Journal of prosthodontic research最新文献

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: This systematic review aims to assess the impact of different 3D printing orientations on the physico-mechanical properties, volumetric change, and accuracy of additively manufactured ceramic specimens, as well as their restorations.

Study selection: The web database containing records for building orientation of 3D-printed ceramics until January 2024 was searched, with no language limitations. PRISMA 2020 guidelines were followed, and the risk of bias was evaluated using the modified CONSORT checklist for laboratory studies on dental materials. The RevMan 5.4 of Cochrane collaboration was used for the meta-analysis with α<0.05.

Results: In this systematic review, 35 out of 2967 records were considered. The printing orientations had a significant influence on the mechanical properties of the additively manufactured specimens (P < 0.05), specifically, the horizontally printed specimens exhibited the best mechanical behavior, while the physical properties exhibited controversial results. Additionally, the printing orientations had a significant impact on the volumetric shrinkage and accuracy of molar teeth (P < 0.05).

Conclusions: The ideal mechanical outcome was observed when ceramic specimens were 3D-printed in a horizontal direction relative to the platform, while vertically printed specimens showed the worst properties. The printing orientations affect the volumetric change of the specimens; however, volumetric change highly depends on the sintering parameters. It is recommended to 3D print ceramic molar crowns at 180° with the occlusal surface facing the printing platform.

Clinical significance: Several factors affect the additively manufactured restorations throughout the printing procedure. Therefore, printing orientation should be carefully considered before the additive production process of ceramic restorations.

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 aimed to explore the association between oral function and mental health status in older adults and to determine the potential mediating roles of fruit and vegetable intake and social interaction.

Methods: This cross-sectional study included 478 community-dwelling older adults aged ≥75 years in Japan. Oral functions (occlusal force, masticatory performance, tongue pressure, tongue-lip motor function, and swallowing function), mental health status, dietary assessment, frequency of outings and interactions with others, and the following confounders were evaluated: educational level, financial satisfaction, residential status, comorbidities, and cognitive function. Structural equation modeling was used to assess the following: (a) a basic model, which hypothesized that oral function has a direct effect on mental health status, and (b) a mediation model, which hypothesized that fruit and vegetable intake and social interaction have potential mediating effects on the association between oral function and mental health status.

Results: The basic model revealed a positive direct association between oral function and mental health status (standardized coefficient = 0.10, P = 0.04). Fruit and vegetable intake and social interactions were identified as mediators; however, no direct association with oral function was observed in the mediation model (P = 0.28), indicating that oral function was indirectly associated with mental health status through the mediating effects of fruit and vegetable intake and social interactions.

Conclusions: Oral function showed a significant association with mental health status in community-dwelling older adults. Fruit and vegetable intake along with social interactions mediate this relationship.

Purpose: This retrospective cohort study evaluated the accuracy of analog versus virtual wax-ups in prosthetic-driven planning and guided surgery.

Methods: There were 73 patients with a single missing posterior tooth who underwent either an analog or virtual wax-up design following a prosthetic-driven concept. Intraoral scans of the final restoration were performed 1 year after completion of the restoration. The accuracy was assessed by comparing the deviation between the final restoration and the wax-up (analog or virtual) of each patient at the prosthetic level. The maximum deviation in six areas (buccal top, buccal mid, buccal bottom, lingual top, lingual mid, and lingual bottom) was recorded. The accuracy was also assessed at the implant level by comparing the deviation between the virtual new implant position, which was redesigned based on the final restoration as the new wax-up, and the planned position. The mean deviations in the coronal, apical, angular, and depth measurements were recorded. A two-tailed independent t-test and a one-way analysis of variance were used.

Results: Statistically significant differences were observed between the buccal (P = 0.03) and lingual tops (P = 0.03) at the prosthetic level. Significant differences were observed in the angular (P < 0.01) and coronal (P = 0.01) deviations at the implant level. There were smaller deviations between the analog wax-ups and final restorations regardless of the prosthetic or implant level.

Conclusions: Analog wax-ups were preferable to virtual wax-ups for preoperative design in computer-guided implant surgery.

Purpose: Although the association between oral health and physical frailty is well established, psychological frailty has not been investigated. Therefore, this prospective cohort study was conducted to examine the association between masticatory performance and psychological frailty in older community-dwelling Japanese individuals.

Methods: The participants included 498 older adults who completed baseline and 3- and 6-year follow-up surveys. The World Health Organization-5 (WHO-5) scale and the Japanese version of the Montreal Cognitive Assessment (MoCA-J) were used to evaluate the psychological frailty status of participants. Psychological frailty was defined as a WHO-5 score < 13 and a MoCA-J score < 23. Masticatory performance was evaluated using a scoring method for the test gummy jelly (score: 0-9). A mixed-effects ordinal logit model analysis was used to examine the influence of masticatory performance and number of teeth on the development of psychological frailty while adjusting for relevant factors such as educational level, financial status, living situation, area of residence, history of chronic diseases, and handgrip strength.

Results: A total of 311 participants (62.5%) exhibited psychological robustness at baseline. The rates of development of psychological frailty after 3 and 6 years were 4.2% and 4.5%, respectively. The longitudinal analysis revealed that masticatory performance at baseline was negatively associated with the prevalence of psychological frailty and pre-frailty at follow-up.

Conclusions: Decreased masticatory performance is associated with the development of psychological frailty in older community-dwelling people of Japanese descent.

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: Psoriasis is a complex, chronic inflammatory keratosis of unclear origin that is challenging to treat. In patients with psoriasis suspected of having metal allergies, the removal of oral metallic prostheses contributes to the alleviation of psoriasis symptoms. However, the relationship and mechanism of the metal removal effect and improvement in psoriasis symptoms in patients with metal allergies are unknown. This study aimed to investigate the relationship between metal allergies and psoriasis using an animal model.

Methods: In the metal allergy model, 4-week-old rats were sensitized and treated with nickel (II) chloride (NiCl₂) solution (provocation model). In the psoriasis model, imiquimod (IMQ) cream was applied to the shaved dorsal skin of rats (IMQ model). To create a psoriasis/metal-allergy composite rat model, we combined the provocation and IMQ models (provocation + IMQ model). Macroscopic observation, histological analysis, and quantitative gene expression analyses were performed to evaluate outcomes.

Results: In the IMQ model, psoriasis-like symptoms were visually observed from day 2 to day 9. In the provocation + IMQ model, psoriasis-like symptoms persisted for at least 11 days. Histological analysis revealed epidermal thickening and an increase in the number of interleukin (IL)-17-positive cells in the provocation + IMQ model on days 7 and 9. The gene expression of IL-17 in the submandibular lymph nodes and spleen increased in the provocation + IMQ model.

Conclusions: The induced state of Ni allergy may contribute to the maintenance of psoriasis pathology through IL-17 activity.

Purpose: To determine the effect of wall thickness on the fracture load of hollow-structured zirconia teeth fabricated using 3D printing.

Methods: The geometry of an artificial ceramic tooth (mandibular right first molar) was copied and modified. The final test group design yielded wall thicknesses of 0.30, 0.50, 0.75, and 1.00 mm. Twenty zirconia specimens from each group were fabricated using a 3D printer. Artificial teeth were divided into subgroups of teeth that remained hollow (hollow teeth) or were filled with resin (filled teeth). Fracture load tests were performed, and each artificial tooth was examined using a digital microscope. Analysis of variance was used to compare the fracture resistance of the artificial zirconia teeth among the conditions, followed by pairwise Tukey's tests. T-tests were used to compare the fracture resistance between the hollow and filled teeth within the test groups.

Results: The fracture resistance of artificial zirconia teeth decreased significantly (P < 0.001) with decreasing wall thickness. The mean fracture load reached ≥500 N for wall thicknesses of 0.75 mm and 1.00 mm. Resin filling of crowns significantly improved the fracture load of very thin walls. Microscopy revealed that most occlusal surfaces of the hollow teeth were completely fractured, whereas all the fracture surfaces of the filled teeth were incompletely fractured.

Conclusions: Artificial zirconia teeth offer sufficient fracture resistance for clinical use when the wall thickness is ≥0.75 mm, regardless of the presence of resin filling.

Purpose: The primary aim of this study was to determine the continuation and success rates of oral appliance (OA) therapy for patients in whom continuous positive airway pressure (CPAP) therapy failed. The secondary aim was to identify predictive factors for the long-term use of OA in patients with CPAP failure.

Methods: A total of 81 patients who failed with CPAP use were included in this study. Patients who had been using OA for more than 1 year at follow-up visits were assigned to Group S, whereas those who discontinued OA or were lost to follow-up within 1 year were assigned to Group D. We investigated the continuation and success rates of OA therapy, as well as predictive factors for its long-term use for those with CPAP failure.

Results: Of the 81 patients, 60 were in Group S and 21 were in Group D; 74.0% of patients with CPAP failure continued OA therapy for more than 1 year. The apnea-hypopnea index was reduced from 41.3±21.7/h to 12.4±6.5/h with OA therapy. The only significant predictor of long-term OA use in patients with CPAP failure was awareness of the effectiveness of OA therapy after 1 month (P = 0.003, odds ratio: 9.731, 95% confidence interval: 2.146-44.119).

Conclusions: Patients who recognized the effectiveness of OA treatment in the early stages were more likely to continue using OA therapy long-term.