Effect of β-tricalcium Phosphate and Porous Hydroxyapatite Bone Substitutes on Bone Regeneration in Alveolar Bone Defects Around Dental Implants
When a sufficient bone mass or favorable bone quality is not available at the implant site, generally, fresh autologous bone transplantation is performed. However, to obtain autologous bone, surgical stress is inevitably applied to the healthy donor region, and the collectable amount of bone is limited. Thus, bone substitutes prepared with various materials have been investigated to substitute for autologous bone. Although artificial materials have no risk of infection compared to other body-derived materials, the clinical outcomes are poorer than those using other bone substitutes. Thus, we filled experimental alveolar bone defects around dental implants with 2 types of bone substitute, and histologically investigated their influences on new bone formation.
Materials and Methods:
Nine female beagles weighing about 10 kg were used for the experiment. The bilateral lower premolars were extracted under general anesthesia. After 3-month observation of the course and osseous healing, a 5.0 x 10-mm bone defect was prepared in the alveolar bone of each extracted tooth using a trephine bur under saline irrigation. Defects were made bilaterally (4 sites in total). Implants were placed in the distal regions of the defects, and divided into groups for filling of the peri-implant bone defect with porous hydroxyapatite (HA), autologous bone, and β-tricalcium phosphate (β-TCP), and without filling (control). The wounds were completely closed. To confirm new bone formation, bone-labeling agents (tetracycline and calcein) were subcutaneously injected before and after implant placement. The samples were collected after 2, 4, and 8 weeks.
Methods of data analysis:
The implant stability index was measured as an evaluation method. Tissue preparations were subjected to Villanueva Bone staining. The histology was observed, and the bone morphology was measured, mainly in the center of the implant, using a bone morphometry system (Histometry RT digitizer) and software (CSS-840 cancellous bone morphometry version, System Supply Co., Ltd.).
Results:
The bone mass increased in the β-TCP group, but no increase was noted until 8 weeks in the HA group. In the autologous bone group, the number of osteoblasts was significantly higher than those in the other groups. In contrast, no significant difference was noted between the β-TCP and control groups, and osteoblasts did not increase throughout the 8-week period in the HA group.
Conclusions:
The number of osteoblasts in the β-TCP group was not significantly different from that in the control group, and that in the HA group was lower than in the control group, suggesting that both HA and β-TCP had only a low cell-inducing ability. However, regarding the bone mass, new born formation was induced earlier in the β-TCP than in the HA group. In the HA group, the material was not absorbed by osteoclasts because it is non-absorbable, which may have delayed the infiltration of cells, such as osteoblasts, into the filled material, resulting in delayed new bone formation. These findings suggest that combination with autologous bone is desirable because filling with HA alone may delay new bone formation.
2 references:
1,Morikawa S.Comparative study on β-tricalcium phosphate and hydroxyapatite as bioactive artificial bone fillers.Tokyo Jikeikai Medical Journal 200;115:193-207
2,Sugawara A. Understanding bone and implant treatment though HA.The Journal of Oral lmplants 2011;45:65-71.2011