骨形成蛋白促进牙周组织再生的动物实验研究

目的将骨形成蛋白（ｂｏｎｅｍｏｒｐｈｏｇｅｎｅｔｉｃｐｒｏｔｅｉｎ，ＢＭＰ）联合应用于牙周引导组织再生（ｇｕｉｄｅｄｔｉｓｓｕｅｒｅｇｅｎｅｒａｔｉｏｎ，ＧＴＲ）技术中，观察和比较其对牙周组织再生修复的影响和意义。方法制备狗下颌后牙区人工骨缺损，于清创后分组置入引导膜材料和ＢＭＰ，以常规翻瓣术为对照；分不同时期取材做组织学观察和评价。结果实验组较对照组新生组织量多，而以复合ＢＭＰ组效果最为显著；膜材料在早期有一定抑制结合上皮根向迁移的作用。结论利用外源性ＢＭＰ的主动生物诱导活性，可望应用于临床促进牙周硬组织成分的新生修复。     

Ultrastructure of early mineral deposition during hyaline layer formation in rat molars

There is no consensus on whether the first mineralized layer, the hyaline layer, that is juxtaposed to root dentine is a variety of dentine or cementum or even a tissue of epithelial origin. Some suggest that there is no intermediate tissue between the acellular extrinsic fibre cementum (AEFC) and the root dentine. Here, to study hyaline layer formation and mineralization we examined by transmission electron microscopy the early stages of root development in upper molars from 10 to 13 day old Wistar rats. In addition to conventionally processed material, undemineralized and unstained sections were examined, which showed the deposition of fine mineral crystals in contact with the mineralized surface of root dentine. Early mineralization of the hyaline layer occurred in the region of the inner basement membrane, which persisted between the inner cellular layer of Hertwig's epithelial root sheath and the outer mineralized root dentine. When the root sheath began its fragment, collagen fibrils from the developing periodontal ligament began to insert into the mineralising hyaline layer, which was 0.5-0.8 micron wide. As the fragmentation of the root sheath HERS increased, more collagen fibrils appeared intermingled with the mineralising hyaline layer. In more advanced stages, when the hyaline layer had become fully mineralized and the formation of the AEFC began, the hyaline layer could no longer be identified. Thus, the hyaline layer is clearly discernible at early stages of periodontal development. Subsequently, it is masked by intermingling of cementum and dentine and therefore it is not possible to detect it in the formed roots of rat molars.     

Root cementum appearance in healthy monkeys and periodontitis-prone patients after different etching modalities

Abstract The purpose of the present study was to compare cementum surfaces after etching at neutral or low pH in both healthy monkey teeth and periodontitis-affected human teeth. 16 monkey teeth and 16 human periodontitis-affected teeth were used. Etching with phosphoric and citric acids as well as EDTA was performed on the following surfaces: healthy monkey cementum, human cementum surfaces coronal and apical to the level of periodontal breakdown as well as exposed human dentin surfaces. Results indicate a profoundly higher capacity of EDTA to selectively expose collagen fibers in both healthy cementum surfaces and periodontitis-affected dentin surfaces compared to agents operating at low pH which seemed to erode the surfaces to varying degrees. Variable results were seen on cementum surfaces which had been exposed to the environment of the periodontal pocket or the oral cavity. In view of this, it would seem preferable to mechanically remove the superficial layer of “diseased” cementum prior to the etching procedure. In conventional periodontal surgery, etching may be of limited value. However, in regenerative procedures, exposure of an intact collagenous matrix provides a matrix for retention of implants of biologically active substances such as growth factors, in addition to serving as a biocompatible surface for periodontal ligament cell colonization.     

Afibrillar dental cementum in the rat and hamster

Afibrillar cementum "spurs" have been observed as a direct coronal extension of fibrillar root cementum near the cemento-enamel junction of rat molars. It was also present as a localized deposit over the dentin surface of a hamster mandibular molar near the bifurcation. Adjacent cementicles in the periodontal ligament consisted of an intimate mixture of fibrillar and afibrillar cementum. It is suggested that afibrillar cementum may be due to failure of the collagen moiety to aggregate into fibrils or to a marked relative increase in the glycoproteoglycan content of the organic matrix.     

Cementum formation around a titanium implant: a case report

Animal studies have shown that a periodontal ligament may be produced around a titanium implant when it is in contact with fractured and retained roots. Formation of cementum and attachment connective tissue around titanium implants confirms that cementum progenitor cells are located in the periodontal ligament, since cementum and periodontal ligament are present at the implant-root interface, whereas the remainder of the implant, which is not in contact with the root, shows osseointegration. The aim was to evaluate histologically the characteristics of the tissue present between a titanium implant and a retained root, which were subsequently extracted as a result of peri-implantitis. The histologic examination revealed a continuous layer of cementum and numerous cementocytes on the implant surface. No blood vessel or collagen fibers were detected in the periodontal space. In contrast to experimental studies carried out on animals, the lack of connective tissue fibers and the presence of hypercementosis in this specimen could have been caused by the inflammatory process. Furthermore, the extrusive movement of the root might explain the presence of cementum hypertrophy. Further studies are required to establish whether the neoformation of cementum and collagen fibers on an implant in the presence of root residues occurs only in animal models or whether it may also occur in humans.     

Application of periodontal ligament cell sheet for periodontal regeneration: a pilot study in beagle dogs

OBJECTIVE: The ultimate goal of periodontal treatment is to regenerate the damaged periodontal support. Although periodontal ligament (PDL) cells are essential for periodontal regeneration, few studies have reported the transplantation of periodontal ligament cells to periodontal defects. We developed a new method to apply periodontal ligament cells as a sheet to the defect. The aim of this study was to investigate the periodontal healing after application of the periodontal ligament cell sheet in beagle dogs. METHODS: Autologous periodontal ligament cells were obtained from extracted premolars of each beagle dog. Periodontal ligament cell sheets were fabricated using a temperature-responsive cell culture dish. Dehiscence defects were surgically created on the buccal surface of the mesial roots of bilateral mandibular first molars of each dog. In the experimental group (five defects), periodontal ligament cell sheet with reinforced hyaluronic acid carrier was applied to the defect. Only the hyaluronic acid carrier was applied to the contralateral side as a control (five defects). Eight weeks after surgery, the animals were sacrificed and decalcified specimens were prepared. Healing of the periodontal defects was evaluated histologically and histometrically. RESULTS: No clinical signs of inflammation or recession of gingiva were observed in both experimental and control groups. In the experimental group, periodontal tissue healing with bone, periodontal ligament and cementum formation was observed in three out of five defects. In the control group, such periodontal tissue formation was not observed except in one defect. Histometric analysis revealed that the formation of new cementum in the experimental group was significantly higher than that in the control group. CONCLUSION: The periodontal ligament cell sheet has a potential to regenerate periodontal tissue and may become a novel regenerative therapy.     

人牙骨质,牙周膜,牙槽骨中Ⅰ,Ⅲ,型胶原的检测

本研究目的为检测人牙骨质、牙周膜和牙槽组织中Ⅰ、Ⅲ、Ⅳ型胶原的分布和含量。应用免疫组化和图像分析法测得：Ⅰ型胶原占牙周膜的７８．０６％、牙骨质的７３．０９％和牙槽骨的３０．５０％；Ⅲ型胶原占牙周膜的１１．７３％，在根尖部牙骨质和相对应的牙槽窝骨组织也观察到Ⅲ型胶原；４型胶原仅见于血管基膜。     

The regenerative potential of the periodontal ligament

Abstract The aim of the present study was to examine if new cementum and new attachment may form during healing of a wound prepared in such a way that preference is given to periodontal ligament ceils to repopulate the wound area adjacent to a root which has been surgically deprived of its periodontal ligament and cementum layer. The maxillary lateral incisors and mandibular canines in three monkeys were used for experimentation. Following elevation of a mucoperiosteal flap, the buccal and approximal alveolar bone was removed within an area extending from the mid-root level to a level 2 mm apical to the marginal bone crest. Following bone removal, the root surfaces were curetted in order to remove the cementum layer. Notches were prepared in the roots to demarcate the denuded root portion. Prior to repositioning of the tissue flap a millipore filter was placed over the treated area in order to prevent the gingival connective tissue from coming into contact with the root surface during healing. The animals were sacrificed 6 months after surgery. The jaws were removed and histological sections of the experimental teeth and surrounding periodontal tissues were produced. New cementum with inserting collagen fibers was observed on the curetted root surfaces. However, this result of healing did not consistently occur along the entire length of the curetted root portion. In the coronal part of the wound, healing was frequently characterized by connective tissue adhesion to the root surface without signs of cementum formation and fibrous attachment. The results of the experiment suggest that the periodontal ligament cells possess the ability to reestablish connective tissue attachment.     

Clinical,radiographic, and histologic evaluation of human periodontal defects treated with Bio-Oss and Bio-Gide

This study evaluated the clinical, radiographic, and histologic response to Bio-Oss porous bone mineral when used alone or in combination with Bio-Gide bilayer collagen membrane in human periodontal defects. Four intrabony periodontal defects were treated: two received Bio-Oss alone and two were treated with a combination of Bio-Oss and Bio-Gide. Radiographs, clinical probing depths and attachment levels were obtained preoperatively and 6 to 9 months postoperative, and teeth and surrounding tissues were biopsied. Both treatments significantly improved clinical probing depths and attachment levels, and the radiographic appearance suggested osseous fill. Histologic evaluation revealed that both treatments produced new cementum with inserting collagen fibers and new bone formation on the surface of the graft particles; this regenerative effect was more pronounced using the Bio-Oss/Bio-Gide combination, which resulted in 7 mm of new cementum and periodontal ligament and extensive new bone incorporating the graft. The membrane was intact at 7 months and partially degraded by 9 months after treatment. This human histologic study demonstrates that the porous bone mineral matrix used has the capacity to stimulate substantial new bone and cementum formation and that this capacity is further increased when the graft is used with a slowly resorbing collagen membrane.     

Effects of occlusal loading on ankylosis, bone, and cementum formation during bone morphogenetic protein-2-stimulated periodontal regeneration in vivo.

BACKGROUND: The purpose of this study was to investigate the influence of occlusal loading on recombinant human bone morphogenetic protein-2 (BMP-2)-induced bone and cementum formation in a previously established rat model of periodontal regeneration during the early and late stages of wound healing. METHODS: 64 Wistar rats were divided into 8 groups and had surgically created fenestrated defects on the right side of the mandible involving the removal of bone and exposure of the first and second molar roots. Four groups had their right maxillary molars extracted 2 weeks prior to surgery. Ten microl of 100 ug/ml BMP-2 in a collagen membrane was placed in extracted (hypofunctional) and non-extracted (functional) groups (BMPe and BMPf, respectively) while control groups had collagen membrane only (CONe and CONf). Groups were sacrificed at 10 (BMPe, BMPf, CONe, CONf) or 35 days (BMP35e, BMP35f, CON35e, CON35f) postoperatively and tissues processed for histological examination. Transverse 5 microm sections were stained for identification of new bone, ankylosis and cementum formation. Results: At 10 days, CONe developed greater bone growth compared with CONf (P<0.05), while both BMP groups developed greater bone compared with controls. However, BMPe developed more ankylosis compared with both CONe and CONf while BMPf was significantly greater than CONf only (P<0.05). BMPf only developed significantly greater new cementum compared with controls. At 35 days, BMP35f developed greater bone growth compared with all other groups including BMP35e (P<0.05) and unlike results at 10 days, no differences were apparent between CON35f and CON35e. Unwanted bone growth beyond the defect margin anteriorly was significantly greater in BMP35f. Conclusions: Results suggest hypofunction stimulates early bone formation. Furthermore, hypofunction and BMP-2 increase the development of transient ankylosis. However, after wound healing is complete, function augments the early effects of BMP-2-induced new bone growth indicating remodeling to physiological levels does not occur. Finally, occlusal loading is both an important stimulus for remodeling and establishment of the periodontal ligament space during early wound healing as well as enhancing BMP-2-induced cementogenesis.     

Enhanced cementum formation in experimentally induced cementum defects of the root surface with the application of recombinant basic fibroblast growth factor in collagen gel in vivo

BACKGROUND: Therapies using biologically active, soluble factors such as growth factors or cytokines have been investigated for potential clinical use in regenerating lost periodontal tissue due to periodontitis. Basic fibroblast growth factor (bFGF, FGF-2) is a multifunctional growth factor that has a variety of effects including induction of proliferation and morphogenesis in a wide range of cells and tissues including periodontal ligament tissue. METHODS: In this study, we examined the effects of bFGF on the regeneration of cementum and periodontal ligament in experimentally induced partial defects in a beagle dog model. bFGF in a collagen gel was applied to the defects and root surfaces, and the teeth were replanted. RESULTS: Eight weeks post-surgery, formation of cementum on denuded dentin was enhanced by application of 0.1, 1, or 5 microg of bFGF in a collagen gel compared to collagen gel containing vehicle. Histological analyses revealed that at 4 weeks post-surgery, random periodontal ligament fibers had bound to dentin, but were attached only to denuded dentin to which 0.1, 1, or 5 microg of bFGF in collagen gel had been applied. At 8 weeks post-surgery, we observed the formation of dense fibers bound to alveolar bone and newly synthesized cementum in teeth treated with 1 microg of bFGF. CONCLUSION: These results suggest that basic fibroblast growth factor in a collagen gel is a suitable therapy for damaged periodontal ligament and could lead to readily achievable methods of treatment for periodontal disease.     

Periodontal ligament cell sheet promotes periodontal regeneration in athymic rats

Aim: The primary goal of periodontal treatment is regeneration of the periodontium. Current theories suggest that the periodontal ligament (PDL) cells have the capacity to participate in restoring connective and mineralized tissues, when appropriately triggered. We evaluated whether human PDL cell sheets could reconstruct periodontal tissue. Material and Methods: To obtain the cell sheet, human PDL cells were cultured on temperature‐responsive culture dishes with or without osteogenic differentiation medium. The cell sheets were transplanted on periodontal fenestration defects of immunodeficient rats. Forty rats were divided in two groups: in one group, cell sheets cultured with control medium were transplanted and in the other, cell sheets cultured with osteogenic differentiation medium were transplanted. The defects were analysed histologically and histomorphologically after healing. Results: Most of the experimental group exhibited a new cementum‐like layer and new attachment of collagen fibres to the layer. Histomorphological analyses indicated significant periodontal regeneration. The control group revealed dense extracellular matrix and fibre formation, but an obvious cementum layer was not observed. Conclusions: Transplanted PDL cell sheets cultured with osteogenic differentiation medium induced periodontal regeneration containing an obvious cementum layer and Sharpey's fibres. Thus, the method could be feasible as a new therapeutic approach for periodontal regeneration.     

多孔β-TCP/BMP复合人工骨引导牙周组织再生的实验研究

目的 将骨形成蛋白(bone morphogenetic protein,BMP)和多孔β磷酸三钙(β-tricalcium phosphate,β-TCP)复合人工骨联合应用于引导组织再生(guided tissue regeneration,GTR)技术中,评价其对Ⅱ度根分叉病变牙周组织再生修复的影响和意义.方法 用健康成年杂种狗4只,制备下颌后牙区人工骨缺损.实验牙位随机分为3组:①骨形成蛋白/引导组织再生(BMP/GTR)组:缺损处植入引导膜材料和复合人工骨;②GTR组:单纯放置引导膜材料;③以常规翻瓣术为对照组.术后12周取材做组织学观察和评价.结果 两实验组均有明显新附着形成,其中BMP/GTR组有大量新生牙槽骨、牙骨质、牙周韧带生长.对照组新生组织量很少.结论 β-TCP/BMP是一种具有较强骨诱导能力,生物相容性较好的复合人工骨,在引导牙周组织再生术中有良好的应用前景.     

Ultrastructural study of experimental cementum regeneration in rats

The present study examined two phases of experimental cementum regeneration at the ultrastructural level. Small fenestration wounds (1 mm in diameter) were made on the mesial root of mandibular first molars in 20 Lewis strain rats to remove cementum and periodontal ligament. The wounds were covered with sheets of Nucleopre filter, before replacing the extraorat flaps, to allow population of denuded roots by cells arising mainly from the adjacent periodontal ligament. The rats were sacrificed in two batches of 10 each to provide observation periods of 2 and 4 weeks. The specimens were processed for transmission electron microscopy. At 2 wk, fibroblasts exhibiting ultrastructural features suggestive of various stages of synthetic activity were seen in the wound and adjacent to denuded root surfaces which appeared irregular. At 4 wk, cementoid regeneration was seen with bundles of oriented collagen fibrils inserting into the cementoid matrix. A consistent finding at both observation periods was the presence of an electron-dense, granular zone between the cementum/collagen matrix and the denuded root surface. Contrary to previous reports, the electron-dense zone appeared bi-layered with collagen fibrils and filamentous material in the superficial layer. At both observation periods, synthetic activity and matrix organization were more advanced in areas away from the root surface (fibrillogenesis) compared to areas adjacent to the root surface (cementogenesis). The present findings suggest that some important cellular and molecular events, possibly regulatory in nature, occur during the early stages of cementum regeneration in rats.     

Immunohistochemical localization of collagenous components in healthy periodontal tissues of the rat and marmoset (Callithrix jacchus).

The distribution of collagen types I and III was demonstrated in healthy periodontal tissues of the rat and marmoset using immunofluorescent localization after decalcification of the maxillae and mandiblae in 0.2 N HCl. An intense fluorescence in the alveolar bone and cementum matrix, as well as in the soft periodontal tissue, was demonstrated with anti-collagen type I antibodies. In the gingival connective tissue and in the periodontal ligament thick fibers of collagen type I could be observed. The fluorescent reaction in the rat periodontal ligament was not strong in comparison to the marmoset periodontal ligament. Sharpey's fibers, inserting into the cementum and alveolar bone, were also stained. On the other hand, collagen type III could not be demonstrated in the hard periodontal tissues, but could be in the bone marrow stroma and the incremental lines as well as around the Sharpey's fibers of the cementum, in accordance to previous studies. In the gingival connective tissue a strong staining was evident, especially near the basement membrane. The periodontal ligament showed an intense fluorescence that was, in some areas, continuous with Sharpey's fibers inserting into the cementum. The distribution of collagen types I and III was demonstrated with immunohistochemical techniques in the rat and marmoset periodontium. These results provide necessary information on healthy tissues that will be required for future studies on the effects of pathological, reparative and regenerative processes.     

Ankylosis of the mouse molar after systemic administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP)

Abstract The proposed homeostasis between fibroblasts in the periodontal ligament and bone cells lining the inner aspect of the alveolar wall is thought to be responsible for maintaining the width of the periodontal ligament space. In the present study, we attempted to interfere with this cellular balance by systemic administration of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP). The maxillary left molars of mice were extracted. They then received a daily subcutaneous injection of HEBP (10 mg P/kg b.w.) for periods of 10, 30 or 50 days. A 2nd group of animals received HEBP without molar extraction. Control groups were injected with Ringer's solution. The animals were sacrificed after the last injection and the mandibles processed for light and electron microscopy. HEBP treatment caused a significant decrease of the width of the periodontal ligament space which was influenced by time. Ankylosis started to occur after 30 days, predominantly in the interradicular areas and was more common around unopposed teeth. At 50 days, signs of resorption were seen along the acellular cementum layer. During HEBP-administration, extensive deposition of newly formed cementum matrix was observed along the cellular cementum but this activity was not seen along the acellular cementum. It is concluded that HEBP interferes with the mechanisms that mediate preservation of the periodontal ligament width.     

Clinical and histologic evaluation of an enamel matrix protein derivative combined with a bioactive glass for the treatment of intrabony periodontal defects in humans

The present study clinically and histologically evaluated healing of human intrabony defects following treatment with a combination of enamel matrix derivative (EMD) and bioactive glass (BG) or BG alone. Six patients displaying either combined one- and two-walled (five patients) or three-walled (one patient) intrabony defects around teeth scheduled for extraction were included. A notch was placed at the most apical extent of the calculus on the root surface to serve as a reference. Six months after surgery, the teeth or roots were extracted, together with some of their surrounding soft and hard tissues, and processed for histologic evaluation; a gain of clinical attachment was found in all cases. Healing in all three defects treated with EMD + BG was mainly characterized by new cementum with inserting collagen fibers and new periodontal ligament; most graft particles were surrounded by bone-like tissue, indicating ongoing mineralization. Treatment with BG resulted in epithelial down-growth and connective tissue encapsulation of the graft material in all three specimens. Reformation of cementum and periodontal ligament was observed in one of the specimens, limited to the most apical part of the defect. Formation of bone-like tissue around the graft particles was observed in only one of the three specimens treated with BG. Direct contact between the BG particles and root surface (cementum or dentin) was not observed in any of the six specimens. BG alone has low potential to facilitate periodontal regeneration. However, EMD + BG resulted in formation of new cementum with an associated periodontal ligament, as well as enhanced mineralization around the BG particles.     

Guided periodontal regeneration using bilayered collagen membranes and bovine bone mineral in fenestration defects in the canine

This study was performed to evaluate the effect of deproteinized bovine porous bone mineral (BBM) and BBM-collagen (BBMC) used alone or in combination with a bilayer collagen membrane in guided periodontal regeneration. In 12 dogs, contralateral surgical circular fenestration defects 5 mm in diameter were produced at the midbuccal aspect of the alveolar bone in 24 maxillary canines. Bone, periodontal ligament, and cementum were completely removed. Experimental sites were filled with BBM or BBMC. Bilayered collagen membranes covered half the experimental sites (BBM+M and BBMC+M), and the other half were left uncovered. Control sites remained empty; half were covered with collagen membranes (cont+M) and the underlying space spontaneously filled with blood, and half were left uncovered (cont). Three months postsurgery, undecalcified sections were prepared. Measurements were made using a caliper on a projection microscope, and the surface area of new bone and BBM particles within the healed surgical defect was evaluated using the point-counting method. In the experimental defects, new cementum covered 31% to 67% of the exposed dentin, with a significant difference between defects covered with membranes and defects that were not covered (P < .05). New cementum in the control (unfilled) defects also differed significantly between covered and uncovered defects. New bone growth presented a pattern similar to the cementum. There was no statistical difference between defects treated with BBM and BBMC, within both covered and uncovered groups. There was less connective tissue in the covered defects than in the uncovered defects (P < .05). The defects were filled with new bone, new connective tissue/bone marrow, and bovine bone particles. New bone area fraction was 23.4% to 25.2% in defects filled with BBMC and BBM, respectively (P = NS). Bone fraction area in membrane-covered defects ranged from 34.4% to 36.8% in experimental defects (P = NS). All membrane-treated defects showed higher values for bone area fraction in comparison to the uncovered control defects. Particle area fraction ranged between 17.4% and 26.2%, with only BBMC and BBM+M defects showing a statistically significant difference (P < .05). Defects filled with submembranous blood clot exhibited significantly more new cementum and bone regeneration than experimental defects filled with BBM or BBMC. Treatment of defects with BBM or BBMC showed similar influences on bone and cementum regeneration in fenestration periodontal defects. The presence or absence of bilayered collagen membranes was the predominant factor influencing bone and cementum regeneration.     

Employing a transgenic animal model to obtain cementoblasts in vitro

BACKGROUND: Proper formation of cementum, a mineralized tissue lining the tooth root surface, is required for development of a functional periodontal ligament. Further, the presence of healthy cementum is considered to be an important criterion for predictable restoration of periodontal tissues lost as a consequence of disease. Despite the significance of cementum to general oral health, the mechanisms controlling development and regeneration of this tissue are not well understood and research has been hampered by the lack of adequate in vitro experimental models. METHODS: In an effort to establish cementoblast cell populations, without the trappings of a heterogeneous population containing periodontal ligament (PDL) cells, cells were obtained from the root surface of first mandibular molars of OC-TAg transgenic mice. These mice contain the SV40 large T-antigen (TAg) under control of the osteocalcin (OC) promoter. Therefore, only cells that express OC also express TAg and are immortalized in vitro. Based on results of prior in situ studies, OC is expressed by cementoblasts during root development, but not by cells within the PDL. Consequently, when populations are isolated from developing molars using collagenase/trypsin digestion, only cementoblasts, not PDL cells, are immortalized and thus, will survive in culture. RESULTS: The resulting immortalized cementoblast population (OC/CM) expressed bone sialoprotein (BSP), osteopontin (OPN), and OC, markers selective to cells lining the root surface. These cells also expressed type I and XII collagen and type I PTH/PTHrP receptor (PTH1R). In addition to expression of genes associated with cementoblasts, OC/CM cells promoted mineral nodule formation and exhibited a PTHrP mediated cAMP response. CONCLUSIONS: This approach for establishing cementoblasts in vitro provides a model to study cementogenesis as required to enhance our knowledge of the mechanisms controlling development, maintenance, and regeneration of periodontal tissues.     

Mechanical removal of necrotic periodontal ligament by either Robinson bristle brush with pumice or scalpel blade. Histomorphometric analysis and scanning electron microscopy

One of the important factors accounting for successful delayed replantation of avulsed teeth is seemingly the type of root surface treatment. Removal of necrotic cemental periodontal ligament remnants may prevent the occurrence of external root resorption, which is the major cause of loss of teeth replanted in such conditions. The purpose of this study was to compare the efficacy of two mechanical techniques for removal of root-adhered periodontal ligament. Preservation or removal of the cementum layer concomitantly with these procedures was also assessed. Forty-five roots of healthy premolars extracted for orthodontic purposes were selected. After extraction, the teeth were kept dry at room temperature for 1 h and then immersed in saline for rehydration for an additional 10 min. Thereafter, the roots were assigned to three groups, as follows: group 1 (control)--the cemental periodontal ligament was preserved; group 2--removal of the periodontal ligament by scraping root surface with a scalpel blade (SBS); group 3--periodontal ligament remnants were removed using a Robinson bristle brush at low-speed with pumice/water slurry (RBP). The specimens were analysed histomorphometrically and examined by scanning electron microscopy. The quantitative and qualitative analyses of the results showed that the RBP technique was significantly more effective than the SBS technique for removal of the periodontal ligament remnants adhered to root surface. Both techniques preserved the cementum layer.