Histomorphometric Study on Healing of Critical Sized Defect in Rat Calvaria Using Two Different Bovine Grafts
Ewha University Clinical Postdoctoral Program
Xenografts such as deproteinized bovine bone substitutes are commonly used by dental clinicians for reconstruction of alveolar defects as alternatives to autogenous grafts. However, differences in the purification and manipulation methods of the bovine bone have led to commercially available products with different chemical properties and possibly different biological behavior. The objective of this study was to evaluate the feasibility of a new xenograft material Ti-oss® (Chiyewon Co., Guri, Korea) by investigating the degree of new bone formation compared with that of OCS-B® (NIBEC, Seoul, Korea) in critical size bone defects of rat calvaria.
MATERIALS AND METHODS
Forty 1-month-old Sprague-Dawley rats were used in the study. A periosteal flap was raised and an 8 mm trephine defect was created in the mid-portion of the calvaria. The animals were randomly allocated into four groups of 10 animals each as follows:
Group 1: The calvarial defect was left untreated.
Group 2: The defect was filled with deproteinized bovine Xenograft OCSB®
Group 3: The defect was filled with deproteinized bovine Xenograft Ti-oss®
The animals were sacrificed at 2 (n=5) and 8 (n=5) weeks of healing for histologic and histomorphometric analysis. At each period, the surface of new bone (mm) with each filling material was computed over sections of rat calvaria. The ANOVA test for variance analysis with Tukey's multiple comparison tests was performed to analyze the effect of healing period and experimental conditions (p<0.05).
Histological evaluation confirmed the effectiveness of the new material to promote new bone formation in rat calvarial bone defects. Areas of newly formed bone were presented at both 2 and 8 week healing periods.
Histomorphometric analysis showed the statistically significant difference between the groups (p<0.05) with a mean bone formation of 0.19 ± 0.04 mm (4.75%) for OCS-B® group, 0.26 ± 0.04 mm (6.5%) for Ti-oss® group at 2 week healing period.
At 8 weeks, a mean bone formation of 1.12 ± 0.11 mm (28%) for OCS-B® group, 1.50 ± 0.28 mm (37.5%) for Ti-oss® group showed the statistically significant difference (p<0.05).
Within the limits of present study, it was concluded that the newly investigated xenograft, Ti-oss®, revealed biocompatibility and effectiveness in bone formation. Ti-oss® could be proposed as a potential material for filling osseous defects. Further clinical trials of the new deproteinized bovine xenograft Ti-oss® are needed for an understanding its relevance in dentistry.
Figure 1. Procedures in rat calvarium (A: Elevation of periosteal flap; B: Creation of a defect 8 mm in diameter; C: Bone grafting)
Please click on the images for a comfortable view.
Figure 2. Histologic sections of control group at 2 and 8 weeks (H&E x10, x100).
(Note no bone within the defect site) A: 2-week healing period; B: 8-week healing period; arrow head: defect margin; CT: connective tissue; PB: pre-existing bone; H-E stain; original magnification: A-1, B-1 x10; A-2, B-2 x100).
Figure 3. Histologic sections at 2 weeks (H&E x10,x100). A: OCSB® B: Ti-oss®
arrowhead: defect margin; NB: new bone; P: bone graft particle; PB: pre-existing bone;
2) 8 week healing period
OCSB® group - more new bone formation was observed compared with the 2-week sections. The defect was filled in its lower portion with newly formed bone tissue grown from the defect margins and relatively large bony islands. Osteoblasts were seen on the newly formed bone tissue. Bone healing in the all specimens was incomplete. Even though some particles of bovine xenograft were surrounded by the new bone, originating from the defect margins, most of the graft particles were still surrounded by fibrous connective tissue
Ti-oss® group - an increased amount of new bone formation was observed compared with the 2-week sections. Most defects were filled with fibrous connective tissue in the superficial portion while the lower portion was filled with newly formed bone tissue. Some particles of bovine xenograft were embedded in the new bone, originating from defect margins
Histologic sections at 8 weeks (H&E x10,x100). A: OCSB®; B: Ti-oss®
arrow head: defect margin; NB: new bone; P: bone graft particle; PB: pre-existing bone; H-E stain
C. Histomorphometric evaluation
The results of the histomorphometric analysis are shown in Table Histomorphometric analysis showed the statistically significant difference between the groups (p<0.05) with a mean bone formation of 0.19 ± 0.04 mm (4.75%) for OCSB® group, 0.26 ± 0.04 mm (6.5%) for Ti-oss® group at 2 week healing period.
At 8 weeks, a mean bone formation of 1.12 ± 0.11 mm (28%) for OCSB® group, 1.50 ± 0.28 mm (37.5%) for Ti-oss® group showed the statistically significant difference (p<0.05).
At both 2 and 8 weeks, the new xenograft material Ti-oss® showed significantly greater new bone formation values compared to the OCS-B® group.
Table III. Mean and standard deviation of new bone area (mm, % n=5)
This investigation demonstrates three xenograft materials can fill the defect when it comes to bone grafting.
In this study, the following conclusions were reached.
1. The new deproteinized bovine xenograft Ti-oss® is biocompatible bone graft material.
2. The new deproteinized bovine xenograft Ti-oss® is effective in the healing of critical-sized osseous defects in rat calvaria.
3. The new deproteinized bovine xenograft Ti-oss® is competitive with the currently commercially available products in the healing of critical-sized bone defects in rat calvaria.
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