Journal of Advanced Prosthodontics最新文献

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.

[This corrects the article on p. 302 in vol. 16, PMID: 39512875.].

Purpose: This study aimed to investigate the extent to which intraoral scanning are affected by clinical conditions, and whether ambient lighting and different color temperatures have an impact on the accuracy of intraoral scanner, as well as to evaluate scanning time.

Materials and methods: Twelve different environments were created using various ambient lighting conditions (0, 500, 1000 and 1500 lux) and color temperatures (white, blue and yellow). A partially edentulous mandibular model with two implants and a three-unit bridge was scanned under each environment until 10 digital models were obtained, and scanning times were recorded using a virtual stopwatch. A 3D analysis was performed on the obtained digital models, and the data were analyzed using a software. The generalized linear model analysis and Tukey multiple comparison test were used to analyse the data (P < .05).

Results: The effect of lux, color temperature, and scanning times on RMS data was found to be significant (P < .001). The mean RMS value was the highest in the 0 lux group and the lowest in the 500 lux group. Regarding the color temperature, the highest RMS value was in the white color group and the lowest in the yellow color group. Scanning times were similar among the 0, 500 and 1000 lux groups, with a significant increase in the 1500 lux group.

Conclusion: Different ambient lighting conditions and color temperatures have significant effect on the accuracy of intraoral scanning.

Purpose: This study aimed to investigate the relationships between reference planes and oral functions on the habitual and non-habitual chewing sides.

Materials and methods: Thirty-four subjects with no abnormalities in the maxillofacial region and oral functions were enrolled in this study. Relationships between angles between the reference plane (Frankfort horizontal plane, Camper's plane, and occlusal plane) and masticatory performance, occlusal force, and occlusal contact area by chewing side were examined. Regarding the measurement of reference planes, a creatively modified three-plane measuring device was used to measure angles between the reference planes. Images were taken from the right and left sides and angles between reference planes were measured. Masticatory performance was examined by measuring the amount of glucose extracted from a gummy jelly on the habitual and non-habitual chewing sides separately. Occlusal force and occlusal contact area were measured by occluding against pressure-sensitive film, and values on the habitual and non-habitual chewing sides were calculated and analyzed.

Results: The angle between Camper's plane and the occlusal plane correlated with masticatory performance on both the habitual chewing side (r = 0.47, P < .01) and the non-habitual chewing side (r = 0.36, P < .05). A correlation was observed between masticatory performance and occlusal force on the habitual chewing side (r = 0.46, P < .01).

Conclusion: Masticatory performance became higher as occlusal plane inclination increased. This result represents essential knowledge for prosthetic treatment.

Purpose: The aim of this study was to investigate microstrains around two non-parallel implant-supported prostheses and different abutment connections and positions under vertical static load using strain gauges.

Materials and methods: 4 models simulating the mandibular unilateral free-end were fabricated. 8 implants (4.0 × 10 mm and 5.0 × 10 mm) were inserted in the second premolar, perpendicular to the occlusal plane, and the second molar, tilted at 15°. Four groups were analyzed: engaging and angled abutments (control group), both non-engaging abutments, both screw-and cement-retained prosthesis (SCRP) abutments, and engaging and non-engaging abutments. Strain gauges were placed buccally, lingually, mesially, and distally adjacent to each implant. The restoration was cement-retained in the control group and screw and cement-retained in the rest. Zirconia bridges were fixed on the abutment with NX3, and a 300 N vertical static load was applied. Microstrains were recorded and analyzed.

Results: Both non-engaging abutments showed the highest compressive microstrains (-52.975), followed by engaging, angled abutment (-25.239). SCRP-SCRP abutments had the lowest compressive microstrains (-14.505), while the engaging, non-engaging abutments showed tensile microstrains (0.418). Microstrains in SCRP-SCRP and engaging, non-engaging groups were significantly lower than in the control group (α = .05). Premolar areas showed compressive microstrains (-47.06), while molar sites had tensile microstrains (+0.91), with microstrains in premolars being significantly higher than in molar area (α = .05).

Conclusion: The types of abutment connections and positions may have a potential effect on microstrains at the implant-bone interface. SCRP-SCRP abutments could be an alternative to use in non-parallel implant-supported prostheses when two implants make an angle of no more than 20 degrees.

Purpose: Studies about success of FPDs (fixed partial dentures) mostly include restorations built by different clinicians. This results in limited comparability of the data. The aim of this study was to evaluate complications of all-ceramic FPDs built by 1 dentist between 2011 to 2023.

Materials and methods: 342 all-ceramic FPDs were observed during follow-up care. 48 patients received 262 single crowns, 59 bridges and 21 veneers. Because of the different lengths of the bridges, units were defined as restored or replaced tooth. 465 units performed by the same dentist from Nov 2011 to Nov 2022 were included. Influencing factors "restoration", "construction", "abutment", "localization", "vitality" and "application period" were evaluated using Kaplan-Meier Analysis and Log-Rank Tests.

Results: 406 units (87.3 %) showed no complication. 7 correctable chippings (1.5 %) and 10 recementable decementations (2.1 %) occurred. Six decemented units got lost (1.3 %). 21 units failed due to fatal fracture (4.5 %). Crown margin complications, such as secondary caries, occurred in 15 units (3.2 %). Comparing the influencing factors resulted in higher complication rates of veneers (P < .001), of monolithic ceramics (P ≤ .050) and of molar-restorations (P = .047). The application period had no influence on the success and survival rate.

Conclusion: Overall, all-ceramic FPDs showed good clinical results. Although less complications were observed with modern restorations, these more often led to complete failure. To generate evidence-based recommendations, further studies are needed to evaluate the mid- and short-term success and survival of current all-ceramic restorations.