An open, prospective, randomized, multicenter study focused on the ridge diminution in case of grafting of fresh extraction sockets with Bio-Oss Collagen, Bio-Gide (Geistlich Pharma, Wolhusen, Switzerland), placing Dentsply implants (Astra Tech System).

The removal of at least 2 adjacent teeth would cause more advanced hard tissue loss during healing than that occurring after removal of a single tooth with adjacent teeth present. In order to maintain the dimension of the ridge following tooth removal, bone grafts and bone substitutes have also been placed in the extraction socket. So far no data have been reported on the effect of removal of multiple adjacent teeth on bone loss at various aspects of the edentulous sites. Furthermore, the potential effect on ridge contraction of implant placement in multiple fresh extraction sites is not documented. Therefore, the objective of the study is to evaluate the possibility of counteracting un favourable ridge modeling after multiple tooth extractions by placing mineral bovine bone in the extraction sockets and covering the wound with a native collagen membrane. In addition, the possibility of placing implants in the grafted sites is evaluated after six month of healing. For these purpose 40 subjects with 2 or more fresh adjacent extraction sites in need of two or more implants replacing teeth will be enrolled. Ridge dimensional changes will be measured after 6 months of healing; marginal bone loss will be measured after 3-years follow-up from the baseline (prosthetic delivery).

Inclusion Criteria:intact extraction sockets following removal of the natural teeth defined by:

• a marginal dehiscence defect of any of the facial bone walls of 3 mm
• no facial fenestration present in the apical of the marginal bone crest

Exclusion Criteria:

• untreated rampant caries and uncontrolled periodontal disease
• uncontrolled diabetes or any other systemic or local disease or condition that would compromise post-operative healing
• unable or unwilling to return for follow-up or unlikely to be able to comply with study procedures according to investigators judgement.