Wear performance of different bulk-fill class II resin composite restorations: 3-year clinical evaluation

This study aimed to evaluate three-year qualitative and quantitative wear performance of a preheated body, an injectable and sonic bulk-fill resin composite, and compare it to that of a body bulk-fill composite placed in Class II cavities in a randomized clinical trial. For the clinical trial, 50 patients with a total of 80 Class II restorations in molars under normal occlusion were enrolled in this study. Restorations were placed by a single operator according to their manufacturers' instructions, with (n = 20) for each material as follows: body bulk-fill (Filtek™ One Bulk-fill/Scotchbond Universal Adhesive), preheated body bulk-fill (Filtek™ One Bulk-fill/Scotchbond Universal Adhesive), injectable bulk-fill (G-ænial™ BULK Injectable/G-Premio BOND), and sonic bulk-fill resin composite (SonicFill3/OptiBond™ Universal). Immediately after placement, the restorations were finished/polished. Wear evaluation was performed qualitatively using modified Fédération Dentaire International (FDI) Criteria and quantitatively using Geomagic Control X software at baseline and at yearly intervals. The changes in FDI parameters during the three-year periods were analyzed and compared with the Chi-square test. For quantitative data, One Way ANOVA test was used to compare different studied groups over follow-up periods. The t-test was used to compare enamel surface volume loss with restoration volume loss within each studied group after one, two, and three years of follow-up. After 3 years, 78 restorations were recalled (97.5% recall rate) with 100% survival. All materials remained clinically acceptable regarding qualitative wear performance. For quantitative wear performance, ANOVA shows a significant difference between volume loss of the tested groups after one and two years, but not significantly different after three years. Mean volumetric wear (mm³) after 3 years was: body 0.020 ± 0.008, preheated body 0.018 ± 0.007, sonic 0.019 ± 0.009, and injectable 0.032 ± 0.010. T-test reveals insignificant difference between restoration and enamel volume loss within body, preheated body, and sonic-fill bulk-fill groups after three years. While injectable bulk fill volume loss significantly differs from enamel after one, two, and three years. All tested bulk-fill composites exhibited acceptable clinical performance qualitatively and quantitatively over 3 years. However, the injectable bulk-fill composite demonstrated greater volumetric loss than other materials, indicating lower long-term wear resistance under occlusal stress. All tested bulk-fill resin composites demonstrated excellent clinical performance and comparable wear resistance after three years. These findings support their reliable use in posterior Class II restorations, simplifying application without compromising longevity.Trial registration: ClinicalTrials.gov Identifier NCT05861908, registered on 17 May 2023.