Lack of significance of increased tooth mobility in experimental periodontitis.

This experiment was carried out in order to study the rate of progression of experimentally produced periodontal tissue breakdown in teeth which prior to the placement of cotton floss ligatures either had a normal or a permanently increased tooth mobility. Six beagle dogs were used. Trauma from occlusion of the jiggling type was produced on test teeth using a model previously described. Four months later experimental periodontal tissue breakdown was induced around both control and test teeth by placing cotton floss ligatures around the necks of the teeth. The ligatures which were exchanged once every 4 weeks during a 4-month period were replaced at the level of the gingival margin. Tooth mobility measurements and radiographic examinations were performed on Days 0, 30, 60, 90, 120, 160, 240 and 300. One dog was killed on Day 120 and the remaining 5 dogs on Day 300. Biopsies of the test and control teeth were fixed in formalin, decalcified, embedded in paraffin and mesiodistal sections cut with the microtome set at 4 micron. The results demonstrated that the degree of periodontal breakdown, initiated and maintained by ligature placement and plaque accumulation, was similar around teeth with a wide periodontal ligament space and in teeth with a normal width of the periodontium. In other words, progression of the plaque-associated lesions appeared to be unrelated to the width of the periodontal ligament space, i.e., to the degree of horizontal tooth mobility.