engleski

Composite Resin Overlays Increase the Fatigue Resistance of Endodontically-Treated Mola

Objectives: Evaluate the influence of material selection (composite resin vs. CAD/CAM porcelain), simulated load cusp (composite resin vs. stainless steel) and their effect on the in-vitro fatigue resistance and failure mode for overlay-type restoration of endodontically treated molars. Methods: Thirty extracted molars received root canal treatment followed by standardized tooth preparation (3mm cusp coverage, mesial box 1.5mm below the CEJ, distal box in enamel, glass-ionomer base, and immediate dentin sealing). Twenty overlays were milled in the ceramic Vita MKII block (groups MKIIGL and MKIIGL-Z) using Cerec3 and oven-glazed. Ten overlays were fabricated with a composite resin, Miris2 (group M2). The intaglio surfaces of the ceramic restorations were sandblasted, etched with hydrofluoric acid, and silanated. The composite resin overlays were sandblasted and silanated. After tooth preparation, restorations were luted with OptibondFL 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 1, 400N at a maximum of 30, 000 cycles each. A stainless steel load sphere was used for groups MKIIGL and M2, while a composite resin load sphere was used in group MKIIGL-Z. 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 porcelain overlays withstood all 185, 000 loading cycles (0% survival). Their average failure load was 1, 060N (steel antagonist) and 1, 280N (resin antagonist). Composite overlays showed superior performance (50% survival) and were associated with lower rate of fracture below the CEJ. Conclusions: Miris2 composite resin overlays showed higher fatigue resistance than MKII porcelain when loaded with a stainless steel antagonist. The simulated cusp in composite resin increased the fatigue resistance of MKII restorations compared to the stainless steel cusp.

composite resin overlays; fatigue resistance

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