Effect of Recombinant Human Bone Morphogenetic Protein-2 on Bone Regeneration around Zirconia Implants in Canine Dehiscence Defects

Abstract

Objectives; Zirconia ceramics are biocompatible and have mechanical properties that make them suitable as materials for dental implants. Bone morphogenetic protein-2 (BMP-2) accelerates the bone regeneration around titanium implants. However, little is known about bone tissue response to zirconia implants in adjunctive therapy with recombinant human bone morphogenetic protein-2 (rhBMP-2). The objective of this study is to evaluate the effect of rhBMP-2 on bone regeneration around zirconia implants in canine dehiscence defects and to compare it with the corresponding response to titanium implants. Methods; Six beagle dogs were used. All mandibular premolars and first molars were extracted. After 3 months of healing, the three bone defects with diameter of 6.3mm were prepared with trephine drill on each side of mandible. Simultaneously, the buccal bone walls of defects were removed and the buccal dehiscence defects, approximately 4 mm in height from the crestal bone and 4 mm in width mesiodistally, were created. Following the installation of the ø3.3×8 mm implant in the center of defect, a circumferential gap occurred between the bone and implant that was 4 mm in height and 1.5 mm in width. On one side of mandible, one zirconia implant and one titanium implant were inserted in each defect that was filled with demineralized bone matrix (DBM) gel, followed by covering with resorbable membrane (BioGide). On the contralateral side, each defect was filled with rhBMP-2 loaded DBM gel, after treatments in the same manner. In remaining defects, a titanium implant and a zirconia implant were placed without gel and membrane. The three animals were sacrificed at 4 weeks and the remaining at 8 weeks for histometric evaluation. Results; The percentage of linear bone fill (LBF) in buccal dehiscence defects with BMP-2 in both of zirconia and titanium was higher than that of other groups. In particular, the mean LBF of zirconia with rhBMP-2 was significantly higher than that of zirconia with DBM gel at 4 weeks and 8 weeks (65.18% vs. 19.01% at 4 weeks, 70.09% vs. 24.29% at 8 weeks) and that of titanium with BMP-2 was significantly higher than titanium alone (75.02% vs. 13.64%) at 4 weeks. At 4 weeks, zirconia with rhBMP-2 exhibited the significantly higher level of bone to implant contact (BIC) in buccal dehiscence than zirconia without rhBMP-2 (24.30% in zirconia with rhBMP-2 vs. 4.55-11.24% in zirconia without rhBMP-2). At 8 weeks, the BIC of the zirconia and titanium with rhBMP-2 (19.56% and 20.19%, respectively) was significantly higher than zirconia alone and titanium with DBM gel (4.80% and 6.42%, respectively). In this animal study, it is concluded that the quantitative extent of bone regeneration around zirconia was comparable to that around titanium. The bone regeneration around zirconia implant was enhanced by rhBMP-2. The present results suggest that zirconia can be used as an effective alternative to titanium in adjunctive therapy with rhBMP-2 in anterior areas with insufficient quantity of bone.

Key Words; bone morphogenetic protein-2; zirconia; titanium; dehiscence defect