人下颌骨在不同应变率下的拉伸强度

研究下颌骨在不同应变率下的生物力学性质，分析应变率和骨密度对极限强度、弹性真量和破坏应变的影响。方法：以5具新鲜男性青年尸体的下颌骨为材料，对每具标本进行骨密度测定，然后制成标准试件在INSTRON材料试验机上进行电子拉伸，应变率分别为0．0003、0．003、0．03、0．3s-1，获得不同应变率下的应力-应变曲线、下颌骨的极限强度、弹性模量以及破坏应变。应用Oropn5．0软件在PC机上进行数据统计和分析。结果：下颌骨在0．0003、0．003、0．03、0．3s-1的拉伸应变率下的极限强度分别为61．24、66．88、74．55、81．11N／mm2，弹性模量分别为15．17×103、16．72×103、1852×103、21．67×103N／mm2，破坏应变分别为0．731％、0．666％、0．625％、0．593％。结论：下颌骨为粘弹性材料，其生物力学性质和应变率有密切的关系．随着应变车数量级的增加，极限强度是逐后递增的，而骨密度和极限强度呈正相关关系。     

人下颌骨在压缩载荷下的生物力学性质

目的研究下颌骨在不同压缩载荷下的生物力学性质,建立下颌骨在压缩载荷下的本构方程。方法以5具新鲜男性青年尸体的下颌骨为材料,对每具标本进行骨密度测定,然后制成标准试件在INSTRON材料试验机上进行电子压缩,应变率分别为0.000　5、0.005、0.05、0.5s-1,获得不同载荷下相应的应力-应变曲线。利用模型Y=aρ     

头颈部癌患者手术及放疗前后T细胞亚群变化及其预后价值

应用单克隆抗体和流式细胞仪式对８６例头颈部癌患者治疗前后行外周血Ｔ淋巴细胞亚群分布的检测，并结合随访资料作回顾性分析，患者中４１例采用根治性手术加术后放射治疗，其余４５例采用放疗，放射剂量４０ＧＹ－７２ＧＹ。随访１２－１９月，中位随访期１６月。结果表明：（１）头颈部癌患者的ＣＤ３＾＋和ＣＤ４＾＋比正常人明显下降（Ｐ＜０．０５），ＣＤ８＾＋明显上升（Ｐ＜０．０１）。ＣＤ４＾＋／ＣＤ８＾＋比值非常明显     

140例维吾尔族百岁老人下颌骨体表测量的观察

目的：观察下颌骨体有无增龄变化及其相关因素。方法：对１４０例维吾尔族百岁老人采用对一侧下颌骨体表直接测量长度及高度，并进行统计学处理。结果：一侧下颌骨体表长度在８．５ｃｍ～１３．０ｃｍ，高度在１．５ｃｍ～５．０ｃｍ，青年组长度大于百岁组（Ｐ＜０．００１），男性组长、高度大于女性组（Ｐ＜０．０１），有牙颌组长高度大于无牙颌组（Ｐ＜０．０１），正常舌组下颌骨长度大于裂纹舌组（Ｐ＜０．０５），但高度无显著性差异（Ｐ＞０．０５）。结论：下颌骨长高度具有生理变化，同时年龄、性别、有无牙列亦有影响，裂纹舌可能与下颌骨缩小有关。百岁老人有下颌骨体增龄表现     

Sjoegren综合征中T细胞亚群值的测定

目的：研究Ｓｊｏｅｇｒｅｎ综合征中Ｔ细胞亚群和免疫球蛋白的变化，方法：应用单克隆抗体技术检测Ｔ细胞亚群，用单向免疫扩散法检测ＩｇＡ，ＩｇＧ，ＩｇＭ。结果：Ｓｊｏｅｇｒｅｎ综合征患者外周血中ＣＤ＾４降低（Ｐ〈０．０５），ＣＤ＾８升高（Ｐ〈０．０５），其程度与病情发展相一致，严重者ＣＤ＾４／ＣＤ＾８倒置，ＩｇＡ，ＩｇＧ，ＩｇＭ均升高（Ｐ〈０．０５），尤以ＩｇＧ显著（Ｐ〈０．０１），结论：Ｓｊｏｅｇｒｅ     

磷［~（32）P］玻璃微球联合加热或平阳霉素的体外抗肿瘤作用

采用集落形成试验，观察了磷（＾３２Ｐ）玻璃微球（＾３２Ｐ－ＧＭＳ）联合加热（水浴，４３℃，２０ｍｉｎ）或化疗药物（平阳霉素，终浓度０．０８μｇ／ｍｌ）对人舌磷状细胞癌，Ｔｃａ８１１３的作用。结果表明：＾３１Ｐ－ＧＭＳ联合加热有协同增效作用（Ｅ／Ｏ值为１．６３），联合平阳霉素有相加作用（Ｅ／Ｏ值１．０１）。     

聋哑青少年口腔卫生状况调查分析

本文调查分析了南京市聋哑学校３３４名青少年的口腔卫生状况，结果表明：牙龈炎患病率７１．２６％，软垢指数、牙结石指数与龈指数间有相关关系（τ＝０．３１、ｕ＝７．４、Ｐ〈０．０１和τ＝０．４２、ｕ＝１４．３１、Ｐ〈０．０１）。龋患率为６７．０７％，第一恒磨牙龋患率５０％，错Ｈｅ畸形患病率９１．６２％。作者分析了聋哑青少年口腔卫生状况差的原因，并探讨了改进措施。     

青少年牙周炎患者IL－2、T细胞亚群变化的研究

青少年牙周炎（ＪＰ）病因除特殊致病菌的感染，还包括免疫应答异常等宿主易感性因素的作用。实验采用生物学测定法，检测２７名ＪＰ患者和１５名对照者外周血单个核细胞（ＰＢＭＣ）ＩＬ－２产生水平。并用ＯＫＴ系列单克隆抗体、及碱性磷酸酶抗碱性磷酸酶桥联酶标法（ＡＰＡＡＰ），检测了外周血Ｔ淋巴细胞群、亚群和ＩＬ－２受体（ＩＬ－２Ｒ）的表达，结果表明：ＪＰ组ＩＬ－２活性单位（１２．４±５．０μ／ｍｌ）明显高于对照组（６．６±２．９μ／ｍｌ，Ｐ＜０．０１）．ＪＰ组细胞百分率均显著低于对照组，ＩＬ－２Ｒ（＋）、比值相差不显著，ＩＬ－２水平与百分率呈显著负相关（ｒ＝－０．５１０７，Ｐ＜０．０５）．还发现ＪＰ患者ＩＬ－２产生水平与附着水平和牙周袋深度均呈显著正相关（ｒ分别为０．５４２５、０．５３８５，Ｐ＜０．０１）．提示ＩＬ－２产生水平的变化可能反映了牙周的破坏程度。     

口腔矫治器治疗阻塞性睡眠呼吸暂停综合征：附10例报告

用夜间多导睡眠图监测结合Ｘ线头影测量法，分析了口腔矫治器对１０例阻塞性睡眠呼吸暂停综合征患者气道、睡眠结构及呼吸功能的影响。结果显示，戴用矫治器后下颌在水平向和垂直向的位移平均分别为１．７３ｍｍ和９．３０ｍｍ，上后气道间隙平均增加２．８０ｍｍ（Ｐ＜０．０１），中气道间隙平均增加６．７５ｍｍ（Ｐ＝０．０１），下气道间隙变化的差异无显著性（Ｐ＞０．０５）。１０名患者的呼吸暂停指数平均下降１５．９８次／小时（Ｐ＜０．０１），有９名患者总呼吸紊乱指数平均下降３２．８１次／小时（Ｐ＜０．０１），另一例无低通气记录。最低ＳａＯ２平均从７３．８７％上升到８５．５０％（Ｐ＜０．０１）。上气道阻塞频率的降低，可归因于矫治器对口咽部结构的影响。作者认为，口腔矫治器是治疗该病的一种有效疗法。     

Bass刷牙法去除菌斑的效果观察

作者对２０名受试者进行了习惯刷牙法与Ｂａｓｓ刷牙法效果的比较试验，分别记录了刷牙前、习惯刷牙后及Ｂａｓｓ法刷牙后６／４１│１４／６ ６个牙颊面的菌斑指数（ＰＬＩ），并进行单因素方差分析及两两比较。结果表明：刷牙前和习惯刷牙后的ＰＬＩ无显著性差异（Ｐ〉０．０５）；习惯刷牙后与Ｂａｓｓ法刷牙后的ＰＬＩ有显著性差异（Ｐ〈０．０５）．Ｂａｓｓ刷牙后与刷牙前的ＰＬＩ有极显著性差异（Ｐ〈０．０１），说明习惯刷     

Effects of bisphosphonate on the mandible of rats in the growing phase with steroid-induced osteoporosis

AIM: The objective of this study was to investigate the effects of bisphosphonate on the mandible of rats in the growing phase with steroid-induced osteoporosis, and to estimate the biomechanical response in the mandibular bone. MATERIALS AND METHODS: Eight-week-old male Wistar rats (n = 50) were assigned to a 6-week control (Co-6) group, 6-week steroid (St) group, 9-week control (Co-9) group, 9-week steroid + standard diet (StSD) group, or 9-week steroid + standard diet + bisphosphonate (StSDBp) group. The mandibular bone was evaluated by two-dimensional bone density measurement (PDS-15), three-dimensional pQCT, and quantitative analysis of Ca, P, Mg, and Zn using a sequential high frequency plasma spectrometer (ICPS-8000). RESULTS: In PDS-15 analysis, the bone density converted to aluminum equivalent was higher in StSDBp group when compared with the StSD group, and no significant difference was observed in bone density between St group and Co-6 group. In pQCT analysis, trabecular bone density and mineral content were significantly higher, while all other bone parameters were significantly lower in St group when compared with the Co-6 group. The densities of trabecular and cortical bones, mineral content and cross-sectional area of cortical bone, and non-invasive stress strain index with reference to x and yaxes were higher in StSDBp group than in StSD group. In quantitative analyses, Ca and P were markedly higher in StSDBp group than in StSD group, while there were no differences in Mg and Zn. CONCLUSION: Bisphosphonate treatment increases trabecular and cortical bone parameters in the mandible of growing rats with steroid-induced osteoporosis.     

Dynamic creep of dental amalgam as a function of stress and number of applied stress cycles

Dynamic creep tests on specimens of dental amalgam gave a relationship between creep (epsilon), applied dynamic stress (sigma), and number of applied stress cycles (N) as epsilon = AN (m sigma + c) where A, m, and c are constants. This equation can be used to predict creep of amalgam at low levels of stress and extended times. The pattern of results produced for different types of amalgam indicates that the creep process is multifactorial in nature.     

The influence of loss of bone mass on induced periodontal disease: a radiographic and densitometric study of female rats

BACKGROUND: Changes in mineral density in the mandibular and femoral bones (BMD) after estrogen deficiency caused by ovariectomy (OVX) and the influence of these changes on induced periodontal disease were evaluated in female rats. METHODS: Forty-eight female Holtzman rats (90 days old) were randomly divided into five groups: 0: control (N = 9); 1: SHAM without induced periodontal disease (N = 11); 2: SHAM with induced disease (N = 10); 3: OVX without induced disease (N = 9); and 4: OVX with induced disease (N = 9). In groups 2 and 4, the first lower molars were tied with ligatures for 30 days 120 days after surgery. After 5 months the animals were sacrificed to measure global mineral density (BMD) and that of the sub-regions of the mandible and femur by dual energy x-ray absorptiometry (DXA). The extent of vertical bone loss was evaluated with digital radiography by measuring the distance from the bone crest to the cemento-enamel junction at the mesial of the first lower molar. RESULTS: Results of the femur (Kruskal-Wallis test) showed a significant difference (P <0.001) between the groups SHAM and OVX in bone density values for all regions. Comparison between the groups in relation to the BMD of the mandible, both in the sub-regions and global revealed no differences (P >0.05). The vertical bone loss measured for the groups with induced disease was similar (P = 0.713). CONCLUSIONS: Differences between the groups were found in the bone mineral density BMD of the femur but not of the mandible. OVX had no influence on induced periodontal disease.     

Implant stability and histomorphometry: a correlation study in human cadavers using stepped cylinder implants

The aim of the present study was to determine the correlation between the primary stability of dental implants placed in edentulous maxillae and mandibles, the bone mineral density and different histomorphometric parameters. After assessing the bone mineral density of the implant sites by computed tomography, 48 stepped cylinder screw implants were installed in four unfixed human maxillae and mandibles of recently deceased people who had bequeathed their bodies to the Anatomic Institute I of the University of Erlangen-Nuremberg for medical-scientific research. Peak insertion torque, Periotest values and resonance frequency analysis were assessed. Subsequently, histologic specimens were prepared, and bone-to-implant contact, the trabecular bone pattern factor (TBPf), the density of trabecular bone (BV/TV) and the height of the cortical passage of the implants were determined. The correlation between the different parameters was calculated statistically. The mean resonance frequency analysis values (maxilla 6130.4+/-363.2 Hz, mandible 6424.5+/-236.2 Hz) did not correlate with the Periotest measurements (maxilla 13.1+/-7.2, mandible -7.9+/-2.1) and peak insertion torque values (maxilla 23.8+/-2.2 N cm, mandible 45.0+/-7.9 N cm) (P=0.280 and 0.193, respectively). Again, no correlations could be found between the resonance frequency analysis, the bone mineral density (maxilla 259.2+/-124.8 mg/cm(3), mandible 349.8+/-113.3 mg/cm3), BV/TV (maxilla 19.7+/-8.8%, mandible 34.3+/-6.0%) and the TBPf (maxilla 2.39+/-1.46 mm-1, mandible -0.84+/-3.27 mm-1) (P=0.140 and 0.602, respectively). However, the resonance frequency analysis values did correlate with bone-to-implant contact of the oral aspect of the specimens (maxilla 12.6+/-6.0%, mandible 35.1+/-5.1%) and with the height of the crestal cortical bone penetrated by the implants in the oral aspect of the implant sites (maxilla 2.1+/-0.7 mm, mandible 5.1+/-3.7 mm) (P=0.024 and 0.002, respectively). The Periotest values showed a correlation with the height of the crestal cortical bone penetrated by the implants in the buccal aspect of the implant sites (maxilla 2.5+/-1.2 mm, mandible 5.4+/-1.2 mm) (P=0.015). The resonance frequency analysis revealed more correlations to the histomorphometric parameters than the Periotest measurements. However, it seems that the noninvasive determination of implant stability has to be improved in order to give a more comprehensive prediction of the bone characteristics of the implant site.     

A new biomechanical model for evaluation of fixation systems of maxillofacial fractures

The aim of this study was to develop a new type of biomechanical model for biomechanical researches of maxillofacial fractures and then evaluate it. Twenty synthetic polyurethane maxillary and mandibular models were used to simulate the mandible and maxilla. Springs were used to represent the forces of masseter, medial pterygoid, temporalis, and lateral pterygoid muscles acting on the models. Four masticatory conditions, namely clenching in the intercuspal position (ICP), incisal clenching (INC), left unilateral molar clenching (L-MOL, contralateral side of fracture) and right unilateral molar clenching (R-MOL, fracture side) were simulated. The strain on a miniplates placed across a simulated fracture was measured using strain gauges attached to the plate surface. During INC and L-MOL, the strain on the miniplates confirmed the findings of Champy. The upper miniplate was subjected to tension force and the lower miniplate to compression. When the bite point moved to the fracture, the tension–compression zone reversed, with the upper miniplate relatively compressed and the lower miniplate tension. During ICP, the tension–compression zone changed again, with both miniplates tension. In conclusion, we have successfully developed a model which is much closer to physiological conditions than models used previously. It is reliable and useful for biomechanical tests of mandibular fractures. Models including soft tissue need developing to further understand fracture healing biomechanics.     

两种游离端半精密附着体可摘局部义齿的应力分析

目的:研究双侧游离缺失活动义齿使用两种不同类型的半精密附着体固位时周围支持骨的表面应力。方法:采用电阻应变测量法在人体下颌骨标本上测量以冠内栓道式及冠外垂直杆式半精密附着体固位的双侧游离缺失活动)固定联合修复体的表面应力值并做统计分析。结果:冠内附着体在基牙周围牙槽骨上产生的总体应力较大,而冠外附着体在缺牙区牙槽嵴和近缺隙侧基牙远中颈部牙槽嵴上产生的应力较大。结论:冠内附着体适用于远中基牙牙周条件良好的情况,而冠外附着体则适用于缺牙区牙槽嵴条件良好、远中基牙条件相对欠佳的情况。     

Structural and radiological parameters for the characterization of jawbone

OBJECTIVES: The aim of this study was to determine the Hounsfield values of selected bone sites on a computed tomography (CT) scan of the jaw and to investigate the relationship between this radiological parameter and structural parameters. MATERIALS AND METHODS: A selection of 24 bone samples out of eight cadaver human jaws was made. The following parameters were measured: Hounsfield value in the jaw (HU1) determined by a first CT scan, Hounsfield value of the excised bone specimen (HU2) by a second CT scan, bone mineral density (BMD) by a dual-energy X-ray absorptiometry scan, bone volume (BV/TV) by the microfocus CT scan, first peak transmission time (T(US-1)) and first zero crossing transmission time (T(US-2)) by an ultrasound measurement and Young's modulus (E(MECH)) by a compression test. RESULTS: Thirteen specimens were composed of a mix of trabecular and a small amount of cortical bone, while another 11 specimens were composed of trabecular bone only. A good correlation was found between the HU value of the specimen (HU2) and BMD (rho = 0.99), BV/TV (rho = 0.97), T(US-1) (rho = -0.83), T(US-2) (rho = -0.87) and E(MECH) (rho = 0.83). For the pure trabecular bone specimens, the HU value of the excised bone specimen (HU2) was highly correlated (rho = 0.95) with the HU value of the total jaw scan (HU1). For mixed trabecular-cortical bone specimens, this relationship was weak (rho = 0.57). CONCLUSION: With the current CT scan technology, predictions of the mechanical properties of trabecular jaw bone based on Hounsfield values were only valid for jaws with a thin layer of cortical bone. For jaws with a thicker cortical layer, the prediction of the mechanical properties decreased significantly.     

Mandibular bone density and fractal dimension in rabbits with induced osteoporosis

OBJECTIVE: Our goal in this investigation was to examine the mandibular bone density and radiographic textural changes and the relationship between mandibular and spinal bone mineral density in an osteoporotic rabbit model. STUDY DESIGN: Three adult female New Zealand white rabbits in each of 4 groups received daily injections of cortisone acetate at a dosage of 0.0 (control), 3.0, 7.5, or 15.0 mg/kg for 4 weeks. The rabbits were then killed, and the mandible and spine of each animal were removed. Digital radiographs (70 kVp, 10 mA, 8 impulses) of the hemimandibles and spines were made. Lateral and anteroposterior bone densities of the lumbar spine (L2) were calculated, and average mandibular interdental bone density, fractal dimension, and gradient values were calculated. RESULTS: Correlation analysis revealed that cumulative steroid dose was strongly related to mandibular bone density (r = -0.80, P <.01), moderately related to mandibular fractal dimension (r = -0.61, P <. 05), and moderately related to anteroposterior lumbar spine density (r = -0.64, P <.05). Moderate correlations were found between mandibular interdental bone density and spinal density (r = 0.56, P <.05), but mandibular fractal dimension was not related to spinal density. CONCLUSIONS: In osteoporotic female rabbits, mandibular bone mineral density decreases in relation to spinal density and cumulative steroid dose. Mandibular fractal dimension decreases with cumulative steroid dose but is not significantly related to either mandibular density or spinal density.