Volume 72 • Number 12 Preprosthetic Periodontal Surgery in the Interproximal Area With Modification of the COL Area: Anatomic and Histologic Study in Dogs Arthur B. Novaes Jr.,* Arthur B. Novaes,* and Paulo T. de Oliveira † 1734 Background: Due to its concave morphology, a COL creates difficulties for proper oral hygiene. When this characteristic is accentuated by tooth position or caries and when restorations are necessary, they should be corrected by preprosthetic surgery. However, there are no data proving the efficacy of the proce- dures. The purpose of this study was to evaluate tissue response to preprosthetic surgery to modify COL morphology. Methods: Five mongrel dogs received apically positioned flaps, osteotomy/plasty, and RAI (restorative alveolar interface technique) on the maxillary right third bicuspid and first molar; on the same teeth on the left side, a large tissue excision simi- lar to gingivectomy and RAI were performed. Histologic speci- mens stained with hematoxylin and eosin and Mallory were eval- uated at hour 0 and 1, 2, 3, and 4 weeks under light microscopy. Results: At hour 0, hemorrhage in the remaining interprox- imal tissue on the left side, and denuded bone modified by the osteotomy on the right side, were observed. At 1 week, both sides showed the presence of granulation tissue and the begin- ning of reepithelialization and fiber formation. At 2 weeks, the papillae were rebuilt and epithelialized, with fewer inflammatory cells and dilated blood vessels, with a convex morphology. At 3 weeks, the papillae were convex and saddle shaped, with thicker epithelium and denser connective tissue. The general aspect was similar to attached gingiva. However, on the right side, the total extension of the interproximal tissues was longer and had a less accentuated convex curvature. At 4 weeks, the tissues were more mature, but the morphologic and histologi- cal findings were similar to 3 weeks. Conclusion: Both techniques modified the COL morphology, suggesting that the RAI technique was effective; but the api- cally positioned flap with osteotomy and RAI created a more extensive convex surface and more interproximal space for the prosthesis. It is recommended that this technique be considered for use in humans. J Periodontol 2001;72:1734-1741. KEY WORDS Alveolar bone/surgery; animal studies; preprosthetic surgery; surgical flaps; osteotomy; comparison studies. * Department of Oral Surgery and Periodontology of the School of Dentistry of Ribeirão Preto, University of São Paulo, SP, Brazil. † Department of Oral Histology, School of Dentistry of Ribeirão Preto, University of São Paulo. U nder certain clinical and anatomical conditions, periodontal surgery may be indispensable if single restorations or extensive oral rehabilitation is to be suc- cessful. Restorative techniques frequently damage the interproximal area where the COL, due to its morphologic concavity (which makes hygiene difficult) and to its histologically characteristic thin and non- keratinized epithelium, is vulnerable to inflammation caused by bacterial plaque. The proximal periodontal area includes the dental surfaces, the proximal marginal gingiva (dental papilla), gingival sulcus, junctional epithelium, and connective tissue fibers. A healthy coexistence between den- tal restorations and these periodontal struc- tures is difficult due to the characteristics of this area. The contact between teeth, prox- imity of roots, configuration of the inter- proximal gingiva, and difficult oral hygiene, depending on the localization of the restora- tion margins, make it impossible to main- tain an ideal interrelationship. Thus, any treatment that involves the interproximal region must consider this area as a whole, taking into account the teeth, gingival tissue, and the interrelation between them and recognizing the morphologic and physiologic needs which, if not appropri- ate, must be surgically modified. Cohen 1 described the interdental papilla and its tissue histology and pointed out the vulnerability of this important peri- odontal area. Analyzing the pathology of interdental tissues, Cohen 2 reported sig- nificant differences between the oral mu-