THE EFFECT OF ROOT SURFACE DEMINERALIZATION ON BONE MORPHOGENETIC PROTEIN-2-INDUCED HEALING OF RAT PERIODONTAL FENESTRATION DEFECTS

THE PURPOSE OF THIS STUDY WAS to investigate the effect of acid condit ioning of root surfaces during recombinant human bone morphogenetic pr otein-2 (rhBMP-2) induced periodontal regeneration in vivo. The buccal aspect of molar roots were denuded of their periodontal ligament thro ugh a bony window created in the mandible of 34 Wistar rats under gene ral anesthesia. Three groups of 11 or 12 animals received either 10 mu L of 50 g/mL rhBMP-2 in a collagen gel over the surgical defect (BMP) or 10 mu L of collagen gel only (COL) or were left untreated (UN). Ea ch of the 3 groups were further subdivided into those that received pr ior root acid conditioning with 35% phosphoric acid gel and those with out acid conditioning. Animals were sacrificed 10 days after surgery a nd the tissues processed for histological examination. The BMP groups with and without acid conditioning developed significantly more bone o ver the second molar (3.89+/-0.86% and 7.62+/-0.93%, respectively; mea n+/-SE), compared with the respective COL (1.24+/-0.26% and 2.77+/-0.5 2%) and UN groups (1.34+/-0.35% and 3.69+/-0.37%) (P < 0.05). Furtherm ore, significantly more bone was found in the BMP non-acid conditioned group compared with all other groups (P < 0.05). Acid conditioning pr omoted significantly more ankylosis (50%) compared with non-acid condi tioning (6.3%) (P = 0.007). New cementum formation was greatest in the BMP acid conditioned group (628.4+/-253.8 mu m(2)) and lowest in the non-acid conditioned UN group (207.6+/-36.4 mu m(2)) (P < 0.05). This is the first known report evaluating the effects of root acid conditio ning after a single application of rhBMP-2 in vivo. Results suggest th at root conditioning agents operating at low pH administered into the periodontal wound impairs early BMP-induced osteogenesis while simulta neously promoting BMP-induced cementogenesis.