Background/Objectives: This in vitro study evaluated the effect of PEEK scan body splinting on geometric scan-body measurements obtained from complete-arch digital implant scans using two intraoral scanners under two simulated clinical scenarios. Methods: Two 3D-printed edentulous maxillary models, each containing six implants at positions #16, #14, #12, #22, #24, and #26 (FDI notation), were evaluated. Model 1 contained parallel implants, whereas Model 2 included selected implants angulated 20° buccally or distally. Each model was scanned with the CS 3600 and TRIOS 3 under non-splinted (NSS) and PEEK-splinted (SS) conditions. Ten repeated scans were acquired per experimental condition (80 scans in total). After alignment to a common reference coordinate system, the scan-body longitudinal-axis vector magnitude (Vector, mm) and a composite angular metric (Δφ, °) were calculated at each implant position. Position-specific differences among NSS, SS, controlNSS, and controlSS groups were evaluated with Kruskal–Wallis tests followed, when appropriate, by Bonferroni-adjusted pairwise comparisons (α = 0.05). Results: Statistically significant NSS–SS differences were observed only at selected implant positions. For the CS 3600, significant differences involved Vector and/or Δφ, whereas for the TRIOS 3 they were confined to Δφ. In every statistically significant NSS–SS comparison, the SS group showed a lower mean value of the corresponding metric. More statistically significant NSS–SS differences were observed in Model 2 for the CS 3600 and in Model 1 for the TRIOS 3. These findings describe differences in the analyzed geometric metrics and should not be interpreted as direct test–reference trueness estimates. Conclusions: PEEK scan body splinting was associated with changes in scan-body geometric measurements at selected implant positions, but the effect was not uniform across scanners or experimental conditions. Because Vector and Δφ were not calculated as direct test–reference deviations, the present data do not establish improved trueness, precision, or overall scanning accuracy. Further studies using direct reference-based error metrics are required to determine clinical relevance.
Background/Objectives: Computer-assisted navigation in total knee arthroplasty (TKA) aims to improve implant positioning and lower-limb alignment. However, its impact on functional outcomes, complications, and implant survival remains uncertain. This study compared radiological and functional outcomes, complications, reoperations, and implant survival between computer-navigated and conventional primary TKA using the same VEGA prosthetic system. Methods: This retrospective observational cohort study included 277 primary TKAs performed for osteoarthritis using the VEGA system between 2019 and 2025: 119 navigated and 158 conventional procedures. Radiological outcomes included postoperative LDFA, MPTA, and HKA alignment. Clinical outcomes included range of motion, Oxford Knee Score (OKS), and Net Promoter Score (NPS). Complications, reoperations, and implant survival were also assessed. Implant survival was analyzed using Kaplan–Meier curves and the log-rank test. Results: The navigated group had a postoperative HKA closer to neutral alignment than the conventional group (177.4° vs. 173.8°, p = 0.0002), and a greater proportion of knees within ±3° of neutral alignment (55.32% vs. 18.75%, p = 0.0003). Excellent postoperative ROM was more frequent after navigation (63.06% vs. 16.46%, p < 0.001). Median OKS was also higher in the navigated group (44 vs. 43, p = 0.031), whereas NPS did not differ significantly. Complication and reoperation rates were similar between groups. Estimated five-year implant survival was 95.88%, with no significant difference between groups (log-rank p = 0.326). Conclusions: Computer-assisted navigation using the VEGA system was associated with more accurate restoration of the mechanical axis and differences in selected functional outcomes. No significant differences were observed in complications, reoperations, or estimated implant survival. The retrospective design, potential confounding by surgeon, and limited follow-up warrant caution when interpreting these findings.
Background/Objectives: The second iron hand of the Franconian Imperial Knight Götz von Berlichingen represents a historically significant and mechanically sophisticated example of an upper-limb prosthesis. Its internal mechanism, documented by Christian von Mechel in 1815, comprises articulated phalanges, springs, locking levers, pins, and additional components integrated within the hand corpus. A previous study reconstructed the internal finger mechanics using three-dimensional computer-aided design (3D-CAD), finite element method (FEM) analysis, and a functional prototype at an enlarged scale of 2:1. The present study has a different and narrower objective: to produce a nominal 1:1 physical representation of selected components derived from that previously published CAD reconstruction and to present them in an exploded-view display. The work addresses visualization and protection of the display model rather than mechanical actuation or conservation of the historical artefact. Methods: Existing 3D-CAD data from the previously published 2:1 reconstruction were uniformly scaled by a factor of 0.5 using Autodesk Inventor Professional 2027. Preliminary fabrication was performed using fused deposition modeling (FDM) with polylactic acid (PLA). Because the preliminary prints did not reproduce the smallest features with sufficient visual definition, resin-based additive manufacturing was used for the final components. The components were arranged in an exploded-view configuration on a black acrylic-glass backing plate, with a transparent cover, wooden frame, LED illumination, labels, and a separate historical image display. Results: The selected CAD components were scaled to nominal 1:1 dimensions and incorporated into the display. The assessment of the two printing approaches was qualitative; no measurements of printed-part dimensional error, surface roughness, repeatability, or mechanical performance were collected. Resin printing was judged visually more suitable for the intended display than the preliminary FDM trial. Conclusions: The work provides a physical representation of selected components from a previously reconstructed CAD model. It does not establish the exact dimensions of the surviving historical prosthesis, demonstrate a complete 1:1 reproduction, or validate a functional mechanism. The display has potential for teaching and exhibition, but its educational effectiveness has not been evaluated.
Background/Objectives: This study evaluated how the elastic modulus of CAD/CAM crown materials affects the stress distribution within a maxillary second premolar and its supporting structures. Methods: A maxillary premolar was digitally reconstructed for finite element analysis. Three crown materials with differing elastic moduli (210, 70, and 37.95 GPa) were modeled under a 300 N static vertical occlusal load, with maximum and minimum principal stresses as the primary outcome measures. Results: At standardized, mesh-verified probe locations, crown-body stress increased monotonically with material stiffness (zirconia > VITA Suprinity > VITA Enamic): outer axial wall stress was ~60% higher for zirconia (11.4 MPa) than for VITA Enamic (7.0 MPa). In the supporting tooth structures the ordering was reversed, the more compliant crown transferring more stress to the tooth at equivalent locations, with enamel probe stress ~29% and dentin probe stress ~52% higher for VITA Enamic than for zirconia. The crown margin was the only region in which tensile stress approached or exceeded the compressive magnitude, particularly for the stiffer materials. Conclusions: The elastic modulus of the restorative material significantly influenced the stress state within the crown (differences up to ~60% at equivalent locations), while its influence on the supporting tooth structures, although measurable at equivalent locations, was small in absolute terms (about 1 MPa in dentin and 3 MPa in enamel). This provides biomechanical context to guide clinical material selection.
Background/Objectives: Previous studies on the digitization of complete dentures with intraoral scanners (IOSs) have reported inconsistent effects of scan path, and whether these effects depend on operator experience remains unclear. This exploratory in vitro study investigated the effects of scan path and operator IOS experience on the trueness of extraoral scanning of complete dentures. Methods: One maxillary and one mandibular complete denture were scanned with a TRIOS 5 IOS using four scan paths: TRIOS denture, TRIOS dentate, rolling, and BOPLM (buccal–occlusal–palatal/lingual–mucosal) methods. Two experienced and two novice dentists repeated each scan path 10 times per arch. Root mean square (RMS) values relative to reference data obtained with a noncontact three-dimensional scanner (FLARE Pro 16M) were analyzed using linear mixed models with operator as a random effect. Results: In the maxilla, the experience group × scan path interaction was significant (p = 0.034): among novice operators, the rolling method yielded smaller RMS values than the BOPLM method (mean difference = −0.0170 mm, p = 0.001), whereas scan paths did not differ among experienced operators (p = 0.114). No significant effects were found in the mandible. Scanning time did not differ among scan paths. Conclusions: Among novice operators, the rolling method showed higher trueness than the BOPLM method for maxillary dentures. The effect of scan path may depend on operator experience; however, this exploratory finding requires confirmation with a larger number of operators.
