Radiographic Evaluation of Permanent Second Molar Substitution After Extraction of Permanent First Molar: Identifying Predictors for Spontaneous Space Closure.

Purpose: The purpose of this study was to investigate pre-extraction variables associated with spontaneous space closure of the perma- nent second molar (PSM) following early extraction of the permanent first molar (PFM), and test an existing prediction model for the mandibular arch as the rates of spontaneous space closure are significantly lower in the mandible compared to the maxilla.

Methods: Pre-extraction panoramic radiographs of 162 patients (138 maxillary and 168 mandibular quadrants) between five and 15 years old at the time of PFM extraction were evaluated. The prediction model was applied to the mandibular quadrants. Postextraction radiographic evaluation was used for outcome assessment, with success defined as the presence of a visible contact between the second premolar and PSM without marginal ridge discrepancy.

Results: Success was observed in 82 percent of maxillary quadrants and 51 percent of mandibular quadrants. Maxillary PFM extraction between eight and 10 years or PSM Demirjian stage D or E demonstrated over 90 percent predictive probability for success. Mandibular PFM extraction at age eight years or PSM Demirjian stage D demonstrated 80 percent success. The prediction model did not add a more predictive value than chronological age or PSM Demirjian stage.

Conclusions: The prediction model was not validated in this study population. Chronological age and permanent second molar developmental stage were the primary predictors for successful substitution with the permanent second molar.