Statistical presentation of eruption age of permanent second molars, premolars and canines in female school children living in Riyadh, Saudi Arabia

OBJECTIVES: To determine the mean eruption times of permanent canines, premolars and second molars; and the relationship of the eruption times of these teeth with height, weight and Body Mass Index (BMI) in Saudi female school children in Riyadh. DESIGN: Cross-sectional study using stratified cluster random sampling. PLACE and DURATION: The data were collected within one and a half months (September to October 2005) from 10 schools of Riyadh, Saudi Arabia. SUBJECTS and METHODS: The study comprised female school children of grade 4 to grade 9 from primary andintermediate schools in Riyadh. Ten schools (8 public and 2 private) were randomly selected from four regions of Riyadh City. A total of 3186 children were examined of which 889 children were found suitable for the study. Clinical examination was carried out under natural light by direct visual inspection and manual palpation. Height and weight of the selected subjects were recorded. Demographic information on age, educational level, date of birth, place of birth and family name of the children were recorded from the school record. RESULTS: The mean age of 889 subjects was 11.58 ± 1.57 years(R: 8.8 – 16.1 years). Mandibular left canine showed the lowest mean eruption age of 10.5 ± 0.9 years. Maxillary left second molar showed the highest mean eruption time of 13.0 ± 1.3 years. Maxillary second molars and maxillary canines showed significantly late eruption than the corresponding mandibular teeth (P 0.0001). All comparisons of contralateral teeth were insignificant (P 0.05), except the maxillary second molars and second premolars (P = 0.025 and P = 0.012, respectively). Eruption time was significantly positively correlated, linear as well as partial, with height of the children for all the studied teeth. However, the partial correlation with weight was negatively correlated for all the studied teeth except maxillary right second premolar. There was no statistically significant correlation between eruption time and BMI (P 0.05). CONCLUSIONS: Mandibular left canine showed the lowest mean eruption time, while maxillary left second molar showed the highest mean eruption time. The mandibular teeth erupted before their maxillary counterparts, except right second premolar and left first premolar. Eruption of teeth was positively related to somatic growth (height and weight), while it became negatively correlated with weight, when height was controlled.