The main purpose of the study was to highlight the causes that may lead to reduction of arches: early loss of deciduous teeth, with consecutive dental drifting on the arch, followed by narrowing of the space necessary for the eruption of successional teeth, caries of the deciduous teeth or ectopic eruption of the first permanent molars. The mesial position of M1 had a frequency of 19.31% of the total number of analysed cases; maximum frequencies have been registered for the localization on the lower arch; M1 ectopia has rarely occurred on the studied batch; the frequency of lateral group mesial position was of 10.34% on the studied batch, registering maximum values for the localisation on the upper arch. The early loss of deciduous teeth was identified in almost 30% of the analysed cases, while the reduction of the space necessary for the eruption of successional teeth was registered in almost 39% of cases, space narrowing resulting both from the caries of deciduous teeth and from their early loss.
Keywords:- deciduous teeth.
- mesial position
- molar ectopia