The efficacy of porous titanium granules graft in peri-implant circumferential defects : an experimental study in dogs

Abstract

Purpose: To investigate the healing pattern and tissue response around the materials and to evaluate the efficacy of Porous titanium granules (PTG, Natix®, Tigran Technologies AB, Sweden) as a bioinert grafting material and to compare the potential of PTG with deproteinized bovine bone mineral (DBBM, Bio-Oss, Geistlich-Pharma, Wolhusen, Switzerland) in peri-implant circumferential defect in dogs. Materials and Methods: The premolars and molars of four mongrel dogs were extracted on both sides of the mandible. Eight weeks after extraction, circumferential defects (2 mm gap width, 5 mm depth) were created and three submerged type implants were placed. At the experimental sites, two circumferential defects were grafted with PTG or DBBM and the other defect was not grafted as a control site. After a period of 4 weeks, the same procedures were repeated on the opposite side of the mandible. The dogs were sacrificed after 4 weeks, and histological and histomorphometrical analyses were performed.Results: Some particles at the bottom and wall of the defect were surrounded by woven bone in DBBM group specimens after 4 weeks of healing. Osteoclast-like multinucleated cells were observed beside some particles which were not surrounded by new bone but connective tissue. Bone growth had progressed onto the surface of the particles in the middle of the defect. Some particles were connected to the implant surface or to other particles with newly formed bone at 8 weeks.Irregular and porous granules were surrounded by blood vessels, and woven bone was formed between the granules and from at the lateral and apical margins of the defect in 4 week specimens. In specimens obtained after 8 weeks of healing, new bone filled within the pores of granules, connected each granule and reached out onto the implant surface. Moreover some granules were completely locked in the new bone. Numerous osteocytes were observed in the newly formed bone. There was no soft tissue embedded within the defect and no multinucleated cell around the granules in any specimens and several titanium granules were found to be in direct contact with the implant in most specimens.The remaining defect depth in control group (3.01 ± 0.84) was greater than in PTG group (2.05 ± 0.36) and DBBM group (1.89 ± 0.20) at 8 weeks, and showed a statistically significant difference compared with DBBM group. DBBM had the highest bone-to-Implant contact (BIC [49.17 ± 5.03]) followed by PTG (48.41 ± 8.10) and control group (30.24 ± 12.75) at 8 weeks. However, there were no statistical significances among the three groups at 4 weeks and 8 weeks. Conclusion: Within the limitations of this study, it couldn''t be concluded clearly whether PTG as a graft material in circumferential defect is superior to DBBM through histometric evaluation of this study. However, PTG, the bioinert and non-resorbable material, could maintain the space without inflammatory response to allow new bone formation reaching at pore of granule, quite different from DBBM which elicit minimal inflammatory response around the grafted material. Therefore PTG could be favorably chosen as a graft material to resolve the contained large defect around the implant.