Research into changes in canine maxillary trabecular bone orientation after tooth extraction.

This paper described the morphological changes in the trabecular bone orientation of the jaw bone due to reduction in the applied functional pressure. All teeth on the right side of the upper and lower jaws were extracted from canine specimens. Experimental periods were set at 0.5, 1, 1.5, 2, 2.5, 3, 5, 7, 9, 11, and 13 months after tooth extraction. The trabecular bone orientation was measured by an image analyzer as morphometrical parameters. The loss of teeth changed the support system for functional pressure, resulting in the marked disordering of the trabecular bone orientation.     

Comparison of three block bone substitutes for bone regeneration: long-term observation in the beagle dog

This study aimed to evaluate the impact of three types of block bone substitute material on bone formation and graft resorption in vivo. Standardized bone defects (n?=?4 defects/animal) were created in the calvaria of nine dogs. Block bone substitutes made of deproteinized bovine bone mineral (DBBM), beta-tricalcium phosphate (β-TCP) and a mixture alpha-TCP and hydroxyapatite (α-TCP/HA) were inserted into the bone defects. A fourth defect was left untreated (empty). All sites were covered with a collagenous membrane. Block biopsies were harvested at 3, 6 and 12 months post-implantation and analyzed by micro-CT and histology. Biomaterial absorption was minimal and incorporation within the defect margin was good for all biomaterials. However, β-TCP demonstrated a relatively greater volume of new bone formation and less residual material volume when compared with DBBM and α-TCP/HA. Conversely, α-TCP/HA showed higher osteoconductive potential and a greater new bone area compared with the other two biomaterials. The block bone substitutes used in the present in vivo study showed advantageous in terms of maintenance of their original form in bony defect. However, the positive impact of all biomaterials on new bone formation and replacement of bone was minor even at 12 months. These findings indicate that block bone substitutes are not well suited to vertical bone augmentation. Further investigations are required to improve the insufficient new bone volume for promising clinical results.     

Dynamics of bone tissue formation in tooth extraction sites. An experimental study in dogs

OBJECTIVES: The aim of the present experiment was to study events involved in the healing of marginal, central and apical compartments of an extraction socket, from the formation of a blood clot, to bone tissue formation and remodeling of the newly formed hard tissue. MATERIAL AND METHODS: Nine mongrel dogs were used for the experiment. The fourth mandibular premolars were selected for study and were divided into one mesial and one distal portion. The distal root was removed and the socket with surrounding soft and mineralized tissue was denoted "experimental unit". The dogs were killed 1, 3, 7, 14, 30, 60, 90, 120 and 180 days after the root extractions. Biopsies including the experimental units were demineralized in EDTA, dehydrated in ethanol and embedded in paraffin. Serial sections 7 microm thick were cut in a mesio-distal plane. From each biopsy, three sections representing the central part of the socket were selected for histological examination. Morphometric measurements were performed to determine the volume occupied by different types of tissues in the marginal, central and apical compartments of the extraction socket at different intervals. RESULTS: During the first 3 days of healing, a blood clot was found to occupy most of the extraction site. After seven days this clot was in part replaced with a provisional matrix (PCT). On day 14, the tissue of the socket was comprised of PM and woven bone. On day 30, mineralized bone occupied 88% of the socket volume. This tissue had decreased to 15% on day 180. The portion occupied by bone marrow (BM) in the day 60 specimens was about 75%, but had increased to 85% on day 180. CONCLUSION: The healing of an extraction socket involved a series of events including the formation of a coagulum that was replaced by (i) a provisional connective tissue matrix, (ii) woven bone, and (iii) lamellar bone and BM. During the healing process a hard tissue bridge--cortical bone--formed, which "closed" the socket.     

Study of structural changes in canine maxillary trabecular bone after tooth extraction

All teeth on the right side of the upper and lower jaws were extracted from canine specimens; and changes in maxillary trabecular-bone structure caused by the resultant reduction in functional pressure were studied by means of image analysis of trabecular-bone density, width, specific length (which indicates bone length to unit area), and trabecular-bone orientations. Results 1. Trabecular-bone density Over the 13-month period, in comparison with the normal side, trabecular-bone density on the experimental side dropped to 69.4% in the incisor region, 82.2% in the premolar region, and from 60.0 to 68.0% in the molar region. The greatest reduction occurred in the molar region. 2. Trabecular-bone width Over the 13-month period, in comparison with the normal side, trabecular-bone width on the experimental side dropped to 86.9% in the incisor region, 86.1% in the premolar region, and from 66.4 to 71.4% in the molar region. The greatest reduction occurred in the molar region. 3. Specific length Over the 13-month period, in comparison with the normal side, specific length on the experimental side dropped to 81.9% in the incisor region, 82.9% in the premolar region, and from 65.6 to 70.5% in the molar region. The greatest reduction occurred in the molar region. 4. Orientation No regular trabecular-bone orientation was observed in the tooth-extraction sockets. In the incisor region, trabecular bone was often distributed at from 100 degrees to 120 degrees in relation to the dental roots. As time passed after extraction, the amount of bone with this orientation gradually decreased. At 13 months, amounts with bone orientation of from 40 degrees to 60 degrees had increased. In the premolar region, a great deal of trabecular bone was oriented at from 140 degrees to 150 degrees in relation to the dental roots. As time passed after extraction, the amount of bone with this orientation gradually decreased. At 13 months, amounts with bone orientation of from 110 degrees to 130 degrees had increased. In the molar buccal region, trabecular bone was often distributed at from 20 degrees to 40 degrees, and 90 degrees in relation to the dental roots. In the molar palatal region, trabecular bone was often distributed at from 120 degrees to 140 degrees in relation to the dental roots. At 13 months, the amount of trabecular bone oriented at about 90 degrees had increased.     

A review of bone substitutes

The use of bone grafts in the repair of defects has a long history of success, primarily with the use of autologous bone. With increasing technologic advances, researchers have been able to broaden the spectrum of grafting materials to allografts, xenografts, and synthetic materials, which provide the surgeon and patient with options, each with unique advantages. It is with the knowledge of each material that the clinician can present and suggest the best material and tailor treatment plans to fit each individual. In this article, we present an overview of the principles of bone grafting, the types of graft materials available, and an outlook to what the future holds in this area of medicine and dentistry.     

Histomorphometric evaluation of bone regeneration using allogeneic and alloplastic bone substitutes.

PURPOSE: The purpose of this investigation was to assess bone regeneration in critical sized defects in the rabbit calvarium using allogeneic and alloplastic bone substitutes. MATERIALS AND METHODS: Thirty New Zealand White rabbits were divided into 3 groups of 10 animals each. Bilateral 15 mm x 17 mm calvarial defects were made in the parietal bones of each animal. Group 1 had demineralized bone matrix (DBM) gel placed in one defect, while the other defect was left unfilled and served as the control. Group 2 had one defect filled with calcium hydroxide (CaOH)-treated DBM gel and the other defect filled with DBM gel. Group 3, the calcium-phosphate cement group, had Norian CRS (Norian Corp, Cupertino, CA) placed on one side and Bone Source (Howmedica Leibinger, Dallas, TX) placed on the contralateral side. Five animals in each group were killed at 6 and 12 weeks. Data analysis included qualitative assessment of the calvarial specimens and radiographic evaluation. Histomorphometric analysis was used to quantify the amount of new bone within the defects. RESULTS: Histomorphometric analysis showed that DBM gel-treated defects had significantly more new bone at 12 weeks compared with all other groups. There was no significant difference between defects filled with CaOH-treated DBM gel and those filled with DBM gel at 12 weeks. In group 3, Norian CRS- and Bone Source-treated defects were not statistically different from the unfilled controls. CONCLUSION: DBM gel was an effective allogeneic bone substitute that showed reliable osseous healing of critical size defects in the rabbit calvarium. The addition of CaOH to DBM gel did not significantly improve the bone regenerative capacity of the DBM gel. Both Norian CRS and Bone Source did not promote bone regeneration in this animal model.     

Bone formation following implantation of bone biomaterials into extraction sites

BACKGROUND: Adequate bone volume is imperative for the osseointegration of endosseous implants, but postextraction resorption and remodeling may challenge implant placement. The use of bone biomaterials has been advocated to fill extraction sites and to enhance primary implant stability during osseointegration. The objective of the case series was to evaluate bone formation histologically and biomechanically in extraction sites following implantation of three commercially available bone biomaterials to compare their ability to allow guided bone regeneration. METHODS: Thirty-six periodontally involved teeth were extracted from eight healthy non-smoking subjects. At least two bone biomaterials, a synthetic sponge based on polylactic-polyglycolic acid technology (FIS), bovine porous bone mineral (BPBM), or a natural coral derivative physically and chemically transformed into a calcium carbonate ceramic (COR), and one non-grafted control were applied to the extraction sockets within each subject and were covered by an expanded polytetrafluoroethylene device. The devices were removed after 2 months, and trephine biopsies were obtained from each site 4 months later. At that time, endosseous implants were placed in 25 of the sites, and healing abutments were placed; measurements were taken 4 to 6 months later with an electronic mobility testing device. RESULTS: The percentage of residual biomaterial was 5.6% +/- 8.9% for FIS (P <0.001), 20.2% +/- 17.0% for BPBM (P <0.05), and 12.0% +/- 16.4% for COR (P <0.001). The amount of residual biomaterial after 6 months showed a significant relationship with the insertion torque measurements during the first third of implant insertion (P <0.05) and with values of the electronic mobility testing device at the abutment connection (P = 0.05). Histologically, new bone apposition was seen on BPBM particles. FIS sites showed similar ingrowth of blood vessels and osteocytes as empty controls. CONCLUSION: All sites revealed good primary stability at implant insertion and proper implant rigidity at abutment placement, indicating that early implant osseointegration was not influenced by the application of bone biomaterials used in this study.     

3种骨代用品修复骨缺损的组织学定量分析

目的探讨无机牛骨(Bio-Oss),携带羧氨基的无机牛骨(PepGen P-15TM)及人工合成磷酸三钙(Cera-sorb)的骨缺损修复能力。方法健康成年雄性杂种犬18只,在两侧下颌骨制备4个直径9 mm、深3 mm的骨缺损,把3种骨代用品Bio-Oss,Cerasorb和PepGen P-15TM随机植入3个骨缺损中,分别作为Bio-Oss组、Cera-sorb组和PepGen P-15TM组;剩余1个骨缺损不植入骨代用品,作为空白对照组。术后1、3、6个月取样制片,以组织形态计量学法分析骨缺损修复率。结果 1、3、6个月时3个骨代用品组骨缺损区新骨形成率均高于空白对照(P<0.05);1个月时PepGen P-15TM组骨缺损新骨形成率(24.77%)高于Cerasorb组(15.33%)和Bio-Oss组(16.22%)(P<0.05);6个月时PepGen P-15TM组存留率高于Cerasorb组和Bio-Oss组(P<0.05)。结论3种骨代用品均具有骨缺损修复能力,且PepGen P-15TM的早期骨修复能力强于Bio-Oss及Cerasorb,但3者的长期骨修复能力无明显差异。3种材料中PepGen P-15TM存留率最高,但不影响新骨形成。     

骨替代材料在口腔种植领域中的成骨效果

骨替代材料目前已成为拔牙位点保存术、牙槽嵴骨增量术和上颌窦底提升术的主要材料,而羟磷灰石、磷酸钙和生物活性玻璃以其良好的生物相容性、骨传导性、生物降解性、骨再生能力和骨结合率成为骨替代材料的代表.单一成分骨替代材料的诱导骨再生能力取决于材料本身的表面形貌、结构、成分、孔径和孔隙率.按不同比例复合的新型骨替代材料,可使原单一骨替代材料的性能得以互补.骨替代材料与血小板浓缩物的联合应用,可促进前成骨细胞的增殖与分化,激发成骨细胞的活动,促进血管新生,从而利于骨替代材料存活.骨替代材料与生长因子的联合应用,可获得不同程度骨结合和骨改建,增加材料的细胞黏附率,改善支架的力学性能,在骨愈合早期即能促进新骨形成.随着科技的进步,未来骨替代材料的成骨性能日臻完善,在口腔种植领域的应用前景将会更加广阔.     

Comparison of ilium to rib for bone grafting in defects of canine mandibular alveolar fidge.

The behavior of iliac and rib grafts in surgically created defects in canine alveolar ridges was investigated. Despite the greater amount of potentially osteogenic tissue in the iliac graft, no significant qualitative differences were noted in the bony remodeling for a year. However, the rib grafts did form a mature superior cortical border significantly more rapidly, leading to speculation on the advantages of rib over iliac graft in alveolar ridge grafting.     

Human mineralized bone in extraction sites before implant placement: preliminary results

BACKGROUND: Bone loss after tooth extraction may prevent dental implant placement. Human mineralized bone grafts can be used to restore bone volume and allow for tooth replacement with dental implants. METHODS: The authors grafted 22 sites in 18 patients with human mineralized bone after tooth extraction. They allowed molar sites 16 weeks for graft healing, placed the implants and restored them with a final crown after a four-month integration period. Single-rooted maxillary sites received implants and immediate placement of provisional crowns or underwent a delayed two-stage restoration approach. The authors used radiographs and clinical examinations to evaluate the results. RESULTS: All of the sites were restored successfully with a single-tooth implant restoration. Periapical radiographs indicated that the crestal bone levels were limited to the first thread of the implants or slightly coronal to the first thread of the implant. Clinical evaluation indicated excellent gingival health around the provisional and final restorations, without obvious gingival migration. CONCLUSIONS: The use of human mineralized bone may have significant potential to reconstruct missing bone resulting from tooth extraction and to preserve bone after tooth extraction. In addition, healed bone graft sites seem to be able to support immediate placement of a provisional crown and implant restorations. CLINICAL IMPLICATIONS: Patients who are having teeth extracted may become candidates for implant restorations when the sites are appropriately grafted to preserve and reconstruct bone volume, thus allowing for more options for reconstructing the missing tooth site.     

A radiographic study of roots in extraction sites.

1) Roots that are overparalleled to the extent that the apices touch do not relapse to the desired upright positions. 2) Roots that are overparalleled, but the apices do not touch, tend to upright but, in so doing, leave space between the crowns. 3) Roots that are underparalleled at the completion of active treatment tend to maintain their positions or diverge even farther. 4) The best postretention results were cases in which roots and crowns were positioned in normal, upright parallel positions. Slight spaced remaining in these situations appeared to close evenly.     

Differential effects of bone graft substitutes on regeneration of bone marrow

Background: This study used a rat tibial marrow ablation model to test the hypothesis that bone remodeling within the medullary canal varies with bone graft materials of different chemical compositions and structural properties, impacting marrow cavity restoration. Bone graft materials were selected based on their relative resorption or degradation in vivo and their osteogenic properties. Methods: Following ablation of the right tibial marrow in male Sabra‐strain rats, materials were implanted in the proximal marrow cavity: poly‐d,l ‐lactide‐co‐glycolide 75 : 25 (PLGA); coralline‐hydroxyapatite (HA), calcium‐sulfate (CaSO4), collagen–HA–tricalcium phosphate granules, anorganic bovine bone mineral, demineralized bone matrix (DBM), 45S5 Bioglass (BG), PLGA with BG 50 : 50, PLGA : BG 80 : 20, and PLGA and PLGA:BG 50 : 50 plus bone marrow (BM). Control tibias were ablated but received no implants. At 2 (endosteal bone healing), 4 (marrow cavity remodeling) and 8 weeks (marrow restoration), six to eight animals per group were euthanized and tibias processed for histomorphometry of proximal and distal medullary canals. Results: Control tibias showed primary bone in proximal and distal medullary canals at 2 weeks, with trabeculae surrounded by cellular marrow. At 4 and 8 weeks, control trabeculae were thinned and marrow had more fat cells. In the treated tibias, trabecular bone volume (TBV) varied with time and was material specific. Most implants supported comparable TBV at 2 weeks. Sites with CaSO4 or DBM exhibited decreased TBV with time whereas trabecular bone was retained in proximal tibias containing other materials, closely juxtaposed to the implants. TBV did not always correlate directly with implant volume, but changes in BM volume were correlated inversely with TBV. Addition of BM increased marrow restoration in sites containing PLGA; however, BM reduced restoration of marrow when added to PLGA : BG. Although the presence of implants in the proximal tibia resulted in retention of trabecular bone, there was a time‐dependent reduction in TBV in distal canals; the rate and extent of the distal TBV reduction were implant dependent. Conclusions: Thus, although many materials can support bone formation in the marrow cavity, bone quality, quantity, and physical relationship to the implant, and its rate of resorption differ in a material‐dependent manner, resulting in differences in the restoration of marrow. Clinical relevance: Bone graft materials should be selected not only for their ability to support new bone formation but also for their impact on the remodeling phase of bone healing.     

不同骨移植材料应用于犬拔牙位点保存的实验研究

目的 探究不同比例松质骨、皮质骨混合的同种异体骨、去蛋白牛骨矿物质(DBBM)在位点保存中的牙槽嵴保存效果及对种植体骨结合的影响.方法 拔除两只比格犬双侧第二、三、四前磨牙,12个牙位,随机分为A、B、C、D 4组.A组空白组;B、C、D 3组分别填塞松质骨:皮质骨:脱钙骨基质(DBM)质量比分别为0:9:1和3:6:1的同种异体骨1、同种异体骨2和DBBM.位点保存术后3个月在每个牙位的远中根牙槽窝中央环钻取柱状骨,植入种植体.比较位点保存术后3、6个月拔牙窝高度和宽度的变化.通过组织学分析柱状骨标本的新生骨、剩余材料和结缔组织及其他成分的比例.种植体植入3个月后通过Van?Gieson染色,观察种植体周围骨结合.结果 术后3、6个月各组的颊侧牙槽嵴高度、宽度均降低,经方差分析4组间差异有统计学意义(P<0.05),组间两两比较,A组与其他3组相比差异有统计学意义(P<0.05).位点保存术后3个月,各组新生骨比例差异无统计学意义.A组的种植体骨结合率小于B、C、D组(P<0.05),其余3组间差异无统计学意义.结论 在比格犬的拔牙位点保存术中使用同种异体骨和DBBM均有保存牙槽嵴形态的作用,也对后期种植体骨结合有积极作用.     

Connective tissue growth factor expressed in rat alveolar bone regeneration sites after tooth extraction

OBJECTIVE: To understand bone regeneration process after tooth extraction could be a clue to develop a new strategy for alveolar bone reconstruction. Recently, accumulated evidences support that connective tissue growth factor (CTGF) is implicated in tissue repair of many tissues. In this study, we investigated the spatial and temporal expression of CTGF in the rat tooth extraction sockets. DESIGN: Five weeks old wild type male rats (weighing 120 g) were used for this experiment. Expression of CTGF was determined by immunohistochemistry and in situ hybridization in the rat upper molar tooth extraction sockets at 2, 4, 7, 10 and 14 days after tooth extraction. RESULTS: CTGF was expressed strongly in the endothelial cells migrating into the granulation tissue at the bottom of the sockets during 4 days after tooth extraction. During the reparative process, no apparent chondrocyte-like cell appeared in the sockets, while osteoblast-like cells proliferated in the sockets with low CTGF expression at 7, 10, 14 days after extraction. As expected, no staining was observed with the preimmune rabbit IgG and CTGF sense probe. CTGF may play an important role in angiogenesis and granulation tissue formation specifically at early healing stage after tooth extraction to initiate alveolar bone repair. CONCLUSION: CTGF was expressed at early healing stage of the rat tooth extraction wound.     

Effects of platelet-rich plasma on bone healing in combination with autogenous bone and bone substitutes in critical-size defects. An animal experiment

OBJECTIVES: An animal study was carried out to investigate the influence of platelet-rich plasma (PRP) on the regeneration of bony defects. MATERIAL AND METHODS: Critical-size defects in the forehead region of a mini-pig were filled with randomly distributed combinations of autogenous bone, tricalcium-phosphate granules (CeraSorb), bovine spongious blocks (BioOss) and a bovine bone inducing collagenous sponge (Colloss) with and without PRP in two preparations (Cusasan, 3i). The animals were killed after 2, 4 and 12 weeks. The specimens were evaluated microradiographically and immunohistologically. RESULTS: Autologous bone (38 +/- 9.9%) and Colloss (52.6 +/- 4.0%) showed the highest remineralization rates at 2 weeks. The initial high expression of BMP-2 in the Colloss-group gives evidence of an early initiation of bony regeneration. At 2 weeks PRP ad modum 3i was able to enhance bone healing significantly (P=0.028) only when applied in combination with autogenous bone (62.8 +/- 1.6%). Four weeks after surgery, both PRP preparations did no longer increase bony regeneration in the autogenous groups. The osteoconductive effect of Bio-Oss (38.7 +/- 5.5%) and CeraSorb (41+/-4.9%) was remarkable as well 4 weeks after surgery. Nevertheless, the addition of PRP hardly influenced bony regeneration, ceramic degradation or cytokine expression when bone substitutes were applied. At 12 weeks, the level of reossification had adjusted similarly in all groups. CONCLUSION: PRP did not add additional benefit when xenogenic bone substitutes were used. However, a significant effect on bone regeneration was found in the autogenous group initially when PRP is added.     

Correction of alveolar cleft with calcium-based bone substitutes

The criterion standard of alveolar cleft repair is iliac crest bone graft before secondary canine eruption. Tooth eruption has never been shown to occur in synthetic bone substitute, and there is no ideal autologous bone graft for primary repair. This prospective study evaluated alveolar cleft grafting with a calcium substitute before primary canine eruption. Ten consecutive patients with complete cleft lip, palate, and unilateral alveolar cleft with reasonably aligned arches were grafted beginning in January 2003 to March 2007. Mean age at surgery was 10.4 months. Follow-up ranged from 3 to 7 years. Radiologic evaluation of alveolar ridge was performed at the age of 4.All 10 patients were operated on by the same surgeon using the same technique, that is, conservative elevation of nasal, oral, and anterior alveolar mucosal flaps around the cleft, closure of nasal and oral flaps, placement of 1 to 3 mL of calcium substitute paste or crystals in the pocket, and closure of the anterior alveolar mucosa. All 10 patients healed without complication. Clinical evaluation revealed a well-healed arch with primary canine growth in the area of the previous cleft. Adequate normal bone formation and often a descending secondary canine were radiologically confirmed. Calcium substitutes offer significant advantages over other biomaterials as well as autologous bone grafts particularly in the primary alveolar cleft reconstruction. Our study has shown for the first time that teeth can erupt through this material, which turns into a normal functioning bone in the alveolar ridge.     

Finite element analysis of different bone substitutes in the bone defects around dental implants

PURPOSE: To evaluate the distribution of stress and strain for the evaluation of implant and graft stability at each stage before stabilization of the graft is achieved after implantation was performed. MATERIALS AND METHODS: Dembone (Pacific Coast Tissue Bank, Los Angeles, CA), Bio-Oss (Geistlich Pharma, Wolhusen, Switzerland), particulate dentin, and plaster of Paris were used to fill bone defects. The distribution of stress was compared in the mandible and maxilla, between vertical load and load applied at 30 degrees angle, and according to time, with 3 different graft materials. RESULTS: Stress occurred more when it was applied at an angle, rather than applied vertically. Stress was relatively high immediately after implantation, and particulate dentin-plaster of Paris showed larger mechanical properties and lower stress distribution overall. The largest stress distribution was shown when stress was applied at an angle when demineralized freeze-dried bone was used. The pattern of stress distribution was different according to differences in the mechanical properties of implants. CONCLUSION: Caution is needed not to apply stress at an angle immediately after implantation. Differences of stress were reduced with time as the implant became stabilized.