Increased apical enlargement contributes to excessive dentin removal in curved root canals: a stepwise microcomputed tomography study

Introduction

To determine whether increased apical enlargement would result in a complete preparation of curved canals and to progressively assess shaping quality using multiple microcomputed tomography (MCT) scans.

Methods

Ninety root canals with a curvature of 25° to 50° were selected. Five MCT scans, 1 preoperative and 4 postoperative, were acquired from each canal. Canal preparation was performed up to size 50 using 3 techniques, nickel-titanium (NiTi) hand files, Mtwo (VDW, Munich, Germany), and ProTaper (Maillefer, Ballaigue, Switzerland), by experienced operators in a dental mannequin so as to simulate the clinical conditions. At a level of 1 mm short of the working length, 2 parameters were evaluated in each of the 4 postoperative acquisitions: the percentage of the prepared outline and the amount of dentin removed (the prepared area).

Results

Statistically, there was no significant difference between the 3 systems used regarding the prepared outline. The maximum prepared outline was achieved by the use of NiTi hand files (63%; confidence interval [CI], 54%–73%), whereas Mtwo and ProTaper amounted to 58% (CI, 50%–66%) and 60% (CI, 51%–70%), respectively. In contrast, the dentin area removed by ProTaper was significantly higher than that of Mtwo and NiTi hand files.

Conclusions

Increased apical enlargement of curved canals did not result in a complete apical preparation, whereas it did lead to the unnecessary removal of dentin.     

18F-FDG PET显像在头颈肿瘤诊断中的作用评价

目的:比较~(18)F脱氧葡萄糖正电子发射体层显像(~(18)F-FDG PET)与CT/MRI检查在头颈肿瘤诊断中的应用价值。方法:54例头颈肿瘤患者在术前2周分别进行PET与CT、MRI检查,以病理结果为金标准,分析2种方法在敏感度、特异度及准确率方面的差异,采用SPSS13.0软件包对数据进行X~2检验。结果:PET和CT、MRI分别准确判断了54例肿瘤中的48和43例,PET在敏感度、特异度及准确率方面分别比CT、MRI高7.4%、15.3%和9.3%,但差异均无显著性。结论:PET在头颈肿瘤诊断的敏感度、特异度及准确率方面优于CT、MRI,但结果无统计学差异。     

数字化影像技术在牙周临床诊疗中的应用

 影像技术是牙周病和种植体周围病的重要辅助检查手段，随着数字化技术的发展，数字化影像技术不仅使牙周病和种植体周围病的检查和诊断越来越快捷、准确，而且在治疗计划的设计和疗效评价中扮演着越来越重要的角色。文章将对数字化影像技术在牙周临床诊治中的应用及进展进行简要介绍。     

A reconstructed computerized tomographic comparison of Ni-Ti rotary GT files versus traditional instruments in canals shaped by novice operators

AIM: The aim of this study was to compare the effects of preparation with conventional stainless steel Flexofiles and Gates Glidden burs versus nickel-titanium GT rotary files in the shaping of mesial root canals of extracted mandibular molars. METHODOLOGY: A total of 54 canals from 27 mesial roots of mandibular molar teeth were prepared using one of two methods by novice dental students. One canal in each root was prepared by a crown-down approach. utilizing stainless steel Flexofiles and Gates Glidden burs. The other canal was prepared using nickel-titanium GT rotary files in a crown-down fashion as recommended by the manufacturer. Preoperative CT scans of each root were recorded and 50 canal specimens were available for postoperative comparisons. Following canal shaping, postoperative scans were superimposed on the original images. Changes in canal area, canal transportation and thickness of remaining root structure at strategic levels of the root were analyzed. The time taken for each method was also noted. RESULTS: At the coronal and mid-root coronal one-third sections, the rotary GT files produced a significantly smaller postoperative canal area (P < 0.05). In the mid-root sections there was significantly less transportation of the root canal toward the furcation, and less thinning of the root structure with GT files compared to the stainless steel files (P < 0.05). Overall, there was greater conservation of structure coronally and more adequate shape in the mid-root level. The GT rotary technique was significantly faster than the stainless steel hand-held file technique (P < 0.0001). Two GT instruments fractured during the study. CONCLUSIONS: Under the conditions of this study, novice dental students were able to prepare curved root canals with Ni-Ti GT rotary files with less transportation and greater conservation of tooth structure, compared to canals prepared with hand instruments. The rotary technique was significantly faster.     

Shaping ability of reciprocating motion in curved root canals: a comparative study with micro-computed tomography

Introduction

Recently, root canal shaping with reciprocating motion has been postulated to reduce the possibility of unexpected file fractures. However, there has been little information on the shaping capability of this reciprocating motion preparation technique. Therefore, the purpose of this study was to evaluate the shaping ability of reciprocating motion when compared with continuous rotation motion in curved root canals.

Methods

The mesiobuccal and distobuccal canals of 20 extracted maxillary molars with curvatures of 20-45 degrees were instrumented with a series of ProTaper rotary files. The canals in the continuous rotation motion (CM) group (n = 20) were prepared by using continuous rotation with pecking motion, whereas the canals in the reciprocating motion (RM) group (n = 20) were prepared with reciprocating motion (clockwise 140 degrees and counterclockwise 45 degrees). Basic geometric parameters such as curvature, root canal volume, surface area, and structure model index (SMI) before and after canal shaping were evaluated by using micro-computed tomography. The degrees and directions of transportation were also measured, and statistical analysis was carried out with one-way analysis of variance and Tukey post hoc tests.

Results

There were no significant differences between the 2 groups in canal curvature, volume, surface area, and SMI categories measured before preparation (P > .05). Changes in curvature, root canal volume, surface area, and SMI were not affected by the instrumentation technique used (P > .05). There were no significant differences in the degrees and directions of transportation between CM and RM groups (P > .05).

Conclusions

The application of reciprocating motion during instrumentation did not result in increased apical transportation when compared with continuous rotation motion, even in the apical part of curved canals. Reciprocating motion might be an attractive alternative method to prevent procedural errors during root canal shaping.     

Alveolar ridge dimensions in maxillary posterior sextants: a retrospective comparative study of dentate and edentulous sites using computerized tomography data

Aim: To compare the alveolar ridge dimensions between edentulous sites and contralateral dentate sites of maxillary posterior sextants in the same individuals. Materials and methods: Computerized tomography scans of 32 patients with one fully edentulous and one fully dentate maxillary posterior sextants were analyzed. Results: When compared with dentate sextants, edentulous sextants showed (i) a lower bone height (BH) at second premolar, first molar and second molar sites, which was associated with a more coronal position of the maxillary sinus floor at second premolar site; (ii) a more apical position of the ridge at second premolar and second molar sites; (iii) a lower bone width (BW)_{1 mm} at first and second premolar sites, and a lower BW_{3 mm} at all sites, (iv) a lower, although not significant, prevalence of premolar and molar sites with BH≥8 mm and BW_{1 mm}≥6 mm. Conclusions: The edentulous sextants in the posterior maxilla showed a reduced height and width of the ridge when compared with contralateral dentate sextants. The reduced vertical dimensions observed in edentulous sextants were variably associated with ridge resorption as well as sinus pneumatization. To cite this article:
Farina R, Pramstraller M, Franceschetti G, Pramstraller C, Trombelli L. Alveolar ridge dimensions in maxillary posterior sextants: a retrospective comparative study of dentate and edentulous sites using computerized tomography data.
Clin. Oral Impl. Res. 22 , 2011; 1138–1144.
doi: 10.1111/j.1600‐0501.2010.02087.x     

Introduction of a new periodontal probe: the pressure probe

Abstract. A new periodontal probe has been developed: the pressure probe. The probe consists of a cylinder and piston assembly connected to a variable air pressure system. The working end is a metal tube in which a plunger can move freely. By means of air pressure the plunger is constantly fully extruded. During probing the plunger will intrude from the position of maximum extrusion only as the probing force exceeds the predetemined force acting on the plunger. The difference by which the plunger is intruded can be read on a millimeter scale within the handle of the probe. The purpose of the present investigation was to determine whether probing force is constant during probing, to study the reliability of reading pocket depth measurements in vitro, and to investigate the relationship between pocket depth and applied force in man. In order to evaluate whether the probing force is constant during probing, measurements were performed on a force transducer. Results show that the device makes probing possible with a constant and adjustable pressure. The influence of the reading of the calibration on pocket depth assessment in vitro was studied in an in vitro model. Results show that pocket depths of 1 mm to 8 mm ± 0.25 mm were read correctly in about 90 % of instances. Generally about 45 % of the half millimeter values were recorded as the lower whole millimeter. To investigate the relationship between pocket depth and applied force, 173 pocket depth measurements were performed in eight patients. Patients selected for this study had, in some part of the upper anterior segment, loss of alveolar bone support up to two-thirds of the root length, visible on periapical radiographs. All patients received preliminary treatment consisting of plaque control and removal of subgingival deposits. The mean Sulcus Bleeding index score was 0.2. Pocket depth measurements were carried out with forces of 0.15, 0.25, 0.50 and 0.75 N. Both approximal and vestibular pocket depths were recorded. In this study 0.75 N was chosen as the maximal force since in a pilot study a force of 1.0 N appeared too painful for patients. Results show an increasing pocket depth with increasing probing force. The mean pocket depths increased from 2.08 mm at 0.15 N to 3.71 mm at 0.75 N. Testing showed it to be statistically significant. At 0.75 N, 72 out of the 173 pockets examined were equal to or deeper than 4 mm. The percentages were calculated of differences equal to or more than 2 mm between pocket depth measurements carried out with 0.75 N and lower forces. It was found that 63.3 % of pocket depths measured with 0.15 N were, when measured with 0.75 N, 2 mm or more deeper. This was 43.1 % when 0.25 N and 0.75 N were compared and 9.7 % when 0.50 N and 0.75 N were compared. The maximal differences varied from 5 mm to 7 mm.     

基于磁共振的青年男性股四头肌的测量和评估

目的: 通过观测髌骨上缘不同水平位置股四头肌横截面积(cross-sectional area,CSA)与体积(quadriceps muscle volume,QMV)的相关性,探讨评估股四头肌肌肉参数的最佳测量位置。方法: 对22例单侧前交叉韧带(anterior cruciate ligament,ACL)断裂男性患者行双侧大腿磁共振成像检查,患者平均年龄(29±6)岁,分别选取髌骨上缘18、15和12 cm处,利用半自动分割和医学影像处理软件确定QMV和各水平位置CSA。通过拟合回归方程建立模型估计QMV,采用Bland-Altman分析评价两者之间的一致性。结果: 受试者健侧QMV平均为(1 944.45±323.77) cm³。髌骨上缘18、15和12 cm处的股四头肌CSA分别为(80.80±12.16) cm²、(77.53±12.03) cm²和(72.68±10.51) cm²,拟合方程R²分别为0.819、0.755、0.684(P均<0.001),QMV估计值的标准误(standard error of the estimate,SEE)分别为7.4%、8.7%、9.8%(以体积的百分比表示)。三个水平位置的拟合方程均较好,但以髌骨上缘18 cm处的拟合度最高。Bland-Altman散点图结果显示,髌骨上缘18、15和12 cm处的QMV差值平均值分别为0.8 cm³、-1.1 cm³、0.9 cm³,95%一致性界限分别为(-268.8, 270.5)、(-315.2, 313.1)、(-355.7, 357.5),髌骨上缘18 cm处QMV的估计值与实测值一致性最好,患侧与健侧结果一致。结论: 以髌骨上缘作为基线探讨青年男性QMV与CSA的相关性具有可靠性和一致性,其中以髌骨上缘18 cm处的股四头肌CSA与QMV的相关性最好,但对于股四头肌的不同损伤部位,可选择不同观测位置。     

直肠腔内三维超声和MRI对中下段直肠癌壁外血管侵犯程度的评估效果

比较直肠腔内三维超声（3D-ERUS）和核磁共振成像（MRI）对中下段直肠癌术前壁外血管侵犯（EMVI）的诊断结果,探讨3D-ERUS在评估中下段直肠癌术前EMVI中的临床价值。