Modulation of the masticatory path at the mandibular first molar throughout the masticatory sequence of a hard gummy jelly in normal occlusion.

OBJECTIVE: In this study, the authors investigated the modulation of the masticatory path at the mandibular first molar during natural chewing of a hard gummy jelly in adults with normal occlusion. METHODS: The unilateral mastication sequence was divided into three stages, and the masticatory path of the mandibular first molar on the working side was analyzed at 2.0, 3.0, 4.0, and 5.0 mm vertical slice levels below the intercuspation in the frontal and sagittal views. RESULTS: In the frontal view, the closing and opening angles and cycle width of the final stage at 3.0, 4.0, and 5.0 mm slice levels were smaller and narrower than those of the initial stage, although those at the 2.0 mm slice level were little changed. DISCUSSION: Masticatory paths of the mandibular first molar at slice levels greater than 3.0 mm were evidently modulated to adapt to the changing properties of the food, and those at the 2.0 mm slice level remained stable throughout the masticatory sequence.

Association of problem behavior with sleep problems and gastroesophageal reflux symptoms.

BACKGROUND: There are few large-scale epidemiologic studies examining the associations between sleep problems, gastroesophageal reflux disease (GERD) symptoms, lifestyle and food habits and problem behaviors (PB) in adolescents. The aim of this study was to evaluate the associations among these factors in Japanese adolescents. METHODS: A cross-sectional survey of 1840 junior high school students was carried out using questionnaires. The subjects were classified into PB or normal behavior (NB) groups using the Pediatric Symptom Checklist (PSC). The scores of the sleep-related factors, sleep bruxism, lifestyle and food habits, and GERD symptoms were compared. Logistic regression analysis was used to determine the factors related to PB. RESULTS: Mean subject age was 13.3 ± 1.8 years. The PB group had significantly longer sleep latency and higher GERD symptom score (P < 0.001). Furthermore, the PB group was significantly more likely to experience absence of the mother at dinner time, skip breakfast, and have <30 min of conversation among family at dinner time. The PB group had significantly higher frequencies of sleep bruxism, difficulty falling asleep within 30 min, nightmares, feeling of low sleep quality, daytime somnolence, and daytime lack of motivation. Feelings of low sleep quality had the strongest association with PB, with an adjusted odds ratio of 12.88 (95% confidence interval: 8.99-18.46). CONCLUSIONS: PB in adolescents are associated with sleep problems, including sleep bruxism, as well as lifestyle and food habits and GERD symptoms.

Changes in grafted autogenous bone during edgewise treatment in patients with unilateral cleft lip/palate or alveolus.

Objective : To examine the changes in autogenous bone from 6 to 12 months after alveolar bone grafting (ABG) (T1) through completion of edgewise treatment (T2). Design : Retrospective longitudinal study. Setting : Multidisciplinary long-term follow-up at Kagoshima University Hospital. Patients : Forty-three patients with unilateral cleft lip and palate or alveolus. Main Outcome Measures : At T1 and T2, the bone bridge and quantity of grafted bone were evaluated using the Chelsea scale and the ABG scale. The cleft-adjacent tooth angles before ABG and at T2, as well as the number of orthodontic space closures, were examined. Patients were classified as having either adequate (type A or C; adequate group) or poor bone bridges (type B, D, E, or F; poor group) by the assessment at T1. Results : At T1, the ABG scores for the cleft-adjacent central incisor side of patients in the adequate group were higher than those of patients in the poor group (P < .001). At T2, the adequate group had higher ABG scores for the cleft-adjacent central incisor side (P = .022) and the canine sides (P = .034). No significant differences in tooth angles or the number of orthodontic space closures were noted between the groups. Conclusions : These results suggest that the quantity of grafted bone in the cleft-adjacent central incisor at 6 to 12 months post-ABG may be an indicator of the quantity of grafted bone that will be present after edgewise treatment.

Relationships between the root-crown ratio and the loss of occlusal contact and high mandibular plane angle in patients with open bite.

OBJECTIVE: To determine the root-crown (R/C) ratio and dental root length of teeth in patients with open bite and seek any relationships with occlusal contact (OC) and the mandibular plane (Mp) angle. MATERIALS AND METHODS: Thirty-one patients with open bite with negative overbite of at least four anterior teeth and 31 control patients with clinically normal overjet and overbite were enrolled. R/C ratios, dental root length, OC, and Mp angle were measured using panoramic radiographs, dental casts, and cephalograms, respectively. Mean differences between the groups, and variations between the R/C ratio or root length and Mp angle in patients with open bite were statistically analyzed. RESULTS: R/C and OC ratios from the incisors to premolars were significantly lower for patients with open bite than for controls, and some teeth had short dental roots. Relationships between low R/C ratio or root length and high Mp angle were significant in patients with open bite. CONCLUSION: Patients with open bite, especially those with a high Mp angle, have an unfavorable R/C ratio and short dental roots in some teeth, which may be related to the loss of OC.