Alveolar bone regeneration for immediate implant placement using an injectable bone substitute: an experimental study in dogs.

BACKGROUND The aim of the present study was to assess the efficacy of a ready-to-use injectable bone substitute for bone regeneration around dental implants placed into fresh extraction sockets. METHODS Third and fourth mandibular premolars were extracted from three beagle dogs and the interradicular septa were surgically reduced to induce a mesial bone defect. Thereafter, titanium implants were immediately placed. On the left side of the jaw, mesial bone defects were filled with an injectable bone substitute (IBS), obtained by combining a polymer and biphasic calcium phosphate ceramic granules. The right defects were left unfilled as controls. After 3 months of healing, specimens were prepared for histological and histomorphometric evaluations. RESULTS No post-surgical complications were observed during the healing period. In all experimental conditions, histological observations revealed a lamellar bone formation in contact with the implant. Histomorphometric analysis showed that IBS triggers a significant (P<0.05) increase in terms of the number of threads in contact with bone, bone-to-implant contact, and peri-implant bone density of approximately 8.6%, 11.0%, and 14.7%, respectively. In addition, no significant difference was observed when number of threads, bone-to-implant contact, and bone density in the filled defects were compared to the no-defect sites. CONCLUSION It is concluded that an injectable bone substitute composed of a polymeric carrier and calcium phosphate significantly increases bone regeneration around immediately placed implants.