Journal of Prosthodontics-Implant Esthetic and Reconstructive Dentistry最新文献

This dental technique describes the use of an artificial intelligence (AI)-facilitated digital workflow in the rehabilitation of an edentulous maxilla with a complete-arch implant-supported prosthesis. The patient's 2D frontal facial photograph was merged with a 3D digitized wax-rim record base in AI-supported smile design software to create an AI facially- guided virtual tooth setup without the use of a facebow transfer. The AI-generated facially driven smile design established esthetic parameters and guided the fabrication of a printed prototype, which was then used for the dual-scan CBCT protocol for the prosthetically driven planning of zygomatic and conventional implants. After osseointegration, a fully modeless workflow utilizing horizontal grammetry (Straumann EXACT, Switzerland) enabled accurate digital capture of implant positions for CAD-CAM fabrication of a titanium framework and monolithic zirconia restoration. This AI-enhanced approach streamlined the treatment visits and improved the esthetic predictability in complex edentulous rehabilitation.

Purpose: The purpose of this radiographic study was to assess the variability and probability of straight and angled screw channel access while planning immediate implant placement for maxillary anterior teeth using cone beam computed tomography (CBCT).

Materials and methods: Anterior maxillary CBCT scans of patients were reviewed for maxillary central incisors, lateral incisors, and canines. The scans were imported to implant planning software. Mid sagittal sections were identified, implants were virtually placed using established clinical criterion, and virtual straight abutments were planned on those sites. The emergence of the abutment access channels was checked, and angular corrections were incrementally made from 5 to 25 degrees till the access channels were lingual to the incisal edges. The prevalence of each angulation and degrees of angulation were then compared among the tooth types by using Fishers' Exact test.

Results: A total of 295 sites in the anterior maxilla were evaluated. The results demonstrated that the greatest percentage of straight access channels was found at canine sites (51%) and the least at lateral incisors (5.1%). There was a significant increase in access channel through the cingulum using angled screw channel systems (p < 0.01) for each tooth type. The lateral incisor required the most significant angle correction among the anterior teeth. The most frequently required angle correction was 10 degrees (18.6%) within the sample (p < 0.01).

Conclusion: The study showed that the angled screw channel systems significantly (p < 0.01) increased the prevalence of a screw-retained restoration in the anterior maxilla. Lateral incisors required the greatest amount of angle correction within the group (75.5%).

Purpose: This study evaluated the biomechanical impact of major connector designs and framework materials, polyetheretherketone (PEEK) and cobalt-chromium (CoCr), on deformation and mechanical stress distribution in the framework, periodontal ligament (PDL), and supporting mucosa through finite element analysis (FEA).

Materials and methods: Intraoral data from a patient were obtained via cone beam computed tomography and a master model scan. Two removable partial denture (RPD) designs were modeled: a lingual plate and a lingual bar. A uniform pressure was applied bilaterally, producing a force of 120 N on each side. Deformation and stress distribution were analyzed using ANSYS Workbench FEA.

Results: For PEEK frameworks, the bar design reduced deformation in the framework and mucosa compared with the plate design but produced 25% higher PDL deformation. von Mises stress within the framework increased by 24% with the bar, while PDL stress increased by 58%, and mucosal stress decreased by 84%. In CoCr frameworks, the bar design similarly reduced framework and mucosal deformation, while PDL deformation showed minimal difference (9% lower with the plate). Unlike PEEK, the CoCr bar design reduced von Mises stress across all structures by 23%-57% compared with the plate.

Conclusions: The optimal major connector design is material-specific. For PEEK RPD, a bar design may be considered for patients with metal sensitivity and strong abutment teeth. In contrast, a plate design may be indicated for cases with periodontally compromised abutments with good residual ridges. In CoCr RPD, the bar design offers superior stress distribution, whereas the plate may be reserved for cases with strong abutments and good ridge support.

Purpose: Systematic reviews are foundational to evidence-based prosthodontics, yet their conclusions may be shaped by methodological choices made during question formulation, evidence selection, analysis, and interpretation. This methodological analysis examines how directional framing of review questions, reliance on surrogate outcomes, and interpretive approaches may influence conclusions in a limited sample of eight prosthodontic systematic reviews, particularly when evidence is sparse, heterogeneous, or indirect.

Methods: Eight recent systematic reviews in prosthodontics, restorative dentistry, and implant therapy were purposively selected for methodological analysis. Each review included an explicit PICO [Patient/Problem (P), Intervention (I), Comparison (C), and Outcome (O)] or focused clinical question and relied on limited or heterogeneous evidence while offering practice-oriented interpretations. Reviews were assessed for the neutrality of question framing, handling of surrogate and clinical outcomes, management of heterogeneity, and alignment between evidence and conclusions. Directional PICOs were defined as those that framed alternatives asymmetrically or suggested expected benefit or acceptability for one option. A Cochrane review was used as a benchmark for interpretive proportionality and neutrality.

Results: All eight prosthodontic reviews exhibited patterns in which interpretation appeared influenced by question framing, evidence type, or heterogeneity. Directional PICO framing frequently aligned with similarly directional conclusions. Reviews relying on in vitro or surrogate endpoints often extrapolated laboratory findings to clinical recommendations. Other observed patterns included limited distinction between surrogate and clinical outcomes, difficulty combining findings from methodologically diverse studies, and conclusions that went beyond what the available evidence could reliably support. The Cochrane review demonstrated clear separation between evidence and inference and maintained interpretive restraint in light of evidentiary limitations.

Conclusions: Within this set of eight prosthodontic systematic reviews, directional framing, surrogate outcomes, and heterogeneous or indirect evidence appeared to influence how conclusions were formulated. Neutral framing, clear differentiation of outcomes, transparent heterogeneity management, and alignment between conclusions and evidence certainty may strengthen future prosthodontic evidence syntheses.

Purpose: This study aimed to assess the accuracy of a photogrammetry scanner and evaluate the influence of four different manufacturing materials on the accuracy and fitting of full-arch restorations made using a photogrammetry scanner.

Materials and methods: A cast with six implant abutment analogs was made. Four groups (n = 9) were created according to the material used: 3D printing resin (OnX), milled resin (PMMA), titanium (Ti), and zirconia (Zir). Nine initial scans were taken using a photogrammetry scanner, and the restorations were designed and fabricated from these digital impressions. Reverse scan bodies (MicronMapper Fit Check) were screwed to the final restorations, and scanned again using the photogrammetry scanner. Linear and angular deviations between reference and test scans were calculated using root mean square error (RMSE). Passive fit was qualitatively assessed by three independent evaluators. Data were analyzed using Kruskal-Wallis, followed by Bonferroni post-hoc correction (𝛼 = 0.05). Cohen's Kappa was used to assess the agreement on the fit of restorations.

Results: Significant differences in accuracy were found among the material groups (p < 0.05). Ti and Zir groups showed the lowest deviation values, followed by PMMA and OnX. Qualitative assessments supported the quantitative findings, with titanium and zirconia demonstrating superior passive fit. OnX showed the highest deviation and inconsistent seating and adaptation, while PMMA showed moderate results.

Conclusions: While photogrammetry provided clinically acceptable capture of implant position, the manufacturing material significantly affected the accuracy and passive fit of full-arch implant-supported restorations produced via photogrammetry-based workflows and alternative solutions should be used to validate the accurary of the manufacturing process in digital workflows. Titanium and zirconia demonstrated the best overall performance, supporting their suitability for final restorations. PMMA may be acceptable for provisional use, while 3D-printed resin showed limited reliability. When checking passive fit, all screws should be tightened simultaneously.

Purpose: To assess the adhesive bond strength of two provisional screw-retained computer-aided design and computer-aided manufacturing (CAD-CAM) crowns bonded to titanium bases (TiB) following artificial aging, tensile testing, and failure mode analysis.

Materials and methods: Ninety CAD-CAM hybrid abutment crowns (HAC) were evaluated: poly(methyl)-methacrylate ([PMMA], n = 40), polymer-infiltrated ceramic network ([PICN], n = 40), and lithium disilicate ceramic ([LS₂], n = 10, control). HACs were cemented to TiB (internal hex, 4.3 mm diameter, 4 mm height, n = 90) using two permanent resin-based cements. Artificial aging was performed via thermocycling (5000 cycles, 5°C-55°C). Tensile bond strength (TBS) was assessed, and failure mode distribution was analyzed using loupes magnification and scanning electron microscopy. Non-parametric tests were used due to non-normal data. Mann-Whitney and Kruskal-Wallis tests compared cement and crown type impact on TBS. Chi-square tests analyzed differences in failure mode and dominant cement location.

Results: All specimens withstood artificial aging. One LS₂ sample was excluded after exceeding the testing limit (>1118 N). PICN demonstrated the highest median TBS (749.8 N), significantly outperforming PMMA (p < 0.001) and LS₂ (p = 0.029, unadjusted pairwise Mann-Whitney U). Cement type was not a statistically significant factor within material groups. Mixed failure modes (79.8%) were predominant, and adhesive failures accounted for 20.2%. Cement remnants were primarily localized on the TiB surface (49.4%).

Conclusion: PICN exhibited superior bonding performance, indicating its suitability for immediate loading in implant-supported restorations. In contrast, PMMA may require modified cementation protocols to achieve optimal retention. These findings provide critical insights for material selection in prosthetic rehabilitation.

Purpose: This study evaluated film thickness, diametral tensile strength (DTS), and crown retentive strength of hydraulic fast-set calcium silicate cement (fast-set CSC) compared to conventional luting cements.

Materials and methods: Fast-set CSC was compared to zinc phosphate cement and glass ionomer cement. Film thickness was measured according to ISO 9917-1:2007. DTS was evaluated using cylindrical samples (n = 6 per group), which were kept in a humid environment for 7 days. Crown retentive strength was evaluated by cementing metal crowns onto prepared extracted molars (n = 21 per group), followed by 10,000 thermal cycling and a pull-off test. Failures were classified as adhesive, cohesive, or mixed.

Results: All cements exhibited film thicknesses below 25 µm: 10 ± 4 µm for glass ionomer, 14 ± 6 µm for zinc phosphate, and 22 ± 2 µm for fast-set CSC. Zinc phosphate cement demonstrated a statistically significant lower DTS value (4.8 ± 1.7 MPa) than glass ionomer cement (8.7 ± 3.1 MPa), while fast-set CSC (7.1 ± 0.8 MPa) showed no significant difference compared with either material. Crown retentive strength did not significantly differ among the cements (p = 0.11), with zinc phosphate cement showing the lowest value (2.7 ± 1.1 MPa), without a statistically significant difference with glass ionomer (3.6 ± 1.9 MPa) and fast-set CSC (3.5 ± 1.3 MPa). Mixed failures were predominant in all groups.

Conclusion: Fast-set CSC demonstrated acceptable film thickness with DTS and crown retentive strength comparable to zinc phosphate and glass ionomer cements, showing promise for clinical potential in crown cementation, warranting further studies.

Purpose: This in vitro study aimed to investigate the effect of different grit sizes of dental burs on the marginal adaptation of lithium-reinforced glass-ceramic restorations. The objective was to determine if finishing with fine-grit burs after initial preparation with coarser-grit burs enhances the marginal adaptation of restorations produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology.

Materials and methods: Fifty impacted human molar teeth with intact enamel were extracted and divided into five groups (n = 10 per group). For group 1, a neutral band chamfer bur (107 µm) was used, while for group 2, a black band bur (181 µm) was used. A green band bur (151 µm) was used for group 3. For group 4, preparation was done using a black band bur and finished with the red band bur (46 µm), while for group 5, a green band bur was used for preparation and finished with the red band bur. Three-dimensional (3D) scans of the prepared teeth were obtained using an intraoral scanner (Virtuo Vivo, Dental Wings), and CAD software was used to design the crowns. The restorations were milled from lithium disilicate blocks (IPS e.max CAD, Ivoclar Vivadent) on a chairside milling machine (M10, Camcube). Marginal gap assessment on the buccal, mesial, palatal/lingual, and distal surfaces by a stereomicroscope at 20× magnification and with 840 LP/mm resolution was performed. The measurements were performed for 32 equidistant points per sample, totaling 1600 points. ImageJ software was used for the analysis. Additionally, scanning electron microscopy (SEM) was used on 10 samples for validation. Statistical analysis was conducted using the Kruskal-Wallis and Mann-Whitney U tests at the 0.05 significance level.

Results: There was a statistically significant difference in marginal adaptation between the different groups, with groups 4 (Black-Red) and 5 (Green-Red) showing a better marginal fit (p < 0.05). Within each group, no significant difference was observed between the buccal, mesial, distal, and palatal sides.

Conclusion: Finishing tooth preparation with a fine-grit red diamond bur after using coarser-grit burs significantly enhances the marginal adaptation of glass-ceramic restorations produced by CAD-CAM technology. This technique could lead to better clinical outcomes in patients treated with such restorations.