Thickness and microhardness of deciduous tooth enamel
with known DLX3 mutation
Hong-Keun Hyun
a
, Jung-Wook Kim
a,b,
*
a
Department of Pediatric Dentistry, Dental Research Institute and BK21 Program, School of Dentistry,
Seoul National University, Seoul, South Korea
b
Department of Cell and Developmental Biology, Dental Research Institute and BK21 Program, School of Dentistry,
Seoul National University, Seoul, South Korea
1. Introduction
The distal-less homeobox 3 (DLX3) gene, located on chromo-
some 17q21, is a homeobox gene with a crucial role during
embryonic development.
1
It has been shown that a 4-bp
deletion (c.571_574delGGGG) in this gene results in tricho-
dento-osseous syndrome (TDO; OMIM 190320).
2
TDO syn-
drome is characterized by defects in hair, teeth and bone, with
an autosomal dominant inheritance pattern.
1,3
The main
clinical features include unique curly or kinky hair at birth that
eventually straightens in many cases, enamel hypoplasia with
taurodontism, and increased bone density.
4
The case with c.561_562delCT in the DLX3 gene reported by
Dong et al. resulted in only enamel phenotype (hypoplastic-
hypomaturation amelogenesis imperfecta with taurodontism,
AIHHT; OMIM 104510) while the same mutation identified
independently in two families of different ethnic background
was responsible for the classic TDO.
5
Thus it has been debated
whether this novel 2-bp deletion in the DLX3 gene causes non-
oral symptoms, such as defects in the hair, increased bone
density or nail involvement.
Dental phenotypes such as taurodontism, enamel thick-
ness and mineral content have been reported for the TDO
syndrome associated with the 4-bp deletion in the DLX3
archives of oral biology 54 (2009) 830–834
article info
Article history:
Accepted 16 June 2009
Keywords:
Enamel
DLX3
Thickness
Microhardness
Mutation
abstract
Aim: To investigate the thickness and hardness of teeth affected by a 2-bp deletion
(c.561_562delCT) in the DLX3 gene.
Methods and materials: Extracted maxillary deciduous second molar was collected from the
affected individual at age 12 years 7 months. Samples were sectioned buccolingually after
embedding in epoxy resin. We measured the enamel thickness and microhardness and
performed an elemental analysis using an electron probe microanalyser.
Results: On average, the hardness of the enamel with a 2-bp deletion in DLX3 was about 53%
of normal enamel hardness. The mutant enamel thickness was about half of the thickness
of the normal control. The calcium level in the enamel with the 2-bp deletion was slightly
decreased, while the magnesium level was slightly increased, in comparison to levels
measured for normal teeth.
Conclusion: This study shows that enamel affected by a 2-bp deletion in DLX3 has reduced
thickness as well as diminished microhardness. These data may explain the severe attrition
and interdental spacing observed in affected individuals.
# 2009 Elsevier Ltd. All rights reserved.
* Corresponding author at: Department of Pediatric Dentistry, Department of Cell and Developmental Biology, Dental Research Institute
and BK21 Program, School of Dentistry, Seoul National University, 275-1 Yongon-dong, Chongno-gu, Seoul 110-768, South Korea.
Tel.: +82 2 2072 2639; fax: +82 2 744 3599.
E-mail address: pedoman@snu.ac.kr (J.-W. Kim).
available at www.sciencedirect.com
journal homepage: www.intl.elsevierhealth.com/journals/arob
0003–9969/$ – see front matter # 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.archoralbio.2009.06.005