Reliability of 3D dental and skeletal landmarks on CBCT images

Objectives:To quantify reliability of three-dimensional skeletal landmarks and a comprehensive set of dental landmarks in cone-beam computed tomography (CBCT) and to determine the shapes of envelope of error.Materials and Methods:Three judges located 31 skeletal landmarks and 60 dental landmarks on the pre- and posttreatment CBCT images of 22 patients. Landmark error was determined by calculating the distance of deviation of landmark locations around their average. Standard deviation and mean radial spherical error were calculated. Scatterplots were constructed to characterize envelope of error.Results:The midline landmarks of the cranial base were highly reliable. Bilateral skeletal landmarks tended to have larger error than midline landmarks. Among the nonconventional landmarks, fronto-zygomatic suture, condyle, and mental foramen showed relatively high reliability. However, foramen spinosum and temporal fossa showed larger errors. Gonion was the least reliable landmark. Most dental landmarks were located more reliably than skeletal landmarks. The highest reliability was found at incisal edges. Mesiobuccal cusp of first molars also showed high reliability.Conclusions:There were differences in the size and shape of the distributions of errors of different landmarks. Most landmarks showed elongated envelopes. Bilateral structures tended to show greater errors than midline structures. Most dental landmarks were more reliable than skeletal landmarks.     

X线头影测量人工定点的准确性研究

目的 评价X线头影测量分析中人工定点的准确性。方法 10名口腔正畸医师对同一张X线头颅定位侧位片的29个标志点进行定位获得的数据，与对照值进行对比以衡量定点误差的大小。结果 S,Ar,U1,L1的平均误差小于1.0mm，它们均为影像轮廓清晰且容易判定的标志点；Po,Mes,Co,Gs的平均误差大于4.0mm，这些标志点均为图像轮廓的最突点。结论 人工识别时，28％的标志点存在显著差异，存在显著差异的标志点主要是某一图象轮廓的最突点。     

咽旁颞下区颈部血管体表标志及临床意义

目的 :研究确定咽旁颞下区重要结构的体表标志及对临床的指导作用。方法 :解剖新鲜尸头 6具 ,观测 12例咽旁颞下区的体表解剖标志及文献复习。结果 :骨性外耳道下内 ( 11.5± 2 .0 )mm为颈内静脉孔外壁 ,髁状突内缘距颈内动脉管外口为 ( 10 .0± 1.3 )mm ,下颌角后缘 ( 12 .0± 3 .0 )mm有颈内动脉经过 ,第一颈椎横突前 ( 5 .0± 2 .0 )mm为颈内静脉后壁。结论 :以骨性外耳道下点为A ,髁状突前点为B ,下颌角点为C ,第一颈椎横突点为D ,组成的四边形为咽旁颞下区后部重要结构的体表标志。BC线可作为咽旁颞下区前、后部的分界线。此标志对该区病变的诊断、治疗有指导意义     

上颌前牙牙冠总宽度与鼻翼宽度的相关性及临床意义

目的：对上颌前牙牙冠总宽度与鼻翼宽度的相关性及临床意义的研究。方法：选择北京地区男６１例女５５例正常合１１６例，对上前牙睡冠总宽度及鼻翼宽度进行测量，采用计算机同频模型测量系统，结果 上前牙牙冠部宽度大于鼻翼宽度。各牙弓形无显著性差异，不同性别比较有显著性差异。结论鼻翼宽测值为５．２５７－７．８９６ｍｍ，可做为全口义齿选上有牙牙冠总宽度的参考标准。     

锥形束CT三维图像上标志点可靠性的研究

目的 探讨锥形束CT三维图像中标志点定位的可靠性,以期为建立基于锥形束CT的三维头影测量方法提供依据.方法 选择二维头影测量中常用的39个标志点,4名正畸学专业研究生分别对18例正畸患者的锥形束CT资料进行标志点定位,使用SimPlant软件输出每个标志点的三维坐标,使用组内相关系数（intraclass correlation coefficients,ICC）计算每个标志点在每个维度的可靠性.结果 32个标志点三维方向的ICC＞0.9,7个标志点有一个维度0.8＜ICC＜0.9,其他两个维度的ICC＞0.9.结论 本项研究测量的39个标志点中,32个标志点三维方向可靠性高,可以根据这些标志点来进行三维头影测量.     

多平面辅助定位法提高颅颌面三维CT测量准确性的研究

目的:建立一种较准确的三维头影测量定点方法,为面部不对称畸形的临床三维测量打下基础。方法:采用螺旋CT系统,对10例面部不对称畸形患者进行全头颅扫描,并进行CT影像三维重建,描绘测量16个相关解剖标志点。采用SAS8.02软件进行直线相关性和零截距直线回归分析,得到各标志点三维坐标的直线相关系数和零截距直线回归系数。结果:16个标志点的48个三维坐标数据的直线相关系数r、零截距直线回归系数b都在0.99000～1.01000以内。结论:本研究采用的三维测量方法具有较高的准确性和可重复性。该套定位要求及标志点,可以为面部不对称患者的硬组织形态特征改变研究提供参考。     

九江地区正常(牙合)青年颅面部硬组织线性测量距离与咬合垂直距离相关性研究

目的:分析咬合垂直距离(occlusal vertical dimension,OVD)与颅颌面相关测量线距的相关性.方法:按正常(牙合)标准筛选出57名志愿者进行头影测量分析,采用Winceph 8.0测量软件进行描点和测量.结果:ANS-Me的平均值为64.50±4.18(95％ CI:63.39 ～65.61)；ANS-Me分别与S-N、N-ANS、ANS-PNS之间均存在显著性线性相关关系(P≤0.05)；偏相关分析结果ANS-Me与N-ANS、ANS-PNS依然存在显著性相关(P≤0.05),而ANS-Me与S-N则无显著性相关(P＞0.05).结论:九江地区青年正常(牙合)者的N-ANS、ANS-PNS可以作为临床确定咬合垂直距离的参考指标.     

Are collimated low-dose digital radiographs valid for performing Delaire's architectural analysis?

Computed radiography (CR) provides the dynamic exposure range to reveal objects in film areas exposed by very low X-ray exposure. Conventional cephalometric radiographs are normally beam limited to the facial skeleton. The cranial vault and cervical vertebra are collimated and only exposed by extra-focal radiation and scatter. We hypothesize that, on conventional cephalometric radiographs obtained with CR, image data of collimated film areas can be enhanced for reliable performance of Delaire's cephalometric analysis of the entire skull. Therefore the aim of the present study was to compare the reproducibility of landmark placement on normal and underexposed film areas of CR images. Intra- and inter-observer reproducibility of landmark identification was evaluated on 200 randomly selected radiographs by calculating the error radius of repeated landmark placements. A paired-samples t-test revealed differences (P< 0.001) between intra- and inter-observer reproducibility. Intra-observer accuracy was influenced (P< 0.001) by variability of suture obliteration (bregma). Identification of landmarks in areas of extra-focal radiation showed no difference (P> 0.05) from that of landmarks inside the normally exposed area. CR offers the opportunity to perform of a full cranial analysis on a cephalometric radiograph collimated to the facial region.     

Identification of ‘Point A’ as the prevalent source of error in cephalometric analysis of lateral radiographs

Deviations in measuring dentofacial components in a lateral X-ray represent a major hurdle in the subsequent treatment of dysgnathic patients. In a retrospective study, we investigated the most prevalent source of error in the following commonly used cephalometric measurements: the angles Sella-Nasion-Point A (SNA), Sella-Nasion-Point B (SNB) and Point A-Nasion-Point B (ANB); the Wits appraisal; the anteroposterior dysplasia indicator (APDI); and the overbite depth indicator (ODI). Preoperative lateral radiographic images of patients with dentofacial deformities were collected and the landmarks digitally traced by three independent raters. Cephalometric analysis was automatically performed based on 1116 tracings. Error analysis identified the x-coordinate of Point A as the prevalent source of error in all investigated measurements, except SNB, in which it is not incorporated. In SNB, the y-coordinate of Nasion predominated error variance. SNB showed lowest inter-rater variation. In addition, our observations confirmed previous studies showing that landmark identification variance follows characteristic error envelopes in the highest number of tracings analysed up to now. Variance orthogonal to defining planes was of relevance, while variance parallel to planes was not. Taking these findings into account, orthognathic surgeons as well as orthodontists would be able to perform cephalometry more accurately and accomplish better therapeutic results.     

计算机辅助颈椎分析系统识别颈椎标志点的准确性和重复性探讨

目的：探讨计算机辅助颈椎分析系统（CACVA,Computer Aided Cervical Vertebra Analysis）半自动识别颈椎标志点的准确性及重复性。方法：随机选取口腔正畸门诊青少年患者常规拍摄的X线头颅侧位定位片120张,由专家组、正畸初学者组、计算机辅助颈椎分析组定点第2～5颈椎体的27个标志点,各组分别定点三次,比较三组之间定点的准确性和组内重复性。专家组和初学者组采用手工定点,CACVA组采用快速行进算法和抛物线拟合来分割颈椎图像,通过多段曲线拟合的方法对颈椎骨边缘拟合,进而计算出标记点。随机区组方差分析及两两比较进行三组定点准确性和重复性的比较。结果：从定点准确性来看,CACVA组与专家组差异无显著性（P〉0.05）,计算机辅助颈椎分析组与初学组、专家组和初学组差异均有显著性（P〈0.05）;从定点重复性来看,CAVCA组优于专家组和初学组。结论：CAVCA组与专家组手工定点具有同样的准确性,同时具有重复性好,简便快速的优势,值得正畸临床和科研推广。     

Development of a three‐dimensional imaging system for analysis of facial change

The objective of this report is to present facial changes produced by the Twin Block appliance in three‐dimensional visual and numerical formats. Using a C3D system, stereophotogrammetric records were made of two children with Class II division 1 malocclusions prescribed treatment with a Twin Block appliance. Three‐dimensional images of their faces were captured. Comparison of specified regions of the three‐dimensional images was made using landmark identification and superimpositions. In addition to obvious visual evidence, numerical data in the form of surface area measurements were also generated. The three‐dimensional, C3D, system, provides a flexible imaging tool which should become increasingly useful as more improvements are made.     

Oral cancer: molecular technologies for risk assessment and diagnosis

Purpose: The effective biomarkers related to diagnosis, metastasis, drug resistance and irradiation sensitivity of oral cancers will help the pathologist and oncologist to determine the molecular taxonomy diagnosis and design the individualization treatment for the patients with oral cancers.     

柠檬精油对牙周致病菌抑制作用及其安全性初步研究

目的:探讨柠檬精油对牙周致病菌的体外抗菌活性及对细胞增殖的影响。方法:采用微量液体稀释法测定柠檬精油对Pg、Fn、Aa、Pi的最小抑菌浓度(minimal inhibitory concentration,MIC)及最小杀菌浓度(minimum bactericidal concentration,MBC);以较低浓度的MIC为标准稀释LEO作为实验组,采用MTT法测定柠檬精油对HUVECs的毒性作用,明确抑菌浓度下LEO的安全性。结果:柠檬精油对牙周主要致病菌均有抑菌作用,Pg、Fn、Aa、Pi的MIC分别是9.0 g/L、4.5 g/L、4.5 g/L、9.0 g/L,Aa、Fn的 MBC是9.0 g/L,Pg、Pi的MBC未测得。1/2MIC、1/20MIC浓度的LEO能够抑制人脐静脉内皮细胞的生长,而低于1/200MIC浓度的LEO则对人脐静脉内皮细胞的生长没有影响,其中1/200MIC浓度的LEO作用明显优于0.02%的CHX。结论:体外环境中,柠檬精油对牙周致病菌Pg、Fn、Aa、Pi具有抗菌活性,低浓度应用对机体相对安全。     

Stimulated whole saliva components in children with Down syndrome

The authors report on the components of stimulated whole saliva from children with Down syndrome—including pH, flow rate, sialic acid and protein concentrations, and amylase and peroxidase activity. Saliva samples were collected from 35 children aged 6–10 years. Of the participants, 17 had Down syndrome and 18 did not. To stimulate saliva production, the children chewed a piece of parafilm for 10 minutes before the sample was collected. Soon after collecting the saliva sample, the authors measured pH using a portable pH-meter. Sialic acid levels were determined with a thiobarbituric acid assay. Protein content was determined with Folin's phenol reagent. Amylase was assayed and the authors measured the maltose produced by the breakdown of starch and peroxidase using ortho-dianisidine.
No statistically significant difference was observed in levels of sialic acid (free and total) between the two groups. Protein concentration was about 36% higher in the group with Down syndrome. However, the salivary flow rate, pH, and amylase and peroxidase activities were lower among the children with Down syndrome.     

Computer-assisted planning for maxillofacial prosthodontic rehabilitation

Computerized tomography (CT) planning and the use of CT derived surgical templates for implant placement have shown promise for restoring function within months after surgical reconstruction of acquired post-oncologic defects.