Comparative study of the osseous healing process following three different techniques of bone augmentation in the mandible: an experimental study

The aim of this study was to evaluate the osseointegration of three different bone grafting techniques. Forty-eight mature New Zealand rabbits were divided randomly into three groups of 16 each. Horizontal augmentation was performed on the corpus of the mandible using three different techniques: free bone graft (FBG), free periosteal bone graft (PBG), pedicled bone flap (BF). The animals were sacrificed at postoperative weeks 1, 3, or 8. Specimens were decalcified for histological examination, and histomorphometric measurements were performed. The histological evaluation demonstrated bony fusion between the grafts and the augmented mandibular bone after 8 weeks in all groups. At week 8, the bone volume was significantly greater in the BF group than in the FBG (P < 0.001) and PBG (P = 0.001) groups, and also the trabecular thickness was significantly greater than in the FBG (P = 0.015) and PBG (P = 0.015) groups. Trabecular separation was significantly lower in the BF group than in the FBG group at week 8 (P = 0.015). BF demonstrated greater osseous healing capacity compared to FBG and PBG. The preserved vascularization in BF improves the bone quality in mandibular bone augmentations.     

Measurement of ridge alterations following tooth removal: a radiographic study in humans

Objective: The aim of this study was a radiographic mesiodistal analysis of the shape of the bone crest 3 months after tooth removal. Material and methods: One hundred single tooth extractions were performed on 100 patients because of orthodontic or prosthetic causes. Bite blocks were used for two radiographs: one on the day of extraction and the other after healing of the socket, 3 months later. These X‐rays were used to determine: (1) the most apical distance of alveolar ridge resorption, with baseline as the line between bone‐to‐teeth contact (the greatest distance in bone resorption height) and (2) the mesiodistal distance (MDD) and mesial and distal angles arising after bone tissue modeling. Results: Significant differences (P<0.05) emerged between the MDDs of multiple‐ [8 mm, 95% confidence interval (CI): 6.09, 9.90] and single‐root teeth (5.60 mm, 95% CI: 4.80, 6.50). However, mesial or distal angles or the most apical distance of alveolar ridge resorption did not differ (mean distance in height=4.32 mm, 95% CI: 3.85, 4.78; mean angle=24°). Conclusions: In this study, the post‐extraction mesiodistal bone distance between teeth adjacent to the edentulous ridge depends on the size of the edentulous space. Nevertheless, the distance does not affect the distance in bone loss height. The distance of bone resorption height reaches a balance at the midpoint, which we consider indicative of stable healing. This resorption process must be considered when placing dental implants in fresh extraction sockets, especially in aesthetic sites, because the implant surfaces could be exposed after 3 months. To cite this article:
Moya‐Villaescusa MJ, Sánchez‐Pérez A. Measurement of ridge alterations following tooth removal: a radiographic study in humans.
Clin. Oral Impl. Res. 21 , 2010; 237–242.
doi: 10.1111/j.1600‐0501.2009.01831.x     

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.     

Surgical intervention in enchondral and membranous bone: intraindividual comparisons in the rabbit

Background: The long bones, which are of enchondral origin, are often used in histologic evaluations of dental implants that clinically will be placed in bones of membranous origin. Purpose: The aim of this investigation was to study the effect of surgical trauma by multiple drill perforations on both enchondral and membranous bone—the tibial and maxillary bone architecture—8 weeks after surgery. Materials and Methods: In eight rabbits the medial metaphyses of both tibiae and the edentulous ridges of both sides in the maxilla were surgically exposed. On the test sides, 25 to 30 holes were drilled through the cortical plate and 5 mm into the medullary space. The contralateral sides underwent no treatment and served as controls. Eight weeks later the animals were killed to obtain transverse ground sections for histomorphometry. A paired analysis of the bone densities of the tibiae and the jaw specimens was made. Results: In general the morphologic appearances of the test and control tibiae were similar. In the control group the anatomy of the medullary space appeared normal, with few bone trabeculae and with abundant marrow tissue. In the test group, areas of resorption were evident on the cortical bone plate that had been perforated 8 weeks previously; also evident were ingrowths of marrow tissue and bone formation. In a few specimens some newly formed bone trabeculae were found in the medullary space, both contiguous to the perforated cortical bone plate and as small islets in the marrow tissue. The mean test and control site values for each parameter were similar, and no statistically significant differences were found. In the maxilla, the bone architecture had altered substantially by way of an increase in the proportion of trabecular bone and a decrease in the proportion of cortical bone. Drilling appeared to have little effect on tibial bone density, which did not significantly differ between test and control sites. Maxillary bone density, however, was significantly greater at the test sites than at the control sites. Comparisons of bone density between tibia and jaw specimens revealed no significant differences either between test sides or between control sides. Thus, the same magnitude of surgical trauma that altered the bone architecture and density of the rabbit maxilla was not found to have altered those of the tibia in the same animal 8 weeks after surgery. The reasons for the differences are discussed in this article. Conclusions: As observed 8 weeks post surgery, multiple drill perforations were not found to cause significant alterations in the metaphysis of the tibia whereas a considerable change in bone architecture and an increase in bone density were found in the maxilla. Whether this depends on different embryologic origins or reflects morphologic and functional differences in the mature bone demands further study.     

Recent outcomes and perspectives of the application of bone morphogenetic proteins in implant dentistry

Background: Since the discovery of bone morphogenetic proteins (BMPs), the number of related studies has increased substantially, and more recent outcomes have cast encouraging perspectives on their use in reconstructive surgery. Purpose: The aim of the present review was to summarize the present knowledge about the use of BMPs in conjunction with dental implants based on the literature. Materials and Methods: Scientific articles dealing with the use of growth factors and bone healing with or without dental implants were searched for on MEDLINE and critically scrutinized. Results: Thirty‐nine scientific reports formed the base for the present review. Whereas the osteoinductive capability of BMPs is well documented, studies on their effects in implant dentistry are still incipient. Preclinical and clinical studies did not show outstandingly good outcomes of the application of BMPs compared with conventional treatments or controls. Conclusions: The number of studies in the field of dental implantology in which BMPs have been used is still too small for establishing clinical protocols of their use in order to improve a recipient bone bed prior to implant placement or to enhance the integration process of an implant.     

固定方式对下颌升支矢状截骨术骨愈合影响的实验动物研究

目的：比较不同固定方式对下颌升支矢状截骨术术后骨创愈合情况的影响。方法16只成年犬随机分成4组,各组均行改良的双侧下颌升支矢状截骨术,分别采用4种骨段固定形式：①钢丝结扎固定;②小夹板固定;③双皮质螺钉固定;④夹板及钢丝联合固定。术后6周、12周分别处死每组动物2只,完整取出下颌骨,HE染色,镜下观察骨组织愈合情况。结果：各组均可见颊舌侧皮质骨的骨膜下有新骨形成;各组术后6周和12周时组织学表现基本相同;后两组可见直接骨愈合,愈合时无内骨痂形成,截骨线不易辨认,骨髓腔和截骨区充满新骨。结论：固定模式影响了骨段稳定性和应力分布状态,从而影响了截骨创的骨愈合,良好的固定对减少术后远期骨性复发有积极意义。     

Clinical and radiographic evaluation of the efficacy of platelet-rich plasma combined with hydroxyapatite bone graft substitutes in the treatment of intra-bony defects in maxillofacial region

Objective. The aim of this study is to evaluate the efficacy of platelet-rich plasma (PRP) clinically and radiographically when combined with bovine derived hydroxyapatite (HA) bone grafting materials and resorbable collagen membranes for the treatment of intra-bony defects frequently seen at the distal aspect of mandibular second molars following the surgical extraction of fully impacted mandibular wisdom teeth. Study design. Eighteen patients were scheduled for post-operative visits at 1, 3 and 6 months post-operatively, probing depths were measured and digital panoramic radiographs were taken. Results. There were no significant differences on probing depths among two groups. Radiographic assessment also showed no significant difference among groups at 1st and 6th month intervals, while 3 months post-operatively the amount of radiographic density at the PRP side was significantly higher. Conclusion. Combined use of PRP and bovine-derived HA graft materials for the treatment of intra-bony defects might be an appropriate approach when the main goal is providing earlier bone regeneration.     

Platelet releasate increases the proliferation and migration of bone marrow-derived cells cultured under osteogenic conditions

Concentrated platelets and their products are currently being used as a clinical tool to accelerate endosseous wound healing. However, there is little understanding regarding the actions of platelets and platelet-released products on osteogenic cells. We show, herein, that releasate from thrombin-activated platelets increases the migration and proliferation of osteogenic cultures of bone marrow cells. Using a scratch wound assay, we demonstrated that platelet releasate (PR) stimulated up to a 2.4 +/- 0.5-fold increase in wound closure in serum-free medium, relative to a control containing thrombin. In the presence of serum, the addition of PR resulted in a 1.45 +/- 0.13-fold increase in scratch closure. To isolate cell migration from the effects of cell proliferation, cell monolayers were pre-incubated with 5, 10 and 20 microg/ml of Mitomycin C (MMC), which is a potent inhibitor of cell proliferation. This resulted in a large decrease in the leading front of scratch closure, which indicates that PR stimulated cell mitogenesis. However, irrespective of MMC pre-treatment, PR stimulated a motogenic response. These results provide evidence of possible mechanisms by which platelets could influence bone regeneration.     

Effect of calcitonin on alveolar wound healing

The effect of calcitonin (CT) on alveolar wound healing was studied with histomorphometric methods. Wistar rats weighing 80-90 g were submitted to extraction of the three mandibular molars. Half of them were injected intraperitoneally with daily therapeutic doses of CT. The control group received no further treatment. All the rats were killed 14 days after the onset of the experiment. Bone healing was impaired in CT treated animals and involved a more intense bone remodeling activity. Bone resorptive areas were present both on the profiles of the newly formed bone and on the alveolar ridge surface. These results suggest that CT would accelerate the process of bone healing.     

The Influence of PRP on Early Bone Formation in Membrane Protected Defects. A Histological and Histomorphometric Study in the Rabbit Calvaria

Background: Platelet rich plasma (PRP) has been proposed to be a useful adjunct to bone grafting. Purpose: The aim of the present study was to assess new bone formation in bone regeneration procedures using platelet rich plasma (PRP) alone or in combination with autogenous bone. Materials and Methods: Four surgically created, monocortical defects 5 mm in diameter in the calvariae of 15 New Zealand rabbits were grafted with a coagulum‐filled control, PRP, particulated autogenous bone alone (A), or combined with PRP (A‐PRP). Results: Mean platelet concentration of 1,761,930 ± 680,200/µl was achieved (5.30 ± 2.63 × fold of baseline). Animals were sacrificed 1, 2, and 4 weeks later. Histomorphometric analysis showed no statistical difference for total new bone formation at any time point, however, a detailed analysis revealed a statistically significant higher percentage of lamellar bone than woven bone for the autogenous bone group at 2 weeks; all other groups demonstrated equal percentages of either bone type. At 4 weeks, all groups revealed a statistically greater component of lamellar bone over woven bone. Graft resorption rate was similar for both A and A‐PRP. PRP platelet concentration was significantly positively correlated with TGF‐beta1 but not with PDGF‐AB. Conclusions: Within the limits of the chosen animal model, this study demonstrated that PRP during early healing, whether alone or mixed with autogenous bone, did not lead to greater bone remodelling, as compared to coagulum. In contrast, autogenous bone alone demonstrated accelerated bone remodelling at 2 weeks.     

脱钙人牙基质材料在埋伏牙拔牙创中的应用

目的:观察脱钙人牙基质材料在埋伏牙拔除后促进骨组织愈合的临床效果。方法:共40例埋伏牙拔除患者,随机平均分为A、B组:A组拔牙创直接缝合,为空白对照;B组拔牙窝内即刻植入脱钙人牙基质材料。所有患者均在术前摄全口曲面断层片,术后1周、1个月行局部数字牙片检查;结合临床检查进行比较,观察骨腔愈合及骨重建情况。结果:2组患者创口均Ⅰ期愈合。术后1月X线片检查,A组拔牙窝骨密度仍低于周围正常骨,B组拔牙创骨密度已与正常骨接近。结论:采用脱钙人牙基质材料填入拔牙窝内的方法,骨诱导作用明显,能加速骨组织的修复重建,缩短了拔牙创愈合时间。