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.