In vitro performance and fracture resistance of interim conventional or CAD-CAM implant-supported screw- or cement- retained anterior fixed partial dentures

Statement of problem. Interim restorations represent an essential clinical treatment step; however, limited information is available concerning the performance of computer-aided design and computer-aided manufacturing (CAD-CAM) interim materials. Purpose. The purpose of this in vitro study was to evaluate the performance and fracture load of resin anterior implant-supported interim fixed partial dentures (IFPDs). Material and methods. Identical anterior resin IFPDs (maxillary central incisor to canine; n=16 per material) were milled from polymethylmethacrylate (PMMA) or di-methacrylate (DMA) systems with different filler content. The IFPD groups were split to simulate a chairside (cemented implant-supported prosthesis) or laboratory procedure (screw-retained implantsupported prosthesis). A cartridge DMA material served as a control. After interim cementation, combined thermocycling and mechanical loading (TCML) was performed on all restorations to approximate a maximum of 2.5 years of clinical function. Behavior during TCML and fracture force was determined, and failures were analyzed. The data were statistically investigated (Kolmogorov-Smirnov test, 1-way-ANOVA; post hoc Bonferroni, Kaplan-Meier survival, a=.05). Results. Drop out during TCML varied between no failures and complete failure during loading. For most systems, failure occurred between 120000 and 600000 mechanical loading cycles. For IFPDs without a screw channel fracture, values varied between 644 +/- 263 N and 987 +/- 101 N. Those with a screw channel fracture failed between 493 +/- 89 N and 951 +/- 248 N. Individual IFPDs had significantly higher mean fracture loads (P<.002), but the mean fracture values between IFPDs with and without a screw channel were not significantly different (P>.137). Failures were characterized by fracture of the connector (n=53) followed by mixed failures (n=22) or fractures at the abutment (n=21). Conclusions. These interim materials are sufficiently fracture resistant for the fabrication of implant-supported anterior IFPDs and are expected to survive between 6 months and 2 years before failure. The stability of IFPDs depended on the type of material but not on the restoration design (with or without a screw channel). (J Prosthet Dent 2021;126:575-8 0)

Automated summary

The study evaluated the performance and fracture load of resin anterior implant-supported interim fixed partial dentures (IFPDs), finding that these interim materials are sufficiently fracture resistant for the fabrication of implant-supported anterior IFPDs, expected to survive between 6 months and 2 years before failure. The stability of IFPDs depended on the type of material but not on the restoration design.