特殊涉核环境人员黄斑区厚度研究

目的 探讨特殊涉核环境人员与普通环境非涉核人员黄斑区厚度的差异性。方法 在某基地年度体检时为特殊涉核环境人员（简称涉核人员）与普通环境非涉核人员（简称非涉核人员）增加眼科光学相干断层扫描（Optical coherence tomography，OCT）检查，测量黄斑区厚度值，每人测量3次，按照体检表末尾编号随机抽取204例编号为奇数的涉核人员和105例非涉核人员，取3次测量值的平均值进行比较。结果 涉核人员与非涉核人员两组年龄均值为（29.40 ±6.16）岁、（28.92 ±6.71）岁，P = 0.5325，无统计学差异。两组人员视力均值：涉核人员为（1.04 ±0.03）（右），（1.05 ±0.03）（左），非涉核人员为（1.00 ±0.05）（右），（1.02 ±0.05）（左），P = 0.5006（右），P = 0.5962（左），无统计学差异。涉核人员黄斑区厚度均值：（212.9 ±1.3） μm（右），（205.5 ±1.1） μm（左），P < 0.0001，两者比较差异有统计学意义；非涉核人员黄斑区厚度均值：（223.2 ±2.5） μm（右），（211.7 ±2.4） μm（左），P < 0.0001，两者比较有统计学差异。对涉核人员与非涉核人员右眼及左眼黄斑区厚度均值进行比较，P = 0.0003（右），P = 0.0217（左），均有统计学差异。结论 非涉核人员黄斑区厚度要厚于涉核人员。与涉核人员特殊工作环境中较多使用LED光源可能存在关联；其他因素包括涉核、气压、氧分压及人员的心理状态需要进一步的试验进行证明。     

Monolithic crowns fracture analysis: The effect of material properties,cusp angle and crown thickness

ObjectivesThis study aimed to investigate the collective influence of material properties and design parameters on the fracture behavior of monolithic dental crowns.MethodsThree-dimensional (3D) models (N = 90) with different combinations of design parameters (thickness, cusp angle and occlusal notch geometry) and material type (lithium disilicate, feldspar ceramic, zirconia, hybrid resin ceramic and hybrid polymer-infiltrated ceramic) were developed for the failure analysis using extended finite element method (XFEM) to identify the stress distribution, crack initiation load, fracture surface area and fracture pattern. Analytical formulation, in vitro fracture tests and fractographic analysis of dedicated models were also performed to validate the findings of the XFEM simulation.ResultsFor all material types considered, crowns with a sharp occlusal notch design had a significantly lower fracture resistance against occlusal loading. In most of the models, greater crown thickness and cusp angle resulted in a higher crack initiation load. However, the effect of cusp angle was dominant when the angle was in the low range of 50° for which increasing thickness did not enhance the crack initiation load.SignificanceComparing the critical load of crack initiation for different models with the maximum biting force revealed that for the studied monolithic materials excluding zirconia, a design with a rounded occlusal notch, 70° cusp angle and medium thickness (1.5 mm occlusal) is an optimum combination of design parameters in terms of tooth conservation and fracture resistance. Zirconia crowns exhibited sufficient strength for a more conservative design with less thickness (1.05 mm occlusal) and sharper cusp angle (60°).     

Ultrasound evaluation of the quadriceps muscles in pronated foot posture

ObjectiveThe main goal of this study was to investigate the size of all portions of the quadriceps muscles in individuals with pronated foot posture compared to normal foot posture using ultrasound imaging.DesignTwenty nine females with pronated foot posture and 29 age-, body weight-, body height-matched females with normal foot posture were recruited from university communities. The muscle thicknesses of the rectus femoris (RF), vastus medialis (VM), vastus medialis oblique (VMO), vastus lateralis (VL) and vastus intermedius (VI) were measured using ultrasound imaging.ResultsThe thicknesses of the RF and VMO were significantly smaller in individuals with pronated foot posture compared to normal foot posture (p < 0.05). No significant differences were observed in the VM, VL, and VI muscle thicknesses in both groups.ConclusionBased on the results of the present study, it seems that besides the foot and lower leg muscles, an integrated assessment of proximal knee muscles, especially quadriceps, is required in individuals with pronated foot posture.     

Prévalence et facteurs déterminants de l’épaisseur intima-media carotidienne élevée dans une population de 1203 hypertendus noirs africains

ObjectivesTo evaluate the prevalence and determinants of increased carotid intima-media thickness (IMT) in a population of black hypertensive patients and it influence of on the assessment of their overall cardiovascular risk.Patients and methodsThis was a 16-month, cross-sectional study conducted in the outpatient unit of the cardiology department of the Campus teaching hospital of Lome, and included 1203 hypertensive patients, both sexes, aged 35 years and more. Each patient benefited from a carotid IMT measure. Carotid IMT was increased if it was > 0.9 mm and the plaque was defined as a carotid IMT > 1.2 mm.ResultsThe mean age of our patients was 53.3 ± 10.4 years with a sex ratio of 1.6 in favor of women. The duration of hypertension was less than 5 years in 56.7% and hypertension was grade 1 in 47.7% of cases. The mean carotid IMT was 0.89 mm ± 0.20. The prevalence of the increased carotid IMT was 45.8% and that of an atheroma plaque was 15.8%. Carotid IMT was correlated with age (P ˂ 0.0001), duration of arterial hypertension (P = 0.01), history of stroke (P ˂ 0.0001), and presence of left ventricular hypertrophy to cardiac ultrasound (P = 0.01). The overall cardiovascular risk was modified after taking into account the carotid IMT. An increase in cardiovascular risk was observed in 30.5% of hypertensive patients.ConclusionIncreased carotid intima-media thickness is frequent in Togolese hypertension. The determining factors are age, duration of arterial hypertension, left ventricular hypertrophy and stroke. The systematic measurement of the carotid intima-media thickness would better evaluate the overall cardiovascular risk for our patients.     

锥形束CT测量牙龈厚度准确性的初步研究

目的评价锥形束CT(CBCT)法测量牙龈厚度的可信度及准确性。方法选择20例牙龈健康者的120颗上颌前牙,采用CBCT法和牙龈穿刺法测量唇侧中央龈缘下2mm处牙龈厚度,比较两组差异并用Kappa系数评价两种方法的一致性;应用Kappa系数评价不同检查者用CBCT法测量牙龈厚度的一致性,以及组内相关系数ICC评价同一检查者重复测量数据的可信度。结果CBCT法测量牙龈厚度为(1.23±0.27)mm,牙龈穿刺法测量结果为(1.24±0.26)mm,差异无统计学意义(P>0.05),两组之间一致率为83.33%(Kappa=0.547)。不同的检查者CBCT法测量牙龈厚度的一致性检验Kappa系数为0.814,可信度良好(ICC=0.795),同一检查者CBCT法重复测量数据之间一致性检验Kappa系数为0.864,可信度良好(ICC=0.893);CBCT法对厚牙龈生物型具有高的灵敏度(92.05%)和低的特异度(59.38%)。结论CBCT测量牙龈厚度的结果与牙龈穿刺法的结果较一致,具有良好的可信度。     

Anthropometric analysis of maxillary anterior buccal bone of Korean adults using cone-beam CT

PURPOSE

The aim of this study was to evaluate the thickness of buccal and palatal alveolar bone and buccal bony curvature below root apex in maxillary anterior teeth of Korean adults using Cone-beam CT images.

MATERIALS AND METHODS

The 3D image was reconstructed with dicom file obtained through CBCT from 20 - 39 year old Korean subjects (n = 20). The thickness of buccal and palatal plate, root diameter, the buccal bony curvature angle below root apex and the distance from root apex to the deepest point of buccal bony curvature were measured on maxillary anterior teeth area using OnDemand3D program.

RESULTS

Mean thickness of buccal plate 3 mm below CEJ was 0.68 ± 0.29 mm at central incisor, 0.76 ± 0.59 mm at lateral incisor, and 1.07 ± 0.80 mm at canine. Mean thickness of palatal plate 3 mm below CEJ was 1.53 ± 0.55 mm of central incisor, 1.18 ± 0.66 mm of lateral incisor, 1.42 ± 0.77 mm of canine. Bucco-lingual diameter 3 mm below CEJ was 5.13 ± 0.37 mm of central incisor, 4.58 ± 0.46 mm of lateral incisor, and 5.93 ± 0.47 mm of canine. Buccal bony curvature angle below root apex was 134.7 ± 17.5° at central incisor, 151.0 ± 13.9° at lateral incisor, 153.0 ± 9.5° at canine. Distance between root apex and the deepest point of buccal bony curvature of central incisor was 3.67 ± 1.28 mm at central incisor, 3.90 ± 1.51 mm at lateral incisor, and 5.13 ± 1.70 mm at canine.

CONCLUSION

Within the limitation of this study in Korean adults, the thickness of maxillary anterior buccal plate was very thin within 1mm and the thickness of palatal plate was thick, relatively. The buccal bony curvature below root apex of maxillary central incisor was higher than that of lateral incisor and canine and it seems that the buccal bony plate below root apex of central incisor is most curved.     

硅溶胶的浓度对磷酸盐包埋料性能的影响

目的 评价硅溶胶浓度对包埋料性能的影响。方法 分别使用SiO2含量为0％、10％、20％、30％、40%的硅溶胶调拌包埋同一包埋料，检测气孔率、抗压强度、凝固膨胀率和热膨胀率．并包埋铸造100个钴铬合金帽状修复体，检测边缘浮出量。结果 当硅溶胶的浓度小于20％时，随着硅溶胶浓度的提高，凝固膨胀和热膨胀明显增大，铸件的边缘浮出量明显减小；当硅溶胶浓度在20％-40％时，随着硅溶胶浓度的提高，抗压强度明显增大，铸件的边缘浮出量变化不大。结论 使用SiO2含量为30％左右的硅溶胶所得的包埋料各方面性能都较优良，建议使用30％左右的硅溶胶。     

第一磨牙牙釉质及牙本质厚度测量研究

目的:了解上下颌第一磨牙牙釉质及牙本质的厚度。方法:用电子测量尺测量23颗上颌第一磨牙和18颗下颌第一磨牙牙合面不同部位牙釉质、牙本质的厚度。结果:牙合面突起结构组织厚度(牙釉质:上颌(1.36±0.27)mm,下颌(1.61±0.27)mm;牙本质:上颌(4.13±0.40)mm,下颌(4.2±0.47)mm大于各自牙合面凹形结构上颌(0.92±0.42)mm,下颌(1.12±0.38)mm;牙本质:上颌(3.15±0.42)mm,下颌(3.32±0.30)mm,P<0.05),下颌牙釉质厚度多大于上颌(P<0.01),但牙本质厚度无此差异(P>0.05)。结论:上下颌第一磨牙硬组织厚度在合面不同结构之间以及上下牙同名部位之间存在不同程度的差异。     

Influence of thermal gradients on stress state of veneered restorations

Objectives

To assess transient and residual stresses within the porcelain of veneered restorations (zirconia and metal) as a result of cooling rate and porcelain thickness.

Methods

Porcelain-on-zirconia (PZ) and porcelain-fused-to-metal (PFM) crowns were fabricated with 1 or 2 mm of porcelain. Thermocouples were attached both internally and externally to the crowns to record transient temperatures. For fast cooling, the furnace was opened after the holding time and switched off. Slow cooling was accomplished by opening the furnace at 50 °C below the glass transition temperature (T_g) of the material. An axially symmetric FEA model simulated thermal stresses. Time-dependent temperature equations from thermocouple readings were set as boundary conditions. Framework materials and the porcelain below T_g were considered to behave elastically. Visco-elastic behavior was assumed for porcelain above the T_g modeling properties as dependent on cooling rate.

Results

Differences in residual stress were found for fast and slow cooled PZ and PFM crowns. Significant transient stress waves were observed within the porcelain when fast cooling through T_g. They are believed to be related to non-uniform volumetric changes originated from thermal gradients. Results were confirmed by modeling and physical testing of crowns containing a defect.

Significance

Residual stresses do not distinguish PZ from PFM. High magnitude transient stresses observed within the porcelain during fast cooling may explain clinical fractures involving internal defects. Stress waves may also originate internal micro-cracking which could grow under function. Therefore, slow cooling, especially for all-ceramic crowns with thick porcelain, is important to prevent thermal gradients and high-magnitude transient stresses.