Effect of a xenograft on early bone formation in extraction sockets: an experimental study in dog

Aim: The aim of this study was to study the effect on early bone formation resulting from the placement of a xenograft in the fresh extraction socket in dogs.
Material and methods: Five beagle dogs were used. The distal roots of the third and fourth mandibular premolars were removed. In one quadrant, a graft consisting of Bio-Oss^® Collagen was placed in the fresh extraction wound, while the corresponding premolar sites in the contra-lateral jaw quadrant were left non-grafted. After 2 weeks of healing, the dogs were perfused with a fixative, the mandibles removed, the experimental sites dissected, demineralized, sectioned in the mesio-distal plane and stained in hematoxyline–eosine.
Results: The central portion of the non-grafted sockets was occupied by a provisional matrix comprised of densely packed connective tissue fibers and mesenchymal cells. Apical and lateral to the provisional matrix, newly formed woven bone was found to occupy most of the sockets. In the apical part of the grafted sockets , no particles of the xenograft could be observed but newly formed bone was present in this portion of the experimental site. In addition, limited numbers of woven bone trabeculae occurred along the lateral socket walls. The central and marginal segments of the grafted sockets, however, were occupied by a non-mineralized connective tissue that enclosed Bio-Oss^® particles that frequently were coated by multinucleated cells.
Conclusions: The placement of Bio-Oss^® Collagen in the fresh extraction wound obviously delayed socket healing. Thus, after 2 weeks of tissue repair, only minute amounts of newly formed bone occurred in the apical and lateral borders of the grafted sockets, while large amounts of woven bone had formed in most parts of the non-grafted sites.     

Healing of extraction sockets and surgically produced - augmented and non-augmented - defects in the alveolar ridge. An experimental study in the dog

OBJECTIVES: The current experiments had three aims (i) to determine whether the absence of the periodontal ligament (PDL) may alter features of the healing of an extraction socket, (ii) to examine if there were differences in the proportion of different tissues in resolved extraction sockets and surgically produced defects after 3 months of healing, (iii) to study the influence of different biomaterials on the healing of surgically produced bone defects. MATERIAL AND METHODS: Extraction sites: In five dogs, the 4th mandibular pre-molars were hemi-sected and the distal roots were removed. The extraction socket of one of the pre-molars was instrumented to eliminate all remnants of the PDL tissue. The socket of the contra-lateral pre-molar was left without instrumentation. The dogs were sacrificed after 3 months of healing. Defect sites: In five dogs, the pre-molars and 1st molars on both sides of the mandible were first removed and 3 months of healing allowed. After this interval three standardized cylindrical defects were prepared in each side of the mandible. The defects were 3.5 mm in diameter and 8 mm deep. In each quadrant one defect was grafted with Bio-Oss Collagen, one with Collagen Sponge and one defect was left non-grafted. The dogs were sacrificed 3 months after the grafting procedure. RESULTS: Extraction sites: The two categories of extraction sockets did not differ with respect to gross morphological features. The tissue of the extraction sites, apical of a newly formed bone bridge, was dominated by bone marrow. Few trabeculae of lamellar bone were also present. Defect sites: The non-augmented defect was sealed by a hard-tissue bridge. In the central and apical portions of the defect bone marrow made up about 61%, and mineralized bone 39% of the tissues. The invagination of the surface of this crestal bone was 0.8+/-0.3 mm. The defect augmented with Collagen Sponge was covered by a hard-tissue bridge 38% of the tissue within the defect was made up of bone marrow while the remaining 62% was occupied by mineralized bone. The invagination of the hard-tissue bridge was on the average 0.6+/-0.1 mm. In defects augmented with Bio-Oss Collagen the biomaterial occupied a substantial portion of the tissue volume. Eighty-five percent of the periphery of the Bio-Oss particles were found to be in direct contact with newly formed mineralized bone. Woven bone and bone marrow made up 47% and 26% of the newly formed tissue. The invagination of the most coronal part of the bone defect was 0.1+/-0.1 mm. CONCLUSION: Sockets that following tooth removal had their PDL tissue removed exhibited similar features of healing after 3 months as sockets which had the PDL retained. The tissues present in an extraction site appeared to be more mature than those present in a surgically produced defect of similar dimension. The Bio-Oss Collagen augmented defect exhibited less wound shrinkage than the non-augmented defect.     

Modeling and remodeling of human extraction sockets

Introduction: The available studies on extraction wound repair in humans are affected by significant limitations and have failed to evaluate tissue alterations occurring in all compartments of the hard tissue defect.
Aim: To monitor during a 6-month period the healing of human extraction sockets and include a semi-quantitative analysis of tissues and cell populations involved in various stages of the processes of modeling/remodeling.
Material and Methods: Twenty-seven biopsies, representative of the early (2–4 weeks, n =10), intermediate (6–8 weeks, n =6), and late phase (12–24 weeks, n =11) of healing, were collected and analysed.
Results: Granulation tissue that was present in comparatively large amounts in the early healing phase of socket healing, was in the interval between the early and intermediate observation phase replaced with provisional matrix and woven bone. The density of vascular structures and macrophages slowly decreased from 2 to 4 weeks over time. The presence of osteoblasts peaked at 6–8 weeks and remained almost stable thereafter; a small number of osteoclasts were present in a few specimens at each observation interval.
Conclusions: The present findings demonstrated that great variability exists in man with respect to hard tissue formation within extraction sockets. Thus, whereas a provisional connective tissue consistently forms within the first weeks of healing, the interval during which mineralized bone is laid down is much less predictable.     

β‐tricalcium phosphate in the early phase of socket healing: an experimental study in the dog

Objectives: The aim of this experiment was to analyze processes involved in the incorporation of β‐tricalcium phospate (TCP) particles in host tissue during healing following tooth extraction and grafting. Material and methods: Five beagle dogs were used. Four premolars in the maxilla (³P³, ²P²) were hemi‐sected, the distal roots were removed and the fresh extraction socket filled with TCP. The tooth extraction and grafting procedures were scheduled in such a way that biopsies representing 1 and 3 days, as well as 1, 2, and 4 weeks of healing could be obtained. Tissue elements such as cells, fibers, vessels, leukocytes and mineralized bone were determined. In deparaffinized sections structures and cells that expressed Tratarate resistant acid phosphate, alkaline phosphatase, and osteopontin were identified by the use of markers. Results: The porosities of the TCP particles were initially filled with erythrocytes that subsequently were replaced with mineralized bone. Some of the graft material was invaded by mesenchymal and inflammatory cells and disintegrated. Thus, small membrane bound granules appeared in the granulation tissue and the provisional matrix. In the process of hard tissue formation, partly mineralized (modified) TCP particles became surrounded by ridges of woven bone. Conclusions: It was demonstrated that the early healing of an extraction socket that had been grafted with β‐TCP involved (i) the formation of a coagulum that was (ii) replaced with granulation tissue and a provisional matrix in which (iii) woven bone could form. In this process the biomaterial was apparently involved. To cite this article:
Araújo MG, Liljenberg B, Lindhe J. β‐tricalcium phosphate in the early phase of socket healing: an experimental study in the dog. Clin. Oral Impl. Res. 21 , 2010; 445–454.
doi: 10.1111/j.1600‐0501.2009.01876.x     

Tissue modeling following implant placement in fresh extraction sockets

OBJECTIVE: To study whether osseointegration once established following implant placement in a fresh extraction socket may be lost as a result of tissue modeling. MATERIAL AND METHODS: Seven beagle dogs were used. The third and fourth premolars in both quadrants of the mandible were used as experimental teeth. Buccal and lingual full-thickness flaps were elevated and distal roots were removed. Implants were installed in the fresh extraction socket. Semi-submerged healing of the implant sites was allowed. In five dogs, the experimental procedure was first performed in the right side of the mandible and 2 months later in the left mandible. These five animals were sacrificed 1 month after the final implant installation. In two dogs, the premolar sites on both sides of the mandible were treated in one surgical session and biopsies were obtained immediately after implant placement. All biopsies were processed for ground sectioning and stained. RESULTS: The void that existed between the implant and the socket walls at surgery was filled at 4 weeks with woven bone that made contact with the SLA surface. In this interval, (i) the buccal and lingual bone walls underwent marked surface resorption and (ii) the height of the thin buccal hard tissue wall was reduced. The process of healing continued, and the buccal bone crest shifted further in the apical direction. After 12 weeks, the buccal crest was located>2 mm apical of the marginal border of the SLA surface. CONCLUSION: The bone-to-implant contact that was established during the early phase of socket healing following implant installation was in part lost when the buccal bone wall underwent continued resorption.     

Dynamics of Bio‐Oss® Collagen incorporation in fresh extraction wounds: an experimental study in the dog

Aim: The objective of this experiment was to analyze processes involved in the incorporation of Bio‐Oss^® Collagen in host tissue during healing following tooth extraction and grafting. Methods: Five beagle dogs were used. Four premolars in the mandible (₃P₃, ₄P₄) were hemi‐sected, the distal roots were removed and the fresh extraction socket filled with Bio‐Oss^® Collagen. The mucosa was mobilized and the extraction site was closed with interrupted sutures. The tooth extraction and grafting procedures were scheduled in such a way that biopsies representing 1 and 3 days, as well as 1, 2 and 4 weeks of healing could be obtained. The dogs were euthanized and perfused with a fixative. Each experimental site, including the distal socket area, was dissected. The sites were decalcified in EDTA, and serial sections representing the central part of the socket were prepared in the mesio‐distal plane and parallel with the long axis of the extraction socket. Sections were stained in hematoxylin and eosin and were used for the overall characteristics of the tissues in the extraction socket. In specimens representing 1, 2 and 4 weeks of healing the various tissue elements were assessed using a morphometric point counting procedure. Tissue elements such as cells, fibers, vessels, leukocytes and mineralized bone were determined. In deparaffinized sections structures and cells positive for tartrate‐resistant acid phosphatase activity (TRAP), alkaline phosphatase and osteopontin were identified. Results: The biomaterial was first trapped in the fibrin network of the coagulum. Neutrophilic leukocytes [polymorphonuclear (PMN) cells] migrated to the surface of the foreign particles. In a second phase the PMN cells were replaced by multinuclear TRAP‐positive cells (osteoclasts). The osteoclasts apparently removed material from the surface of the xenogeneic graft. When after 1–2 weeks the osteoclasts disappeared from the Bio‐Oss^® granules they were followed by osteoblasts that laid down bone mineral in the collagen bundles of the provisional matrix. In this third phase the Bio‐Oss^® particles became osseointegrated. Conclusions: It was demonstrated that the incorporation of Bio‐Oss^® in the tissue that formed in an extraction wound involved a series of different processes. To cite this article:
Araújo MG, Liljenberg B, Lindhe J. Dynamics of Bio‐Oss^® Collagen incorporation in fresh extraction wounds: an experimental study in the dog.
Clin. Oral Impl. Res. 21 , 2010; 55–64.     

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     

Effects of alendronate on bone healing after tooth extraction in rats

Oral Diseases (2010) 16 , 674–685 Objectives: Tooth extraction has been identified as an important risk factor for bisphosphonate‐induced osteonecrosis of the jaw. Therefore, the main goal of this study was to determine the effects of alendronate on healing of the extraction socket and on interdental alveolar bone after tooth extraction in rats. Materials and methods: Animals were injected subcutaneously with vehicle or alendronate for 3–4 weeks before the first mandibular molar was extracted and these treatments were continued during post‐extraction periods of 10, 21, 35 and 70 days. Mandibles were processed to evaluate healing of the extraction socket and adjacent alveolar bone by assessing bone formation, bone resorption and vascularity by histomorphometric techniques. Results: Alendronate decreased new woven bone formation, blood vessel area, perimeter and number in the extraction socket at 10 days postextraction, but not at later time points. Furthermore, alendronate‐treated rats had increased interdental alveolar bone volume and height only at 10 days postextraction. In addition, a 2.5‐fold increase in the percentage of empty osteocyte lacunae was found in alveolar bone of alendronate‐treated rats only at 10 days postextraction. Conclusions: Alendronate transiently decreases bone formation and vascularity in the extraction socket and delays the removal of interdental alveolar bone after tooth extraction in rats.     

De novo alveolar bone formation adjacent to endosseous implants

OBJECTIVE: To describe a model for the investigation of different phases of wound healing that are involved in the process resulting in osseointegration. MATERIAL AND METHODS: The implants used for the study of early healing had a geometry that corresponded to that of a solid screw implant with an SLA surface configuration. A circumferential trough had been prepared within the thread region (intra-osseous portion) that established a geometrically well-defined wound compartment. Twenty Labrador dogs received 160 experimental devices totally to allow the evaluation of healing between 2 h and 12 weeks. Both ground sections and decalcified sections were prepared from different implant sites. RESULTS: The experimental chamber used appeared to be conducive for the study of early phases of bone formation. The ground sections provided an overview of the various phases of soft and hard tissue formation, while the decalcified, thin sections enabled a more detailed study of events involved in bone tissue modeling and remodeling. The initially empty wound chamber became occupied with a coagulum and a granulation tissue that was replaced by a provisional matrix. The process of bone formation started already during the first week. The newly formed bone present at the lateral border of the cut bony bed appeared to be continuous with the parent bone, but woven bone was also found on the SLA surface at a distance from the parent bone. This primary bone that included trabeculae of woven bone was replaced by parallel-fibered and/or lamellar bone and marrow. Between 1 and 2 weeks, the bone tissue immediately lateral to the pitch region, responsible for primary mechanical stability of the device, became resorbed and replaced with newly formed viable bone. Despite this temporary loss of hard tissue contact, the implants remained clinically stable at all times. CONCLUSION: Osseointegration represents a dynamic process both during its establishment and its maintenance. In the establishment phase, there is a delicate interplay between bone resorption in contact regions (between the titanium body and mineralized bone) and bone formation in 'contact- free' areas. During the maintenance phase, osseointegration is secured through continuous remodeling and adaptation to function.     

小型猪拔牙创愈合的组织学研究

目的了解小型猪拔牙窝愈合的基本特征,观察愈合过程中成骨细胞及破骨细胞的分布规律。方法拔除小型猪相邻的两颗前磨牙,分别于拔除后即刻、4、7、14、30及60天处死动物,获取标本后脱钙,制作组织切片,HE染色,光镜观察不同时间点的拔牙窝组织学变化。采用Image-ProAnalyzer 7.0图像分析系统对颊、舌侧骨板的成骨、破骨细胞进行计数分析。结果拔牙后第4天拔牙窝底部可见较多的破骨细胞;拔牙后第7天骨板内外侧已经有类骨质形成,破骨细胞向方迁移;拔牙后第14天成骨活动十分活跃,仅舌侧骨板还可观察到少量破骨细胞;拔牙后30天拔牙窝内已充满板层骨,哈弗氏系统丰富;60天后拔牙窝内组织学形态接近正常牙槽骨。结论小型猪拔牙窝愈合过程中组织学特征与人类及其它种属相似,但愈合速度更接近人类,小型猪是研究拔牙窝愈合及牙槽突改建较理想的动物模型。     

Dimensional ridge alterations following tooth extraction. An experimental study in the dog

OBJECTIVE: To study dimensional alterations of the alveolar ridge that occurred following tooth extraction as well as processes of bone modelling and remodelling associated with such change. MATERIAL AND METHODS: Twelve mongrel dogs were included in the study. In both quadrants of the mandible incisions were made in the crevice region of the 3rd and 4th premolars. Minute buccal and lingual full thickness flaps were elevated. The four premolars were hemi-sected. The distal roots were removed. The extraction sites were covered with the mobilized gingival tissue. The extractions of the roots and the sacrifice of the dogs were staggered in such a manner that all dogs contributed with sockets representing 1, 2, 4 and 8 weeks of healing. The animals were sacrificed and tissue blocks containing the extraction socket were dissected, decalcified in EDTA, embedded in paraffin and cut in the buccal-lingual plane. The sections were stained in haematoxyline-eosine and examined in the microscope. RESULTS: It was demonstrated that marked dimensional alterations occurred during the first 8 weeks following the extraction of mandibular premolars. Thus, in this interval there was a marked osteoclastic activity resulting in resorption of the crestal region of both the buccal and the lingual bone wall. The reduction of the height of the walls was more pronounced at the buccal than at the lingual aspect of the extraction socket. The height reduction was accompanied by a "horizontal" bone loss that was caused by osteoclasts present in lacunae on the surface of both the buccal and the lingual bone wall. CONCLUSIONS: The resorption of the buccal/lingual walls of the extraction site occurred in two overlapping phases. During phase 1, the bundle bone was resorbed and replaced with woven bone. Since the crest of the buccal bone wall was comprised solely of bundle this modelling resulted in substantial vertical reduction of the buccal crest. Phase 2 included resorption that occurred from the outer surfaces of both bone walls. The reason for this additional bone loss is presently not understood.     

Hyaluronic Acid Improves Bone Formation in Extraction Sockets With Chronic Pathology: A Pilot Study in Dogs

Background: Previous studies on ridge preservation focusing on fresh extraction sockets using graft materials for ridge preservation procedures have reported a delay in the tissue modeling and remodeling phases. The objective of this study is to evaluate the effect of hyaluronic acid (HA) on healing of infected sockets. Methods: Six beagle dogs were used in this study. Both mandibular third premolars were hemisected, and the distal roots were extracted. Subsequently, periodontal and endodontic lesions were induced at the remaining mesial root. After communication of the periodontal lesion, an endodontic periapical lesion was observed at 4 months, and the mesial roots of both the right and left sides were extracted. HA was applied into the socket of the test group, and no treatment was administered to the other group (control group). Three months after extraction of the mesial roots, the dogs were sacrificed, and histologic evaluations were performed. Results: The sockets were filled by mineralized bone (47.80% ± 6.60%) and bone marrow (50.47% ± 6.38%) in the control group, whereas corresponding values were 63.29% ± 9.78% and 34.73% ± 8.97% for the test group, respectively. There was a statistically significant difference between the groups. Reversal lines and a copious lineup of osteoblasts were observed in the middle and apical parts of the sockets in the test group. Conclusion: An infected socket shows delayed healing of the socket wound, and HA, because of its osteoinductive, bacteriostatic, and anti‐inflammatory properties, may improve bone formation and accelerate wound healing in infected sockets.     

局部应用芦荟膏对大鼠拔牙窝早期愈合的影响

目的 研究拔牙窝内填塞芦荟膏对牙槽窝骨愈合的影响,为临床应用提供实验依据.方法 采用20只Wister大鼠,拔除左右上颌第一磨牙,建立拔牙窝动物模型.右侧拔牙窝中放入300g/L的芦荟膏作为实验组,左侧拔牙窝不放置任何药品作为对照组,观察拔牙窝愈合情况.于拔牙后第4、8、15、30、60d分5批处死大鼠,制取拔牙创标本,并行X线检查和扫描电镜观察.结果 X线检查结果显示实验组拔牙窝愈合较快,新骨形成速度及骨密度明显优于对照组.扫描电镜显示实验组拔牙窝愈合速度明显优于对照组,术后30d时,实验组拔牙窝基本愈合,对照组仍可见明显的骨吸收陷窝,直至60d时拔牙窝基本愈合.结论 芦荟膏对大鼠拔牙窝的早期愈合具有促进作用.     

Bone formation in furcation defects

The aim of the present investigation was to study bone formation in an experimentally-produced furcation defect in the dog. 15 foxhound dogs (group A) and 4 large mongrel dogs (group B) were used. The 2nd and 4th mandibular premolars were extracted and the 3rd lower premolars (3P3) were assigned as experimental teeth. "Through and through" furcation defects, about 4 mm high and 3 mm wide, were first produced in the experimental teeth of the dogs in group A. Reconstructive surgery was subsequently performed in group A using a GTR technique. The dogs of group A were scheduled for biopsy 2 weeks (2 dogs), 1 month (2 dogs), 2 months (2 dogs), 4 months (3 dogs), 5 months (3 dogs) and 6 months (3 dogs) after GTR. The dogs in group B (4 animals) represented healthy, untreated pristine furcations and served as positive controls. Biopsies from the 3P3 regions were harvested, embedded in paraffin and prepared for histological analysis. Mesio-distal sections were cut with the microtome set at 7 microm. The sections were stained in hematoxylin and eosin, and Van Gieson. 3 sections, about 50 microm apart, and representing the central portion of the furcation site were selected for histological measurements. In group A, the proportions of various structures in the newly formed bone and marrow were assessed. In addition, the proportions of primary and secondary osteons, and the number of bone multicellular units (BMU)/mm2 mineralized bone tissue were determined. In the pristine furcations (group B), the histological analyses were performed in a corresponding area to that of the healing furcations. The results demonstrated that the process of bone formation in a large "suprabony" furcation defect can be divided into 3 different phases, namely, (i) the formation of a provisional connective tissue, (ii) the development of a primary bone spongiosa (including mainly woven bone), (iii) the replacement of the spongiosa by lamellar bone and bone marrow through processes of modeling and remodeling. The newly-formed trabeculae of woven bone were reinforced by the deposition of parallel-fibered bone and lamellar bone, a finding which substantiates the validity of the concept that woven bone possesses poor weight-bearing properties and, hence, needs to be re-inforced by a more mature type of bone. The modeling of the newly-formed bone resulted in the formation of (i) one large marrow space in the center of the furcation and, in addition, (ii) a smaller bone marrow space in the most coronal portion of the defect. At the end of the study (6 months), the bone marrow occupied a much larger space than in the bone tissue of pristine furcations. It was suggested that the process of modeling or remodeling of bone tissue in the furcation defect was not completed at the end of the study.     

Extraction wound healing in desalivated rats

Wound licking has been shown to promote extraoral wound healing among animals. Although the oral mucosa is bathed in saliva. Little information about the role of saliva in oral wound healing is found. The present study evaluates the healing of extraction wounds in desalivated rats. Experimental rats underwent sialadenectomy of the submandibular and sublingual glands and ligation of the parotid ducts. Maxillary left first molars were extracted. Rats were killed at 0, 1, 3, 5, 7, 10, 14, and 21 days after surgery and maxillae were prepared for light microscopy examination. Generally, a delay in socket healing in the desalivated rats was found. No differences were observed in blood clot formation. Replacement of the clot by granulation tissue was relatively slow concomitant with a longer inflammatory process. Bone formation kinetics were slower among the experimental rats.     

Clinical Evaluation of Use of Platelet Rich Plasma in Bone Healing

Background

Tooth extraction is performed for a wide variety of reasons as we know. Several techniques aiming at enhancing the regeneration process in the extraction socket have been adopted such as filling the socket with autogenous bone grafts or bone substitutes. We know platelets play a central role in hemostasis and healing processes but relative contradictory effect of platelet in bone regenerating capacity have been published in different in vitro and in vivo studies.

Method

To explore this we used platelet-rich plasma (PRP) (autogenous) alone in empty extraction socket of bilateral impacted mandibular third molars. For that we selected five patients having bilateral impacted teeth. Out of two sockets one was used as intervention by filling with PRP and the other was allowed to heal without PRP. All patients were followed for clinical and radiological evaluation by using digital OPG view after 1 week, 1, 2 and 4 months period.

Result and conclusion

PRP enhanced the osteogenic response in initial bone healing at 1 month duration but there was no added benefit in late bone healing at 4 months period compared in both intervention and control groups. However PRP significantly improved the soft tissue healing in PRP treated sites compared to control group.     

C57BL/6小鼠上颌第一磨牙拔牙创愈合过程观察分析

目的    建立C57BL/6雌性小鼠拔牙创模型,观察第一磨牙拔除后的愈合过程。方法    采用自制器械拔除小鼠上颌第一磨牙,应用体式显微镜、Micro-CT及HE染色等方法观察并记录拔牙后1、3、7、10、14、21、28、35 d共8个时间点拔牙创软组织及骨组织的愈合情况。结果    小鼠拔牙后14 d拔牙窝表面软组织完全愈合;拔牙后7 d拔牙窝底部出现新生骨质,14 d时牙槽窝被新生骨质充填满,21 ~ 28 d时拔牙窝新生骨质继续改建,骨密度显著增加,35 d时新生骨质完成重塑改建。结论    本研究详细阐明了正常小鼠上颌第一磨牙拔牙创愈合过程的阶段特性及时间,为利用小鼠拔牙创构建各种疾病模型的研究提供了详尽的参考。     

Ridge alterations following tooth extraction with and without flap elevation: an experimental study in the dog

Background: Different approaches were advocated to preserve or improve the dimension and contour of the ridge following tooth extraction. In some of studies, socket 'flapless extraction' apparently had a successful outcome.
Aim: The objective of the present experiment was to compare hard tissue healing following tooth extraction with or without the prior elevation of mucosal full-thickness flaps.
Material and methods: Five mongrel dogs were used. The two second mandibular premolars (₂P₂) were hemi-sected. The mesial roots were retained. By random selection the distal root in one side was removed after the elevation of full-thickness flaps while on the contralateral side, root extraction was performed in a flapless procedure. The soft tissue wound was closed with interrupted sutures. After 6 months of healing, the dogs were euthanized and biopsies were sampled. From each experimental site, four ground sections – two from the mesial root and two from the healed socket – were prepared, stained and examined in the microscope.
Results: The data showed that the removal of a single tooth (root) during healing caused a marked change in the edentulous ridge. In the apical and middle portions of the socket site minor dimensional alterations occurred while in the coronal portion of the ridge the reduction of the hard tissue volume was substantial. Similar amounts of hard tissue loss occurred during healing irrespective of the procedure used to remove the tooth was, i.e. flapless or following flap elevation.
Conclusion: Tooth loss (extraction) resulted in marked alterations of the ridge. The size of the alveolar process was reduced. The procedure used for tooth extraction – flapless or following flap elevation – apparently did not influence the more long-term outcome of healing.     

Lack of influence of the Schneiderian membrane in forming new bone apical to implants simultaneously installed with sinus floor elevation: an experimental study in monkeys

Aim: To describe the early healing processes around the implants installed after elevation of the sinus mucosa applying the lateral access technique without the use of grafting material. Material and methods: Immediately after the elevation of the maxillary sinus Schneiderian membrane by the lateral approach in eight monkeys, implants were installed without the use of grafting material. The healing of the tissue around the implants was evaluated after 4, 10, 20 and 30 days. Ground sections were prepared and analyzed histologically. Results: After 4 days of healing, the formation of coagulum and provisional matrix was documented within the elevated area. At 10‐day interval, sprouts of woven bone were in continuity with the parent bone, and partly in contact with the implant surface at the base of the augmented area. While bone‐to‐implant contact increased after 20 and 30 days, the area underneath the Schneiderian membrane appeared reduced in volume and condensed toward the apex of the implants. The sinus mucosa was to some extent collapsed onto the implant surface and on the newly formed bone. Conclusions: The void initially occupied by the coagulum after sinus membrane elevation shrank substantially during the observation period. A lack of influence of the Schneiderian membrane in bone formation apical to implants was documented in the early phase of healing. To cite this article:
Scala A, Botticelli D, Faeda RS, Rangel IG Jr, de Oliveira, JA, Lang NP. Lack of influence of the Schneiderian membrane in forming new bone apical to implants simultaneously installed with sinus floor elevation: an experimental study in monkeys.
Clin. Oral Impl. Res. 23 , 2012; 175–181.
doi: 10.1111/j.1600‐0501.2011.02227.x     

Ridge preservation following tooth extraction using a polylactide and polyglycolide sponge as space filler: a clinical and histological study in humans

BACKGROUND: The placement of different graft materials and/or the use of occlusive membranes to cover the extraction socket entrance are techniques aimed at preserving/reducing alveolar ridge resorption. The use of grafting materials in fresh extraction sockets has, however, been questioned because particles of the grafted material have been found in alveolar sockets 6-9 months following their insertion. AIM: The aims of the study were to (i). evaluate whether alveolar ridge resorption following tooth extraction could be prevented or reduced by the application of a bioabsorbable polylactide-polyglycolide sponge used as a space filler, compared to natural healing by clot formation, and (ii). evaluate histologically the amount and quality of bone tissue formed in the sockets, 6 months after the use of the bioabsorbable material. MATERIAL AND METHODS: Thirty-six patients, undergoing periodontal therapy, participated in this study. All patients were scheduled for extraction of one or more compromised teeth. Following elevation of full-thickness flaps and extraction of teeth, measurements were taken to evaluate the distance between three landmarks (mesio-buccal, mid-buccal, disto-buccal) on individually prefabricated stents, and the alveolar crest. Twenty-six alveolar sockets (test) were filled with a bioabsorbable polylactide-polyglycolide acid sponge (Fisiograft), while 13 sockets (controls) were allowed to heal without any filling material. The flaps were sutured with no attempt to achieve primary closure of the surgical wound. Re-entry for implant surgery was performed 6 months following the extractions. Thirteen biopsies (10 test and three control sites) were harvested from the sites scheduled for implant placement. RESULTS: The clinical measurements at 6 months revealed, in the mesial-buccal site, a loss of bone height of 0.2 mm (1.4 SD) in the test and 0.6 mm (1.1 SD) in the controls; in the mid-buccal portion a gain of 1.3 mm (1.9 SD) in the test and a loss of 0.8 mm (1.6 SD) in the controls; and in the distal portion a loss of 0.1 mm (1.1 SD) in the test and of 0.8 (1.5 SD) mm in the controls. The biopsies harvested from the test sites revealed that the new bone formed at 6 months was mineralized, mature and well structured. Particles of the grafted material could not be identified in any of the 10 test biopsies. The bone formed in the control sites was also mature and well structured. CONCLUSION: The results of this study indicate that alveolar bone resorption following tooth extraction may be prevented or reduced by the use of a bioabsorbable synthetic sponge of polylactide-polyglycolide acid. The quality of bone formed seemed to be optimal for dental implant insertion.