In-vitro assessment of a registration protocol for image guided implant dentistry

In this study a computer aided navigation technique for accurate positioning of oral implants was assessed. An optical tracking system with specially designed tools for monitoring the position of surgical instruments relative to the patient was used to register 5 partially or completely edentulous jaw models. Besides the accuracy of the tracking system, the precision of localizing a specific position on 3-dimensional preoperative imagery is governed by the registration algorithm which conveys the coordinate system of the preoperative computed tomography (CT) scan to the actual patient position. Two different point-to-point registration algorithms were compared for their suitability for this application. The accuracy was determined separately for the localization error of the position measurement hardware (fiducial localization error-FLE) and the error as reported by the registration algorithm (fiducial registration error-FRE). The overall error of the navigation procedure was determined as the localization error of additional landmarks (steel spheres, 0.5 mm diameter) after registration (target registration error-TRE). Images of the jaw models were obtained using a high resolution CT scan (1.5 mm slice thickness, 1 mm table feed, incremental scanning, 120 kV, 150 mAs, 512 x 512 matrix, FOV 120 mm). The accuracy of the position measurement probes was 0.69 +/- 0.15 mm (FLE). Using 3 implanted fiducial markers, FRE was 0.71 +/- 0.12 mm on average and 1.00 +/- 0.13 mm maximum. TRE was found to be 1.23 +/- 0.28 mm average and 1.87 +/- 0.47 mm maximum. Increasing the number of fiducial markers to a total of 5 did not significantly improve precision. Furthermore it was found that a registration algorithm based on solving an eigenvalue problem is the superior approach for point-to-point matching in terms of mathematical stability. The experimental results indicate that positioning accuracy of oral implants may benefit from computer aided intraoperative navigation. The accuracy achieved compares well to the resolution of the CT scan used. Further development of point-to-point/point-to-surface registration methods and tracking hardware has the potential to improve the precision of the method even further. Our system has potential to reduce the intraoperative risk of causing damage to critical anatomic structures, to minimize the efforts in prosthetic modelling, and to simplify the task of transferring preoperative planning data precisely to the operating room in general.     

Novel methods for quantifying soft tissue changes after orthognathic surgery

Laser scanners are becoming increasingly important as a tool for quantifying the outcome of facial surgery. However, few computer algorithms have been developed for this purpose. Researchers have either measured the differences in the positions of (manually located) landmarks, or have taken radial measurements of the distances between surfaces. Neither of these techniques provides satisfactory information about the shape changes between surfaces. In this paper, alternative methods are proposed and their performance is compared with that of the radial method. Tests on two patients show that the Correspondences by Sensitivity to Movement (CSM) and closest point algorithms provide the most realistic measurements of the differences between two surfaces. The CSM method was found to be useful for pinpointing areas where the shape has changed.     

腮腺包块136例临床分析

目的：通过对136例腮腺包块的临床分析，提高腮腺包块的诊断水平和治疗效果。方法：对1985～2004年收治的136例腮腺包块病例进行回顾性分析。其中良性肿瘤112例，恶性肿瘤18例，其它病变6例。所有包块均行手术治疗，对恶性肿瘤术后进行放化疗。结果：128例腮腺包块经手术治愈，3例良性肿瘤及5例恶性肿瘤复发。结论：腮腺包块的正确诊断对治疗方法的选择有重要指导意义。     

正畸正颌联合治疗唇腭裂继发牙颌面畸形

目的评价正畸正颌联合治疗唇腭裂继发牙颌面畸形的疗效。方法回顾性研究2000年7月～2005年9月广东省口腔医院治疗的20例唇腭裂继发牙颌面畸形患者。20例患者均行术前及术后正畸治疗,单纯采用上颌骨LeFortⅠ型截骨前移者1例,单纯采用双侧下颌升支矢状劈开后退术者1例,行LeFortⅠ型截骨前移术 双侧下颌升支矢状劈开后退术者15例,行LeFortⅠ型截骨前移术 双侧下颌升支矢状劈开后退术 颏成型术者3例。17例患者在正颌手术前行牙槽裂植骨。结果经治疗患者上颌前移(5.5±1.2)mm,下颌后退(7.2±2.5)mm。患者唇颏关系改善明显,咬合关系良好,但大部分患者鼻部仍有塌陷及偏斜畸形。患者术前后语音状况经语音师评估均无明显变化。结论正畸正颌联合治疗唇腭裂继发牙颌面畸形,可以较好地改善患者的容貌并取得良好的咬合关系。     

正畸治疗中磨牙的拔除和保留(二十九)——拔除第一磨牙的矫治设计

目的:总结拔除第一磨牙矫治病例的设计特点.方法:46例拔除第一磨牙病例,男12例,女34例,年龄11～40岁,平均25.5岁.全部病例均采用直丝弓矫治器矫治.结果:矫治周期10～28个月,平均17个月.矫治结束时磨牙间隙完全关闭,牙根平行,上下牙列获得良好的牙尖交错关系,中线对齐,前牙覆(牙合)、覆盖正常;面型恢复理想;齿槽及牙根未见吸收现象.结论:对被动拔除的第一磨牙,目前矫治技术已经较成熟,但对于主动拔除第一磨牙矫治设计应主要针对严重的骨性畸形病例,周全考虑.     

Evaluation of accuracy of computer-aided intraoperative positioning of endosseous oral implants in the edentulous mandible

The overall accuracy of a novel surgical computer-aided navigation system for placement of endosseous implants was evaluated. Five dry cadaver mandibles were scanned using high resolution computed tomography (HRCT). The position of four interforaminal dental implants was planned on the computer screen and transferred to the cadaver mandibles using VISIT, a surgical navigation software developed at the Vienna General Hospital. The specimens were HRCT-scanned again to compare the position of the implants with the preoperative plan on reformatted slices after matching of the pre- and postoperative data sets using the mutual information technique. The overall accuracy was 0.96 +/- 0.72 mm (range 0.0-3.5 mm). No perforation of the mandibular cortex or damage to the mandibular canal occurred. We conclude that computer-aided implant surgery can reach a level of accuracy where further clinical developments are feasible.     

Cryotherapy in reducing pain,trismus, and facial swelling after third-molar surgery: Systematic review and meta-analysis of randomized clinical trials

Background

The aim of this systematic review and meta-analysis was to evaluate the efficacy of cryotherapy in reducing pain, trismus, and facial swelling in patients undergoing third-molar surgery.

拔牙诱发唇血管神经性水肿1例

血管神经性水肿为一种过敏性疾病。其发病机制属I型变态反应。过敏原可能为特定的食物、药物、肠道寄生虫、感染因子等。此外，外伤、情绪激动、寒冷等可能诱发本病^[1]。我科收治1例患儿乳牙拔除后出现唇血管神经性水肿，现报告如下。     

颌面部不对称畸形的正颌外科治疗--附44例报告

目的：探讨治疗颌面部不对称畸形的各种正颌手术方法组合。为治疗这种畸形提供临床参考。方法：回顾性随访第四军医大学口腔医学院颌面外科1987-1999年用正颌外科治疗的44例颌面部不对称性畸形患者，总结其临床疗效和经验。结果：除一例患者偏颌畸形术1年复发外，其余患者均恢复了对称的面部形态，咀嚼功能，咬合关系和咬合平面，治疗效果满意，结论：应根据患者不对称畸形的不同原因和部位制定相应的正颌治疗方案，选择不同的术式组合，同时结合关节手术可获得满意的疗效。     

A study on tooth mobility following periodontal surgery

The purpose of this study was to evaluate the quantitative changes in tooth mobility before and after periodontal surgery using a tooth mobility tester. The tester was so designed as to be able to measure the cycle of sympathetic vibrations produced when a tooth was tapped with a impact hammer. Initially the degrees of tooth mobility, which were clinically classified from 0 to 3, were observed and the mode of mobility was assessed by the tester. Then, we examined the changes of tooth mobility after flap surgery. The following is a summary of findings.