The optimal result of periodontal therapy is the regeneration of tissues previously destroyed by periodontal disease. In order for regeneration to occur, it is believed necessary to eliminate all root surface alterations. Preparation of the root surface include scaling and root planning, use of acids and other chemical and biological agents. Citric acid has been studied by several authors, but still remains in controversy the biological nature of its effects. In spite of this, the findings of some studies indicate that citric acid used on root surfaces results in: elimination of endotoxins; chemical, exposure of dentin collagen fibers; induction of cementogenesis by the exposed dentin; demineralization of root cementum; enhancement of fibroblast attachment when a plasma factor is used in addition to citric acid demineralization and influence on direction in which the epithelium initially starts to migrate. By the other hand root surface preparation by mean of scaling and root planning is an unpredictable procedure due to variables such as failure to remove the cementum on calculus debris in a clinical situation. New research is needed in order to obtain a predictable root conditioning procedure for a biological surface.