The Effect of Root Surface Demineralization on Bone Morphogenetic Protein‐2‐Induced Healing of Rat Periodontal Fenestration Defects

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Abstract
The purpose of this study was to investigate the effect of acid conditioning of root surfaces during recombinant human bone morphogenetic protein-2 (rhBMP-2) induced periodontal regeneration in vivo. The buccal aspect of molar roots were denuded of their periodontal ligament through a bony window created in the mandible of 34 Wistar rats under general anesthesia. Three groups of 11 or 12 animals received either 10 microL of 50 g/mL rhBMP-2 in a collagen gel over the surgical defect (BMP) or 10 microL of collagen gel only (COL) or were left untreated (UN). Each of the 3 groups were further subdivided into those that received prior root acid conditioning with 35% phosphoric acid gel and those without acid conditioning. Animals were sacrificed 10 days after surgery and the tissues processed for histological examination. The BMP groups with and without acid conditioning developed significantly more bone over the second molar (3.89+/-0.86% and 7.62+/-0.93%, respectively; mean+/-SE), compared with the respective COL (1.24+/-0.26% and 2.77+/-0.52%) and UN groups (1.34+/-0.35% and 3.69+/-0.37%) (P <0.05). Furthermore, significantly more bone was found in the BMP non-acid conditioned group compared with all other groups (P <0.05). Acid conditioning promoted significantly more ankylosis (50%) compared with non-acid conditioning (6.3%) (P=0.007). New cementum formation was greatest in the BMP acid conditioned group (628.4+/-253.8 microm2) and lowest in the non-acid conditioned UN group (207.6+/-36.4 microm2) (P <0.05). This is the first known report evaluating the effects of root acid conditioning after a single application of rhBMP-2 in vivo. Results suggest that root conditioning agents operating at low pH administered into the periodontal wound impairs early BMP-induced osteogenesis while simultaneously promoting BMP-induced cementogenesis.