Dental alloys and magnetic resonance imaging

The aim of this review article is to describe the behaviour of dental alloys during the magnetic resonance imaging procedure. Mechanical and physical effects of a high frequency magnetic field are discussed. They may cause a movement or heating of metal objects present in the body, which can lead to a potential health risk for patients undergoing this examination. Metal objects with positive magnetic properties can influence magnetic resonance scans and the results of this procedure. Such negative effects are documented in experiments, theoretical studies and articles evaluating clinical trials. The safety of magnetic resonance and the compatibility of dental alloys must always be considered prior to the magnetic resonance imaging procedure.     

Assessment of repeatability and reproducibility of mental and panoramic mandibular indices on digital panoramic images

OBJECTIVES: To evaluate the repeatability and reproducibility of the measurements for Mental Index (MI) and Panoramic Mandibular Index (PMI) on digital panoramic images. METHODS: In this study, measurements for MI and PMI were carried out independently by two oral and maxillofacial radiologists on twenty digital panoramic images. Each observer repeated the measurements after a period of approximately one week. Paired t-tests and Pearson correlation coefficients were calculated to assess the levels of association. RESULTS: All measurements, both within and between observers, demonstrated high correlations and intraobserver agreement was higher than interobserver agreement according to Pearson correlation coefficients (P<0.01). There was no statistically significant difference according to t-test (P<0.05). CONCLUSIONS: This study has shown that digital panoramic radiographs may be used to evaluate PMI and MI. Reproducibility and repeatability of digital panoramic images were found to be high for measurements of PMI and MI. Additionally, as measuring tool, this software is easy and practical to use and may be preferable for validation of radiomorphometric indices.     

Ex Vivo Detection of Apical Delta in Premolars: A Comparative Study Using Periapical Radiography,Cone-beam Computed Tomography,and Micro–computed Tomography

Introduction

Imaging methods are essential for the correct identification of root canal anatomy, which is a key factor for successful endodontic therapy. This study aimed to evaluate the performance of periapical radiography (PR) and cone-beam computed tomographic (CBCT) imaging in identifying the apical delta (AD) using micro-computed tomographic imaging as the gold standard.

Brain activation patterns during unilateral premolar occlusion

Objective: To observe the characteristics of brain activation during unilateral premolar occlusion.

Methods: Functional magnetic resonance imaging was collected from 10 healthy volunteers during occlusion of the left first premolar (L1), left second premolar (L2), and right first premolar (R1). The brain activation patterns were analyzed, and the primary sensorimotor cortex, supplementary motor area, insula, thalamus, and prefrontal cortex were chosen as regions of interest.

Results: Single premolar occlusion activated the precentral gyrus, postcentral gyrus, cerebellum, thalamus, frontal lobe, hippocampus, cingulate gyrus, and parietal lobe. The brain areas showing activation during single premolar occlusion were similar to those activated by chewing. The activation pattern of L1 was more similar to that of L2 than R1. No significant left and right hemisphere differences in signal intensity were detected within the regions of interest.

Conclusion: Brain activation patterns from two ipsilateral premolars were more similar than the pattern from a contralateral premolar.     

The correlation of DIFOTI to clinical and radiographic images in Class II carious lesions

BACKGROUND: The authors conducted a study to evaluate the correlation between digital imaging fiber-optic transillumination (DIFOTI) (KaVo Dental, Lake Zurich, Ill.) and clinical and radiographic images in estimating the true clinical axial extension of Class II carious lesions. METHODS: The authors examined 51 Class II carious lesions visually, imaged them by means of DIFOTI and radiographed them with D-speed film and a complementary metal oxide silicon (CMOS)-based digital radiographic sensor. They validated axial extension of the lesions clinically. They compared the clinical and radiographic depths of the carious lesion with the size of the lesion on the DIFOTI images. RESULTS: The authors detected 84 percent of the lesions with DIFOTI, and 82 percent showed a visible dark shadow under the marginal ridge when examined clinically. DIFOTI correlated significantly with the clinical depth of decay (Pearson r = 0.43189). The combination of a CMOS digital sensor and DIFOTI (R2 = 0.7210) provided readings closer to the clinical measures than did the combination of D-speed film and DIFOTI (R2 = 0.6215). CONCLUSIONS: DIFOTI images correlated with clinical depth, especially in smaller lesions, and improved the estimation of lesion size when used in conjunction with the CMOS digital sensor and D-speed images. CLINICAL IMPLICATIONS: Using radiographs in combination with DIFOTI images could help clinicians determine the presence and, to some extent, the size of proximal caries, especially in smaller lesions.     

Early morphogenesis of heterodont dentition in minipigs

The minipig provides an excellent experimental model for tooth morphogenesis because its diphyodont and heterodont dentition resemble that of humans. However, little information is available on the processes of tooth development in the pig. The purpose of this study was to classify the early stages of odontogenesis in minipigs from the initiation of deciduous dentition to the late bell stage when the successional dental lamina begins to develop. To analyze the initiation of teeth anlagens and the structural changes of dental lamina, a three-dimensional (3D) analysis was performed. At the earliest stage, 3D reconstruction revealed a continuous dental lamina along the length of the jaw. Later, the dental lamina exhibited remarkable differences in depth, and the interdental lamina was shorter. The dental lamina grew into the mesenchyme in the lingual direction, and its inclined growth was underlined by asymmetrical cell proliferation. After the primary tooth germ reached the late bell stage, the dental lamina began to disintegrate and fragmentize. Some cells disappeared during the process of lamina degradation, while others remained in small islands known as epithelial pearls. The minipig can therefore, inter alia, be used as a model organism to study the fate of epithelial pearls from their initiation to their contribution to pathological structures, primarily because of the clinical significance of these epithelial rests.     

多发性硬化型脊髓炎MRI研究进展

脊髓炎是一种脊髓炎性病变导致运动、感觉及自主神经功能障碍的综合征,常常给患者带来不同程度的残疾,其主要包括疾病相关性脊髓炎和特发性横贯性脊髓炎。临床中对多发性硬化(multiple sclerosis,MS)型脊髓炎的诊断存在一定的困难,但随着神经高级影像学的快速发展,MRI已成为MS型脊髓炎诊断的重要手段。现就MS型脊髓炎MRI研究进展进行综述。     

三维真实重建反转恢复磁共振成像在梅尼埃病内耳淋巴造影中的诊断价值

目的对比分析钆喷酸葡胺(Gadolinium-diethylene triamine pentaacetic acids,Gd-DTPA)增强的三维液体衰减反转恢复(three-dimensional fluid-attenuated inversionrecovery,3D FLAIR)与三维真实重建反转恢复(three-dimensional real inversionrecovery,3D real IR)磁共振成像(magnetic resonance imaging,MRI)在梅尼埃病内耳内淋巴积水中的诊断价值。材料与方法回顾性分析29例梅尼埃病患者,男10例,女19例,年龄22~71岁,12例为双侧耳发病,17例为单侧耳发病,共患侧耳41只。29例患者均经咽鼓管向中耳鼓室内注入Gd-DTPA稀释液,24 h后行3D FLAIR序列及3D realIR序列MRI内耳造影,在两种序列图像上分别定量测量前庭最大切面及穿过窝轴的耳蜗底旋短轴切面的内淋巴间隙与总淋巴间隙面积比值R(前庭为RV,耳蜗为RC)及定性评估相应内淋巴积水分级G (前庭为GV,耳蜗为GC),比较两组扫描序列图像所测得的RV、RC、GV及GC的差异。结果 29例梅尼埃病患者41只患侧耳中,3D FLAIR与3D real IR两种序列所测得的RV、RC、GC及GV均具有统计学差异性(PRV=0.000,PRC=0.000,PGV=0.000,PGC=0.001),3D real IR序列测得的RV及RC值大于3D FLAIR序列测得值,GV及GC达1~2级(即发现内淋巴积水)患耳数量大于3D FLAIR序列。结论相比于3D FLAIR序列,3D real IR序列内耳造影对于梅尼埃病患者内耳内淋巴积水的检测更敏感,检出率更高。     

单指数、双指数、拉伸指数模型DWI在胶质瘤术前分级中的应用

目的探讨单指数、双指数、拉伸指数模型扩散加权成像(diffusion weightedimaging,DWI)对胶质瘤术前分级的诊断性能,评价灌注参数与血流量(cerebral bloodflow,CBF)的相关性。材料与方法收集经手术病理证实为脑胶质瘤的病例34例,包括低级别17例,高级别17例。受试者术前均行常规扫描、3D动脉自旋标记成像(threedemensional arterial spin labeling,3D ASL)及多b值DWI序列扫描,利用FUNCTIONTOOL后处理软件中的单指数模型计算得到表观扩散系数(apparent diffusion coefficient,ADC),利用双指数模型得到D、D*、f值,利用拉伸指数模型得到分布扩散系数(distribute diffusion coefficient,DDC)、水分子各向异性(alpha,α),利用3D ASL后处理软件得到CBF值。所得各参数利用SAS9.4统计软件进行分析。结果高级别胶质瘤ADC、D、f、DDC、ɑ值低于低级别胶质瘤,D*值高于低级别胶质瘤,P值均<0.05;全部胶质瘤D*与CBF呈正相关(r=0.51,P<0.05);受试者工作特性(receiver operatingcharactsteristic,ROC)曲线分析得出:ɑ、D、DDC、ADC值的曲线下面积(area undercurve,AUC)分别为0.969、0.965、0.961、0.957,其诊断阈值分别为0.88×10^-3mm^2/s、0.86×10^-3mm^2/s、1.10×10^-3mm^2/s、1.11×10^-3mm^2/s。结论单指数、双指数、拉伸指数模型DWI为胶质瘤术前提供更多诊断信息,ɑ、D、DDC、ADC值在鉴别高、低级别胶质瘤均有较高价值,且灌注参数D*与CBF呈正相关。