[Sequence in calcification and eruption of second premolars and molars--a longitudinal study]

Investigation was done with the purpose of establishing frequency of eruption and calcification of P2 and M2 and to perform a longitudinal analysis of certain types, observing the changes during growth, character of these changes and their durability. Analysis was done on 354 orthopantomographic radiographs of orthodontic patients from Nis, aged 7 to 12 years. Eruption phase was determined on the bases of vertical relation to M1 Development phase was determined with the help of a table with 11 developmental phases. Depending on tooth in predominance, patients were divided into three groups: P2M2, (P2M2) and M2P2. All three types of eruption and calcification were recorded. (P2M2) eruption is dominant in maxilla, while M2 has some advantage in mandible. In calcification of both jaws, type P2M2 is predominant in both sexes. In later age, eruption shows changes of type-in 31% to 39% of cases, but this percentage is lower in calcification-from 22% to 25%. Relation of P2 and M2 in eruption is not permanent and changes with growth: in maxilla, P2 has synchronous position in relation to M2 until 8 years of age, to gain advantage in later years; in mandible, P2 has lower position until 10 years of age, to start quicker growth in eleventh year so that in 42% of cases it erupts before M2. In development phase, P2 has advantage in both jaws. P2M2 type shows least changes with age. Other two types change into type P2M2 in 40% of cases. Once set sequence of eruption and calcification cannot be a reliable indicator of later growth since considerable changes were observed in most patients.