Relationships of physical constitution with occlusal force and masticatory performance in adults with natural dentition.

This study aimed to clarify whether physical constitution affects masticatory function. A total of 251 healthy adults with completely natural dentition participated in this study. Height, weight, and body mass index (BMI) were used as parameters representing physical constitution, and the amount of glucose eluted from chewed gummy jelly and maximum occlusal force was used as parameter representing masticatory function. Handgrip strength was also measured. After comparing each parameter between male and female participants, the relationship between physical constitution and masticatory function was investigated in the combined (male and female) group, the male group, and the female group. The relationship between handgrip strength and masticatory function was also investigated. Stepwise multiple linear regression analysis was performed with masticatory function as the dependent variable and physical constitution as independent variable. The mean values of each parameter were significantly greater in the male group than in the female group. Regarding the relationship between physical constitution and occlusal force, the occlusal force tended to increase as the parameter value representing physical constitution increased, and a significant correlation was observed for all parameters. For masticatory performance, a significant correlation was observed in all parameters in the combined group, but no significant correlations were observed in the male group and in the female group. Multiple linear regression analysis showed that weight was significantly associated with occlusal force. Though occlusal force may be affected by physical constitution, masticatory performance is not easily affected by physical constitution.

Relationship between age and occlusal force in adults with natural dentition.

This study aimed to clarify the relationship between age and occlusal force in adults with natural dentition. A total of 385 adults (180 males and 205 females) with natural dentition participated in this study. Subjects were asked to perform maximum clenching for approximately 3 s, and the occlusal forces on both sides and habitual chewing side were calculated using a dental prescale. Regression analysis was performed by sex with occlusal forces on both sides and habitual chewing side as the dependent variable and age as the independent variable. In addition, all subjects were divided into three groups: young group (20-39 years), middle group (40-59 years), and old group (60 years and over), and the occlusal forces on both sides and habitual chewing side were compared among the three groups. The occlusal forces did not differ from 20 to 60 years old for both males and females, and the occlusal forces gradually decreased after 60 years old. The curve of the polynomial equation was the most suitable. The occlusal forces on both sides and the habitual chewing side were similar in the young and middle groups, and the values of the old group were significantly smaller than those of the other two groups. From these results, it was suggested that the occlusal force of adults with natural dentition does not differ from 20 to 60 years old and can be represented by a curve of a cubic polynomial, and it significantly decreases after 60 years old.

Usefulness of newly devised food intake score in removable denture wearers.

BACKGROUND: Although the food intake score (FIS) from conventional food intake questionnaires is widely used, the evaluation method, number of foods and food selection used in the questionnaire can be improved. OBJECTIVE: This study aimed to evaluate the usefulness of a newly devised FIS in removable denture wearers. METHODS: A total of 219 removable denture wearers were asked about their food intake, and three types of FIS (FIS1, FIS2 and FIS3) were calculated as subjective parameters. FIS1 and FIS2 are conventional FISs, while FIS3 is the FIS devised in this study. The amount of glucose extracted (AGE) when participants chewed gummy jelly was used as an objective parameter. The relationship between the three FISs and that between each FIS and AGE were investigated. Stepwise multiple linear regression analysis was performed with AGE as the dependent variable and age, sex and FIS as independent variables. RESULTS: The three types of FISs were positively correlated. A positive correlation was also found between FIS and AGE. The correlation coefficient was the largest in FIS2 and decreased in the order of FIS3 > FIS1; however, the values of FIS2 > FIS3 were similar. Multiple linear regression analysis revealed that sex and FIS were significantly associated with AGE. CONCLUSION: For denture wearers, the newly devised FIS3 was useful and evaluated masticatory performance, as well as or better than FIS1 and FIS2.

Stability of masticatory movements after placement of implant-supported denture.

The purpose of this study was to clarify the stability of masticatory movement after placement of implant-supported denture. Fourteen patients (patient group) with mandibular implants denture and maxillary complete denture and 30 dentate adults (control group) were asked to chew a boiled fishpaste, and the masticatory movement was recorded using MKG. For the 10 cycles beginning with the 5th cycle of mastication, the parameters representing the stability of masticatory movement were calculated. Data collected at 1, 3, 6, 9 months and 1, 2, 3 years after insertion of implants denture were compared between sessions and also between the patient and control groups. The mean and standard deviation of the values in the patient group at 1 month after insertion of implants denture were large, but gradually decreased 6 to 9 months after insertion of implants denture. Each parameter maintained almost the same value from 1 to 3 years. The parameter values of the patient group were significantly larger than those of control group from 1 to 9 months after insertion of implants denture, but 1 year after insertion of implants denture, there was no significant difference between the two groups in 5 out of 7 parameters. From these results, it was suggested that a certain duration, about 9 months to 1 year, was necessary for patients with implants denture to adapt to the new masticatory function and that the timing of functional evaluation should be set to 1 year after insertion of implants denture.

Gender differences in masticatory function in elderly adults with natural dentition.

The purpose of this study was to clarify the presence or absence of gender differences in masticatory function in elderly adults with completely natural dentition. Fifty-six elderly adults aged 65 years and older (elderly group) and 60 young adults in their 20-40 s (young group) with natural dentition participated in this study. The maximum occlusal force on the habitual chewing side was measured using dental prescale. Next, the amount of glucose extraction when subjects chewed a gummy jelly on their habitual chewing side for 20 s was measured. The maximum occlusal force and masticatory performance in the elderly and young groups were compared between males and females. The relationship between the maximum occlusal force and masticatory performance was also investigated. The maximum occlusal force in the elderly and young groups was larger in males than in females, and the difference was significant. The amount of glucose extraction in the elderly and young groups was higher in males than in females, and the difference was significant. Regarding the relationship between the maximum occlusal force and the amount of glucose extraction, there was a significant positive correlation. These results suggest that there are gender differences in the masticatory function of the elderly adults with completely natural dentition, and these differences need to be noted in the evaluation of masticatory function.

Comparison of two dental prescale systems used for the measurement of occlusal force.

The purpose of this study was to clarify the relationship between two types of dental prescale systems. Forty healthy subjects were asked to maximally clench for about 3 s, and the maximum occlusal force before and after cleaning was calculated using an Occluzer FPD707 for dental prescale (P1) and a bite force analyzing system for dental prescale II (P2). The maximum occlusal forces measured by P1 and P2 were compared before cleaning and after cleaning. Next, the relationship between the maximum occlusal force by P1 and maximum occlusal force by P2 was investigated. In addition, comparisons were made between males and females. The maximum occlusal force after cleaning was significantly smaller than before cleaning for both P1 and P2. The reduction rate of the occlusal force was 4.1% for P1 and 25.9% for P2. Significant linearity was observed between the maximum occlusal forces of P1 and P2 (regression linear equation: y = 1.191x - 30.521, r = 0.980, p < 0.001). The maximum occlusal forces measured by P1 and P2 were both significantly larger in males than in females. It was suggested that there was a certain relationship between the maximum occlusal forces measured by dental prescale and dental prescale II, suggesting that it is possible to compare the results of both by applying corrections using a regression equation.

Changes in mandibular movement during chewing of different hardness foods.

In order to clarify the change in mandibular movement during chewing of foods with different hardness, 20 healthy subjects were asked to chew 3 types of gummy jellies (containing 6, 8, and 10% gelatin), and the masseter muscular activity and the mandibular movement were recorded. The indicators representing the muscular activity (integral value of masseter muscular activity), the mandibular movement (opening distance, masticatory width, cycle time, opening maximum velocity and closing maximum velocity), and the stability of masticatory movement were calculated, respectively, and compared among the three foods. The integral value of masseter muscular activity was smallest for the 6% gelatin and significantly increased in order as the content of gelatin increased to 8, 10%. The value of each indicator for the mandibular movement increased gradually as the food got harder. The value for all indicators was significantly larger for the 10 than the 6%. However, between the two foods, no significant change was observed for the several indicators. The mean ratio of the 10% gelatin to the 8% gelatin for the cycle time was extremely small, being 1.01, but was between the range of 0.89-1.07 showing aspects of changes within each individual. The other indicators showing small ratio were similar in this aspect. The parameters representing stability of movement showed the lowest values for the 8% gelatin. It was suggested that the hardness of food affected mandibular movement during mastication, but the movement changed variously according to the hardness and exerted muscular activities.

Relationship between masticatory performance using a gummy jelly and food intake ability in Japanese complete denture wearers.

Twenty patients wearing complete dentures were asked to chew a gummy jelly, and their glucose extraction was measured. Two types of masticatory scores (MS1 and MS2) were calculated using a food intake questionnaire. The relationship between masticatory scores and glucose extraction was investigated. The values of masticatory scores were large when the amount of glucose extraction was also large, and there were significantly positive correlations between the two. There was also a positive correlation between MS1 and MS2. It was suggested that the food intake ability was high when the masticatory performance using a gummy jelly was high.

Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism.

PURPOSE: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects. METHODS: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant. RESULTS: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups. CONCLUSIONS: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

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.

Validity of analysis of masticatory movement using a two-dimensional mandibular movement recording device.

To clarify the validity of analysis of masticatory movement using a two-dimensional (2D) mandibular movement recording device, masticatory movements (pattern of movement path, opening distance, masticatory width, and cycle time) were compared between simultaneous recordings made by 2D and three-dimensional (3D) devices in healthy adults. The 2D device can perform the same level of mandibular movement analysis as the 3D device if the distance between LED and camera is fixed (15 cm), and the findings indicated the suitability of the 2D device for clinical application.

Usefulness of the masticatory score by occlusal support.

This study aimed to clarify the usefulness of masticatory score by occlusal support. A total of 605 adults were classified into four groups (A1, A2A3, B, and C) according to the Eichner classification, and the relationship between the amount of glucose eluted and masticatory score was investigated in each group. A significant correlation between the glucose eluted and masticatory score was observed in groups A2A3, B, and C, but not in A1, suggesting that the masticatory score is useful for evaluating the masticatory performance of complete denture wearers, but not adults with natural dentition.

Path pattern and movement during mastication on habitual and non-habitual chewing sides.

PURPOSE: To clarify the presence or absence of differences in path pattern and movement during mastication between the habitual and non-habitual chewing sides. METHODS: Participants were 225 healthy adults with natural dentition. Mandibular movement while chewing gummy jelly on each side was recorded, and masticatory path pattern was classified into five types (one normal and four abnormal). The frequency of each pattern was measured and compared between chewing sides. The amount, rhythm, velocity, and stability of movement and masticatory performance were measured and compared between chewing sides. RESULTS: A normal pattern was observed on the habitual chewing side in 84.4% of participants. There was a significant difference between chewing sides in masticatory path pattern (χ2 = 35.971, P < 0.001). Values of parameters regarding the amount and velocity of movement and masticatory performance were significantly higher on the habitual chewing side. Values of parameters regarding rhythm and stability of movement were significantly lower on the habitual chewing side. CONCLUSION: The present findings of functional differences between chewing sides in terms of path pattern and movement during mastication suggest that these factors should be analyzed on the habitual chewing side.

Masticatory performance with one missing molar.

PURPOSE: This study aimed to evaluate masticatory performance in cases where one molar was missing. METHODS: Participants were 156 adults with one molar missing from their natural teeth, who were divided into group A (without prosthetic treatment) and group B (with prosthetic treatment). The non-missing side was designated as A1 or B1, and the missing side was designated as A2 or B2. The amount of glucose eluted (AG) when the participants chewed a gummy jelly was measured and used as a parameter for masticatory performance. AG was compared between the non-missing side (A1, B1) and missing side (A2, B2), and between the first molar missing group and second molar missing group. RESULTS: AG was significantly greater on the dentate side (P < 0.001) and was significantly less in the A2 group when the first molar was missing (P = 0.002). The rate of decrease of AG was 11.1%, 14.3%, and 8.4% in groups A+B, A, and B, respectively. CONCLUSION: Masticatory performance appears to decrease even with only one missing molar. Although improvement is achieved by prosthetic treatment, performance remains inferior to that on the dentate side.

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.

Effect of denture treatment on masticatory movement in patients with complete dentures.

PURPOSE: To clarify the effect of denture treatment on masticatory movement in patients with complete dentures. METHODS: Forty eight patients who required new complete dentures and 20 patients who were satisfied with their original complete dentures (control: C group) participated in this study. Subjects were asked to chew a gummy jelly on their habitual chewing side. The movement of mandibular incisal point was recorded using a mandibular kinesiograph. First, average path and overlap of the movement path were displayed for the ten cycles between the fifth cycle and the fourteenth cycle. The movement path was classified into one of seven patterns and the frequency of each pattern was calculated and investigated the relationship between treatment and masticatory path pattern. Next, opening distance and masticatory width (spatial parameter) and cycle time (temporal parameter) were calculated and compared between the before treatment group (BT group) and after treatment group (AT group), and between the AT and C groups. RESULTS: The BT group showed various patterns of masticatory path, whereas the majority of subjects in the AT and C groups showed path patterns that were representative of healthy dentate subjects. The opening distance and masticatory width increased, and the cycle time was shortened after wearing new complete denture, and there were no statistically significant differences between AT group and C group. CONCLUSIONS: From these results it was suggested that the masticatory movement of patients with complete dentures improved greatly after wearing new denture.

Section showing minimal intra-individual variations in masticatory movement.

PURPOSE: To clarify the section showing minimal intraindividual variations in the movement of the mandibular incisal point during mastication of softened chewing gum. METHODS: Twenty healthy subjects were asked to chew softened chewing gum on the habitual side for 20 seconds. The change in the spatial parameters (gape and masticatory width) and temporal parameter (cycle time) were investigated for 20 cycles from the first cycle. The coefficients of variation of these parameters were investigated for each of 10 consecutive cycles (first to eleventh series). RESULTS: The spatial and temporal parameters were maximal at the first cycle, decreased progressively until the fourth or fifth cycle, and then remained almost unchanged thereafter. The coefficients of variation of the parameters were maximal during the first series, decreased progressively until the fourth to sixth series, and then tended to increase gradually thereafter. Minimal coefficients of variation were observed during the fifth and sixth series for the gape, during the fifth series for the width, and during the fourth series for the cycle time. CONCLUSION: These results suggest that the ten cycles after the fourth to the sixth cycle was the section showing minimal intra-individual variations in the masticatory movement during the chewing of softened chewing gum.

[Planning guidelines for prosthodontic treatment].

In recent years "practice guidelines" based on EBM techniques have even been attracting attention at a societal level, and guidelines modeled after the procedure for preparing practice guideline (described at http://www.niph.go.jp/glgl-4.3rev.htm) have begun to be drafted and made public. With the aim of ensuring the quality and presenting the basic concepts of prosthodontic therapy, the Japan Prosthodontic Society, which bears a great obligation and responsibility toward society and the Japanese public, has decided to undertake the formulation of guidelines related to prosthodontic therapy, and decided to first undertake the formulation of "Practice guideline for denture relining and rebasing", and to prepare a guideline model. We tried to prepare the guidelines according to the "Procedure for preparing practice guidelines", but because of the scientific uniqueness of prosthodontic treatment and dentistry, research to elucidate the basis of treatment has been insufficient, and we ultimately reconfirmed the current state of affairs in which it is difficult to perform. We therefore prepared the guidelines based on the limited evidence obtained in a search of the scientific literature and on the consensus of experts. The Japan Prosthodontic Society has investigated and prepared a Society guideline "model" to the extent possible at the present time, and it has prepared "Guidelines for adhesion bridge" and "Practice guidelines for denture prosthodontics" based on it. Nevertheless, the fact of the matter is that we are faced with numerous problems, and we think that in the future new bases and clinical knowledge will be accumulated by promoting scientific clinical research, and that the guidelines should be revised regularly based on them.

Masticatory performance and oral health-related quality of life before and after complete denture treatment.

PURPOSE: To clarify the relationship between masticatory performance and oral health-related quality of life (OHRQoL) before and after complete denture treatment. METHODS: Thirty patients wearing complete dentures were asked to chew a gummy jelly on their habitual chewing side, and the amount of glucose extraction during chewing was measured as the parameter of masticatory performance. Subjects were asked to answer the Oral Health Impact Profile (OHIP-J49) questionnaire, which consists of 49 questions related to oral problems. The total score of 49 question items along with individual domain scores within the seven domains (functional limitation, pain, psychological discomfort, physical disability, psychological disability, social disability and handicap) were calculated and used as the parameters of OHRQoL. These records were obtained before treatment and 3 months after treatment. Each parameter of masticatory performance and OHRQoL was compared before treatment and after treatment. The relationship between masticatory performance and OHRQoL was investigated, and a stepwise multiple linear regression analysis was performed. RESULTS: Both masticatory performance and OHRQoL were significantly improved after treatment. Furthermore, masticatory performance was significantly correlated with some parameters of OHRQoL. The stepwise multiple linear regression analysis showed functional limitation and pain as important factors affecting masticatory performance before treatment and functional limitation as important factors affecting masticatory performance after treatment. CONCLUSIONS: These results suggested that masticatory performance and OHRQoL are significantly improved after treatment and that there is a close relationship between the two. Moreover, functional limitation was found to be the most important factor affecting masticatory performance.

Masticatory performance of the elderly as seen from differences in occlusal support of residual teeth.

PURPOSE: To clarify whether the occlusal state affects the masticatory performance of elderly adults. METHODS: Elderly women were asked to chew a gummy jelly, and the amount of glucose extraction was measured as the parameter for masticatory performance. Subjects were divided into five groups depending on occlusal support on the habitual chewing side (G1: no occlusal support of posterior teeth, G2: occlusal support of first premolar, G3: occlusal support of premolars, G4: occlusal support from first premolar to first molar, and G5: occlusal support from first premolar to second molar). It was also investigated whether or not the subjects were wearing dentures. The amount of glucose extraction was compared among the five groups and then between subjects with removable denture and subjects without removable denture. The relationship between age and glucose extraction were also investigated. RESULTS: The amount of glucose extraction progressively increased with increase in number of occlusal support. There were no fixed tendencies between age and glucose extraction, when occlusal state was taken into account. The amount of glucose extraction of subjects without removable denture was significantly larger than that of subjects with removable denture. It was also found that 67 % of subjects with removable denture were within the normal range when it was set based on G5 data. CONCLUSIONS: It was suggested that the occlusal state affected the masticatory performance of elderly adults.