Vickers Hardness and Microleakage of Coated Glass-Hybrid and High-Viscosity Glass Ionomer Systems in Thermocycled Conservative Class II Cavities: An In Vitro Study.

Background/Objectives: Glass-hybrid and high-viscosity glass ionomer systems were developed to address limitations of conventional glass ionomer cements. This in vitro study compared post-thermocycling Vickers hardness and microleakage of a coated glass-hybrid system and a coated high-viscosity glass ionomer system in conservative Class II cavities. Methods: Thirty extracted human maxillary first premolars each received both systems in standardized mesio-occlusal and disto-occlusal cavities, enabling paired within-tooth comparisons. Following thermocycling and methylene blue immersion, Vickers hardness was measured on polished restoration cross-sections at occlusal and gingival locations. Microleakage was quantified using a continuous microleakage index and ordinal dye penetration scores. Results: The EQUIA Forte HT system had a higher tooth-level mean Vickers hardness than the Gold Label IX Extra system (95.05 ± 6.58 HV vs. 91.33 ± 7.50 HV), with a mean paired difference of 3.72 HV (95% CI, 0.32 to 7.11; p = 0.033; Cohen's dz = 0.41, 95% CI, 0.03 to 0.78). The location-specific mixed model also showed an effect of restorative system (p = 0.025), whereas neither testing location nor the system × location interaction was significant. No significant between-system difference was detected for the microleakage index or for either ordinal dye penetration score. Conclusions: Within the limitations of this in vitro study, the EQUIA Forte HT system had a modestly higher post-thermocycling tooth-level mean Vickers hardness than the Gold Label IX Extra system, although the clinical relevance of the difference remains uncertain. No between-system differences were detected in dye penetration outcomes.