Timing of developmental stages in permanent mandibular teeth of Finns from birth to age 25.

OBJECTIVE: The aim was to provide radiographic data on postnatal development of the 8 mandibular teeth to serve as reference norms in clinical dentistry, forensic dentistry, anthropology, and research. MATERIAL AND METHODS: Developmental stages of teeth were assessed from a total of 2795 radiographs, mostly panoramic, of 1970 Finns (966 M and 1004 F) from birth to age 25. The grading was based on Demirjian's 8 mineralization stages and the crypt stage. RESULTS: Timing of development in individual mandibular teeth is presented in two ways: as age at attainment of each developmental stage and as age of subjects in a developmental stage. Initiation of mineralization was visible in 1st molars at 0.20 years, in central incisors at 0.22 years, lateral incisors at 0.37 years, and canines at 0.56 years of age. Timing was usually earlier in girls than in boys. Differences were greatest in canines, where females were advanced by 1.74 years at the closure of the apex. Root development in 3rd molars showed an opposite trend, where apical closure was 1.19 years earlier in men. In 3rd molars, age at apical closure in females was 21.50 years, among the highest reported. In general, the early developmental stages had the shortest duration and the last stages the longest. CONCLUSION: Timing of postnatal development of individual mandibular teeth in Finns resembled developmental schedules reported for other Caucasian population groups. Any differences were mostly small and inconsequential.

Orthodontic treatment need from eight to 12 years of age in an early treatment oriented public health care system: a prospective study.

The aim of this study was to investigate the effects of an early treatment oriented orthodontic program on treatment need at age 12 years in a public health care system. The subjects consisted of one whole age cohort in a municipality in Finland, 87 children in total. All children were examined at ages eight, 10, and 12 years. Treatment need was assessed on casts using a modified Dental Health Component of the Index of Orthodontic Treatment Need and a 10-Grade Scale based on the Treatment Priority Index. Early treatment was started on children having definite treatment need according to both indices. The agreement between indices was good at ages eight and 12 years and moderate at age 10 years. Treatment need changed significantly from eight to 12 years. Of the 29 children with definite treatment need at age eight years, only two had treatment need at age 12 years. Of the 38 children with no treatment need at age eight years, 28 remained in this category and only two children had definite need for treatment at age 12 years. The duration of treatment ranged from one to 61 months, although 59% of the treatments lasted two years or less. We conclude that systematically planned early orthodontic treatment may have contributed to the significant reduction in treatment need from eight to 12 years of age.