Purpose: The introduction of computer-aided design/computer-aided manufacturing (CAD/CAM) technology to the field of removable prosthodontics has recently made it possible to fabricate complete dentures using prepolymerized polymethyl methacrylate (PMMA) blocks that are claimed to have better mechanical properties. However, little was published concerning the clinical deformation of CAD/CAM PMMA. The purpose of this study was thus to compare the clinical deformation of CAD/CAM processed PMMA and conventionally processed heat-cured PMMA implant retained mandibular overdenture bases. Materials and Methods: Thoroughly selected ten completely edentulous patients have received two dental implants in the lower canine region. Two duplicate mandibular overdentures were constructed using CAD/CAM milled PMMA and conventionally constructed heat-cured PMMA. Self cure acrylic resin was used to pick up the attachments to the fitting surface of the mandibular overdenture base. Six linear strain gauges were attached to the lingual side of the polished surface of both overdenture bases to measure strains induced during maximal clenching and gum chewing. Results: Higher strain values were recorded with the conventionally constructed heat-cured PMMA overdentures compared to CAD/CAM constructed PMMA overdentures. The recorded strains were mainly compressive at the midline while the strains at implant sites were tensile. Higher strains were recorded during clenching compared to gum chewing in both assessed overdentures. Conclusion: CAD/CAM constructed PMMA implant-retained mandibular overdenture exhibits less denture deformation during function compared to conventionally constructed heat-cured PMMA overdenture.
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