Efecto de la pérdida prematura de molares primarios sobre la relación horizontal incisiva

Premature loss of primary molars produces different malocclusions that include crowding, tooth impactation and alteration in molar and canine relation. The aim of this study is to determine the effect of premature loss of primary molars on the incisor overjet. The design is documental, retrospective, and observational. Orthodontic records (dental charts, photographs and x-rays) of 209 patients ages 4 to 15 years-old were examined. Overjet was considered normal (group 1) when the incisal border of the lower incisor occluded with the palatal surface of the upper incisor, increased overjet (group 2) when a positive distance was notes and negative overjet (group 3) when incisal borders were edge to egde or in cross bite. Data were analysed using Pearson´s test (p?0,001). 22% (45 patients) presented with premature molar loss, no significative difference between genders was noted and prevalence was higher for the 7 to 9 year-old group. Patients with premature molar loss were classified according to overjet;, 6 (13,3%) were included in group 1; 12 (26,7%) in group 2 and 27 (60%) in group 3. The mean number of lost molars in group 3 was 4,7; higher than the other two groups. A positive association was found between number of lost molars and prevalence of anterior cross bite. Premature primary molar loss has a statistically significant positive association with anterior cross bite, that may be related with lack of vertical posterior occlusal support and protrusive mandibular displacement.