The Effect of the Injectable Bovine Collagens (Zyderm(R)) on the Repair of Critical-Size Defect in Rat Calvaria

This study was designed to examine the capacity of injectable bovine collagen(Zyderm(R)) to mediate the repair of critical size defects of rat calvaria. Thirty-six rats were randomized into six groups(n=6) and an 8-mm circular calvarial defect was made in each rat. In Group I, defects were left untreated. Defects in Groups II and III were implanted with Zyderm I(R) and Zyderm II(R), respectively. These three groups were evaluated in the 6th week after the operation. The defects in Groups IV, V, and VI received the same treatment as in Groups I, II, and III, respectively and were evaluated at postoperative 12th week. Results were examined by gross and histologic findings, simple radiographic study, and radiodensitometric analysis for bony density quantitatively. By gross and simple radiographic findings, defects with Zyderm(R) implantation showed thick coverage and focal radioopacity within defect area, but non-treated animals showed only fibrous healing. Histologically collagen pocket and woven bone were coexisted over the defect at postoperative 6th week, but the regenerating bone appeared much robust in Group III. At postoperative 12th week, there was a well-organized lamellar pattern of new bone formation, especially on the periosteal side of the defect. In the radiodensitometric analysis, all groups of Zyderm(R) implantation showed significant bony healing. There was also statistically significant difference between Group II and Group III at 6th week. Compared with Group V, however, Group VI did not show significant bony healing at 12th week. Additionally, prolonged implantation period allowed more complete healing of the defects with the same concentration of collagen. In conclusion, Zyderm(R) appeared to be an effective mediator of bone regeneration in this critical size calvarial defect model and its concentration had an effect on bone healing in the early period.

Stability and Efficacy of Titanium in Osteointegration in a Rabbit Model

Osteointegration with titanium implant has become a highlight having titanium implant tightly fixed in the bone with prosthesis attaching over it. The procedure is relatively simple with no morbidity of donor site and ensues superior shape aesthetically. However, the stability of it has been in question, therefore an experiment was performed to study the actual stability and periosteal formation around the implant. This study presents a histomorphometric and biomechanical comparison of bone response between titanium and stainless steel placed in the tibia of 5 rabbits. Two implants were placed in tibia of rabbit; titanium implant in left and stainless steel implant as a control in right. As a titanium implant, Brnemark implant with depth of 4 mm and diameter of 3.75 mm which has actually been used in the reconstruction of ears was used, and the stainless steel was manufactured in the same way as titanium implant. After a healing period of 3 months, the average removal torque was 8.2 Ncm for the stainless steel implants and 26.5 Ncm for the titanium implant. Histomorphometric study revealed that the stainless steel screw demonstrated rough and irregular contact surface with partial formation of new bone and the titanium implant demonstrated smooth contact surface with a good formation of new bone. In conclusion, the results indicated that titanium surfaces achieved greater periosteal bone formation over stainless steel surfaces and provided enhanced mechanical interlocking.