Fracture Resistance and Cusp Deflection of Lined or Non-lined Composite and Glass Hybrid Restorations Over Residual Demineralized Dentin.

PURPOSE To assess the fracture resistance (FR) and cusp deflection (CD) of lined or non-lined composite (CO) and glass hybrid (GH) restorations over residual demineralized dentin. MATERIALS AND METHODS In 48 extracted human premolars, artificial residual demineralized dentin was induced on pulpo-axial walls of standardized cavities. Various restorations were placed over this demineralized dentin: an experimental GH, a composite restoration (OptiBond FL+Tetric EvoCeram) without lining, or composite restorations with non-setting (Hypocal) or setting (Dycal) calcium hydroxide lining. After thermomechanical cycling, groups (n = 12) were compared regarding their CD and FR. RESULTS CD did not differ significantly between groups. FR was significantly lower in teeth restored with GH (median: 238 N; 25th/75th percentiles: 191/287 N) than in those restored with lined or non-lined composites (median range: 517-569 N; p < 0.05/Mann-Whitney), which did not differ significantly from each other (p > 0.05). CONCLUSION Within the conditions of this in vitro study, CH lining of pulpo-axial walls had only limited impact on CD and FR. GH showed the lowest FR and might not be optimal for restoring deep or extended cavitated lesions.