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

Purpose: This in vitro study aimed to evaluate and compare the fracture resistance of zirconia mandibular molar crowns with the traditional trapezoidal (TT) shaped access and three novel conservative access designs. The designs tested were the TT, conservative trapezoidal (CT), ultraconservative circular (UC), and two conservative single accesses (TC).

Materials and methods: A mandibular right first molar typodont tooth was prepared for a full coverage zirconia crown. The preparation was scanned, and a total of 56 monolithic zirconia crowns were milled. Resin dies were printed for each restoration. Crowns were cemented with dual curing resin cement to the printed dies. The specimens were artificially aged with 10,000 thermal cycles between 5°C and 55°C with a dwell time of 30 s and were loaded to failure using a universal testing machine. Furthermore, scanning electron microscope (SEM) images were taken to evaluate the fracture patterns of the specimens. The fracture load was analyzed using the Shapiro-Wilks normality test, followed by a one-way ANOVA with a post hoc Tukey test.

Results: The fracture resistance of mandibular molar zirconia crowns significantly varied according to the endodontic access cavity design. Crowns with UC access had the highest fracture resistance (2722 ± 113 N, p < 0.001), followed by the CT (2469 ± 126 N) and the TT access (1915 ± 71 N). The two-conservative single access design had the lowest value (1064 + 129 N).

Conclusions: All endodontic access designs for mandibular molar zirconia crowns appeared to withstand the average occlusal forces. Crowns with UC access demonstrated the highest fracture resistance among different endodontic access designs. Two conservative single accesses in the same crowns significantly diminished the fracture resistance.

Purpose: Performing endodontic procedures on existing crowns is common when replacing the crown is not feasible. Traditional triangular access (TTA) is standard for maxillary molars, but more conservative designs are reported in the literature. However, research comparing the fracture resistance of maxillary molar zirconia crowns using traditional and novel endodontic access sealed with composite resin remains limited. The purpose of this in vitro study was to evaluate the fracture resistance of maxillary molar zirconia crowns with various endodontic cavity designs: traditional triangular access (TTA), conservative triangular access (CTA), and conservative circular access (CCA). A control group with no endodontic access (NEA) was also included.

Materials and methods: A maxillary right first molar typodont tooth was prepared for a full all-ceramic crown. The preparation was scanned, and 48 dies were 3D-printed based on the tooth preparation. A total of 48 zirconia crowns were fabricated (n = 12 per group) and divided into four groups according to the endodontic access cavity design: TTA, CTA, CCA, and a control group without an endodontic cavity. To ensure consistency, all restorations were designed and fabricated using a digital workflow. Endodontic access was created using a specialized bur kit and sealed using a repair kit for damaged ceramic restorations along with resin composite. The restorations were cemented, and all samples underwent artificial aging with 10,000 thermal cycles between 5°C and 55°C, with a dwell time of 30 s. The samples were then loaded to failure using a universal testing machine. The maximum load to fracture was analyzed using a one-way ANOVA and post hoc Tukey honestly significant difference (HSD) test (α = 0.001). Additionally, the fracture patterns of the specimens were evaluated descriptively using a scanning electron microscope.

Results: The mean fracture resistance of maxillary molar zirconia crowns varied significantly by endodontic access type. CCA showed the highest resistance (3677 N) among access groups, followed by CTA (3385 N) and TTA (2927 N). The control group NEA (3834 N) exhibited the highest overall resistance, exceeding all access groups.

Conclusions: Conservative access designs increased the fracture resistance of zirconia crowns compared with traditional access, with circular access showing the highest strength. However, all access preparations reduced resistance relative to crowns without endodontic access.

Purpose: This study aims to determine whether prosthetic rehabilitation affects salivary flow, pH, and comfort in patients treated for head and neck cancer (HNC) and to assess potential differences between irradiated and non-irradiated patients.

Materials and methods: This pilot clinical study focused on patients treated for HNC who require prosthetic rehabilitation. Participants were divided into two groups: irradiated and non-irradiated. Stimulated and unstimulated salivary flow, pH, and perceived comfort sensation were assessed at three time points: T0 (prior to prosthesis placement), T1 (1 month after prosthesis placement), and T6 (6 months after prosthesis placement). Outcomes were compared between the two groups across all time points.

Results: Significant differences were observed in unstimulated salivary flow between T0 and T6, while stimulated salivary flow showed significant differences between T0 and T1, T0 and T6, and T1 and T6. No significant differences were found in salivary pH or perceived comfort. However, 85% of participants reported greater comfort 6 months after prosthetic rehabilitation. Both irradiated and non-irradiated patients demonstrated improvements in salivary flow and perceived oral comfort, although no significant differences were observed between groups. A significant change in pH was detected only in the non-irradiated group.

Conclusions: The study demonstrated a significant increase in both unstimulated and stimulated salivary flow, with no significant differences between groups. Salivary pH increased significantly in the non-irradiated group compared to the irradiated one. Both groups reported improvements in perceived comfort, although no significant differences were observed between T1 and T6.

Purpose: Mandibular two-implant overdentures represent the standard of care for edentulous patients; however, long-term evidence comparing prosthetic maintenance demands among different bar attachment systems remains limited. This pilot randomized clinical study aimed to compare the 5-year prosthetic complications and maintenance profiles of bar-locator versus bar-clip attachments to inform clinical attachment selection.

Materials and methods: Sixteen completely edentulous patients were rehabilitated with new maxillary and mandibular complete dentures and received two implants placed in the mandibular canine regions. Participants were randomly allocated to either a bar-locator group (n = 8) or a bar-clip group (n = 8). Prosthetic complications, including retentive component wear, screw loosening, tooth wear, denture fracture, relining, and other maintenance events, were clinically recorded over a 5-year follow-up period.

Results: All participants completed the 5-year follow-up (100% retention). A total of 24 prosthetic complications were recorded in the bar-locator group and 13 in the bar-clip group. The mean number of complications per patient was 3.0 ± 1.3 for bar-locator and 1.6 ± 0.9 for bar-clip overdentures (absolute risk difference = +1.4; 95% CI: -0.3 to 3.0). Although the bar-locator group demonstrated numerically higher frequencies of retentive insert wear, tooth wear, and minor fractures, none of the between-group differences reached statistical significance (p > 0.05). No catastrophic mechanical failures were observed in either group.

Conclusions: Over 5 years, both bar-locator and bar-clip attachment systems demonstrated reliable mechanical performance and clinical longevity. The bar-locator system was associated with a higher overall maintenance burden. In contrast, bar-clip overdentures required relining more frequently, reflecting distinct long-term maintenance profiles rather than differences in durability. These pilot findings support the feasibility of a larger randomized trial and highlight the need for future studies incorporating patient-reported outcomes, cost-effectiveness analyses, and time-to-event assessments of prosthetic maintenance.

This technique describes a scanner-agnostic digital workflow for generating dynamic mandibular motion from static virtual interocclusal records using a custom artificial intelligence (AI) algorithm and user interface. Virtual records of mandibular positions, including maximum intercuspation, protrusion, and lateral excursions, were captured with an intraoral scanner and processed through a custom interface developed using Python, an open-source, script-based programming language. The program interpolates intermediate positions using quantified point tracking and exports a motion path file compatible with dental computer-aided design software. By leveraging AI and open-source tools, this method offers a cost-effective, non-vendor-specific solution for integrating individualized jaw motion into digital prosthodontic workflows.

Purpose: To compare the three-dimensional (3D) accuracy of digital (intraoral scanning and photogrammetry) and conventional implant impressions for complete-arch implant-supported fixed dental prostheses.

Methods: A systematic search was conducted in electronic databases using relevant MeSH keywords to identify in vitro and in vivo studies comparing the 3D accuracy of digital versus conventional implant impressions. Eligible studies were included in a meta-analysis, with subgroup analyses conducted based on implant number (≤ 4 vs. > 4), impression type (intraoral scanners vs. photogrammetry), and study design (in vitro vs. in vivo). Publication bias was assessed using funnel plots and Egger's regression test. Risk of bias was evaluated using QUIN for in vitro studies, RoB 2 for randomized trials, and ROBINS-I for non-randomized studies.

Results: A total of 37 studies were included, comprising 30 in vitro and 7 in vivo investigations, with the latter including 3 randomized clinical trials, 3 prospective studies, and 1 retrospective study. The studies assessed impression accuracy using 3D global deviation and/or coordinate measuring machine (CMM) analysis. Meta-analysis of 25 studies revealed no significant overall difference in accuracy between digital and conventional impressions (standardized mean difference [SMD]: -0.03; 95% CI: -0.20 to 0.14; p = 0.74), although substantial heterogeneity was present (I² = 68%). Subgroup analysis showed no significant difference for cases with ≤ 4 implants, while conventional methods were slightly favored in cases with > 4 implants (SMD: 0.22; 95% CI: 0.05 to 0.39; p = 0.01). Photogrammetry produced slightly greater accuracy than conventional impressions (SMD = 0.15; 95% CI 0.02 to 0.28), whereas intraoral scanners did not differ from conventional techniques. Funnel-plot asymmetry and Egger testing suggested publication bias. Certainty of evidence was judged moderate owing to methodological heterogeneity and imprecision. Descriptive findings indicated that 12 studies reported comparable accuracy between techniques, 11 favored conventional impressions, and 13 favored digital methods. One study noted implant number as a factor, with conventional methods more accurate for three implants and digital techniques superior for four or more. These results highlight both methodological variability and a lack of consensus in the current evidence.

Conclusions: Digital impressions achieve accuracy comparable to conventional impressions in most clinical situations. Accuracy may decline when scanning arches with more than 4 implants, although photogrammetry appears to mitigate this effect. Well-designed in vivo studies that use standardized scanning and evaluation protocols are needed to confirm these findings and to define clinical thresholds for adopting specific digital workflows.

Purpose: The present study was conducted to assess the cyclic fatigue resistance of implant-supported long single crowns and the effect of retention type on their mechanical behavior. The investigation aimed at evaluating failure modes and fracture resistance under conditions simulating mastication.

Materials and methods: Thirty implant-supported crowns were made, out of which 15 were screw-retained and 15 were cement-retained implant prostheses. The samples were tested on cyclic fatigue loading in a universal testing machine using physiological masticatory forces. The test method adhered to ISO 14801 guidelines, where cyclic loading at 275 N was used at a frequency of 5 Hz until failure or up to 5 million cycles. Fractographic analysis was carried out using FESEM. Statistical analysis was done using the independent t-test for fatigue resistance between groups.

Results: Screw-retained prostheses demonstrated a greater mean number of cycles to screw fracture (105,430 cycles) than cement-retained prostheses (87,039 cycles), and the difference was not statistically significant (p = 0.503). Screw-retained crowns demonstrated greater fatigue resistance at the expense of increased screw loosening. Cement-retained crowns demonstrated lower fatigue resistance but improved stability. Fractographic analysis verified fatigue fractures with characteristic failure modes between retention types.

Conclusion: Screw-retained crowns and cement-retained crowns have statistically insignificant differences in fatigue resistance. Screw-retained crowns are subject to loosening of the screw, whereas cement-retained crowns are more stable. The choice of retention type should be based on mechanical performance and clinical retrievability.

Purpose: This study evaluated the accuracy (trueness and precision) of facial scanners using different technologies and the reliability of the texture maps produced.

Materials and methods: A volunteer was scanned using nine scanners: Cloner, Artec MHT, Revopoint Mini, Revopoint POP 2, Vectra H2, EXAscan, Scaniverse app, iPhone 13 Pro MAX, and Nikon Z 7II Camera. Eighty scans were compared to a reference model (Vectra XT). Root mean square and standard deviation of the dimensional discrepancies were analyzed using ANOVA and Tukey post-hoc test. Acquisition times were assessed using Kruskal-Wallis test followed by Mann-Whitney U-test. Two expert assessments on texture map realism were averaged and compared to the reference using one sample t-test. The two experts' intraclass correlation coefficient (ICC) was calculated.

Results: Eight scanners fully captured the three-dimensional facial geometry. Overall trueness and precision of the facial scanners were significantly different (p < 0.001). Seven scanners showed clinically acceptable scanning accuracy of less than or equal to 2 mm. Cloner displayed the lowest deviation (0.61 ± 0.08 mm), fastest acquisition time (0.40 ± 0.00 s), and was highly reliable (<1 mm). The texture map of the Vectra H2 had the highest mean score of 8.50 and was the most realistic. The ICC between the experts was 0.78 indicating good interexaminer reliability.

Conclusions: The more economical facial scanners within each scanning technology (iPhone 13 Pro MAX, Cloner, Revopoint MINI, and Scaniverse app) showed clinically acceptable accuracy with realistic texture maps for facial scanning and therefore could be eligible substitutes for professional higher-cost scanners.

This digital clinical report presents a novel CAD-CAM workflow for fabricating a customized monolithic zirconia post-and-core restoration. A 26-year-old female patient required prosthetic rehabilitation of the maxillary left first and second premolars, as well as an implant screw-retained crown (ISRC) for the maxillary left first molar. After post space preparation, intraoral scans (IOS) were obtained both with and without a prefabricated fiber post in place. The fiber post was also scanned separately using a desktop scanner. These datasets were superimposed using digital software to design a precise monolithic zirconia post-and-core, which was then milled using CAD-CAM technology. The structure was cemented with self-adhesive resin cement, and a lithium disilicate crown was digitally designed and fabricated. This digital approach minimized the errors associated with conventional techniques, improved fit and adaptation, and enhanced clinical efficiency. The definitive restoration achieved excellent aesthetic and functional outcomes, fulfilling the patient's expectations without complications. This report highlights the value of digital workflows in achieving precision and predictability in post-and-core restorations.