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PURPOSE: The aim of this study was to assess Candida albicans attachment on conventionally fabricated (polymethylmethacrylate, PMMA), CAD-CAM milled, and 3D-printed acrylic resin bases pre- and post-simulated thermal aging, along with examining material surface changes after aging. MATERIALS AND METHODS: Forty-six samples (10 mm × 10 mm × 2 mm) for each of four material groups (conventional heat-polymerized PMMA, CAD-CAM milled acrylic resin base, CAD-CAM 3D-printed methacrylate resin base, CAD-CAM 3D-printed urethane methacrylate resin base) were subjected to 0, 1, or 2 years of simulated thermal aging. Microscopic images were taken before and after aging, and C. albicans attachment was quantified using cell proliferation assay (XTT). Statistical analysis employed analysis of variance (α = 0.05). RESULTS: Two-way factorial analysis showed no significant differences based on acrylic resin type or thermal aging (p = 0.344 and p = 0.091 respectively). However, C. albicans attachment significantly differed between 0- and 2-year thermally aged groups (p = 0.004), mainly due to elevated initial attachments on CAD-CAM milled acrylic resin base and CAD-CAM 3D-printed urethane methacrylate resin base. CONCLUSIONS: Regardless of the fabrication technique and material combination, no significant differences were found in C. albicans adhesion pre- or post- thermal aging. Milled and 3D-printed bases compared favorably with heat- polymerized PMMA in their affinity for C. albicans attachment and surface characteristics after aging. These findings indicate that the risk of patients developing denture stomatitis might not be linked to the type of acrylic resin or fabrication method used.

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PURPOSE: The purpose of this in vitro study was to evaluate the effect of software on scan time, trueness, and precision of digital scans created using the CEREC Omnicam. MATERIAL AND METHODS: Sixty scans (20 scans/provider) of a standard reference cast were made by three different providers using the CEREC Omnicam with both CEREC Ortho 1.2.1 software (10 scans/provider) and CEREC SW 4.4.4 software (10 scans/provider). A digital full arch scan and the time to complete each scan were recorded. Trueness was calculated by overlaying the digital scans against a reference file created using the standard reference cast and a laboratory-based, white light, 3-dimensional scanner. Precision was calculated by overlaying each of digital scans against each other, using each scan as a reference. The non-parametric Mann-Whitney U-test was used to determine significant differences attributable to scanning software for each provider. RESULTS: The CEREC Ortho 1.2.1 software required a longer scan time than the CEREC SW 4.4.4 software for each provider (∼1 minute). No significant difference in trueness was observed within one provider. Two individual providers had higher precision when scanning with the CEREC Ortho 1.2.1 software than the CEREC SW 4.4.4 software. CONCLUSION: Software and scan strategy may affect the accuracy of complete-arch scans. The CEREC Ortho 1.2.1 software may demonstrate a speed-accuracy tradeoff, with generally longer scan times and possibly more precise scans.

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PURPOSE: To compare retentive forces of removable partial denture clasps traditionally fabricated with cobalt-chromium (CoCr) material and two computer-aided design and computer-aided manufactured (CAD/CAM) thermoplastic polymers. MATERIALS AND METHODS: Forty-eight clasp assemblies (16 CoCr, 16 polyetheretherketone (PEEK) and 16 polyetherketoneketone (PEKK) thermoplastic polymer) were fabricated for 48 mandibular tooth analogs. Individual clasps were inserted and removed on the tooth analogs utilizing a chewing simulator for 15,000 cycles to simulate 10 years of use. Retentive forces were measured utilizing a mechanical load tester at baseline and intervals of 1500 cycles. Data were analyzed with one-way Analysis of Variance, Tukey post-hoc, and paired T tests. RESULTS: Mean retentive forces between all groups were significantly different (p < 0.001). Retentive forces of CoCr clasps were significantly higher than both polymers (p < 0.001). The mean retentive forces for PEEK were not significantly different from PEKK (p = 0.23). A significant increase in retentive forces was observed for all three clasps after the first period of cycling, followed by continual decrease for the remaining cycles. At the endpoint of 15,000 cycles, no clasp assemblies showed lower retentive forces than at initial baseline. CONCLUSION: Thermoplastic polymer clasps demonstrated lower retentive forces compared to CoCr clasps. All three groups displayed a similar pattern of initial increase, followed by a gradual decrease, of retentive force. Despite this observation, the clasps maintained similar or higher retentive forces than measured at baseline. This resistance to fatigue and ability to fabricate with CAD/CAM technologies provides support for clinical use of these high-performance polymer (HPP) materials.

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PURPOSE: To compare the reverse torque values (RTVs) of abutment screws tightened from three different angles. MATERIALS AND METHODS: Implant abutment screws (n = 48), abutments (3), and regular platform implant analogs (3) were divided into three angulation groups (n = 16/group). Custom guides of 0°, 10°, and 20° were fabricated to verify driver angulation. The implant components for each group were assembled and all screws torqued to 35 Ncm using a universal screwdriver in a manual torque wrench at the appropriate angle. Torque was reapplied 10 minutes after initial torque. A digital gauge was then used to measure reverse torque at a position parallel (0°) to the implant analog. RTVs were recorded and compared using one-way ANOVA and Tukey HSD post-hoc comparisons (α = 0.05). RESULTS: All mean RTVs fell below the targeted torque value of 35Ncm, with some values in each angulation group 10% below of the target value. Mean RTVs in descending order from targeted torque value were: 10° group = 32.07 ± 0.97 Ncm, 0° group = 31.16 ± 1.12 Ncm, and 20° group = 30.08 ± 0.88 Ncm. One-way ANOVA revealed significant differences between angulation groups (F = 15.954, p < 0.001). Tukey HSD post hoc comparisons revealed that the mean RTVs of the three angulation groups were significantly different from each other (0° vs. 10°: p = 0.033; 0° vs. 20°: p = 0.011; 10° vs. 20°: p < 0.001). CONCLUSIONS: All RTVs did not reach the targeted torque value of 35 Ncm. Mean screw RTVs were significantly influenced by screwdriver insertion angulation.

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The method of fabricating an auricular prosthesis by digitally positioning a mirror image of the soft tissue, then designing and using rapid prototyping to produce the mold, can reduce the steps and time needed to create a prosthesis by the traditional approach of sculpting either wax or clay. The purpose of this clinical report is to illustrate how the use of 3-dimensional (3-D) photography, computer technology, and additive manufacturing can extensively reduce many of the preliminary procedures currently used to create an auricular prosthesis.

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