The effect of transtooth curing technique using different LED light intensities on microhardness and depth of cure of nanofilled resin composite restorations

Aim: To evaluate the effect of different LED light intensities on microharness and depth of cure of nanofilled resin composite restorations using transtooth illumination technique with different thickness of buccal wall.
Materials and methods: The materials used for this study was nanofilled resin composite material (Filtex Z350XT, 3M, ESPE) shade A3with its corresponding bonding system (single bond universal, 3M, ESPE). A total of 10 sound extracted human maxillary premolar teeth were used in this study. The teeth were divided into 2 main groups of 5 teeth each according to curing light intensities; either standard LED curing mode (800 mW/cm2) for 30 sec or high intensity LED curing mode (1400 mW/cm2) for 10 sec. In each tooth, 2 cavity preparations were performed; moderate cavity preparation width (1/3 intercuspal distance) in the mesial aspect of each tooth and wide cavity preparation (1/2 intercuspal distance) in the distal aspect. All specimens were light cured using transtooth curing technique from the buccal and lingual surfaces. Each tooth was sectioned in a mesio-distal direction into 2 equal halves. Surface Micro-hardness of the specimens was determined. The mean microhardness values and hardness ratio % of the specimens were calculated. One way analysis of variance ANOVA, Tukey’s post hoc and independent t tests were used to compare between more than 2 groups. The significance level was set at p ≤ 0.05.
Results: The highest mean value for B/T ratio was recorded in Post. High I/3 ICD, whereas the lowest mean was recorded in Post.conv. I/3 ICD. ANOVA test revealed a significance difference between all groups (p<0.0001). Tukey’s post hoc test revealed no significant difference between the post high ½ ICD group and the post conv. 1/3 ICD group. Comparisons within the same groups revealed a significance difference within the post high groups, and within the post Conv. Groups (p= 0.0007, p=0.012 respectively. Moreover, there was a significant difference between the 1/3 subgroups (p<0.0001). However, the difference between the ½ ICD subgroups was not statistically significant (p=0.1174).
Conclusions: Transtooth curing techniques is greatly affected by cavity width. Light intensity is critical factor that should be considered when performing transtooth curing techniques. High LED light intensity successfully able to perform optimum polymerization for resin composite in both cavity width (moderate and wide).