Shear Bond Strength and Temperature Rise of Orthodontic Brackets Bonding by Using a New 3-Second LED Mode

Objective:The aim of this study was to evaluate the effects of different curing times of a light-emitting diode (LED) on the bond strength of stainless steel brackets and to evaluate the temperature changes in the pulp chamber during curing of the composite.Materials and Method:Caries-free human first premolar and maxillary central incisor teeth extracted for orthodontic and periodontal reasons were used. For the temperature-measurement test, 60 incisor teeth were randomly divided into 3 groups (n=20), and 60 premolar teeth were used in 3 groups (n=20) for shear bond strength (SBS) testing. Three light sources—quartz tungsten halogen, LED, and LED in Xtra Power Quadrant mode—were used for polymerization of Transbond XT. Temperature variations were recorded by J-type thermocouple. For SBS testing, a universal testing machine was used. Statistical analyses were performed by χ2, ANOVA, and Holm-Sidak tests at p < 0.05 level.Results:The results of the SBS test revealed no statistically significant (p=0.305) differences between the halogen and LED groups. The conventional halogen light resulted in significantly (p<0.01) higher intrapulpal temperature changes.Conclusions:This study showed that high-intensity curing devices (3-seconds mode) can safely be used in bonding orthodontic brackets to teeth without causing a harmful effect on the dental pulp.