基于CBCT的下颌前牙区颌骨形态学研究

[摘要]目的：利用锥形束CT（codebeamcomputedtomography,CBCT）图像研究测量下颌前牙区的颌骨形态和宽度,为临床种植手术提供治疗依据。方法：选取2011年--2013年间50名成年受试者的CBCT检查结果,利用CBCT图像对下颌前牙区颌骨外形、唇舌侧宽度、近远中距离等进行观察和测量。结果：1．下颌前牙区颌骨形态唇侧均为凹形,最凹点位于下颌骨上中份,舌侧外形多样化,凸形比例最高。2．下颌骨前牙区颌骨唇舌侧宽度在下颌骨中1／2和下颌骨下缘较宽,在牙槽嵴顶和根尖区较窄。3．左右尖牙、侧切牙、中切牙于牙槽嵴顶的近远中距离是4．46～6．94mm,尖牙最长,侧切牙次之,中切牙最小。结论：下颌前牙缺失后,尤其是下颌侧切牙或中切牙个别缺失,如行种植修复近远中距离可能不足,易损伤邻牙;植入种植体等手术时应当注意下前牙区颌骨外形,避免因倒凹导致唇舌侧穿通;CBCT可作为下颌前牙区种植手术术前的常规影像学检查手段。     

锥形束CT与根尖片对牙根纵裂诊断的对比研究

目的:比较锥形束CT(CBCT)和X线根尖片在牙根纵裂诊断中的准确度,探讨CBCT对牙根纵裂诊断的价值。方法:选取临床检查中疑似牙根纵裂患牙50例,分别进行X线根尖片、CBCT检查诊断和外科手术诊断;对X线根尖片和CBCT对牙根纵裂的诊断结果进行统计分析。结果:CBCT诊断牙根纵裂的敏感度(83.33%)高于X线根尖片诊断牙根纵裂的敏感度为(47.61%),P<0.05。结论:CBCT比X线根尖片能更准确诊断牙根纵裂,有助于牙根纵裂诊断。     

多来源颅颌面三维数字化模型的建立

目的 建立一个满足临床和科研要求的可视化的多来源多精度的颅颌面三维数字化模型.方法 采用锥体束断层CT(CBCT)扫描整个头部,利用不同组织的亨氏单位(Houns Field值)的不同,提取出面部软组织、颌面部骨骼以及牙列3种组织结构,利用三维重建的方法,重构出面部、颌骨和牙齿三部分的数字化三维模型,同时采用激光扫描的方法获得带有纹理信息的面部三维模型以及高精度三维数字化牙列模型,利用三维图形学中的配准技术,将激光扫描获得的面部、三维模型转化到CT来源的重建的三维颅颌面数字化模型所在坐标系.结果 获得一个带有颜色信息的面部软组织、高精度牙列和清晰骨骼的复合三维数字化颅颌面模型.结论 多来源的三维数字化颅颌面模型是一种能够达到临床和科研要求的高精度数字化模型.     

Root resorption diagnosed with cone beam computed tomography after 6 months of orthodontic treatment with fixed appliance and the relation to risk factors

Objectives:To investigate root resorption after 6 months of active orthodontic treatment and its relation to possible risk factors.Materials and Methods:Ninety-seven patients (10–18 years) with a Class I malocclusion and crowding treated with fixed appliance and premolar extractions were examined with cone beam computed tomography before and after 6 months of active treatment. The exposure covered all teeth from first molar to first molar in both jaws. The Malmgren index was used to evaluate the degree of root resorption. Irregular root contour (score 1) was seen in most teeth already before active treatment, and therefore resorptions were registered only as score 2 (<2 mm, minor resorption) or higher.Results:Minor root resorption was noted in 10% of the patients and severe root resorption, >2 mm (score 3) was found in four patients. Root resorption was more frequently seen in the upper jaw, especially the incisors. There was no statistically significant correlation of root resorption with any of the selected risk factors.Conclusions:After 6 months of treatment, clinically significant resorption was diagnosed in 4% of the patients, ie, in 96% of the patients the radiographic examination did not reveal any significant information. The selected risk factors did not have any impact on the amount of resorption after 6 months of active treatment.     

Comparison of root resorption between self-ligating and conventional preadjusted brackets using cone beam computed tomography

Objective:To compare the magnitude of external apical root resorption (EARR) of incisors in patients undergoing the initial phase of orthodontic treatment with two sets of brackets.Materials and Methods:According to the results of the power analysis for sample size calculation, 19 Angle Class I patients (anterior crowding: 3 to 5 mm; mean age: 20.6 years) were included in the study and randomly divided into two groups: group I (n  =  11, self-ligating brackets) and group II (n  =  8, conventional preadjusted brackets). The degree of EARR was detected in 152 upper and lower incisors by using cone-beam computed tomography (CBCT) scans and a three-dimensional program (Dolphin 11.5, Dolphin Imaging & Management Solutions, Chatsworth, Calif) with 25% level of sensitivity. The CBCT scans were obtained before (T1) and 6 months after initiation of treatment (T2). Differences between and within groups were analyzed by nonpaired and paired t-test, respectively, with 5% significance level.Results:Significant differences were found for both groups between T1 and T2. However, no differences in the degree of EARR were detected between the groups studied.Conclusions:Although EARR has occurred in all teeth evaluated, the bracket design (self-ligating or conventional) did not demonstrate any influence on the results observed.     

Analysis of ion beam teletherapy patient-specific quality assurance

The objective of this study was to evaluate the procedures for patient-specific quality assurance measurements using modulated scanned and energy stacked beams for proton and carbon ion teletherapy. Delivery records from 1734 portal measurements were analyzed using a 3-point pass criteria: more than 22 of 24 chambers in a water phantom (WP) had to have a measured dose difference from the planned portal doses less than or equal to 3%, or the distance from the measurement point location to a point location in the plan having the same dose had to be less than or equal to 3?mm (distance to agreement [DTA]), and the mean dose deviation of all chambers had to be less than 3%. Stratification of results showed some associations between measurement parameters and pass rates. For proton portals, pass rates were high at all measurement depths, but for carbon ion portals, pass rates decreased as a function of increasing measurement depth. Pass rates of both proton and carbon ion portals with 1 WP were slightly lower than those with a second WP. The total pass rates were 97.7% and 91.9% for proton and carbon ion patient portals, respectively. In general, the measured doses exhibited good agreement with the treatment planning system (TPS) calculated doses. When the chamber position was deeper than 150?mm in carbon ion beams, a lower pass rate was observed, which may have been caused by ion chamber array setup uncertainty (lateral and depth) in highly modulated portals or incorrect modeling of scatter by the TPS. These deviations need further investigation.