THE USE OF PREMOLAR EXTRACTIONS WITH ORTHODONTIC TREATMENT DOES NOT GUARANTEE AN IMPROVED ERUPTION POTENTIAL OF THIRD MOLARS

Selection Criteria The authors conducted a search using 2 electronic databases (MEDLINE and Web of Science) for prospective and retrospective controlled clinical studies that compared orthodontic treatment groups with premolar extractions vs those without extractions concerning their effect on the eruption of the third molars. Studies were limited to articles published in English or French through April 2017. The initial search yielded 325 articles; 44 articles remained after title screening. After full-text assessment, 12 articles were selected that satisfied the inclusion and exclusion criteria. Each article was independently assessed for quality. Key Study Factor The inclusion criteria were as follows: prospective or retrospective controlled clinical studies of a group receiving premolar extraction with comprehensive orthodontic treatment and a group receiving comprehensive orthodontic treatment without premolar extractions. Exclusion criteria included those articles without adequate control groups with orthodontic treatment but without extraction, case reports, case series, reviews, studies without adequate statistical significance tests, and deemed methodological quality assessment of,7 (based on the National Heart, Lung and Blood Institute analysis). 1 Main Outcome Measure The primary outcome measurements were the rate of third molar eruption, the change in retromolar space, and the angulation of the third molars after treatment. Main Results Eruption Rate Four studies compared eruption rate of the mandibular third molars and found that all had higher rates of eruption in the premolar extraction group. Two studies that examined the maxillary third molar eruption rate noted similar findings in the premolar extraction group. Retromolar Space Five studies focused on the available retromolar space for mandibular third molars; they noted that there was more space available for the extraction group than the non-extraction group. In the maxilla, 1 study noted increased posterior space available in the extraction group. Uprighting Two of the 6 studies that examined mandibular third molar uprighting noted that angular positioning of the molars was more conducive to eruption in the premolar extraction group than in the nonextraction group. However, 4 of the other studies did not find a significant difference between the extraction and nonextraction groups for mandibular third molars. Two studies examined the maxillary third molars and noted a more eruption-conducive angulation for the extraction group than the nonextraction group. Conclusions Premolar extractions can lead to a mesial movement of the posterior buccal segments, increasing retromolar space, and may produce eruption-favorable anticlockwise rotation of the third molars. However, the authors noted that premolar extraction therapy coincident with orthodontic treatment does not guarantee conclusively the eruption of third molars.