Comparison of micro-CT and conventional dye penetration for microleakage assessment after different aging conditions

Aim: The aim of this study was to compare microleakage assessment by micro-tomography (micro-CT) and conventional microscopy in class V restorations after different aging treatments. Methods: Class V cavities were prepared in sound human molars and restored with composite (Filtek Supreme XTE) after application of a self-etch adhesive (Clearfil SE Bond). Sealing ability was evaluated by assessing silver nitrate penetration along enamel and dentin margins either by micro-CT or by conventional stereomicroscopy. Class V cavities were divided in three groups (each n = 5): control: no aging, thermocycling: 10,000 cycles, 5–55 °C; thermo-erosive cycling: thermocycling with concomitant storage in HCl (pH 2.1, 5 min, 6×/day, 8 days). Penetration of silver nitrate was quantified by micro-CT and stereomicroscopy (25-fold magnification). Data for silver penetration assessed by stereomicroscopy and micro-CT were checked for normality and analyzed by Pearson or Spearman correlations. Differences between the aging effects were analyzed by one-way ANOVA (enamel) or Kruskal-Wallis tests (dentin) (p< 0.05). Results: For enamel, the correlations between stereomicroscopy and micro-CT data were not significant. For dentin, silver penetration depths obtained by stereomicroscopy and by micro-CT were moderately correlated (r=0.54, p=0.039), while volume of silver penetration (micro-CT) was not significantly correlated with penetration depth of silver (stereomicroscopy). Thermo-erosive cycling mostly increased microleakage compared with the control group and restorations submitted to thermocycling. Conclusions: Thermo-erosive aging increased the microleakage at enamel and dentin. The micro-CT analysis resulted in lower values of microleakage compared with the conventional stereomicroscope. Clinical significance: Microleakage is often used to evaluate the interfacial integrity of adhesives with dental hard tissues. The micro-CT analysis underestimated the dye penetration compared with the assessments made by the conventional stereomicroscopy, leading to lower microleakage values.