Journal of Advanced Prosthodontics最新文献

Purpose: Removable partial dentures (RPDs) require metal frameworks for support, stability, and retention. Conventional impression methods are time-consuming and may introduce inaccuracies that affect framework fit. Intraoral scanning (IOS) offers a digital alternative that may improve accuracy and efficiency; however, few studies have quantitatively compared frameworks fabricated using IOS data with those fabricated using conventional methods. This study aimed to compare the accuracy of RPD frameworks fabricated using conventional and IOS-based methods.

Materials and methods: This study included 15 arches from 13 patients requiring RPDs. Each arch received two metal frameworks, one fabricated using the conventional impression method (CON group) and the other using IOS (IOS group). Qualitative evaluations included visual inspection and pressing with a plugger, whereas quantitative evaluations were performed using three-dimensional superimposition and gap measurements at the rest-seat areas. Paired t-tests were used to compare the accuracy, and two-way analysis of variance was used to evaluate the interaction between the fabrication method and tooth position.

Results: All frameworks met the qualitative evaluation criteria. In the quantitative evaluation, the IOS group exhibited a significantly smaller mean gap (201 ± 78 µm) than the CON group (239 ± 83 µm) (P = .015). Furthermore, the IOS group demonstrated significantly greater accuracy, particularly at the terminal abutments of distal-extension RPDs.

Conclusion: Clinically acceptable RPD framework accuracy was achieved in both groups. However, accuracy was significantly better in the IOS group, especially at the terminal abutments of distal-extension RPDs.

Purpose: The biomechanical advantage of selective pressure impressions over mucocompressive techniques remains unclear. This study aimed to determine whether selective pressure techniques offer substantial biomechanical advantage over mucocompressive impressions using clinical computer simulation.

Materials and methods: Two models were analyzed: Model C, with mucocompressive impression tray, and Model S, with selective pressure impression tray with 10-mm diameter circular relief in the midline. Each model included the tray, polyvinyl siloxane (PVS), mucosa, cortical, and cancellous bone. Seven locations were designated, from which the results were analyzed. With a vertical load of 49 N on the palatal area, pressure, von Mises stress, and displacement were evaluated. Statistical analysis was performed using paired-samples t-test and effect size estimation (Cohen's d).

Results: Both models generated mucosal displacement and stress transmission to the underlying structures upon load application. In Location 3, where the relief was placed, Model S exhibited lower pressure, stress, and displacement than Model C, indicating localized force reduction. Conversely, other locations exhibited higher values in Model S than in Model C. Low stress in bone for both trays suggested that tray design had minimal effect on bone. All variations demonstrated small effect sizes (d ≤ 0.2), despite statistical significance (P < .007).

Conclusion: Selective pressure trays modified tissue loading locally at the relief site; however, these did not seem to provide a substantial biomechanical advantage, particularly on bone. Their clinical relevance remains limited and needs further supporting evidence.

Purpose: Material surfaces can influence the biological response of soft tissues, particularly during the early stages of healing and maturation. This study assessed whether the type of surface finish (glazed or polished) of monolithic zirconia single crowns impacts the health of peri-implant soft tissues during the first 6 months of clinical function. Infrared thermography was employed to assess soft tissue conditions.

Materials and methods: This was a prospective, randomized, intra-participant clinical trial. Twenty single crowns, supported by posterior implants, were fabricated in monolithic zirconia using computer-aided design/computer-aided manufacturing. For each crown, the mesial and distal surfaces were randomly allocated to receive either a glazed or a polished surface finish. Data were collected at 7 (T1) and 180 days (T2) following crown placement, using clinical examinations (assessing pain/discomfort, biofilm formation, bleeding, inflammation, and suppuration) and infrared thermography (to record thermogram values in Celsius). The data were analyzed using both descriptive and inferential statistics.

Results: No significant clinical differences in peri-implant soft tissue health were identified between the glazed and polished surface treatments at T1, T2, or across the evaluation period. Infrared thermography revealed a significant decrease in temperature from T1 to T2 for some polished and/or glazed subgroups when comparing the peri-implant mucosal phenotype, dental arch, and tooth regions. However, no significant differences were observed between the polished and glazed groups.

Conclusion: Both glazing and polishing are suitable surface treatments for monolithic zirconia and do not adversely affect peri-implant soft tissue health within 6 months after crown installation. Infrared thermography has the potential to be a complementary tool for the objective evaluation of soft tissue healing.

Purpose: This in vitro study aimed to evaluate the effect of clinically practical auxiliary geometric devices (AGD) on measurement trueness and scan time in full-arch implant-supported prostheses, focusing on different intraoral scanners (IOS) and implant angulations.

Materials and methods: Four implants were planned in an edentulous maxillary arch and divided into two groups based on posterior implant angulation: Model A (Parallel) and Model B (30°). Each model was evaluated under three auxiliary geometric devices (AGD) application types (std, agd1, agd2), and scanned using three different intraoral scanners (IOSs) [3Shape Trios 3 (T), Medit i700 (M), and Cerec Primescan (PS)], resulting in nine groups per model (n = 10). Scanning times and faulty scans were recorded. A conventional impression (CON) was taken as a control and digitized with a desktop scanner. Trueness was analyzed using Geomagic Control X, with statistical significance set at P < .05.

Results: Group B had higher RMS values than Group A (40.3 µm vs. 34.7 µm). T_std in Group A (51.4 µm) and T_std (53.1 µm) and Con (50.7 µm) in Group B exceeded the acceptable deviation limit. AGDs reduced deviations to acceptable levels in the Trios 3. The Primescan scanner had the shortest scanning times. AGD use, especially in T_agd2 and M_agd2, shortened scan times and eliminated erroneous scans.

Conclusion: The use of AGD has a significant impact on scanners' scanning trueness and time.

Purpose: Designing restorations remains challenging because the process is time-consuming and requires operator skill and experience. This clinical study evaluated the fit accuracy of polymerized complete crowns fabricated using a web-based 3D generative artificial intelligence design (GAID) method compared to crowns fabricated using a conventional computer-aided design (CCAD) method.

Materials and methods: Sixty-two patients requiring complete crowns in maxillary and mandibular premolars and molars were enrolled. After tooth preparation, digital impressions were taken using an intraoral scanner. Two crowns per patient were designed: one used a web-based automatic 3D GAID software program, and the other used a standard human-driven CCAD software program. The crowns were 3D-printed and delivered to the patients. Marginal and internal discrepancies and occlusal contacts were evaluated using a digital triple scan technique. Statistical analysis used two one-sided t-tests for paired samples to assess crown accuracy in both methods (α = .05).

Results: Marginal gaps of crowns made by both methods showed equivalence in the buccal, mesial, and distal regions; however, in the lingual region, the GAID method produced higher marginal discrepancies (P > .001). Regarding internal gaps, no significant difference was observed between the two methods. Crowns produced by the GAID method exhibited larger occlusal discrepancies than those made by the CCAD method (P < .001).

Conclusion: The fit accuracy of crowns fabricated using generative artificial intelligence was equivalent to those produced using the manual-input computer design method when the margins were well defined. While marginal and occlusal discrepancies were within clinically acceptable range, careful attention must be given to automated design outcomes, considering various tooth preparation shapes, anatomical structures, and clinical variations.

Purpose: This in vitro study evaluated the fit of implant-supported bars fabricated using different computer-aided manufacturing (CAM) techniques.

Materials and methods: A mandibular model with four dental implants (Nobel Replace Conical Connection, 3.5 mm × 11.5 mm) was fabricated using photoelastic resin. Sixteen Co-Cr implant-supported bars were produced using four CAM techniques: casting milled wax (CMW), selective laser sintering (SLS), dense milling (DM), and soft milling (SM) (n = 4). Fit was assessed through photoelastic stress analysis and digital scanning with a topographic digitizer (BreuckmannSmartScan). A standardized coordinate system was used for fit analysis. Data were analyzed using the Kruskal-Wallis test, with Dunn-Bonferroni for multiple comparisons (α = .05).

Results: Photoelastic analysis showed that bars fabricated with DM exhibited the lowest stress levels, while SM showed moderate stress. Fit was significantly influenced by Δy-z, Δd_in, and Δd_out (P < .01), whereas Δhex and Δx-z had no significant effect (P > .05). The highest mean Δy-z value was observed in CMW (0.68 ± 0.28°) and the lowest in SLS (0.01 ± 0.34°). CMW had the highest Δd_in (-160.44 ± 61.17 µm) and DM the lowest (-5.46 ± 11.80 µm). DM showed the highest Δd_out (46.23 ± 39.32 µm), while SM had the lowest (-55.04 ± 35.06 µm), with significant differences among the techniques.

Conclusion: In conclusion, full-arch implant supported Co-Cr bars fabricated using the different CAM techniques exhibited clinically acceptable passive fit.

Purpose: This study investigated how different data collection methods affect final restoration design and dynamic occlusal morphology.

Materials and methods: Digital systems allow intraoral recording of functional occlusal paths through the digitally recorded functionally generated pathway (DRFGP) technique, using intraoral scanners and optical jaw tracking. Two substudies were conducted. Study I assessed full-arch occlusal splints in 31 healthy participants with Angle Class I occlusion, comparing outcomes from a virtual articulator and jaw tracking systems. Study II evaluated three-unit fixed partial dentures (FPDs) in 12 participants, comparing models from virtual articulators, face scans, and jaw tracking. Additionally, sagittal and protrusive condylar inclinations and the Bennett angle were compared between two jaw tracking systems: an optical tracking device (OTD) and an electronic tracking device (ETD). Statistical analysis included normality tests and non-parametric tests with significance set at P < .05.

Results: Condylar inclination measurements significantly differed between OTD and ETD (P < .01). Lateral condylar inclination values showed discrepancies, excluding mediotrusion. Occlusal splint surfaces showed significant deviations using OTD (P < .01). For FPDs, tooth 1.6 exhibited notable differences.

Conclusion: Despite significant differences in jaw tracking measurements, the overall impact on occlusal design for both full-arch and FPD restorations was minimal. Semi-adjustable articulators produced comparable outcomes to digital methods, supporting the clinical reliability of both conventional and digital workflows.

Purpose: This systematic review and meta- analysis aimed to evaluate the occlusion variations in single posterior implant supported fixed prostheses.

Materials and methods: The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed and the study was registered in the international prospective register of systematic reviews (PROSPERO) platform (CRD42024501657). A systematic search of the PubMed/MEDLINE, Embase, Web of Science, and Cochrane Library databases published until December 2024 was done by 2 independent reviewers, without restriction of language or publication date. A meta-analysis was performed using the R version 4.0.2, considering the significance level P < .05. Quality assessments were performed using the ROBINS-I tool.

Results: Five studies were included, totaling 150 participants and 146 posterior single implant-supported fixed prostheses evaluated over time. The meta-analyses were performed with different follow-up months to evaluate the means in percentage the occlusal variations: 0,5 months (5,91%); 3 months (7,70%); 6 months (8,29%); 12 months (13,01%); 24 months (14,31%); 36 months (19,41%). Significant difference (P < .05) was presented from 12 months of follow-up.

Conclusion: Implant-supported prostheses present occlusal variations after installation, with a progressive increase over time, being significant after 12 months of installation. Therefore, careful long-term monitoring of occlusion is essential, with occlusal adjustments being considered when necessary.

Purpose: This study aims to compare the occlusal trueness and precision of teeth manufactured using two modern digital milling processes.

Materials and methods: A total of 38 complete dentures (CDs) were fabricated and analyzed. CDs in Group 1 (monolithic) (n = 19) were produced using a monolithic bicolor resin disk, whereas in Group 2 (oversize) (n = 19) were fabricated using the oversize process, which involves two separate resin disks of different colors. Two investigation methods were developed to evaluate trueness and precision: cusp area analysis and cusp vertex analysis. The study included three levels of analysis: a comparison of the two measurement methods, an evaluation of the monolithic versus oversize processes, and an assessment of under- and overcontouring inaccuracies.

Results: Statistical analysis using the Welch two-sample t-test, the non-parametric Wilcoxon signed-rank test, and the modified signed-likelihood ratio test (SLRT) revealed a statistically significant difference (P < 2.2 × 10^-16) between the two measurement methods (vertex vs. area) for both the monolithic and oversize groups, with the vertex method demonstrating greater accuracy. The analysis of over- and undercontouring inaccuracies revealed that 55% of the surface for the monolithic process exhibited overcontouring, compared to 99% for the oversize process, indicating a strong tendency toward surface roughness in the latter.

Conclusion: The monolithic milling method exhibited significantly superior accuracy compared to the oversize process (P < .05). Additionally, the Reference Point System (RPS) metrological method proved more reliable than the best-fit method for comparing complex structures, offering more accurate estimates of both trueness and precision.

Purpose: The purpose of this study was to assess the effect of thermomechanical aging on fracture strength of CAD/CAM (computer aided design and computer aided manufacturing) anterior crowns.

Materials and methods: A resin maxillary central incisor was prepared and 96 epoxy resin replicas were obtained. Anterior crowns were produced and divided into four groups: IPS (IPS e.max CAD, 1.5 mmthickness), CD (Celtra Duo, 1.5 mm thickness), GC (GC Initial UHT, 1.5 mm thickness) and GC1 (GC Initial UHT, 1 mm thickness). Twelve crowns of each group were subjected to a chewing simulator for 240,000 cycles, and the other 12 crowns were regarded as control. Fracture resistance of aged and non-aged crowns were tested using a universal testing machine (Shimadzu AGS-X). One-way ANOVA, Tukey post hoc and independent sample t-tests were used to analyze the data and a P value < .05 was considered significant.

Results: IPS crowns without aging had the highest (2094.3 ± 399.31 N), and the GC1 crowns after aging had the lowest (1216.99 ± 302.96 N) fracture strength values. The difference of fracture strength among the same thickness samples without aging was not statistically significant (P > .05). The fracture strength of the GC1 group was significantly lower than those of the other groups (P < .05). After aging; GC group showed significantly higher fracture strength than the IPS and GC1 groups. The CD group's fracture strength was significantly higher than the GC1 group (P < .05). Aging significantly decreased the fracture strength of the IPS group (P < .05).

Conclusion: All monolithic crowns employed in this research proved to be resistant to physiological chewing forces in the anterior region.