Journal of Advanced Prosthodontics最新文献

Purpose: The aim of the present study was to evaluate whether the accuracy of digital definitive implant casts is affected by both the process of best fit (BF) alignment of the scan bodies (SBs) with the CAD library and the type of scanner used.

Materials and methods: Scans of the upper and lower arches of a totally edentulous patient, each with eight implants, were performed using the Trios-3 (T) and True-Definition (TD) intraoral scanners and the Identica-Light extraoral scanner (EO) for casts. Two types of alignment of the SB with the CAD implant library were performed, using either 3/3 or 1/3 of its mesh. Twelve virtual definitive implant casts were generated, each with a designed prosthetic bar. Analysis included absolute differences in 28 inter-implant distances and 7 relative angles of the bar implant abutments.

Results: Descriptive statistical analysis was carried out, including the calculation of means ± standard deviations and maximum and minimum values for both distances and angles.

Conclusion: In conclusion, the accuracy of digital definitive casts with multiple implants was influenced by both the amount of mesh selected in the SBs during the BF alignment with the CAD library and the optical impression system used.

Purpose: This study aimed to compare the marginal adaptation and fracture strength of monolayered and multilayered monolithic zirconia crowns fabricated at three distinct milling depths.

Materials and methods: Eighty-four epoxy resin dies of prepared premolars were fabricated. Crowns were designed in software and milled from two monolayered zirconia materials [3Y-TZP (VITA YZ HT)(3-VYZ) and 4Y-TZP (Priti^®multidisc ZrO₂ Extra Translucent)(4-ET)], three multilayered zirconia materials [3/5Y-TZP (IPS e.max ZirCAD Prime)(3/5-ZP), 4/5Y-TZP (IPS e.max ZirCAD Prime Esthetic)(4/5-ZPE), and 4/5Y-TZP (Priti^®multidisc ZrO₂ Multi Translucent Plus)(4/5-MTP)], at three milling depths [above (A), center (C), below (B)], and a zirconia-reinforced lithium silicate glass ceramic block (VITA Suprinity)(VS) (n = 7). After sintering and glazing, marginal gaps (MG) were measured using silicone replica technique. Crowns were cemented with dualcure resin (SpeedCEM Plus, Ivoclar Vivadent), subjected to 5000 thermal cycles. Fracture strength (FS) test was performed perpendicularly to occlusal surface at 1 mm/min. Data were analyzed (SPSS 26, one-way ANOVA, Tukey post-hoc tests, P = .05), and fracture types were classified. SEM analysis was performed on representative specimens.

Results: MG differences among groups were insignificant (P > .05). The highest FS values were observed in 3-VYZ (1587.14 ± 228.26 N), 3/5ZP-B (1537.28 ± 268.81 N), and 4-ET (1364.86 ± 196.98 N) (P > .05). The lowest FS values were found in VS (483.86 ± 47.10 N)(P > .05). B-positioned multilayered crowns exhibited numerically higher FS than A or C positions.

Conclusion: Monolayered (3Y-TZP and 4Y-TZP) or multilayered 3/5Y-TZP zirconia milled from below layer may be preferred for posterior region, whereas multilayered 3/5Y-TZP milled from upper layer and all configurations of multilayered 4/5Y-TZP may be more suitable for anterior.

Purpose: The aim of the present study was to assess the influence of various implant angulations, camera positions and number of implant references on the accuracy of a photogrammetry device for complete arch implant prostheses.

Materials and methods: 2 edentulous models, one with 6 parallel implants (PM) and other with 6 angled implants (AM), underwent digitalization with a coordinate measuring machine (CMM) to establish a reference standard. Both models underwent 20 impressions with 2 different camera positions and 3 different implant references, with a total of 240 impressions. Euclidean linear and angular measurements were obtained on the reference cast and each experimental scan and compared. Absolute (n) and relative frequencies (%) of true and precise measurements at 95% confidence intervals (CI) were calculated. Chi-squared tests were used to assess differences in trueness and precision between these factors.

Results: 3660 distances and 1440 angles were analyzed for trueness. The absolute difference was 54 ± 46 µm and 0.341 ± 0.301°. Precision was 18 ± 23 µm from 68400 measured distances and 0.048 ± 0.074° for the 22800 angulations measured. Statistically significant differences (P < .05) were identified between PM and Am, A1 and A2 and number of references in both distances and angulations for trueness and precision.

Conclusion: Implant angulations, camera positions and number of implant references used affected the precision and trueness of Precise Implant Capture (PIC) system. However, these differences did not show clinically relevant values.

Purpose: This study aimed to assess the osseointegration effects of niobia-modified yttria-stabilized tetragonal zirconia ((Y,Nb)-TZP) implants, compared to titanium implants and 3 mol% yttria-stabilized tetragonal zirconia (3Y-TZP) implants in a rabbit tibia model.

Materials and methods: Sandblasted (Y,Nb)-TZP implants (YNb), sandblasted and acid-etched titanium implants (SLA), and smooth-surface 3D-printed 3Y-TZP implants (3Y) were prepared. Surface characteristics of the specimens were evaluated using scanning electron microscopy and confocal laser scanning microscopy. Implants were inserted into the tibiae of 16 rabbits, with eight rabbits euthanized at each time point (2 and 6 weeks). To estimate periodic bone remodeling, tetracycline and xylenol orange were administered to the rabbits euthanized at 6 weeks. Undecalcified specimens were prepared to measure the periodic bone remodeling ratio (PBR), bone-to-implant contact (BIC) and bone area (BA). Data analysis was conducted using one-way ANOVA with Bonferroni post hoc analysis and the Wilcoxon signed-rank test at a significance level of 0.05.

Results: At both the 2-week and 6-week intervals, YNb group exhibited significantly higher BIC values than the SLA and 3Y groups. No significant differences (P > .05) were found in PBR and BA across all comparisons.

Conclusion: Sandblasted (Y,Nb)-TZP implants indicated superior osseointegration in comparison to SLA titanium and smooth-surface 3D-printed 3Y-TZP implants. The enhanced osseointegration observed in this study supports the clinical potential of (Y,Nb)-TZP as a next-generation zirconia implant material.

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.