EFFECT OF HYDROXYAPATITE - BASED BIOGENIC PASTE ON 
RECONSTRUCTION OF OSSEOUS TISSUE IN SOSCED OF
 EXTRACTED TOOTH
Potapchuk A.
Medical Faculty of Uzhorod State University

SUMMARY
In an experiment on rabbits, reconstruction of the osseous tissue and an inflammatory reaction of the tissues around the tooth after filling of the extracted tooth socket with a hydroxyapatite-based paste were studied on the 7th, 14th, 30th and 90th postoperative days. It has been revealed that use of the developed ceramic material based on hydroxyapatite with addition of chonsuride preparation results into reduction of the healing period for the bone wound. Osteogenesis was noticed directly on the surface of hydroxyapatite granules, it testifying to significant osteointegrative properties of this material.

INTRODUCTION	

Substitution for defects of dentitions by means of implants is one of acute problems in modem stomatology. At present, active medical and biological elaborations are being done to look for various implantation systems enabling stimulation of osteogenesis in the area of implantation and strengthening of the bond of the osseous tissue with the implant [1, 2]. The most promising in this aspect are resolved materials, later substituted for with osseous tissue (4).
The Purpose of the Present Report is an experimental study of the effect produced on the reparative process in a tooth socket by the paste based on the granular hydroxyapatite (Kiev Institute of Problems of Materials, Academy of Sciences of Ukraine).
MATERIAL AND METHODS
In the experiment, 9 rabbits were used, with body weight of 2-3 kg and at the age of 8-12 months. All the manipulations were performed under general thiopental anesthesia. The 3rd mandibular tooth was extracted. After revision, the socket was filled with the paste based on granules (size =150) hydroxyapatite chonsuride preparation know as producing an effect on regeneration (3). For control, a similar operation was filled with a blood clot. In the both cases, the mucosa over the socket was taken in. The animals were taken out from the experiment by means of air embolism 7, 14, 30 and 90 days later. A portion of the jaw with the extracted tooth was isolated, and after standard histological procedures the material

was embedded into celloidin and micropreparations were made, they being stained with hematoxylin and eosin as well as with pycrofiixin by van Gisson’s method.
The state of soft tissues was analyzed, it enabling assessment of a local inflammatory reaction.

EXPERIMENTAL STUDIES
In the postoperative period, the animals from both the experimental and control groups revealed edema of paramaxillary and paramandibular soft tissues in the zone of operation; this edema disappeared by the end of the 3rd-5th day. Within a few postoperative days, the animals were adynamic and ate their fodder very bad; in this connection any rough vegetable diet within these terms was excluded from their ratio. Later, the state of the animals in the both groups became normal.
Analysis of micropreparations of the animals from the control group revealed that after 7 days the socket of the extracted tooth was filled up with fibrocellular connective tissue rich in vessels of the capillary type, with a great number of lymphocytes and macrophages. In the center of the socket, foci of polynuclear cells and necrotic detritus could be found After 14 days,	the fibcocelluiar tissue with a
higher density than on the 7th day was still revealed in the socket. This tissue was characterized by expansion of thick and consolidated bundles of collagenous fibers, and among them there were numerous cells of the fibroblastic line.
After 28 days, the tooth socket still had large territories made up of the fibrocellular

connective tissue. But near the socket walls, rough-fibrous osseous trabeculae, connected with the maternal bone, were formed.
After 90 days, expansion of the territories of the newly-formed osseous trabeculae, represented by a large-looped net, was noticed. The trabecular surface contained brightly colored laige osteocytes and osteoblasts. The maternal bone traces of reactive reconstruction.
The surrounding soft tissues revealed chronic inflammatory infiltrates.
In preparations of the animals from the experimental group with the use of the paste, 7 days after the operation, the socket had numerous granules of hydroxyapatite; their smaller part was among structureless oxyphilous masses, and the larger on was surrounded with the fibrocellular connective tissue having a great number of large cells of the fibroblastic line and few macrophages. Formation of a thin osteoid rim around single granules of hydroxyapatite was noticed. The surrounding soft tissues demonstrated signs of an inflammatory reaction; they were caused by presence of few small foci of polymorphonuclear leukocytes, phenomena of edema, foci of destructive-dystrophic changes in the mucosa. The changes revealed in the mucosa persisted up to 30 days.
On tile 14th day, around hydroxyapatite granules in the tooth socket, osteoblasts prevailed; they w'ere characterized by large size, brightly-colored cytoplasm and hyperchromic nuclei. Only in the central part of the socket small gubeniacula of the fibrocellular tissue were revealed; they were adjacent to granules of the ceramic material. On the periphery of the socket, young osseous trabeculae were formed; they were tightly connected with granules of hydroxyapatite and ibe maternal bone (Fig. 1).
After 30 days, on the whole territory of the socket the granules of hydroxyapatite were

REFERENCES
surrounded with newly-formed osseous trabeculae having high density of osteoblasts and osteocytes on their surface. The trabeculae formed a small-looped net.

Figure. Newly-formed osseous trabeculae around fragments of hydroxyapatite ceramic (C). 14th day after operation. (H&E. x 80).
After 90 days, the socket revealed single fragments of hydroxyapatite, they having various size and being closely united with osseous trabeculae of the reclaimed product. The osseous tissue of the latter product had a laminar structure and turned into the socket wall without any visible border.
Thus, the use of the hydroxyapatite-based composite material resulted into reduction of the healing period for the bone wound. Osteogenesis took place directly on the surface of hydroxyapatite granules, it contributing to tight adhesion of the newly-formed osseous tissue and the ceramic material.

1.	Абоянц P.K., Истранов Л.П., Шехтер А.Б. и соавт. Стоматология. -1996.-N 5.-С.23-25.
2.	Григорьян А.С., Байматов М.Б., Рудько В.П. и соавт. Стоматология. 1992.-N 2- С.51-53.
3.	Иорданишвили А.К. Новое в стоматологии .-1995.-N1.-C.19-22.
4.	Назаров С.Г., Григорьян А.С., Малорян Е.Я Стоматология. -1990. -N 3. -С.14-16.