J Periodontol • July 2001 901 Evaluation of the Dentogingival Area During Early Plaque Formation* Patrícia Weidlich, Maria Antonieta Lopes de Souza, and Rui Vicente Oppermann Background: The aims of this investigation were to evaluate the pattern of supragingival plaque formation in the dentogin- gival area within 96 hours after abstinence from mechanical plaque control and to clinically analyze the gingival inflamma- tory response observed. Methods: Six male volunteers, 20 to 23 years of age, had their upper incisors and cuspids polished. Four independent periods of no mechanical plaque control – 24, 48, 72, and 96 hours – were instituted. In each period, plaque was disclosed and standardized individual photographs were taken. Impressions were taken and replicas were analyzed by scanning electron microscopy. Gingival crevicular fluid (GCF) was collected at baseline and 96 hours. The height of the gingival papilla was measured at baseline, 24, and 96 hours. Results: Results showed the presence of a plaque-free zone (PFZ) along the gingival margin up to 72 hours. After 96 hours, there was a significant reduction in the presence of PFZ in the proximal thirds of the buccal surface when compared to the other experimental periods. At the end of the study, there was a significant increase in the GCF flow as well as edema of the interdental papilla, when compared to baseline values. Conclusions: The PFZ observed during the initial phase was less apparent at the 96-hour period. At this time, there was an increase in the gingival inflammatory response, represented clin- ically by increased GCF flow and edema. J Periodontol 2001;72: 901-910. KEY WORDS Dental plaque/etiology; dental plaque/prevention and control; gingival crevicular fluid/analysis; inflammatory response. * Graduate Program in Periodontology, Dental School, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil. D ifferent approaches have been used to study the colonization pattern of dental surfaces. Some studies examine dental plaque on nat- ural teeth, using different classification systems. 1-3 Others investigate plaque formation on tooth sections or artificial substrates, which are placed in the oral cavity or attached to teeth. 4-8 More recently, photographic records and planimetry have been proposed. 9-13 Early plaque formation has also been examined under light and electron microscopes. 4,14-18 The studies that analyze the topog- raphy of the initial supragingival plaque formation through scanning electron microscopy (SEM) show the presence of a zone with an absence of microbial deposits, which is located between the plaque bulk and the gingival mar- gin. 19-21 In the subgingival area, the presence of a “plaque-free zone” is also described, which is located between the apical border of the subgingival plaque and the most coronal cells of the junc- tional epithelium. 19-24 However, most of these studies were performed on extracted teeth; 19-21 thus, the dynamics of the relationship between plaque bac- teria and the surrounding tissues, par- ticularly the gingival sulcus, cannot be observed. The supragingival plaque formation process has intra- and interindividual differences. The rate of plaque growth differs with time, 1,9 tooth type, dental arch, 1,12 and period of the day. 11,12 As a result, different topographic plaque- growth patterns may be observed. 11,25 Local factors may interfere and mod- ify plaque growth. Diet-related aspects such as consistency 26 and composition, in particular the presence of sucrose, 27-29 are some examples. Furthermore, the