IADR Abstract Archives
Load Symmetry And Failure Modes Of Repaired MOD Composite Restorations
Objectives: From our previous findings, off-axis loading results in repairable fractures of intact teeth. Even with the added strength that composite restorations give to extensive MOD cavities, restored molars are still susceptible to fracture. Thus, this study evaluates the load-bearing resistance and fracture modes of human molars with repaired MOD composite restorations.
Methods: After hydrolytic aging (2 years storage in water) plus mechanical cyclic fatigue (200 N for 1 million cycles), restored teeth were fractured under off-axis loading. The fractured surface was prepared with diamond burs, involving the distal-third of the MOD restoration and the fractured distal-buccal cusp. The teeth were repaired using Scotchbond Universal adhesive system and Filtek Z350 XT resin composite (3M ESPE). Samples were stored in water for 30 days for complete polymerization and hydration of the restorations, prior to off-axis load to fracture testing. For a systematic understanding of the role of load symmetry on the failures of MOD composite restorations, the following groups were also subjected to off-axis load to fracture test: Intact teeth, MOD Cavity (no restoration), with aged MOD composite restoration, with aged and fatigued MOD composite restoration, and with fractured/repaired MOD composite restorations as described above.
Results: Off-axis loading of repaired MOD restorations resulted in similar load-bearing capacity when compared to intact teeth and the fracture modes were also favorable, since no further fracture of tooth structure occurred outside of the repaired area of the restoration. For intact molar teeth, off-axis loading resulted in cusp fractures that were repairable, while most fractures were restricted to the restoration in the MOD group.
Conclusions: Load symmetry demonstrated its importance in the fracture modes of intact teeth, MOD restored molars, and repaired restorations. The extent of damage is minimized by off-axis occlusal loading, making a conservative repair with composite resin feasible, which yields load-bearing similar to intact teeth.
Methods: After hydrolytic aging (2 years storage in water) plus mechanical cyclic fatigue (200 N for 1 million cycles), restored teeth were fractured under off-axis loading. The fractured surface was prepared with diamond burs, involving the distal-third of the MOD restoration and the fractured distal-buccal cusp. The teeth were repaired using Scotchbond Universal adhesive system and Filtek Z350 XT resin composite (3M ESPE). Samples were stored in water for 30 days for complete polymerization and hydration of the restorations, prior to off-axis load to fracture testing. For a systematic understanding of the role of load symmetry on the failures of MOD composite restorations, the following groups were also subjected to off-axis load to fracture test: Intact teeth, MOD Cavity (no restoration), with aged MOD composite restoration, with aged and fatigued MOD composite restoration, and with fractured/repaired MOD composite restorations as described above.
Results: Off-axis loading of repaired MOD restorations resulted in similar load-bearing capacity when compared to intact teeth and the fracture modes were also favorable, since no further fracture of tooth structure occurred outside of the repaired area of the restoration. For intact molar teeth, off-axis loading resulted in cusp fractures that were repairable, while most fractures were restricted to the restoration in the MOD group.
Conclusions: Load symmetry demonstrated its importance in the fracture modes of intact teeth, MOD restored molars, and repaired restorations. The extent of damage is minimized by off-axis occlusal loading, making a conservative repair with composite resin feasible, which yields load-bearing similar to intact teeth.