Does headgear treatment in young children affect the maxillary canine eruption path?

Does headgear treatment in young children affect the maxillary canine eruption path? Summary Objective To test whether early headgear (HG) treatment and space conditions in the dental arch affect the eruption pathway of the maxillary canines in young children with mixed dentition. Subjects and methods Data from two randomized controlled trials studying the effects of early HG treatment were pooled, yielding a study sample comprising 99 children (38 girls and 61 boys, mean age 7.6 years) with Angle Class II occlusion. Fifty-one children were treated with HG and 48 children served as an untreated control group (CG). Digital 3D models and panoramic radiographs were taken before (T0) and after (T1) treatment, and changes in the maxillary canine eruption angle and interdental spaces were measured at T0 and T1. A paired samples t-test was used to assess changes in maxillary canine angulation, and an independent samples t-test was used to evaluate the effect of HG treatment on spacing in the dental arch. Associations between intra-arch space conditions and changes in maxillary canine angulation were estimated with linear regression models. Results The eruption pattern of the permanent canine was significantly more vertical in the HG group than in the CG. The linear regression models showed a statistically significant association among the intercanine distance, crowding in the anterior part of the maxilla, and changes in the maxillary canine eruption angle. The maxillary canine eruption pattern changed significantly more to a vertical direction in spaced dental arches than in crowded dental arches in the HG group. Conclusion This study shows that early HG treatment in children with Angle Class II occlusion may change the eruption pattern of permanent maxillary canines to a more vertical direction. This change appears to be related to space conditions in the maxillary arch, especially in the intercanine region, with more effect in children with spaced dental arches than in children with crowded dental arches. Introduction During orthodontic treatment, it is common to move the maxillary permanent first molars distally by means of extraoral headgear (HG). This treatment modality has been used in orthodontics since the early 1900s (1), and 62 per cent of orthodontists in Canada and the USA still view HG as a viable treatment method (2, 3). The purpose of this treatment is usually to correct a Class II sagittal molar relationship and a large overjet, to provide space for maxillary teeth, or to provide anchorage for tooth movement, and most previous studies have concentrated on these effects (4–8). However, a few studies have shown that HG treatment may also have an effect on the eruption pattern of the maxillary canines, and therefore could be used as an interceptive treatment modality in cases with ectopic maxillary canine eruption. Armi et al. (9) found that the use of a cervical pull HG significantly improved the eruption rate of palatally displaced canines compared with an untreated control group (CG). Baccetti et al. (10) studied the outcome of HG treatment together with extraction of primary canines on the eruption of palatally displaced canines, and compared the results with extraction of the primary canines only. This study showed that the addition of HG treatment to the extraction of primary canines significantly improved the successful eruption of the displaced canines (10). Silvola et al. (11) investigated the effects of early HG treatment in seven-year-old children with a Class II tendency and moderate crowding on panoramic radiographs. They concluded that the eruption pattern of the maxillary permanent canines was more vertical after 2 years of HG use than in a CG. These studies (9–11) indicate that HG treatment may influence the eruption pattern of maxillary canine teeth. However, the number of studies in this field is limited, and the research quality and methodological standards in a number of these studies have been criticized (12). The aim of the present study was to investigate whether HG treatment in young children affects the maxillary canine eruption path. Also, we wanted to study whether the potential effect of HG treatment on the eruption pattern of maxillary canines is related to space conditions in the dental arch. Subjects and methods The present data were adopted and pooled from two randomized clinical trials (RCTs) studying the outcomes of early HG treatment (Figure 1). The first RCT (4, 11) consisted of 71 seven-year-old children (mean age 7.2 years, SD 0.6 years). The inclusion criteria were Class II occlusion or tendency to Class II occlusion (cusp to cusp). Children with known syndromes and a cleft lip and palate diagnosis were excluded. The second RCT was analogous in design to the first RCT and included 67 seven-year-old children (mean age 7.6 years, SD 0.3 years). Figure 1. View largeDownload slide Patient flow chart. Figure 1. View largeDownload slide Patient flow chart. In both RCTs, the children were randomly divided into two groups of equal size: the HG treatment group (HGG) and the CG. HG treatment started immediately after records were taken (T0) and lasted for at least 1 year or until full angle Class I occlusion was achieved on both sides (T1). In the treatment group, no other appliances were used during the follow-up period. The long outer bows of the HG were bent 10 degrees upwards in relation to the inner bow, which was expanded 5–10 mm compared with the maxillary first molars. The mean force on the HG was 400–700 g, and the patients were instructed to use the HG for 8–10 h per night. No records of HG compliance were taken. Records collected from both groups (HGG and CG) at T0 and T1 included comprehensive clinical examination, dental casts, and panoramic radiographs. Thirty-nine individuals were excluded from the pooled sample for the following reasons: (a) interceptive extraction of primary teeth: 17 subjects, (b) missing images: 15 subjects, (c) bad image quality: 2 subjects, (d) full eruption of maxillary canines at T1: 2 subjects, (e) agenesis of lateral incisors: 2 subjects, and (f) transposition (canines and first premolars): 1 subject. The final study sample therefore consisted of 99 subjects: 51 subjects in the treatment group (HGG) and 48 subjects in the CG. The HGG comprised 39 per cent females and 61 per cent males, and the corresponding numbers for the CG were 38 per cent females and 62 per cent males. The mean age in the pooled sample at T0 was 7.7 years (SD 0.4 years) in the HGG and 7.5 years (SD 0.4 years) in the CG. The mean treatment time with the HG was 23.8 months, SD 5.6 months. Interceptive slicing of the mesial surface of the primary canines was performed in two children in the HGG and three children in the CG. These cases were not excluded. No further interceptive treatment was done in either group. Parental informed consent was obtained before the randomization. The study protocol was approved before the start of the second series of the study by the Ethics Committee of the Oulu University Hospital, Finland (EETTMK: 46/2003). The trial is registered at ClinicalTrials.gov, number NCT02010346. Digital model measurements Dental casts were digitized and analyzed using OrthoAnalyzerTM computer software (3Shape, Copenhagen, Denmark). Digital model measurements (Figure 2) were performed along a constructed occlusal plane, using the mesiobuccal cusp tips of the maxillary right and left first molars and the incisal edges of the right or left central incisor. In those cases with a deviating incisor position, the incisor considered to be in the ‘correct’ position was used. Dental arch distances were measured between the most buccal aspects of the contact points. For trans-palatal measurements, distances were measured between cusp tips. Figure 2. View largeDownload slide Digital model analysis. (A) arch perimeter, (B) premolar space, (C) incisor space, (D) premolar and canine space, (E) intercanine distance, and (F) intermolar distance. Figure 2. View largeDownload slide Digital model analysis. (A) arch perimeter, (B) premolar space, (C) incisor space, (D) premolar and canine space, (E) intercanine distance, and (F) intermolar distance. The following distances were measured (Figure 2): 1. ‘Arch perimeter’—formed by a curve from the distal contact points of teeth #16 and #26 through the contact points and incisal edges of the incisors 2. ‘Premolar space’—from the mesial contact points of the first molar to the distal contact points of the primary canine in the maxilla (measured on both right and left sides) 3. ‘Incisor space’—between the mesial contact points of the right and left maxillary primary canines 4. ‘Premolar and canine space’—from the mesial contact point of the first molar to the distal contact point of the lateral incisor in the maxilla (measured on both the right and left sides) 5. ‘Intercanine distance’—transversally between the left and right maxillary primary canine cusp tips 6. ‘Intermolar distance’—transversally between the left and right maxillary first molar mesiobuccal cusp tips. In addition, the mesiodistal width of each upper and lower incisor was measured. Space analysis Space discrepancy in the maxillary arch was estimated as follows: ‘estimated arch length/tooth size discrepancy’ = the sum of the measured space for the incisors and premolars at T0 minus the sum of the estimated widths of the upper permanent incisors and premolars. The width of the permanent canine and premolars was estimated using Moyers mixed dentition analysis (13) using the lower incisor width: ‘estimated anterior arch length/tooth size discrepancy’ = the sum of the measured space for the incisors at T0 minus the mesiodistal width of the maxillary permanent incisors. Panoramic radiograph measurements The panoramic radiographs and patient positioning were done according to the manufacturer’s protocol. The panoramic images were imported into the Facad® tracing programme (Ilexis, Linkoping, Sweden) and analyzed in a dark room using a Lenovo ThinkPad® (Lenovo, Morrisville, North Carolina, USA) with a 15.6-inch screen with 1,366 × 768 resolution. The following angles were measured (Figure 3): Figure 3. View largeDownload slide Angular measurements of maxillary canines. Angle A: canine to bicondylar line, Angle B: canine to lateral incisor, Angle C: canine to maxillary midline. Figure 3. View largeDownload slide Angular measurements of maxillary canines. Angle A: canine to bicondylar line, Angle B: canine to lateral incisor, Angle C: canine to maxillary midline. – Angle A: the long axis of the maxillary canine to a line drawn between the superior edges of the condyles (14) – Angle B: the long axis of the maxillary canine to the long axis of the maxillary lateral incisor (15) – Angle C: the long axis of the maxillary canine to the maxillary midline formed by a line drawn though the intermaxillary suture (16) – Sector location for canines according to Lindauer et al. (17). All measurements were done for both right and left canines by one investigator (SHO). Reliability of measurements Thirty panoramic radiographs and 20 digital models were measured and scored twice with a timespan of 2 weeks by one investigator (SHO). Intraclass correlation (ICC) was calculated for continuous variables and kappa statistics for categorical variables. The reliability analysis for the measurements of panoramic radiographs showed ‘acceptable’ agreement for the measurement ‘canine to the maxillary midline’ (ICC = 0.745), and ‘excellent’, and ‘almost perfect’ agreement for all the other variables (ICC = 0.905–0.984, kappa = 0.92–1.00). For the 3D model analysis, the reliability for all the variables was rated as ‘excellent’ (ICC: 0.904–0.997). Statistical methods Statistical analysis was performed using version 24.0 of the SPSS software package (SPSS Inc, Chicago, Illinois, USA). An independent sample t-test was used to evaluate the difference between the HGG and the CG on distances (Figure 2) measured on digital models. A paired sample t-test was used to analyze the mean changes between T0 and T1 in maxillary canine angulation (Angles A, B, and C) within the HGG and the CG. Marginal homogenity test was used to analyze changes between T0 and T1 in sector location for canines. Changes in canine eruption angle (Angle A, T1–T0) in crowed compared to spaced dental arches was analyzed with an independent samples t-test. Crude linear regression models were used to evaluate the relationships between the digital model measurements (independent variables; Figure 2) and a change in the maxillary canine angulation (dependent variable; Angle A, T1–T0). To search for the best predictor of the change in Angle A, the statistically significant variables from this calculation and HGG/CG were then entered into a stepwise regression model, and variables were excluded one by one on the grounds of the P-value or the effect of beta. Scatter plots and regression lines were used to analyze and demonstrate the correlation between the change in Angle A (T1–T0) and the incisor space at T0. The differences between the regressions slopes were calculated using analysis of covariance. P-values of less than 0.05 were considered to be statistically significant. Results At T0, the estimated tooth size/arch length discrepancy for the whole study sample was normally distributed, with a mean value of −0.4 mm (min −7.7 mm, max 12.9 mm). The distribution of crowding and spacing in the study sample is shown in Figure 4. There were no statistically significant differences in arch length/tooth size discrepancy between the HGG and the CG (P = 0.29). Figure 4. View largeDownload slide Distribution of tooth size/arch length discrepancy in the study sample. Figure 4. View largeDownload slide Distribution of tooth size/arch length discrepancy in the study sample. From T0 until T1, there was an increase in distance for most dental arch parameters in both the HGG and the CG, but with a larger increase in the HGG. Especially for the arch perimeter, the intermolar and intercanine distances increased to a greater statistically significant degree in the HGG than in the CG (Table 1). Table 1. Maxillary dental arch space changes, T1–T0. HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001, tz/ald = tooth size/arch length discrepancy, measurements in mm. 1Mean difference between HGG and CG groups evaluated with independent samples t-test. View Large Table 1. Maxillary dental arch space changes, T1–T0. HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001, tz/ald = tooth size/arch length discrepancy, measurements in mm. 1Mean difference between HGG and CG groups evaluated with independent samples t-test. View Large The angular measurements of the maxillary permanent canines from T0 and T1 (Table 2) showed that the mean changes for Angle A and Angle C in the HGG were larger (i.e. a more vertical eruption pattern for the maxillary canine) than in the CG. The changes in the HGG were statistically significant on the left side of the maxilla (P = 0.012) and almost significant on the right side (P = 0.051). The changes in canine Angle A and Angle C were not statistically significant in the CG. For Angle B, the mean changes were larger (i.e. a larger angle between the canine and the lateral incisor) in the CG than in the HGG, and the changes in the CG were statistically significant, in contrast to the HGG. Sector location for canines showed significant distal movement (i.e. into lower-numbered sectors) of the canines from T0 to T1 in both the HGG and the CG (Table 2). Table 2. Differences in maxillary canine angulation measured from panoramic radiographs (T1–T0) Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001. 1Mean difference for Angles A, B, and C in degrees, 2Paired samples t-test, 3Marginal Homogenity test. View Large Table 2. Differences in maxillary canine angulation measured from panoramic radiographs (T1–T0) Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001. 1Mean difference for Angles A, B, and C in degrees, 2Paired samples t-test, 3Marginal Homogenity test. View Large The maxillary canine angulation changed significantly more within the HGG in spaced arches than in crowded arches for both the left side (P = 0.020) and the right side (P = 0.031). There was also a statistically significant difference between the HGG and the CG in the spaced arches (P = 0.025) on the left side (i.e. a more vertical eruption pattern in spaced dental arches than in crowded dental arches)—see Figure 5. In the crowded dental arches, there was no difference between the HGG and the CG in canine angulation. Figure 5. View largeDownload slide Effect of headgear treatment on change in canine eruption angle (Angle A) in crowed and spaced dental arches. Figure 5. View largeDownload slide Effect of headgear treatment on change in canine eruption angle (Angle A) in crowed and spaced dental arches. In the regression analysis, a statistically significant relationship was found among ‘incisor space’, ‘intercanine distance’, ‘estimated anterior tooth size/arch length discrepancy’, and change in canine angulation (‘Angle A, T1–T0’). In the CG, a statistically significant relationship was seen on the left side of the maxilla among ‘arch perimeter’, ‘incisor space’, ‘intercanine distance’, and change in canine angulation (‘Angle A’, T1–T0)—see Table 3. Table 3. Regression analysis showing the relationship between digital model space analysis (T0) and “Angle A”, T1-T0. Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 1Linear regression, *p < 0.05, **p < 0.01, tz/ald = tooth size/arch length discrepancy View Large Table 3. Regression analysis showing the relationship between digital model space analysis (T0) and “Angle A”, T1-T0. Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 1Linear regression, *p < 0.05, **p < 0.01, tz/ald = tooth size/arch length discrepancy View Large A stepwise regression model of the statistically significant variables showed that the best predictor for change in canine angulation (‘Angle A, T1–T0’) was ‘incisor space’ at T0. In Figure 6, this association is shown by means of scatter plots and regression curves. The curves show generally a larger increase in Angle A (hence a more vertical eruption pattern for the maxillary canine) in the HGG than in the CG. The difference between the regression slopes in the HGG and those in the CG was statistically significant on the left side (P = 0.043). Figure 6. View largeDownload slide Relationship between ‘incisor distance’ and ‘Angle A’ on the right and left side of the maxilla. Linear regression. Figure 6. View largeDownload slide Relationship between ‘incisor distance’ and ‘Angle A’ on the right and left side of the maxilla. Linear regression. Discussion One of the most interesting findings in this study was that HG treatment appears to influence the eruption pattern of the maxillary canines, especially in patients with space excess in the dental arch. Previous studies have shown that the maxillary canines are affected by HG treatment (9–11), but the importance of the space discrepancy and the size of the dental arch are unclear. The reason for the maxillary canine erupting more vertically in the HGG is unclear. It may be related to more space being created distally to the canine, since HG treatment has the ability to expand the dental arch and distalize first molars (18). Trans-septal fibers (19) may apply a distal force on the posterior dentition increasing space for the erupting maxillary canine. Increased space created transversally in the dental arch may be another reason for the changed canine angulation. According to previous studies, increased intercanine space created with fixed appliances (20) or rapid maxillary expanders (21) has increased the eruption rate of ectopic maxillary canines. Also, maxillary incisors with signs of eruption disorders appear to improve their vertical and angular position after the use of rapid maxillary expanders (22). The reason for HG treatment seeming to have a greater effect on the canine angulation in spaced arches cannot be explained yet. Our study showed that the expanding effect of HG treatment on the maxilla was actually significantly larger (P < 0.05) in narrow arches than in broad dental arches, so less expansion in the crowded cases cannot explain the finding. It is more likely that the maxillary canines are more restricted to move in crowded cases owing to space deficiency than in spaced arches, even though the arches were more expanded in crowded cases than in spaced cases. Another very interesting finding from the stepwise regression analysis was that space conditions in the anterior part of the maxilla appear to be the most important factor in how much the maxillary canine erupts vertically. The intercanine distance and especially the incisor space at T0 correlated significantly with a change in canine angulation (Angle A, T1–T0). In our study, we found a significantly larger increase in intercanine distance in the HGG than in the CG. This increase is consistent with previous studies (5, 6) in which an expanded inner HG bow was used. This effect may be due not only to the force applied, but also to the inner HG bow relieving the pressure of the lip musculature, and thereby creating a ‘lip bumper effect’. The clinical relevance of more vertical and distal movement of the maxillary canines observed in the HG group compared to the CG could have several implications. In patients with crowding in the anterior part of the maxilla, more vertical or distal movement of the canines than normal will relieve crowding and is therefore beneficial. In angle Class II patients, distal movement of the maxillary dentition is usually wanted and the HG-effect seen in this study may therefore be positive. In cases with lateral incisor root resorptions or risk for root resorptions triggered by maxillary canines, distal movement of the maxillary canines away from the lateral is required. At times, fixed appliances are contraindicated and therefore the distal movement of the maxillary canine by a simple appliance like a HG could be advantageous. During normal tooth eruption, children in the 7–8-year age range are often experience the ‘ugly duckling stage’ (23). In this period, the maxillary canine crown pushes onto the lateral incisor roots, causing them to flare and leading to an increase in Angle B. In the present study, we saw an increase in Angle B in the CG but no change in Angle B in the HGG. The reason for our seeing no change in the HGG is probably that the maxillary canines moved away distally from the lateral incisor when an HG is used. The fact that Angle B did not change in the HGG may also be because the upper incisors tend to move labially when using a HG, which has been shown earlier (5). Labial tilting of the incisors may change the lateral incisors’ position relative to the canines, as well as increase the interdental spaces. Together, these two effects may reduce the flaring of the lateral incisors. Patients in this study started HG treatment around 7.5 years of age. At this age, it is too early to detect palatal or buccal displacement of the canines (24). It is therefore not possible to conclude whether early HG treatment has an effect on ectopically erupting canines. Also, it is important to note that patients with other malocclusions may respond differently than the angle Class II sample selected. For this study, data from two previous RCTs were pooled. When pooling data from different studies, the combined results may contradict the results of the individual studies. This effect, also known as ‘Simpson’s paradox’, may arise when important subgroup characteristics in the different studies are not considered or weighted (25). In the present study, weighting of the subgroups was not performed, since the two RCTs were similar in design in five ways: (1) the RCTs were conducted in the same region in Finland, (2) they were carried out by the same research team, (3) the research team used the same treatment technique in both studies, (4) the age and gender of the participants were similar for both studies, and (5) the angle classifications were similar. Seventeen children were excluded from the study because their primary canines had been extracted owing to space discrepancy or ectopic positioning of the maxillary canine. Primary canine extraction may influence both the eruption path and the rate of maxillary canines, as well as reduce the dental arch length (10, 26–28), and thereby create bias. Two children in the HGG and three children in the CG had the mesial surface of their primary maxillary canines slightly sliced in order to facilitate the alignment of their maxillary lateral incisors. It is possible that this procedure might reduce the intercanine width, but it is doubtful that it would affect the maxillary canine eruption pattern, and so we decided not to exclude these patients. The reliability measurements were ‘excellent’ and ‘almost perfect’ for all measurements except the angular measurement of the maxillary canine relative to the maxillary midline (Angle C). The reliability of this measurement was rated as ‘acceptable’ in this study (ICC = 0.745), and some caution should therefore be taken when interpreting this variable. The lowered reliability of Angle C may be related to difficulty in assessing the maxillary midline in some panoramic radiographs, as blurring of panoramic images may happen in the maxillary midline owing to incorrect patient positioning in the X-ray machine (29). Overall, the most reliable variable was ‘Angle A’, and it was therefore chosen as the dependent variable in the linear regression analysis. HG compliance was not evaluated in the two studies involved. However, full Class I occlusion at the endpoint and a larger increase in most dental arch parameters in the HGG indicated a proper use of the HG. Estimation of crowding and spacing in mixed dentition is a challenge, since the precise size of the permanent teeth is not possible to measure. In our estimation of tooth size/arch length discrepancy, we used the well-known Moyers mixed dentition analysis (13) to assess the size of the permanent maxillary canines and premolars. The Moyers method may have population variations, and it is suggested that it may be necessary to develop prediction tables for specific populations (30). Certain caution should therefore be taken with regard to our calculations of tooth size/arch length discrepancy. A follow-up study to investigate the final differences in canine position between the HG and CG would be desirable. Conclusion This study showed that early HG treatment in children with angle Class II occlusion may change the eruption pattern of maxillary canines to a more vertical direction. The change in the eruption pathway seems to be related to space conditions in the maxillary arch, especially in the intercanine region, with the most significant effect in the HG group with spaced dental arches compared to crowded dental arches. Conflict of Interest None to declare. References 1. Pavlick , C.T. Jr . ( 1998 ) Cervical headgear usage and the bioprogressive orthodontic philosophy . Seminars in Orthodontics , 4 , 219 – 230 . Google Scholar CrossRef Search ADS PubMed 2. Tüfekçi , E. , Allen , S.B. , Best , A.M. and Lindauer , S.J . ( 2016 ) Current trends in headgear use for the treatment of class II malocclusions . The Angle Orthodontist , 86 , 584 – 589 . Google Scholar CrossRef Search ADS PubMed 3. Keim , R.G . ( 2009 ) The state of the profession . Journal of Clinical Orthodontics , 43 , 9 – 10 . Google Scholar PubMed 4. Pirttiniemi , P. , Kantomaa , T. , Mäntysaari , R. , Pykäläinen , A. , Krusinskiene , V. , Laitala , T. and Karikko , J . ( 2005 ) The effects of early headgear treatment on dental arches and craniofacial morphology: an 8 year report of a randomized study . European Journal of Orthodontics , 27 , 429 – 436 . Google Scholar CrossRef Search ADS PubMed 5. Mäntysaari , R. , Kantomaa , T. , Pirttiniemi , P. and Pykäläinen , A . ( 2004 ) The effects of early headgear treatment on dental arches and craniofacial morphology: a report of a 2 year randomized study . European Journal of Orthodontics , 26 , 59 – 64 . Google Scholar CrossRef Search ADS PubMed 6. Varlik , S.K. and Iscan , H.N . ( 2008 ) The effects of cervical headgear with an expanded inner bow in the permanent dentition . European Journal of Orthodontics , 30 , 425 – 430 . Google Scholar CrossRef Search ADS PubMed 7. de Oliveira , J.N. Jr , Rodrigues de Almeida , R. , Rodrigues de Almeida , M. and de Oliveira , J.N . ( 2007 ) Dentoskeletal changes induced by the Jasper jumper and cervical headgear appliances followed by fixed orthodontic treatment . American Journal of Orthodontics and Dentofacial Orthopedics , 132 , 54 – 62 . Google Scholar CrossRef Search ADS PubMed 8. Lima Filho , R.M. , Lima , A.L. and de Oliveira Ruellas , A.C . ( 2003 ) Mandibular changes in skeletal class II patients treated with Kloehn cervical headgear . American Journal of Orthodontics and Dentofacial Orthopedics , 124 , 83 – 90 . Google Scholar CrossRef Search ADS PubMed 9. Armi , P. , Cozza , P. and Baccetti , T . ( 2011 ) Effect of RME and headgear treatment on the eruption of palatally displaced canines: a randomized clinical study . The Angle Orthodontist , 81 , 370 – 374 . Google Scholar CrossRef Search ADS PubMed 10. Baccetti , T. , Leonardi , M. and Armi , P . ( 2008 ) A randomized clinical study of two interceptive approaches to palatally displaced canines . European Journal of Orthodontics , 30 , 381 – 385 . Google Scholar CrossRef Search ADS PubMed 11. Silvola , A.S. , Arvonen , P. , Julku , J. , Lähdesmäki , R. , Kantomaa , T. and Pirttiniemi , P . ( 2009 ) Early headgear effects on the eruption pattern of the maxillary canines . The Angle Orthodontist , 79 , 540 – 545 . Google Scholar CrossRef Search ADS PubMed 12. Naoumova , J. , Kurol , J. and Kjellberg , H . ( 2011 ) A systematic review of the interceptive treatment of palatally displaced maxillary canines . European Journal of Orthodontics , 33 , 143 – 149 . Google Scholar CrossRef Search ADS PubMed 13. Moyers , R.E . ( 1988 ) Handbook of Orthodontics . Year Book Medical Publishers , Chicago, IL , 3rd edn , pp. 369 – 379 . 14. Warford , J.H. Jr , Grandhi , R.K. and Tira , D.E . ( 2003 ) Prediction of maxillary canine impaction using sectors and angular measurement . American Journal of Orthodontics and Dentofacial Orthopedics , 124 , 651 – 655 . Google Scholar CrossRef Search ADS PubMed 15. Ericson , S. and Kurol , J . ( 1988 ) Resorption of maxillary lateral incisors caused by ectopic eruption of the canines. A clinical and radiographic analysis of predisposing factors . American Journal of Orthodontics and Dentofacial Orthopedics , 94 , 503 – 513 . Google Scholar CrossRef Search ADS PubMed 16. Bjerklin , K. and Ericson , S . ( 2006 ) How a computerized tomography examination changed the treatment plans of 80 children with retained and ectopically positioned maxillary canines . The Angle Orthodontist , 76 , 43 – 51 . Google Scholar PubMed 17. Lindauer , S.J , Rubenstein , L.K , Hang , W.M , Andersen , W.C , Isaacson , R.J . ( 1992 ) Canine impaction identified early with panoramic radiographs . Journal of the American Dental Association , 123 , 91 – 92 . Google Scholar CrossRef Search ADS PubMed 18. Henriques , F.P. , Janson , G. , Henriques , J.F. and Pupulim , D.C . ( 2015 ) Effects of cervical headgear appliance: a systematic review . Dental Press Journal of Orthodontics , 20 , 76 – 81 . Google Scholar CrossRef Search ADS PubMed 19. Itoiz , M.C . ( 2002 ) Carranza’s Clinical Periodontology . W.B. Saunders Company , Philadelphia, PA, 9th edn , pp. 26 – 27 . 20. Olive , R.J . ( 2002 ) Orthodontic treatment of palatally impacted maxillary canines . Australian Orthodontic Journal , 18 , 64 – 70 . Google Scholar PubMed 21. Sigler , L.M. , Baccetti , T. and McNamara , J.A. Jr . ( 2011 ) Effect of rapid maxillary expansion and transpalatal arch treatment associated with deciduous canine extraction on the eruption of palatally displaced canines: a 2-center prospective study . American Journal of Orthodontics and Dentofacial Orthopedics , 139 , e235 – e244 . Google Scholar CrossRef Search ADS PubMed 22. Pavoni , C. , Franchi , L. , Laganà , G. and Cozza , P . ( 2013 ) Radiographic assessment of maxillary incisor position after rapid maxillary expansion in children with clinical signs of eruption disorder . Journal of Orofacial Orthopedics , 74 , 468 – 479 . Google Scholar CrossRef Search ADS PubMed 23. Broadbent , B.H . ( 1941 ) Ontogenic development of occlusion . The Angle Orthodontist , 11 , 223 – 241 . 24. Mitchell , L . ( 2013 ) Assessing Maxillary Canine Position . Oxford University Press , UK , 4th edn , pp. 172 – 173 . 25. Bravata , D.M. and Olkin , I . ( 2001 ) Simple pooling versus combining in meta-analysis . Evaluation & the Health Professions , 24 , 218 – 230 . Google Scholar CrossRef Search ADS PubMed 26. Power , S.M. and Short , M.B . ( 1993 ) An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption . British Journal of Orthodontics , 20 , 215 – 223 . Google Scholar CrossRef Search ADS PubMed 27. Ericson , S. and Kurol , J . ( 1988 ) Early treatment of palatally erupting maxillary canines by extraction of the primary canines . European Journal of Orthodontics , 10 , 283 – 295 . Google Scholar CrossRef Search ADS PubMed 28. Sjögren , A. , Arnrup , K. , Lennartsson , B. and Huggare , J . ( 2012 ) Mandibular incisor alignment and dental arch changes 1 year after extraction of deciduous canines . European Journal of Orthodontics , 34 , 587 – 594 . Google Scholar CrossRef Search ADS PubMed 29. Molander , B. , Ahlqwist , M. and Gröndahl , H.G . ( 1995 ) Image quality in panoramic radiography . Dento Maxillo Facial Radiology , 24 , 17 – 22 . Google Scholar CrossRef Search ADS PubMed 30. Galvão , M. , Dominguez , G.C. , Tormin , S.T. , Akamine , A. , Tortamano , A. and de Fantini , S.M . ( 2013 ) Applicability of Moyers analysis in mixed dentition: a systematic review . Dental Press Journal of Orthodontics , 18 , 100 – 105 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The European Journal of Orthodontics Oxford University Press

Does headgear treatment in young children affect the maxillary canine eruption path?

Loading next page...
 
/lp/ou_press/does-headgear-treatment-in-young-children-affect-the-maxillary-canine-0oNYfl1St8
Publisher
Oxford University Press
Copyright
© The Author(s) 2018. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com
ISSN
0141-5387
eISSN
1460-2210
D.O.I.
10.1093/ejo/cjy013
Publisher site
See Article on Publisher Site

Abstract

Summary Objective To test whether early headgear (HG) treatment and space conditions in the dental arch affect the eruption pathway of the maxillary canines in young children with mixed dentition. Subjects and methods Data from two randomized controlled trials studying the effects of early HG treatment were pooled, yielding a study sample comprising 99 children (38 girls and 61 boys, mean age 7.6 years) with Angle Class II occlusion. Fifty-one children were treated with HG and 48 children served as an untreated control group (CG). Digital 3D models and panoramic radiographs were taken before (T0) and after (T1) treatment, and changes in the maxillary canine eruption angle and interdental spaces were measured at T0 and T1. A paired samples t-test was used to assess changes in maxillary canine angulation, and an independent samples t-test was used to evaluate the effect of HG treatment on spacing in the dental arch. Associations between intra-arch space conditions and changes in maxillary canine angulation were estimated with linear regression models. Results The eruption pattern of the permanent canine was significantly more vertical in the HG group than in the CG. The linear regression models showed a statistically significant association among the intercanine distance, crowding in the anterior part of the maxilla, and changes in the maxillary canine eruption angle. The maxillary canine eruption pattern changed significantly more to a vertical direction in spaced dental arches than in crowded dental arches in the HG group. Conclusion This study shows that early HG treatment in children with Angle Class II occlusion may change the eruption pattern of permanent maxillary canines to a more vertical direction. This change appears to be related to space conditions in the maxillary arch, especially in the intercanine region, with more effect in children with spaced dental arches than in children with crowded dental arches. Introduction During orthodontic treatment, it is common to move the maxillary permanent first molars distally by means of extraoral headgear (HG). This treatment modality has been used in orthodontics since the early 1900s (1), and 62 per cent of orthodontists in Canada and the USA still view HG as a viable treatment method (2, 3). The purpose of this treatment is usually to correct a Class II sagittal molar relationship and a large overjet, to provide space for maxillary teeth, or to provide anchorage for tooth movement, and most previous studies have concentrated on these effects (4–8). However, a few studies have shown that HG treatment may also have an effect on the eruption pattern of the maxillary canines, and therefore could be used as an interceptive treatment modality in cases with ectopic maxillary canine eruption. Armi et al. (9) found that the use of a cervical pull HG significantly improved the eruption rate of palatally displaced canines compared with an untreated control group (CG). Baccetti et al. (10) studied the outcome of HG treatment together with extraction of primary canines on the eruption of palatally displaced canines, and compared the results with extraction of the primary canines only. This study showed that the addition of HG treatment to the extraction of primary canines significantly improved the successful eruption of the displaced canines (10). Silvola et al. (11) investigated the effects of early HG treatment in seven-year-old children with a Class II tendency and moderate crowding on panoramic radiographs. They concluded that the eruption pattern of the maxillary permanent canines was more vertical after 2 years of HG use than in a CG. These studies (9–11) indicate that HG treatment may influence the eruption pattern of maxillary canine teeth. However, the number of studies in this field is limited, and the research quality and methodological standards in a number of these studies have been criticized (12). The aim of the present study was to investigate whether HG treatment in young children affects the maxillary canine eruption path. Also, we wanted to study whether the potential effect of HG treatment on the eruption pattern of maxillary canines is related to space conditions in the dental arch. Subjects and methods The present data were adopted and pooled from two randomized clinical trials (RCTs) studying the outcomes of early HG treatment (Figure 1). The first RCT (4, 11) consisted of 71 seven-year-old children (mean age 7.2 years, SD 0.6 years). The inclusion criteria were Class II occlusion or tendency to Class II occlusion (cusp to cusp). Children with known syndromes and a cleft lip and palate diagnosis were excluded. The second RCT was analogous in design to the first RCT and included 67 seven-year-old children (mean age 7.6 years, SD 0.3 years). Figure 1. View largeDownload slide Patient flow chart. Figure 1. View largeDownload slide Patient flow chart. In both RCTs, the children were randomly divided into two groups of equal size: the HG treatment group (HGG) and the CG. HG treatment started immediately after records were taken (T0) and lasted for at least 1 year or until full angle Class I occlusion was achieved on both sides (T1). In the treatment group, no other appliances were used during the follow-up period. The long outer bows of the HG were bent 10 degrees upwards in relation to the inner bow, which was expanded 5–10 mm compared with the maxillary first molars. The mean force on the HG was 400–700 g, and the patients were instructed to use the HG for 8–10 h per night. No records of HG compliance were taken. Records collected from both groups (HGG and CG) at T0 and T1 included comprehensive clinical examination, dental casts, and panoramic radiographs. Thirty-nine individuals were excluded from the pooled sample for the following reasons: (a) interceptive extraction of primary teeth: 17 subjects, (b) missing images: 15 subjects, (c) bad image quality: 2 subjects, (d) full eruption of maxillary canines at T1: 2 subjects, (e) agenesis of lateral incisors: 2 subjects, and (f) transposition (canines and first premolars): 1 subject. The final study sample therefore consisted of 99 subjects: 51 subjects in the treatment group (HGG) and 48 subjects in the CG. The HGG comprised 39 per cent females and 61 per cent males, and the corresponding numbers for the CG were 38 per cent females and 62 per cent males. The mean age in the pooled sample at T0 was 7.7 years (SD 0.4 years) in the HGG and 7.5 years (SD 0.4 years) in the CG. The mean treatment time with the HG was 23.8 months, SD 5.6 months. Interceptive slicing of the mesial surface of the primary canines was performed in two children in the HGG and three children in the CG. These cases were not excluded. No further interceptive treatment was done in either group. Parental informed consent was obtained before the randomization. The study protocol was approved before the start of the second series of the study by the Ethics Committee of the Oulu University Hospital, Finland (EETTMK: 46/2003). The trial is registered at ClinicalTrials.gov, number NCT02010346. Digital model measurements Dental casts were digitized and analyzed using OrthoAnalyzerTM computer software (3Shape, Copenhagen, Denmark). Digital model measurements (Figure 2) were performed along a constructed occlusal plane, using the mesiobuccal cusp tips of the maxillary right and left first molars and the incisal edges of the right or left central incisor. In those cases with a deviating incisor position, the incisor considered to be in the ‘correct’ position was used. Dental arch distances were measured between the most buccal aspects of the contact points. For trans-palatal measurements, distances were measured between cusp tips. Figure 2. View largeDownload slide Digital model analysis. (A) arch perimeter, (B) premolar space, (C) incisor space, (D) premolar and canine space, (E) intercanine distance, and (F) intermolar distance. Figure 2. View largeDownload slide Digital model analysis. (A) arch perimeter, (B) premolar space, (C) incisor space, (D) premolar and canine space, (E) intercanine distance, and (F) intermolar distance. The following distances were measured (Figure 2): 1. ‘Arch perimeter’—formed by a curve from the distal contact points of teeth #16 and #26 through the contact points and incisal edges of the incisors 2. ‘Premolar space’—from the mesial contact points of the first molar to the distal contact points of the primary canine in the maxilla (measured on both right and left sides) 3. ‘Incisor space’—between the mesial contact points of the right and left maxillary primary canines 4. ‘Premolar and canine space’—from the mesial contact point of the first molar to the distal contact point of the lateral incisor in the maxilla (measured on both the right and left sides) 5. ‘Intercanine distance’—transversally between the left and right maxillary primary canine cusp tips 6. ‘Intermolar distance’—transversally between the left and right maxillary first molar mesiobuccal cusp tips. In addition, the mesiodistal width of each upper and lower incisor was measured. Space analysis Space discrepancy in the maxillary arch was estimated as follows: ‘estimated arch length/tooth size discrepancy’ = the sum of the measured space for the incisors and premolars at T0 minus the sum of the estimated widths of the upper permanent incisors and premolars. The width of the permanent canine and premolars was estimated using Moyers mixed dentition analysis (13) using the lower incisor width: ‘estimated anterior arch length/tooth size discrepancy’ = the sum of the measured space for the incisors at T0 minus the mesiodistal width of the maxillary permanent incisors. Panoramic radiograph measurements The panoramic radiographs and patient positioning were done according to the manufacturer’s protocol. The panoramic images were imported into the Facad® tracing programme (Ilexis, Linkoping, Sweden) and analyzed in a dark room using a Lenovo ThinkPad® (Lenovo, Morrisville, North Carolina, USA) with a 15.6-inch screen with 1,366 × 768 resolution. The following angles were measured (Figure 3): Figure 3. View largeDownload slide Angular measurements of maxillary canines. Angle A: canine to bicondylar line, Angle B: canine to lateral incisor, Angle C: canine to maxillary midline. Figure 3. View largeDownload slide Angular measurements of maxillary canines. Angle A: canine to bicondylar line, Angle B: canine to lateral incisor, Angle C: canine to maxillary midline. – Angle A: the long axis of the maxillary canine to a line drawn between the superior edges of the condyles (14) – Angle B: the long axis of the maxillary canine to the long axis of the maxillary lateral incisor (15) – Angle C: the long axis of the maxillary canine to the maxillary midline formed by a line drawn though the intermaxillary suture (16) – Sector location for canines according to Lindauer et al. (17). All measurements were done for both right and left canines by one investigator (SHO). Reliability of measurements Thirty panoramic radiographs and 20 digital models were measured and scored twice with a timespan of 2 weeks by one investigator (SHO). Intraclass correlation (ICC) was calculated for continuous variables and kappa statistics for categorical variables. The reliability analysis for the measurements of panoramic radiographs showed ‘acceptable’ agreement for the measurement ‘canine to the maxillary midline’ (ICC = 0.745), and ‘excellent’, and ‘almost perfect’ agreement for all the other variables (ICC = 0.905–0.984, kappa = 0.92–1.00). For the 3D model analysis, the reliability for all the variables was rated as ‘excellent’ (ICC: 0.904–0.997). Statistical methods Statistical analysis was performed using version 24.0 of the SPSS software package (SPSS Inc, Chicago, Illinois, USA). An independent sample t-test was used to evaluate the difference between the HGG and the CG on distances (Figure 2) measured on digital models. A paired sample t-test was used to analyze the mean changes between T0 and T1 in maxillary canine angulation (Angles A, B, and C) within the HGG and the CG. Marginal homogenity test was used to analyze changes between T0 and T1 in sector location for canines. Changes in canine eruption angle (Angle A, T1–T0) in crowed compared to spaced dental arches was analyzed with an independent samples t-test. Crude linear regression models were used to evaluate the relationships between the digital model measurements (independent variables; Figure 2) and a change in the maxillary canine angulation (dependent variable; Angle A, T1–T0). To search for the best predictor of the change in Angle A, the statistically significant variables from this calculation and HGG/CG were then entered into a stepwise regression model, and variables were excluded one by one on the grounds of the P-value or the effect of beta. Scatter plots and regression lines were used to analyze and demonstrate the correlation between the change in Angle A (T1–T0) and the incisor space at T0. The differences between the regressions slopes were calculated using analysis of covariance. P-values of less than 0.05 were considered to be statistically significant. Results At T0, the estimated tooth size/arch length discrepancy for the whole study sample was normally distributed, with a mean value of −0.4 mm (min −7.7 mm, max 12.9 mm). The distribution of crowding and spacing in the study sample is shown in Figure 4. There were no statistically significant differences in arch length/tooth size discrepancy between the HGG and the CG (P = 0.29). Figure 4. View largeDownload slide Distribution of tooth size/arch length discrepancy in the study sample. Figure 4. View largeDownload slide Distribution of tooth size/arch length discrepancy in the study sample. From T0 until T1, there was an increase in distance for most dental arch parameters in both the HGG and the CG, but with a larger increase in the HGG. Especially for the arch perimeter, the intermolar and intercanine distances increased to a greater statistically significant degree in the HGG than in the CG (Table 1). Table 1. Maxillary dental arch space changes, T1–T0. HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001, tz/ald = tooth size/arch length discrepancy, measurements in mm. 1Mean difference between HGG and CG groups evaluated with independent samples t-test. View Large Table 1. Maxillary dental arch space changes, T1–T0. HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 HGG mean T1–T0 SD CG mean T1–T0 SD Mean difference T1–T01 Sig. (two-tailed) 95% confidence interval of the difference Lower Upper Arch perimeter 5.79 4.32 2.78 4.53 3.01 0.002** 1.13 4.89 Premolar and canine space—right side −0.02 1.69 −0.59 1.71 0.57 0.103 −0.12 1.25 Premolar and canine space—left side 0.12 1.39 −0.65 1.94 0.77 0.027* 0.09 1.45 Intermolar distance 3.81 3.13 1.75 2.59 2.06 <0.001*** 0.87 3.24 Intercanine distance 3.07 1.98 1.27 2.27 1.80 <0.001*** 0.88 2.72 Incisor space 4.80 2.78 3.39 3.79 1.41 0.053 −0.02 2.84 Premolar space—right side −0.18 1.11 −0.20 0.61 0.02 0.907 −0.34 0.39 Premolar space—left side −0.48 1.22 −0.45 1.42 −0.03 0.916 −0.56 0.51 Estimated tz/ald* 5.03 4.14 2.98 4.23 2.05 0.030* 0.21 3.89 Estimated anterior tz/ald* 4.73 2.73 3.24 3.75 1.49 0.041* 0.063 2.91 CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001, tz/ald = tooth size/arch length discrepancy, measurements in mm. 1Mean difference between HGG and CG groups evaluated with independent samples t-test. View Large The angular measurements of the maxillary permanent canines from T0 and T1 (Table 2) showed that the mean changes for Angle A and Angle C in the HGG were larger (i.e. a more vertical eruption pattern for the maxillary canine) than in the CG. The changes in the HGG were statistically significant on the left side of the maxilla (P = 0.012) and almost significant on the right side (P = 0.051). The changes in canine Angle A and Angle C were not statistically significant in the CG. For Angle B, the mean changes were larger (i.e. a larger angle between the canine and the lateral incisor) in the CG than in the HGG, and the changes in the CG were statistically significant, in contrast to the HGG. Sector location for canines showed significant distal movement (i.e. into lower-numbered sectors) of the canines from T0 to T1 in both the HGG and the CG (Table 2). Table 2. Differences in maxillary canine angulation measured from panoramic radiographs (T1–T0) Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001. 1Mean difference for Angles A, B, and C in degrees, 2Paired samples t-test, 3Marginal Homogenity test. View Large Table 2. Differences in maxillary canine angulation measured from panoramic radiographs (T1–T0) Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** Side Group Mean diff.1 SD 95% confidence interval of the difference1 Sig. two-tailed2 Lower Upper Angle A Right CG 1.26 8.16 −1.12 3.61 0.295 HGG 2.57 9.19 −0.016 5.15 0.051 Left CG 0.97 6.85 −1.02 2.96 0.332 HGG 3.65 10.02 0.83 6.46 0.012* Angle B Right CG 4.88 10.94 1.70 8.06 0.003** HGG 1.17 12.63 −2.38 4.72 0.511 Left CG 4.55 10.62 1.47 7.64 0.005** HGG −0.43 13.06 −4.10 3.24 0.815 Angle C Right CG −1.32 8.50 −3.79 1.15 0.289 HGG −2.24 9.57 −4.93 0.45 0.101 Left CG −0.65 6.96 −2.68 1.37 0.518 HGG −3.88 9.92 −6.67 −1.09 0.007** Side Group Mean diff. Sector decreased (N) Sector unchanged (N) Sector increased (N) Sig. two-tailed3 Right CG 0.29 18 25 5 0.006** Sector Left HGG 0.37 21 27 3 <0.001*** Right CG 0.19 15 25 8 0.095 Left HGG 0.33 20 28 3 <0.001*** CG: control group; HGG: headgear group. *P < 0.05, **P < 0.01, ***P < 0.001. 1Mean difference for Angles A, B, and C in degrees, 2Paired samples t-test, 3Marginal Homogenity test. View Large The maxillary canine angulation changed significantly more within the HGG in spaced arches than in crowded arches for both the left side (P = 0.020) and the right side (P = 0.031). There was also a statistically significant difference between the HGG and the CG in the spaced arches (P = 0.025) on the left side (i.e. a more vertical eruption pattern in spaced dental arches than in crowded dental arches)—see Figure 5. In the crowded dental arches, there was no difference between the HGG and the CG in canine angulation. Figure 5. View largeDownload slide Effect of headgear treatment on change in canine eruption angle (Angle A) in crowed and spaced dental arches. Figure 5. View largeDownload slide Effect of headgear treatment on change in canine eruption angle (Angle A) in crowed and spaced dental arches. In the regression analysis, a statistically significant relationship was found among ‘incisor space’, ‘intercanine distance’, ‘estimated anterior tooth size/arch length discrepancy’, and change in canine angulation (‘Angle A, T1–T0’). In the CG, a statistically significant relationship was seen on the left side of the maxilla among ‘arch perimeter’, ‘incisor space’, ‘intercanine distance’, and change in canine angulation (‘Angle A’, T1–T0)—see Table 3. Table 3. Regression analysis showing the relationship between digital model space analysis (T0) and “Angle A”, T1-T0. Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 1Linear regression, *p < 0.05, **p < 0.01, tz/ald = tooth size/arch length discrepancy View Large Table 3. Regression analysis showing the relationship between digital model space analysis (T0) and “Angle A”, T1-T0. Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 Headgear Group Control Group Digital model measurements Unstand. Coeff. B1 Sig. (2-tailed)1 95 % Confidence Interval for B1 Unstand. Coeff. B1 Sig. (2-tailed)1 95% Confidence Interval for B1 Upper Lower Upper Lower RIGHT SIDE: Arch perimeter 0.468 0.097 -0.088 1.024 0.670 0.012* 0.159 1.182 Incisor space 1.069 0.001** 0.452 1.686 0.960 0.010* 0.238 1.682 Premolar and canine space -1.306 0.181 -3.240 0.628 0.572 0.531 -1.251 2.394 Premolar space -1.984 0.148 -4.699 0.732 0.577 0.657 -2.019 3.172 Intermolar distance 0.756 0.138 -0.252 1.764 0.701 0.182 -0.340 1.742 Intercanine distance 1.310 0.036* 0.092 2.528 1.304 0.031* 0.128 2.479 Estimated tz/ald* 0.291 0.331 -0.305 0.886 0.510 0.076 -0.056 1.076 Est. anterior tz/ald* 0.970 0.007** 0.281 1.660 0.650 0.070 -0.056 1.356 LEFT SIDE: Arch perimeter 0.464 0.134 -0.149 1.077 0.359 0.119 -0.096 0.815 Incisor space 1.164 0.001** 0.490 1.837 0.510 0.112 -0.124 1.144 Premolar and canine space -0.937 0.308 -2.764 0.890 0.461 0.581 -1.209 2.130 Premolar space -1.490 0.203 -3.812 0.831 1.211 0.312 -1.172 3.594 Intermolar distance 0.845 0.124 -0.242 1.932 0.255 0.573 -0.649 1.159 Intercanine distance 1.457 0.032* 0.132 2.783 0.392 0.449 -0.641 1.424 Estimated tz/ald* 0.540 0.092 -0.091 1.172 0.017 0.943 -0.472 0.507 Est. anterior tz/ald* 1.187 0.002** 0.458 1.915 0.208 0.496 -0.401 0.816 1Linear regression, *p < 0.05, **p < 0.01, tz/ald = tooth size/arch length discrepancy View Large A stepwise regression model of the statistically significant variables showed that the best predictor for change in canine angulation (‘Angle A, T1–T0’) was ‘incisor space’ at T0. In Figure 6, this association is shown by means of scatter plots and regression curves. The curves show generally a larger increase in Angle A (hence a more vertical eruption pattern for the maxillary canine) in the HGG than in the CG. The difference between the regression slopes in the HGG and those in the CG was statistically significant on the left side (P = 0.043). Figure 6. View largeDownload slide Relationship between ‘incisor distance’ and ‘Angle A’ on the right and left side of the maxilla. Linear regression. Figure 6. View largeDownload slide Relationship between ‘incisor distance’ and ‘Angle A’ on the right and left side of the maxilla. Linear regression. Discussion One of the most interesting findings in this study was that HG treatment appears to influence the eruption pattern of the maxillary canines, especially in patients with space excess in the dental arch. Previous studies have shown that the maxillary canines are affected by HG treatment (9–11), but the importance of the space discrepancy and the size of the dental arch are unclear. The reason for the maxillary canine erupting more vertically in the HGG is unclear. It may be related to more space being created distally to the canine, since HG treatment has the ability to expand the dental arch and distalize first molars (18). Trans-septal fibers (19) may apply a distal force on the posterior dentition increasing space for the erupting maxillary canine. Increased space created transversally in the dental arch may be another reason for the changed canine angulation. According to previous studies, increased intercanine space created with fixed appliances (20) or rapid maxillary expanders (21) has increased the eruption rate of ectopic maxillary canines. Also, maxillary incisors with signs of eruption disorders appear to improve their vertical and angular position after the use of rapid maxillary expanders (22). The reason for HG treatment seeming to have a greater effect on the canine angulation in spaced arches cannot be explained yet. Our study showed that the expanding effect of HG treatment on the maxilla was actually significantly larger (P < 0.05) in narrow arches than in broad dental arches, so less expansion in the crowded cases cannot explain the finding. It is more likely that the maxillary canines are more restricted to move in crowded cases owing to space deficiency than in spaced arches, even though the arches were more expanded in crowded cases than in spaced cases. Another very interesting finding from the stepwise regression analysis was that space conditions in the anterior part of the maxilla appear to be the most important factor in how much the maxillary canine erupts vertically. The intercanine distance and especially the incisor space at T0 correlated significantly with a change in canine angulation (Angle A, T1–T0). In our study, we found a significantly larger increase in intercanine distance in the HGG than in the CG. This increase is consistent with previous studies (5, 6) in which an expanded inner HG bow was used. This effect may be due not only to the force applied, but also to the inner HG bow relieving the pressure of the lip musculature, and thereby creating a ‘lip bumper effect’. The clinical relevance of more vertical and distal movement of the maxillary canines observed in the HG group compared to the CG could have several implications. In patients with crowding in the anterior part of the maxilla, more vertical or distal movement of the canines than normal will relieve crowding and is therefore beneficial. In angle Class II patients, distal movement of the maxillary dentition is usually wanted and the HG-effect seen in this study may therefore be positive. In cases with lateral incisor root resorptions or risk for root resorptions triggered by maxillary canines, distal movement of the maxillary canines away from the lateral is required. At times, fixed appliances are contraindicated and therefore the distal movement of the maxillary canine by a simple appliance like a HG could be advantageous. During normal tooth eruption, children in the 7–8-year age range are often experience the ‘ugly duckling stage’ (23). In this period, the maxillary canine crown pushes onto the lateral incisor roots, causing them to flare and leading to an increase in Angle B. In the present study, we saw an increase in Angle B in the CG but no change in Angle B in the HGG. The reason for our seeing no change in the HGG is probably that the maxillary canines moved away distally from the lateral incisor when an HG is used. The fact that Angle B did not change in the HGG may also be because the upper incisors tend to move labially when using a HG, which has been shown earlier (5). Labial tilting of the incisors may change the lateral incisors’ position relative to the canines, as well as increase the interdental spaces. Together, these two effects may reduce the flaring of the lateral incisors. Patients in this study started HG treatment around 7.5 years of age. At this age, it is too early to detect palatal or buccal displacement of the canines (24). It is therefore not possible to conclude whether early HG treatment has an effect on ectopically erupting canines. Also, it is important to note that patients with other malocclusions may respond differently than the angle Class II sample selected. For this study, data from two previous RCTs were pooled. When pooling data from different studies, the combined results may contradict the results of the individual studies. This effect, also known as ‘Simpson’s paradox’, may arise when important subgroup characteristics in the different studies are not considered or weighted (25). In the present study, weighting of the subgroups was not performed, since the two RCTs were similar in design in five ways: (1) the RCTs were conducted in the same region in Finland, (2) they were carried out by the same research team, (3) the research team used the same treatment technique in both studies, (4) the age and gender of the participants were similar for both studies, and (5) the angle classifications were similar. Seventeen children were excluded from the study because their primary canines had been extracted owing to space discrepancy or ectopic positioning of the maxillary canine. Primary canine extraction may influence both the eruption path and the rate of maxillary canines, as well as reduce the dental arch length (10, 26–28), and thereby create bias. Two children in the HGG and three children in the CG had the mesial surface of their primary maxillary canines slightly sliced in order to facilitate the alignment of their maxillary lateral incisors. It is possible that this procedure might reduce the intercanine width, but it is doubtful that it would affect the maxillary canine eruption pattern, and so we decided not to exclude these patients. The reliability measurements were ‘excellent’ and ‘almost perfect’ for all measurements except the angular measurement of the maxillary canine relative to the maxillary midline (Angle C). The reliability of this measurement was rated as ‘acceptable’ in this study (ICC = 0.745), and some caution should therefore be taken when interpreting this variable. The lowered reliability of Angle C may be related to difficulty in assessing the maxillary midline in some panoramic radiographs, as blurring of panoramic images may happen in the maxillary midline owing to incorrect patient positioning in the X-ray machine (29). Overall, the most reliable variable was ‘Angle A’, and it was therefore chosen as the dependent variable in the linear regression analysis. HG compliance was not evaluated in the two studies involved. However, full Class I occlusion at the endpoint and a larger increase in most dental arch parameters in the HGG indicated a proper use of the HG. Estimation of crowding and spacing in mixed dentition is a challenge, since the precise size of the permanent teeth is not possible to measure. In our estimation of tooth size/arch length discrepancy, we used the well-known Moyers mixed dentition analysis (13) to assess the size of the permanent maxillary canines and premolars. The Moyers method may have population variations, and it is suggested that it may be necessary to develop prediction tables for specific populations (30). Certain caution should therefore be taken with regard to our calculations of tooth size/arch length discrepancy. A follow-up study to investigate the final differences in canine position between the HG and CG would be desirable. Conclusion This study showed that early HG treatment in children with angle Class II occlusion may change the eruption pattern of maxillary canines to a more vertical direction. The change in the eruption pathway seems to be related to space conditions in the maxillary arch, especially in the intercanine region, with the most significant effect in the HG group with spaced dental arches compared to crowded dental arches. Conflict of Interest None to declare. References 1. Pavlick , C.T. Jr . ( 1998 ) Cervical headgear usage and the bioprogressive orthodontic philosophy . Seminars in Orthodontics , 4 , 219 – 230 . Google Scholar CrossRef Search ADS PubMed 2. Tüfekçi , E. , Allen , S.B. , Best , A.M. and Lindauer , S.J . ( 2016 ) Current trends in headgear use for the treatment of class II malocclusions . The Angle Orthodontist , 86 , 584 – 589 . Google Scholar CrossRef Search ADS PubMed 3. Keim , R.G . ( 2009 ) The state of the profession . Journal of Clinical Orthodontics , 43 , 9 – 10 . Google Scholar PubMed 4. Pirttiniemi , P. , Kantomaa , T. , Mäntysaari , R. , Pykäläinen , A. , Krusinskiene , V. , Laitala , T. and Karikko , J . ( 2005 ) The effects of early headgear treatment on dental arches and craniofacial morphology: an 8 year report of a randomized study . European Journal of Orthodontics , 27 , 429 – 436 . Google Scholar CrossRef Search ADS PubMed 5. Mäntysaari , R. , Kantomaa , T. , Pirttiniemi , P. and Pykäläinen , A . ( 2004 ) The effects of early headgear treatment on dental arches and craniofacial morphology: a report of a 2 year randomized study . European Journal of Orthodontics , 26 , 59 – 64 . Google Scholar CrossRef Search ADS PubMed 6. Varlik , S.K. and Iscan , H.N . ( 2008 ) The effects of cervical headgear with an expanded inner bow in the permanent dentition . European Journal of Orthodontics , 30 , 425 – 430 . Google Scholar CrossRef Search ADS PubMed 7. de Oliveira , J.N. Jr , Rodrigues de Almeida , R. , Rodrigues de Almeida , M. and de Oliveira , J.N . ( 2007 ) Dentoskeletal changes induced by the Jasper jumper and cervical headgear appliances followed by fixed orthodontic treatment . American Journal of Orthodontics and Dentofacial Orthopedics , 132 , 54 – 62 . Google Scholar CrossRef Search ADS PubMed 8. Lima Filho , R.M. , Lima , A.L. and de Oliveira Ruellas , A.C . ( 2003 ) Mandibular changes in skeletal class II patients treated with Kloehn cervical headgear . American Journal of Orthodontics and Dentofacial Orthopedics , 124 , 83 – 90 . Google Scholar CrossRef Search ADS PubMed 9. Armi , P. , Cozza , P. and Baccetti , T . ( 2011 ) Effect of RME and headgear treatment on the eruption of palatally displaced canines: a randomized clinical study . The Angle Orthodontist , 81 , 370 – 374 . Google Scholar CrossRef Search ADS PubMed 10. Baccetti , T. , Leonardi , M. and Armi , P . ( 2008 ) A randomized clinical study of two interceptive approaches to palatally displaced canines . European Journal of Orthodontics , 30 , 381 – 385 . Google Scholar CrossRef Search ADS PubMed 11. Silvola , A.S. , Arvonen , P. , Julku , J. , Lähdesmäki , R. , Kantomaa , T. and Pirttiniemi , P . ( 2009 ) Early headgear effects on the eruption pattern of the maxillary canines . The Angle Orthodontist , 79 , 540 – 545 . Google Scholar CrossRef Search ADS PubMed 12. Naoumova , J. , Kurol , J. and Kjellberg , H . ( 2011 ) A systematic review of the interceptive treatment of palatally displaced maxillary canines . European Journal of Orthodontics , 33 , 143 – 149 . Google Scholar CrossRef Search ADS PubMed 13. Moyers , R.E . ( 1988 ) Handbook of Orthodontics . Year Book Medical Publishers , Chicago, IL , 3rd edn , pp. 369 – 379 . 14. Warford , J.H. Jr , Grandhi , R.K. and Tira , D.E . ( 2003 ) Prediction of maxillary canine impaction using sectors and angular measurement . American Journal of Orthodontics and Dentofacial Orthopedics , 124 , 651 – 655 . Google Scholar CrossRef Search ADS PubMed 15. Ericson , S. and Kurol , J . ( 1988 ) Resorption of maxillary lateral incisors caused by ectopic eruption of the canines. A clinical and radiographic analysis of predisposing factors . American Journal of Orthodontics and Dentofacial Orthopedics , 94 , 503 – 513 . Google Scholar CrossRef Search ADS PubMed 16. Bjerklin , K. and Ericson , S . ( 2006 ) How a computerized tomography examination changed the treatment plans of 80 children with retained and ectopically positioned maxillary canines . The Angle Orthodontist , 76 , 43 – 51 . Google Scholar PubMed 17. Lindauer , S.J , Rubenstein , L.K , Hang , W.M , Andersen , W.C , Isaacson , R.J . ( 1992 ) Canine impaction identified early with panoramic radiographs . Journal of the American Dental Association , 123 , 91 – 92 . Google Scholar CrossRef Search ADS PubMed 18. Henriques , F.P. , Janson , G. , Henriques , J.F. and Pupulim , D.C . ( 2015 ) Effects of cervical headgear appliance: a systematic review . Dental Press Journal of Orthodontics , 20 , 76 – 81 . Google Scholar CrossRef Search ADS PubMed 19. Itoiz , M.C . ( 2002 ) Carranza’s Clinical Periodontology . W.B. Saunders Company , Philadelphia, PA, 9th edn , pp. 26 – 27 . 20. Olive , R.J . ( 2002 ) Orthodontic treatment of palatally impacted maxillary canines . Australian Orthodontic Journal , 18 , 64 – 70 . Google Scholar PubMed 21. Sigler , L.M. , Baccetti , T. and McNamara , J.A. Jr . ( 2011 ) Effect of rapid maxillary expansion and transpalatal arch treatment associated with deciduous canine extraction on the eruption of palatally displaced canines: a 2-center prospective study . American Journal of Orthodontics and Dentofacial Orthopedics , 139 , e235 – e244 . Google Scholar CrossRef Search ADS PubMed 22. Pavoni , C. , Franchi , L. , Laganà , G. and Cozza , P . ( 2013 ) Radiographic assessment of maxillary incisor position after rapid maxillary expansion in children with clinical signs of eruption disorder . Journal of Orofacial Orthopedics , 74 , 468 – 479 . Google Scholar CrossRef Search ADS PubMed 23. Broadbent , B.H . ( 1941 ) Ontogenic development of occlusion . The Angle Orthodontist , 11 , 223 – 241 . 24. Mitchell , L . ( 2013 ) Assessing Maxillary Canine Position . Oxford University Press , UK , 4th edn , pp. 172 – 173 . 25. Bravata , D.M. and Olkin , I . ( 2001 ) Simple pooling versus combining in meta-analysis . Evaluation & the Health Professions , 24 , 218 – 230 . Google Scholar CrossRef Search ADS PubMed 26. Power , S.M. and Short , M.B . ( 1993 ) An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption . British Journal of Orthodontics , 20 , 215 – 223 . Google Scholar CrossRef Search ADS PubMed 27. Ericson , S. and Kurol , J . ( 1988 ) Early treatment of palatally erupting maxillary canines by extraction of the primary canines . European Journal of Orthodontics , 10 , 283 – 295 . Google Scholar CrossRef Search ADS PubMed 28. Sjögren , A. , Arnrup , K. , Lennartsson , B. and Huggare , J . ( 2012 ) Mandibular incisor alignment and dental arch changes 1 year after extraction of deciduous canines . European Journal of Orthodontics , 34 , 587 – 594 . Google Scholar CrossRef Search ADS PubMed 29. Molander , B. , Ahlqwist , M. and Gröndahl , H.G . ( 1995 ) Image quality in panoramic radiography . Dento Maxillo Facial Radiology , 24 , 17 – 22 . Google Scholar CrossRef Search ADS PubMed 30. Galvão , M. , Dominguez , G.C. , Tormin , S.T. , Akamine , A. , Tortamano , A. and de Fantini , S.M . ( 2013 ) Applicability of Moyers analysis in mixed dentition: a systematic review . Dental Press Journal of Orthodontics , 18 , 100 – 105 . Google Scholar CrossRef Search ADS PubMed © The Author(s) 2018. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

The European Journal of OrthodonticsOxford University Press

Published: Apr 3, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off