Decreased oral function in Japanese inpatients with schizophrenia

AIM

Oral function in patients with schizophrenia has not been well-characterized. To address this, we performed a cross-sectional study of oral function in Japanese inpatients with schizophrenia.

METHODS

We measured oral function, including occlusal force, tongue-lip motor function, tongue pressure, and masticatory function in 130 Japanese inpatients with schizophrenia. We then compared the frequency of clinical signs of oral hypofunction among 63 non-elderly and 67 elderly inpatients with schizophrenia, as well as data from 98 elderly control participants from a previous Japanese study.

RESULTS

The frequency of reduced occlusal force was significantly higher in the elderly inpatients (76.2%) than in the non-elderly inpatients (43.9%) and elderly controls (43.9%). The frequency of decreased tongue-lip motor function in non-elderly inpatients (96.8%) and elderly inpatients (97.0%) was significantly higher than that in elderly controls (56.1%). The frequency of decreased tongue pressure in non-elderly inpatients (66.1%) and elderly inpatients (80.7%) was significantly higher than that in elderly controls (43.9%). Finally, the frequency of decreased masticatory function was highest in elderly inpatients (76.5%), followed by non-elderly inpatients (54.8%) and elderly controls (15.3%).

CONCLUSION

Oral function was decreased in both non-elderly and elderly Japanese inpatients with schizophrenia compared with elderly controls.

A Preliminary Report of Maximum Voluntary Bite Force of Young Indian Population

Introduction

The measurement of bite force is increasingly gaining importance in dentistry. This preliminary report evaluates the maximum voluntary bite force (MVBF) of young healthy individuals with normal occlusion and correlates the effect of age and gender with the maximum bite force (MBF).

Materials and Methods

405 participants in the age group of 18 to 40 years were selected from the outpatient department meeting inclusion and exclusion criteria. MVBF was measured with the help of a digital device called "Byte" at incisors, right first molar, and left first molar region.

Results

There was a strong correlation between age with bite force. Bite force increased with age. Males had more bite force than females. The posterior region had higher bite force than the anterior region.

Conclusion

Measurement of bite force is very important for every patient undergoing restorative treatment. The "Byte" device was found to be very efficient.

Guillain-Barré Syndrome Presenting With Masticatory Disturbance and Reduction in Bite Force

Guillain-Barré syndrome is a rare, rapidly progressive, and potentially fatal immune-mediated neuropathy. A 17-year-old male patient with a fever of 38°C developed masticatory impairment a few days later. Although the fever resolved after one week, the restricted mouth opening and decreased bite force persisted. Thirty-five days after disease onset, the patient was referred to our clinic and reported severe masticatory dysfunction due to a significant reduction in maximum bite force (left: 0 N, right: 12.7 N). His maximal mouth opening was 24 mm without jaw deviation. An electrophysiological study revealed Guillain-Barré syndrome (acute motor axonal neuropathy). The patient was closely monitored as he underwent rehabilitation comprising mouth opening and mastication training. The patient's bite force and masticatory impairment due to the weakness of the muscles of mastication gradually improved. At one year and five months after disease onset, the masticatory impairment had fully resolved. His maximum bite force two years after disease onset was 158.3 N on the left side and 172.2 N on the right side.

Relationship between occlusal force and psychological frailty in Japanese community-dwelling older adults: The Septuagenarians, Octogenarians, Nonagenarians Investigation with Centenarians study

BACKGROUND

Frailty increases the risk of negative health-related events, such as falls, disability, hospitalizations, and death. Although the association between oral health and physical frailty is well established, the relationship between oral health and psychological frailty has not yet been investigated. Therefore, we conducted a cross-sectional study to examine the association between maximal occlusal force and psychological frailty in Japanese community-dwelling older adults.

METHODS

Psychological frailty was defined as a World Health Organization-5 scale (WHO-5) score of <13, cognitive and functional status was defined as a Japanese version of the Montreal Cognitive Assessment (MoCA-J) score of <23, and psychological robustness was defined as a WHO-5 score of ≥13 and a MoCA-J score of ≥23. We used a cross-sectional study design to measure maximal occlusal force in 1810 participants, and examined the following factors relevant to psychological frailty: educational level, financial status, living situation, history of chronic diseases, handgrip strength, and instrumental activities of daily living. We used propensity score matching to match the psychological frailty and psychological robustness groups according to demographic and confounding factors. This process, resulted in 344 participants, of whom 172 were in the psychological frailty group and 172 were in the psychological robustness group. In the matched cohort, differences between groups with and without psychological frailty were compared using generalized estimating equations for maximal occlusal force after adjusting for the number of teeth.

RESULTS

After controlling for potential confounding factors of frailty, the psychological frailty group showed lower maximal occlusal force compared with the psychological robustness group (unstandardized regression coefficients = -72.7, 95% confidence interval: -126.3 to -19.1).

CONCLUSIONS

Maximal occlusal force was associated with a reduced prevalence of psychological frailty among Japanese community-dwelling older adults participating in our study.

Elucidation of the relationship between masticatory muscle activity and masticatory movement. Report 1. Mechanism of occlusal force generation

OBJECTIVES

The purpose of this study was to elucidate how masticatory muscles are involved in the generation of occlusal force.

MATERIALS AND METHODS

The experiment was conducted by fabricating an experimental apparatus for a unilateral occlusion model with the masticatory muscles imparted. The experimental apparatus was fabricated by enlarging the lateral photograph of a dried adult skull specimen 3.5 times larger than that of a standard adult and drawing the outlines of the maxilla and mandible, canines and molars of the upper and lower jaws, and temporomandibular joint on a wooden board. The masticatory muscles used in the experiment were the masseter muscle, the temporalis muscle (anterior and posterior muscle bundles), and the lateral pterygoid muscle. For the measurement of the contractile force of the masticatory muscle, we used the spring scale. For the food, we used cut plastic cylinders.

RESULTS

The results of the experiment revealed the following: First, the occlusal force was generated under the condition that the contraction forces of all the masticatory muscles were balanced. Second, when the occlusal force was applied to food, the occlusal planes of the upper and lower jaws were parallel. Third, the occlusal force occurred perpendicular to the occlusal plane. Fourth, the occlusal force was generated with a force greater than the contraction force of the individual masticatory muscles. And finally, even if occlusal force was applied to the food, the occlusal force did not load the temporomandibular joint.

CONCLUSION

Occlusal force is not generated by the action of a single masticatory muscle but under the balanced contractile force of all masticatory muscles. The occlusal force then emerges with a force greater than the contraction force of all the masticatory muscles, and its direction occurs perpendicular to the occlusal plane.

Masseter muscle cross-sectional area and late implant failure: A case-control study

INTRODUCTION

Occlusal overload is considered to be one of the causes of late implant failure. However, it is unclear whether the magnitude of the patient's occlusal force is a risk factor for late implant failure.

PURPOSE

This case-control study aimed to clarify the association between the cross-sectional area (CSA) of the masseter muscle and late implant failure.

METHODS

This case-control study was limited to implant-supported fixed prostheses. We compared cases with at least one late implant failure (n = 25 patients) to controls (n = 82 patients) without implant failure. Patients were matched by age, sex, year of surgery, jaw and tooth type, and bone graft. Log-rank and Cox proportional hazard regression analyses were used to identify possible risk factors for late implant failure.

RESULTS

The incidence of late implant failure was significantly associated with masseter muscle CSA ≥504.5 mm² (hazard ratio: 4.43; 95% CI: 1.82-10.79; p < 0.01).

CONCLUSION

Higher masseter muscle CSA increases the risk of late implant failure.

Evaluation of automatic cleaning in analysis of occlusal force

This study aimed to clarify the usefulness of automatic cleaning in analysis of occlusal force. The maximum occlusal force was calculated in 151 healthy adults before cleaning (B), after manual cleaning (M), and after automatic cleaning (A) and compared among the three conditions. The absolute value of the error rate of A, based on M, was calculated. The occlusal forces in M and A were similar and significantly smaller than the occlusal force in B. The absolute error rate of A was 2.4%. These results suggest that automatic cleaning has a similar effect to manual cleaning and can be applied clinically.

Quantitative parameters of digital occlusal analysis in dental implant supported restorative reconstruction recent 5 years: a systematic review

OBJECTIVE

The aims of this systematic review were to evaluate the clinical masticatory performance of implant-supported restorations, observe the occlusal force changes in the distribution of the implant restoration and reveal the positive and negative contributing factors of implant design and components based on the outcomes of digital occlusal measurement.

MATERIAL AND METHODS

An extensive search was conducted through PubMed and CENTRAL to identify clinical trials on implant-retained restorations using digital occlusal analysis methods. Two researchers assessed the identified studies and data extraction independently, and the data synthesis strategies without meta-analysis that summarizes the effect estimates were adopted.

RESULTS

The search screened 3821 titles and abstracts, then full-text analysis for 26 articles was performed, and 14 studies were included in the quantitative synthesis. Four of six studies for implant-retained overdenture showed statistically significant improved bite force when immediate loading (p = .00045, .00005, .00055, and .00005, respectively), and no statistically significant results in the other two studies (p = .225, .371, respectively.) However, the results of the favoured intervention were not statistically significant (p = .104, .166, respectively) in two studies of single posterior implant restorations. In all three studies, the bite force distributed on the implant prostheses of partially fixed implant-retained restoration increased statistically significantly (p = .013, .001, .05, respectively).

CONCLUSIONS

The edentulous restoration supported by implants seems to significantly improves bite force and chewing efficiency compared with conventional dentures. Regular quantitative occlusal measurement is recommended to avoid the possible risk of overload. Smaller implants size and relatively small and flexible attachment designs may be more conducive to the stability and retention of the restoration of atrophy of alveolar bone.

Usefulness and Validity of a Jaw-Closing Force Meter in Older Adults

We prototyped a new device with a soft and flexible pressure sensor to measure the force to close the mandible with or without occlusal support (jaw-closing force, JCF). This study aimed to clarify the practicality of this instrument. Healthy young and older adults with occlusal support were recruited. Intra- and inter-rater reliability of the JCF meter was examined using data from younger participants. Data regarding age, sex, body mass index, remaining teeth, and dentures of the older adults were obtained. Furthermore, the right and left JCFs were measured using a JCF meter; occlusal force was measured using an existing occlusal force-measuring device. Intra- and inter-rater correlation coefficients were significantly reproducible (0.691−0.811, p < 0.05). JCF was correlated with occlusal force (p < 0.05). Multiple regression analysis revealed that factors significantly associated with JCF included denture status (p < 0.001), age (p = 0.038), and occlusal force (p = 0.043). The prototyped JCF meter can measure JCF with high reproducibility, reliability, and validity. Further, association with occlusal force, which is an existing index, was observed. This device could be used to measure the JCF with or without occlusal support as a new method of evaluating oral function in older adults.

The correlation between two occlusal analyzers for the measurement of bite force

Background

Occlusal force represents masticatory function. Using quantifiable occlusal indicators provides a more objective occlusal force evaluation. In the recent dental practice, digital methods such as the Dental Prescale II (DP2, GC Corp., Tokyo, Japan) and T-scan (T-Scan III v8; Tekscan Inc.) are commonly used in clinics to evaluate treatment outcomes. The T-scan provides the relative bite force (%) compared to the maximal bite force on individual teeth or the unilateral arch. The DP2 can quantify occlusal force, measured in newtons (N), on the half arch or the overall bite, but it is difficult to identify the bite force on an individual tooth. It is difficult to select a device that fulfils all the requirements to record occlusal force. This study aimed to investigate the association between the bite measured by the DPS2 and T-scan to determine whether the measured bite force is comparable through calculation.

Methods

A total of 80 healthy adults, including 41 women and 39 men with a mean age of 38.2, were requested to bite pressure sensitive film sheets ten minutes apart. Linear regression analysis was used to estimate the measured bite force by the DP2 and T-scan.

Results

There was a significant positive correlation between the occlusal force measured by the DP2 and T-scan (P < 0.01) when intercept was equal to zero as confounders were adjused. These results provided the comparability of the measured occlusal forces determined by the DP2 and T-scan.

Conclusion

The estimated bite force determined by DP2 and T-Scan is convertible using the linear equation from this study to increase the value for clinical applications. The estimated bite force from the two quantifiable occlusal indicators are comparable. The two commercially available quantifiable occlusal indicators can be fully adapted to all clinical requirements according to this result.

Effects of Interval Walking Training on Oral Health Status in Middle-Aged and Older Adults: A Case-Control Study

The purpose of this study was to determine the effect of walking training "Interval Walking Training (IWT)" on oral health status. Participants were divided into two groups: an exercise intervention group and a non-intervention group (control). The intervention group consisted of 59 subjects (20 males, 39 females) aged 50 years or older who participated in the IWT program in Matsumoto from 2019 to April 2022. The control group consisted of 33 subjects (14 males and 19 females) aged 50 years or older who have visited Niigata University Medical and Dental Hospital and agreed to participate in the study. The intervention group underwent walking training (interval walking training) for at least 5-6 months. The walking training consisted of five sets of fast walking above 70% peak aerobic capacity for walking (VO₂peak) for 3 min, followed by 3 min of slow walking at ~40% VO₂ peak per day for more than four days/week. The oral health status was evaluated for the number of teeth, occlusal force, salivary occult blood, masticatory performance, and tongue pressure. A total of 57 participants were analyzed in the intervention group (18 males and 39 females, age: 66.7 ± 0.8 (mean ± S.E.) years) and 33 participants in the control group (14 males and 19 females, age: 74.5 ± 1.1 (mean ± S.E.) years). There were no significant differences in gender, salivary occult blood, tongue pressure, masticatory performance, or occlusal force between the two groups at the start of the intervention (p = 0.36, p = 0.48, p = 0.42, p = 0.58, and p = 0.08, respectively by unpaired t-test or χ² test). On the other hand, there were significant differences in age and BMI, with a trend toward lower age and higher BMI in the intervention group (p < 0.001 and p < 0.001, respectively, by unpaired t-test). In terms of rate of change, the intervention group showed a significant increase in occlusal force (F = 4.5, p = 0.04, ANCOVA) and a significant decrease in BMI (F = 7.3, p = 0.009, ANCOVA). No significant differences were observed in the other measured items. It was found that walking training in both middle-aged and older people does not only affect the physical aspect of weight loss but may help maintain and improve the occlusal force.

Factors affecting masticatory performance during the mixed dentition period

BACKGROUND

During the mixed dentition period, masticatory performance may temporarily decline as deciduous teeth are replaced by permanent teeth. This may lead to an insufficient intake of chewy foods.

OBJECTIVES

This study aimed to clarify the characteristics of factors that affect masticatory performance during the dentition exchange period.

METHODS

The participants were 229 students in grades 4-6 who were in the lateral dentition exchange period. Shearing performance (SP) was evaluated using gummy jelly, and mixing performance (MP) was evaluated using color-changing gum. The chewing rate, occlusal force and area, number of teeth, Hellman's tooth age, Rohrer index, grip strength, and walking speed were also evaluated. The χ² test, Mann-Whitney test, Spearman's rank correlation coefficient, and a generalized linear model were used for statistical analysis.

RESULTS

SP/MP showed a significant positive correlation with occlusal force, occlusal contact area, and chewing rate for gummy jelly and gum but there was a difference in the strength of the correlation between boys and girls. Chewing rate for gummy jelly and gum showed a significant relationship with both SP and MP, suggesting that masticatory performance is higher with slower chewing. Maximum occlusal force was selected as a significant independent variable for SP, and Rohrer index was selected as a significant independent variable for MP. When the occlusal force was higher and the Rohrer index was lower, the masticatory performance tended to be higher.

CONCLUSIONS

Our results suggest that masticatory performance during the dentition exchange period is higher with slower chewing and a stronger occlusal force, which may be related to obesity.

Assessment of Occlusal Force and Local Gas Release Using Degradable Bacterial Cellulose/Ti3C2Tx MXene Bioaerogel for Oral Healthcare

Dental diseases resulting from movement disorders and volatile gases are very common. The classic method for detecting occlusal force is effective; however, its function is one-time rather than real-time monitoring, and the technology is very time-consuming. Herein, we report a multifunctional, flexible, and degradable bacterial cellulose/Ti₃C₂T_x MXene bioaerogel for the accurate detection of occlusal force and early diagnosis of periodontal diseases. Combining the mechanical properties of MXene and the abundant functional groups of bacterial cellulose, 3D porous bioaerogels exhibit both pressure-sensitive and ammonia (NH₃)-sensitive responses. By integrating these substances into a flexible array, the resulting device can distinguish the intensity, location, and even the time sequence of the occlusion force; moreover, it can provide NH₃ gas and occlusion force response signals. Therefore, this technology is promising for both disease diagnosis and oral health. In addition, the introduction of a renewable biomaterial allows the bioaerogel to degrade completely using a low-concentration hydrogen peroxide solution, making the device environmentally friendly and satisfying the demands for sustainable development.

Effect of prosthetic framework material, cantilever length and opposing arch on peri-implant strain in an all-on-four implant prostheses

Aim

To evaluate the effect of prosthetic framework material and cantilever length on peri-implant strain in mandibular all-on-four implant-supported prostheses with different types of arch antagonist forces.

Materials and Methods

Models simulating a completely edentulous mandibular arch fabricated in heat-cured acrylic resin were used. On the acrylic models, four implants were placed at regions 34, 32, 42, and 44 simulating all-on-four implant placements. Implant-supported screw-retained fixed prosthesis frameworks were fabricated using three different materials (cobalt-chromium, zirconia, and polyetheretherketone) and with three different cantilever lengths (zero mm, 15 mm, and 25 mm). Strain gauges were attached on the model at the buccal and lingual positions of each implant. Forces simulating opposing natural dentition, conventional complete denture, and the parafunctional habit were applied to the models. The peri-implant strain in each strain gauge was recorded.

Results

Least peri-implant strains (67 microstrains) were observed when forces simulating conventional complete dentures were applied on the models and the highest peri-implant strains (9091 microstrains) were observed when forces simulating parafunctional habit were applied. One-way ANOVA test followed by Tukey's post hoc analysis was performed to compare the mean deformation scores between different materials at 50 N load. The level of significance [P-value] was set at P < 0.05. Tests showed significant differences between zero mm and the other types in all the different materials, and also between 1.5 x AP and 2.5 x AP for Zirconia and Peek material at P = 0.02 & P = .008, respectively. The results showed that the type of framework material, cantilever length, and occlusal forces from the opposing arch influence the peri-implant strain in the bone in all-on-four implant-supported prostheses.

Conclusion

Rehabilitation of a single, completely edentulous arch with implant-supported prostheses should consider the situation of the opposing arch. The choice of framework material, as well as the cantilever length, should be altered based on the forces from the opposing arch.

A robotic chewing simulator supplying six-axis mandibular motion, high occlusal force, and a saliva environment for denture tests

Six-axis motion is essential for the evaluation of the wear failure modes of dental prostheses with complete teeth morphologies, and a high occlusal force capacity is vital for static clenching and dynamic bruxism. Additionally, the saliva environment influences abrasive particles and crack growth. The present research was aimed at the development of a six-axis masticatory and saliva simulator with these capacities. The masticatory simulator was designed based on a six-axis parallel mechanism, and the saliva simulator consisted of a saliva circuit and a temperature control loop. A control system of the masticatory and saliva simulators was constructed. The operating interface includes a centric occlusal position search, a static test, a dynamic test, a saliva supply, and data reporting. The motion and force performances of the masticatory simulator were evaluated. The flow rate and temperature change of the saliva simulator were calculated. For the occlusal position-searching, the driving amplitude is linear with the moving variables during minor one-axis motion. For the static tests, the force capacity of the driving chain is 3540 N, while for the dynamic tests, the force capacity is 1390 N. The flow rate of the saliva is 0.18-51.84 mL/min, and the saliva can effectively wet the prosthesis without the risk of overflow. Moreover, the saliva temperature can increase from room temperature (23°C) to body temperature (37°C) in about 6 min. The proposed DUT-2 simulator with six-axis motion, high force, and a salvia environment provides an in vitro testing approach to validate numerical simulation results and explain the clinical failure modes of prostheses. The centric occlusal position-searching, static tests, and dynamic tests could therefore be executed using a single testing machine. Moreover, the proposed device is more compact than previously reported six-axis masticatory simulators, including the Bristol simulator and DUT-1 simulator.

Impact of occlusal force on decline in body mass index among older Japanese adults: Finding from the SONIC study

OBJECTIVES

To determine any independent influence of occlusal force and of number of natural teeth on decline in body mass index (BMI) among older Japanese adults.

DESIGN

Longitudinal study over a 3- to 6-year period.

SETTING

Urban and rural area in Japan.

PARTICIPANTS

Independently living Japanese adults aged 69-71 years and 79-81 years at baseline. This analysis excluded participants who were defined as underweight at baseline.

MEASUREMENTS

Information was collected on age, gender, occlusal force, the number of teeth, BMI, socioeconomic factors, medical history, the number of daily prescription medications, cognitive function, depressive symptoms, hand grip strength, and physical function. Maximal occlusal force was measured with a pressure-sensitive sheet. Nutritional status was assessed using BMI, and participants with BMI <21.5 were defined as underweight. Then, they were divided into two groups: a "BMI declined" group who were defined as underweight at either 3- or 6-year follow-up survey, and a "BMI maintained" group who were not defined as underweight at both follow-up surveys. Logistic generalized estimating equation (GEE) models were used to assess the effect of occlusal force and the number of teeth at baseline on decline in BMI over 3 or 6 years, after adjusting for possible covariates associated with nutritional status.

RESULTS

The final analysis included 704 participants. Eighty-six (12.2%) participants were classified into the BMI declined group. Logistic GEE models showed that the number of teeth was not significantly associated with decline in BMI. However, occlusal force was significantly associated with decline in BMI (odds ratio = 0.90, 95% confidence interval = 0.83-0.97) after adjusting for covariates.

CONCLUSION

Participants with lower occlusal force were more likely to be in the BMI less than 21.5 kg/m² . The findings suggest that to prevent decline in oral function is important to maintain nutritional status.

Development of a Wearable Mouth Guard Device for Monitoring Teeth Clenching during Exercise

Teeth clenching during exercise is important for sports performance and health. Recently, several mouth guard (MG)-type wearable devices for exercise were studied because they do not disrupt the exercise. In this study, we developed a wearable MG device with force sensors on both sides of the maxillary first molars to monitor teeth clenching. The force sensor output increased linearly up to 70 N. In four simple occlusion tests, the trends exhibited by the outputs of the MG sensor were consistent with those of an electromyogram (EMG), and the MG device featured sufficient temporal resolution to measure the timing of teeth clenching. When the jaw moved, the MG sensor outputs depended on the sensor position. The MG sensor output from the teeth-grinding test agreed with the video-motion analysis results. It was comparatively difficult to use the EMG because it contained a significant noise level. Finally, the usefulness of the MG sensor was confirmed through an exercise tolerance test. This study indicated that the developed wearable MG device is useful for monitoring clenching timing and duration, and the degree of clenching during exercise, which can contribute to explaining the relationship between teeth clenching and sports performance.

Evaluation of occlusal force and masticatory performance in elderly adults with natural dentition unaffected by occlusal support

PURPOSE

This study aimed to clarify whether occlusal force and masticatory performance reduced in elderly adults and whether these parameters were affected by age.

METHODS

Seventy-eight elderly adults (elderly group) and 76 young adults (control group) with natural dentition were asked to maximally clench for 3 s, and occlusal force was calculated. The amount of glucose extraction after chewing a gummy jelly was measured as the parameter for masticatory performance. Occlusal force and masticatory performance were compared between the elderly and control groups. The correlation between age and occlusal force and between age and masticatory performance was also investigated.

RESULTS

Occlusal force was significantly smaller in the elderly group (P < 0.05). Masticatory performance was lower in the elderly group, but this difference was not statistically significant. No significant correlation was observed between age and occlusal force in the control group, but a negative correlation was found in the elderly group (P < 0.05). No significant correlation was found between age and masticatory performance in either group.

CONCLUSION

Occlusal force was affected by age and reduced significantly, whereas masticatory performance was not affected by age and was maintained in elderly adults.

Relationship between two pressure-sensitive films for testing reduced occlusal force in diagnostic criteria for oral hypofunction

OBJECTIVE

To measure the occlusal force in the same group of patients with the Dental Prescale 50H type R and the Dental Prescale II, examine the association between them, and determine the reference value for Dental Prescale II that corresponds to the 50H type R 200 N reference value used to make a diagnosis of oral hypofunction.

BACKGROUND

Reduced occlusal force, a measure of frailty in older persons, was previously determined with Prescale 50H type R pressure-sensitive film, but it has been replaced by the Prescale II.

MATERIALS AND METHODS

The study participants were 441 men and women aged ≥ 65 (mean, 71.8 ± 5.3) years. The occlusal force was measured with the two different types of pressure-sensitive film, and their association was examined. Receiver operating characteristic curves for the Prescale II measured values were created with the 200 N reference value used for the 50H type R film as the cut-off value.

RESULTS

The analysis set included 391 participants for whom measurements were obtained using both the 50H type R and the Prescale II. Linear regression analysis produced regression equations, and a ROC curve analysis provided reference values of 500 N for the Prescale II (without pressure filter) and 350 N for the Prescale II (with pressure filter).

CONCLUSION

In occlusal force tests for making a diagnosis of oral hypofunction, reference values for the Prescale II (without pressure filter) and for the Prescale II (with pressure filter) were determined. The findings suggested that the Prescale II can be used as a diagnostic examination for oral hypofunction.

The effect of occlusal splints on the mechanical stress on teeth as measured by intraoral sensors

PURPOSE

Whether it is possible to prevent mechanical stress on teeth via an occlusal splint remains to be clarified. This study aimed to assess the same by simultaneously recording the occlusal pressure and strain on the teeth in humans.

METHODS

Eleven participants (five women and six men; mean age 25.7 years) were enrolled in this study. Hard and soft oral appliances were fabricated for the maxillary arch of each participant. The strain on the four target teeth (right maxillary and mandibular first premolars, and first molars) and occlusal pressure were concurrently measured, while the participants performed maximum voluntary teeth clenching under each condition (hard, soft, or no occlusal splint).

RESULTS

Compared to the absence of an occlusal splint, hard occlusal splints generated less strain on molar teeth but more strain on premolar teeth, while soft occlusal splints did not lower the strain on all target teeth significantly.

CONCLUSION

Considering the limitations of this study, hard occlusal splints should be used for the protection of molar teeth but for premolar teeth caution is required and depends on the case. On the other hand, soft occlusal splints may not have any benefit for the protection of either type of teeth for patients exhibiting excessive occlusal pressure.

Effects of Neuromuscular Electrical Stimulation Synchronized with Chewing Exercises on Bite Force and Masseter Muscle Thickness in Community-Dwelling Older Adults in South Korea: A Randomized Controlled Trial

This study is aimed at investigating the effects of synchronized neuromuscular electrical stimulation (NMES) and chewing exercises on bite force and the masseter muscle thickness in community-dwelling older adults. Material and methods: Forty older adults were enrolled in South Korea and randomly assigned to either an experimental or control group. The experimental group performed chewing exercises using the No-Sick Exerciser equipment synchronized with NMES applied to the bilateral masseter muscles, while the control group performed only chewing exercises. Both groups received interventions for 20 min/day, 5 days/week, for 6 weeks. Bite force was measured using the OCCLUZER device, and masseter muscle thickness was measured using a portable ultrasound. Results: Both groups showed a significant increase in bite force and masseter muscle thickness compared to baseline measurements (p < 0.05). The experimental group showed a significantly higher increase in bite force and masseter muscle thickness than the control group after combined intervention (p < 0.05). Conclusion: This study demonstrates that NMES synchronized with chewing exercises is more efficient in increasing bite force and masseter muscle thickness than chewing exercises alone in community-dwelling older adults.

Relationship between oral function and mandibular anterior crowding in early mixed dentition

The position of the dentition is considered to be determined by a combination of forces exerted by the perioral muscles and tongue. We hypothesized that mandibular anterior crowding may be related to abnormalities in the development of oral function. To determine the relationship between oral function and mandibular anterior crowding in early mixed dentition. A total of 61 children (30 boys, 31 girls) with early mixed dentition were included in this study. Height, body weight, maximum occlusal force, lip‐closing strength, and maximum tongue pressure were measured in all participants, and their dental casts and lateral cephalograms were evaluated. Little's irregularity index (LII), evaluated by dental casts, was used as an indicator of mandibular anterior crowding. Maximum occlusal force and lip‐closing strength were not significantly correlated with the LII, although they were positively correlated with maximum tongue pressure, mandibular intercanine perimeter distance, and upper central incisor (U1)‐to‐NL angle (p < .05). Maximum tongue pressure was negatively correlated with LII (p < .05). Maximum tongue pressure and LII were significantly positively correlated with the mandibular intercanine perimeter distance and U1/NL angle, and negatively correlated with the interincisal angle (p < .05 for all). Crowding of the mandibular anterior teeth was directly correlated with tongue pressure function and indirectly correlated with maximum occlusal force and lip‐closing strength.

Association between myotonometric measurement of masseter muscle stiffness and maximum bite force in healthy elders

BACKGROUND

Maximum bite force (MBF) is a common and useful index of masticatory function; it correlates with physical strength in elderly people. Palpation of stiffness in the masseter muscle during forceful biting has been considered to be associated with MBF. However, this assessment method relies on subjective judgments; no study has verified the relationship between MBF and quantitative measurements of masseter muscle stiffness (MMS).

OBJECTIVE

We aimed to verify the association between masseter muscle myotonometric assessment results and MBF.

METHODS

In total, 117 community-dwelling >65-year-old individuals from the Tokyo metropolitan area were assessed. MMS on the dominant side during forceful biting was measured with a MyotonPRO device. Masseter muscle thickness (MMT) during rest and forceful biting was measured with an ultrasonic diagnostic apparatus, and the difference in MMT (DMMT) between the rest and forceful biting conditions was determined. MBF data were obtained with a pressure-sensitive sheet and an associated device. To determine the independent variables affecting MBF and MMS, multivariate linear regression analyses with adjustments for age, sex and number of teeth were performed.

RESULTS

The multivariate analysis revealed that MBF correlated with the number of teeth (β = .489, P < .001) and MMS (β = .259, P = .003) (R²  = .433). MMS correlated with MBF (β = .308, P = .003) and DMMT (β = .430, P < .001) (R²  = .326).

CONCLUSION

Masseter muscle stiffness possibly reflects a force generated by the masseter muscle during forceful biting. Therefore, MMS is effective to assess tooth loss as well as an index of masseter muscle strength when evaluating MBF.

Factors associated with masticatory performance in community-dwelling older adults: A cross-sectional study

BACKGROUND

Decreased masticatory performance leads to deterioration of overall health among older adults. However, maintaining and improving masticatory performance in ways other than maintenance of natural teeth and appropriate prosthodontic treatment remains unclear. If the factors related to the mixing and shearing abilities for masticatory performance are clarified, it may be possible to maintain and improve the masticatory performance of older adults. We aimed to clarify the association among mixing ability, shearing ability, and masticatory performance-related factors.

METHODS

Of the 707 community-dwelling older adults in Kusatsu Town, Japan, 344 who had been treated for any dental defects were enrolled in this study. Masticatory performance was evaluated on the basis of mixing ability and shearing ability. The number of natural teeth and artificial teeth, occlusal force, tongue pressure, and oral diadochokinesis /ta/ were measured as masticatory performance-related factors. Their relationship with mixing ability, shearing ability, and masticatory performance-related factors was examined by means of Spearman rank correlation coefficient and path analysis.

RESULTS

Among masticatory performance-related factors, the number of natural teeth, occlusal force, and tongue pressure were directly associated with both mixing ability and shearing ability. Moreover, mixing ability was also directly associated with shearing ability.

CONCLUSIONS

Tongue pressure, which can be improved by means of training, is a masticatory performance-related factor associated with both mixing and shearing abilities.

PRACTICAL IMPLICATIONS

Training for tongue pressure after proper prosthetic treatment may provide an effective means of maintaining and improving masticatory performance in older adults.

Oral function and vertical jump height among healthy older people in Japan

OBJECTIVE

Vertical jump height and oral function affect the general muscle condition. This study aimed to evaluate the association between vertical jump height and oral function among healthy older individuals.

BASIC RESEARCH DESIGN

Cross-sectional analytic study.

PARTICIPANTS

231 independent older people (mean age, 74.4 ± 5.6 years) who participated in the Kyoto Elders Physical Fitness Measurement Research Project. Individuals with partial or complete edentulousness who did not use a prosthetic device or complained of oral/maxillofacial pain were excluded from the study.

INTERVENTIONS

Grip strength was measured using a Smedley Hand Dynamometer. To measure masticatory performance, the participants were instructed to chew a gummy jelly on their habitual chewing side (left or right) for 20 s. Occlusal force, contact area, and pressure were also assessed.

MAIN OUTCOME MEASURES

The outcome variable was vertical jump height. The predictor variables were physical status (age, body mass index, and grip strength), oral status (number of present teeth and denture use), and oral function (masticatory performance, occlusal force, occlusal contact area, occlusal pressure, and tongue pressure). These relationships were evaluated with univariate analysis, and then multiple regression analysis was performed with age as the covariate for each male and female participant.

RESULTS

Vertical jump height was significantly associated with grip strength in both men and women. Moreover, in women, it was associated with masticatory performance, occlusal force, and occlusal contact area.

CONCLUSIONS

Vertical jump height was closely associated with oral function among healthy older women.

Is a History of Falling Related to Oral Function? A Cross-Sectional Survey of Elderly Subjects in Rural Japan

Background: Deteriorated physical function makes older adults prone to fall, and it is therefore known to prompt elders to require long-term care. In this regard, oral function can be related to the loss of motor function. This cross-sectional study assessed the oral factors that increase the risk of falling among older adults. Methods: We surveyed 672 self-reliant elderly individuals aged ≥65 years who were dwelling in a rural area. We assessed each subject’s risk of falling and any related anxiety. Oral-related conditions (number of teeth, occlusal support, masticatory performance, occlusal force, and tongue pressure) and physical motor functions (gait speed, knee extension force, and one-legged standing) were also assessed. Statistical analyses were performed using Mann-Whitney’s U-test, the χ² test, and a logistic regression model. Results: In all subjects, 23% had a history of falling, while 40% had anxiety over falling. Both factors were significantly higher among female subjects, who also had slower gait speeds, and greater lateral differences in occlusion. The subjects with histories of falling were older, had impaired physical motor function, and exhibited a decrease in occlusal force and left/right occlusal imbalances. We recognized similar trends for anxiety about falling. Conclusions: These results revealed that the risk of falling might be lessened by maintaining healthy teeth occlusion and promoting healthy oral function.

Occlusal trauma inhibits osteoblast differentiation and bone formation through IKK-NF-κB signaling

BACKGROUND

Occlusal trauma is an important factor promoting bone loss caused by periodontal diseases. Although there are reports of traumatic force promoting bone resorption in periodontal diseases, no studies examining the inhibition of bone formation by traumatic force and the underlying mechanism have been reported. The aim of this study was to investigate the mechanism whereby traumatic force inhibits bone formation.

METHODS

MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without stimulation with Pg. LPS. The expression of osteoblast markers and the activation of IKK-NF-κB signaling were evaluated in vitro. Then, MC3T3-E1 cells were induced to undergo osteogenic differentiation and subjected to cyclic uniaxial compressive stress with or without IKK-2 Inhibitor VI. The expression of osteoblast markers was determined. Then, the classic Wnt signaling pathway (β-catenin, Gsk3β, p-Gsk3β, and Dkk1) was further evaluated in vitro. Finally, occlusal trauma was induced in Wistar rats with or without the injection of IKK-2 Inhibitor VI, to evaluate changes in bone mass and IKK-NF-κB and Wnt/β-catenin signaling in vivo.

RESULTS

After stimulation with Pg. LPS and traumatic force, IKK-NF-κB signaling was significantly activated in vitro. The expression of osteoblast markers and the activity of alkaline phosphatase in MC3T3-E1 cells declined after traumatic force loading and were rescued when IKK-NF-κB signaling was blocked. Wnt/β-catenin signaling was accordingly inhibited upon force loading, but this inhibition was reversed when IKK-NF-κB was antagonized in vitro. X-ray and Micro-CT analysis of the mandibles of the rats as well as HE and TRAP staining showed that bone loss induced by occlusal trauma declined after IKK-NF-κB was inhibited. The expression of p65 and IκBα was increased when occlusal trauma was induced in Wistar rats, whereas β-catenin, OCN, and Runx2 levels were decreased. After blocking IKK-NF-κB, significant upregulation of β-catenin, OCN, and Runx2 was observed in rats suffering from occlusal trauma.

CONCLUSIONS

IKK-NF-κB signaling could be activated by traumatic force or occlusal trauma. Its activation promoted the degradation of β-catenin, ultimately inhibiting osteogenic differentiation in vitro and bone formation in vivo.

Simultaneous Measurement of Ear Canal Movement, Electromyography of the Masseter Muscle and Occlusal Force for Earphone-Type Occlusal Force Estimation Device Development

We intend to develop earphone-type wearable devices to measure occlusal force by measuring ear canal movement using an ear sensor that we developed. The proposed device can measure occlusal force during eating. In this work, we simultaneously measured the ear canal movement (ear sensor value), the surface electromyography (EMG) of the masseter muscle and the occlusal force six times from five subjects as a basic study toward occlusal force meter development. Using the results, we investigated the correlation coefficient between the ear sensor value and the occlusal force, and the partial correlation coefficient between ear sensor values. Additionally, we investigated the average of the partial correlation coefficient and the absolute value of the average for each subject. The absolute value results indicated strong correlation, with correlation coefficients exceeding 0.9514 for all subjects. The subjects showed a lowest partial correlation coefficient of 0.6161 and a highest value of 0.8286. This was also indicative of correlation. We then estimated the occlusal force via a single regression analysis for each subject. Evaluation of the proposed method via the cross-validation method indicated that the root-mean-square error when comparing actual values with estimates for the five subjects ranged from 0.0338 to 0.0969.

Radiographic changes of trabecular bone density after loading of implant-supported complete dentures: A 3-year prospective study

BACKGROUND

Bone tissues may undergo remodeling under functional mechanical stimuli.

PURPOSE

This prospective study on implant-supported fixed complete dentures (IFCDs) evaluated the radiographic trabecular bone changes in density by means of gray levels and texture analysis variables after up to 3-year loading.

MATERIALS AND METHODS

The sample consisted of digital periapical radiographs of 63 distal implants of hybrid IFCDs installed in 30 patients (22 women, mean age of 62 ± 7.8 years). Digital periapical radiographs were taken after prosthesis installation, and 1 and 3 years after IFCD loading. Longitudinal images of each implant were superimposed, and the same regions of interest were selected for measurement of gray levels statistics (mean gray levels, SD, and coefficient of variation [CV]) and texture parameters (correlation, contrast, entropy, and angular second moment). Data were analyzed by mixed regression models.

RESULTS

Mean gray levels increased for 1 year (P < .05), for 3 years (P < .01) and for maximum bite force (P < .01). The interaction between bruxism and time in 1 year was significant (P < .01) for a decrease in CV. No significant effect of texture analysis variables was found (P > .05).

CONCLUSIONS

The results suggest an increase of radiographic bone density as measured by an increase in mean gray levels and a decrease in CV in IFCD distal implants up to 3 years of loading.

Changes in oral health-related quality of life after oral rehabilitation with dental implants in patients following mandibular tumor resection

Oral rehabilitation with prosthodontic treatment considerably influences the well-being and quality of life of patients after ablative oral tumor surgery. This study evaluated the effects of implant-supported prostheses (ISPs) on oral health-related quality of life (OHRQoL) and chewing ability in 10 patients who requested ISPs after mandibular oral tumor resection. OHRQoL was assessed using the Japanese version of the Oral Health Impact Profile (OHIP-49) before and one year after ISP placement. Chewing ability, including self-assessed masticatory ability and occlusal force, was examined at one year after ISP placement. The initial mean total OHIP-49 score of 65.3 ± 9.79 decreased to 46.0 ± 8.14 at one year after ISP placement. Mean OHIP-49 score decreased in all domains, whereas self-assessed masticatory ability increased within one year of ISP placement. There were no significant differences between prosthesis types with respect to the mean OHIP-49 score or self-assessed masticatory ability. In conclusion, ISP placement improves OHRQoL and the self-assessed masticatory ability. Moreover, the prosthesis type might not significantly affect OHRQoL.

Occlusion accuracy of restorations and removable partial dentures fabricated using the impression under occlusal force with functionally generated path recording

To evaluate the occlusion accuracy of a novel impression technique, excessively high occlusion and the occlusal contact area during lateral movements were compared between metal restorations (restorations) and removable partial dentures (RPDs) fabricated using conventional and novel techniques. Both restorations and RPDs were fabricated on the simulation model with the precise displacement of the remaining teeth and soft tissue. For the novel technique, functionally generated path (FGP) recording and impression under occlusal force were simultaneously performed using a custom tray with an FGP table. For the two conventional techniques, definitive casts were mounted on an average value articulator and a semi-adjustable articulator in the typical manner. Prostheses were placed on the simulation models, and excessively high occlusion in the intercuspal position and occlusal contact areas during lateral movements were measured. Statistical analyses were performed using Kruskal-Wallis and Steel-Dwass tests (α = 0.05). For both prostheses, conventional techniques showed significantly higher occlusion in the intercuspal position than the novel technique. Moreover, the new technique demonstrated better guidance contact during lateral movements than conventional techniques. This novel technique can be recommended for the fabrication of highly accurate prostheses with appropriate occlusal contact without corrections at delivery.

Head position affects the direction of occlusal force during tapping movement

Despite numerous reports describing the relationship between head position and mandibular movement in human subjects, the direction and magnitude of force at the occlusal contacts have not been investigated in relation to head position. The objective was to investigate the effect of head position on the direction of occlusal force while subjects performed a tapping movement. Twenty-three healthy adult subjects were asked to sit on a chair with their back upright and to perform 15 tapping movements in five different head positions: natural head position (control); forward; backward; and right and left rolled. The direction and magnitude of force were measured using a small triaxial force sensor. The Wilcoxon signed-rank test and Bonferroni test were used to compare head positions in each angle of the anteroposterior axis direction and the lateral axis direction with respect to the superior axis. The force element in the anteroposterior axis shifted to the forward direction in the head position pitched backward, compared with control, pitched forward and rolled left positions (P = .02, <.01 and <.01, respectively). The force direction in the lateral axis with the head position rolled to the right or left shifted to the left and right directions, respectively, compared with those in the other positions (P < .05). Results of this study suggest that the head should be maintained in a position in which a stable tapping movement can be performed in a relaxed position without anteroposterior and lateral loading.

Fabrication of a screw-retained hybrid prosthesis following treatment of peri-implant defects: a case report

The etiology of marginal bone loss around osseointegrated implants is primarily based on the biomechanical and/or microbial factors. If stresses and strains around dental implants under functional loading conditions are expected to exceed the physiologic tolerance thresholds of the alveolar bone, the fixed hybrid prosthesis might be a more reliable treatment of choice instead of fixed metal ceramic restorations. The purpose of this article is to report the 1-year follow-up of the periodontal and prosthetic rehabilitation of a patient who has presented with symptoms of peri-implantitis due to incorrectly planned implant supported fixed metal ceramic bridge which was later replaced with screw-retained hybrid prosthesis following the treatment of peri-implant defects. Treatment helped to maintain patient’s self-confidence and comfort, as well as favorable masticatory function. Rehabilitation with screw retained hybrid prosthesis is an ideal treatment of choice for maxillomandibular skeletal discrepancies.

Does the presence of an occlusal indicator product affect the contact forces between full dentitions?

Studies have explored occlusal marking interpretation, repeatability and accuracy. But, when an occlusion detection product is interposed between teeth, direct tooth-tooth occlusal contact relationships are replaced by tooth-material-tooth structures. Thus, the marks cannot reflect the original contacts. This has been shown for single tooth pair contacts. The purpose of this laboratory study was to similarly examine full dentitions. A dentiform was set into Class I centric occlusion with the mandible supported by a load cell. The maxillary arch was guided by precision slides. As the weighted (~52 N) upper assembly was lowered onto and raised off the mandibular arch, the loads on the mandible were measured. With and without (control) occlusal marking material, the steps were as follows: (cleaning - control 1 - material 1) … (cleaning - control 6 - material 6). The six materials were as follows: Accufilm I and II, Rudischhauser Thick and Thin, Hanel Articulating Silk and T-Scan. Then, the six sets of (cleaning - control - material) measurements were repeated with the mandibular assembly shifted, in turn, by 0·1 mm in the Anterior, Posterior, Right and Left directions. The five (Centric and four 0·1 mm shifted) occlusal relationships produced grossly different tooth-tooth (control) load profiles. And, in general, these controls were affected, in different ways, by the marking products. Among the five conventional products, the Rudischhausers fared the worst and the electronic T-Scan was an extreme outlier. Thus, in general, popular occlusal detection products alter the occlusal contact forces, and therefore, their markings cannot characterise the actual occlusion.

Evaluation of the effects of modified bonded rapid maxillary expansion on occlusal force distribution: A pilot study

Objective:

To evaluate the effects of modified bonded rapid maxillary expansion (RME) on occlusal force distribution.

Materials and Methods:

The sample included 12 patients (7 girls and 5 boys; mean age: 13.1 years) at the permanent dentition stage with bilateral posterior cross-bite. The patients were treated with a modified bonded RME appliance, activated twice a day. The study was terminated when the palatal cusps of the maxillary posterior teeth were occluding with the buccal cusps of the mandibular posterior teeth. The postretention period was 3 months. The T-Scan III device was used to analyze the percentages of occlusal force distribution, and records were taken at the pretreatment (T1), the postreatment (T2), and the postretention (T3) periods. Wilcoxon signed rank test was used for statistical analyses.

Results:

Incisors were most frequently without contact, followed by canines. The highest forces were seen in the second and first molar regions. A significant decrease was seen in total occlusal force during treatment (T1–T2); however, during retention, the force returned to its initial value, and no significant differences were found (T1–T3). No differences were found between right and left sides and in occlusal forces of the teeth in all time periods.

Conclusion:

The use of modified bonded RME decreases the total occlusal forces during the treatment period, but it does returns to its initial value after the postretention period.

The effects of salivas on occlusal forces

Contacting surfaces of opposing teeth produce friction that, when altered, changes the contact force direction and/or magnitude. As friction can be influenced by several factors, including lubrication and the contacting materials, the aim of this study was to measure the occlusal load alterations experienced by teeth with the introduction of different salivas and dental restorative materials. Pairs of molar teeth were set into occlusion with a weighted maxillary tooth mounted onto a vertical sliding assembly and the mandibular tooth supported by a load cell. The load components on the mandibular tooth were measured with three opposing pairs of dental restorative materials (plastic denture, all-ceramic and stainless steel), four (human and three artificial) salivas and 16 occlusal configurations. All lateral force component measurements were significantly different (P < 0·0001) from the dry (control) surface regardless of the crown material or occlusal configuration, while the effects of the artificial salivas compared to each other and to human saliva depended on the crown material.

Prevalence of torus mandibularis among a group of elderly Japanese and its relationship with occlusal force

OBJECTIVE

To examine the prevalence of torus mandibularis (TM) and identify clinical factors associated with its presence.

MATERIALS AND METHODS

A total of 664 Japanese adults over age 60 were studied by means of a questionnaire and clinical examination.

RESULTS

In all, 197 subjects (29.7%) had TM. We found a significant association between the presence of TM and torus palatinus (TP; 45.1% vs. 26.5%, p<0.001). Moreover, occlusal force with TM was significantly higher than without TM (p<0.05). Logistic regression adjusted for age and occlusal force revealed a significant relationship between TM and occlusal force and TP [p=0.005, odds ratio (OR)=2.44; p<0.001, OR=2.66, respectively].

CONCLUSION

This study suggests that there is a relationship between TM and factors related to occlusal factor.

Occlusal function associated with body composition in premenopausal Japanese women

OBJECTIVES

The goal of the present study was to investigate the relationship between occlusal function and body composition in 108 premenopausal healthy Japanese women aged 20-45 years.

METHODS

Pressure-sensitive sheets were used to measure occlusal function. Whole fat mass and lean mass, fat-free mass, and whole-bone mineral content were measured by dual-energy X-ray absorptiometry (DXA).

RESULTS

After being adjusted for age and the square of height, the whole lean mass and grip strength of the large occlusal contact-area group were found to be significantly higher than those of the small occlusal area groups (p<0.05, respectively). In the 1-year follow-up study, changes in weight in the small-occlusal contact-area group and the low-occlusal force group were significantly larger than other occlusal-contact area or occlusal-force groups. The mean occlusal-contact area and occlusal force were both significantly smaller in subjects with partial dentures than in those without (p<0.05).

CONCLUSION

Large occlusal contact-area, high occlusal force, and no dentures may be associated with some good health conditions in premenopausal Japanese women.