Evolution of the incisal relationship in a Central European population (1870-1970)
Résumé
Recent studies have supported the hypothesis that there is a tendency to evolution in the occlusal relationships of urban populations. Due to its role in the stomatognathic system and the hypothesis of the role of deep overbite in the appearance and development of TMD, particular interest is given to the incisal relationship and its evolution in urban populations. Incisal situation and relationship can be studied with anthropometric and cephalomatric determinants. This study compares the incisal relationship of two groups of young Caucasian adults born in 1870 and 1970, respectively. Twenty-four anthropometric and cephalometric points were analyzed for 30 subjects from each group. A statistically significant difference between the 1870/1970 samples was found for the following criteria (p < 0.001): overbite: 1.17/ 3.81, position of the free edge of the mandibular incisor, sagittal values (orthodontic norm PAO) 78.75 mm/82.88mm, position of the free edge of the mandibular incisor, vertical values 54.74 mm/58.87 mm, FMIA angle: 65.97 /58.4 and Angle classes: difference in distribution of the skeletal classes (Classes I, II and III) between the two populations (increase in Class II, 1970). Within the limits of this study results show a remarkable increase in overbite, a tendency towards a reduced prevalence of class III malocclusions and an increased prevalence of Class II malocclusions with vestibular position of the mandibular incisors.