In-vitro assessment of temperature rise in the pulp during orthodontic bonding

IntroductionIn this in-vitro study, we evaluated the temperature changes in the pulp chamber during bracket bonding using 4 different light sources.MethodsEighty intact extracted maxillary central incisors were used. The teeth were divided into 4 groups of 20 teeth each. Brackets (Mini Twin, Dentaurum, Ispringen, Germany) were bonded with Transbond XT (3M Unitek, Monrovia, Calif) adhesive and light cured with low-intensity halogen light for 40 seconds, high-intensity halogen light for 40 seconds, light-emitting diode (LED) light for 20 seconds, and plasma arc light (PAC) for 6 seconds. Light curing was performed 5 mm from tooth surfaces. A J-type thermocouple wire was positioned in the center of the pulp chamber. The results were analyzed with analysis of variance (ANOVA) and the Tukey HSD test.ResultsANOVA and the Tukey HSD test showed that pulp chamber temperature changes were influenced by the type of light source. All groups showed significant differences between each other (P <0.001). The intrapulpal temperature changes induced by different light sources were the following: high-intensity halogen (6.84°C ± 2.44°C), low-intensity halogen (4.71°C ± 0.96°C), LED (2.95°C ± 1.12°C), and PAC (0.96°C ± 0.83°C).ConclusionsHigh- and low-intensity halogen light induced significantly higher intrapulpal temperature changes than did the LED and PAC. Except for the high intensity halogen light, orthodontic bonding with light-curing units did not exceed the critical 5.5°C rise in temperature reported to produce pulpal damage.