Influence of Preheating Resin Composites: A Nano CT assessment on Voids, Internal Adaptation and Post-Gel Shrinkage Strain

Background Resin-based composites stand as widely employed restorative materials in the field of dentistry, owing to their superior esthetic and physicochemical properties. Nevertheless, a notable limitation of these composites is the occurrence of polymerization shrinkage, leading to stress at the interface of tooth restoration. Over time, this phenomenon may result in marginal leakage and secondary caries, thereby causing restoration failure. Objectives Our study aimed to conduct a comparative evaluation of voids, internal adaptation, and polymerization shrinkage in Class II preheated composite restorations [5 seconds vs. 20 seconds] and composites at room temperature [20 seconds], utilizing Nano CT analysis. Methods Cylindrical Class II cavities were prepared on both mesial and distal sides of Fifteen freshly extracted human maxillary premolar teeth. The specimens were then randomly allocated into three groups and restored as follows: Group 1 [Filtek Supreme XT at room temperature, photocured for 20 seconds], Group 2 [Filtek Supreme XT composite preheated to 68°C in Compex HD, photocured for 20 seconds], and Group 3 [Filtek Supreme XT composite preheated to 68°C in Compex HD, photocured for 5 seconds]. Nano CT was employed for the qualitative assessment of the samples. Statistical analysis involved the Shapiro-Wilkins test, ONE WAY ANOVA test, followed by Tukey’s HSD Post hoc analysis. Results Significantly improved outcomes were observed in preheated composite groups, irrespective of the photo curing time, when compared to the room temperature composite group in terms of polymerization shrinkage. The room temperature composite group exhibited the highest void volume and frequency among the investigated groups. Conclusions Within the constraints of the study, it can be deduced that preheating at 68°C and light curing for 5 seconds enhance internal adaptation and reduce the incidence of voids in composite restoration. Clinicians should be informed about clinical techniques that mitigate shrinkage stress to improve the durability of composite restorations. Clinicians should be informed about clinical techniques that mitigate shrinkage stress to improve the longevity of composite restorations.