[Surgical placement of third molars to replace other teeth: "spare wheels"].

INTRODUCTION: The prognostic improvement for dental auto-transplants is the result of a better understanding in the physiopathology of the periodontium and also of the refining of the technical operative procedure. This fact allows the use of third molars as donor site for the replacement of absent, or first or second badly decayed molars. DISCUSSION: This possible therapy is a supplement argument for the conservation of third molars and their extraction must be indicated only when the anatomic situation presents a pathological risk. RESULTS: If, in adults, it is possible to compare the advantages and disadvantages with the classical implant or prosthetic techniques, it should however be considered as first choice therapy for adolescents and young adults. Indeed, in these cases, the lower risk of root ankylosis avoids passive intrusion and the osteogenic effect of the desmodontium allows normal alveolar bone formation.