ABSTRACT
OBJECTIVES: This study aimed to evaluate the bone formation process in experimental defects created on rabbit calvarial, in which one of the bone defects was covered by the impermeable membrane before suturing the skin flap, while the other was closed only by the cutaneous flap. The experimental holes were filled only by the blood clot. MATERIAL AND METHODS: Sixteen New Zealand female rabbits weighing between 3.5 and 4 kg were used. Two experimental bone defects were made in the rabbit calvarial. The holes were filled only with the blood clot and one of them was covered with an impermeable polypropylene membrane. A histological analysis was made at 21 and 42 days following the surgery. Histological evaluation consisted of the following: 1. inflammatory process; 2. Bone repair; 3. Bone remodeling; 4. Presence of osteoid matrix and mineralization, and 5. Formation of hematopoietic tissue. Each characteristic was analyzed semi quantitatively. RESULTS: There was a statistical difference between the test and the control group at 21 days of healing in the following items: presence of cementation line (p = 0.012), presence of osteoid tissue (p = 0.012), and trabecular bone tissue development and mineralization (p = 0.012). A greater amount of lamellar bone tissue (mature) was also observed in the test group compared to the control group. CONCLUSION: The semiquantitative analysis showed that at 21 days there was a superiority of the repair process in the test group; at 42 days there was no significant difference in bone formation between the two groups; and that the polypropylene membrane is feasible to be used in GBR. CLINICAL SIGNIFICANCE: The impermeable polypropylene barrier is feasible for use in the guided bone regeneration technique. It can be used only on the blood clot, without the need for grafting, and can be easily removed a few days after surgery. These results are unprecedented.
ABSTRACT
BACKGROUND: A major challenge for dental implantology is to consistently obtain appropriate bone augmentation before implant placement. The aim of this study is to evaluate the effect of recombinant human bone morphogenetic protein 2 (rhBMP-2) associated with bone substitute materials beta-tricalcium phosphate (ß-TCP), biphasic calcium phosphate (BCP), and bovine bone mineral on vertical guided bone regeneration (GBR) in rabbit calvarium. METHODS: Four titanium cylinders were fixed to the calvarium of 22 rabbits. In group 1 (n = 10), three cylinders were randomly filled with one of the test materials, and one cylinder was filled with a blood clot (CL). In group 2 (n = 12), the cylinders were randomly assigned to the same materials and CL but with the addition of rhBMP-2. Bone labels were injected over the course of 13 weeks, and euthanasia was performed 14 weeks after surgery in both groups. RESULTS: The mean volume and area of tissue growth was greater in group 2 (with rhBMP-2) than in group 1 (without rhBMP-2), irrespective of the material used (P <0.001). The mean volume of tissue growth in the CL cylinder was smaller than that observed with all other materials (P <0.001) in both groups. The mean area of regenerated bone in the CL cylinder was smaller than that observed in the ß-TCP cylinder (P = 0.028). The histologic study revealed more lamellar bone in the rhBMP-2 group, with a greater level of biodegradation of all the bone substitute materials tested. CONCLUSION: The use of rhBMP-2/absorbable collagen sponge (ACS) combined with all of the bone substitute materials tested resulted in a greater amount of bone formation than that produced with the bone substitute materials alone or rhBMP-2/(ACS) and CL using the rabbit calvarium GBR model.