Experimental Study Of Bone Defects Repairing Around Dental Implants

Background :Localized alveolar ridge defects can occur, amongst other causes, as the consequence of tooth removal, periodontal disease or traumatic injury. These defects may result in unesthetic ridge deformities and insufficient bone volume for implant placement. In view of this, during the last few decades several procedures have been developed to preserve or restore alveolar ridge dimensions. Use is frequently made of biologic or synthetic materials to fill the existing bone defect. This is often combined with the application of a membrane, either to keep the material in place or to prevent ingrowth of connective tissue. Currently, autografts are still considered to be the golden standard for such bone reconstructive surgeries. On the other hand, autografts require a harvesting procedure, which is considered a negative factor because of additional morbidity and discomfort for the patient. Allograft bone has been widely used, which of course have several problems encountered when used, including immunogenicity and disease transmission such as hepatitis, loss of biologic and mechanical properties secondary to its processing and increased cost. Consequently significant strides have been made to search ideal bone graft substitutes. Various synthetic materials have been developed as bone substitute which include synthetic polymers,inorganic materials and some composite. Hydroxyapatite has the similar chemical composition with inorganic ingredient of bone tissue and offers excellent biodegradation and biocompatible properties. and interconnected microporosity are believed to improve osteo-conductive properties of material and promote timely resorption concomitant with the process of remodeling. According to internal porosity and microstructure , Hydroxyapatite divide into two type: dense Hydroxyapatite and poro- Hydroxyapatite. The aim of this study was to evaluate the clinical handling properties and bone behavior of poro-hydroxyapatite as a filler materialfor gaps around implants.Methods :One healthy mature (2years of age) male Beagle dog, weighing about 8kg, were used in this study. Ten BLB implants, creating gaps of 4mm×4mm×3mm, were inserted into femoral bone. Four different situations were tested: (1) implant + gaps; (2) implant + gaps, but covered with a collagen membrane; (3) implant + gaps that were filled with poro- hydroxyapatite; and (4) implant + gaps that were filled with poro-hydroxyapatite and covered with a collagen membrane. All implants were left in place for 12 weeks. Histological and quantitative histomorphometrical measurements overview new bone formation and bone implant interface ratio to analyze bone defect restoration.Results:Histological and quantitative histomorphometrical measurements demonstrated that implants + gaps had generally poor bone contact at the implant .Furthermore, fibrous encapsulation was observed in the gap part. In contrast, the presence of a membrane promoted bone ingrowth into the gap and also the bone contact at the implant base. Poro- Hydroxyapatite resulted in an almost complete filling of the gaps around the implant. Additional use of a membrane result in adjunctive benefits. Bone-to-implant contact at the implant was comparable with the implants provided only with a membrane.Conclusion :Poro- Hydroxyapatite used here showed excellent clinical handling properties and a superior bone behavior combined with a collagen membrane.