Journal of Prosthetic Dentistry最新文献

Statement of problem: Considerable variations exist in cavity preparation methods and approaches. Whether the extent and depth of cavity preparation because of the extent of caries affects the overall accuracy of training deep learning models remains unexplored.

Purpose: The purpose of this study was to investigate the difference in 3-dimensionsal (3D) model cavity preparations after International Caries Detection and Assessment System (ICDAS) classification performed by different practitioners and the subsequent influence on the ability of a deep learning model to predict cavity classification.

Material and methods: Two operators prepared 56 restorative cavities on simulated mandibular first molars according to 4 ICDAS classifications, followed by 3D scanning and computer-aided design processing. The surface area, virtual volume, Hausdorff distance (HD), and Dice Similarity Coefficients were computed. Multivariate analysis of variance was used to assess cavity size and operator proficiency interactions, and 1-way ANOVA was used to evaluate HD differences across 4 cavity classifications (α=.05). The 3D convolutional neural network (CNN) predicted the ICDAS class, and Saliency Maps explained the decisions of the models.

Results: Operator 1 exhibited a cavity preparation surface area of 360.55 ±15.39 mm², and operator 2 recorded 355.24 ±10.79 mm². Volumetric differences showed operator 1 with 440.41 ±35.29 mm³ and operator 2 with 441.01 ±35.37 mm³. Significant interactions (F=2.31, P=.01) between cavity size and operator proficiency were observed. A minimal 0.13 ±0.097 mm variation was noted in overlapping preparations by the 2 operators. The 3D CNN model achieved an accuracy of 94.44% in classifying the ICDAS classes with a 66.67% accuracy when differentiating cavities prepared by the 2 operators.

Conclusions: Operator performance discrepancies were evident in the occlusal cavity floor, primarily due to varying cavity depths. Deep learning effectively classified cavity depths from 3D intraoral scans and was less affected by preparation quality or operator skills.

Statement of problem: The use of additive manufacturing Ti-6Al-4V (AM Ti64) in removable partial denture (RPD) frameworks has become increasingly prevalent in clinical practice. However, the elastic and fatigue properties of AM Ti64 clasps are not well understood.

Purpose: The purpose of this in vitro study was to investigate the elastic and fatigue properties of AM Ti64 clasps by comparing them with milled Ti64 (Milled TC4) clasps.

Material and methods: Dumbbell specimens of AM Ti64 and Milled TC4 were prepared for tensile tests following the International Organization for Standardization (ISO) 22674 standard (n=6). Raw (R) and mechanically polished (P) clasp-shaped specimens were prepared for elastic and fatigue tests and divided into 4 groups: AM Ti64R, AM Ti64P, Milled TC4R, and Milled TC4P. The clasp intaglio surface roughness was measured before testing (n=10). The elastic deformation limit (EDL) of the clasp was determined through incremental displacement loading (n=10). Fatigue tests were conducted on 160 clasps (40 specimens per group) at displacements from 0.30 mm to 1.00 mm for 10⁵ cycles (n=5 per displacement). The fracture surfaces of failed clasps were observed using a scanning electron microscope (SEM), and the microstructures were analyzed using optical microscopy. Statistical analyses were conducted using t tests and Kruskal-Wallis tests (α=.05).

Results: AM Ti64 exhibited higher 0.2% offset yield strength and ultimate tensile strength than Milled TC4 (P<.001), with no significant difference in percentage elongation (P=.298) or elastic modulus (P=.151). No significant differences in intaglio surface roughness were found between AM Ti64 and Milled TC4 clasps in both the raw (P=.306) and polished (P>.999) groups. AM Ti64 clasps demonstrated greater EDL values than Milled TC4 clasps in both the raw and polished groups (P<.001). The fatigue life of AM Ti64 clasps was significantly shorter than that of Milled TC4 clasps (P<.001), with no significant difference between the raw and polished groups in both AM Ti64 (P=.611) and Milled TC4 clasps (P>.999). SEM observation revealed fatigue cracks originating from surface defects in AM Ti64 clasps. Microstructural analysis showed lamellar α phase dominance in AM Ti64, while Milled TC4 exhibited primarily equiaxed α phase.

Conclusions: The AM Ti64 clasp showed better elasticity but inferior fatigue performance compared with Milled TC4 clasps. Mechanical polishing did not significantly affect the elasticity or fatigue properties of the titanium clasp.

Statement of problem: Digital scans for single crowns have been reported to achieve accuracy similar to that of traditional impressions in certain patients, but criteria for acquiring high-quality scans are lacking.

Purpose: The purpose of this in vitro study was to determine the optimal gingival displacement widths, finish line depths, and preparation designs for single crowns when using intraoral scanners (IOSs) to achieve clinically acceptable and high-quality recordings.

Material and methods: Three different preparation designs of computer-aided design and computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA) abutments (round shoulder, shoulder, and sloped shoulder) were fitted with titanium sleeves of 4 different thicknesses (0.2 mm, 0.3 mm, 0.4 mm, and 0.5 mm) and magnetically attracted onto the spindle of an electronic spiral micrometer. Occlusal registration material was injected around the abutment to simulate gingival tissue. After setting, the titanium sleeves were removed to create gaps as different gingival displacement widths. The spiral micrometer was rotated to create 5 different finish line depths (supragingival 0.5 mm, equal gingiva, subgingival 0.5 mm, subgingival 1.0 mm, and subgingival 1.5 mm). Two IOSs (CEREC Primescan [PS] and TRIOS 3 [TS]) were used to scan 3 preparation designs with a combination of 4 gingival displacement widths and 5 finish line depths 5 times each (N=600). The files were imported into an engineering software program and superimposed with the corresponding reference scanned files of the original abutments. Tangent distances (TD) and marginal angle differences (MAD) between the testing groups and references were measured and analyzed using the Kolmogorov-Smirnov, Kruskal-Wallis, and Jonckheere-Terpstra tests (α=.05).

Results: A significant linear trend of decreasing TD and MAD with increasing gingival displacement widths and shallower finish line depths was found. Statistically significant differences (P<.05) were found in TD and MAD between different preparation designs at finish line depths that were equigingival and 0.5-mm subgingival.

Conclusions: Clinically acceptable scans generally required a gingival displacement width of at least 0.3 mm and a finish line depth within subgingival 1.0 mm. Both IOSs produced high-quality scans for supragingival finish lines. Both IOSs required at least 0.4-mm gingival displacement width to achieve high-quality scans under equal gingival conditions. Only PS with at least 0.4-mm gingival displacement width was able to achieve high-quality scans for subgingival margins. The accuracy ranking of preparation designs was round shoulder (highest), shoulder, and sloped shoulder (lowest).

Statement of problem: Advanced additive manufacturing (AM) of zirconia is an emerging technology that can explore the limitations of traditional computer-aided design and computer-aided manufacturing (CAD-CAM) milling techniques. However, a comprehensive evaluation of their differences in producing zirconia restorations, especially multi-unit restorations, is lacking.

Purpose: The purpose of this in vitro study was to compare the accuracy, fit, marginal quality, and surface roughness of zirconia 3-unit fixed dental prostheses (FDPs) by using advanced AM and 2 CAD-CAM milling materials.

Material and methods: Based on the same CAD model, 30 3-unit posterior FDPs (n=10) were manufactured by using AM and 2 CAD-CAM milling materials (VT and UP). The accuracies of the total, intaglio, occlusal, axial, and marginal regions were calculated separately by comparing the scanned model with the design model by using 3-dimensional (3D) deviation analysis. The silicone layer was scanned to evaluate the marginal and intaglio fit in 3 dimensions. A 3D laser microscope was used for surface roughness detection, marginal quality assessment, and marginal defect measurement. The data were analyzed using ANOVA and the Tukey post hoc test (α=.05).

Results: Compared with CAD-CAM milling, the AM group had higher accuracy and smaller positive deviations on the axial and intaglio regions (P<.001). Different manufacturing methods showed no statistically significant effect on the mean intaglio fit (P>.05), and all were within the clinically acceptable range (<100 µm). The intaglio gap was significantly higher than the target parameter in the occlusal regions. AM-fabricated FDPs had significantly higher surface roughness than milled ones, yet showed better margin quality with fewer marginal defects CONCLUSIONS: Compared with CAD-CAM milling, the advanced additively manufactured zirconia 3-unit FDPs provided better accuracy, improved margin quality, and clinically acceptable fit, but higher surface roughness, and may be a promising alternative for clinical applications.

Statement of problem: The mastication ability of the elderly greatly affects their health-related quality of life. However, studies investigating the impact of peri-oral muscular strength on the performance of mastication in older adults are lacking.

Purpose: The purpose of this cross-sectional clinical study in older adults was to formulate an equation relating to the mastication pattern and tongue pressure to estimate the correlation between tongue pressure and habitual mastication patterns, including mastication strokes and mastication time.

Material and methods: A total of 98 healthy adults over 65 years old who were independent in daily activities and had no swallowing difficulties were enrolled. Tongue pressure was measured with the Iowa Oral Performance Instrument (IOPI), which assesses pressure generated by squeezing a bulb between the tongue and palate. The mastication pattern was evaluated by counting strokes and measuring the time required to consume a cornstarch cookie. Statistical analysis used linear regression (α=.05).

Results: The sample included 48 women and 50 men with an average age of 71.7 years. Tongue pressure demonstrated a significant correlation with both mastication time and mastication strokes (P=.03 and.04, respectively). The findings led to a linear regression model linking tongue pressure (x) to mastication time (y₁) and mastication strokes (y₂), expressed as y₁=-0.2976x + 33.907 and y₂=-0.4134x + 45.624.

Conclusions: In older adults, a correlation was found between tongue pressure and both mastication time and mastication strokes. Based on this correlation, measuring tongue pressure might provide insight into mastication patterns, while estimating mastication time and mastication strokes could help gauge tongue strength in an aging population. Mastication ability could then be assessed and appropriate food textures chosen for elderly individuals. This formula could also help determine the optimal tongue pressure value for enhancing the mastication pattern by serving as a guide for tongue training or rehabilitation initiatives.

Statement of problem: Thiourethane has high chemical affinity with polymeric materials and its addition has been suggested for improving adhesives and composite resin. However, a systematic review of thiourethane addition is lacking.

Purpose: The purpose of this systematic review was to analyze the articles in the dental literature that studied the effect of thiourethane added to the resin matrix of dental materials related to polymerization shrinkage and mechanical properties.

Material and methods: The systematic review was prepared in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines and was registered in the Open Science Framework (osf.io/sb9my). The population, intervention, comparison, outcome, and study design (PICOS) were the following: composite resin, thiourethane addition, composite resin without addition, evaluation of polymerization and mechanical properties, and in vitro experimental studies. Initially, 204 articles were found, 150 of which were excluded because of duplication. After reading the titles and abstracts based on the application of eligibility criteria, 21 articles were selected for reading in full, and all were included in the systematic review. Three reviewers evaluated the articles independently in 2 phases based on the eligibility criteria (selection of the title and reading of the article in full), with the reviewers' doubts and discrepancies being analyzed and resolved in a meeting with the authors.

Results: Most of the articles reported a significant improvement in the polymerization shrinkage and mechanical properties of experimental polymeric materials with the addition of oligomers.

Conclusions: Thiourethane added to resin dental materials improved their polymerization shrinkage values and mechanical properties.

Statement of problem: The outcome of posterior nonvital teeth depends not only on endodontic factors but also on the effectiveness of the restoration. The growing trend in minimally invasive dentistry has led to increasing interest in 1-piece endodontic crowns as an alternative restoration. Nevertheless, their indications and longevity lack extensive exploration, thereby limiting their widespread acceptance in dental practice.

Purpose: The purpose of this overview was to synthesize the available evidence from systematic reviews (SRs) about 1-piece endodontic crowns and to identify clinical outcomes such as survival, success rates, and patient-reported outcome measures (PROMs).

Material and methods: A systematic search was performed in the electronic databases MEDLINE/PubMed, Cochrane, Web of Science, and OpenGrey, as well as a manual search, up to June 2024, with no language or time restriction. SRs that addressed clinical studies related to 1-piece endodontic crowns or endocrowns were included. The risk of bias and methodological quality was measured using the ROBIS and AMSTAR-2 tools, respectively.

Results: The search identified 468 articles, of which 9 SRs were included. The best evidence reported in the SRs was that survival or success rates for ceramic and indirect resin 1-piece endodontic crowns were high at 5 years, similar to those for conventional crowns. Loss of retention was the main cause of failure with similar failure rates for molars and premolars. Evidence for the use of zirconia and metal 1-piece endodontic crowns is limited, and no SR was found that addressed PROMs. Methodological quality was considered low or critically low in most SRs. However, the risk of bias was low for 2 of the 3 SRs that provided the best evidence in the meta-analysis for ceramic and indirect resin 1-piece endodontic crowns. Overlap in the included studies was very high.

Conclusions: Although the evidence generated by multiple RS only determined that ceramic and indirect resin 1-piece endodontic crowns can be a suitable and reliable option for restoring endodontically treated premolars and molars, with high success and survival rates comparable with those of complete crowns with posts, this overview concluded that it was not possible to provide firm conclusions regarding the outcomes of 1-piece endodontic crowns because of the lack of adequate high-quality primary studies with different materials, heterogenicity of the studies, variations in follow-up, preparation, and operative steps, and very high overlap of studies. Thus, additional well-designed clinical trials are necessary rather than SRs to strengthen the evidence in this area.

Statement of problem: Despite the increasing number of publications on applying artificial intelligence (AI) in the dental field, clarity regarding the performance of different approaches for nasoalveolar molding (NAM) planning and designing is lacking. Additionally, the overall robustness of the evidence in this field remains uncertain.

Purpose: The purpose of this systematic review was to evaluate the role of AI in automating the prediction of anatomic landmarks and the design of NAM appliances.

Material and methods: A comprehensive literature search was conducted in major databases up to April 2024 without language restrictions. Studies applying AI algorithms for NAM landmark detection or appliance design were included. Data on study characteristics, AI methods, outcomes, and limitations were extracted.

Results: Six studies met the eligibility criteria. AI algorithms demonstrated high accuracy in automatically detecting landmarks and designing NAM appliances. Approaches ranged from fully automated to semi-automated workflows. Most studies reported significant time savings compared with manual methods.

Conclusions: AI applications in NAM demonstrate substantial potential in improving workflow design, as demonstrated by the high accuracy reported in various studies. The incorporation of AI in NAM planning leads to a significant reduction in treatment appointment times when compared with conventional manual methods, thereby potentially decreasing the overall duration of treatment. Nevertheless, additional research is required to foster better collaboration between dental professionals and AI experts, ultimately facilitating more efficient clinical integration.