Wisdom tooth eruption secondary to localized lower molar mesialization in patients with aplastic lower second premolars

After localized space closure in the mandible it is desirable to preserve lower wisdom teeth as natural replacements for missing second premolars and as antagonists for upper second molars. The aim of this study was to determine whether this treatment method can obviate the need for prosthodontic restorations, implants, and third molar osteotomy. Furthermore the time point of possible third molar eruption was to be determined and whether further orthodontic interventions were required to achieve their alignment. The test group comprised 34 patients who exhibited agenesis of one or both lower second premolars (n = 45) in conjunction with a corresponding number of third molar tooth germs. Follow-up examinations were performed 2 to 8 years after conclusion of orthodontic treatment involving push-and-pull mechanics (PPM) without extraction of any contralateral teeth. The results of the clinical retrospective follow-up examination at consecutive post-treatment endpoints were compared with two orthodontic control groups (A: 4-premolar extraction group, B: non-extraction group). After an average of 4 years and 2 months, the percentage of fully-erupted third molars in the agenesis group with localized space closure was 82%, compared to 29% and 28%, respectively, in the controls. These differences were statistically significant (p < or = 0.01). The success rate in the agenesis group reached 94% when the 4- to 8-year results were considered in isolation. Compared with the contralateral (non-aplastic) side, teeth on the aplastic side erupted prematurely. In 9% of the cases, minor orthodontic interventions were required to exactly position the third molars. There is high probability that mandibular third molars can be preserved after localized space closure, obviating the need for prosthodontic restorations, dental implants, and third molar osteotomies.