engleski

Composite resin overlay thickness influences fatigue resistance of endodontically-treated premolars

Aims: Evaluate the influence of composite resin CAD-CAM restoration thickness on the in-vitro fatigue resistance and failure mode for overlay-type restoration of endodontically treated premolars. Methods: Thirty extracted premolars received root canal treatment followed by a standardized tooth preparation (1.5, 2.5 or 3.5 mm cusp reduction, proximal gingival margins located 1.5 mm below the CEJ, glass-ionomer base and immediate sealed dentin with Optibond FL). Restorations were milled using Cerec3 and FiltekMZ100 composite resin blocks. The intaglio surfaces of the overlays were sandblasted and silanated. Tooth preparations were sandblasted and etched before insertion of the restoration. All restorations were luted with Optibond FL adhesive resin and preheated FiltekZ100. A closed-loop servo-hydraulic unit was used for simulating cyclic isometric chewing at 5 Hz, starting with a load of 200N (5, 000 cycles), followed by stages of 400, 600, 800, 1000, 1200 and 1400N at a maximum of 30, 000 cycles each. All samples were loaded until fracture or to a maximum of 185, 000 cycles. Groups were compared using the Kaplan-Meier survival curves. Results: None of the restored premolars with the 1.5mm cusp overlap restoration withstood all 185, 000 loading cycles (survival=0%). With 2.5mm and 3.5mm cusp overlap, the survival rate was 30% and 40%, respectively. The rate of fracture below the CEJ was 60%, 60% and 30% for 1.5, 2.5 and 3.5mm of cusp overlap, respectively. Survival of restored premolars with 2.5 and 3.5mm cusp coverage was not significantly different (p=.23). Conclusions: Thick FiltekMZ100 composite resin onlays (2.5 and 3.5mm cusp overlap) showed higher fatigue resistance than thin ones (1.5mm) and may be associated with fractures that are less subgingival.

composite resin overlay; fatigue resistance

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