Occlusal features of primary dentition in Chinese preschool children

Abstract

AIM: To study the occlusal features of primary dentition of preschool children in Hong Kong. METHODS: Seven kindergartens in Hong Kong were included in this study. Invitation letter was sent to parents of Chinese children attending grades 2 and 3 for an occlusal assessment. Consent was obtained from 92% of them. The children were examined by two trained examiners using CPI probes, dental mirror and intra-oral LED lights in the kindergartens. Children with one or more permanent teeth erupted were excluded. Occlusal features examined included molar and canine relationship, overjet and overbite, presence of median diastema, primate space, crossbite and mandibular displacement on closure. 10% of the children were re-examined to assess the inter-examiner reliability. RESULTS: A total of 557 children, 299 boys and 258 girls, were examined. Their mean age was 5.1 years. For molar relationship, there were 66% with flush terminal plane, 9% with mesial step and 25% with distal step. For canine relationship, there were 77% with class I, 6% with class II and 17% with class III. There were 12% children with increased overjet (≥4mm), 27% with edge to edge relationship and 8% with reverse overjet. Increased overbite was found in 38% of the children, while anterior openbite was found in 0.7%. Median diastema was observed in 34% of the children. Primate space (>0.5mm) was present in 78% and 43% of the upper and the lower arch, respectively. Prevalence of anterior crossbite and posterior crossbite were 12% and 1%, respectively. Among the children with anterior crossbite, 43% of them presented with mandibular displacement on closure. There is a statistically significant association between anterior crossbite and mandibular displacement (p<0.001). CONCLUSION: The most prevalent occlusal features of Chinese preschool children were normal overjet for incisors relationship, class I for canine relationship, and flush terminal plane for molar relationship.