Ectopic eruption of the maxillary first permanent molar: characteristics and occurrence in growing children.

The purpose of this study was to determine the characteristics and occurrence of the ectopic eruption of the maxillary first permanent molar in a sample of growing Spanish children. A descriptive, observational, retrospective study was done using the radiographs of 509 consecutive patients, who were in the first phase of mixed dentition. A method was designed to evaluate the amount of pathologic resorption of the second maxillary primary molar and the impaction of the first permanent molar measured in millimeters. Statistical analysis of the studied variables was done using chi-square, analysis of variance, and Pearson correlation coefficient. The frequency of occurrence was 4.3% with no differences in both sexes. Of these, 36.4% were unilateral and 63.6% bilateral with a right:left relation of 3:1. Of the 36 ectopic molars, 69.4% self-corrected spontaneously. In such cases, the pathological resorption of the root of the second maxillary primary molar and its adverse clinical implications were persistent. The relation between self-correction and impaction was 2.27:1. The average impaction on the right side was 2.91 mm and 1.6 mm on the left side. Correlation between the magnitude of resorption and grade of impaction was not observed. Although resorption was found on grades I and II, spontaneous self-correction could occur without arch length loss. However, on grade III or more, therapeutic intervention has to be done. The benefit of early diagnosis and treatment of the maxillary first permanent molar is the prevention of the premature loss of second maxillary deciduous molar and the resulting malocclusion.