General experimental procedure: A prospective, longitudinal, multicentric, randomized open study. Patients will be randomized into two groups: dental avulsion only or dental avulsion and PRF. For both groups the initial management is surgical (bone curettage + PRF for the PRF group).The follow up is spread over one year with 10 visits. Each patient will undergo a clinical and photographic examination with a complete radiological check up(OPT),a standard biological blood test (blood count with haemogram (NFS) and a thorough calculation of the quantity of BP administered. The appearance of OCN or of any delay in cicatrisation will be documented by a histological biopsy, a bacteriological swab test and X-ray.