不对称性颌间牵引对成年SD大鼠髁突胶原成熟和钙盐沉积的影响

目的:通过观察不对称牵引引起的成年SD大鼠髁突软骨下骨的成骨活性变化,了解关节外不对称机械应力对髁突的影响.方法:选用10周龄雄性SD大鼠20只(随机分为轻力组8只、重力组8只、对照组4只),实验组动物使用关节外固定加力装置,分别施加0.39 N和1.18 N(轻力组和重力组)的力,加力第28天拆除加力装置,第56天取得标本.在实验前1天、去除牵引装置前1天和处死前1天注射荧光染料,.使用Masson染色和活体荧光技术观察软骨下骨的胶原成熟和钙盐沉积.结果:正常软骨下骨有成骨活动,在负荷加载后,加力侧骨胶原成熟程度高于非加力侧,较小负荷引发的成骨活动更为活跃.结论:成年个体的髁突软骨下骨在外力刺激下出现成骨活性变化,发生适应机械应力环境的重塑,压应力促进胶原成熟,但旋转位移抑制胶原成熟.负荷增加可促进成骨,轻力的促进效应更强.     

不对称性颌间牵引作用下BMP2在成年SD大鼠髁突关节下骨中的表达

目的：通过观察不对称牵引引起的成年大鼠髁突关节下骨中与骨改建密切相关的BMP2的表达情况,了解关节下骨对不对称机械应力的反应。方法：选用10周龄雄性SD大鼠220只（分轻力组104只、重力组104只、对照组12只）,实验组动物使用关节外固定加力装置,分别施加0.39N、1.18N（轻力组和重力组）,加力第28天拆除加力装置。在加力后3、7、14、28d以及停止牵引后3、7、14、28d分别取得左右侧标本,进行免疫组织化学染色,对结果进行计算机辅助的半定量分析。结果：正常的关节下骨也有BMP2的表达,内源性BMP2的表达增加与机械应力有关,BMP2表达的量受到力量的大小的影响。结论：BMP2参与不对称牵引引起的重塑过程。     

不对称牵引对成年SD大鼠髁突软骨中胶原类型影响的研究

目的 观察不对称牵引作用下,成年SD大鼠髁突软骨中胶原类型的变化。方法 选用10周龄雄性SD大鼠220只(随机分为轻力组104只、重力组104只、对照组12只),实验组动物使用关节外固定加力装置,分别施加0.39N和1.18N(轻力组和重力组),加力第28天拆除加力装置。在加力后3、7、14、28d以及停止牵引后3、7、14、28d分别取得标本,进行苦味素-天狼星红染色,用偏振光显微镜进行观察。结果 不同类型胶原的主要分布位置和排列形态不同,Ⅰ、Ⅱ、Ⅲ型胶原出现的部位和数量随着加力的大小和不同的实验阶段出现变化。Ⅲ型胶原较多出现在受力较大、负荷出现时间较长的部位。结论 成年个体的髁突软骨在外力刺激下,仍然出现胶原合成和类型的变化,重力组的胶原类型更替在经历了较长的时间后仍然持续进行。?     

不对称牵引对成年大鼠髁突软骨Ⅱ型胶原的影响

目的通过观察不对称牵引引起的成年SD大鼠髁突软骨中Ⅱ型胶原的变化,了解关节外机械应力对髁突软骨细胞合成Ⅱ型胶原活性的影响。方法选用10周龄雄性SD大鼠220只（随机分为轻力组104只、重力组104只、对照组12只）,实验组动物使用关节外固定加力装置,分别施加0.39 N和1.18 N（轻力组和重力组）,加力第28天拆除加力装置。在加力后3、7、14、28 d以及停止牵引后3、7、14、28 d分别取得标本,进行免疫组化染色。结果Ⅱ型胶原阳性信号主要在软骨细胞胞浆表达,在成熟带和肥大带细胞中表达明显。在实验的不同阶段,不同部位的发生表达强度不同。在牵引力加载以后,重力组Ⅱ型胶原表达的变化的幅度不如轻力组明显,但2组相对应的加力侧和非加力侧发生的变化趋势相近---加力侧在加力早期出现表达下调,在去除牵引力后出现表达量的增加,随即又下降到在加力阶段最低的水平,然后逐渐升高;非加力侧在加力后表达上调,2组在第14天达到高峰。去除牵引力后,发生下调,然后都再次升高。结论成年个体的髁突软骨在受到外力后仍然出现了Ⅱ型胶原合成的变化。Ⅱ型胶原的表达在蛋白质合成活跃的成熟带和肥大带出现,单侧向前牵引对加力侧的软骨基质合成具有抑制作用,较大的牵引力对抑制作用要强于较轻的牵引力;非加力侧受到的应力性质不同,出现细胞外基质合成加速。     

不同咀嚼压力对幼兔髁突软骨成骨的影响研究

目的：分析生长发育期不同咀嚼模式下兔髁突软骨成骨形态学的差异,研究咀嚼压力对幼兔髁突生长发育的影响和作用机制。方法：选取15天龄的未断奶幼兔16只,随机分为硬食组和软食组各8只,硬食组提供颗粒饲料,软食组提供由同种颗粒饲料碾磨而成的粉末状饲料。幼兔28天龄断奶,分别于28天龄、33天龄肌肉注射四环素、钙黄绿素,38天龄处死幼兔。制作硬组织切片,荧光显微镜观察,独立t检验分析比较两组髁突软骨成骨厚度,骨形态学参数。结果：硬食组的软骨成骨厚度、骨小梁相对体积、骨小梁数量、骨小梁厚度均大于软食组（P<0.05）,硬食组骨小梁分离度小于软食组（P<0.05）。相同时间硬食组骨形成沉积率[（3.25±0.02）μm / d ]大于软食组[（2.37±0.02）μm / d ]。结论：生长期软食组幼兔的髁突软骨成骨能力较硬食组弱,咀嚼负荷力是影响髁突软骨成骨生长的重要因素。     

功能性矫治器引导下颌后退对大鼠髁突软骨新骨形成影响的实验研究

目的探讨功能性矫治器引导下颌后退所致的髁突软骨新骨形成的影响。方法选用4周龄SD雄性大鼠45只,分为实验组及对照组,每组5只。实验组模拟临床功能性矫治器引导大鼠下颌后退。分别在0、3、7、14及21 d全麻下处死动物各5只。苏木精-伊红染色观察细胞形态反应,PAS染色观察新骨形成量。结果大鼠在下颌持续后退情况下,实验组髁突后份软骨组织增殖层和成熟层明显变薄,移行区可见破骨细胞增加,此区附近的骨小梁骨沉积减少;实验第3天及第7天,实验组和对照组髁突软骨新骨形成的量有明显区别,第14天和第21天,二者间的差别趋于减小。结论后退大鼠下颌后,髁突软骨后份新骨形成量减少。     

颞下颌关节退行性变早期髁突软骨细胞行为改变的实验研究

目的 探索应力诱导颞下颌关节(TMJ)退行性变早期,髁突软骨细胞增殖、凋亡和自噬行为表现及相关信号通路的变化.方法 使用小鼠强制张口模型分别对小鼠加力0 d(对照组)和10 d(实验组),加力结束后取样.髁突软骨行激光共聚焦扫描,5-乙炔基-2'脱氧尿嘧啶核苷(EdU)染色检测增殖;完整关节区切片行苏木精/伊红、甲苯胺...     

下颌持续前导对成年大鼠髁突软骨骨形态发生蛋白表达及超微结构的影响

目的 观察成年期大鼠在下颌持续前导作用下髁突软骨的改建以及超微结构的变化。方法 将30只9周龄SD大鼠随机分为实验组和对照组,实验组佩戴上颌斜面导板,对照组不做任何处理,分别在第3、7、14、21、30天处死动物并取材,免疫组织化学染色检测骨形态发生蛋白2（BMP-2）在髁突中的表达及分布,透射电镜观察髁突软骨细胞的超微结构,Micro CT分析髁突骨质的变化。结果 与对照组相比,实验组髁突中部和后部软骨增生明显,软骨细胞BMP-2阳性细胞率及灰度值在第7天开始增多,随时间延长而增强,髁突软骨细胞的超微结构出现细胞核固缩,核周微丝变少、脂滴变小、内质网腔隙肿胀、细胞外基质增宽变多等。Micro-CT显示实验组的新生骨和骨小梁厚度、骨小梁数量和分离度随时间延长而增加。结论 在下颌持续前导下,成年期大鼠髁突软骨出现增生性改建,并存在BMP-2的高表达。     

渐进性咬合紊乱对大鼠颞下颌关节的影响

目的:探讨渐进性咬合紊乱对大鼠颞下颌关节的影响。方法:9只成年雄性SD大鼠,随机分为实验组(3只),操作对照组(3只)和空白对照组(3只)。实验组大鼠左侧上颌第一、第二磨牙间及右侧下颌第一、第二磨牙间分别嵌入正畸用皮圈推第一磨牙向近中,造成磨牙尖窝接触不吻合的渐进性咬合紊乱。术后6周取双侧颞下颌关节作HE染色观察。结果:操作对照组与空白对照组间未见差异,实验组与对照组相比髁突软骨中部增厚,后部变薄(P<0.05);关节盘中带和后带均明显变薄(P<0.05);实验组中部和后部软骨下骨小梁变得明显垂直于髁突表面排列。结论:渐进性咬合紊乱可以引起大鼠髁突软骨及软骨下骨小梁适应性改建。     

过氧化物酶增殖活化受体γ对老龄鼠髁状突的影响

目的 通过给予过氧化物酶增殖活化受体γ(peroxisome proliferator-activated receptor γ,PPARγ)激动剂-吡格列酮,观察PPARγ对老龄鼠髁状突软骨及软骨下骨的影响.方法 18月龄健康雄性C57BL/6小鼠20只,随机分为两组,实验组每日予以吡格列酮灌胃20 mg/kg,对照组每日予以生理盐水灌胃.8周后处死动物取双侧下颌骨,行下颌骨X线检查及髁状突骨密度测定,同时行髁状突部位组织学观察,并采用骨形态计量学方法计算髁状突软骨下骨的静态骨参数.结果 实验组髁状突的X线片灰度值、骨密度、骨小梁面积百分率、骨小梁的平均宽度、胶原纤维及弹性纤维的含量均明显低于对照组.结论 PPARγ能抑制老龄鼠髁状突的成骨代谢及软骨的增殖和分化,促进其髁状突骨质疏松的发生、发展.     

牙齿移动过程中牙槽骨显微结构动态变化的微型CT研究

目的 通过微型CT探讨正畸牙齿移动过程中矫治力对牙槽骨骨小梁的影响规律,以期为正畸临床提供参考.方法 选择10周龄SD雄性大鼠10只建立实验动物模型,施加0.196 N矫治力,近中移动上颌第一磨牙,分别于加力前、加力后第3、7、14 d对大鼠上颌牙槽骨骨小梁进行微型CT扫描,计算骨体积分数、骨表面积体积比、结构模型指数...     

Response of mandibular condyles of juvenile and adult rats to abnormal occlusion and subsequent exemption

ObjectiveThe adaptation capacities of the mandibular condyle in response to mechanical stimuli might be different between juveniles and adults, but has not been compared. This study aimed to investigate whether abnormal molar occlusion and subsequent molar extraction could lead to different remodeling responses in the mandibular condyles of juvenile and adult rats.MethodsAbnormal molar occlusion (AMO) was established in the 5- and 16-wk old rats by moving their maxillary left and mandibular right third molars distally. AMO was removed in the molar extraction group at 4 weeks but remained in the AMO group. All rats were sacrificed at 8 weeks. Micro-computed tomography, histomorphology, immunohistochemistry and real-time PCR were adopted to evaluate the remodeling of condylar subchondral bone.ResultsCondylar subchondral bone loss and increased osteoclastic activities were observed in both juvenile and adult AMO groups, while increased osteoblastic activities were only seen in the juvenile AMO group. Decreased bone mineral density, bone volume fraction and trabecular thickness, but increased trabecular separation, number and surface of osteoclasts and mRNA levels of TRAP, cathepsin-K, RANKL in the juvenile AMO group were all reversed after molar extraction (all P < 0.05). However, these parameters showed no difference between adult AMO and extraction groups (all P > 0.05).ConclusionsAbnormal molar occlusion led to degenerative remodeling in the mandibular condyles of both juvenile and adult rats, while exemption of abnormal occlusion caused significant rescue of the degenerative changes only in the juvenile rats.     

Stability of implants as anchorage for orthopedic traction.

The aim of this animal study was to investigate the stability of osseointegrated fixtures when used as anchorage for orthopedic traction with extreme force magnitude. Three Br?nemark fixtures were placed in the left zygomatic arch and three in the right of five adult dogs. An orthopedic nonaxial force of 5 N was applied using an intraoral coil system. The initial displacement immediately after force application was measured by means of speckle interferometry. After 2 months of continuous loading, bone adaptation and mineralization around all implants were analyzed. All the loaded implants were immobile. Significant marginal bone loss at the abutment-fixture interface (<1 mm) was observed around each loaded fixture implant. Bone remodeling was significantly more pronounced at the tension side of the implants, irrespective of fixture length. Radiographical and histological analyses showed bone with normal trabecular pattern around the implants.     

Changes in alveolar bone structure during orthodontic tooth movement in adolescent and adult rats: A microcomputed tomography study

Background

Increasing number of adults are willing to seek orthodontic treatment, but treatment duration for them is commonly longer. Although there have been studies on molecular biological changes during tooth movement, few have focused on microstructural changes in alveolar bone.

Objective

This study aims to compare the microstructural changes in alveolar bone during orthodontic tooth movement in adolescent and adult rats.

Methods

25 6-week-old and 25 8-month-old male Sprague–Dawley (SD) rats were used to build orthodontic tooth-movement models. On Days 0, 1, 3, 7 and 14, the rats were sacrificed. Microcomputed tomography was used to evaluate tooth movement, alveolar crest height loss and microstructural parameters of alveolar bone (bone volume fraction, trabecular thickness, trabecular separation and trabecular number).

Results

Tooth movement in the adult group was slower than in the adolescent group. Alveolar bone crest height in adults was lower than it was in adolescents on Day 0. Under orthodontic force, the alveolar crest in both groups decreased and the degree of decrease are higher at early stage in adolescents. The microstructural parameters indicated that the alveolar bone was originally denser in the adult rats. With orthodontic force, it tended to be looser.

Conclusions

Under orthodontic force, changes in alveolar bone differ between adolescent and adult rats. Tooth movements in adults are slower, and the decrease in alveolar bone density are more severe.     

The expression of osteopontin with condylar remodeling in growing rats.

It is suggested that osteopontin may promote osteoclast binding to resorptive sites by interacting with the alphavbeta3 receptor on osteoclasts. However, the role of osteopontin in functional remodeling of bony structures remains unclear. The present study was conducted to examine the distribution of osteopontin on the condyle and explore the role in condylar remodeling in growing rats using an immunohistochemical method. Twenty Wistar strain male rats aged 7, 14, 28 and 56 days were used. In 7- and 14-day-old rats, no immunoreaction to osteopontin was detected in the cartilage cells. In 28-day-old rats initiating mastication, the thickness of condylar cartilage was decreased abruptly as compared to the younger rats. High immunoreaction to osteopontin was found in the cytoplasm of hypertrophic chondrocytes and on the trabecular bone surfaces of primary spongiosa adjacent to the osteoclasts or chondroclasts. The immunoreactions to osteopontin in the cytoplasm of hypertrophic chondrocytes were less in 56-day-old rats than in 28-day-old rats. It is shown that the alteration in mechanical loading on the mandibular condyle due to functional changes from weaning to mastication correlates with the localization of osteopontin in growing rats. Furthermore, it is suggested that osteopontin may stimulate osteoclastic resorption of calcified matrix by mediating the attachment of osteoclasts and/or chondroclasts during growth-related functional remodeling of the condyle.     

正畸力作用下垂直型骨吸收牙周炎大鼠牙槽骨改建的实验研究

目的：观察正畸力作用下牙周炎大鼠垂直吸收的牙槽骨改建,为牙周炎的临床正畸治疗提供依据。方法：将75只10周龄雄性SD大鼠,随机分为3组,正常加力对照组（ A）、牙周炎垂直骨吸收对照组（ B）、牙周炎垂直骨吸收加力实验组（ C）,每组各25只,各组动物分别于加力后8 h,1、7、14、21 d处死,取动物模型上颌左侧第一磨牙近中牙槽骨进行组织学及免疫学检测,所得结果进行对比研究。结果：正畸加力至7d时,实验组大鼠垂直吸收侧牙周膜纤维排列紊乱,出现无细胞结构,结缔组织可见少量炎症细胞,牙槽骨表面还可见功能活跃的多核破骨细胞,与对照组相比较无显著差异,实验组大鼠牙周组织中IGF?1表达达到峰值,光密度值最高,与对照组比较有显著差异（ P＜0．05）;加力至14 d时,实验组大鼠垂直吸收侧牙周组织中RUNX2的表达达到峰值,其光密度值最高,明显高于正常加力对照组,其变化有统计学意义（P＜0．05）。结论：控制牙周炎症和消除咬合创伤后,正畸力能刺激牙周炎大鼠垂直缺损牙槽骨区域的RUNX2和IGF?1的表达增强,合成骨胶原和骨基质的能力增强,从而促进牙槽骨的改建。     

Effects of interferon-gamma on bone remodeling during experimental tooth movement

OBJECTIVE: To determine the effects of interferon-gamma (IFN-gamma) on bone remodeling during orthodontic tooth movement. MATERIALS AND METHODS: Thirty adult male Sprague Dawley rats were randomly categorized into five groups. IFN-gamma was administered in three different doses (0.01, 0.02, and 0.05 microg/20 microL) and the remaining two groups served as control. Mandibular first molars were moved mesially by means of Ni-Ti closed coil springs in all groups. The results were evaluated histomorphometrically, and parameters of trabecular bone volume (BV/TV), trabecular bone number (Tr.N), and trabecular separation (Tr.Sep) were observed at the interradicular bone area of the mandibular first molars. RESULTS: Increases in BV/TV and Tr.N and decreases in Tr.Sep revealed the antiosteoclastic activity of IFN-gamma. CONCLUSION: IFN-gamma administration may be useful clinically for anchorage control.