Assessment of Marginal Microleakage of Restorations in the Treatment of Root Caries: A Randomized Controlled Open In Vitro Study

Background. Microleakage is a key clinically significant factor affecting restoration longevity, the risk of secondary caries, marginal discoloration, and postoperative sensitivity. Despite advances in restorative materials and adhesive systems, complete prevention of loss of marginal integrity at the tooth-restoration interface remains unattainable. Therefore, experimental assessment of microleakage considering restorative material type, adhesive protocol, and thermomechanical aging conditions remains a relevant area of research aimed at improving the clinical reliability of restorations.

Objective. To evaluate microleakage in Class II restorations with root involvement performed using different restorative techniques.

Methods. An in vitro study was conducted on 60 teeth extracted for orthodontic reasons and randomly assigned to three groups (n = 20). Standardized Class II cavities were restored using: (1) glass ionomer cement (GIC) + packable composite; (2) bulk-fill composite + eighth-generation self-etch adhesive; and (3) bulk-fill composite + eighth-generation universal self-etch adhesive. After thermocycling (1,000 cycles between 5 ± 2 °C and 60 ± 2 °C), specimens underwent microleakage evaluation. Marginal permeability was assessed microscopically using a dye penetration method with quantitative measurement of dye penetration along the restoration-tooth interface. Statistical analysis was performed using SPSS Statistics software (IBM, USA).

Results. Following thermocycling, Group 1 (open sandwich technique: GIC + packable composite) demonstrated the highest microleakage values, reaching 90.0% (83.8%; 92.3%), which were significantly greater than those observed in Groups 2 and 3 (p < 0.017). In the groups restored with flowable bulk-fill composites and eighth-generation adhesive systems, microleakage was significantly lower, measuring 49.0% (46.5%; 55.0%) and 52.0% (45.8%; 55.5%), respectively. No statistically significant differences were detected between these groups (p > 0.05).

Conclusion. Achieving adequate marginal sealing in root caries restorations remains a clinical challenge. The use of a flowable bulk-fill composite combined with a packable composite and an eighth-generation universal self-etch adhesive system resulted in significantly lower microleakage than the combination of glass ionomer cement and packable composite. These findings support the use of contemporary bulk-fill restorative techniques for root caries management and warrant further validation in clinical studies.