Prevalence of dental caries and associated factors among 10-12-year-old students in Chongqing / 华西口腔医学杂志

OBJECTIVE@#To investigate the caries status of the first permanent molars in urban and rural children aged 10-
12 in Chongqing and analyze the related factors in order to provide a theoretical basis for the prevention and treatment of children's caries and targeted suggestions for oral health education.@*METHODS@#A multi-stage, stratified, cluster, and random sampling method was used to extract 5 057 children from 18 schools in three districts and three counties in Chongqing for oral health examination and questionnaire survey from March to May 2018.@*RESULTS@#The total caries rate of the first permanent molar was 39.2%. The decayed-missing-filled tooth was 0.84±1.20. The rate of filling teeth was 3.4%. The rate of pit and fissure sealing was 6.1%. The prevalence of the first permanent molars was significantly different between men and women, between urban and rural areas, between only children and non-only children, and between ethnic minorities and Han nationality (P<0.001). The gap between the pit and fissure sealing was significantly different between urban and rural areas (P<
0.001). Multiple logistic regression analysis showed that many independent factors influence the occurrence of caries, including the frequency of brushing teeth every day, the frequency of eating desserts, the habit of eating dessert/drinking milk before going to bed, whether only-children or not, and parents' education background, among others.@*CONCLUSIONS@#The first permanent molars of children aged 10-12 in Chongqing have a high rate of caries but low rates of pit and fissure sealing and dental caries filling. The difference between urban and rural areas is large, children's oral health knowledge is scarce, and children have bad oral hygiene behaviors and eating habits. Children's oral health education must be strengthened, oral health preaching must be implemented in schools, the oral health knowledge of children in school must be improved, and urban-rural differences must be minimized.

Three-dimensional finite element analysis of stress distribution in mandible advanced with Forsus / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To construct a three-dimensional finite element model of mandible and to analyze the stress distribution in mandible advanced with Forsus.</p><p><b>METHODS</b>One growing patient with mandibular retrusion was selected. After leveling and aligning with MBT (Mclaughlin Bennett Treriri) straight-wire appliance to achieve the request of forsus with the spiral CT, a three-dimensional finite element model was constructed and the stress distribution in mandible after advancing at 1 second, 15 seconds and 300 seconds was analyzed.</p><p><b>RESULTS</b>The three-dimensional finite element model included MBT straight-wire appliance. The stress concentration areas were located in the front side of the condylar process, the sigmoid notch and mandibular molar areas at 15 seconds and 300 seconds after mandibular advancement. The maximum stress values were 34.47 MPa and 34.45 MPa, respectively. With the extension of loading time, the largest displacement increased from 3.30 x 10(-2) mm to 1.15 mm and the region of the largest displacement extended backwards along the body of mandible. However, the displacement of condyle reduced from 1.65 x 10(-2) mm at 1 second to 3.27 x 10(-5) mm at 300 seconds after mandibular advancement.</p><p><b>CONCLUSIONS</b>The three-dimensional finite element model considered the viscoelasticity and viscoelasticity of mandibular. The result suggested that the stress distribution in the mandible gradually became stable after the application of Forsus and the appliance caused downward and forward mandibular modification.</p>