Radiographic Evaluation of Second Molar Substitution

Abstract

INTRODUCTION: Extraction of first permanent molars (FPM) is unavoidable in pediatric dental patients considering their high rate of caries and enamel hypoplasia. The national guidelines in the United Kingdom recommend extracting the FPM between 8-10 years of age, and when the second molar (SPM) demonstrates early root bifurcation development. Several recent retrospective studies reported contradictory findings and identified additional predictive variables. Aims: 1) to evaluate the outcome of spontaneous SPM substitution following extraction of FPMs in pediatric patients, and identify pre-extraction radiographic variables associated with success; 2) to test the variables described by Patel et al 2017 in their predictive model for success in the mandibular arch: mesial angulation of the SPM and presence of the third molar (TPM) (1).METHODS: The charts of 162 patients were assessed for a total of 138 maxillary quadrants and 168 mandibular quadrants. A pre-extraction panoramic radiograph was evaluated for 1) SPM developmental stage, 2) presence or absence of a developing TPM and 3) angle of the mandibular SPM relative to the occlusal plane. Chronological age at time of extraction and gender were recorded. A post-extraction radiograph was used for outcome assessment. RESULTS: Successful space closure was observed in 82 percent of maxillary quadrants and 51 percent of mandibular quadrants. In the maxillary arch the SPM developmental stage was statistically significant, with the highest odds for success associated with the earlier stages of SPM development compared to the later stages of development (p <0.05). In the mandibular arch, the chronological age at time of extraction was statistically significant, with the highest odds for success associated with the younger ages compared to the older ages (p <0.05). Mesial angulation of the mandibular SPM combined with presence of a TPM did not result in the highest probability for success. CONCLUSIONS: The Patel et al predictive model was not validated in this study population. The results suggest the primary importance of chronological age and SPM developmental stage for predicting a successful outcome. Extraction at a younger chronological age and earlier SPM developmental stage are significantly associated with success compared to extraction at later ages and stages.