This multi-center study evaluated periodontium visibility during natural and forced smile based on a new classification. The study population consisted of 576 patients (364 women and 212 men) aged from 21 to 78 years. All the participants teeth from first right premolar to first left premolar were present and the periodontium was healthy. Clinical photographs of the participants smiles were taken and the smile line analyzed according to the following 4 classifications: 1) more than 2 mm of marginal gingiva visible or more than 2 mm apical to the cemento-enamel junction visible for the reduced but healthy periodontium; 2) between 0 and 2 mm of marginal gingiva visible or between 0 and 2 mm apical to the cemento-enamel junction visible for the reduced but healthy periodontium; 3) only gingival embrasures visible; and 4) gingival embrasures and cemento-enamel junction not visible. Patients were also classified by age group and gender. With natural smile analysis revealed the following: Class 1, 4.69%; Class 2, 8.16%; Class 3, 44.79%; and Class 4, 42.36%. With forced smile analysis revealed the following: Class 1, 22.22%; Class 2, 21.35%; Class 3, 45.49%; and Class 4, 10.94%. The eriodontium was more visible in the forced smile than in the natural smile. Age and gender influenced the position of the smile line for only the natural smile. Concern was expressed about esthetics by participants in 89.06% of the cases. Examination of periodontium visibility must be performed both for natural and forced smile.
Keywords: smile, smile line, aesthetic, periodontium