Statement of problem: failure of resin composite restoration is most frequently caused by improper polymerization; it would be advantageous if the restoration possessed optimal depth of cure. Objective: The purpose of this study was to the depth of cure of resin composite restoration by using Trans-tooth curing technique with different light curing intensities
Material and methods: A total of 20 sound, non-carious human maxillary anterior teeth, were used in this study. The teeth were divided into 2 main groups of 10 teeth each according to the thickness of the labial tooth structure plate (T); either 1.5 mm plate thickness (T1) or 1 mm plate thickness (T2). Each main group was subdivided into 2 subgroups of 5 teeth each according to the intensity of the light curing (I); either conventional intensity light curing (I1), or high intensity light curing (I2). Two Standardized class III cavity preparations were prepared in the proximals and lingual surfaces. Resin composite restorations were applied then all the teeth prepared for micro-hardness assessment. Data were explored for normality using Kolmogorov-Smirnov test of normality. The results of Kolmogorov-Smirnov test indicated that most of data were normally distributed (parametric data), therefore, one-way analysis of variance (ANOVA) test was used to compare between groups. This was followed by Tukey's post hoc test and independent t test for pairwise comparisons. The significance level was set at p < 0.05.
Results: Comparing all groups revealed that the highest mean value was recorded in High intensity curing (1.5 mm), whereas the lowest mean value was recorded in conventional intensity curing at 1.5 mm. ANOVA test revealed that the difference between all groups was statistically significant (P=0.001).
Conclusions: Under the limitation of this in-vitro study it can be concluded that the thickness of the tooth structure as trans-tooth curing technique was applied is greatly affect the amount of light energy reached to the resin composite restoration. So therefore subsequently affect the degree of conversion of the composite restoration rather than the degree of light intensity.