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B o n e a u g m e n t a t i o n u s i n g p o r o u s (cid:696)-TC PB o n e a u g m e n t a t i o n o f c a n i n e f r o n t a l s i n u s e s u s i n g a p o r o u s (cid:696)-t r i c a l c i u m p h o s p h a te (cid:696)-TCP at four weeks, new bone formation had already started. Moreover, the porous (cid:696)-TCP particles had been completely absorbed and replaced with new bone at 12 weeks. New bone formation in the area of the bone window re- duced between 12 and 24 weeks. No bone exists originally in the area of the bone window; thus, the newly formed bone will be absorbed over time. Mechanical stresses, such as occlusion, may inhibit the absorption of the newly formed bone. Although (cid:697)-TCP was an acceptable bone substitute material for augmenting maxillary sinus bone formation, it was likely to continue increasing and would have been progressively replaced over a longer time.27 However, pro- longed bone augmentation is disadvantageous. Conclusion Sinus floor augmentation is a safe and elegant surgical procedure before implant insertion. The porous (cid:696)-TCP tested is a biocompatible, osteo- conductive material that promotes new bone formation when used with integrated Ti im- plants, as demonstrated in this study on a canine frontal sinus model. However, the efectiveness and safety of this method need to be further evaluated before it can be clinically applicable. Competing interests The authors declare no conflicts of interest. Acknowledgments This work was funded by the Promotion and Mutual Aid Corporation for Private Schools of Japan’s Science Research Promotion Fund (Tokyo, Japan; No. 15-09). ceramics with 80% porosity.17 In this study, a comparison of the scatter plot data of the syn- thesized (cid:696)-TCP particles with that of (cid:696)-TCP data registered with the Joint Committee on Powder Diffraction Standards confirmed that these peaks appeared at the same angles. In addition, the Ca/P ratio of the product was 1.5, which ful- filled the requirements of the ASTM standards.18 Basic animal research on sinus lift has been conducted on dogs, sheep and rabbits.12, 19, 20 The canine frontal sinus is a size closer to the human maxillary sinus and allows accurate control of a large number of experimental models. In addi- tion, the canine frontal sinus is the largest among the canine paranasal sinuses and the canine sinus wall is covered with multiple rows of ciliated columnar epithelium, as is the human maxillary sinus.21 Moreover, the surgeon can approach both sides of the frontal sinus through a single incision because the left and right fron- tal sinuses are adjacent to each other. In the edentulous jaw and sinus-alveolar crest, the distance between the sinus and the alveolar bone is important in terms of implant treatment. A bone height of around 20 mm is required for dental implant treatment; therefore, sinus surgery is expected to promote bone for- mation to a height of more than 20 mm.22 Since the vertical length of the human maxillary sinus is about 28 mm, the top of the implant projects from the maxillary sinus floor into the elevation space of 20 mm.21 In this experiment, the top of the implant projected into the canine frontal sinuses. Therefore, the canine frontal sinus was considered a suitable experimental model of sinus surgery. The biological behavior of (cid:696)-TCP-based bio- materials has been analyzed in several in vivo studies.23–25 Kihara et al. performed an in vivo test using a rat model to observe the biodegra- dation process of particles (~300 μm diameter) of pure (cid:696)-TCP and found that the residual (cid:696)-TCP particles degraded without decreasing the volume of the transplantation region.26 Our pre- vious study evaluated the efects of combining poly(Pro-Hyp-Gly) and (cid:696)-TCP particles on bone formation in a canine tibial defect model.23 These particles did not induce inflammation; moreover, complete degradation and remodeling of the lamellar bone were observed with their use. This, to our knowledge, is the first study to inves tigate the efects of porous (cid:696)-TCP as a tissue- engineered scafold for maxillary sinus augmentation in a canine model. Although histo- logical images showed high levels of porous 50 Volume 3 | Issue 1/2017 Journal of Oral Science & Rehabilitation