Emiko Saito

Influence of Residual Bone on Recombinant Human Bone Morphogenetic Protein-2–Induced Periodontal Regeneration in Experimental Periodontitis in Dogs

BACKGROUND Previous studies reported that bone morphogenetic protein (BMP)-2 induced periodontal regeneration in animals. However, the effects of local host factors on bone formation when using recombinant human (rh)BMP-2 are unknown. The purpose of this study was to evaluate local conditions in recipient sites that affected periodontal regeneration following BMP implantation in experimentally induced horizontal defects in dogs. METHODS Experimental periodontitis was induced in the maxillary and mandibular premolars of six male beagles. The recipient sites were divided into four quadrants (maxillary buccal, maxillary palatal, mandibular buccal, and mandibular lingual sites). A polymer-coated gelatin sponge (PGS; 3 x 3 x 2 mm) was impregnated with 7.2 mul rhBMP-2 solution. The recipient sites in each quadrant were treated with physiologic saline/PGS and rhBMP-2/PGS (rhBMP-2 at 7.2 mug/7.2 mul). The dogs were sacrificed 12 weeks post-surgery, and healing was evaluated histologically. RESULTS Bone formation and connective tissue attachment were observed following rhBMP-2/PGS implantation. In the four recipient sites of the BMP-treated group, significant positive correlations were found between the width of residual bone and the height and area of regenerated bone (r = 0.791; r = 0.828; P <0.0001). The height of regenerated bone was also significantly correlated to the area (r = 0.891; P <0.0001). CONCLUSIONS The width of residual bone was one of the clinical host factors that affected bone regeneration following BMP implantation. However, it did not affect connective tissue attachment, cementum regeneration, and downgrowth of junctional epithelium.

Healing in transplanted teeth with periodontal ligament cultured in vitro.

Regeneration of connective tissue attachment is the ultimate goal of periodontal therapy. It has been suggested that periodontal ligament cells possess the potential to create new connective tissue attachment. However, as cells from gingiva and alveolar bone occupy the root surface during initial wound healing, population by periodontal ligament cells is limited in vivo. We have been developing a new periodontal regeneration technique using in vitro tissue culture of periodontal ligament remaining on a periodontally involved root. The purpose of this study was to examine the periodontal healing after transplantation of teeth with reduced periodontal ligament that had been cultured in vitro. Twenty-five incisors from four beagles were used. After the teeth were extracted, the periodontal ligament and cementum were removed from coronal part of the roots and the roots were planed. The periodontal ligament of the apical part was retained. Fourteen teeth of the experimental group were transplanted following culture for 6 weeks. Eleven teeth of the control group were similarly prepared and immediately transplanted without tissue culture. Four weeks after transplantation, the specimens were prepared for histological analysis. Downgrowth of junctional epithelium on the root of experimental group was significantly less than control. Most of the root planed surfaces of experimental group were covered with periodontal ligament fibers oriented parallel or inclined to the root surfaces and limited new cementum formation was observed near the apical end of the planed root. There was no significant difference between groups in observations on the root surface with remaining periodontal ligament. From the above results, it was concluded that periodontal tissue culture of teeth with root planed surface and remaining periodontal ligament could reduce the extent of epithelium downgrowth and increase connective tissue adhesion on the root planed surface, as well as minimize damage to remaining periodontal ligament, after transplantation of teeth.

Attachment Formation After Transplantation of Teeth Cultured With Enamel Matrix Derivative in Dogs

BACKGROUND Implantation of cultured cells may be applied for periodontal regeneration in the future. However, a donor is essential in each case and tooth extraction is required to obtain the periodontal ligament-derived cell. We developed a novel regenerative technique combining tissue culture and transplantation of teeth. The purpose of this study is to evaluate the effect of enamel matrix derivative (EMD) on periodontal healing using this technique in dogs. METHODS A total of 32 incisors from seven beagle dogs were used. The periodontal ligament and cementum 5 mm from the coronal part of the roots were removed, whereas those in the apical part were preserved. Teeth were transplanted after the following treatments: 1) culture with application of EMD to the root surface for 6 weeks (n = 11); 2) culture without application of EMD for 6 weeks (n = 11); and 3) immediately transplanted without culture as control (n = 10). Eight weeks after transplantation, periodontal healing was analyzed. RESULTS The downgrowth of junctional epithelium on the roots of the EMD and culture groups was significantly smaller than that in the control group (P <0.01). Most of the root-planed surfaces in the EMD group were covered with new cementum (72.2% ± 8.6%). This was significantly greater than that in the culture (29.1% ± 22.9%) and control groups (0.3% ± 1.1%). CONCLUSIONS Transplantation of tissue-cultured teeth decreased epithelial downgrowth and increased connective tissue attachment on the root-planed surface. Furthermore, EMD could remarkably increase the new connective tissue attachment in this periodontal regenerative technique.

A Novel Regenerative Technique Combining Bone Morphogenetic Protein‐2 With Fibroblast Growth Factor‐2 for Circumferential Defects in Dog Incisors

BACKGROUND Periodontal regeneration of incisors is necessary for esthetic recovery. A novel regenerative method combining bone morphogenetic protein (BMP)-2 and fibroblast growth factor (FGF)-2 was developed. The purpose of this study is to evaluate periodontal healing, including root coverage, in circumferential defects of incisors. METHODS Fifty incisors in five beagles were used. After circumferential defects were surgically created, each group, consisting of ten recipient sites, received: 1) a double layer with FGF-2 (2 μg)/collagen as inner layer and BMP-2 (4 μg)/collagen as outer layer (FB-DL group); 2) collagen impregnated with both FGF-2 (2 μg) and BMP-2 (4 μg) (FB-M group); 3) BMP-2 (4 μg)/collagen (B group); 4) FGF-2 (4 μg)/collagen (F group); or 5) collagen (C group). Dogs were sacrificed 8 weeks post-surgery, and healing was evaluated histologically. RESULTS The three groups treated with BMP-2 showed enhanced new bone formation compared with control and F groups (P < 0.05). Furthermore, connective tissue attachment with cementum regeneration in the FB-DL group was significantly greater than in FB-M and B groups (P <0.05). Ankylosis in the FB-DL group was significantly less than in FB-M and B groups (P <0.05). Gingival recession was inhibited significantly better in FB-DL and FB-M groups compared with control and B groups. CONCLUSION These data support development of a double-layer method combining BMP-2 and FGF-2 as a therapeutic approach to periodontal regeneration at incisors with horizontal circumferential defects.

Healing Following Implantation of Root with Remaining Periodontal Ligament Cultured In vitro

Background: Intentional replantation is extraction of a tooth to do extraoral root canal therapy, curettage of apical lesion when present, and its replacement in its socket. The most common causes of failure in intentionally replanted teeth are external resorption and ankylosis caused by periodontal ligament damage. We hypothesized that if proliferative cells derived from healthy periodontal ligament could cover a damaged site, the success rate of implantation and replantation would increase and thus widen its application. The purpose of this study was to histologically evaluate the influence of tissue culture on healing following implantation of root with remaining periodontal ligament cultured in vitro into a mandibular bone cavity. Methods: Twenty incisors of 5 beagles were extracted and forty trimmed roots (4.0×3.0 mm) were made using a bur. Periodontal ligament on the root surface of thirty trimmed roots was retained and remaining ten trimmed roots were removed periodontal ligament on the root surface. Thirty trimmed roots with remaining periodontal ligament were divided into three groups according to each culture sequence, namely 0 week (not cultured), 2 and 4 weeks. Following the culture period, the roots were implanted into bone cavities created in the mandible. Four weeks postsurgery, the specimens were prepared for histological analysis. Results: In the 0w group, ankylosis was observed in three of 10 cases. However, ankylosis did not occur at all in the 2w and 4w groups. However, there were no significant differences in any parameter (normal periodontum, ankylosis, surface resorption, inflammatory resorption) among the three groups. Conclusion: The mechanical injury that occurred during extraction of the teeth could be responsible for the ankylosis. If the entire root surface is covered with cultured periodontal ligament-derived cells and that could prevent ankylosis, the success rate of intentional replantation and implantation might increase.

The Effect of EMD Application for Intentional Replantation of Periodontally Involved Teeth in Dogs

Background: Intentional replantation of periodontally involved teeth has been reported to result in unfavorable healing like root resorption and ankylosis. However, many recent clinical reports using enamel matrix derivative (EMD) showed a good outcome based on clinical and radiographic examination. However, histological findings are lacking. The purpose of this study was to evaluate healing after intentional replantation with EMD in a periodontally involved teeth model. Methods: A total of 20 incisors from seven beagle dogs were used. The periodontal ligament and cementum 5 mm from the coronal part of the roots were removed, whereas those in the apical part were preserved. Ten teeth of the experimental group were transplanted following application of EMD to the root surface. Ten teeth from the control group were transplanted without application. Eight weeks after transplantation, periodontal healing was analyzed. Results: Surface root resorption in the experimental group was significantly greater than in the control. New cementum formation was observed near the apical end of the planed root of the EMD group. Replacement resorption of the EMD group was significantly less than in the control. There was no significant difference in inflammatory resorption between groups. Conclusion: The combination use of EMD in intentional replantation resulted in new cementum formation on the root planed surface and inhibited root resorption and ankylosis. However, root resorption occurred at the coronal part in areas where the surface was root planed.

Effect of Tunnel Structure of β-TCP on Periodontal Repair in Class III Furcation Defects in Dogs

Background: The pore characteristics of bone graft materials play an important role in bone regeneration. Previous studies have reported that a pore size of 100 ~ 400 μm effectively induces vascular invasion and cell population within the materials. Many graft materials used recently have macropore (200 ~ 600 μm) or micropore (0.1 ~ 1 μm) structures. We devised a bone material with a tunnel pipe structure and pore size of 300 μm. The present study evaluated periodontal healing following implantation of this new bone graft material in furcation class III defects. Methods: Thirty mandibular premolar teeth of five beagles were used. After class III furcation defects were surgically created, each furcation was randomly treated with: 1) β-TCP with a tunnel pipe structure (tunnel group) (n=10); 2) Granular β-TCP (granular group) (n=10); and 3) No implant material (control group) (n=10). The dogs were sacrificed 8 weeks post-surgery and healing was evaluated histologically. Results: In the tunnel group, down growth of junctional epithelium was significantly less than that in the other two groups (P <0.01) and bone formation and blood capillary invasion were observed in the inner part of pores of the implanted material in the furcation. However, little bone formation was observed between the granules in the granular group. Conclusion: β- TCP with a tunnel pipe structure and pore size of 300 μm promotes bone regeneration and new cementum formation in class III furcation defects.