Perturbation of Rat Alveolar Bone Remodeling under Bisphosphonate(HEBP) Regimen: Osteoid-mediated ankylosis and its convalescence accompanying the periodontium reconstruction

The present study was undertaken to investigate the effects of systemic HEBP (1-hydroxyethylidene-1, 1-bisphosphonate) administration on the alveolar bone structure at the intraradicular region of rat lower molars. Male Wistar rats (about 100 g b.w.) were divided into three groups: (a) animals kept with drinking water containing 1% HEBP throughout the housing periods covering 4 days through 8 weeks; (b) animals given the same HEBP-containing water during the initial 4 weeks, thereafter being kept with HEBP-free drinking water for various periods (4-28 days) ; and (c) animals kept free from HEBP during the corresponding periods as the control group. The tooth specimens were examined by histometric analysis in conjunction with H.E., van Gieson, and TRAP stainings; or by microradiography. The results obtained evidenced that: 1) systemic administration of 1% HEBP stimulated the outgrowth of osteoid due to hindrance of mineralization onto the deposited bone matrix and osteoclastic resorption activity, giving rise to obliteration of the periodontal space (development of focal ankylosis) ; and 2) after cessation of the HEBP administration, TRAP-positive osteoclasts penetrated into the ankylosed areas, leading to reconstruction of the periodontal structure within the following 3 to 4 weeks. It is pertinent that the use of HEBP to rat provides an experimental model for pathogenesis of the osteoid-mediated ankylosis and its reversible recovery.