Space changes after premature loss of the mandibular primary first molar: a longitudinal study.

The purpose of this study was to evaluate the space changes after premature loss of the primary mandibular first molar. Twenty-one children (12 boys and 9 girls), with premature loss of the primary mandibular first molar, were selected from the children's dental clinic for this study. The age ranged from 5.1 to 7.2 years with an average of 6 years and 11 months. Mandibular study casts were made from alginate impression for each initial examination and a follow-up examination eight months later. Four measurements including D+E (first and second primary molars) space, arch width, arch length and arch perimeter were tested for comparisons between the initial examination and the follow-up examination eight months later. The D+E space of intact primary molars served as a control. The results showed that the D+E space on the extraction side after the follow-up examination eight months later was significantly shorter than the control side (p = 0.025) and less than the initial D+E space (p < 0.001). However, there were no significant differences on arch width, arch length, and arch perimeter between the initial examination and the follow-up examination eight months later (p > 0.05). It is concluded that the space change after the eruption of the first permanent molar in the mandible is mostly distal movement of the primary cuspid during the early stage of premature loss of the primary first molar.