Detection of the apical lesion and the mandibular canal in conventional radiography and computed tomography

OBJECTIVE: The purpose of this study was to compare the information gathered from dental radiography and high resolution computed tomography (CT) scans with regard to the detection of the endodontic lesion and its relation to the important neighboring anatomic structures such as the mandibular canal. STUDY DESIGN: Fifty patients with a persistent apical lesion referred for endodontic surgery were selected. The teeth involved were 6 mandibular premolars and 44 mandibular molars. Eighty roots were evaluated. For each case 1 CT scan and 1 periapical radiograph were taken. The apical lesion and the mandibular canal were evaluated for possible identification in CT scan or radiograph. The presence of the lesion was correlated to the findings during the surgical procedure. The CT scans of the involved roots were further evaluated with regard to the bone thickness and differentiation between cancellous and cortical bone. The position of the lesion/root within the mandible was studied in all dimensions. RESULTS: All 78 lesions diagnosed during surgery were also visible with the CT scan. In contrast, only 61 of the lesions were noted by conventional radiographs. The mandibular canal could be identified in 31 cases in dental radiographs, whereas in the oblique cuts of the corresponding CT scans the mandibular canal was detected in all patients. The amount of cortical and cancellous bone and the bone thickness as well as the three-dimensional extent of the lesion could only be adequately interpreted in CT scans. CONCLUSIONS: The use of CT provides additional, beneficial information not available from dental radiographs for treatment planning in apical surgery of mandibular premolars and molars. When the mandibular canal cannot be detected in dental radiographs or is in close proximity to the lesion or root apex, CT should be considered before endodontic surgery. The presence, extent, and location of the lesion and its relation to the mandibular canal can be predictably evaluated in a CT scan of the area.     

Radiologic examination for location of the mandibular canal: a comparison between panoramic radiography and conventional tomography

Panoramic radiography was compared with conventional tomography as techniques for visualizing the mandibular canal. Tomography gave a significantly clearer image of the canal at and 1 cm posterior to the mental foramen, while no differences were found between the methods 2 cm posterior to the mental foramen. Thus, tomography could be of great value in locating the mandibular canal before implant surgery in edentulous mandibular posterior segments.     

Comparison between panoramic radiography and cone-beam computed tomography findings for assessment of the relationship between impacted mandibular third molars and the mandibular canal

Objectives

The aim of this study was to assess the relationship between the mandibular canal and impacted mandibular third molars using cone-beam computed tomography (CBCT) and to compare the CBCT findings with panoramic radiographic signs.

Methods

This study involved a retrospective radiographic review of 781 impacted third molars in 500 patients who showed a close relationship between the mandibular canal and the third molars on panoramic radiographs. Panoramic radiographic images were evaluated for interruption of the white line, darkening of the roots, diversion of the mandibular canal/roots, and narrowing of the mandibular canal/roots. The authors evaluated CBCT images to determine the course of each canal and its proximity to the roots. The statistical correlations between the panoramic radiography and CBCT findings were examined using the Chi-square test and Fisher’s exact test.

Results

Cone-beam computed tomography examination showed that darkening of the roots and deviation of the canal associated with the absence of corticalization between the mandibular third molar and the mandibular canal on panoramic radiographs were statistically significant, both as isolated findings and in association. No significant associations were observed for the other panoramic radiographic findings, either individually or in association.

Conclusions

The results of this study suggest that darkening of the roots, deviation of the mandibular canal, and interruption of the white line observed on panoramic radiographs, both as isolated findings and in association, were effective for determining the risk relationship between the roots and the mandibular canal, requiring three-dimensional evaluation of such cases.     

Radiographic assessment of the mandibular retromolar canal using cone-beam computed tomography

Abstract

Objective. The ‘retromolar’ nerve is a collateral branch of the inferior alveolar nerve. Cone-beam computed tomography (CBCT) provides higher resolution images. This CBCT study reports the frequency of the retromolar nerve. Materials and methods. From 2007–2010 the CBCT study of 233 hemi-mandibles have been examined. The CBCT study was obtained from an investigation of the posterior mandibular region in 187 patients suffering from different pathologies and it was aimed at detecting in patients the presence of a retromolar canal and foramen. Results. Thirty-four retromolar canals with a foramen were detected on 233 CBCT (14.6%) in 30 out of 187 patients (16%). In the 46 patients who underwent CBCT bilaterally, the retromolar canal was found in nine subjects (19.6%) and was present bilaterally in four subjects, for an incidence of 8.7%. Conclusions. The results suggest that the radiological frequency of the retromolar nerve is notable, with a possible relevance in the surgical approach of the mandibular retromolar area. The presence of a retromolar canal, well detected with CBCT, may warn clinicians about the possibility of inadequate pre-surgical anaesthesia, local intra-operative bleeding and post-operative alterations of the sensation in the third molar area.     

Simple bone cyst: Evaluation of contents with conventional radiography and computed tomography

To evaluate whether gas is present in the cavity of simple bone cysts, the clinical and histologic findings of 53 patients with simple bone cysts were examined and compared with an experimental model. The model consisted of a dry mandible with the medullary bone removed and the resulting cavity injected with water. Although an air-liquid level was observed on all radiographs for the experimental model, none was observed in the clinical cases of simple bone cysts. When the experimental cavity was completely filled with water, the density in the cavity was similar to that of the surrounding water on computed tomography, but when it was filled with air, the density was lower than that of the surrounding water. In contrast, in simple bone cysts said to contain air at surgery, the cavity contents were not consistent with the density for gas on computed tomography. These results indicate that the operative finding of air in the cavity of simple bone cysts may have been in error at least in some cases.     

Branching of mandibular canal on cone beam computed tomography images

BackgroundMandibular neurovascular canal contents may be vulnerable to damage during mandibular surgical procedures. Greater knowledge of the location and configuration of the mandibular canal can help in the safe performance of these procedures in the dental clinic. Cross-sectional CBCT imaging is a good modality for studying the course, location, configuration and accessory branches of the mandibular canal. The aim of this study was to observe the branching of the mandibular canal at different segments of the mandible and mandibular tooth groups.MethodsCBCT images of 116 mandibular halves were included in this study. The presence of secondary branching of the mandibular canal in the ramus, retromolar area, molar and premolar teeth as well as the length, diameter and angle of these branches were observed.Resultssixty nine mandibular halves (59.5%), had a main canal with no branching, There were 36 IAC (31%) with one, 8 (6.9%) with two, 2 (1.7%) with three and 1(0.9%) with 5 accessory branches. Of these secondary branches, 16 (25.4%) were in the ramus, 16(25.4%) in the retromolar, and 31(49.2%) in the molar regions.ConclusionAdvanced cross-sectional imaging modalities especially CBCT is a suitable tool for observing anatomic characteristics of mandibular canal to preserve this vital structure in surgical procedures.     

下颌管分支的锥形束CT影像学分析

目的 运用锥形束CT（CBCT）分析下颌管分支发生的概率及其类型。方法 选取拍摄CBCT影像的216例（女104 例,男112例）患者为研究对象,对CBCT的下颌管分支影像进行观测并进行分类。结果 216例（432侧）患者中,39例（18.06%）50侧（11.57%）观测到下颌管分支,其中女18例（17.31%）,男21例（18.75%）。下颌管分支分为4类,第Ⅰ类17侧（3.94%）,第Ⅱ类11侧（2.55%）,第Ⅲ类20侧（4.63%）,第Ⅳ类2侧（0.46%）。结论 CBCT对下颌管分支的检出率较高,口腔颌面外科医生在进行下颌手术时应注意下颌管分支这一解剖变异。     

Assessment of variations of the mandibular canal through cone beam computed tomography

The neurovascular bundle may be vulnerable during surgical procedures involving the mandible, especially when anatomical variations are present. Increased demand of implant surgeries, wider availability of three-dimensional exams, and lack of clear definitions in the literature indicate that features of anatomical variations should be revisited. The objective of the study was to evaluate features of anatomical variations related to mandibular canal (MC), such as bifid canals, anterior loop of mental nerve, and corticalization of MC. Additionally, bone trabeculation at the submandibular gland fossa region (SGF) was assessed and related to visibility of MC. Cone beam computed tomography exams from 100 patients (200 hemimandibles) were analyzed and the following parameters were registered: diameter and corticalization of MC; trabeculation in SGF region; presence of bifid MC, position of bifurcations, diameter, and direction of bifid canals; and measurement of anterior loops by two methods. Corticalization of the MC was observed in 59% of hemimandibles. In 23%, MC could be identified despite absence of corticalization. Diameter of MC was between 2.1 and 4 mm for nearly three quarters of the sample. In 80% of the sample trabeculation at the SGF was either decreased or not visible, and such cases showed correlation with absence of MC corticalization. Bifid MC affected 19% of the patients, mostly associated with additional mental foramina. Clinically significant anterior loop (>2 mm of anterior extension) was observed in 22–28%, depending on the method. Our findings, together with previously reported limitations of conventional exams, draw attention to the unpredictability related to anatomical variations in neurovascularization, showing the contribution of individual assessment through different views of three-dimensional imaging prior to surgical procedures in the mandible.     

Localisation of the mandibular canal using conventional spiral tomography: a human cadaver study

For certain surgical procedures (e.g. placement of implants), an accurate localisation of the mandibular canal is of utmost importance to avoid injuries to the neurovascular bundle. The aim of the present study was to evaluate, on human fresh cadavers (n = 6), the accuracy of conventional spiral tomography for the localisation of the mandibular canal. By means of the Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland), tomographic slices were taken at 3 different locations in the left posterior mandible (distal to the mental foramen). The mandibles were then sectioned at these 3 sites with a microtome. With a digital sliding caliper, the following 3 measurements were performed both on the tomograms and the bone sections at the three sites: 1) distance from the crest to mandibular canal, 2) overall bone height and 3) bone width. Overestimations of the distance to the mandibular canal (8/18) ranged from 1.05 to 0.10 mm and underestimations from 0.30 to 1.36 mm. The same number of over- and underestimations occurred for the bone height (1.14 to 0.14 mm and 0.15 to 1.40 mm, respectively). The bone width scored more overestimations (10/18), ranging from 1.40 to 0.12 mm, while underestimations ranged from 0.25 to 1.35 mm. From the present results, it is concluded that spiral tomography using the Cranex TOME multifunctional X-ray unit provides accurate information and sufficient detail for preoperative planning of implant placement in the posterior mandible.     

锥形束计算机体层摄影术观察下牙槽神经管形态及其临床意义

目的 应用锥形束计算机体层摄影术（CBCT）观测并分析下牙槽神经管在下颌骨内的走行特点,探讨其分布规律,为临床手术提供解剖学依据.方法 采用单纯随机抽样法选取具备下颌后部CBCT 扫描数据的患者60 例,应用CBCT 自带的KaVo eXam Vision 软件测量颏孔区、前磨牙区、磨牙区下牙槽神经管与牙槽嵴顶、下颌骨颊舌侧骨板及下缘的平均距离,对各组测量项目进行成组t 检验比较,并观察其走行特点.结果 下牙槽神经管距下颌下缘小于距牙槽嵴顶的距离,在第二磨牙区距离下颌骨下缘最近;颏孔区至第一磨牙区间,下牙槽神经管距颊侧骨板距离小于距舌侧骨板距离,自第二磨牙后,下牙槽神经管距颊侧骨板距离则大于距舌侧骨板距离;性别及左、右侧下牙槽神经管距离差异无统计学意义（t＝2.437,P ＞ 0.05）.结论 CBCT 扫描有利于更好了解下牙槽神经管的走行及结构特异性,对牙槽外科及种植外科手术方案的制定具有一定临床指导意义.     

锥形束CT与数字化根尖片对根充效果的评价

目的比较锥形束CT(CBCT)与根尖片对根管充填后效果的评价,进一步探讨CBCT在根管治疗中的优势及应用价值。方法选取经临床诊断需要进行根管治疗的100颗患牙(221例根管),根管充填后同步拍摄根尖片与CBCT,术后分别由2位经验丰富的临床医生从根管充填的有效长度与严密程度两方面进行读片,运用卡方检验比较2种方法是否在评价结果上存在差异性。结果总计充填根管214例,充填遗漏7例,在根管充填长度、严密程度及满意程度评价方面,分别约有34.58%、30.48%和37.58%的根管在数字化根尖片与CBCT的评价结果上未能达成一致意见,经过统计学检验,数字化根尖片与CBCT在上述三方面的评价均有高度显著性差异(P<0.01)。结论 CBCT较根尖片在根管治疗术的长度及严密程度评价方面更为灵敏及准确,在复杂或疑难的根管治疗术中拥有很高的临床应用价值。     

Variations of the bony canal in the mandibular ramus using cone-beam computed tomography

The location and configuration of the mandibular canal are important in surgical procedures involving the mandible. Previously, we reported that bifid mandibular canals could be classified into four types: retromolar, dental, forward, and bucco-lingual canals, using cone-beam computed tomography (CBCT). Herein we report three Japanese patients with a bony canal in the mandibular ramus, which was independent of the mandibular canal, using CBCT images. A CBCT unit with a flat panel detector and exposure volume of 102 mm in diameter and 102 mm in height was used. Two-dimensional (2D) and three-dimensional (3D) images in the mandibular ramus region were reconstructed using 3D visualization and measurement software packages. Three bony canals in two patients were considered to correspond to a temporal crest canal, which was raised from the mandibular notch, and reached the antero-inferior region of the coronoid process. One bony canal in one patient, ran bucco-lingually in the mandibular ramus. It is important for variations in the mandibular and bony canals to be carefully observed, by use of CBCT images, in surgical procedures involving the mandible.     

下颌切牙根管解剖特点的锥形束CT影像学研究

目的采用锥形束CT研究下颌切牙根管解剖特点,及其与性别、年龄、牙位的关系。方法使用锥形束CT观察316例共1148颗下颌切牙,获得其断层图像后进行三维重建,通过计算机图像观察其根管数目及根管类型。记录被检查者的性别、年龄和牙位。计算下颌切牙双根管检出率,统计根管类型,分析根管解剖特点与性别、年龄、牙位的关系。结果下颌切牙双根管检出率为27．5％,其双根管类型以Vertucci分类的Ⅲ型最多,占14．1％。双根管在各年龄段间的分布差异有统计学意义（P〈0．05）,20～29岁和30～39岁两个年龄段的双根管检出率较高,分别为36．8％和36．5％。下颌切牙双根管的检出率女性高于男性。侧切牙双根管的检出率高于中切牙,结论下颌切牙双根管检出率较高,锥形束CT在诊断双根管方面具有重要作用。     

下颌前磨牙牙根形态和根管系统的锥形束CT研究

目的采用锥形束CT(Cone-beam computed tomography,CBCT)研究下颌前磨牙牙根及根管系统解剖形态特征。方法回顾148例患者288颗下颌第一前磨牙和218颗下颌第二前磨牙的CBCT影像,分析牙根和根管系统形态,采用Vertucci等提出的分类法对根管构型进行分类。结果 288颗下颌第一前磨牙单根牙285颗,双根牙2颗。三根牙1颗;根管Ⅰ型占77.78%,Ⅱ型0.34%,Ⅲ型2.08%,Ⅳ型0.69%,Ⅴ型14.58%,Ⅶ型1.04%,Ⅹ型0.69%,C型2.78%。218颗下颌第二前磨牙全部为单根;根管Ⅰ型占98.17%,Ⅴ型占1.83%。结论下颌前磨牙大多数是单根单根管。下颌第一前磨牙根管系统具有较大的变异性。下颌第一前磨牙多根管类型主要是Ⅴ型,C型根管的检出率也较高。而下颌第二前磨牙多根管的发生率远低于下颌第一前磨牙。多根管的分歧发生在根中或根尖1/3处。CBCT可用于下颌前磨牙复杂根管形态的评价。