Osteogenic Regenerative Ability of Hydroxyapatite and Tricalcium Phosphate (Osteon III) in Rabbits

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Phosphate (Osteon III) in Rabbits
allografts may be more desirable in some cases, but the possible immune reaction and infection transmission limit their application. (1,2,3,4)To overcome these limitations, various natural and synthetic biomaterials such as bone substitutes made of various composite structures have been introduced to accelerate and improve the process of bone regeneration. (5,6)     The inflammatory response degree shown in (Table 1).

Table (1):
The inflammatory response degree (21) Grade At day 28 after surgery, the borders of both groups were not detected, and Osteon III group showed a higher radio-opacity and as shown in (Figure 4 C).Histopathology Assessment: At day 7, histological findings in the control group showed granulation tissue formation with inflammation (score 3) and scanty amount of new bone formation (bony spicules) and as shown in (Figure 5).In regard to bone surface area and throughout the periods of study, the osteon III material showed greater bone surface area formation with a statistically significant difference and as shown in (Table 3).In addition, a higher number of Osteoclasts was observed in the Osteon III defect when compared with the control defect and a statistically highly significant difference disclosed between both groups at days 14 and 28 and shown in (Table 5).

DISCUSSION
In the current study, the radiographic results revealed a higher radio-opacity in Osteon III filled bone defects versus control defects due to new bone formation and a higher mineralization ration achieved with a slow degradation of Osteon III which coincided with results disclosed in some studies.The porocities act as a channel for cell migration and protien adhesion, diffusion of cells, angiogenesis and nutrients transportation.These porosities act as a nidus for formation of new blood vessels.
These events coincided with the results of -DOI: 10.33899/RDENJ.2024.132104.1145,© Authors, 2024, College of Dentistry, University of Mosul This is an open-access article under the CC BY 4.0 license (http://creativecommons.org/licenses/by/4.0/INTRODUCTION Bone defects may develop in various systemic and dental disorders.The conventional methods of bone repair commonly used, such as autografts and allografts have their own shortcomings and drawbacks.Auto grafts are limited in terms of the availability of materials and may result in donor site morbidity.Using
Histopathological response observed 0 -Nil No inflammatory cells seen in the field of operation 100X 1 -mild /scanty When inflammatory cells present in few numbers, less than half of the field 100X 2 -Moderate Inflammatory cells could be seen in more than half of the field 100X 3 -Sever/marked Inflammatory cells present in large numbers more than 3/4 of the field 100X All parameters were measured using special computerized image analysis soft ware named OMAX Toupview that designed to be integrated with OMAX digital camera which is equipped to the light microscope used for study the specimen's visualization.SPSS program version 25. was used to conduct the radiographically and histo-morphometrically analysis.Data were presented as means and standard deviation and analyzed by independent Ttest.The significance was set at p < 0.05.RESULTS Radiographic Assessment: At day 7 after surgery, the defect filled with Osteon III showed a higher radio-opacity compared with the control defect.The margins of the defect in the control group were clearly round compared with the Osteon III defect group in which the borders appeared obstructed and as shown in (Figure 4 A).At day 14 after surgery, the borders in the control group were still detected, while the borders in the Osteon III group were barely detected and material still detected and as shown in (Figure 4 B).

Figure ( 6 ):
Figure (6): Histological section of M group7 days after surgery at 40 X magnification.H&E stain .At day 14, histological findings in the control group showed granulation tissue formation with inflammation (score 1) and moderate amount of new bone formation (bony spicules) and as shown in (Figure7).

Figure ( 7 ):
Figure (7): Histological section of control group14 days after surgery at 40 X magnification.H&E stain.On the other hand, in the study group defects, histological observations showed the material in red color and granulation tissue characterized without inflammation (score 0) and moderate amount of new bone formation (bony spicules) and as shown in (Figure 8).

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It was noticed that the degradation of ceramics (i.e. by its solubility properties and resorption activity of osteoclast) which depends on the HA/ β -TCP ratio within its composition, they observed that solubility influences the pattern of osteoblastic resorption activity in terms of shape and distribution of resorption lacunae.For example, in pure β-TCP, lacunae appear discontinuous like a chain of small islands whereas they are large and continuous on BCP (resorption activity β -TCP>BCP>HA) resembling those on bone.In addition, the shift in functional phases of osteoclast from resorption to migration seems to occur earlier on β -TCP than on BCP with different HA/ β -TCP ratio. )11 (By controlling the ratio of HA-β TCP of BCPs, it should be possible to control not only the resorption rate of BCPs but also the release of Ca+2, P in the vicinity of bone cells, and consequently modulate the biological properties of BCPs.Some free ions Ca +2 and inorganic P released could thus trigger the osteogenic differentiation.The results of the current study displayed an enhancement of bone regeneration when using Osteon III material as the biomaterial resorbs free calcium and phosphate ions released and the change in the ions concentration stimulate formation and differentiation of osteoblast and eventually bone formation either by directly response or by the expression of Ca +2 binding-proteins and Ca 2+ incorporation into the extracellular matrix. )12,13, 14(Moreover, the increase in inorganic phosphate (Pi) has also been shown to act as a specific signal, affecting the expression of various genes implicated in the proliferation, differentiation, mineralization and apoptosis of skeletal cells.In addition, by hydrolyzing inorganic pyrophosphate ions (PPi) into Pi, ALP promotes type I collagen mineralization by preventing the inhibitory action of PPi on mineralization.A sustained release of Pi was shown to upregulate the mineralization process of collagen by overriding the inhibitory effect of PPi. )13,15(The results of the current study came into agreement with Puttini et al. (2019). )12(Biphasic calcium phosphate is made from hydroxyapatite (HA) Ca10 (PO4) 6 (OH) 2 and tricalcium phosphate Ca3(PO4) 2 and are definitely considered the gold standard of bone substitutes in bone reconstructive surgeries. )16(Its extent of dissolution depends on the β -TCP/HA ratio, the higher the ratio, the higher the extent of dissolution. )5(Biphasic calcium phosphate has the advantages of providing better bioactivity and controlling resorption and solubilization of the scaffold and this in turn enhances stability leading to better bone ingrowth. )17(The HA in this scaffold provides better mechanical properties while the TCP provides a better biodegradation rate.The properties of the BCP manipulated by the composition ratio of HA/TCP may be the reason behind the increase in the number of osteoclast along the period of study. )4(while the of scaffold provided by Osteon III ( 80% porocity and a particle size of 1.0-2.0mm)may be the reason in the increase in number of osteoblasts along the period of study. )18 (

Table ( 4
): Statistical analysis of osteoblast numbers represented as mean and standard deviation of mean at significant level≤ 0.05.