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T his study was performed to evaluate the effects of orthodontic therapy on the width of the zone of keratinized gingiva. Pre‐ and post‐treatment photographic slides, plaster study casts, and cephalograms were examined. The labial surfaces of 966 teeth in a sample of 100 orthodontic patients were studied. Widths of the keratinized gingiva were determined from photographic slides. Crown lengths were measured from the study casts, and measurements were performed on the cephalograms. Data were collected and analyzed in three categories: 1) The overall changes in the width of the keratinized gingiva and the lengths of the clinical crowns during the course of orthodontic therapy; 2) An analysis of grouped data with a comparison of the pre‐existing widths of keratinized gingiva to the post‐treatment periodontal status of the patient; and 3) A correlation analysis of the changes in the dimensions of the tissues to the changes in tooth position as measured on the cephalograms. The results of the study revealed: 1) Increases in the width of the keratinized gingiva may occur on some teeth during the course of orthodontic therapy; 2) Statistically significant increases in the clinical crown during orthodontic therapy are not reflected in statistically significant decreases in the width of keratinized gingiva; 3) Minimal widths of keratinized gingiva (less than 2 mm) are capable of withstanding the stresses of orthodontic mechanics; 4) Teeth that are lacking in any keratinized gingiva prior to orthodontic treatment will not form any new keratinized tissue during the course of orthodontic therapy; 5) Mucogingival problems noted after orthodontic therapy are often the result of a pre‐existing mucogingival problem; 6) Changes in the dimensions of the keratinized gingiva correlated statistically with the orthodontic movement of the maxillary central incisors ( P < 0.001) and, with the maxillary and mandibular cuspids ( P < 0.02).
Coatoam et al. (Mon,) studied this question.