Effects of ovariectomy on trabecular structures of rat alveolar bone

An association between postmenopausal osteoporosis and tooth loss has been proposed. However, histomorphometrical changes in alveolar bone following estrogen deficiency are rarely reported with data on microtrabecular structural changes. To clarify the relationship between estrogen deficiency and tooth loss, we histomorphometrically analyzed the trabecular structural changes of mandibular alveolar bone in ovariectomized rats. Twenty-four adult female Fischer rats were used. Eight rats were sacrificed on day 0 (baseline). The remaining 16 rats were divided into two groups. One group was ovariectomized bilaterally (OVX) and the other group was subjected to sham surgery (Sham). After administration of tetracycline and calcein, the animals were sacrificed 60 days after surgery. Bone histomorphometry, node-strut analysis and measurement of thickness of alveolar bone proper were performed on the interradicular septum of the first molar on the sagittal surface. The trabecular bone volume and trabecular number of the OVX group were significantly lower than those of the baseline and Sham groups. All of the bone resorptive and formative parameters of the OVX group were significantly higher (about one-and-a-half times) than those of the Sham group. Several osteoclasts were seen lining the irregular, eroded surface facing the bone marrow in the OVX group. Furthermore, the OVX group tended to have low microtrabecular stiffness and showed significantly thinner distal alveolar bone proper than in the baseline and Sham groups. In summary, estrogen deficiency caused osteoporotic changes and thin alveolar bone proper in the interradicular septum of rat first molar. This phenomenon might accelerate destruction of alveolar bone and tooth loss, especially in elderly women affected by periodontal disease.     

Characteristic features of trabecular bone in edentulous mandibles

Background: The density and architecture of the alveolar trabecular bone are crucial to the stability of an endosseous implant. A significantly higher implant failure rate can be expected when implants are placed in alveolar bone with reduced density and stability. Therefore, the present study aimed to describe the trabecular bone structure of edentulous mandibles. Method: Two hundred and seventy‐eight bone sections, including the lateral incisor, first premolar, and first molar regions, were obtained from 128 edentulous lower jaws (68 females and 60 males; mean age: 77.58 years). Ground sections were prepared for each region using the ‘sawing and grinding’ technique. The following standard structural histomorphometric parameters were determined using a semiautomatic image analysis: trabecular bone volume, trabecular thickness, trabecular number, trabecular separation, and the trabecular bone pattern factor, which describes the connectedness of cancellous bone structures. Also, the maximum height of the jaw section was determined, to detect any possible correlations between vertical height and histomorphometric parameters. Results: All the histomorphometric parameters examined showed an unexpectedly huge range of variation. The mean trabecular bone volume ranged between 20.9% and 36.9%. The mean trabecular thickness showed values between 165.9 and 224.7 μm. The mean trabecular number ranged between 1.22 and 1.77/ mm, and the mean trabecular separation ranged between 436.7 and 720.0 μm. The mean trabecular bone pattern factor showed values between ?0.05 and ?3.01/ mm. The maximum height of the jaw sections showed values between 16.05 and 23.42 mm. The trabecular bone volume, thickness, number and connectivity were significantly lower in the molar region than in the incisal and premolar regions. Significant sex‐specific differences were found in all the regions, female mandibles showing a smaller amount and lower connectivity of cancellous bone than male mandibles. No correlation could be found between the maximum height of the jaw and the histomorphometric parameters of the cancellous bone. Conclusion: A possible explanation for the difference in the density between the incisal and the molar region may be that molars are generally lost at an earlier age than anterior and premolar teeth. As a result, atrophy‐related resorptive and remodeling processes commence earlier and progress further in this region than in the anterior and premolar regions. Sex‐specific differences are probably due to an increased postmenopausal bone loss of the females.     

实验性骨质疏松症对下颌骨骨折愈合的影响

目的 建立骨质疏松大白兔模型，探讨骨质疏松对下颌骨骨折愈合的影响，为临床提供理论依据。方法 38只3～4月龄雌性新西兰大白兔，随机分为实验组（去势组）及对照组（假手术组）。实验组去除双侧卵巢，对照组只摘除卵巢周围部分脂肪。建模成功后，两组均于双侧颌下角前切迹处行双侧下颌骨骨折，术后2、4、8用处死动物，取骨折处骨痴进行组织学及骨组织形态计量学研究。结果 实验组各时同点的愈合均较对照组慢，骨组织形态计量学比较有显著性差异（P〈0．05）。结论 骨质疏松性骨折的愈合过程较正常骨折愈合慢。愈合后仍处于骨质疏松状态。     

Histological and histomorphometrical changes in rat alveolar bone following antagonistic tooth extraction and/or ovariectomy

OBJECTIVE: To examine changes appearing in the alveolar bone following the removal of the mechanical stress of occlusal loading, as well as the added influence of estrogen deficiency on such changes. DESIGN: The right mandibular molars of female rats were extracted. After 8 weeks, 12 animals were ovariectomized (OVX), and the other 12 were subjected to sham surgery (sham). Four weeks after surgery, all rats were sacrificed. The left-half and right-half maxillas of the sham group (the sham-occluded side and the sham-extruded side, respectively) and right-half maxilla of OVX group (the OVX-extruded side) were examined by histological observation and bone histomorphometry. RESULTS: The vertical height of alveolar bone in the sham-extruded and the OVX-extruded sides increased as compared with that of the sham-occluded side. In both extruded sides, active bone formation occurred on the surface of the alveolar bone facing the periodontal ligament, but the bone marrow was expanded and the bone volume had decreased in the internal area of the alveolar bone. In the OVX-extruded side, the bone marrow expanded more remarkably than that of the sham-extruded side, and the highest percentage of osteoclast surface was detected. CONCLUSIONS: Around the extruded teeth, there were regional differences in bone dynamics between the internal area of the alveolar bone and the bone surface facing the periodontal ligament, and estrogen deficiency seems to have caused further loss of bone volume in the interior of the alveolar bone supporting the extruded tooth.     

鼠哺乳期二(噁)英暴露对子代牙槽骨生长发育的影响

目的 研究鼠哺乳期二(噁)英类物质2,3,7,8-四氯二苯对二(噁)英暴露对大鼠仔鼠牙槽骨生长发育的影响.方法 60天龄2,3,7,8-四氯二苯对二(噁)英暴露组和对照组仔大鼠被处死,将其带有磨牙的上颌骨行树脂包埋,制备硬组织磨片并在荧光显微镜下观察,对两实验组牙槽骨的组织形态、荧光标记情况及组织形态计量学参数进行比较.结果 与对照组相比,二(噁)英暴露组牙槽骨骨小梁结构较为疏松,荧光标记较紊乱.实验组与对照组骨小梁宽度分别为(52.5±5.2)μm及(59.4±6.6)μm,二者差异有统计学意义(P<0.05);骨小梁数目分别为(3.27±0.23)mm-1及(3.75±0.29)mm-1,差异有统计学意义(P<0.01);骨小梁分离度分别为(217.3±37.6)μm及(177.6±33.8)μm,差异有统计学意义(P<0.05);矿化沉积率分别为(0.68±0.08)μm/d及(0.95±0.12)μm/d,差异亦有统计学意义(P<0.05).结论 二(噁)英类物质哺乳期暴露显著降低了大鼠仔鼠牙槽骨的质、量,并影响其空间构型.     

骨质疏松对拔牙创愈合的影响

目的探讨骨质疏松对拔牙创愈合的影响。方法选用40只雌性健康新西兰大白兔(5月龄2～3kg),随机平均分为两组:实验组(切除卵巢并在术后喂以15%低钙饮食)和对照组(切除卵巢周围脂肪组织并在术后喂以正常钙含量饮食)。去卵巢术后2个月对照组和实验组各处死两只动物,通过组织形态学检测显示:与对照组相比,实验组骨小梁纤细,结构稀疏紊乱,成骨细胞和破骨细胞数量均增多,Howship增多,骨陷窝内破骨细胞活跃。所有实验动物于去卵巢后3个月在1%戊巴比妥钠全麻下拔除两侧下颌第一磨牙,拔牙后两组动物饲料全部为正常钙饮食。两组在拔牙术后2周、4周、8周分别处死动物,每次各组各6只,分离下颌骨取材备光镜观察和骨组织形态计量学检测。评价指标:骨小梁各指标(数目、面积比、周长、平均宽度、最长径、最短径)、成骨细胞和破骨细胞个数。所得数据均在SPSS10.0软件下进行成组均数的t检验。结果从拔牙术后2、4、8周各时间点看两组均显示拔牙创骨小梁纤细,排列和形态均不规则,骨量少,骨改建活跃,拔牙创愈合延迟,新生骨愈合质量降低。骨组织形态计量学显示除骨小梁数目外,骨小梁其余各参数值实验组均显著低于对照组(P<0.05),而成骨细胞和破骨细胞个数实验组均显著高于对照组(P<0.05)。结论①以卵巢去势 低钙饮食首次建立新西兰大白兔颌骨骨质疏松模型。②卵巢去势引起的骨质疏松可延缓拔牙创的愈合。     

骨组织工程支架材料充填下颌阻生智牙拔牙窝的临床效果

目的:探讨下颌阻生智牙拔除后,用骨组织工程支架材料充填拔牙窝,修复第二磨牙远中牙槽骨高度的临床效果。方法:13例患者在阻生智牙拔除后,即刻植入组织工程骨微粒(小牛无机松质骨Bio-oss、倍骼生PerioGlasfi)于牙槽窝内,术后定期随访,并从临床和X线影像检查比较术后1、12周时,第二磨牙远中牙龈附着水平和牙槽嵴高度的变化。采用SPSS10.0软件包对数据进行配对样本t检验。结果:所有患者术后未出现并发症,术后12周时,第二磨牙远中牙槽嵴高度显著降低(P<0.05)。结论:下颌阻生智牙拔除术后即刻植入组织工程骨支架材料,有利于保持第二磨牙远中牙槽嵴的高度。     

不同方式处理犬下颌磨牙区即刻种植间隙的效果评价

目的: 探讨在犬下颌磨牙区即刻种植中,不同方式处理拔牙窝与种植体之间的间隙后的新骨形成情况。方法: 选择 6 条 1.5~2.0 岁的拉布拉多犬作为实验对象,在每条犬下颌骨中拔除两侧的第四前磨牙和第一磨牙,分别植入 4 颗牙种植体（Astra Tech^®,4.0 mm × 10 mm）。种植体和拔牙窝骨壁之间的近远中间隙分别进行3种处理,分为空白组（NN组）、胶质银明胶海绵（Gelatamp） 组（EN组）和 Gelatamp + 可吸收胶原膜（CM）组（EG 组）。术后12周收集标本,进行显微CT 扫描和组织学分析。采用SPSS 25.0软件包进行统计学分析。结果: 牙种植术后 12 周存活率为 100%。显微CT 扫描结果显示,新骨高度、骨矿物质密度（BMD）、骨体积分数 （BV/TV）、骨表面积骨体积比（BS/TV）、骨小梁厚度（Tb.Th）、骨小梁数（Tb.N）和骨小梁间距（Tb.Sp）等指标,组间无显著差异。组织学分析结果显示,新骨形成面积和种植体与骨接触面积（BIC）在组间无统计学差异。结论: 使用不同方式处理种植体与拔牙窝之间的间隙后的12周内,与空白对照组相比,单独放置 Gelatamp 或与 CM 联合使用,对种植体周围新骨形成、BIC、BMD、BV/TV、BS/TV、Tb.Th、Tb.N 及 Tb.Sp 等均无显著影响。     

Anisotropic elastic properties of cancellous bone from a human edentulous mandible

The elastic moduli have not been reported for cancellous bone from the edentulous mandible. Accurate values are needed for finite element modeling of the mandible. The aim of this study was to determine elastic modulus values in three orthogonal directions for cancellous bone taken from an edentulous jaw and to relate these values to apparent density and volume fraction. Seven samples were obtained from the edentulous mandible of a 74-year-old female. Young's modulus was determined by compression testing of cubes cut with the faces aligned with the anatomic axes. Bone volume fraction averaged 0.33 (SD 0.14) and apparent density averaged 0.55 g/cc (SD 0.29). Young's modulus was greatest in the mesio-distal direction (mean 907 MPa, SD 849 MPa), followed by the bucco-lingual (mean 511 MPa, SD 565 MPa) and infero-superior direction (mean 114 MPa, SD 78 MPa). The infero-superior direction was less than the bucco-lingual (P = 0.03) and mesio-distal (P = 0.002). The mesio-distal and bucco-lingual directions could not be shown to be different (P = 0.32). This suggests a model of transverse isotropy for cancellous bone in the jaw, where the symmetry axis is along the infero-superior (weakest) direction.     

Alveolar ridge preservation of an extraction socket using autogenous tooth bone graft material for implant site development: prospective case series

This case series evaluated the clinical efficacy of autogenous tooth bone graft material (AutoBT) in alveolar ridge preservation of an extraction socket. Thirteen patients who received extraction socket graft using AutoBT followed by delayed implant placements from Nov. 2008 to Aug. 2010 were evaluated. A total of fifteen implants were placed. The primary and secondary stability of the placed implants were an average of 58 ISQ and 77.9 ISQ, respectively. The average amount of crestal bone loss around the implant was 0.05 mm during an average of 22.5 months (from 12 to 34 months) of functional loading. Newly formed tissues were evident from the 3-month specimen. Within the limitations of this case, autogenous tooth bone graft material can be a favorable bone substitute for extraction socket graft due to its good bone remodeling and osteoconductivity.     

拔牙矫治对牙弓宽度及基骨宽度的影响

目的 :研究拔牙矫治对牙弓宽度和基骨宽度的影响。方法 :在 2 0例AngleⅡ1拔牙病例矫治前后的石膏模型上 ,测量上下颌的牙弓长度、尖牙间牙弓宽度、第二前磨牙间牙弓宽度、第一磨牙间牙弓宽度以及相应的基骨宽度 ,测量结果数据用SPSS 10 .0进行统计学分析。结果 :上颌矫治后尖牙间牙弓宽度和基骨宽度明显增加 (P <0 .0 1) ,前磨牙间牙弓宽度和基骨宽度明显减小 (P <0 .0 1)。下颌矫治后尖牙间牙弓宽度不变而基骨宽度增加 (P <0 .0 5) ,第一磨牙间牙弓宽度不变而基骨宽度减小 (P <0 .0 1) ,前磨牙间牙弓宽度和基骨宽度均减小 (P <0 .0 1)。上下颌牙弓长度均减小 (P <0 .0 1)。结论 :牙弓越向远中移动 ,其牙弓宽度增大 ,越向近中移动 ,牙弓宽度减小 ,相应的基骨宽度也发生同样的变化。牙齿的转矩移动 ,会引起基骨宽度的改变。     

Effect of calcium supplementation on bone dynamics of the maxilla, mandible and proximal tibia in experimental osteoporosis

The effect of calcium supplementation on the bone dynamics in the hard palate of the molar region (maxilla), mandible and proximal tibia in experimental osteoporotic rats was examined. Ninety ovariectomized (OVX) and 45 sham-OVX Wistar female rats were used in this study. All the rats received surgical operation at 6 weeks of age. Ovariectomized rats were fed on a low calcium diet (0.02%) for 12 weeks post-operation, and then randomly divided into the two following groups. One group was fed on high calcium diet (2.30%) (OVX-HCa) and the other group was remained on the low calcium diet (OVX-LCa). Sham-OVX rats were fed on regular calcium diet (1.15%) during the experimental period (Sham-OVX). Histomorphological analysis was carried out from 12 to 32 weeks post-operation. On undecalcified thin section, bone volume, eroded surface, osteoid surface and bone formation rate were calculated for cortical bone of the maxilla, and for cancellous bone of the mandible and proximal tibia. In the OVX-LCa group, compared with the Sham-OVX group, decrease of the bone volume and increase of the bone resorption and formation parameters were detected throughout the observation periods. In the OVX-HCa group, compared with the OVX-LCa group, increase of the bone volume and temporarily increased parameters of bone formation at 1 week after feeding on high calcium diet were observed in the maxilla, but these changes were not observed in the mandible and proximal tibia. Moreover, the bone resorption and formation parameters in the maxilla, mandible and proximal tibia in the OVX-HCa group became equivalent to the Sham-OVX levels with the passage of time.     

Evaluation by quantitative magnetic resonance imaging of trabecular bone quality in the dentate and edentulous mandible

OBJECTIVE: To quantify the differences in mandibular trabecular bone quality between edentulous and dentate patients using quantitative magnetic resonance imaging (QMRI). METHODS: The patients in this study had been referred to our clinic for QMRI examination for various reasons. A total of 40 male patients (18 dentate, 22 edentulous), 45-55 years of age, were examined. Mandibular T2* axial cross-sections were performed following receipt of consent from each patient. T2* relaxation time values (RTVs) were determined in the trabecular area. RESULTS: The mean mandibular T2* RTVs of dentate and edentulous patients were 181 and 182, respectively. There were no significant differences between the two groups (P=0.929) (Student's t-test). CONCLUSIONS: Mandibular trabecular bone quality may not be influenced by edentulousness according to QMRI.     

Quality and quantity of bone following alveolar distraction osteogenesis in the human mandible

PURPOSE: The purpose of this prospective study on humans were to evaluate (a) the clinical outcome of alveolar distraction osteogenesis for the correction of vertically deficient edentulous mandibular ridges, (b) the clinical outcome of dental implants placed in the distracted areas, and (c) the quality and quantity of the bone that had formed in the distraction gap. MATERIAL AND METHODS: Seven patients presenting vertically deficient edentulous ridges were treated by means of distraction osteogenesis with an intraoral alveolar distractor. Approximately 3 months after consolidation of the distracted segments, 20 ITI solid screw SLA implants were placed in the distracted areas. Three to 4 months later, abutments were connected and prosthetic loading of the implants started. During implant site preparation, bone biopsies were taken at the implant sites with trephine burrs for histologic and histometric analyses. RESULTS: The mean follow-up after the initial prosthetic loading was 18 months (range 12-24 months). The mean bone gain obtained at the end of distraction was 7 mm (range 5-9 mm). The cumulative success rate of implants 2 years after the onset of prosthetic loading was 95%, whereas the survival rate of implants was 100%. The newly formed bone consisted of woven bone reinforced by parallel-fibered bone with bone marrow spaces between the bone trabeculae. The bone area fraction in the distraction region ranged from 21.6% to 57.8% (38.5+/-11.7%). DISCUSSION AND CONCLUSIONS: Results from this study showed that (a) distraction osteogenesis is a reliable technique for the correction of vertically deficient edentulous ridges, (b) the regenerated bone withstood the functional demands of implant loading, (c) survival and success rates of implants placed in the distracted areas were consistent with those of implants placed in native bone, and (d) there is sufficient bone volume and maturity in the distracted region for primary stability of the implant.     

Influence of platelet rich fibrin on post-extraction socket healing: A clinical and radiographic study

Aim

The aim of this study was to evaluate clinically and radiographically, extraction socket healing using autologous platelet rich fibrin (PRF).

Effects of lithium on extraction socket healing in rats assessed with micro-computed tomography

Abstract

Objective. Lithium is an activator of β-catenin signaling and β-catenin plays an important role in regulating bone formation and remodeling. The purpose of this study was to investigate the effects of lithium on bone repair in tooth extraction sockets in rats. Material and methods. Twenty male Wistar rats were subjected to maxillary left second molar extraction. The animals received a daily injection of lithium chloride (LiCl) or the same dose of sodium chloride (NaCl) starting 7 days before tooth extraction until sacrifice 14 days after extraction. Rats were randomly divided into: (1) a pre-treated group that received LiCl injection from 7 days before to 3 days after tooth extraction; (2) a post-treated group that received LiCl injection starting 4 days after tooth extraction; (3) a continuously treated group that received LiCl injection for the entire 21 days; and (4) a control group that received NaCl injection only. The volume of new bone and the bone density in the extraction socket were quantified by micro-computed tomography. Results. The percentage of new bone formation in the extraction socket was as follows: 63.2 ± 13.4% (pre-treated group), 53.9 ± 9.8% (post-treated), 23.8 ± 8.0% (continuously treated) and 37.5 ± 4.2% (control). The difference in percentage was statistically significant between each pair of groups. Pre- and post-treated groups also showed a significant increase in the density of new bone. Conclusions. Lithium enhances bone repair in extraction sockets when delivered before or after tooth extraction. Tooth extraction during lithium treatment may impair bone healing.     

Cortical porosity of the mandible in an osteoporotic sheep model

Objectives: Cortical porosity and thickness of the axial and the appendicular skeleton are predictors of osteoporotic fractures. In the jawbone, however, cortical porosity and thickness may affect the mechanical stability of dental implants. We have shown previously that the jawbone of osteoporotic sheep has impaired trabecular structures, but whether catabolic bone turnover also accounts for the cortical bone porosity remains unknown. Material and methods: We compared mandibular bone from six geriatric sheep subjected to ovariectomy, calcium/vitamin D restriction, and methylprednisolone administration to those of six healthy adult control sheep. Histological ground sections were prepared from the diastema, first and second premolars, and postmolar region. Cortical porosity and thickness were assessed by histomorphometry. Results: Cortical porosity was higher in osteoporotic sheep than in adult controls in the diastema and in the first and second premolar region. In the postmolar region, the difference failed to reach the level of significance. The changes were even more prominent when histomorphometry was restricted to the inner millimeter of the mandibular cortex. In contrast, induction of osteoporosis did not have a discernable effect on cortical thickness. Conclusion: These results demonstrate that cortical porosity of mandibles is more pronounced in geriatric osteoporotic sheep than in adult controls. To cite this article:
Dvorak G, Reich KM, Tangl S, Goldhahn J, Haas R, Gruber R. Cortical porosity of the mandible in an osteoporotic sheep model.
Clin. Oral Impl. Res 22 , 2011; 500–505
doi: 10.1111/j.1600‐0501.2010.02031.x     

Rehabilitation of the edentulous mandible with implant-supported overdenture using ball attachments and healing abutments: A case report

For many years, osseointegrated implant-supported overdentures have been used in the rehabilitation of the edentulous lower jaw with excellent results. In this report, additional implants with healing abutments were applied posterior to mental foramen on each side was used to achieve additional support to the overdenture.     

Histomorphometric study on the effects of age on orthodontic tooth movement and alveolar bone turnover in rats

The aim of this study was to investigate, in a rat model, the effects of age on the amount of tooth movement and concomitant changes in alveolar bone turnover activity adjacent to orthodontically treated tooth roots. Rats (n = 48) of four different age groups (10, 30, 50, and 80 wk of age) were used in the experiment. Maxillary first molars were tipped mesially with a nickel titanium alloy coil-spring for 2 wk by a continuous force of 10 cN. Forty-eight age-matched untreated rats were used as controls. The changes in alveolar bone turnover were assessed histomorphometrically. Two weeks after the start of tooth movement, the amount of tooth movement was found to decrease with age and was significantly different among the four age groups. The histomorphometric study demonstrated that, in all experimental groups, turnover of alveolar bone increased significantly compared with that of each age-matched untreated group. However, the rate of increase decreased in an age-related manner. These results suggest that the age-dependent decrease in alveolar bone turnover activity, in response to mechanical forces, may negatively affect the amount of tooth movement.     

聚乳酸、rhBMP-2复合体在牙槽骨修复中作用的实验研究

目的研究聚乳酸与rhBMP-2的复合体在牙槽骨修复中作用，寻找一种适合临床应用促进牙槽骨再生的新型的生物材料。方法杂种犬6只，随机分为2组，拔除每只犬的上下颌前磨牙，右侧拔牙创填入聚乳酸与rhBMP-2的复合体，左侧拔牙创自然愈合作对照，于2周、6周和10周行X线检查，于6周和10周分别处死2组犬，取拔牙创标本行光镜和扫描电镜观察对比两组成骨状况及植入材料在组织内的反应。结果X线检查及病理结果显示右侧拔牙创愈合快，成骨速度及成骨质量明显优于左侧自然愈合的拔牙创。电镜显示该材料组织相容性好，无炎性刺激反应，可降解。结论聚乳酸与rhBMP-2复合体是一种促牙槽骨再生的新型生物复合材料．可望成为临床实际应用的修复牙槽骨缺损的新型材料。