Towards the limit of quantifying low-amplitude strains on bone and in coagulum around immediately loaded oral implants in extraction sockets

The purpose of this study was to quantify strains in coagulum around immediately loaded oral implants in extraction sockets at the ex vivo level. Bilateral maxillary premolar teeth of two fresh human cadavers were extracted and psi 4.1 x 12 mm Straumann TE implants were placed in the sockets of first and second premolars by utilizing mesio-distal and palatal anchorage, respectively. Installation torque value (ITV) of each implant was measured by a custom-made torque wrench and resonance frequency analyses (RFAs) were undertaken to determine intraosseous stability. Upon abutment connection, a gold coping allowing the placement of a miniature load cell to contact the underlying solid abutment was fabricated. A linear strain gauge was connected to the coping at a distance for strain measurements in coagulum around the implant neck in the extraction socket. Linear strain gauges were also bonded on the labial marginal bone of each extraction socket. Strain measurements were performed at a sample rate of 10 kHz simultaneously monitored from a computer connected to data acquisition system and under a maximum load of 100 N on each implant with or without human coagulum in the extraction socket. Low-amplitude strains were measured around immediate implants. The increase in load increased strains on labial marginal cortical bone around implants (P < 0.05). Bone strains were higher on the implant loaded, when coagulum was present in the bone defects (P < 0.05). Strains within coagulum around mesiodistally anchored implants were higher than palatally anchored implants (P < 0.05). The type of implant on anchorage and presence of coagulum has an impact mechanotransduction to buccal marginal bone around immediate implants.     

失牙后牙槽骨骨量保存：人工骨替代、膜引导及骨组织工程再生

背景：失牙后的牙槽骨对稳定义齿、承载咬合力起着非常重要的作用。牙槽骨条件的好坏也直接关系到修复的治疗效果。因此,失牙后避免牙槽骨吸收,促进新骨生成显得尤为重要。 目的：综述近年来应用于保存牙槽骨骨量方法的研究进展,并讨论拔牙时牙周翻瓣术和即刻种植技术对保存牙槽骨骨量带来的不利影响。 方法：应用计算机检索2005至2011年 medline数据库及CNKI数据库有关失牙后牙槽骨骨量保存方法的研究进展方面的文章,英文检索词为“alveolar preservation,socket preservation”,排除重复性研究,共保留其中34篇进行归纳总结。 结果与结论：临床试验证明植入人工骨替代材料、膜引导骨再生技术、骨组织工程再生技术等方法能明显减少失牙后牙槽骨吸收的量,促进新骨生成,是目前较为有效的保存牙槽骨骨量的方法。而拔牙时的牙周翻瓣术虽给拔牙操作提供了更广阔的视野,但是加速了牙槽骨的吸收。动物实验和临床实验同时证明即刻种植技术,并不能有效阻止拔牙后牙槽骨的吸收。因此,拔牙时是否采用牙周翻瓣术或即刻种植技术应酌情考虑。     

The effect of calcium phosphate bone substitute on defect resolution around a rough-surfaced dental implants in dogs

Gap defects often exist around dental implants due to morphological differences between the natural tooth extraction socket and the dental implant. Techniques that can resolve such gap defects include implant surface modification and filling of the defects with bone substitutes. Modified surfaces are generally more effective in this regard than smooth surfaces. Favorable results have also been reported using bone substitutes. This study evaluated the effectiveness of a calcium phosphate (CaP) bone substitute for resolving gap defects around implant surfaces that have been treated with grit blasting and thermal etching. Implants were placed in edentulous areas in four mongrel dogs. Gap defects with a diameter of 2 mm were prepared surgically around the dental implants. These defects were either filled with CaP bone substitute (experimental group) or left unfilled (control group). Defects were evaluated after 8 and 16 weeks of healing. Block specimens were fixed, sectioned, and stained with hematoxylin and eosin. Histometric measurements revealed that healing in gap defects that had been filled with CaP bone substitute proceeded until 16 weeks. Total CaP degradation seemed to occur at between 4 and 8 weeks of healing. In conclusion, a more complete defect resolution was observed in gap defects filled with CaP bone substitute after 16 weeks than after 8 weeks of healing. The beneficial effects of filling in 2-mm gap defects around implants were attributed to the use of CaP bone substitute.     

富血小板凝胶与拔牙窝新骨形成和骨量保持

背景：富血小板血浆能否促进骨组织的修复再生存在一定的争议。 目的：研究富血小板血浆/凝胶对拔牙窝骨愈合过程中新骨形成和骨量保持的可能调节作用,探讨富血小板血浆/凝胶与骨愈合的相互关系。 方法：通过拔牙建立Beagle犬拔牙窝骨缺损模型,同期在拔牙窝导入富血小板血浆或复血小板凝胶,并设计对照组。术后2,4,8,12周分别进行大体观察、放射影像学检查、三维CT平扫+重建、组织学检查拔牙窝颊舌侧牙槽嵴高度差、CT值以及新生骨面积。 结果与结论：与富血小板血浆组和对照组比较,影像学结果表明富血小板凝胶组在第2,4,8周新骨形成的面积最大(P < 0.01);组织学结果表明富血小板凝胶组在第2,4周新骨形成面积最大(P < 0.05);在所有时间点上富血小板凝胶组颊舌侧牙槽嵴高度差值最小(P < 0.05)。在第12周,富血小板凝胶组颊舌侧牙槽嵴高度仍有2 mm差值。提示,富血小板凝胶具有促进牙槽窝早期愈合的能力,但其单独使用时促进牙槽窝骨量保持的效能有限。     

Alveolar bone regeneration in post-extraction socket: a review of materials to postpone dental implant

Tooth extraction usually involves alveolar bone loss and reduction in height and width of the remaining alveolar socket, owing to the physiological bone resorption. This occurrence may perform an inadequate bone profile, that make difficult orthodontic applications, compromising the functional and aesthetic restoration of dental implants. The present review will provide an update on the biological and clinical profile of materials currently in use and those under investigation, in the recovering of bone margins of edentulous sockets.     

Differentiation of periodontal ligament fibroblasts into osteoblasts during socket healing after tooth extraction in the rat

Background: The entire socket after tooth extraction is filled with new bone formed by osteoblasts (Obs), but the origin of these Obs remains unknown. Thus, the proliferation and migration of paravascular and endosteal fibroblastic cells and periodontal ligament (PDL) fibroblasts (Fbs) and their differentiation into Obs during socket healing after extraction of the first maxillary molars of the rat were investigated. Methods: The proliferative activity and migration of these cells in the sockets after tooth extraction were studied using radioautography and immunohistochemistry after injection of ³H-thymidine and 5-bromo-2′-deoxy-uridine (BrdU), respectively. Their morphological changes during differentiation was investigated by transmission electron microscopy. Results: One day after tooth extraction, PDL Fbs were the major cell type in the PDL remnant of the socket. Proliferation was low (labeling index (LI) = approximately 2%) until 16 h after tooth extraction but dramatically increased to a maximum level 1 day postextraction (LI = 23%). Between 1 and 2 days, numerous PDL Fbs in the PDL remnant actively migrated into the coagulum and continued to proliferate. On the basis of the high proliferative activity and small number of cellular organelles responsible for procollagen synthesis, these cells appear immature. At 3 days, Fbs contained more cellular organelles and deposited more collagen fibers as they replaced the coagulum with dense connective tissue and the LI declined. At 4 and 5 days, some of the Fbs began to differentiate into Obs, and the proliferation of Fbs dramatically decreased to baseline values. The migration of PDL Fbs and their differentiation into Obs were investigated by labeling with ³H-thymidine or BrdU 1 day after tooth extraction. Heavily labeled Fbs were observed in the PDL remnant at 1 day, in the coagulum at 2 days, and in the dense connective tissue at 3 days. Labeled Obs associated with new bone were seen 4 days after injection. Endosteal and paravascular Fbs also proliferated, but at a lower level and at later time periods than the PDL Fbs. Surprisingly, endosteal and paravascular Fbs contributed only a small population of Fbs to socket healing. Conclusions: These results indicate that PDL Fbs after tooth extraction actively proliferate, migrate into the coagulum, form dense connective tissue, and differentiate into Obs which form new bone during socket healing. © 1994 Wiley-Liss, Inc.     

Early bone healing events following rat molar tooth extraction

Healing of the rat tooth extraction socket occurs rapidly, indicating a mechanism for cancellous bone formation occurring swiftly throughout the matrix. The residual periodontal ligament is evident at 2 days after extraction and its rich collagen type III fibre content may form a template for future cancellous bone formation. In the remainder of the early tooth extraction socket, fibronectin staining was generalized. The widespread distribution of fibronectin staining has given rise to speculation that the function of fibronectin may be important in granulation tissue formation, by providing a template matrix for fibroblast migration. Osteoprogenitor cells migrated into the socket from the surrounding bone, and produced decorin and proMMP-13 (procollagenase-3). ProMMP-13 was only expressed at sites of new bone formation, e.g. the border of the recently formed trabecular islands or the periphery of the closing socket. Collagen type I fibres were formed later, and were especially evident at 6 days after extraction. The pattern of distribution of both collagen type I and III fibres were similar as they passed from the bone margin towards the centre of the socket - in the same direction as the forming bone trabeculae. Bone formation occurs by rapid movement of the osteoprogenitor cells along these collagen fibres to allow a rapid healing, rather than that of resorption followed by slow bone deposition.     

Bone augmentation with bioactive glass in three cases of dental implant placement

This study reports the clinical use of a bioactive bone graft material, PerioGlas, in the treatment of dental extraction sites before dental implant placement, to effect bone regeneration and to give early fixation to the implant.PerioGlas, granules, ranging from 90 to 710 mm, are implanted after tooth extraction in three patients; after 6 months bone biopsies were performed in the site of the glass implantation and observed under Electron Scanning Microscopy.All the granules showed a biodegradation involving precipitation of calcium phosphate that worked as a scaffold for osteoblasts colonization. All cases examined showed the bioactivity of PerioGlas granules resulting in new bone formation and biodegradation of the glass. After a two-year clinical follow-up all the implants were successfully loaded and appeared stable.     

A Comparative Finite-Element Analysis of Bone Failure and Load Transfer of Osseointegrated Prostheses Fixations

An alternative solution to conventional stump–socket prosthetic limb attachment is offered by direct skeletal fixation. This study aimed to assess two percutaneous trans-femoral implants, the OPRA system (Integrum AB, Göteborg, Sweden), and the ISP Endo/Exo prosthesis (ESKA Implants AG, Lübeck, Germany) on bone failure and stem–bone interface mechanics both early post-operative (before bony ingrowth) and after full bone ingrowth. Moreover, mechanical consequences of implantation of those implants in terms of changed loading pattern within the bone and potential consequences on long-term bone remodeling were studied using finite-element models that represent the intact femur and implants fitted in amputated femora. Two experimentally measured loads from the normal walking cycle were applied. The analyses revealed that implantation of percutaneous prostheses had considerable effects on stress and strain energy density levels in bone. This was not only caused by the implant itself, but also by changed loading conditions in the amputated leg. The ISP design promoted slightly more physiological strain energy distribution (favoring long-term bone maintenance), but the OPRA design generated lower bone stresses (reducing bone fracture risk). The safety factor against mechanical failure of the two percutaneous designs was relatively low, which could be improved by design optimization of the implants.     

Preservation and regeneration of alveolar bone by tissue-engineered implants

Bone maintenance after dental extraction has a significant impact on the success of future treatment. The purpose of this study was to regenerate bone by implanting an engineered porous scaffold seeded with bone marrow mesenchymal stem cells (BMSCs) in a socket created by extraction of the lower left central incisor in rabbits, utilizing the principles of tissue engineering. It involved preparation and characterization of three-dimensional porous hollow root form scaffolds consisting of a poly-L-lactic acid:polyglycolic acid composite (PLG, 50:50), using a solvent casting/compression molding/particulate leaching technique. Porosity of the scaffolds was 83.71% with good interconnectivity and uniform distribution of the various pore sizes. The degraded scaffolds maintained their porosity and form for the first 2 weeks and their mass loss continued up to 6 weeks. The scaffolds developed viscoelastic behavior under dynamic compression; yet they lost their mechanical characteristics as they degraded. The scaffolds were seeded with BMSCs and examined by scanning electron microscopy. Cell proliferation and scaffold degradation were shown up to 2 weeks in vitro. The cultivated scaffolds were implanted in empty extraction sockets immediately after tooth removal. Four weeks later, bone regeneration was evaluated histologically in the healed sockets in three experimental groups: sockets left empty, sockets that received PLG without cells, and sockets that received PLG with cells. Radiographic evaluation, performed 4 weeks later for the three experimental groups, demonstrated preservation of alveolar bone walls in the extraction sockets that received PLG with cells as compared with the other two groups. The bone density profile for the healed sockets confirmed both histological and radiographic findings. The results of this study show promise in the area of dentoalveolar surgery, yet longitudinal studies under variable clinical situations would encourage the current application.     

矿化胶原与镁钙合金的复合材料用于犬拔牙位点保存的实验研究

目的　研究矿化胶原复合镁钙合金用于犬拔牙位点保存的可行性。 方法　拔除8只杂种犬下颌双侧第4前磨牙,共32个拔牙窝（近中和远中牙槽窝各16个）,随机分为A、B两组。A组植入矿化胶原复合镁钙合金材料,B组仅植入矿化胶原材料,于术后12,24周处死实验犬,制备组织标本,通过大体观察、CBCT、肝肾组织学切片观察以及X射线显微镜检测评价拔牙窝愈合情况及肝肾组织的损伤情况。 结果　两组材料在拔牙窝愈合过程中,逐渐被降解吸收,新生骨组织不断形成。术后12周,实验A组的相对骨密度值以及新生骨组织数量均多于B组,差异有统计学意义（P＜0.05）。术后24周,A、B两组的新生骨组织数量逐渐增多,两组相对骨密度值差异不显著（P＞0.05）。 结论　矿化胶原与镁钙合金的复合材料可用于犬拔牙位点的保存,可促进新骨再生,减缓牙槽嵴的吸收。     

Effect of umbilical cord mesenchymal stem cell in peri-implant bone defect after immediate implant: an experiment study in beagle dogs

Background: For the sake of reducing post extraction resorption, getting optimal positioning of the implant and shortening treatment time, immediate implant placement following tooth extraction has been proposed as a treatment option. However, the large bone defect peri-implant has a negative influence on the process of bone healing. In this study, umbilical cord mesenchymal stem cells (UCMSCs) were transplanted into the bone defect peri-implant inbeagle dogs and the effect of UCMSCs on bone regeneration in peri-implant were assessed. Methods: The mandibular second, third and fourth premolars of 8 beagle dogs were extracted bilaterally. The defects in one side were filled with platelet-rich fibrin (PRF) and then UCMSCs were injected into the defect area, while the defects in the other side were filled with PRF only as control group. The titanium implant was placed into the distal root socket of each extracted tooth. The animals were sacrificed at week 2, 4 and 8 post operative. The bone defects adjacent to the implant which are 4 mm in height, 4 mm in the mesio-distal direction and 3.5 mm in the bucco-lingual direction were made after immediate implant. Histomorphometric analysis was performed using methylene blue-fuchsin acid staining and hematoxylin and eosin (HE) staining to evaluate bone regeneration. Results: The direct bone-to-implant contact (BIC) in the experiment after 4 and 8 weeks was 56.47±1.18% and 76.23±2.08%; and in the control group was40.79±0.65% and 61.17±2.79%, respectively. The percentage of newly formed bone after 2, 4 and 8 weeks was 17.60±1.5%, 49.82±4.02% and 67.16±2.1% in experiment group; and in control group 14.30±1.25%, 37.04±2.29% and 58.83±3.36%, respectively. These results represented significant differences statistically. Conclusion: Intra-bone marrow injection of UCMSCs can promote new bone formation. UCMSCs can be used to as excellent seed cells to repair the large defect peri-implant after immediate implant.     

面向即刻种植的种植体的初期稳定性研究

在即刻种植中,良好的种植体初期稳定性是种植成功的关键。牙周炎、外伤以及拔牙时可能导致患者牙槽骨受到破坏出现的骨壁缺损,以及种植体与牙槽窝之间的过盈量,对种植体的初期稳定性均会造成影响。针对临床上种植体周围不同的骨壁缺损程度建立一种新的分类模型,并基于该分类模型,借助有限元分析软件ABAQUS,模拟在不同的过盈量、骨壁缺损程度下面向即刻种植的拟自然牙种植体的初期稳定性。将种植体种植到模拟骨块上,通过种植体稳定性测量仪测量出种植体稳定系数(ISQ),评价种植体的初期稳定性,进行实验比较分析。结果发现:随着过盈量的增加,初期稳定性升高;随着骨缺损程度的增加,初期稳定性下降。在三壁骨缺损下,当种植体与种植窝之间无过盈量时,其ISQ值均小于40;而当过盈量为0.2 mm时,其ISQ值均大于50。这说明,种植体与种植窝之间是否有过盈量,对种植体初期稳定性的影响非常大。当种植体周围是一壁骨缺损时,其ISQ值基本都小于40,此时应增大过盈量来增加种植体的初期稳定性。针对不同程度的骨壁缺损,种植体在设计时所需的过盈量是不同的,这为之后面向即刻种植的个性化拟自然牙种植体的设计提供一定的理论参考。     

Healing of tooth extraction sockets in the streptozotocin diabetic rat model: Induction of cartilage by BMP-6

Cartilage does not form in the tooth extraction socket of the normal rat. The aim of the study was to determine if adding BMP-6 to the extraction socket would cause chondrogenic differentiation in the diabetic rat.

A group of 8-week-old rats were injected intraperitoneally with a diabetogenic agent, streptozotocin, and a control group received citrate buffer only. Three weeks later, the maxillary molar teeth were extracted and either BMP-6 or saline applied to the extraction sockets. Rats from each group were killed on days 3, 5, 7, and 9 after tooth extraction. In the diabetic rats treated with BMP-6, there was a cellular subperiosteal reaction at day 3 in the extra-alveolar tissues, which by day 7 had formed a large mass of cartilage.

Cartilage was induced in the subperiosteal region of the socket extra-alveolar bone following the application of BMP-6 in the diabetic rat.     

Histological and histomorphometric investigations on bone integration of rapidly resorbable calcium phosphate ceramics

Resorbable ceramics can promote the bony integration of implants. Their rate of degradation should ideally be synchronized with bone regeneration. We report here the results of a histological study of implants with two resorbable calcium phosphate ceramic coatings: Ca(2)KNa(PO(4))(2)-(GB14) and Ca(10)[K/Na](PO(4))(7)-(602020). The results attained with these ceramic-coated implants show the benefits of these materials with regard to bioactive bone-healing stimulation, compared with uncoated implants. The GB14 ceramic coating exhibited greater bone regeneration and differentiation on its surface than the conventional hydroxyapatite coating and helped bone tissue achieve more extensive contact free of connective tissue. Not until the coating disintegrated did the histological features of GB14- and 602020-coated implants converge-both implant types were integrated into bone. Rapid disintegration of the coating material, as with 602020, supports osteoblast proliferation but has negative effects on bone mineralization. Both resorbable ceramics tested, GB14 and 602020, demonstrated bioactivity; even metal surfaces coated with these materials were populated by mature bone tissue without connective tissue after disintegration of their ceramic coating. The less rapidly degrading material, GB14, achieved better results. Degradable calcium phosphate coatings have the potential to stimulate bone regeneration. From the histological viewpoint, the resorbable ceramics examined here can be recommended as coating materials for clinical use.     

骨引导再生术在牙种植术中的临床应用

目的评估Bio—Gide生物膜、Bio—oss骨粉引导骨组织再生修复种植床骨缺损的作用。方法选择种植区牙槽骨存在骨缺损的11例患者．其中男性9例．女性2例．年龄18～56岁。共计ll枚种植体。植入种植体后,在骨缺损处植入Bio～oss骨粉．并用Bio-Gide生物膜覆盖．术后、Ⅱ期手术前进行口腔临床检查和X射线检查。种植修复体完成后,分别于戴牙后6、12个月定期复诊．检查种植体周围骨组织的吸收及种植体周围软组织情况。结果术后2周内有1枚种植体覆盖黏膜少许裂开．Ⅱ期手术时,1枚种植体周围形成纤维愈合而失败,后经重新种植,所有种植体均顺利完成种植修复。修复后随访6～12个月．种植体均能成功地恢复咀嚼功能。结论Bio—Gide生物膜、Bio-oss骨粉可以引导骨组织再生,改善种植床骨增量效果。与正常骨组织中种植修复的1年成功率不存在明显差异。     

Proliferative activity, apoptosis, and histogenesis in the early stages of rat tooth extraction wound healing

We examined the proliferative activity, apoptosis, and histogenesis in the early stages of the rat healing socket from just after extraction until new bone formation occurs. Thirty 11-week-old male Wistar rats underwent bilateral maxillary first molar tooth extraction. Five craniomaxillary tissue specimens were dissected at the following time points: at 12 h, days 1, 3, 5, 7 and 10 after surgery. The immunohistochemical expression of both proliferating cell nuclear antigen (PCNA) and the Ki67 counterpart of rodent (MIB5) for proliferative activity and both the TUNEL reaction and the immunohistochemical expression of single-strand DNA for apoptosis were evaluated using 6-mum-thick serial paraffin sections, which were prepared in the coronal plane. The positive cell counts in the socket were converted into the cell numbers per mm(2) as either the proliferative index (PI) or the apoptotic index (AI). The PI and the AI showed maximum levels at 5 days and 12 h after extraction, respectively. The proliferative activity in the early stages of extraction wound healing is initially distributed in the remaining periodontium with load-induced apoptosis, next in the proliferative fibrous tissue, and then around the trabeculae of the new bone marking its peak.     

牙髓干细胞修复种植体周围骨缺损的研究

目的 建立兔下颌骨前牙即刻种植种植体周围骨缺损的动物模型,考察牙髓干细胞(DPSCs)在种植体周围骨缺损中的骨再生能力.方法 将8只新西兰白兔随机分为两组,分别拔除兔双侧下颌前牙,在拔牙窝颊侧建立2 mm×3 mm骨缺损区,即刻植入种植体,对照组植入Bio-oss骨粉和磷酸盐缓冲液,实验组植入Bio-oss骨粉和DPSCs.通过大体观察和组织学观察(苏木精-伊红染色、Goldner's三色染色和扫描电镜观察)评价植入后4周骨缺损区的骨再生能力.结果 所有实验兔种植体植入顺利,且种植体植入后均稳固,无明显差异.苏木精-伊红和Goldner's三色染色观察均可见实验组有新生骨组织形成,且部分新生骨组织为编织骨,骨细胞体积大、数量多,呈编织状排列,骨细胞分化成熟;而对照组可见少量新生骨样组织形成,骨细胞分化较成熟.扫描电镜结果显示,实验组新生骨与种植体间的骨结合较对照组多.结论 与单独使用Bio-oss骨粉比较,DPSCs与Bio-oss骨粉联用的成骨能力相对较强,新生骨组织与种植体的结合能力更好.     

Healing of tooth extraction sockets in the streptozotocin diabetic rat model: Induction of cartilage by BMP-6

Cartilage does not form in the tooth extraction socket of the normal rat. The aim of the study was to determine if adding BMP-6 to the extraction socket would cause chondrogenic differentiation in the diabetic rat. A group of 8-week-old rats were injected intraperitoneally with a diabetogenic agent, streptozotocin, and a control group received citrate buffer only. Three weeks later, the maxillary molar teeth were extracted and either BMP-6 or saline applied to the extraction sockets. Rats from each group were killed on days 3, 5, 7, and 9 after tooth extraction. In the diabetic rats treated with BMP-6, there was a cellular subperiosteal reaction at day 3 in the extra-alveolar tissues, which by day 7 had formed a large mass of cartilage. Cartilage was induced in the subperiosteal region of the socket extra-alveolar bone following the application of BMP-6 in the diabetic rat.     

Evaluation of porous collagen membrane in guided tissue regeneration

Porous collagen membrane was prepared with collagen protein, which was extracted from bovine tendon by enzyme digestion, by freeze-drying method. The animal, clinical experiments of the membrane used in artificial dental implant system were studied. In the animal experiments, pure titanium spiral implants, which were prepared according to Adell etc. method, were implanted in the mandibular dental alveus of adult hybrid dog and covered with collagen membrane. Then the animals were killed after 4, 18 weeks individually. In the clinical research, the implants (phi 3.3 mm) were used in 33 patients of different age groups. The implant was put on the buccal lateral deficiency of implantation cavity wall, and covered with collagen membrane on the buccal lateral, then observed after 3, 6 months individually. The results of animal experiments proved the collagen membrane could guide osseous tissue regeneration around the bone integral implant which was implanted in the fresh tooth extraction fossa, be helpful to repair the fissural bone deficiency produced when implanted the implant, increase the bone content around the implant significantly, and improve the structure of new bone to a certain extent. The results of clinical research proved that collagen membrane was used in the patients with density deficiency, irregularity of alveolar ridge, or artificial dental of shorter tooth extraction, could significantly improved the bone density of artificial implant's shoulder.