Journal of Advanced Prosthodontics最新文献

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: 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: 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 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.

Purpose: Titanium implants are widely used to replace pathological joints, bones, and teeth, with successful engraftment requiring osteoblast attachment to the metal surface for bone regeneration. However, the immune response at the bone-implant interface remains unclear, and few studies have examined why titanium elicits a reduced foreign-body reaction (FBR) compared to other metals. This study aimed to elucidate the mechanism underlying titanium biocompatibility by characterizing the immune response at the bone-implant interface in a rat model.

Materials and methods: Copper, machined titanium, and sandblasted/acid-etched titanium rods were fabricated for implantation into rat tibiae. Topographical and chemical features of each rod surface were evaluated. Rods were inserted into rat tibiae, and immune cell subtypes were analyzed by flow cytometry, histomorphometry, and immunohistochemistry. Statistical analyses were performed at a significance level of 0.05.

Results: Flow cytometry of bone marrow cells collected on Days 1, 7, and 35 post-implantation revealed recruitment of macrophages and neutrophils at all implant sites. Histological analysis confirmed immune cell infiltration at the metal-bone interface, with a pronounced FBR surrounding copper rods. Immunohistochemistry demonstrated an abundance of osteoclast-like M1 macrophages at the copper-implant interface. In contrast, M1 macrophages were absent near titanium implants, where reparative M2 macrophages were present.

Conclusion: The recruitment of M1 macrophages at the copper implantation site, but not at the titanium implant, indicates the FBR to copper and underlies the biocompatibility of titanium. Titanium may affect the differentiation of intrabony macrophages to increase its biocompatibility.

Purpose: This study evaluated how implant scan body (ISB) design affects trueness and operator convenience of digital implant impressions. The null hypothesis stated no significant differences in trueness or usability between ISB designs.

Materials and methods: A cast metal model with nine implants and silicone mucosal masks (1 mm and 3 mm thickness) were used. Seven ISB prototypes were developed by modifying a commercial ISB (ELOS Accurate IO2A-B, ELOS Medtech) in four aspects: length (30% shorter and 50% longer), material (polyetheretherketone (PEEK) or titanium), surface reflectance (polished or aluminium oxide-blasted titanium), and top surface (concave top and screw holes enlarged by 100% and 200%). Each prototype was scanned ten times using an intraoral scanner (NeoScan1000, Neoss), with a desktop scanner (E3, 3Shape) providing reference scans. Deviations in depth, angulation, and rotation were analyzed in CAD software (GOM Inspect, Zeiss). Statistical analysis included the Welch test (P < .05) and Games-Howell post hoc test (P < .007).

Results: Material affected depth accuracy; blasted titanium (89 ± 86 µm) and polished titanium (80 ± 72 µm) outperformed PEEK (149 ± 131 µm). Shorter ISBs showed greater angular deviations (0.64 ± 0.70°) compared to control (0.31 ± 0.21°). Rotational deviations were not significant. Scanning times increased for reflective, longer ISBs with reduced top areas, while shorter ISBs improved usability.

Conclusion: ISB design influences digital impression accuracy. Titanium ISBs with reduced reflectivity improve trueness, and larger screw holes enhance usability. Shorter ISBs reduce scanning time but compromise angular trueness. Stitching errors remain the primary source of depth inaccuracies.

Purpose: This diagnostic study evaluated the accuracy and time efficiency of digital surveying compared to the conventional method for partially edentulous arches.

Materials and methods: Thirty Standard Tesselation Language (STL) files of partially edentulous arches were analyzed. Conventional surveying was performed on 3D-printed diagnostic casts, while digital surveying was conducted using CAD software (Dental Wings Inc., Straumann, Montreal, Canada). The path of insertion and removal, and determining factors (guiding planes, undercut areas, and reciprocation) were assessed. Sensitivity and specificity tests were used to measure accuracy. Sensitivity was defined as the proportion of true positives identified by both techniques, while specificity was measured as a percentage of true negatives compared with the conventional method. Accuracy was assessed as the ability to correctly differentiate true positives and negatives. The paired t-test (95% CI) compared the mean working time between the techniques.

Results: Agreement on reciprocation was 2.91 times higher in regions with a greater number of edentulous areas compared to those with fewer edentulous areas (P = .025). The agreement of guiding planes in tooth-supported abutments was 2.59 times greater than in distal extension cases (P = .031). Accuracy ranged from 0.73 to 0.85. The working time was significantly longer for the digital technique (P = .030).

Conclusion: Both techniques demonstrated high levels of agreement, especially for reciprocation and guiding planes. The digital method exhibited accuracy ranging from good to very good; however, it required a longer working time compared to the conventional approach.