Journal of Advanced Prosthodontics最新文献

Purpose: This study examines the potential of computer-aided design (CAD) systems equipped with artificial intelligence (AI) in reducing the workload of dental technicians. We aimed to compare the accuracy and design time of crowns designed using conventional CAD with those designed using AI-equipped CAD.

Materials and methods: Abutment tooth models of a maxillary right second premolar (FDI classification #15) and a maxillary left first molar (FDI classification #26) were mounted on a dental model to form the master model. Stereolithography data were acquired using an intraoral scanner, and five dental technicians designed one crown each for #15 and #26 using both conventional and AI-equipped CAD systems. With the #15 and #26 crowns, six measuring points were established for comparing the accuracy of the occlusal surfaces and design time of the crowns designed by the two CAD systems. The occlusal surfaces were also compared for the buccal and palatal sides.

Results: The accuracy of the occlusal surface was 275.5 ± 116.8 µm and 25.7 ± 13 µm for the conventional CAD and AI-equipped CAD systems, respectively. For the buccal and palatal surface comparisons, the conventional CAD system revealed larger misfits on the palatal side for both #15 and #26, with significant differences observed. No significant differences were noted with the AI-equipped CAD system. The AI-equipped CAD resulted in significantly faster design time for both #15 and #26.

Conclusion: The AI-based CAD system significantly reduced design time and enabled the fabrication of uniform crowns regardless of the dental technician's experience and skill.

Purpose: The purpose of this clinical study was to evaluate the extent of intraoral occlusal adjustment required for zirconia crowns designed with a dynamic jaw motion tracking method compared to a conventional approach.

Materials and methods: Fifteen patients needing zirconia crown restorations in the anterior or posterior regions participated in this study. Following tooth preparation, dynamic jaw motion tracking records were gathered using a tracking device. These records were imported into computer-aided design software and aligned with scanned upper and lower jaw data to design each crown's occlusal surface. Two crowns were fabricated for each patient: one using motion tracking data and another without it. Crowns were scanned pre- and post-adjustment following standard protocols. The scanned data were analyzed with 3D inspection software to calculate occlusal adjustments in the segmented occlusal area as root mean square values, with a paired t-test used for statistical analysis (α = 0.05).

Results: Crowns designed with motion tracking data required significantly less intraoral occlusal adjustment than those designed conventionally (P = .028).

Conclusion: Dynamic jaw motion tracking in crown design reduces the extent of intraoral occlusal adjustment, potentially enhancing clinical efficiency.

Purpose: Three-dimensional (3D) printing must go through a post-processing procedure. This study aimed to evaluate the effects of different cleaning methods on 3D printed three-unit fixed partial dentures using 3D analysis.

Materials and methods: A three-unit fixed partial denture was designed and printed using two different printers. The evaluation was taken regarding cleaning method with ethanol (ETH) or isopropanol (IPA), and combining ultrasonic (US) technique for the following groups: group 1, ETH; group 2, ETH+US; group 3, IPA; group 4, IPA+US; and group 5, US. The 3D evaluation was conducted by calculating the mean distance between two specific points and analyzing various angular deviations, utilizing the geometry-embedded library. In addition, visual analysis was performed by creating sectional planes in different points of view. Normality test and independent t-test were performed to compare results between the two printers used in this study. In addition, one-way ANOVA was performed to compare cleaning method groups.

Results: Mean distance results showed statistical differences between printers for groups IPA, US, and IPA+US, whereas no significant differences were found among cleaning methods. Angular measurements were taken at the bucco-lingual, proximal, and occlusal planes to assess deviations in the internal surfaces. Overall results showed a tendency of shrinkage of the printed three-unit fixed partial denture.

Conclusion: Ultrasonic treatment may impact the washing efficiency when used with other cleaning solutions regarding angular and longitudinal deformation. Adequate selection of post-processing methods is crucial to decrease morphological deformities in 3D printed materials.

Purpose: This study aimed to evaluate the accuracy of the ultrasonic jaw tracking system by comparing with the conventional electronic system in recording condylar movements.

Materials and methods: Twenty-six subjects with normal occlusion participated in the study. The CADIAX^® 4 and Jaw Motion Analyzer (JMA) systems were used to record condylar movement trajectories during mandibular border movements (protrusive/retrusive, lateral, and wide mouth opening), with each movement repeated three times. Both systems used facebows and sensors to locate the condylar axis points and capture movement trajectory data. Paired t-tests were used for normally distributed data, while the Wilcoxon rank-sum test was applied to non-normally distributed data. The level of significance was set at α = .05.

Results: The maximum condylar displacement in the sagittal plane during mandibular border movements and the sagittal condylar inclination (SCI) values on both the left and right sides showed no significant difference between the two systems (P > .05). The Bennett angle (BA) values on both the left and right sides measured by the JMA system were significantly higher than those measured by the CADIAX^® 4 system (P < .05). The comfort levels of the JMA system were significantly higher than the CADIAX^® 4 system (P < .05).

Conclusion: Through this study, it was found that the accuracy of the ultrasonic jaw tracking system was comparable with the conventional electronic system, except for the Bennett angle measurement. In terms of comfort and ease of use, the ultrasonic jaw tracking system is more favored.

Purpose: This study aimed to evaluate the accuracy of static computer-assisted implant surgery (s-CAIS) by comparing the planned and actual positions of implants placed in a partially edentulous model using surgical templates with different sleeve designs.

Materials and methods: Forty-nine mandibular partially edentulous models were scanned using a model scanner to create standard tessellation language (STL) files. The models were divided into seven groups based on sleeve design: Group 1-4 (Open non-metal sleeves with varying heights (3 mm, 6 mm) and buccal widths (5 mm, 6 mm)), Group 5-6 (Closed non-metal sleeves with heights of 3 mm and 6 mm), and Group 7 (Closed metal sleeve). After implant placement at #45 and #47, STL files were generated and analyzed using 3D measurement software. Deviations were measured in terms of horizontal deviation (coronal and apical), vertical deviation, and angular deviation. Statistical significance was evaluated using the Wilcoxon rank sum test, Kruskal-Wallis test, and multiple generalized linear models.

Results: While height differences showed no significant deviations (P > .05), there was a tendency for larger apical deviation with increased sleeve height (P < .1). Closed metal and closed non-metal sleeves showed smaller deviations compared to open non-metal sleeves, except in vertical deviation.

Conclusion: Closed sleeves demonstrated greater accuracy in s-CAIS compared to open sleeves. Higher sleeves may improve implant placement accuracy, but buccal insertion width did not significantly affect accuracy.

Purpose: This study assessed the microgap width and adhesion of three bacterial species in four dental implants with different interlocks under four screwing torques.

Materials and methods: Ten samples of four implant systems with various interlockings, including full-hexagonal (FHI), cylindrical-conical trilobe-index (TLI), Morse-taper with octagon terminal index (OI), and hexagonal interlock (slip-fit) (HI-SF), were used. The abutments were screwed to the fixtures under torques of 10, 20, 30, and 40 Ncm. The microgap between the abutment and the platform was assessed using a Scanning Electron Microscope (SEM). The leakage of 3 bacteria, including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, was evaluated under 30 Ncm torque.

Results: The TLI system showed the widest gap under all torques compared to others. There was no significance among all systems under different screwing torques. Regarding the leakage, there was no adherence to E. coli and S. aureus and 36.4% of Ps. aeruginosa to the HI-SF, followed by the OI system. The FHI and TLI systems showed the highest bacterial adherence.

Conclusion: Even with low torque, the studied systems showed gap widths narrower than acceptable width. Implant systems with FHI and OI demonstrated misfits of less than 2 µm upon 10 Ncm and less than 1 µm when the torque increases, giving them priority to be used in areas with poor bone quality. The HI-SF demonstrated a high ability to resist the adherence to E. coli and S. aureus, followed by OI. However, Ps. aeruginosa demonstrated a high ability to adhere to all systems.

Purpose: This pilot study investigated the effect of surface roughness on osseointegration by comparing two types of commercial SLA-treated dental implants with different surface roughness levels: moderately rough (S_a = 1 - 2 µm) and rough surfaces (S_a > 2 µm).

Materials and methods: Two implant groups were studied: TS (rough surface) and ADD (moderately rough surface) groups. Surface characteristics were analyzed using optical profilometry and SEM. In vitro studies using BRITER cells assessed cell adhesion, proliferation, and osteogenic differentiation through CCK-8 assay and qRT-PCR for osteopontin (OPN), osteocalcin (OCN), and alkaline phosphatase (ALP) expression. The in vivo study involved 12 implants (six per group) placed in mandibular defects of two beagle dogs. After 8 weeks, histomorphometric analysis evaluated bone to implant contact (BIC) and inter-thread bone density (ITBD). Statistical analysis used Student's t-test and two-way ANOVA for in vitro data, and Mann-Whitney U test for in vivo data.

Results: Surface analysis revealed S_a values of 2.50 ± 0.27 µm for the TS group and 1.80 ± 0.06 µm for the ADD group. In vitro studies showed no significant differences in cell adhesion and proliferation between the groups (P > .05). However, gene expression patterns differed, with ADD group showing higher OPN expression (P < .001) and TS group showing higher ALP expression (P < .01). The in vivo study revealed no statistically significant differences in BIC and ITBD between the two groups (P > .05).

Conclusion: Surface roughness influenced osteoblast differentiation in vitro, but did not significantly affect osseointegration outcomes in vivo. Both moderately rough and rough surfaces appeared to support comparable levels of osseointegration. Larger studies are needed to confirm these findings and determine optimal implant surface characteristics.

Under-occlusion ('infraocclusion' as defined in the natural teeth) after implant restoration in the posterior area is commonly encountered in clinical practice; however, it has rarely been reported. Most importantly, the under-occlusion change mechanism remains unknown. The purpose of this case report was to analyze how the dentition of both arches changed in a patient, including teeth tilting, elongation and occlusal plane change with under-occlusion of the posterior implant restoration after long-term function. Based on this, we hypothesized a mechanism of under-occlusion of the posterior implant restoration. Among patients showing the under-occlusion phenomenon, three patients who had a long-term follow-up and had a model produced at the time of restoration were enrolled. The dentition changes were analyzed via digital scanning and superimposition of the model at the time of restoration, with the current model showing under-occlusion. Based on the result of superimposition, tooth elongation occurs mainly in the maxilla, and two types of positional changes occur in the mandible, specifically in the anterior-superior and posterior-inferior direction. The mechanism of under-occlusion of the posterior implant could be the result of tooth elongation and the relative positional change of the mandible.

Purpose: Proper tooth alignment directs occlusal forces along the long axis, supporting optimal masticatory function and periodontal health. Deviations that lead to non-axial forces are common; however, teeth with such deviations often maintain optimal health. This study aims to assess various occlusal and periodontal parameters in teeth experiencing non-axial forces to better understand the underlying reasons and mechanisms that contribute to their maintained health status.

Materials and methods: Fifty subjects, each with one normally aligned posterior tooth (Group A) and a malaligned contralateral tooth (Group B), were recruited for this study. Clinical assessments were conducted to measure relative occlusal load, gingival status, and alveolar bone levels in both groups. Statistical analyses were performed to compare findings between normally aligned and malaligned teeth.

Results: Seventy two percent of malaligned teeth (9.33 ± 6.38%) exhibited reduced relative occlusal force compared to normally aligned teeth (12.05 ± 8.39%). No significant differences in gingival status or alveolar bone levels were observed between the two groups.

Conclusion: This study demonstrates that malaligned teeth can adapt to non-axial occlusal forces while preserving their structural integrity, which could imply the presence of adaptive mechanisms within the stomatognathic system. Further research is needed to differentiate the types and directions of occlusal forces and to explore the broader clinical implications of these findings across diverse populations.

Purpose: This study aimed to compare the accuracy of an alternative scan path with that of traditional scan paths to obtain a more accurate method for complete arch scans.

Materials and methods: A mandibular stone cast, including tooth preparations for the inlay, crown, and fixed prosthesis, was scanned 10 times using four different scan paths (A, B, C, and D). The scans were converted into stereolithography files, resized, and superimposed onto a control file obtained from a desktop scanner. The scan time, total surface deviation, and local deviation of the mandibular teeth were measured. One-way analysis of variance (ANOVA) and Welch ANOVA were used for statistical analyses (α = .05). The relative standard deviation and standard error of the mean were calculated to evaluate accuracy.

Results: The total surface deviation differed significantly according to the scanning path despite a similar scan time. Path D had the highest accuracy and the most uniform color maps, showing minimal deformation of the digital model. Meanwhile, no significant differences were found in the local deviations in the individual tooth assessments, likely owing to issues with the superimposition method.

Conclusion: Among all scan paths, the scan path with the shortest distance from the starting point to the end point showed the smallest total surface deviation and the highest accuracy. No differences were observed in the deviations of specific teeth based on the scan path.