Comparison of oral hypofunction tests and determination of reference values for a subjective masticatory function test.

BACKGROUND: In Japan, oral hypofunction has been recognized as a disease since 2018. An alternative to occlusal force testing for assessing oral hypofunction is the evaluation of the number of natural teeth. Subjective masticatory function testing, which evaluates the ease or difficulty in chewing foods, is an effective alternative to occlusal force testing. However, no reference values have been established for this test. We determined the reference values of the subjective masticatory function test and evaluated its potential as a substitute for the number of natural teeth for assessing oral hypofunction. METHODS: The sample consisted of 184 older adults who visited the Department of Geriatric Dentistry, Showa University Dental Hospital, from July 2018 to January 2020. The subjective masticatory function test (table for evaluation of chewing function in complete denture wearers [Chewing Score 20]) was performed using 20 foods. The occlusal force test and a receiver operating characteristic curve were used to determine the reference values for Chewing Score 20. The sensitivity, specificity, and positive and negative predictive values were calculated and compared with the occlusal force test and the number of natural teeth. RESULTS: A significant correlation (r) was found between the occlusal force test and the Chewing Score 20 (r = 0.526, p < 0.001). The reference value for Chewing Score 20 was < 85. Although the Chewing Score 20 was less sensitive than the number of natural teeth, it demonstrated a higher specificity and a positive predictive value. CONCLUSION: Herein, a score of < 85 on the subjective masticatory function test was determined to be the optimal quantitative reference. The subjective masticatory function test may be used as an alternative for assessing oral hypofunction.

Development of an optimal relief method for the palatal plate by stress analysis.

BACKGROUND: Plate dentures cannot be easily modified after fabrication; therefore, the sites and magnitude of relief must be effectively assessed at the time of fabrication. However, a considerable variation exists in the magnitude of optimal relief and relief range, and there are no guidelines that present these clearly, leading the dentists to decide subjectively. Thus, this study aims to develop an optimal relief method to improve the stress bearing capacity of the palatal mucosa. METHODS: The objective of this study, namely, the borderline, was set in steps. A three-dimensional finite element model for the pseudopalatal plate was created and used to evaluate the changes in stress distribution in the palatal mucosa due to the selective relief of stresses above the borderline. The resulting data were used to develop the optimal relief method. RESULTS: In the relief model with a borderline of 0.04 MPa or higher, the distribution volume at which a high stress of 0.20 MPa or higher is generated was approximately 800% of that with the no-relief model, and in the relief model with a borderline of 0.06 MPa or higher, the respective ratio was approximately 280%. On the other hand, the relief models with a borderline of 0.14 MPa or higher were approximately 60%. In the mid-palatal relief model, the distribution volume at which a stress of 0.20 MPa or higher was generated was 180% of that in the relief model. CONCLUSIONS: The supportive strength of plates can be increased by selectively applying optimal relief rather than standard relief, allowing for easier and more effective plate-denture treatment.

Experimental study on the factors affecting torque of beam-type implant torque wrenches.

BACKGROUND: Screw breakage and loosening are the most common mechanical complications associated with implant treatment, and they may occur due to excess or inadequate screw tightening torque. When fastening and fixing the implant superstructure, screws are tightened using a torque wrench, which is essential for an accurate tightening force. However, the characteristics of the torque wrench have not been fully verified. Therefore, we aimed to clarify the factors affecting the torque with a focus on beam-type torque wrenches, which are the main types of wrenches. METHODS: The torque values generated by beam-type torque wrenches from eight manufacturers were measured using a torque gauge. To investigate the influence of the location of the beam relative to the scale, measurements were performed with a scale aligned with the trailing edge, center, and leading edge of the beam respectively. Additionally, measurements were taken at 90°, 60°, and 30° to examine the effect of the angle at which the examiner read the torque value. Under each condition, a single examiner applied the recommended torque to each manufacturer's screws five times in a clockwise direction. The average measured torque, standard deviation, bias, and coefficient of variation were calculated and compared accordingly. RESULTS: Wrenches from six manufacturers demonstrated excellent accuracy for measurements at the center of the beam (bias within ± 4%). For measurements at 90°, equipments from five manufacturers displayed excellent accuracy (bias within ± 7%), and seven showed excellent repeatability (coefficient of variation ≤ 2%). CONCLUSION: The scale should be aligned with the center of the beam and read from 90° while using a torque wrench. The accuracy and repeatability torques generated by the wrenches differed according to the manufacturer, scale width, scale line width, beam width, and distance between the scale and beam center. Based on these results, we suggest that a torque wrench must be selected after determining the difference in the structure of the torque wrench.

Dental implant care and trouble among dependent patients based on the questionnaire survey among Japanese dental practitioners.

BACKGROUND: Self-care and professional care of implants may prove difficult for elderly people who require nursing care. However, the actual state of care and problems remains unknown. In this study, we investigated the actual state of implant problems in elderly people living in their own home or in a nursing home who received visiting dental treatment. METHODS: We mailed questionnaire survey forms to 2339 representatives or specialists who were members of the Japanese Society of Oral Implantology, the Japanese Society of Gerodontology or the Japan Prosthodontic Society. We narrowed down the respondents to those who provided visiting dental treatment, and analyzed the actual state of implants observed during visiting dental treatment (type, care, problems, countermeasures, etc.). RESULTS: Of the 924 dentists who responded to the questionnaire survey, 291 (22%) provided visiting dental treatment. While the majority of implant types encountered in the previous 12 months were root-form implants, there were still a certain number of blade and subperiosteal implants. Daily implant care involved mostly cleaning with a toothbrush + auxiliary tools. The most frequent implant problems encountered in the past were difficulty in cleaning and peri-implantitis. Medication and antiphlogistic treatment were most frequently adopted as countermeasures to implant problems, followed by observation. When we classified the results into those for the dentists who provided implant treatment and those for the dentists who did not, we found that many of the dentists who did not provide implant treatment opted for observation or medication, while those who provided implant treatment also implemented removal of superstructure, retightening of screws, repair and so forth. CONCLUSIONS: We found that many of the implant troubles encountered by dentists who provided visiting dental care were difficulty in cleaning or peri-implantitis, and that the actions taken against these troubles varied depending on the experience of the dentist performing the implant treatment. Our study also revealed that dentists who provide visiting dental care need to acquire knowledge and skills of implant treatment, to have actions prepared in case they encounter such cases, or to closely coordinate with dentists who specialize in implants.

Implant treatment in ultra-aged society.

Implant therapy is gaining presence as a prosthodontic treatment option. However, the graying of the population has led to an increase in the number of older adults requiring special consideration in implant treatment because of their systemic health problems. Additionally, with the growth of the elderly population in need of long-term care, a greater number of older adults who have received implant treatment are receiving long-term care, raising various issues that need to be addressed. In the present review article, we describe the significance of implant treatment in older adults, issues when performing implant treatment in geriatric patients, and measures to be taken when implant patients have lapsed into a state of requiring long-term care. In addition, in view of population aging, we propose an approach for applying implant treatment to older adults. This approach includes using an appropriate type of implant system depending on the remaining life expectancy and the patient's general condition, performing less invasive surgery, providing treatment using prosthetic appliances that are easy to manage and can be modified, and ensuring oral health management by providing an Implant Card to patients when the treatment is completed.

A preliminary report on dental implant condition among dependent elderly based on the survey among Japanese dental practitioners.

BACKGROUND: The objective of this study was to ascertain the situation relevant to implants, the status of oral self-care, the status of aftercare provided by the dentist who placed the implant, and the usage status of the implant card, in homebound or institutionalized older adults who are receiving home-visit dental care due to the inability to visit a dental clinic on their own. METHODS: A survey questionnaire was sent by post mail to 2339 people who are representative members or dental specialists belonging to any of the following three academic societies: Japanese Society of Oral Implantology, Japanese Society of Gerodontology, and Japan Prosthodontic Society. The survey questions asked were about provision/no provision of implant treatment, provision/no provision of home-visit dental care, the situation of patients after implant treatment, the situation of implants in the context of home-visit dental care, and the usage status and recognition of the implant card. RESULTS: No less than 30% of the dentists had patients who were admitted to the hospital or became homebound after receiving implant treatment at their clinic. Twenty-two percent of the dentists had been consulted about the implants. Dentists who continued to provide post-operative implant care through home-visit dental care accounted for approximately 80%. On the other hand, however, 40% of the dentists did not know the post-implantation status of their implant patients. Of the patients receiving home-visit dental care, approximately 3% had implants (identified mainly by visual inspection). It was found that more than 50% of the dentists offering implant treatment did not use the implant card, and even in cases where it was used, most of the cards were not in the standardized format. CONCLUSIONS: Within the limitation of low response rate to the questionnaire in this preliminary study, we concluded that many of practitioners including specialists indicated the need of universal record of implant for dependent elderly cares.

Fabrication of a customized tray for preventing fracture of isolated abutment teeth in definitive casts.

Isolated abutment teeth with advanced bone resorption on definitive casts for a partial removable dental prosthesis can fracture when the definitive cast is removed from the impression or during subsequent laboratory procedures. This report describes a technique that avoids fracture of the definitive cast during its fabrication. A separating line is formed on the custom tray, which enables removal of the definitive cast without fracturing the isolated tooth. In addition, if the cervical line is sharp and appears compromised, then the impression can be trimmed at the clinical cervical line to enlarge the abutment diameter and increase its resistance to fracture without altering the shape of critical areas.

Influence of denture supporting tissue properties on pressure-pain threshold--measurement in dentate subjects.

PURPOSE: The present study was designed to clarify the relationship between the properties of the palatal mucosa and the pressure-pain threshold. METHODS: Three parts of the palatal mucosa of 17 dentate subjects were measured: the median part of the palate, the lateral part of the first molar, and the midpoint between these two parts. The subjects were instructed to press a pushbutton when he or she felt pressure-pain. The probe pressure was gradually increased (1N/s). The thickness (T) (mm) and elasticity (E) (MPa) were used as the parameters of the properties of the palatal mucosa, whereas pressure (P) (MPa), compressibility (C) (%), and subsidence (S) (mm) were used as the parameters of the pressure-pain threshold. The Shapiro-Wilk test was used to consider the data of distribution of normality for each measurement point, as obtained from the 17 subjects. A Kruskal-Wallis test and a Wilcoxon signed rank test were performed for multiple comparisons, the Bonferroni method was used to compensate for the P-value. Spearman's rank correlation coefficient was calculated. RESULTS: T correlated with the values of S at the median points (P=0.001) and midpoints (P=0.011). CONCLUSION: Thickness can be an index of the amount of relief where pain is caused easily. In addition, modulus of elasticity is important as an indicator of the bearing ability of denture support tissues, it is necessary to consider how to evaluate the modulus of elasticity and to evaluate the relationship between the parameters of the pain threshold.