Loss of Masticatory Function Affects Morphology of the Tooth Root in Rats

Masticatory hypofunction and soft food affect the tooth rows, occlusion, and jawbone. This study aimed to clarify the influence of tooth loss and a soft diet on morphology of the tooth root during the growth period. We divided 3-week-old Wistar rats into the following three groups: Hard diet group (rats raised on solid standard diet), Powder diet group (rats raised on powdered standard feed diet), and Extraction group (rats raised on powdered standard diet with maxillary molars extraction). Length, width, cross-sectional area, and volume of the root of the mandibular M1 and M2 were measured using micro-CT analysis. Non-decalcified thin-slice specimens of sagittal sections of the M1 were obtained at the age of 20 weeks, and the roots were observed. The root length of all roots in the Extraction group was significantly longer than that in the other groups. The root width and cross-sectional area at the apical side 1/4 of all roots in the Extraction group were significantly smaller than those in the other groups. The root volume of the M1 mesial root in the Extraction group was significantly smaller than that in the other groups. This study clarified that when masticatory stimulus in the immature teeth is reduced by the extraction of opposing teeth and a powder diet, the root length increases due to the promotion of cellular cementum addition at the apex, and the root width and cross-sectional area decrease due to the suppression of cellular cementum addition at the apical side 1/4 of the roots.

Dental caries and first permanent molar pit and fissure morphology in 7-to 8-year-old children in Wuhan,China

To obtain the caries experience and, plaque accumulation severity and pit and fissure morphology in first permanent molars in 7-8 children in Wuhan, as a reasonable prediction of caries risk and preventive attention in the future, a convenient sample of five primary schools in the vicinity of the Wuhan University School and Hospital of Stomatology was drawn. Two calibrated examiners orally examined all present grade 2 children in the classroom, using standard caries plaque and tooth morphology criteria. Dental caries was scored at enamel （D2） and dentine （D3） for tooth and surface level. Independent variables were age, gender and school. Data analysis used analysis of variance and t-test. The sample comprised 1 043 7- and 8-year-olds. The prevalence of dental caries in permanent dentition was 8.7% and in primary dentition, 68.7%. Mean Decayed, Missing, Filled Teeth/S （DMFT/S） scores were 0.1 1 and . 14, respectively. Mean dmft/s scores were 2.8 and 5.0. The d-component constituted 75% of the d3mft index, while enamel carious lesions constituted 36% of the total number of carious lesions （d2,3-component）. Prevalence of medium and deep pits and fissures was 84.6%. Prevalence of medium and severe plaque accumulation was 67.4%. Prevalence of dental caries in the deciduous and permanent dentitions of 7- to 8-year-old children was high. Deed oits and fissures in high caries risk children should be sealed_