Temperature elevation during root canal treatment with a 445-nm diode
laser—an in vitro study
Received: 26 June 2017 / Accepted: 1 February 2018 / Published online: 28 February 2018
Springer International Publishing AG, part of Springer Nature 2018
Objective This study investigated the thermal effects of a 445-nm diode laser on tooth roots of endodontic treatment.
Material and methods A total of 15 human single-rooted extracted teeth were included in the survey. Samples were sectioned at
the cementoenamel junction. The root canals were instrumented using a rotary system. Each root was fitted into a resin mold and
was fixed in a vertical position using clamps. All samples were placed on a support in a thermal path at 37 °C. The root canals
were randomly divided into three groups (n = 5 each): samples were irradiated with 0.6 W continuous wave (CW), 0.4 W CW,
and 1.2 W gated mode, at a repetition rate of 10 Hz with a pulse duration of 50 ms. The time-dependent temperature elevations of
the cervical, middle, and apical thirds of the roots were recorded at a sampling rate of 2 Hz during laser irradiation with a K-type
thermocouple measurement system.
Results The mean temperature rise inside the roots in this study was below 10 °C, whereas the maximum temperature rise of
9.83 °C (0.6 W CW) and 9.81 °C (1.2 W gated mode, repetition rate 10 Hz, and pulse duration 50 ms) was registered in lower
incisors, and 4.97 °C was detected at 0.4 W CW. The thermal changes seen in the apical thirds of the root were statically
significantly (p < 0.001) and were greater than those at the coronal and middle thirds.
Conclusion The results of this study suggest that 445-nm diode lasers may provide a safe temperature for endodontic
Keywords Dental laser
The goal of primary endodontic treatment is to improve
root canal disinfection and to prevent re-infection [1–4].
Therefore, there is an agreement that an important aim of
the endodontic therapy is to eliminate the microorganisms
in the root canal .
To date, several studies [6–9] have shown that bio-mechan-
ical, also known as chemo-mechanical, methods play a signif-
icant role in the treatment of root canal systems. On the one
hand, these methods cannot completely remove the smear
layer, preventing the penetration of chemical irrigating solu-
tions into dentinal tubules [6, 10], leading to, as a conse-
quence, less than full elimination of nested bacteria [4, 11,
12]. In fact, the method is mostly limited to a dentin depth
between 100 and 300 μm. Deeper dentin tubules house many
thousands of remaining bacteria, and these bacteria can mi-
grate into and multiply inside the root canal system [13, 14].
Furthermore, the complexity of the root canal system is well
known to be one of the major challenges in root canal prepa-
ration , lateral canals, ramifications, and accessory canals
where conventional treatments cannot reach bacteria [6, 15,
16]. This may result in failure after endodontic treatment and a
recurrence of the infection [17, 18].
The advantage of using lasers is due to their high disinfec-
tion efficiency, using photo-thermal and photo-mechanical ef-
fects  to enhance cleaning, the reduction of bacteria ,
* Abeer Alshamiri
Department of Conservative Dentistry, Periodontology and
Preventive Dentistry, RWTH Aachen University Hospital,
Pauwelsstrasse 30, 52074 Aachen, Germany
Lasers in Dental Science (2018) 2:89–94