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.

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.

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.

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.

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.

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.

Masticatory path pattern and masticatory performance while chewing gummy jelly.

The purpose of this study was to clarify masticatory path pattern and masticatory performance during gummy jelly chewing. A total of 235 healthy adults were asked to chew gummy jelly for 20 s on each side, and the masticatory movement was recorded using a Motion Visi-Trainer (MVT V1). Next, the amount of glucose extraction was measured as a parameter of masticatory performance. The masticatory path was classified into one of five patterns newly devised: normal pattern (N, opening: straight or concave, closing: convex) and abnormal patterns (A1-A4). The number of occurrences of each pattern was investigated and compared by sex and path pattern. Next, masticatory performance was compared between the normal pattern and the abnormal patterns by sex. Pattern N was the most frequently expressed in 346 cases out of 470 cases (73.6%), followed by patterns A1, A4, A2, and A3 in that order. Regarding the number of patterns observed, pattern N was the most common in both sexes, followed by pattern A1, with no significant difference between sexes. The amount of glucose extraction in each pattern was the highest in pattern N for both sexes, followed by A2 and others in that order, and a significant difference was observed between the normal pattern and the abnormal patterns. From these results, the existence of sex difference in masticatory path patterns during gummy jelly chewing was not proven, and that masticatory performance was higher with normal patterns than with abnormal patterns.

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.

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.

Gender difference in masticatory performance in dentate adults.

PURPOSE: To clarify whether there might be a gender difference in masticatory performance in dentate adults. METHODS: Thirty male subjects and thirty female subjects were asked to chew gummy jelly on their habitual chewing side for 10, 15 and 20s and the amounts of glucose extraction were measured. The changes of both glucose extraction and standardized glucose extraction from 10 to 20s were investigated differently for males and females. The amount of glucose extraction was compared between males and females for each chewing duration. In addition, in order to confirm a gender difference in occlusal force, the maximum occlusal force was compared between males and females. RESULTS: For both males and females, the amount of glucose extraction was lowest for 10-s chewing and increased significantly for 15-s and 20-s chewing. The mean standardized glucose extraction values increased in proportion with the duration of chewing. The standard deviations of the standardized glucose extraction were very small (below 0.02) for all chewing durations in both males and females. With regard to comparison of the glucose extraction between males and females, the amount of glucose extraction was significantly larger for males than for females for all chewing durations. The maximum occlusal force was significantly larger for males. CONCLUSION: It was suggested that it might be important to take into consideration gender-related differences while analyzing masticatory performance in dentate adults.

Influence of two masticating conditions on assessment of movement path stability.

PURPOSE: The purpose of this study was to clarify whether differences in masticating conditions affected masticatory path stabilities of healthy subjects and TMD patients. METHODS: Twenty healthy female subjects as the healthy group, and 20 female Temporomandibular Disorders (TMD) patients as the TMD group, were selected. Incisal point movement of during mastication of both masticating condition 1 (mc1; crispy bread chewed until swallowing on the free side) and masticating condition 2 (mc2; softened chewing-gum chewed for 20s on the habitual side) were recorded by MKG. As for mc1, out of all cycles during mastication only those cycles on the habitual chewing side were analyzed. As for mc2, the ten cycles from the fifth cycle were analyzed. For these analyzed sections, the indicators representing movement path stability were calculated and compared between the two groups. RESULTS: As for mc1, though the values of the indicators representing path stability were larger for the TMD group, there were cases where no significant differences were found between the two groups. As for mc2, the values were significantly larger for the TMD group (SDs; P<0.05, SD/ODs; P<0.01). CONCLUSIONS: From these results, it was suggested that the differences in masticating conditions affected the assessment of masticatory path stabilities of healthy subjects and TMD patients and the conditions should be considered for analyzing masticatory movement.

Differences in masticatory function of subjects with different closing path.

PURPOSE: The purpose of this study was to clarify whether there was a difference in the masticatory function between two masticatory path patterns: a convex closing path and a concave closing path. METHODS: For 80 healthy subjects, the masticatory function (masticatory muscular activity, mandibular movement, and masticatory performance) when chewing a gummy jelly was recorded. Out of the 160 chewing cases (80 subjects chewing on either side), 65 cases (Group I) in which the incisal point opened in a linear or concave manner toward the working side and closed in a convex manner, and 15 cases (Group II) in which the opening path was the same as that in Group I, but the closing followed a concave path, were selected. For the masticatory function, the integral values per unit time of masseter and temporal muscular activities, the gape and masticatory width, the indicators representing the stability of movement path, and the glucose extraction from chewing gummy jelly were measured and compared between the two groups. RESULTS: The integral values of muscular activities and the amount of glucose extraction were significantly greater in Group I. The gape and masticatory width were not significantly different between the groups. The values of the indicators representing the stability of path were smaller in Group I than in Group II. CONCLUSION: From these results, it was suggested that there was a functional difference between Group I (with a convex closing path) and Group II (with a concave closing path), and that Group I had a superior masticatory function to Group II.

Masticatory path pattern during mastication of chewing gum with regard to gender difference.

PURPOSE: To clarify the masticatory path patterns of the mandibular incisal point during mastication of softened chewing gum with regard to gender difference. METHODS: One hundred healthy subjects (50 males and 50 females) were asked to chew softened chewing gum on one side at a time (right side and left side) and the movement of the mandibular incisal point was recorded using MKG K6I. After a catalog of path patterns was made, the movement path was classified into one of the pattern groups, and then the frequency of each pattern was investigated. RESULTS: A catalog of path patterns consisting of the three types of opening path (op1, linear or concave path; op2, path toward the chewing side after toward the non-working side; op3, convex path) and two types of closing path (cl1, convex path; cl2, concave path) was made. The movement path was classified into one of seven patterns, with six patterns being from the catalog and a final extra pattern in which the opening and closing paths crossed. The most common pattern among the subjects was Pattern I, followed by Patterns III, II, IV, V, VII, and VI, in that order. The majority of cases, 149 (74.5%) of 200 cases, showed either Pattern I (op1 and cl1) or Pattern III (op2 and cl1). There was no significant difference between the two genders in the frequency of each pattern. CONCLUSION: The movement path could be classified into seven patterns and no gender-related difference was found in the frequency of each pattern.

Usefulness of indicators for stability of masticatory movement path.

PURPOSE: To clarify the usefulness of the standard deviation (SD) and SD divided by the opening distance (SD/OD) of the opening lateral, closing lateral, and vertical components of the masticatory path as indicators of the stability of masticatory movement path. METHODS: Fifty subjects masticated softened chewing gum on the unilateral side for 20s, and the movement of the mandibular incisal point was recorded. For 10 cycles from the 5th cycle of 100 cases (50 subjects chewing on either side), a picture comprising each cycle path was displayed and classified subjectively into three categories (stable, unstable, and unknown) by three evaluators. The 18, 17, and 19 cases that were assessed as stable, unknown, and unstable were classified as Groups A, B, and C, respectively. For 10 cycles from the 5th cycle, the SD and SD/OD of the opening lateral, closing lateral, and vertical components representing the movement path as indicators for the stability of the path were calculated and compared among the three groups. RESULTS: The SD and SD/OD of the opening lateral, closing lateral, and vertical components were small in Group A, increased in Group B, and increased further in Group C. Significant differences were observed among the groups. These differences were more apparent in the assessment using the SD/OD than in the assessment using the SD. CONCLUSION: The SD and SD/OD of the components representing the movement path were useful as indicators for the stability of the movement path and the SD/OD appeared to be particularly useful.