[Histomorphologic evaluation of upper lip frenum in relation to the method of treating diastema]

The aim of this study was to determine collagen density in the hypertrophic upper lip frenum and scar forming after frenectomy and to compare the results with collagen density in a normal population (autopsy specimens). Differences in collagen density may cause problems in diastema closure and may eventually result in relapse of this condition. The study was done in 47 patients treated for diastema. Histomorphology was performed in 15 patients of this group. Autopsy material was obtained from 27 persons. Histomorphometric assessment of collagen density was done after staining of collagen fibers according to van Gieson. A computerized image analysis system was used for interactive detection of stained collagen fibers on the digitized microscopic image. The percentage of positive staining expressed as ratio of positive area to whole area of the field studied was determined and recorded as an Excel file. Collagen density was increased in the pathologic frenum and in the scar as compared with the normal frenum. The difference was statistically significant. Diastema treatment with frenectomy, fixed appliance and retainer produced more stable results as compared to treatment with a removable appliance without frenectomy. The results suggest that the similar collagen density observed in hypertrophic upper lip frenum and scar after frenetomy may hinder complete closure of diastema and facilitate relapse after treatment.