Surface Morphology of Superficial Cells in Irradiated Oral Mucosa: An Experimental Study in Beagle Dog

Abstract

Objectives: The aim of the present study is to investigate if radiation induces changes in the superficial cells of the oral mucosa and secondly to describe morphological characteristics of the cell surface structure by scanning electron microscopy (SEM).

Materials and methods: Ten beagle dogs aged 1–2 years were used in this study. One side of each mandible was irradiated in two sessions, each lasting 1 week. The total dosage was 40?Gy (Group A; 5 dogs) and 50?Gy (Group B; 5 dogs), in five fractions of 4?Gy. The other side of mandible (non-irradiated) served as a control. The specimen was harvested with a scalpel from the alveolar mucosa of the irradiated area 1 year after irradiation and studied with SEM.

Results: In the control side, the surface structure of the cell contains straight parallel or branched microplicae (MPL), which were equally spaced over the cell surfaces. Discontinuous and short MPL were typical cell structure of irradiated mucosa. In 50?Gy group, the surface structure of epithelial cell was pitted and the cell boundaries were thick.

Conclusions: The novelty of the present study is that radiation disrupts superficial cells of the oral mucosa. The role of the MPL structure of the superficial cells in mucositis development is discussed.     

Acid-etching technique of non-decalcified bone samples for visualizing osteocyte-lacuno-canalicular network using scanning electron microscope

The aim of this study was to define the acid-etching technique for bone samples embedded in polymethyl metacrylate (PMMA) in order to visualize the osteocyte lacuno-canalicular network (LCN) for scanning electron microscopy (SEM). Human jaw bone tissue samples (N = 18) were collected from the study population consisting of patients having received dental implant surgery. After collection, the bone samples were fixed in 70% ethanol and non-decalcified samples embedded routinely into polymethyl metacrylate (PMMA). The PMMA embedded specimens were acid-etched in either 9 or 37% phosphoric acid (PA) and prepared for SEM for further analysis. PMMA embedded bone specimens acid-etched by 9% PA concentration accomplishes the most informative and favorable visualization of the LCN to be observed by SEM. Etching of PMMA embedded specimens is recommendable to start with 30 s or 40 s etching duration in order to find the proper etching duration for the samples examined. Visualizing osteocytes and LCN provides a tool to study bone structure that reflects changes in bone metabolism and diseases related to bone tissue. By proper etching protocol of non-decalcified and using scanning electron microscope it is possible to visualize the morphology of osteocytes and the network supporting vitality of bone tissue.     

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.     

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.     

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。     

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.     

脱细胞异体真皮组织补片在智齿拔除中的应用

背景：使用J-1型脱细胞异体真皮组织补片覆盖拔牙创口的报告较少。 目的：探讨异体脱细胞组织补片置入拔牙窝对预防拔牙后并发症的影响。 方法：将400例阻生智齿拔除患者随机分为2组,实验组智齿拔除后拔牙窝内放置医用组织补片;对照组智齿拔除后不放置医用组织补片。分别观察拔牙后组织补片脱落率、肿胀发生率、拔牙窝内血凝块存留和食物残渣残留情况、牙龈是否红肿、对拔牙后出血的影响以及干槽症的发生率。 结果与结论：拔牙后出血的百分比,血凝块留存率,拔牙窝内食物残渣残留百分比,干槽症发生率实验组均明显低于对照组。放置组织补片对术后肿胀和牙龈红肿无明显影响。所有放置在拔牙窝内的组织补片与拔牙创周围组织附着紧密,未见脱落。     

Single Nucleotide Polymorphisms in HIF-1α Gene and Residual Ridge Resorption (RRR) of Mandible in Korean Population

Tooth extraction is a routine surgical procedure in dental treatment. As a wound healing process after tooth extraction, a saddle-shaped residual ridge forms due to bone formation in the extraction socket and localized bone resorption on the external surface of the jawbone. The residual ridge is subjected to continuous bone resorption with substantial differences among individuals. In some cases, it results in excessive bone atrophy, which complicates dental restorative treatment. This unique oral wound healing process may be influenced by factors that are specific to oral tissue. HIF expression is different in oral wound healing compared to that of skin wounds. The objective of this study was to examine a genetic association between SNP of the HIF-1α gene, which is known to have high genetic diversity, and the residual ridge resorption (RRR). Two hundred and two Korean subjects (70.80 ± 9.40 years) with partially or completely edentulous mandible were recruited, and edentulous mandibular bone height was measured following the protocol of the American College of Prosthodontists. The HIF-1α allele was directly sequenced in 24 subjects resulting in the variants over 5% frequency in 95% likelihood, whereas tag-SNPs were selected to perform analysis for the remaining population. Student’s t-test and ANOVA were used for statistical analysis to examine the association between the SNPs and the RRR. Four novel variants were discovered, and a minor allele of rs11549467 was associated with the RRR of the subjects (p = 0.028). rs11549467 increases HIF-1α transactivity, enhancing angiogenesis and increasing new vessel formation. Thus, rs11549467 may play an important role in the disturbed bone remodeling balance resulting in RRR. Results of this study may be useful in developing novel genetic diagnostic tests and identifying Koreans susceptible to developing excessive jawbone atrophy after dental extraction. Most importantly, early screening using genetic information will rescue susceptible patients from the vulnerable situation of excessive jawbone atrophy where no effective prosthetic treatment is available.Key words: Single nucleotide polymorphism (SNP), HIF-1α, Residual ridge resorption (RRR), Edentulous mandible, Atrophy     

Morphological Features of Peri-Implant Tissue after Placement of Dental Implants into the Extraction Socket

In experiments on pigs, bone regeneration was studied after implantation of implants with four cylindrical roots and support cone and laminar crest-shaped implants with shape memory effect. The implants were placed to the extraction socket (mandibular canine) and through the socket immediately after tooth extraction using osteoplastic material or without using collapan-L. The use of collapan-L accelerated regeneration of peri-implant tissue and provided stable fixation of dental construct in the bone over 3 months after surgery, which can be relevant for determining timing of prosthodontic therapy and constructional features of prosthesis.     

Freeze-dried and irradiated allograft bone combined with fresh autologous coagula promotes angiogenesis in an ectopic bone allograft implantation model

Background: Freeze-dried and irradiated allograft bone (FIAB) is more easily impacted than fresh-frozen allograft bone (FAB), but has weaker incorporation efficiency. We combined FIAB with fresh autologous coagula to enhance donor-host incorporation after impaction during hip revision. Methods: Thirty adult male Sprague–Dawley (SD) rats were sacrificed for bone allograft harvesting, and nine male rats were subjected to ectopic bone allograft implantation. For each rat, the container on the left (study) side was filled with freeze-dried allograft bone powder and fresh autologous blood coagula, whereas the right (control) side was filled with freeze-dried allograft bone powder and physiological saline. The extent of angiogenesis (VEGFα) was investigated at postoperative weeks 1, 4, and 8. The deformability of the material was evaluated by performing a confined-impaction mechanical test. Results: At postoperative weeks 4 and 8, angiogenesis within FIAB on the left side was more pronounced than that on the right side. At postoperative week 1, the left side showed significantly higher VEGFα expression than that on the right side. The delta ratios of compression of the allografts were found to be influenced by bone height and impaction frequency, but not by stiffness or elastic modulus (EM). Conclusion: Supplementation with fresh autologous coagula promoted angiogenesis within the FIABs. Moreover, FIABs were equivalent to FABs in terms of deformability.     

Development of Swellable Local Implants of a Polyethyleneimine-Poly(Vinyl Pyrrolidone) (PEI-PVP) Hydrogel as a Socket Filler

Abstract

In this study, hydrogels composed of polyethyleneimine (PEI) and poly(vinyl pyrrolidone) K90 (PVP) cross-linked with various concentrations (0, 0.125, 0.25 and 0.5%) of glutaraldehyde were evaluated as a hydrogel filler for the local delivery of lidocaine after tooth extraction. The drug-release kinetics, swellability, cytotoxicity and wound healing after tooth extraction of these non-cross-linked and cross-linked PEI–PVP hydrogels were examined in male beagles and compared to values using Spongostan^®. Results demonstrated that the extent of cross-linking influenced the swelling of the resulting hydrogel, but the drug-release rates were similar. No significant changes were observed in gingival fibroblasts in contact with the PEI– PVP hydrogels or Spongostan^®. In the in vivo study, PEI–PVP hydrogels showed good retention in the socket for 2 days and showed comparable wound-healing rates within 2 weeks with those of Spongostan^®. In conclusion, PEI–PVP hydrogels are suitable for use as socket-dressing materials, and the release of local anaesthesia from PEI–PVP hydrogels can be sustained for a desirable period of time to prevent pain after a tooth extraction.     

神经支配与拔牙窝的骨愈合*

背景：拔牙窝的新骨形成与骨量保持受体内外多种因素调控,神经系统通过介导成骨细胞和破骨细胞调节骨代谢。 目的：观察神经支配对拔牙窝骨愈合的调节作用,探讨神经支配与拔牙窝骨愈合的相互关系。 方法：切除犬一侧下牙槽神经建立失神经支配动物模型,以未切除侧为对照,拔除失神经支配侧和正常侧前磨牙,放射影像学方法检测术后2,4,8,12周拔牙窝新骨形成和骨量保持。 结果与结论：失神经支配组拔牙窝骨缺损区牙槽嵴高度、宽度和CT值明显低于对照组(P < 0.01);实验组拔牙窝唇颊侧牙槽嵴高度明显低于对照组(P < 0.05或0.01),舌侧牙槽嵴高度差明显高于对照组(P < 0.05或0.01)。提示失下牙槽神经支配影响拔牙窝的新骨形成及骨量保持,二者之间存在密切相关性。     

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 the morphological changes in the mandible for dentate and totally edentate elderly population using cone-beam computed tomography

Purpose

The loss of teeth considerably modifies the mandibular shape. The aim of this study was to compare the morphological changes in the mandible for dentate and totally edentate elderly subjects using cone-beam computed tomography.

Methods

In total, 50 cone-beam computed tomography patients (25 dentate, 25 edentate) without any maxilla-mandibular dysmorphosis were analyzed retrospectively. Panoramic representations of the mandible with superimposed axial slices and cross-sectional slices were developed with the cone-beam computed tomography scans. Values of the mandibular cortical index, bone quality index, gonial angle, antegonial angle, antegonial depth and condyle angle in the left and right side were measured.

Results

There was a significant difference in the mandibular cortical index between the total edentate group and the dentate group in the left side of the mandible (p < 0.001). There was a significant difference in the bone quality index between the total edentate group and the dentate group in the right side and the left side (p < 0.001). There was a significant difference in the bone quality index between the right side and the left side (p < 0.005). When comparing gender, there was only a difference in the right side (p < 0.05).

Conclusions

Our study concluded that the mandibular basal bone morphology changes as a consequence of tooth loss. Cone-beam computed tomography is shown to be a good tool in investigating and achieving these results.     

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。     

Radiation-induced abscopal effect and its enhancement by programmed cell death 1 blockade in the hepatocellular carcinoma: A murine model study

Background/AimsThe abscopal effect, a rare phenomenon induced by radiation, can be reinforced by immunotherapy. Although radiation therapy and immunotherapy are increasingly being utilized for the treatment of hepatocellular carcinoma (HCC), whether immunotherapy could boost the abscopal effect remains unclear. In this study, we aimed to elucidate the immunological mechanisms underlying the abscopal effect induced by the combination of irradiation and immunotherapy in a murine HCC model.MethodsA syngeneic HCC mouse model was established by transplanting murine Hepa 1–6 HCC cells into both hind legs of immunocompetent C57BL/6 mice. The tumors on the right hind legs were irradiated, and abscopal effects were observed in the non-irradiated tumors on the left hind leg with or without the coadministration of anti-programmed cell death 1 (PD-1) antibodies. Flow cytometric analyses were performed to analyze the distributions of immune cells infiltrating both irradiated and non-irradiated tumors and the tumor-draining lymph nodes (TDLNs).ResultsAdministration of 16 Gy in two fractions more effectively inhibited the growth of both irradiated and non-irradiated tumors with higher tumor infiltration of cytotoxic T cells than 8 Gy did in a single fraction. The higher dose also increased activated dendritic cells in TDLNs, which had higher expression of the programmed cell death ligand 1. Coadministration of anti-PD-1 antibodies significantly enhanced the abscopal effect and increased infiltration of activated cytotoxic T cells in both irradiated and non-irradiated tumors.ConclusionsOur findings show that adding anti-PD-1 therapy to radiation enhanced the abscopal effect in a syngeneic murine model of HCC.     

纳米晶胶原人工骨用于新疆维吾尔自治区塔城地区哈萨克族人的牙槽嵴保存

背景：拔牙后牙槽嵴的保存是一个重要的课题。新疆维吾尔自治区塔城地区边疆各县少数民族牙齿拔出后,由于就诊条件、地理条件等限制以及当地居民缺乏口腔保健意识等诸多因素,缺牙区长时间未及时修复导致牙槽嵴条件较差,因此寻找一种适合当地的且更有效的保存剩余牙槽嵴的方法,在当地有着较实用的临床价值。 目的：探索纳米晶胶原人工骨用于新疆维吾尔自治区塔城地区哈萨克族人牙槽嵴保存的可行性。 方法：采用自身配对设计,选取68例新疆维吾尔自治区塔城地区哈萨克族双侧拔牙患者,对就诊的双侧拔牙患者实验侧和对照侧的确定按“不平衡指数最小的分配原则”分组,实验侧拔牙窝植入纳米晶胶原人工骨,对照侧拔牙窝常规处理。植入后即刻及植入后3个月应用螺旋CT对植入区感兴趣区扫描,测量骨密度。 结果与结论：植入后即刻,患者实验侧和对照侧CT图像可见拔牙窝清晰的轮廓,牙槽间隔可见;植入后3个月,患者实验侧和对照侧CT图像显示拔牙窝牙槽间隔影像模糊,CT值与周围牙槽突CT值接近,但实验侧植骨区骨充盈;且植入后3个月患者实验侧骨密度高于对照侧。说明纳米晶胶原人工骨用于新疆维吾尔自治区塔城地区哈萨克族患者牙槽嵴保存的临床效果较好。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

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。     

胎儿牙齿硬组织发育的临床应用解剖

目的：探讨国人胎儿牙齿硬组织发育状况。方法：对正常胎龄10-38周的胎儿上、下颌骨作连续切片,观察乳、恒牙胚及其相关结构发生规律。结果：牙体硬组织形成于14-20周,牙齿的增殖、钙化、萌出同时进行,牙釉质、牙本质厚度随胎龄增长而增加,各乳磨牙牙尖总是近颊尖最先发牛,恒牙板总是位于乳牙胚舌侧。结论：国人牙体硬组织发育成熟较低,牙釉质、牙本质厚度与胎龄呈正相关。