Journal of prosthodontic research最新文献

Purpose: To perform vertical bone augmentation on rat parietal bone by coating the inner surface of dense polytetrafluoroethylene (d-PTFE) domes with hydroxyapatite (HA) using Erbium Yttrium Aluminum Garnet (Er:YAG) pulsed laser deposition in a rat model.

Methods: The d-PTFE plate surface, α-tricalcium phosphate (α-TCP) coating, and HA coating were measured using scanning electron microscopy and X-ray diffraction to confirm the replacement of α-TCP with HA via high-pressure steam sterilization. The dome was glued to the center of the rat parietal bone and closed with periosteal and epithelial sutures. The rats were euthanized at 4, 8, and 12 weeks postoperatively, and the d-PTFE dome and surrounding tissues were harvested for radiological and histological evaluation.

Results: In a group without HA coating (control group), a small amount of layered neosteum was observed in the d-PTFE dome. Conversely, a new balloon-shaped bone was observed in a HA-coated group (experimental group). Bone growth and number of bone beams were higher in the HA-coated group from 4 to 12 weeks postoperatively than those in the control group. However, no significant differences in bone mineral density values or bone bridge widths were observed.

Conclusions: The HA coating enhanced bone augmentation without bone replacement. Histological findings indicated that the new bone comprised normal bone tissue with cartilage lumen and matrix. Therefore, our results indicate that bone augmentation with a HA coating may be mediated by endochondral ossification, a process similar to that of ectopic ossification.

Purpose: This study aimed to investigate the association between denture restoration and cognitive impairment through a meta-analysis and to assess the correlation between different degrees of tooth loss.

Study selection: Observational studies exploring the association between denture restoration and cognitive function were systematically searched across six databases from January 2000 to January 2024. Two researchers independently searched electronic databases and extracted relevant studies from all articles.

Results: This study included 24,252 participants from six observational studies. The risk ratio and 95% confidence interval (CI) were used to compare the risk of cognitive impairment. Participants who experienced tooth loss without dentures had a 1.27-fold (95% CI: 1.20-1.38) higher risk of cognitive impairment, whereas those with dentures had only a 1.01-fold (95% CI: 0.92-1.12) higher risk. In the dose-response analysis, the risk of cognitive impairment in the non-denture group increased by 1.009 times (95% CI: 1.006-1.012) for each tooth lost, whereas the denture restoration group showed a 1.003 times (95% CI: 1.000-1.006) increased risk. The years of follow-up and clinical measurement tools simultaneously explained this heterogeneity.

Conclusions: This study provides detailed evidence of a potential association between denture restoration and a reduced risk of cognitive impairment. Furthermore, there was a correlation between denture restoration and a reduced impact of the number of teeth lost on the risk of cognitive impairment. Therefore, timely and reasonable denture restoration may contribute to prevent cognitive impairment.

Purpose: Artificial intelligence (AI) may be used to learn and predict the maxillomandibular relationship, particularly when the number of occluding teeth pairs is insufficient. This study aimed to investigate the feasibility of training a new two-stage coarse-to-fine teeth alignment pipeline AI system in predicting maxillomandibular relationships based on the occlusal morphology of antagonistic teeth.

Methods: Maxillary and mandibular stone casts were collected and scanned at the maximal intercuspal position (MIP). A deep learning alignment network was trained using 90% of cast pairs. The remaining 10% of pairs were input into the trained AI system for validation. The maxillomandibular relationships predicted by the AI system were superimposed and compared with those of the mounted casts. Cartesian x-, y-, and z-coordinates were defined for each mandibular tooth scan with respect to (w.r.t.) its occlusal plane and dental midline. The discrepancy in the position of maxillary teeth scans was described based on rotation and translation.

Results: A total of 325 pairs of maxillary and mandibular stone casts were collected, with 300 pairs used for training and 25 for validation. For the AI-predicted maxillomandibular relationship, the mean rotational discrepancies w.r.t. the x-, y-, and z-axis were 1.407°±1.548°, 1.269°±8.476°, and 0.730°±1.334°, respectively. The mean translational discrepancies w.r.t. the x-, y-, and z-axis were 0.185±1.324 mm, 1.222±0.848 mm, -1.034±0.273 mm, respectively.

Conclusions: The AI-predicted maxillomandibular relationship for maxillary and mandibular teeth scans shows discrepancies of less than 1.3 mm and 1.5° compared to the actual relationships.

Purpose: We aimed to analyze the influence of different designs (inlay, onlay, and crown) on stress distribution and crack propagation in an endodontically treated cracked premolar.

Methods: Three-dimensional (3D) finite element analysis (FEA) was employed to model an endodontically treated cracked premolar with three different restorations (inlay, onlay, and crown). Six types of loadings (vertical loading of 600 N; hot thermal-600 N vertical coupling loading; cold thermal-600 N vertical coupling loading; oblique loading of 200 N; hot thermal-200 N oblique coupling loading; cold thermal-200 N oblique coupling loading) were applied to simulate the hot and cold food/beverages intake. The Von-Mises Stress (VMS) on the lower margin of the crack surface was measured at 20 points in each model, and the position of the stress concentration on the crack surface was analyzed.

Results: All three restoration types effectively improved stress distribution. The influence of different restorative modalities on the stress distribution at the crack tip exhibited different trends under different loading conditions. Lateral loading and/or hot thermal cycling increased the intensity of VMS, and crown restoration exhibited the highest stress concentration at the crack tip under lateral loading and hot thermal cycling.

Conclusions: From a mechanical perspective, the outcome of this study suggested that a full crown restoration is not the optimal choice for preventing further crack propagation. Additionally, it is recommended to reduce the consumption of excessively hot foods and beverages daily.

Purpose: This study investigated the effects of femtosecond laser (FL) irradiation on the surface roughness and shear bond strength of high-translucency zirconia (6 mol% yttria-partially stabilized zirconia [6Y-PSZ]) and lithium disilicate (Li₂SiO₃) glass ceramics.

Methods: Fully sintered square-shaped specimens of 6Y-PSZ (7 groups; 20 specimens/group) and Li₂SiO₃ (8 groups; 20 specimens/group) were surface-treated via sandblasting (50-μm alumina sand or glass beads) or FL irradiation (20- or 40-μm dot or cross-line patterns) or using Monobond Etch & Prime (Ivoclar Vivadent AG; only for Li₂SiO₃ specimens). The surface roughness (arithmetic average [Sa] and developed interfacial area ratio [Sdr]) and shear bond strength after 24 h and 10,000 thermal cycles were measured and statistically analyzed.

Results: The surface roughness of both ceramics significantly increased after 40-μm cross-line FL irradiation. The Sdr also significantly increased after FL irradiation. The 20- and 40-μm cross-line laser-irradiated 6Y-PSZ samples showed the highest shear bond strength after 24 h and 10,000 thermal cycles, respectively. Li₂SiO₃ glass-ceramic specimens showed the highest shear bond strength after Monobond Etch & Prime treatment for both groups. The 40-μm cross-line laser-irradiated Li₂SiO₃ glass-ceramic specimens exhibited high shear bond strength after thermal cycling.

Conclusions: FL significantly increases the bonding efficacy of 6Y-PSZ and Li₂SiO₃ glass ceramics. Furthermore, Monobond Etch & Prime is effective for the surface treatment of Li₂SiO₃ glass ceramics. Therefore, FL can be used to effectively treat the surfaces of dental restorations in clinical settings, facilitating enhanced adhesion between the restoration and the tooth.

Purpose: This study investigated the bond strength between short fiber-reinforced resin composite (SFC) and dentin following air abrasion with various types of abrasive particles.

Methods: A total of 120 human molars were prepared for a shear bond strength (SBS) test of the resin composite. The teeth were divided into 12 groups (n = 10/group) based on the air abrasion particle used. Half of the groups underwent phosphoric acid etching (10 s) prior to air abrasion, while the other half received no pretreatment. Air abrasion was performed using five types of particles, after which a two-part adhesive (G2 Bond) and SFC were applied on the treated surfaces. The SBS test was performed using a universal testing machine at a crosshead speed of 1.0 mm/min until failure. Two additional specimens from each group were prepared to evaluate the air abraded surface using scanning electron microscopy after being stored in simulated body fluid (SBF) for two weeks. Statistical analysis was performed using two-way analysis of variance and the Tukey test (α = 0.05).

Results: The highest SBS values were observed in the control group (18.9 MPa), which did not undergo air abrasion. The use of different air abrasion particles affected the SBS of SFC to dentin (P < 0.05), as air abrasion with jet sand in the absence of pre-etching differed significantly from the other Cojet group (P < 0.05).

Conclusions: Air abrasion with various particles did not improve the bond strength between the SFC and dentin.

Purpose: The basal bone of the anterior maxilla plays a crucial role in maintaining primary stability of immediate implants. However, no consensus exists on the relationship between basal bone width and immediate implant success, unlike for basal bone length. This study presents a clinical scheme to predict the primary stability of immediate implants using the basal bone width.

Methods: Cone-beam computed tomography (CBCT) images were acquired from 1000 patients to determine the quantitative characteristics of the basal bone of the anterior maxilla. Basal bone dimensions, including the length and width along the tooth and bone axes, and immediate implant-related hard tissue indices, were measured on the sagittal sections. Descriptive statistics, frequency, multiple correlation, and canonical correlation analyses were performed.

Results: Basal bone indices were significantly greater in men than in women and exhibited different patterns of change with increasing age. Canonical correlation analyses revealed that the basal bone indices, especially basal bone width, correlated with other immediate implant-related indicators, among which the total width of the basal bone at 2 mm apical to the apex (Apical-2mm) exhibited the greatest contribution. Apical-2mm was positively correlated with the coronal bone dimensions, apical bone dimensions, basal bone length, and angulation.

Conclusions: The basal bone width of the maxillary anterior tooth may reflect the distribution of other implant-related anatomical indices, which may provide an additional reference for predicting the primary stability of an immediate implant.

Purpose: To compare the stress distribution in loaded zirconia resin-bonded fixed dental prostheses (RBFDPs) and periodontal tissue using finite element analysis, considering reduced alveolar bone levels and the number of retainers.

Methods: A human skull was micro-CT scanned. Three framework designs were tested: a 2-unit RBFDP using the maxillary left central incisor (#21) as an abutment, another using a canine (#23), and a 3-unit RBFDP using both #21 and #23. The models were categorized based on the distance from the cemento-enamel junction (CEJ) to the alveolar bone: M1 (1 mm), M2 (2 mm), M4 (4 mm), M6 (6 mm), and M8 (8 mm).

Results: The shear stresses in the adhesive resin cement were lower in the 2-unit designs than in the 3-unit design in the M4-M8 models. The maximum principal stresses in the framework were smaller in the 2-unit design than in the 3-unit design for all models. The maximum principal strains in the periodontal ligament and trabecular bone in #21 were greater in the 2-units than in the 3-units in the M4-M8 models.

Conclusions: This study suggests that cantilever RBFDPs may have a lower risk of framework fracture than 2-retainer RBFDPs, regardless of the reduction in alveolar bone levels. In cases with alveolar bone levels >4 mm below the CEJ, the cantilever RBFDPs had a smaller risk of debonding than the 2-retainer RBFDPs; however, it may increase the damage to periodontal tissue.

Purpose: This study evaluated biomechanical behavior of endocrown and post-core restorations produced from computer aided design/computer aided manufacturing (CAD/CAM) and traditional materials in severely damaged teeth that lack a ferrule and assessed the associated failure risk of resin cement.

Methods: A phantom maxillary central incisor and mandibular second premolar were trimmed 1 mm coronally to the cemento-enamel junction, the root canals were enlarged, and the teeth were scanned. Data were transferred to a solid modeling software. Twenty-two models were constructed, including endocrowns (hybrid ceramic, lithium disilicate, and polyetheretherketone [PEEK]) and post-cores (glass-fiber post/composite core; glass-fiber single-piece post-core; PEEK single-piece post-core; gold single-piece post-core). Hybrid ceramic and lithium disilicate crowns were modeled on the post-cores. Loads of 100 N for the central incisor and 300 N for the premolar were applied in a 45° oblique direction. von Mises stresses were analyzed on both root dentin and restorations, and the failure risks for the resin cement were calculated.

Results: The highest stresses were found at the roots of the PEEK endocrown (37.6 MPa) for the central incisor and of the lithium disilicate endocrown for the premolar (40.0 MPa) among endocrown groups. PEEK endocrowns had the lowest stress within the restoration and presented a higher risk of cement failure. The glass-fiber post/composite core groups demonstrated the highest adhesive and cohesive failure risks for post cement.

Conclusions: For the central incisor and mandibular premolar, lithium disilicate and PEEK endocrowns, respectively, generated less stress at the root. However, PEEK endocrowns had a higher risk of cement failure.

Purpose: This retrospective clinical study aimed to evaluate the clinical outcomes of surveyed monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia crowns for abutment teeth in removable partial dentures (RPDs).

Methods: Patients who received monolithic surveyed zirconia crowns were clinically examined. The crowns were examined according to the modified United States Public Health Service criteria, and Kaplan-Meier survival was determined. The effect of different variables on the survival and success rates was assessed using Cox regression analysis (α = 0.05).

Results: A total of 297 crowns of 275 patients were evaluated over a mean period of 7 years. The cumulative survival and success rates were 95.6% and 91.2%, respectively. Complications were in the form of secondary caries (n=12), minor chipping (n=9), and debonding (n=5). A higher number of failures was observed in the mandibular molars (P < 0.05).

Conclusions: Surveyed monolithic zirconia crowns demonstrated high survival after 7 years of service. Monolithic zirconia is an excellent alternative to metal ceramic crowns for RPD abutments.