Effect of proliferating tissue on transplanted teeth in dogs.

OBJECTIVE: The objective of this study was to investigate the effect of transplanted proliferating tissue on the regeneration of periodontal ligaments (PDL) in tooth transplantation. STUDY DESIGN: Two weeks after removing the alveolar bone, proliferating tissues were excised and examined for expression of basic fibroblast growth factor (bFGF) and alkaline phosphatase (ALP) using a LightCycler. Next, the teeth to be transplanted (first premolars) were extracted and PDLs were removed by scaling. After that, the first premolar teeth and proliferating tissues for the experimental group were transplanted into bone cavities created at the sites of the third and fourth premolars, while the control sites received teeth only. Finally, 1, 2, and 4 weeks later, the animals were sacrificed and specimens were collected and processed for histopathologic examination. RESULTS: bFGF and ALPmRNA showed a significant increase in the transplanted proliferating tissue. Transplantation of the proliferating tissues positively affected the formation of new cementum and PDL. Moreover, application of the transplanted proliferating tissues decreased the occurrence and extent of ankylosis and root resorption at the root surface. CONCLUSION: These results indicate that transplanted proliferating tissue may promote the regeneration of periodontal tissue and prevent ankylosis and root resorption following the transplantation of teeth.     

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.     

Resorption of the mouse incisor after the application of cold to the periodontal attachment apparatus

Summary In order to study in detail the processes leading to the resorption and ankylosis of teeth after trauma, the effects of cold application on the periodontal tissues were studied in the mouse. Liquid nitrogen was applied locally to the outer surface of the lower jaw which resulted in a freezing of the incisor and its surrounding tissues. The healing processes in the damaged periodontal ligament and the accompanying phenomena of ankylosis and dental root resorption were investigated histologically at both the light and electron microscopic levels. As a result of cold application, the cells in the periodontal ligament were killed. After a few days, the ligament started to be repopulated with cells like fibroblasts and macrophages. From 3 days on, mineral crystallites were deposited along the cementum covering the lingual, mesial, and lateral surfaces of the incisor, finally resulting in a 4–6 μm thick layer. During the period of 7–12 days following cold application, this layer of mineralized material started to be phagocytosed and degraded, presumably by mononuclear cells. Finally, extensive root resorption and some ankylosis between the tooth and the laveolar bone were observed. In the resorbed areas, cells were seen which could not be distinguished from osteoclasts. In some instances, their ruffled border was in close apposition with each of the three mineralized tissues—dentin, cementum, and alveolar bone. It is hypothesized that the deposition and subsequent phagocytosis of mineralized material along the root surface may be an important factor in the initiation of dental root resorption.     

Radiographic evaluation of periapical status and prevalence of endodontic treatment in an adult Japanese population.

OBJECTIVES: To determine the prevalence of periapical radiolucencies and endodontic treatment in an adult Japanese population. STUDY DESIGN: Periapical status and length of root fillings of 672 adult patients attending Okayama University Hospital of Dentistry were evaluated using full mouth intraoral radiographs. RESULTS: Overall, 87% of the subjects had root-filled teeth, and 70% exhibited an apical radiolucency. Of the 16,232 teeth examined, 21% had been root-filled, and, of these, 40% exhibited an apical radiolucency. Root-filled teeth that were overfilled or that were mandibular incisors had the highest prevalence of apical radiolucencies. CONCLUSIONS: The prevalence of root-filled teeth appears higher in this Japanese population than in Europe or America; however, the ratio of teeth with an apical radiolucency to root-filled teeth was within the range of that reported for other countries. Overfilled teeth and mandibular incisors are most likely to exhibit apical radiolucencies.     

Histomorphometric description of allograft bone remodeling and union in a canine segmental femoral defect model: a comparison of rhBMP-2, cancellous bone graft, and absorbable collagen sponge.

The purpose of this study was to determine the effect of recombinant human bone morphogenetic protein type 2 (rhBMP-2) on the histomorphometry of femoral allograft-host bone union and allograft remodeling. A 6 cm mid-diaphyseal femoral defect was created and filled with an allograft stabilized with an interlocking nail in 21 dogs. Dogs were randomly divided into three equal groups and the allograft-host bone junctions and the mid-diaphyses of the allografts were treated with either an absorbable collagen sponge (ACS) loaded with rhBMP-2 (BMP group), an autogenous cancellous bone graft (CBG group), or ACS loaded with buffer solution (ACS group). All dogs received daily tetracycline until sacrifice at 24 weeks to label new bone formation. Histomorphometric analyses on sections of proximal and distal allograft-host bone junctions and the mid-diaphyseal portion of allografts were performed using fluorescent and regular light microscopy. Analyses of the host bone and junctions between allograft and host bone revealed significantly greater new bone formation and larger osteon radii in the BMP group compared to CBG and ACS groups and contralateral intact bone. Porosity in CBG and ACS groups was significantly higher than in the BMP group, which had similar values to intact bone. In transverse sections of allografts, the largest pore diameters were present in the CBG group. Based on all parameters measured, significantly higher bone turnover occurred in the outer cortical area of the allograft in all groups as compared to the inner cortical and mid-cortical areas. New bone formation and osteon radius/osteon width in allografts were similar for all three groups. Higher porosity and larger pore diameters in the CBG and ACS groups suggested higher bone resorption versus formation in these groups compared to the BMP group. The results of this study reveal more balanced allograft bone resorption and bone formation in the BMP group, with greater resorptive activity in the CBG and ACS groups. However, neither rhBMP-2 nor autogenous bone graft increased allograft incorporation when compared to the negative control (ACS group).     

Evaluation of the prognosis and causes of failure in 182 cases of autogenous tooth transplantation.

OBJECTIVES: Autotransplantation is a viable option for treating missing teeth when a donor tooth is available. The aim of this study was to evaluate the prognosis in addition to the causes of failure in 182 autotransplanted teeth. STUDY DESIGN: A total of 182 cases of autotransplantation were analyzed. All the transplants were performed according to a computer-aided rapid prototyping technique with an average extraoral time of 7.58 minutes. These cases were followed for 2 to 60 months after surgery. The prognosis was divided into 4 groups, complete healing, incomplete healing, uncertain healing, and failure. The initial stability, root resorption, and ankylosis were also analyzed. RESULTS: Most transplanted teeth showed complete healing between postoperative 2 months and 8 months. The transplanted teeth with a good initial stability showed better initial healing than those with a poor initial stability. The average extraoral time was 7.58 min (range: immediately after extraction up to 25 min). There was no relationship (P > .05) between the extraoral time and either root resorption (4 cases, 2.4%) or ankylosis (18 cases, 10.7%) within this experimental time period. Nine cases (4.5%) failed. CONCLUSION: This study showed a 4.5% failure rate during the short to intermediate observation period. Autotransplantation is a very useful method for replacing missing teeth, provided that the extraoral time and other factors are well controlled.     

上颌唇侧倒置埋伏中切牙患者正畸矫治后埋伏牙发生及牙根吸收的影响因素分析

评估上颌唇侧倒置埋伏中切牙患者正畸矫治后埋伏牙发生及牙根吸收的影响因素。方法 收集2019年3月-2021年3月于溧阳市人民医院就诊的1021例上颌唇侧倒置埋伏中切牙患者临床资料进行回 顾性调查，查阅锥形束CT及X线图像。其中113例发现埋伏牙，按照是否出现牙根吸收分为牙根吸收组 （51例）和牙根未吸收组（62例）。调取资料，包括性别、初诊年龄、平均体质量指数、埋伏牙位置、 近远中分区、是否拔牙、正畸治疗时间、埋伏牙发生个数等。统计上述指标情况，分析正畸矫治后埋伏 牙牙根吸收的单因素和多因素。结果 1021例患者中埋伏牙113例（11.07%）；牙根吸收组平均年龄、2~4 区占比均低于牙根未吸收组（P ＜0.05）；牙根吸收组拔牙率、正畸治疗时间＞2年占比均高于牙根未吸 收组（P ＜0.05）；两组性别、平均体质量指数、埋伏牙位置、病变位置、埋伏牙发生个数比较，差异无 统计学意义（P ＞0.05）；Logistic结果显示，高龄、近远中分区（0~1区）、拔牙、正畸治疗时间＞2年均为 正畸矫治后埋伏牙牙根吸收的高危因素（P ＜0.05）。结论 上颌唇侧倒置埋伏中切牙正畸矫治后埋伏牙牙 根吸收与年龄、近远中分区、拔牙、正畸治疗时间有关，对于高危因素患者，临床应给予重视，采用早期 干预措施，减少损伤。     

Use of MTA for orthograde obturation of nonvital teeth with open apices: report of two cases.

The purpose of this report is to present the treatment of 2 immature necrotic permanent incisors with the use of apical plugs of mineral trioxide aggregate (MTA) for apexification. With this technique, MTA mixture is used to create an artificial stop against which to condense gutta-percha in pulpless teeth with open apices. The report of these cases confirms that MTA acts an apical barrier and can be considered as an effective material to support regeneration of apical tissue in immature necrotic teeth. The treated teeth were asymptomatic, and radiographic follow-ups showed healing of periradicular tissues and new hard tissue formation in the apical area of the affected teeth.     

Time of endodontic treatment in autogenic transplants of mature teeth: histological study in dogs.

OBJECTIVE: Root canal therapy is often recommended after mature tooth transplantation. The aim of this work was to histologically evaluate, in dogs, the best time for root canal treatment in autogenic transplants of teeth with complete root formation. STUDY DESIGN: Mandibular lateral incisors of 8 dogs were extracted and transplanted to the homologous alveolus, endodontically treated after 15 (Group I) or 40 (Group II) days, and processed for routine histological evaluation. Tissue responses on the root surface were evaluated by light microscopy and classified as normal periodontium, active inflammatory root resorption, favorable healing, and unfavorable healing. RESULTS: The mean of normal periodontal tissue was in 88.6% in Group I and 79.4% in Group II. There were no significant statistical differences between the groups in all analyzed parameters. CONCLUSION: The results indicated that endodontic therapy can be postponed for 40 days postoperatively when the tooth stability is higher.     

微小种植体支抗压低前牙改善露龈笑的临床研究

目的：评价利用微小种植体作为支抗压低前牙改善露龈笑的临床效果。方法：选取我科室9例（男5例,女4例）前牙过长,开唇露齿露龈笑的深覆病例,年龄18.6～28.3岁,平均24.7岁。9例患者前牙区存在II度或III度深覆,5例病例伴有不同程度的牙列前突。9例患者在佩戴固定戴矫治器后在上、下颌前牙区相应部位植入微小种植体,治疗前后拍摄全口曲面断层片进行测量对比,观察切牙的变化和改善露龈笑的情况。结果：9例患者治疗前后上下颌前牙均有不同程度的压低,上颌前牙平均压低3.8mm,下颌切牙平均压低3.0mm,深覆得到有效的治疗,同时露龈笑有一定程度的改善。其中2例患者出现一定程度的牙根吸收。结论：利用微小种植体支抗能有效地治疗前牙过长开唇露齿,达到真正压低前牙解除深覆的效果。     

Management of cervical root fracture using orthodontic extrusion and crown reattachment: a case report.

Root fractures involve damage to pulp, cementum, dentin, and periodontal ligaments. These injuries affect 0.5% to 7% of permanent teeth. Cervical root fractures are less frequently seen and have a worse prognosis compared with the fractures in the apical or middle third of the root. This case report describes the treatment of a cervical root fracture in a maxillary central incisor. After removal of the coronal fragment, the root was filled temporarily with calcium hydroxide and orthodontic extrusion was initiated. The remaining root portion was elevated above the epithelial attachment and a successful coronal restoration was made using the natural crown of the traumatized tooth.     

RhBMP-7 improves survival and eruption in a growing tooth avulsion trauma model

Long-term loss of avulsed and replanted teeth is a frequent clinical problem. Bone morphogenetic protein-7 (BMP 7) induces cementogenesis in periodontitis-associated periodontal ligament (PDL) defects. This study's aim was to assess the utility of rhBMP 7 in a tooth avulsion trauma model in growing individuals. Immature primary incisors of 12 minipigs were extracted. PDL and cementum were removed either partially (group 1: 4 mm2 [n=28 teeth]; group 2: 16 mm2 [n=26 teeth]) or totally (group 3 [n=26 teeth]). 500 microg rhBMP 7/g collagen matrix was applied to the teeth from one side while the corresponding teeth on the contralateral side served as controls (split mouth model). After an experimental period of 4 months, microradiography, fluorescence and light microscopy of nondecalcified sections were performed. All teeth of group 1 survived and all teeth of group 3 were lost, whether rhBMP-7 was applied or not. In group 2, nine out of ten teeth survived when rhBMP-7 was applied and four out of ten teeth were lost when rhBMP-7 was not applied. In the presence of rhBMP-7, eruption of teeth in group 2 was significantly improved (difference [median]: 5 mm, P<0.05, n=6). Even though there was a tendency towards increased deposition rates of cementum under rhBMP-7, this difference was not significant (Wilcoxon: P>0.05, ANOVA: P=0.002; n=6/group). In conclusion, rhBMP-7 improved survival rates and eruption of replanted teeth in growing individuals. No adverse effects were seen. Based on the present results, future clinical trials appear to be warranted.     

Recombinant human bone morphogenetic protein-2 enhances osteotomy healing in glucocorticoid-treated rabbits.

The objectives of this study were to evaluate the effect of chronic prednisolone treatment on osteotomy healing in rabbits and to determine whether recombinant human bone morphogenetic protein-2 (rhBMP-2) would enhance healing in the presence of chronic glucocorticoid therapy. Forty-nine skeletally mature, male rabbits were injected with either prednisolone (n = 26; 0.35 mg/kg per day, three times a week) or saline (n = 23). After a 6-week pretreatment period, bilateral ulnar osteotomies were created surgically. One osteotomy was treated with rhBMP-2 (0.2 mg/ml of rhBMP-2, 40 microg of rhBMP-2 total) delivered on an absorbable collage sponge (ACS), whereas the contralateral osteotomy remained untreated. Prednisolone or saline treatment was continued until the rabbits were killed either 6 weeks or 8 weeks after creation of the osteotomy. Osteotomy healing was evaluated by radiography, peripheral quantitative computed tomography (pQCT), torsional biomechanics, and undecalcified histology. Because we observed similar responses to both prednisolone and rhBMP-2/ACS treatment in the 6-week and 8-week cohorts, the results from these time points were combined. Serum osteocalcin and vertebral trabecular bone density were lower in the prednisolone-treated rabbits. Prednisolone treatment dramatically inhibited osteotomy healing. In the untreated ulnas, callus area and torsional strength were 25% and 55% less, respectively, in the prednisolone-treated rabbits than in the saline group (p < 0.001 for both). rhBMP-2/ACS enhanced healing in both the prednisolone- and the saline-treated groups, although the effect was larger in the prednisolone-treated rabbits. In the prednisolone-treated rabbits, callus area and torsional strength were 40% and 165% greater (p < 0.001 for both), respectively, in osteotomies treated with rhBMP-2/ACS compared with the contralateral, untreated osteotomies. Histological evaluation confirmed that osteotomy healing was inhibited by prednisolone and accelerated by rhBMP-2/ACS. In summary, a single application of rhBMP-2/ACS counteracted the inhibition of osteotomy healing caused by prednisolone exposure. These results suggest that rhBMP-2/ACS may be a useful treatment for enhancing fracture healing in patients who are undergoing chronic glucocorticoid therapy.     

Bone loss and teeth

Loss of teeth results in irreversible alveolar bone resorption, and untreated dental disease causes alveolar bone lysis that ultimately leads to loss of teeth. In addition to anchoring the teeth in the alveolar ridge, the maxillary and mandibular bone allows dental restoration procedures, such as construction of root-supported implants, fixed dentures, or removable dentures. However, the functional and cosmetic results depend on the quantity and quality of the maxillary or mandibular bone, which can be affected by many normal and abnormal processes. The alveoli are particularly fragile and labile. Changes in alveolar bone vary considerably across individuals and depend directly on local factors. Many studies have investigated associations between alveolar bone status and bone mass at other skeletal sites. These studies focused chiefly on the course of parodontal disease, alveolar ridge resorption after tooth extraction, and density differences across various mandibular sites. They produced conflicting results, probably because of differences in measurement methods. Measurement sites and methods should be standardized to ensure that reliable and comparable data are obtained. To date, there are few reliable methods for obtaining quantitative measurements of bone mineral content in maxillary and mandibular bone.     

Effect of rotary or manual instrumentation, with or without a calcium hydroxide/1% chlorhexidine intracanal dressing, on the healing of experimentally induced chronic periapical lesions.

OBJECTIVE: To evaluate the healing of experimentally induced chronic periapical lesions in dogs at 30, 75, and 120 days after root canal instrumentation with rotary NiTi files or manual K-files, with or without a calcium hydroxide/1% chlorhexidine paste intracanal dressing. STUDY DESIGN: The second, third, and fourth mandibular premolars and the second and third maxillary premolars of 5 dogs (12 to 18 months of age, weighing 8 to 15 kg) were selected for treatment (a total of 82 root canals). After pulp removal, the root canals were left exposed to the oral cavity for 7 days to allow microbial contamination, after which the root canals were sealed with ZOE cement until periapical lesions were confirmed with radiography. Group I and II teeth were instrumented with manual K-files using the crown-down technique. In group III and IV teeth, NiTi rotary files were used. The apical delta was perforated by using #20 to #30 K-files at the length of the tooth, thus creating a standardized apical opening. The apical stop was enlarged to size 70, with 2.5% sodium hypochlorite irrigation at each file change. Teeth in groups II and IV were dressed with calcium hydroxide (Ca(OH) 2 )/1% chlorhexidine (CHX) paste for 15 days before root filling. Group I and III teeth did not receive an intracanal dressing. The access openings of the teeth were permanently restored with silver amalgam condensed on a glass ionomer cement base. Pairs of standardized periapical radiographs were taken at the beginning of the treatment (0 days) and at 30, 75, and 120 days after filling. RESULTS: There was no significant difference in the rate of radiographic healing of the periapical lesions between manual and rotary instrumentation. Radiographs taken at 120 days showed that the treatment with Ca(OH) 2 /1% CHX paste resulted in a significant reduction in mean size of the periapical lesions in comparison to single-session treatment. These findings were also true for histologic observations. CONCLUSION: The findings support the hypothesis that, regardless of the instrumentation technique (manual or rotary), the use of an intracanal dressing is important in the endodontic treatment of dog's teeth with experimentally induced chronic periapical lesions.     

Comparing ectopic bone growth induced by rhBMP-2 on an absorbable collagen sponge in rat and rabbit models.

Recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) is currently employed as an autograft replacement for spinal fusion. The morphogen is incorporated onto its carrier, an absorbable collagen sponge (ACS), in the operating room. Although the effectiveness of the rhBMP-2/ACS implant in stimulating bone formation in human subjects has now been well established, further investigations of its use are necessary to deepen our understanding of its performance. The objective of the present study was to determine whether fluid released from the rhBMP-2/ACS implant could induce bone growth in tissue sites away from the implant site. We first measured the amount of protein in the fluid released from the rhBMP-2-soaked ACS during intraoperative handling. Variables included soak time and degree of compression. In the compression group that most closely approximated intraoperative conditions, more than 95% of the rhBMP-2 protein was retained by the ACS following a 15-min. soak time. This in vitro study was followed by an in vivo ectopic implant experiment using rat and rabbit models. The animal investigation compared the amount of bone induced by rhBMP-2 solution alone versus the de novo bone formation induced by rhBMP-2/ACS implants with varying concentrations of rhBMP-2. No ossicles were found at the sites where rhBMP-2 solution was injected in either animal species. Twenty-two of the 24 subcutaneous sites in the rats implanted with the rhBMP-2/ACS constructs displayed the presence of the typical 4- and 12-week ossicle. There were no noticeable differences in the size and shape of the ossicles after 4 and 12 weeks. There was a greater percentage of implant sites without ossicles in the rabbits, compared to the rats.     

Tooth Germ‐Like Construct Transplantation for Whole‐Tooth Regeneration: An In Vivo Study in the Miniature Pig

The purpose of this study was to demonstrate the feasibility of whole‐tooth regeneration using a tooth germ‐like construct. Dental pulp from upper incisors, canines, premolars, and molars were extracted from sexually mature miniature pigs. Pulp tissues were cultured and expanded in vitro to obtain dental pulp stem cells (DPSCs), and cells were differentiated into odontoblasts and osteoblasts. Epithelial cells were isolated from gingival epithelium. The epithelial cells, odontoblasts, and osteoblasts were seeded onto the surface, upper, and lower layers, respectively, of a bioactive scaffold. The lower first and second molar tooth germs were removed bilaterally and the layered cell/scaffold constructs were transplanted to the mandibular alveolar socket of a pig. At 13.5 months postimplantation, seven of eight pigs developed two teeth with crown, root, and pulp structures. Enamel‐like tissues, dentin, cementum, odontoblasts, and periodontal tissues were found upon histological inspection. The regenerated tooth expressed dentin matrix protein‐1 and osteopontin. All pigs had regenerated molar teeth regardless of the original tooth used to procure the DPSCs. Pigs that had tooth germs removed or who received empty scaffolds did not develop teeth. Although periodontal ligaments were generated, ankylosis was found in some animals. This study revealed that implantation of a tooth germ‐like structure generated a complete tooth with a high success rate. The implant location may influence the morphology of the regenerated tooth.     

Administration of the Bisphosphonate Zoledronic Acid During Tooth Development Inhibits Tooth Eruption and Formation and Induces Dental Abnormalities in Rats

Bisphosphonates (BPs) are potent inhibitors of osteoclastic bone resorption and widely used for the treatment of osteoporosis and metastatic bone diseases. Recently, BPs have also been shown to benefit children with primary and secondary osteoporosis, including osteogenesis imperfecta; however, their long-term safety has not been established yet. Clinical and experimental studies have demonstrated that BPs delay or inhibit tooth eruption. The failure of tooth eruption causes several dental abnormalities. In this study, to determine the effects of BPs on tooth formation, the BP zoledronic acid (ZOL) was injected into 7- and 14-day-old rats, and the development of the mandibular teeth was examined. X-ray analysis demonstrated that ZOL inhibited the eruption of both incisors and molars and their formation, especially in the molar roots. Histological examination showed that, in ZOL-treated animals, alveolar bone remained unresorbed around tooth crowns, which injured ameloblasts and enamel matrix, leading to defects of the enamel. Furthermore, haphazard proliferation of odontogenic epithelium and mesenchyme associated with primitive tooth structures, which resembles human odontomas, was induced at the basal end of incisors but not around the molars. Tooth ankylosis to alveolar bone was occasionally observed in molars. These results suggest that administration of BPs during tooth development has the potential to inhibit tooth eruption and formation and to induce several types of dental abnormalities, which may be attributed to the altered osteoclastic activities.     

Periodontal tissue healing following flap surgery using an Er:YAG laser in dogs

BACKGROUND AND OBJECTIVES: The purpose of this study was to compare periodontal tissue healing following flap surgery using an Er:YAG laser with that of conventional surgery. STUDY DESIGN/MATERIALS AND METHODS: Bilateral premolars with experimentally induced periodontitis in six dogs were treated by periodontal flap surgery. Degranulation and root debridement in the furcation were performed using an Er:YAG laser or curet. At 3 months postsurgery, animals were sacrificed and decalcified specimens were prepared for histological and histometric analysis. RESULTS: Degranulation and root debridement were effectively performed with an Er:YAG laser without major thermal damage and significantly faster than with a curet. Histologically, the amount of newly formed bone was significantly greater in the laser group than in the curet group, although both groups showed similar amounts of cementum formation and connective tissue attachment. CONCLUSIONS: The Er:YAG laser irradiation can be safely and effectively utilized in periodontal flap surgery, and has the potential to promote new bone formation.     

Bone consolidation is enhanced by rhBMP-2 in a rabbit model of distraction osteogenesis.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a differentiation factor which has been shown to induce bone formation and heal bony defects in a variety of animal models. A possible application of rhBMP-2 is to accelerate bone regeneration during distraction osteogenesis. which clinically is a long procedure, often involving significant complications. In this study we tested the ability of rhBMP-2 to accelerate the consolidation phase of distraction osteogenesis in a rabbit model of leg lengthening. Tibiae were lengthened 2 cm over a period of ten days. rhBMP-2 was administered at the end of the lengthening phase. Two modes of rhBMP-2 application were tested: surgical implantation of rhBMP-2/ACS (absorbable collagen sponge) into the regenerate (50 microl of 1.5 mg/ml rhBMP-2, total dose = 75 microg rhBMP-2), and percutaneous injection of rhBMP-2/buffer (0.1 ml of 0.75 mg/ml rhBMP-2. total dose = 75 microg rhBMP-2) into three sites within the regenerate. Also, there were three groups of control animals: (1) no surgical intervention, (2) surgical implantation of buffer/ACS and (3) percutaneous injection of buffer. Rabbits were sacrificed at 5, 14 and 28 days after the interventions. Radiographic evaluation indicated a significant increase in bony union of the distraction regenerate in the rhBMP-2 treated groups compared with the untreated groups at 5 and 14 days. At 28 days, formation of a cortex and reestablishment of the medullary canal was evident only in the rhBMP-2 treated groups. The bone mineral content (BMC) of the regenerate was significantly higher in the rhBMP-2 treated groups at 5 and 14 days. However, at 28 days, BMC of the regenerate was similar in all groups. The average volumetric density of the regenerate was significantly higher in the rhBMP-2 injection group at day 14. In Summary, both injection of rhBMP-2/buffer and implantation of rhBMP-2/ACS enhanced the consolidation stage of distraction osteogenesis in this rabbit model.