Debonding of adhesively restored deep Class II MOD restorations after functional loading

Purpose: To assess debonding due to functional loading at the cervical dent in margins of deep Class II MOD restorations prepared with a variety of adh esive restoratives in endodontically-treated teeth. Materials and Methods: MOD preparations and endodontic treatment were carried out on extracted sou nd maxillary premolars. The cavities were restored with seven material comb inations: Three different resin-based composites (RBC) (Z100, Herculite XRV or Clearfil RP with their respective bonding systems); two bonded amalgam combinations (Valiant with Superbond D or with Panavia 21) and two sandwich combinations [the RBC Tetric with the polyacid-modified RBC (compomer) Com poglass or Z100 with the resin-modified glass ionomer Fuji II LC]. For each group, half of the samples were exposed to mechanical functional loading a nd the other half served as control. Imperfect bond formation and debonding due to loading was determined by dye penetration. In addition, the dye pen etration scores were correlated with the cusp fracture strengths of similar ly prepared restorations of a previous study. Results: After functional loa ding, the RBC in combination with hybridizing dentin bonding agents showed better preservation of marginal integrity than the sandwich restorations, w hich in turn performed better than the amalgam restorations (P < 0.05). Deb onding correlated with reduction in fracture resistance. Under the conditio ns of this study, debonding of adhesive MOD restorations by functional load ing can best be prevented by using RBC in combination with hybridizing dent in-bonding systems.