Objective:  To examine the expression of possible secular trend in timing of the emergence of permanent teeth in Finnish children over the past few decades, considering the differences between genders. Materials and Methods:  Two age groups of Finnish children, one born in 1976–1985 (group 1980) and the other born in 1999–2002 (group 2000), were examined. Group 2000 comprised 483 children (235 girls and 248 boys) aged 6.4 to 8.5 years at the time of the examination, and the same children were examined at the age of 9.0 to 11.8 years. Altogether 405 children could be recalled, 196 girls and 209 boys. For comparison, matching age groups were selected from the group 1980 data (n = 1579), resulting in a sample of 312 children (155 girls and 157 boys) aged 6.4 to 8.5 years and 393 children aged 9.0 to 11.8 years. The emergence stage of each permanent tooth was determined clinically (Grades 0–3), based on which the subjects were furthermore divided according to the emergence stage of the dentition. Results:  Linear regression models showed that the permanent teeth of the first phase of the mixed dentition erupted earlier in group 2000 than in group1980, but the teeth of the second phase of the mixed dentition erupted later in group 2000. Girls showed more advanced tooth eruption than boys. Conclusion:  The longer duration of mixed dentition in group 2000 than in group 1980 makes the duration of combined follow-up and active treatment longer, and should be considered in timing of efficient orthodontic treatment.

When planning resources for orthodontic treatment for different populations as well as planning treatment for individuals, ethnic background and emergence stage of the dentition need to be considered.

Occlusal characteristics and anomalies were studied among 869 (428 boys, 441 girls) Tanzanian Bantu children aged 3.5-16 years and 706 (319 boys, 387 girls) Finnish children aged 5-11 years during different emergence stages of the permanent dentition. Various occlusal variables were registered according to described criteria. Multiple linear regression, ANOVA, t-test, Chi-square and logistic regression models were used to test for various statistically significant differences between different subgroups. Significant differences between Tanzanians and Finns were found for malocclusion, neutral and distal molar occlusion, mean values for overjet and overbite, overjet greater than 5 mm, deep bite and anterior open bite (all P < 0.0001). The most prevalent anomalies among Tanzanians were anterior open bite (7-19 per cent), increased overjet (3-19 per cent) and distal molar occlusion (3-16 per cent). For the Finns, distal molar occlusion (18-38 per cent) was the most prevalent anomaly, followed by deep bite (4-22 per cent) and increased overjet (4-40 per cent). An anterior crossbite was rare and equally distributed among the two ethnic groups. Girls had a larger mean value for overbite (P = 0.003) and more often a deep bite (P < 0.01) than boys. Mandibular incisor crowding among children with neutral occlusion (Class I malocclusion) occurred significantly more often among Finnish than Tanzanian children. In conclusion, various developmental changes in occlusion were observed leading to variation in occlusal characteristics and anomalies according to the emergence stages of the permanent dentition. Most of the classic malocclusions occur among Tanzanian children, but the prevalence differs from that in other parts of the world.