The Effect of Progressive and Increasing Tooth Hypermobility on Reduced but Healthy Periodontal Supporting Tissues

Abstract

The aim of the present investigation was to assess the effect of progressive and increasing tooth hypermobility on a periodontium reduced by marginal periodontitis, but in which the inflammatory lesion had been resolved. Periodontitis was induced by tying plaque-retentive silk ligatures around the mandibular second and third bicuspids on one side of the jaw (experimental) in four squirrel monkeys. Ten weeks later the ligatures were removed and an oral hygiene regime of mechanical cleaning was started and continued 3 times a week for 20 weeks. Ten weeks after beginning oral hygiene, continual mesio-distal jiggling trauma to the periodontium between these bicuspids was begun and continued for the remaining 10 weeks. Induction of periodontitis, removal of ligatures, and the oral hygiene regime were performed around the same teeth of the contralateral side (control) of the jaw so that the interproximal periodontium corresponded to the situation on the experimental side immediately before initiation of jiggling. The bicuspids had slight mobility prior to the initiation of jiggling; however, mobility increased progressively throughout the period of tooth displacement. Histologic examination showed that each periodontal ligament under compression had areas of acellularity, while those under tension were widened with dilated blood vessels. In contrast to the dense alveolar bone of control specimens, the alveolar bone of the experimental specimens was characterized by islands of osseous tissue surrounded by the connective tissue of the marrow spaces and periodontal ligaments. Histometric analysis showed that the progressively increasing tooth mobility on the reduced periodontium had significantly decreased the percentage of bone in the coronal interproximal periodontium, but it had not affected the level of crestal alveolar bone or the level of connective tissue attachment. It was concluded that teeth with markedly reduced but healthy periodontal tissues may continually accommodate to increasing and multidirectional forces by morphologic alterations in the periodontium which are independent of alterations in the level of connective tissue attachment.