The purpose of this study was to explore non-crystalline calcium phosphate glass as potential biomaterials in the regeneration of periodontal tissue. We prepared calcium phosphate glass with Ca/P ratio of 0.6 using the system CaO-CaF2-P2O5-MgO-ZnO and subsequent milling to 0.08~555.7 μm (average size; 167.95 μm). In vivo evaluation of the prepared glass was investigated using beagle dogs by 1-wall intrabony defect model. They were sacrificed after 8 weeks and alanlyzed histomorphometrically. No root resorption or ankylosis were observed in the experimental group. It can be examined that the prepared glass were effective in cementum regeneration in the early healing stage by Mann-Whitney U test, while there were no statistical significant difference between experimental and control group in the amounts of junctional epithelium migration, connective tissue adhesion, and alveolar bone regeneration. Further study is required to control the flowability as well as reduce the absorption rate in vivo. Introduction A couple of forms of calcium phosphate ceramic, HA and TCP, have been widely used in clinical practice for alveolar ridge augmentation, preservation of alveolar bone after tooth extraction and repair of periodontal osseous lesions [1]. The physical properties such as surface area, form of product, porosity, and crystallinity as well as chemical properties such as Ca/P ratio, elemental impurities, ionic substitution in HA, and pH of the surrounding area affect the rate of resorption and determine the clinical applications of the graft. Kamakura et al. reported that synthetic octacalcium phosphate enhanced new bone formation in rat skull defect [2]. Gauthier et al. reported that injectable calcium phosphate enhanced bone filling in extraction sockets and expressed osteoconductive capacities, and the biological properties of the mineral phase were conserved [3]. Recently it is reported that the amorphous calcium phosphate formation in the plasma-sprayed coatings on dental and orthopedic implants as well as metal substrates had a significant effect on the properties of the coatings, especially it increased the extent of dissolution. Earlier calcium phosphate glass obtained from the system CaO-P2O5-Al2O3 has been proposed for dental crown materials. This material can be expected to extend application field to biomaterials for hard tissue repair because of non-crystalline structure as well as low Ca/P ratio. Low Ca/P ratio and amorphous states provide the great extent of dissolution and resorption that allows the fast ingrowth of the surrounding bone. The purpose of this study was to explore the potential of as biomaterials for hard tissue repair. The purpose of this study is to evaluate the effect of the con-crystalline calcium phosphate glass on the regeneration of periodontal tissue in beagle dogs. Key Engineering Materials Vols. 240-242 (2003) pp. 391-394 online at http://www.scientific.net © 2003 Trans Tech Publications, Switzerland Licensed to Y.-K. (leeyk@yumc.yonsei.ac.kr) Yonsei University, College of Dentistry Korea All rights reserved. No part of the contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 128.134.207.85-10/03/05,04:03:28) Title of Publication (to be inserted by the publisher) Methods Calcium phosphate glasses with Ca/P ratio 0.6 were prepared from the system CaO-CaF2-P2O5-MgOZnO. Mixed batches were melted in a platinum crucible at 850C and poured onto a graphite plate at room temperature. As-quenched glasses were ground in an alumina mortar. Determined particle size of the powdered samples was 0.08 to 555.7 μm (average size; 167.95 μm). In vivo evaluation of the prepared calcium phosphate glasses was carried out using 4 beagle dogs. The surgical procedure was performed under the general anesthesia induced by the intravenous injection of atrophin (0.04 mg/kg) and the intramuscular induction with the compound of xylazin and ketamin, followed by the application of enflurane through inhaling. Routine dental infiltration anesthesia (2% lidocaine hydrochloride with 1/80000 epinephrine) was used at the surgical sites. The mandibular first and third premolars had been extracted in advance of the experimental surgeries, and the extraction sites had been allowed to heal for 8 weeks. 12 intrabony defects from 6 beagle dogs with 4 4 mm 1-wall intrabony defects were surgically created in the bilateral mandibular second and fourth premolars (Fig 1). Following root planing, a reference notch was made with 1/4 round bur on the root surface at the base of the defect. The experimental group was treated with the prepared calcium phosphate glass powders, while the control group just carried out a flap operation. The subjects were sacrificed 8 weeks after the operation. For the histometric analysis, the cementoenamel junction(CEJ) and the notch were used as reference points(bN) and the histometric parameters included defect height(DH), junctional epithelium(JE), connective tissue adhesion(CT), cementum regeneration(NC) and alveolar bone regeneration(NB) (Fig 2). Histomorphometric recordings from the four sections from each defect were used to calculate mean score for each animal. Statistical analysis was compared by Mann-Whitney U test. Root resorption and ankylosis was dischotomously scored when can be observed in one or more of the four sections for each tooth. Fig. 1. A surgically created Fig. 2. A schematic diagram depicting parameters 1-wall intrabony defect. used in histomorphometric analysis Results Histologically, the junctional epithelium showed tendency of apical migration, and inflammatory cell infiltration was minimal in all defect sites (Fig. 3A & 4A). Residual bone graft material and peculiar inflammation activity could not observed in experiment site (Fig. 4A). The connective tissue fibers exhibited parallel arrangement beneath the junctional epithelium (Fig. 3B, 4A & 4C). New cementum grew up prominently along root surface in experiment group than the control group, whose thickness was thicker in notch site (Fig. 3C & 4B). Limited resorption bays on the root surface were observed in most of the teeth (Fig. 4C). The magnitude of resorption appeared greater in the root surface without cementum than in the root surface covered by new cementum. No site had signs of ankylosis. Bioceramics 15 392