Microleakage evaluation of conservative adhesive resin restorations in premolar teeth using guided polymerization technique: An in vitro study

Polymerization shrinkage is a major problem in composite resin restorations and results in marginal leakage. This study evaluated the influence of guided polymerization on microleakage of conservative adhesive resin restorations (CARRs) in premolar teeth using two different light curing units. This in vitro study was performed using 72 freshly extracted human premolars without dental caries and crack. After cavity preparation in the occlusal surface, the teeth were randomly assigned to 12 subgroups of six each and then filled using the single bond\ Z250 system. Irradiation procedures were performed in the experimental group (through tooth structure), first control group (irradiation with conventional method) and second control group (irradiation with increased time) with high and low intensities of Light-emitting diode (LED) and Quartz-tungsten-halogen (QTH) light curing units. Microleakage was evaluated by a stereomicroscope at 40x magnification. The Kruskal-Wallis, Mann-Whitney and logistic regression with a significance level of 0.05 were used for statistical analyses. The “guided polymerization” technique had no significant effect on the microleakage of the study groups. None of the independent variables (light intensities, light curing units and irradiation protocols) had a statistically significant effect on microleakage. Irradiation with higher intensity and lower duration (within the limits of examined intensities and durations) and just from occlusal surface using LED or QTH light curing units, in order to reduce the working time in pediatric dentistry is recommended.