Effects of ethnicity, gender and age on clenching force and load distribution.

The aim of the study was to investigate the effect of ethnicity, gender and age on the degree of clenching force and distribution of the load over the dentition. The maximal clenching force was measured in 12 young Danish females, 12 young Japanese females, 12 young Japanese males and 10 senior Japanese males using the Dental Prescale System. The occlusal contact area, average pressure, occlusal load, antero-posterior and right-left location of the occlusal load center (i.e., a center of balance of the occlusal load distributed over the maxillary dentition: OLC) and dental arch length and width were analyzed and compared. The arch width and average pressure in young Danish females were significantly smaller/lower than in Japanese females. The arch length, arch width, contact area and total occlusal load in young Japanese males were significantly greater than those of the Japanese females. The average pressure in young Japanese males was also greater than in senior males. The location of the OLC was almost the same in all groups. The results suggest that the analysis of the OLC may be a useful method for evaluating occlusal function and prosthodontic treatment because the location of the OLC is not affected by ethnicity, gender and age.

Bite force and occlusal load distribution in normal complete dentitions of young adults.

The aim of this study was to investigate the bite force and its distribution over the maxillary dentition in completely dentate subjects. Twenty-three dental students (14 Danish, 9 Japanese) with complete dentitions, but without occlusal contact on the third molars participated and their maximal bite forces were measured using the Dental Prescale System close to intercuspation. The antero-posterior location of the occlusal load centre, i.e. the centre of balance of distributed occlusal load, was a little posterior of the centre of the upper first molar. These results could be used as a basic model for evaluation of occlusion.

[Reproducibility of maximal bite force distribution over dentition].

We have reported that the analysis of the maximal bite force distribution over dentition was available for objective evaluation of prosthodontic treatment. The purpose of this study was to investigate the reproducibility of occlusal force distribution in maximal voluntary clenching. The maximal bite forces of 10 normal subjects with complete dentition were measured at close to intercuspation using Dental Prescale System. The measurements were performed two times with an interval of 3 years. The differences of the distributed occlusal force and the location of occlusal load center, i.e., the center of balance of distributed occlusal force, between 1st and 2nd measurement were evaluated by Mann-Whitney signed rank test (p < 0.01). The coefficient of variance was calculated from the results of two measurements in order to assess the measurement error. The statistical significant differences were not found in all measurement protocol and the coefficient of variance of the location of occlusal load center showed a remarkably small value (4.0%). The mean of absolute differences in the location of occlusal load center between two measurements were almost 4.0 mm anteroposteriorly and right-left. These results suggested that the maximal bite force measurement and the analysis of occlusal force distribution using Dental Prescale System were useful for the longitudinal evaluation of masticatory function and prosthodontic treatment. The analysis of occlusal load center was shown to be the most reliable method for evaluation. The reliable range for the reproducibility of occlusal load center was also shown.

[A clinical and physiological evaluation of masticatory center in shortened arch].

The aim of this study was to evaluate the influence of occlusal deficit by loss of bilateral posterior molars in masticatory habituation and how to improve by RPD, investigating the location center of occlusal load (by Prescale Fuji Film Co.) and in its amount, in connection with masticatory muscle activities by analyzing EMG. EMG measurements of masticatory masculature at maximal clenching with pressure indicator, were induced at intercuspal position, confirming by MKG. As controls, seven complete dentate adults were referred, the five mandibular and maxillary bilateral molar-edentate cases each of five were investigated. The results were as follows: i) The location of the center of the occlusal load in dentate mouth was about the midline of the maxillar first molar. ii) In the loss of bilateral molars, the center of the occlusal load was in the first premolar area. iii) By prosthodontic treatments the center of the occlusal load was changed to the second premolar area. iv) These results indicated that the prosthodontic treatment was estimated in physiological imperfection of recovery as yet dentate mouth.