Aim: This study aims to evaluate and compare the scanning accuracy of three IOSs and measuring the vertical marginal fit of three-dimensional (3D) printed resin retainers for single crown, three-unit, and cross-arch fixed partial denture situations. Settings and Design: Comparative In Vitro Study. Materials and Methods: A maxillary Nissin typodont with prepared abutments at #13, #23, #25, #27, and #16 served as the master model. A calibrated Shining 3D laboratory scanner provided the reference standard tessellation language (control). Each IOS generated six scans (n = 6/scanner; 18 test scans). Trueness and precision were derived by best-fit superimposition in Geomagic Design X. Fifty-four single-unit, three-unit, and cross-arch retainers were 3D-printed. Vertical marginal discrepancy was measured at mid-buccal and mid-lingual sites using a digital stereomicroscope (×20). Statistical Analysis Used: One-way ANOVA with Tukey’s post-hoc test was used for comparisons among scanners and prosthesis spans. Pearson’s correlation was used to assess the relationship between trueness and marginal fit, and Chi-square test was used to assess clinical acceptability. A P value ≤0.05 was considered statistically significant. Results: 3Shape TRIOS 3 showed the highest trueness (28.5 ± 5.2 µm) and precision (18.2 ± 3.1 µm), followed by Medit i700 and Shining 3D Aoralscan 3 (P < 0.001). Marginal discrepancy was lowest with 3Shape TRIOS 3 (52.4 ± 6.5 µm) and increased with span. A positive correlation was found between trueness and marginal fit (r = 0.82; P < 0.001). Clinical acceptability was 100%, 94.4%, and 77.8% for 3Shape TRIOS 3, Medit i700, and Shining 3D Aoralscan 3, respectively (P = 0.041). Conclusion: All three scanners delivered clinically acceptable results; 3Shape TRIOS 3 yielded the highest accuracy and best marginal adaptation. Accuracy and marginal fit deteriorated as prosthesis span increased.
Aim: This study aimed to evaluate and compare the vertical marginal discrepancy of DMLS copings fabricated from stone dies scanned using an intraoral scanner (IOS) and a laboratory scanner. Settings and Design: An in vitro comparative study was conducted to evaluate the influence of intraoral and laboratory scanning systems on the vertical marginal discrepancy of DMLS copings. Materials and Methods: A customised stainless-steel model simulating a prepared tooth with a shoulder finish line was fabricated. Impressions of the model were made using elastomeric impression material. Forty dies (n=40) were poured using type IV dental stone and divided into two groups (n=20). Group 1 dies were scanned using a 3Shape TRIOS IOS and Group 2 dies were scanned using a 3Shape extraoral laboratory scanner. Copings were fabricated using CAD/CAM software. Marginal gap between the die and the coping was measured at 4 predetermined points (buccal, lingual, mesial, and distal) using a stereomicroscope at ×40 magnification. Statistical Analysis Used: Data were analysed using SPSS (version 21, IBM Corp., Armonk, NY, USA). Student’s unpaired t-test was used to compare the tested groups. The collected data were analysed at a significance level set at P < 0.05. Results: The mean marginal gap between the die and coping was 11.44 μm for Group 1 and 29.62 μm for Group 2. The difference between the groups was statistically significant (P < 0.001). Conclusion: Copings fabricated from dies scanned using IOS demonstrated significantly lower vertical marginal discrepancies compared to those scanned using the laboratory scanner. However, the marginal gaps observed in both groups were within clinically acceptable limits.
Aim: Conventional complete denture (CD) fabrication requires multiple appointments, posing barriers for remote elderly patients.This study compared oral health-related quality of life (OHRQoL) and patient satisfaction between digitally fabricated dentures (DD) and conventional methods within the Royal Mobile Dental Services in Thailand. Settings and Designs: In this prospective randomized trial, 30 edentulous participants (aged 50–80 years) were allocated to CD (n = 15) or DD (n = 15) groups; 25 participants (CD: n = 15, DD: n = 10) completed the 1.5-month evaluation. Materials and Methods: The CD protocol used a four-visit, heat-polymerized workflow. The DD protocol used a three-visit workflow with mucostatic intraoral scanning and three-dimensional (3D) printing dentures. Participants and outcome assessors were blinded. Statistical Analysis Used: Outcomes were assessed after the first meal, at 24 h, and at 1.5 months using a Visual Analog Scale (VAS) for satisfaction and the Oral Health Impact Profile-14 for OHRQoL. Data were analyzed using Mann–Whitney U-tests. Results: Overall VAS satisfaction showed no significant intergroup differences (P > 0.05). At 24 h, the DD group reported significantly higher negative impacts (P < 0.05) on phonetics, taste perception, and food avoidance. By 1.5 months, most OHRQoL dimensions in the DD group normalized to match the CD group, but phonetic difficulties remained significantly higher (P < 0.05). Conclusion: 3D-printed dentures offer satisfaction comparable to conventional methods while reducing clinical visits. Early functional limitations resolve rapidly, but persistent phonetic issues suggest that standardized computer-aided design protocols may benefit from patient-specific customization to optimize speech outcomes in mobile dental settings.
Aim: To evaluate and compare stress distribution patterns in mandibular implant-supported overdenture retained with bar and ball attachment systems at two attachment heights (1 mm and 3 mm) using three-dimensional finite element analysis (FEA). Settings and Design: An in silico comparative three-dimensional finite element analysis study. Materials and Methods: Four three-dimensional finite element models of an edentulous mandible restored with two interforaminal bone-level implants (3.5 × 10 mm) were developed. The models incorporated bar attachments with heights of 1 mm (A1) and 3 mm (A2), and ball attachments with heights of 1 mm (B1) and 3 mm (B2). All materials were assumed to be homogeneous, isotropic, and linearly elastic. Complete osseointegration was simulated using bonded contact conditions. A mesh convergence test was performed, and mesh refinement continued until the change in peak von Mises stress between successive mesh refinements was <5%. A static vertical load of 100 N was applied at the central occlusal fossa of the first molar under unilateral and bilateral loading conditions. Stress distribution was evaluated qualitatively and quantitatively using von Mises stress analysis. Statistical Analysis Used: No statistical analysis was performed. Stress distribution was compared descriptively using qualitative stress distribution patterns and quantitative von Mises stress values generated by the finite element models. Results: Under unilateral loading, stresses were concentrated predominantly on the working side, with the implant neck serving as the principal site of stress concentration. Increasing attachment height increased stress magnitudes in both bar and ball attachment systems under unilateral and bilateral loading conditions. Overall, stress concentrations were greatest at the implant neck, followed by the implant body and apical region. Cortical bone consistently exhibited higher stress values than cancellous bone across all models. Conclusion: Within the limitations of this finite element study, attachment height and splinting configuration influenced peri-implant stress distribution. Increased attachment height was associated with greater stress magnitudes in both attachment systems.
Aim: This study aimed to compare the marginal and internal adaptation of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia crowns and heat-pressed ceramic-veneered zirconia crowns fabricated using a standardized digital workflow. Settings and Design: An in vitro laboratory study was conducted using standardized epoxy resin dies and zirconia crowns fabricated by two different laboratory workflows. Materials and Methods: Twenty zirconia crowns were fabricated from a single STL dataset with a 50-µm cement space and divided into two groups (n = 10): monolithic CAD/CAM zirconia (MZ) and bilayer heat-pressed ceramic-on-zirconia (PVZ). All crowns were fabricated on epoxy resin dies replicated from a CAD/CAM-milled stainless-steel master die. After cementation with glass ionomer cement under a controlled seating load of 50 N, the specimens were sectioned buccolingually. Marginal and internal gaps were measured using scanning electron microscopy at eight predetermined sites. Statistical Analysis Used: Data were evaluated for normality using the Shapiro–Wilk test. Intergroup comparisons were performed using the Mann–Whitney U-test, with statistical significance set at P < 0.05. Bonferroni adjustment was applied for exploratory multiple comparisons. Results: For the primary outcome, composite internal adaptation was lower in the monolithic CAD/CAM zirconia crown group than in the heat-pressed ceramic-veneered zirconia crown group (103.07 vs. 111.38 µm; P = 0.019), with a moderate effect size (r = 0.53). Composite marginal adaptation did not differ significantly between the groups (88.90 vs. 95.73 µm; P = 0.226). Conclusion: Both fabrication workflows produced zirconia crowns with marginal and internal adaptations within clinically acceptable limits. Monolithic CAD/CAM zirconia crowns showed slightly smaller internal discrepancies than heat-pressed ceramic-veneered zirconia crowns; however, the magnitude of this difference is unlikely to affect clinical seating or cementation.
