Evaluation of Bone Formation in the Rabbit Periosteum on Titanium Plate Coated
With or Without Hydroxyapatite
Aung Bo Bo Thike, Kazuhiro Kon, Wataru Kouzuma, Sawako Kawakami, Shohei Kasugai
Department of Oral Implantology and Regenerative Dental Medicine, Tokyo, Japan
Many studies have been shown that periosteum plays an important role in osteogenesis. Biocompatibility of titanium coated with hydroxyapatite (HA), favoring the bone regeneration has been previously reported.
The aim of this study was to evaluate the subperiosteal bone regeneration on the titanium plate coated with or without hydroxyapatite using microcomputed tomography and histology.
Materials and Methods
Japanese male, six white rabbits, weighing 2.9 to 3.2 kg, were used in this study. Totally 24 titanium plates (size:5 x 5 x 0.5mm) coated with or without HA were used (n=12). Titanium plates with Hydroxyapatite were inserted subperiosteally on the right or left side of calvarium and on the tibia by facing the surface coated with Hydroxyapatite toward periosteum. Titanium plates without Hydroxyapatite were placed on the other side of calvarium and on the tibia respectively. Rabbits were sacrificed after 4 weeks. Tissues specimens were analyzed with a high-resolution microcomputed tomography(CT) imaging system and histologically after preparing non-demineralized sections.
Figure 1. Photographs of the surgical procedure.
A) Skin and periosteum were reflected on the calvarium.
B) On the right side of calvarium Ti plate with HA(Black arrow) and on the left side Ti plate without HA(White arrow) were inserted below the periosteum.
C) Skin and periosteum were reflected on the Tibia.
D) Ti plate with or without HA was inserted below the periosteum of right and left Tibiae respectively.
In Micro CT and histological examinations, bone formation was observed more on the HA-coated titanium plates than the titanium plates without coating on the parietal bone, whereas the difference of bone formation was not detected between the titanium plates coated with or without HA on the tibiae.
Figure 2. Micro CT images showing the horizontal view of newly formed bone (showing in white color) on the titanium plates. Scale bar = 8 mm. A) Calvarium (Ti plate without HA), partially expending bone was observed. B) Calvarium (Ti plate with HA), the surface of the plate was almost covered by newly formed bone. C) Tibia (Ti plate without HA), newly formed bone was observed on the side of the plate. D) Tibia (Ti plate with HA), newly formed bone was observed almost covering the surface of the plate. Titanium plate with hydroxyapatite (HA).
Figure 3 Graphic representation of the mean and standard deviation of bone volume among two groups at 4 weeks. P<0.05
The statistically significant difference was observed between calvarium model with Ti with HA and Ti without HA. There was no statistically significant difference on Tibia model.
A) Calvarium (Ti plate without HA), newly formed bone could be seen on the side of the plate.
B) Calvarium (Ti plate with HA), newly formed bone could be seen on the surface of the plate. Bone was also observed under the plate.
C) Tibia (Ti plate without HA), more bone formation was formed on the side of the plate
where the plate was touched with the periosteum.
D) Tibia (Ti plate with HA), the plate was separated from the tibia and covered with thin connective tissue.
Figure 4. Representative histological images stained with toluidine blue. Scale = 300µm. Newly formed bone (NB). Host bone (HB).
In Tibia model, the curvature of the tibia and stability of Titanium plate may influence the new bone formation on the titanium plate. Therefore, the better bone formation was seen on the flat bone surface of the calvarium. In this study, bone formation was determined at 4 weeks of healing period and newly formed bone was seen in all of the specimens. The favorable bone formation was observed in the calvarium model with the HA-coated Ti plate. This suggested that HA-coated Ti plate might induce bone formation on the flat and stable surface. Most of the newly formed bone can be seen on the side of the titanium plate. It was probably due to the tenting effect of the periosteum on the plate.
The responses of the periosteum of calvaria and tibiae to HA and titanium are different. Periosteum of calvarium produces more bone without HA coating.
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