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The effect of citric acid on the healing of periodontal ligament-free, healthy roots, horizontally implanted against bone and gingival connective tissue.

Edentulous sites were created in four adult baboons by prior extraction of all premolars. Amputated healthy molar roots were implanted horizontally into shallow grooves cut into the alveolar bone at these sites so that one side of the root faced gingival connective tissue and the other bone. Prior to implantation the roots were planed to remove all periodontal investing tissue and were demarcated by a circumferential groove into two portions. One portion was treated with citric acid (pH 1) for 3 minutes, thus creating side-by-side experimental and control sites facing both bone and soft tissue. The experimental sites were randomly distributed between apical and coronal root ends and observation periods of 4, 8, and 12 weeks were obtained. Efforts were made to reduce infection at the implantation site by the use of topical and parenteral antibiotics. After sacrifice the tissues were processed for routine light microscopy. Histometric analysis revealed that citric acid, in this situation remote from the influence of periodontal ligament and junctional epithelium, did not enhance new fibrous attachment and new cementum formation nor did it reduce artifactual tissue separation, root resorption, or ankylosis. Ankylosis and root resorption were the predominent features of the healing root surfaces facing bone and gingival tissue, respectively. However, the amount of root resorption on the gingival side was apparently less pronounced than that reported for similar studies probably because of the use of antibiotics to control infection.