Gingival tissue reactions to orthodontic closure of extraction sites. Histologic and histochemical studies.

The formation of a hyperplastic gingival tissue with invagination was observed in the extraction areas in seven patients aged 12 to 17 years who, after extraction of the maxillary first premolars, were undergoing orthodontic treatment with an edgewise appliance. This tissue was excised when about 2 mm. of the space remained to be closed. Histologic and histochemical analyses of the biopsy areas demonstrated hyperplasia and increased metabolism in the invaginated epithelium as well as increased production of glucose aminoglycans in the surrounding connective tissue. Loss of collagen was noted in the same regions. There was evidence of bone remodeling rather than only bone resorption in the biopsy area. It was concluded that stimulation from the orthodontic forces was responsible for the hyperplastic tissue reaction and that the increased amounts of glucose aminoglycans may be responsible for possible relapses.