The aim of this study was to investigate the clinical periodontal condition in subjects undergoing orthodontic treatment with fixed appliance and evaluate the effects of extracted the first premolars on the periodontal conditions of the second premolars and canines. Thirty-six healthy Class I orthodontic subjects, with modified edge-wise appliances were included in the study. In the eighteen subjects (extracted group) all first premolars were extracted. The other eighteen subjects were no extracted group. The teeth of all the subjects were scaled and polished. Also, their oral hygiene were motivated at each recall. On each subjecl the values of plaque index (Pl), sulcus bleeding index (SBI), gingival index (Gl) and periodontal pocket depths (PD) were assessed at the baseline, the first week, the first month, the third month and the sixth month during orthodontic treaünent. In all subjects, there were significant differences between the mean values of PI, Gl, PD at the baseline and the sixth month, while SBI was not found to be different between the baseline and the sixth month. PD (baseline), PI (the first week) and SBI (the first, week) mean values of the canines between extracted and no extracted groups were statistically different. PD (baseline) and PI (the first week) mean values of second premolars between extracted and no extracted groups were statistically different. The findings of this study suggested that in the subjects undergoing orthodontic treatment with fixed appliance, extraction of the first premolars has the effect on the clinical periodontal condition of the neighbour teeth in only the first week and in all subjects the periodontal health was affected by the orthodontic treatment.

Keywords: Fixed appliance orthodontic treatment, periodontal status