Mouthguards: difference in longitudinal dimensional stability between single- and double-laminated fabrication techniques

Abstract –  Though the use of mouthguards (MGs) has increased with the increase in sporting activities, little is known about the influence of their fabrication methods on longitudinal dimensional stability. The objective of this study was to compare the difference in the longitudinal dimensional stability between single and laminated MGs. Single-layer MGs were made from a 4.0 mm thick ethylene vinyl acetate (EVA) sheet and laminated MGs were made from two 2.0 mm thick sheets of EVA. MGs were kept in a 37°C water bath for 60 h, equivalent to the time period of 3-months inter-oral use. MG deformation was analyzed by measuring designated points on the MG border using a profile projector (J-12, Nikon Inc., Tokyo, Japan) before and after the water immersion. A finite-element model was also created to examine the time course of stress accumulation during the sheet forming process using Finite Element software. Longitudinal deformation was smaller in the laminated MGs than in the single-layer MGs in the anterior area ( P  < 0.05). Finite element method (FEM) analysis also showed the largest stress accumulation in the anterior incisal area where deformations were mainly observed. Laminated double layer MGs have advantages over single-layer MGs in terms of longitudinal stability due to lower stress accumulation during the fabrication process.     

Evaluation of four elastomeric interocclusal recording materials

Background: The fabrication of dental prosthesis requires the transfer of interocclusal records from patient's mouth to semiadjustable articulators using different kinds of recording media. Any inaccuracy in these interocclusal records leads to occlusal errors in the final prosthesis. This study was conducted to evaluate the dimensional changes occurring in the interocclusal recording material over a given period of time and the material's resistance to compression during the cast mounting on the articulator.     

超声波在医疗领域中的应用及分析例举

本文简要介绍了超声波的三个特点，并从诊断、治疗、辅助用途三方面论述了超声波在临床的普遍应用，其中重点介绍了三维超声成像技术。     

三维适形与简化调强放疗技术在非小细胞肺癌放疗中的剂量学比较

目的 用剂量学方法比较三维适形(3D-CRT)和简化调强放疗(sIMRT)技术用于治疗非小细胞肺癌(NSCLC)的差异.方法 选择接受放疗的10例NSCLC患者进行研究.对每例患者进行3D-CRT和sIMRT的治疗计划设计,处方剂量为60 Gy(2 Gy/次),所有计划都使95%靶区体积达到处方剂量要求.并用ADAC Pinnacle3计划系统提供的卷积或迭加算法对两种放疗技术的治疗计划进行剂量计算,比较靶区剂量分布均匀性和适形性,以及危及正常组织剂量体积直方图参数.结果 3D-CRT与sIMRT放疗计划的等剂量线和DVH相近,sIMRT计划的靶区剂量均匀性和适形性略优于3D-CRT计划,sIMRT放疗计划中肺的平均剂量、V5、V10、V20别比3D-CRT降低14.81%、17.88%、19.15%、27.78%,而食管、心脏、脊髓等危及器官的受量基本相同.结论 对于NSCLC,sIMRT放疗技术在某些方面具有3D-CRT无法替代的优势,值得在临床推广应用.     

翼腭窝的CT三维成像

目的：探讨CT三维成像评价翼腭窝解剖结构的价值。材料和方法：使用Philips Mx8000型多层CT检查仪对5个成人头颅标本进行准直1mm或0．5mm的容积采集，并将数据输入配套Mxview工作站（SGI02）进行三维重建处理，包括容积显示（VR）和三维正交多平面重建（MPR）。鼻腔内侧壁相关结构进行测量并与标本测量进行对比。结果：CT三维正交多平面重建图像可以十分清楚地显示翼腭窝结构及其6个通路结构，VR可以清楚、准确地显示鼻腔内侧壁结构，并均可以获得准确测量。结论：CT容积采集结合合理的三维重建可以直观、立体地显示翼腭窝解剖及其相关通连结构。     

Precision of three-dimensional CT-assisted model production in the maxillofacial area

Individual skull model fabrication was introduced into preoperative diagnostics in maxillofacial surgery in the mid-1980s. The aim of the present study was to collect information on the reproducibility of a skull model milled from hardened polyurethane foam. This model was based on the CT data of a real skull. Twenty comparative studies were carried out on both the model and the original skull, the model showing an average inaccuracy of 1.6 mm. The deviations ranged between 0.0 and 3.6 mm; the general trend favouring enlargements. The total deviation of the model as compared to the original skull was 1.8%. A convincing aspect of the model, which cannot be obtained by any other method, is its plasticity and the possibility of 3 D orientation on a lifesize model. This new method is already used in preoperative planning of corrections of post-traumatic defects and craniofacial deformities as well as in tumour surgery. Correspondence to: P. Solar     

多层面CT重建诊断中央大气道良性病变

目的 :分析多层面CT三维重建诊断中央大气道良性病变的价值。材料和方法 :用多层面CT对 3 5例中央气道良性病变 (解剖性异常 5例 ,炎症性病变 18例及其它 12例 )扫描 ,并全部完成三维表面遮盖显示、容积显示和仿真内窥镜检查。所有病例第一次读片时仅有横断面图像 ,第二次读片时增加重建图像。结果 :三维重建帮助 4例横断面漏误诊的解剖性异常获得确诊 ,16例炎症性病变进一步详细显示 ,2例气管支气管裂伤明确范围和程度 ;虚拟内窥镜帮助 5例横断面上不能确诊的痰液获得确诊。结论 :CT三维重建可用于解剖性异常和痰液的诊断 ,对其它良性疾病主要是对病变的另一种形式的进一步显示。     

腰椎间盘突出症CT诊断与三维瞬间牵引

目的 :探讨腰椎间盘突出症的 CT表观及三维瞬间牵引的治疗效果。材料与方法 :回顾分析经 CT及临床诊断为腰椎间盘突出症病例 16 7例的临床及 CT资料。结果 :16 7例腰椎间盘突出症表现为单个或多个椎间盘的突出 ,硬脊膜囊、硬膜外间隙及神经根受压等征象。经三维瞬间牵引后 6 5例 (38.9% )症状有不同程度缓解 ,其中 94例 (5 6 .3% )症状完全消失。结论 :CT是腰椎间盘突出症的有效诊断手段之一