Change in occlusion and masticatory function after orthodontic treatment was investigated by a follow-up study in a group of 14 patients with malocclusion (3 men, 11 women, aged 12-46 years). All completed a food questionnaire and underwent occlusal force evaluation using a pressure-sensitive sheet at pre-treatment, post-treatment, and during the retention phase. The number of foods identified as difficult to eat decreased at post-treatment in all patients. The mean occlusal force was 646.65223.5 N at pretreatment, 401.15109.1 N at post-treatment, and 530.65183.6 N during the retention phase. The mean occlusal contact area was 14.155.9 mm 2 at pre-treatment, 6.551.7 mm 2 at post-treatment, and 9.853.8 mm 2 during the retention phase. The mean average occlusal pressure was 47.656.6 MPa at pre-treatment, 62.255.7 MPa at post-treatment, and 55.456.7 MPa during the retention phase. A Dental Prescale film evaluation revealed that occlusal force and occlusal contact area increased over the 1-year retention phase. An improvement in level of satisfaction with mastication ability was reported at posttreatment and during the retention phase. Average occlusal pressure at post-treatment increased significantly (p<0.01), which may account for the observed increase in the ability of the patients to bite through food. These results suggest that an increase in average occlusal pressure improves level of satisfaction with mastication ability.

The aim of this study was to obtain basic data that might serve as criteria in the diagnosis of delayed eruption of the permanent teeth. The synchronicity of the eruption of corresponding contralateral teeth was determined. Data were obtained on both the deciduous and permanent dentition based on records made every 2 months at the Department of Pediatric Dentistry of Tokyo Dental College. These data were then used to investigate bilateral differences in the timing of eruption of the permanent teeth. Over 80% of incisors, first molars, mandibular canines, and maxillary first premolars erupted within 4 months of their contralateral counterparts, while this occurred in 75% of maxillary canines, mandibular first premolars, and mandibular second molars, 70% of maxillary and mandibular second premolars, and 65% of maxillary second molars. Bilateral differences in the timing of permanent tooth eruption varied depending on type of tooth, and these differences tended to be smaller for teeth erupting at an earlier point in the order of eruption, and greater for those erupting at a later point. These results suggest that the failure of a contralateral tooth to erupt within 4 months of its counterpart might serve as a criterion in a diagnosis of suspected delayed eruption of a permanent tooth.

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