Journal of prosthodontic research最新文献

Purpose: This study aimed to analyze how the wall thickness of 3D-printed hollow zirconia teeth affects shape accuracy.

Methods: Datasets with measurement points were created for different artificial teeth resembling the mandibular right first molar (Geomagic Design X, 3D Systems). Reference distances were 9.8 mm for mesio-distal direction (M-D), 10.9 mm for bucco-lingual direction (B-L), 7.0 mm for MB-BB and DB-BB, and 4.5 mm for ML-LB and DL-LB. The outer geometry was identical for all artificial teeth with wall thicknesses of 0.30, 0.50, 0.75, and 1.00 mm. Twenty zirconia teeth were fabricated using a 3D printer (CeraFab 7500 Dental, Lithoz) for each group and sintered before support removal. After performing analog distance measurements using a micrometer screw, the digital distance measurements and angular deviations between measurement points on 3D scans were analyzed. Possible effects were investigated using nonparametric ANOVA, followed by Tukey's honest significant difference (HSD) test for multiple comparisons.

Results: The shape accuracy was acceptable for artificial teeth with wall thicknesses of ≥0.5 mm. The largest distance deviation was observed for a wall thickness of 0.3 mm. In particular, DB-BB showed a median deviation of >56.2 µm, which is significantly larger than that for other test groups, ranging from 7.4-9.5 µm (P < 0.05). In most cases, angular deviations were the largest for teeth with 0.3-mm wall thickness (11.6°) and remained below 5.0° for the other test groups.

Conclusions: Acceptable accuracy was obtained for artificial teeth with wall thicknesses of at least 0.5 mm.

Purpose: Acute stroke often leads to dysphagia. In the oral stage of dysphagia, there is a potential for immediate benefit from using a palatal augmentation prosthesis (PAP). We investigated whether our quickly fabricated, simple, and expedited version of PAP would result in an immediate improvement in swallowing function after an acute stroke.

Methods: We analyzed the records of stroke patients that were hospitalized between October 2019 and March 2022 and met the following criteria: they had a rehabilitation prescription and had paralysis of facial or hypoglossal nerves and either repeated salivary swallowing test ≤2 times or modified water swallow test ≤3, they were fasting, were within 3 weeks of onset, and had a simple PAP made for them. Outcomes included with/without PAP, maximum tongue pressure, repeated salivary swallowing test, and modified water swallow test on the day after starting to wear PAP was started. In addition, within one week, a videofluoroscopic examination was performed to measure the oral transit time, pharyngeal transit time, and penetration aspiration scale. Statistical analyses were performed using Wilcoxon signed-rank tests. Statistical significance was set at P < 0.05.

Results: Fifteen patients met the inclusion criteria and were included in this study. The mean age of the subjects was 76.9 ± 9.0 years. The use of PAP significantly increased maximum tongue pressure (P < 0.0001*) and shortened oral transit time (P < 0.0091*). There were no significant differences among the other items.

Conclusions: Simple PAP immediately increased the maximum tongue pressure and improved swallowing function during the oral stage.

Purpose: This study aimed to evaluate the risk of bone loss around single short molar crown-supporting implants in an atrophic mandible.

Methods: Implants of different lengths (L = 4 or 6 mm) and diameters (Ø = 4.1 or 4.8 mm) were placed in the molar area of an atrophic mandible. Additional control mandible models were simulated for 4.1 mm diameter implants (L = 4, 6, 8, and 10 mm). A vertical masticatory load of 200 N was applied to three or six occlusal contact areas (3ca or 6ca) of the prosthetic crown. The bone strain energy density (SED) of 109.6 µJ/mm³ was assumed to be the pathological threshold for cortical bone. The peri-implant bone resorption risk index (PIBRri) was calculated by dividing the maximum SED of the crestal cortical bone by the SED pathological threshold.

Results: Increasing the implant length from 4 to 6 mm, implant diameter from 4.1 to 4.8 mm, and number of contact areas from 3 to 6 reduced the SED and PIBRri values by approximately 20%, 35%, and 40%, respectively, when comparing pairs of models that isolated a specific variable. All models with 6ca had a low bone resorption risk (PIBRri<0.8), while the Ø4.1 short implant with 3ca had a medium (0.8≤PIBRri≤1.0) or high (PIBRri>1.0) resorption risk.

Conclusions: Increasing the diameter or occlusal contact area of a 4 mm short implant in an atrophic mandible resulted in reduced bone resorption risks, similar to or lower than those observed in a regular mandible with standard-length implants.

Patients: An 18-year-old woman sought treatment for caries of the anterior teeth after completing orthodontic treatment. Direct composite resin restoration was chosen because the patient preferred a minimally invasive and cost-effective treatment whenever possible. Based on diagnostic wax-up, veneer-shaped indices for composite resin injection were designed to replicate and restore tooth defects rapidly and accurately. The overall esthetic result was excellent after a 1-year of follow-up.

Discussion: Direct freehand composite resin restorations are clinically challenging. The recently proposed 3D printing index for the composite resin injection technique is helpful for direct restoration but is challenging to remove. The veneer-shaped indices avoid the formation of an undercut in the direction of removing the index, making them easy to remove after finishing the restorations.

Conclusions: Using veneer-shaped indices for composite resin injection enables rapid esthetic rehabilitation of labial tooth defects caused by caries. This approach reduces chairside time and operational difficulty while allowing for easy index removal after completing the restorations.

Patients: This case report describes a procedure for assessing changes in occlusal relationships in patients with acquired open bites due to temporomandibular joint disease using an intraoral scanner (IOS). A digital impression was made using the IOS at the initial visit. Subsequent impressions were made every 6 months using the IOS and magnetic resonance imaging (MRI) or computed tomography (CT). Standard triangulated language (STL) image files of two digital impressions at different points in time were superimposed, including the occlusal relationship with reference to the maxillary dentition. Finally, three-dimensional (3D) changes in the occlusal relationship over time were evaluated.

Discussion: In Case 1, the superimposed STL image indicated almost no evident deviation of the mandible. Therefore, an orthodontic treatment was initiated. In contrast, in cases 2 and 3, where changes in the occlusal relationship continued, secondary treatment was postponed and patients continued to be monitored periodically. In case 3, even though left condyle resorption was progressive, the degree of open bite on the right side improved after 6 months. However, the open bite continued to progress for another 6 months despite the stability of the condyle.

Conclusions: Changes in the condylar shape observed using imaging may not always reflect changes in the occlusal relationship. In addition to changes in the condyles and eminences of the temporomandibular joint (TMJ), changes in the occlusal relationships of patients with acquired open bite should be evaluated using an intraoral scanner.

Purpose: This review aims to summarize the available technologies, material categories, and prosthodontic applications of additive manufacturing (AM) dental ceramics, evaluate the achievable accuracy and mechanical properties in comparison with current mainstream computer-aided design/computer-aided manufacturing (CAD/CAM) subtractive manufacturing (SM) methods, and discuss future prospects and directions.

Study selection: This paper is based on the latest reviews, state-of-the-art research, and existing ISO standards on AM technologies and prosthodontic applications of dental ceramics. PubMed, Web of Science, and ScienceDirect were amongst the sources searched for narrative reviews.

Results: Relatively few AM technologies are available and their applications are limited to crowns and fixed partial dentures. Although the accuracy and strength of AM dental ceramics are comparable to those of SM, they have the limitations of relatively inferior curved surface accuracy and low strength reliability. Furthermore, functionally graded additive manufacturing (FGAM), a potential direction for AM, enables the realization of biomimetic structures, such as natural teeth; however, specific studies are currently lacking.

Conclusions: AM dental ceramics are not sufficiently developed for large-scale clinical applications. However, with additional research, it may be possible for AM to replace SM as the mainstream manufacturing technology for ceramic restorations.

Purpose: To build an image recognition network to evaluate tongue coating status.

Methods: Two image recognition networks were built: one for tongue detection and another for tongue coating classification. Digital tongue photographs were used to develop both networks; images from 251 (178 women, 74.7±6.6 years) and 144 older adults (83 women, 73.8±7.3 years) who volunteered to participate were used for the tongue detection network and coating classification network, respectively. The learning objective of the tongue detection network is to extract a rectangular region that includes the tongue. You-Only-Look-Once (YOLO) v2 was used as the detection network, and transfer learning was performed using ResNet-50. The accuracy was evaluated by calculating the intersection over the union. For tongue coating classification, the rectangular area including the tongue was divided into a grid of 7×7. Five experienced panelists scored the tongue coating in each area using one of five grades, and the tongue coating index (TCI) was calculated. Transfer learning for tongue coating grades was performed using ResNet-18, and the TCI was calculated. Agreement between the panelists and network for the tongue coating grades in each area and TCI was evaluated using the kappa coefficient and intraclass correlation, respectively.

Results: The tongue detection network recognized the tongue with a high intersection over union (0.885±0.081). The tongue coating classification network showed high agreement with tongue coating grades and TCI, with a kappa coefficient of 0.826 and an intraclass correlation coefficient of 0.807, respectively.

Conclusions: Image recognition enables simple and detailed assessment of tongue coating status.

Purpose: A growing body of evidence suggests that oral health is associated with a wide range of health outcomes; however, opinions tend to vary because of inconsistent findings. This study aimed to simultaneously examine the association between oral health status and multiple health and well-being indicators using outcome-wide epidemiology.

Methods: Data were obtained from the Japan Gerontological Evaluation Study. Oral health status was categorized as: ≥20 teeth, 10-19 teeth with dental prosthesis, 0-9 teeth with prosthesis, 10-19 teeth without prosthesis, and 0-9 teeth without prosthesis. We examined the associations between oral health status in 2013 and 35 health and well-being outcomes in 2019, including physical/cognitive health, psychological distress, subjective health, social well-being, prosocial/altruistic behaviors, and health behaviors, using two databases (n=32,827 and 15,905).

Results: Compared to individuals with ≥20 teeth, those with <20 teeth had a 10-33% higher risk of mortality and a 6-14% higher risk of functional disability six years later. Additionally, individuals with fewer than 20 teeth tended to go out less frequently and eat fewer vegetables and fruits. Furthermore, individuals with 0-9 teeth without a prosthesis were more likely to have severe functional disability (risk ratio (RR):1.17, 95% confidence interval (CI):1.05-1.31), engage in fewer intellectual activities (standardized difference: 0.17, 95% CI: 0.10-0.24), and feel more hopeless (RR: 1.21, 95% CI: 1.04-1.41).

Conclusions: The prevention of tooth loss and prosthodontic treatment may be associated with reduced mortality and functional disability, as well as maintenance of intellectual ability, frequency of going out, and improvements in dietary lifestyle.

Purpose: To improve smile esthetics, clinicians should comprehensively analyze the face and ensure that the sizes selected for the maxillary anterior teeth are compatible with the available anthropological measurements. The inter commissural (ICW), interalar (IAW), intermedial-canthus (MCW), interlateral-canthus (LCW), and interpupillary (IPW) widths are used to determine the width of maxillary central incisors (CW). The aim of this study was to develop an automated approach using machine learning (ML) algorithms to predict central incisor width in a young Turkish population using anthropological measurements. This automation can contribute to digital dentistry and clinical decision-making.

Methods: In the initial phase of this cross-sectional study, several ML regression models-including multiple linear regression (MLR), multi-layer-perceptron (MLP), decision-tree (DT), and random forest (RF) models-were validated to confirm the central width prediction accuracy. Datasets containing only male and female measurements, as well as combined were considered for ML model implementation, and the performance of each model was evaluated for an unbiased population dataset.

Results: Compared with the other algorithms, the RF algorithm showed improved performance for all cases, with an accuracy of 96%, which represents the percentage of correct predictions. The plot reveals the applicability of the RF model in predicting the CW from anthropological measurements irrespective of the candidate's sex.

Conclusions: These results demonstrated the possibility of predicting central incisor widths based on anthropometric measurements using ML models. The accurate central incisor width prediction from these trials also indicates the applicability of the proposed model to be deployed for enhanced clinical decision-making.