Optimization of large MOD restorations: Composite resin inlays vs. short fiber-reinforced direct restorations

• Published in: Dental materials 2018-04, Vol.34 (4), p.587-597
• Main Authors: Soares, Luciana Mara, Razaghy, Mehrdad, Magne, Pascal
• Format: Article
• Language: English
• Subjects: CAD; CAD/CAM; CAM; Chewing; Composite resin; Composite Resins - chemistry; Computer aided design; Computer aided manufacturing; Crack propensity; Cracks; Cyclic loads; Dental enamel; Dental Enamel - chemistry; Dental Materials - chemistry; Dental Restoration Failure; Dental Restoration, Permanent - methods; Dental restorative materials; Dental Stress Analysis; Dentin; Dentistry; Failure analysis; Fatigue cracks; Fatigue failure; Fatigue resistance; Fiber composites; Fiber reinforced polymers; Fibers; Fracture mechanics; Humans; In Vitro Techniques; Inlays - methods; Isometric; Mastication; Materials fatigue; Materials Testing; Mechanical properties; Molar; Molars; Optimization; Photography; Resin Cements; Resins; Short fibers; Shrinkage; Shrinkage stress; Surface Properties; Teeth; Transillumination
• ISSN: 0109-5641; 1879-0097
• DOI: 10.1016/j.dental.2018.01.004

•Mechanical performance and enamel crack propensity of composite restorations.•Shrinkage-induced enamel cracks were tracked by transillumination photography.•Acumen 3; MTS Systems was utilized to perform fatigue tests and evaluation.•Short-fiber reinforced composite-resin was used for the direct approach.•Semi-direct, and CAD/CAM inlays restorations were compared with the direct approach. To compare mechanical performance and enamel-crack propensity of direct, semi-direct, and CAD/CAM approaches for large MOD composite-resin restorations. 45 extracted maxillary molars underwent standardized slot-type preparation (5-mm depth and bucco-palatal width) including immediate dentin sealing (Optibond FL) for the inlays (30 teeth). Short-fiber reinforced composite-resin (EverX Posterior covered by Gradia Direct Posterior) was used for the direct approach, Gradia Direct Posterior for the semi-direct, and Cerasmart composite resin blocks for CAD/CAM inlays. All inlays were adhesively luted with light-curing composite-resin (preheated Gradia Direct Posterior). Shrinkage-induced enamel cracks were tracked by transillumination photography. Cyclic axial isometric chewing (5-Hz) was simulated, starting with a load of 200N (5000 cycles), followed by stages of 400, 600, 800, 1000, 1200, and 1400N (maximum 30,000 cycles each) until fracture or to a maximum of 185,000 cycles. Survived specimens were subjected to cyclic-load-to-failure test at 30-degree angle on the palatal cusp. Only small shrinkage-induced cracks were found in 47% of the direct restorations compared to 7% and 13% of semi-direct and CAD/CAM inlays, respectively. Survival to accelerated fatigue was similar for all three groups (Kaplan–Meier p>.05) and ranged between 87% (direct) and 93% (semi-direct and CAD/CAM). Cyclic-load-to-failure tests did not yield significant differences either (Life Table analysis, p>.05) with median values of 1675N for CAD/CAM inlays, 1775N for fiber-reinforced direct restorations and 1900N for semi-direct inlays. All three restorative techniques yielded excellent mechanical performance above physiological masticatory loads. Direct restorations performed as good as inlays when a short-fiber reinforced composite-resin base was used.