Preorthodontic socket preservation after tooth extraction is intended to enhance favorable dentoalveolar ridge morphology and architecture, and facilitate orthodontic tooth movement (OTM) and extraction space closure. This 13-year-old skeletal Class II case presents a unique opportunity to evaluate and compare the OTM extraction space closure by means of a split-mouth analysis in a single patient. The comprehensive orthodontic-periodontal treatment included nonsimultaneous extraction of the bilateral periodontally compromised mandibular first molars and the eruption of bilateral impacted mandibular canines. While the right post-extraction space underwent a natural healing process, the left one was grafted using 4BONE BCH (hydroxyapatite β-tricalcium phosphate [HA-β-TCP], HA 60%, and β-TCP 40%). The 3-year multidisciplinary treatment approach resulted in Class I relationships on the right side and Class II on the left side, improved facial appearance, and dento-skeletal jaw relationships. However, a 3-mm residual alveolar space remained unclosed on the grafted left-site, along with an unerupted left third molar. This split-mouth comparative analysis of the orthodontic space closure demonstrated a significant clinical difference in the outcome. Preorthodontic placement of HA-β-TCP grafting material on the left segment, proved to be an obstacle for OTM extraction space closure, hindering the establishment of good occlusion.