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。     

Organ radiation dose assessment for conventional spiral tomography: a human cadaver study

The head of a human cadaver was positioned in a Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland) to measure the organ radiation doses after tomographic examinations of the upper and lower edentulous jaw bone. Five consecutive examinations were carried out in the upper and lower anterior jaw regions to cover the entire frontal area, 2 in the upper and lower left premolar regions, and 3 and 4 in the upper and lower left molar regions, respectively. Each examination consisted of 4 slices with a 2 mm slice thickness. Thermoluminescent dosimeter chips were placed in the thyroid gland and bilaterally in the parotid and submandibular glands. Dosimetric measurements were repeated for the different tomographic examinations mentioned above. For spiral tomography in the maxilla, organ doses for both parotid glands were most elevated, while those for the thyroid glands were the lowest. Average doses per examination reached levels of 0.27 mGy for the right (OS) parotid gland with frontal tomography, and 3.89 mGy and 1.67 mGy for the parotid gland at tube-side (TS) for premolar and molar tomography. For the thyroid gland, a minimal dose of < or = 0.004 mGy was noticed for all examinations. For spiral tomography of the frontal area in the mandible, the OS parotid gland received the highest dose (0.77 mGy), while for an analysis of the premolar and molar areas, doses were more elevated for the TS parotid gland (1.22 mGy and 1.72 mGy, respectively). For the TS submandibular gland, organ doses were also raised, with values of 0.39 mGy for frontal, 1.31 mGy for premolar and 1.61 mGy for molar tomography. This study thus indicates that for conventional spiral tomographic examinations in the maxilla and the mandible, radiation doses for the TS submandibular and parotid glands were significantly more elevated than those to the thyroid gland. These values remain however below the organ doses previously reported for spiral CT involving both a full upper or lower jaw.     

Association between impacted third molars and position of the mandibular canal: a morphological analysis using cone-beam computed tomography

Our aim was to assess the association between the angle of impaction of the third molar and the position of the mandibular canal on cone-beam computed tomography (CT). We designed a retrospective study of 100 cone-beam CT images of 173 mandibular third molars that were obtained between January 2012 and December 2015, and recorded the angle of impaction of the third molar, the position of the mandibular canal in relation to the impacted tooth, and the potential contact between the roots of the tooth and the mandibular canal. Most third molars tilted mesially (n = 33), while the mandibular canal was positioned below the roots of the third molar in most cases (n = 73). Contact between the two was most likely when the mandibular canal was between (RR = 1.49; 95% CI 1.27 to 1.75, p < 0.001), or to the lingual side (RR = 1.49; 95% CI 1.27 to 1.75, p < 0.001) of the roots of the tooth. These outcomes indicate a greater likelihood of contact between the canal and the roots when the canal is between, and to the lingual side, of the roots. We found no association between the angle of impaction and the position of the canal. These findings illustrate the importance of surgical planning using complementary imaging tests such as cone-beam CT.     

Detection of the mandibular canal via shaded surface display and multiplanar reconstruction of CT data

The purpose of this study was to evaluate the sensitivity of conventional two-dimensional (2D) multisection images (multiplanar rendering, MPR) and registered three-dimensional (3D) shaded surface images (shaded surface display, SSD) of standard axial computed tomography (CT) data for detecting the mandibular canal (MC) in the lower jaw of 136 patients. The patients, who had different indications for mandibular CT, were examined using standard axial CT scanning. Two post-processing programs were used for 3D visualization of the data sets. The cross-sectional rendered images and the shaded surface 3D images were graded for detection of the MC, the presence of artefacts, overall quality and clinical relevance. A 3D display of the MC was achieved using the MPR technique in 100% with high image quality. The surface rendered display depicted the MC in 80%. Artefacts markedly degraded the 3D displays obtained using the surface rendering technique; thus, SSD is an inappropriate technique for imaging the entire MC without manual segmentation. MPR-CT improves the sensitivity of CT imaging in the detection of the MC with very little time needed for post-processing compared with the SSD method. This post-processing modality should, therefore, be considered for serial studies of patients undergoing dental CT. The sensitivity of the MPR method is even superior to the standard axial CT slices.     

正常青年人下颌管全长三维走向及下颌骨形态的锥形束CT测量

目的采用锥形束CT（CBCT）分析正常青年人下颌管在下颌骨内的三维位置以及下颌骨的形态特征,为临床下颌骨手术提供解剖学依据。方法 对29例个别正常进行CBCT扫描,用InVivo 5软件对下颌骨进行三维重建,定位标记点,测量下颌骨形态以及下颌管在其内的三维走行。采用SPSS 17.0软件对测量值进行统计分析。结果 下颌管舌侧骨皮质厚度明显较颊侧骨皮质薄。下颌管到颊侧骨皮质的距离从近中到远中逐渐增加,到舌侧骨皮质、牙槽嵴顶的距离从近中到远中逐渐减小,到下颌下缘的距离在第一磨牙处最小,第二前磨牙处最大。下颌体截面高度、宽度、皮质骨厚度左右侧无统计学差异,从中线至远中,下颌体截面高度、舌侧下1/3皮质骨厚度逐渐减小,上截面宽度、唇/颊侧上1/3皮质骨厚度逐渐增大。部分测量项目性别间有统计学差异。结论下颌管入下颌孔后渐渐远离舌侧而向颊侧靠近,然后又逐渐远离偏向舌侧,但其总体走行还是靠近舌侧。男性下颌骨较女性更坚厚。CBCT能精确地显示下颌神经管的走行及其与周边结构的关系。     

A cone-beam computed tomography study of root canal morphology of maxillary and mandibular premolars in a Turkish population

Aim. The aim of this study was to evaluate the root canal number and configuration of maxillary and mandibular premolar teeth by gender, intervals for decades, tooth position and unilateral or bilateral occurrence in a Turkish population using Cone Beam Computed Tomography(CBCT) scanning. Methodology. CBCT images of 5496 maxillary and mandibular premolars from 849 patients were evaluated. The following was evaluated in all the images: numbers of roots and root canals, the morphology of the root canal configuration according to the Vertucci classification, male–female differences in the tooth position and male–female differences in unilateral or bilateral occurrence. The reliability data were analyzed with a chi-square test. Results. The most prevalent root canal frequency was the two canals (86.2%) and type IV (76.9%) configuration for maxillary first premolar, one canal (59.7%) and type I (54.5%) canal configuration for second premolar. The incidence of one canal was higher in females and the occurrence of two or three canals was more common in males. The incidence of one canal was higher on the left side of maxillary premolars and the incidence of two canals was higher on the right side. Most mandibular first (93.5%) and second (98.5%) premolars had one canal. In general, females had one root canal of the mandibular premolar, whereas males had two or three canals. The type I configuration was most common and the incidence was higher on the right side. There were some differences found in the frequency distribution of the number of root canals and configuration of maxillary and mandibular premolar teeth according to intervals for decades. Conclusion. CBCT scanning provides comprehensive information about the root canal morphology of maxillary and mandibular premolar teeth. These data may help clinicians in root canal treatment of premolar teeth.     

大量根充糊剂进入下颌管10年观察1例报告

根管治疗是通过机械和化学方法取出根管内的大部分感染物,并通过充填根管、封闭冠部,防止发生根尖周病变或促进已经发生的根尖周病变的愈合[1]。下颌后牙周围解剖结构接近下颌管,在根管治疗过程中,机械性、化学性或热刺激都有损伤下牙槽神经的潜在风险。如根管充填糊剂超出根尖孔,与神经组织接触,有病例报道会产生细胞毒性及机械挤压造成神经敏感性改变[2]。本文报道1例左下第二磨牙行根管治疗,大量根充糊剂进入下颌管10年观察,患者未出现下牙槽神经损伤症状的病例。     

锥形束CT在下颌第二磨牙C形根管治疗前中后的应用

下颌第二磨牙C形根管存在根管变异和不规则峡区,容易造成根管清理不彻底和充填不足。锥形束CT(CBCT)可清晰地显示C形根管在矢状面、冠状面和横断面的解剖形态。CBCT空间分辨率高,图像清晰;可选择合适的视野,小视野图像更清晰;可以光盘形式最大限度的保存图像信息,方便临床医生在计算机上多层面、多方位的仔细观察;金属伪影少,辐射剂量低,扫描时间短;所显示下颌第二磨牙C形根管图像的矢状面、冠状面和横断面无前后重叠、无变形和无放大等情况,可为了解下颌第二磨牙C形根管形态提供清晰的三维影像。下颌第二磨牙C形根管预备的难度主要有相对独立的根管间有大量的副根管、交通支和根管弯曲,传统器械难以进入峡区;将显微镜和CBCT共同使用,可提高下颌第二磨牙C形根管的治疗效果。在根管预备前行CBCT检查,可提醒术者避免过度切削并防止侧穿。本文就CBCT在下颌第二磨牙C形根管治疗前中后的应用等研究进展作一综述。     

Changes in the pre-surgical treatment planning using conventional spiral tomography

OBJECTIVE: To investigate variation in the pre-surgical treatment planning after using conventional spiral tomography in addition to conventional radiographic exams. MATERIAL AND METHODS: Twenty-nine partial or fully edentulous patients referred to implant therapy were selected and submitted to periapical, panoramic and conventional cross-sectional tomography exams. Pre-surgical treatment planning of 120 potential implant sites in 69 edentulous areas was performed by two independent experienced dental implant surgeons. After clinical examination, pre-surgical planning was made using only periapical and panoramic exams. Examiners were requested to reformulated initial planning after assessing tomographic images. Four treatment parameters were evaluated: length and width of implants, need of bone grafting and need of other surgical procedures. RESULTS: Implant length and width remained unchanged in 60.2% and 87.2% of cases, respectively. No difference in length (P=0.576) and width (P=1) scores was observed in treatment planning with and without tomography. Variation in implant dimension was not affected by location of edentulous areas. Bone grafting and other surgical procedures significantly changed after tomograms (P<0.001), independent of the location of edentulous areas. In 15.8% and 5.3% of cases bone grafting and other procedures were planned only after tomograms, respectively. Significant differences were observed in all maxillary and mandibular regions. CONCLUSION: Conventional spiral tomography plays an important role in pre-surgical treatment planning, increasing clinician's certainty of the need of additional surgical procedures (bone grafting, sinus lifting, and others) in pre-surgical treatment stage.     

Visualisation of the mandibular canal by different radiographic techniques

6 mandibles were radiographically examined bilaterally to visualise the mandibular canal. 5 imaging techniques were used: periapical radiography, panoramic radiography, hypocycloidal tomography, spiral tomography and computed tomography (CT). Panoramic radiographs were obtained with 2 different X-ray machines. The CT-examinations comprised direct images and standard reconstructions based on axial slices. The specimens were subsequently sectioned for contact radiography. The visibility of the mandibular canal was estimated by 3 observers at special reference points on all radiographs and classified as clearly visible, questionable visibility or not visible. The contact radiographs served as the "gold standard". The inter-observer and the intra-observer agreement were assessed by calculating the overall agreement and the x value. Direct coronal computed tomography, as well as spiral and hypocycloidal tomography, gave better visualisation of the mandibular canal than periapical and panoramic radiography.     

Absorbed doses from spiral CT and conventional spiral tomography: a phantom vs. cadaver study

For several radiological examinations, a clinician can select between conventional and spiral computed tomography. Using both techniques, this study aimed at evaluating the difference in absorbed doses when examining a single lateral jaw segment in a human cadaver head and Rando phantom. The present study involved the placement of thermoluminescent dosimeter (TLD) chips (GR-200) in the thyroid gland, and bilaterally, in the parotid and submandibular glands and the lenses of the eyes in both a human cadaver and a Rando phantom at corresponding locations. Consecutive conventional spiral tomographic examinations were carried out in both the left upper and lower premolar area, using a Cranex TOME multifunctional unit. Each examination consisted of 4 slices with a 2 mm slice thickness and exposure parameters of 57 kV, 56 seconds and 1.6-2.0 mA. Regarding spiral computed tomography (CT), a Somatom Plus S scanner (Siemens, Erlangen, Germany), with a slice thickness of 1 mm with settings at 120 kV and 165 mA, was used on both phantoms and separately in the upper and lower jaw. With conventional tomography, the findings of the present study showed that the parotid and submandibular glands on the side near the X-ray tube received the highest dose, both for the cadaver head (doses ranging from 0.5 to 1.3 mGy) and the phantom (doses ranging from 0.6 to 2.6 mGy). For CT of the upper jaw, the highest doses were delivered to the parotid glands with an average absorbed dose of 9.2 and 10.6 mGy for the cadaver head and phantom, respectively. The submandibular glands received the highest doses during CT examination of the lower jaw with an average of 7.8 and 12.9 mGy for the cadaver head and phantom, respectively. It appears from the present investigation that if small edentulous regions are examined, radiation doses during conventional tomography remain much lower than during CT imaging. However, when multiple tomographic cuts are required, a spiral CT examination can replace a series of conventional examinations, especially in cases such as the rehabilitation of an edentulous upper jaw or a more complex surgery.     

锥束CT评价下颌第二恒磨牙牙根和根管解剖形态研究

目的:用锥束CT扫描评估下颌第二恒磨牙牙根和根管解剖形态。方法:收集305例锥束CT影像,分别记录病人的性别、牙位、牙根和根管的数目和形态,采用Vertucci分类法对根管构型进行分类描述。结果:在受检样本中,47.21%的下颌第二恒磨牙为融合根,C形根和C型根管的检出率均为41.64%。在两个根的下颌第二恒磨牙中,66.03%近中根管是Ⅳ型,92.31%的远中根管是I型。左、右侧下颌第二恒磨牙C形牙根和C型根管的发生率没有统计学差异(P>0.05),男性和女性的C形牙根和C型根管的发生率也没有统计学差异(P>0.05)。结论:中国西部人群中,下颌第二恒磨牙通常为双根或融合根,C形牙根和C型根管的发生率均较高。     

Radiologic measurements of the mandible: a comparison between CT-reformatted and conventional tomographic images

This study was carried out to compare the accuracy of determination of the mandibular contour and the position of the mandibular canal in cadaver mandibles by the multiplanar reconstruction method (MPR-CT), which has recently come to be used widely for preoperative examinations, with those by tomographic techniques and to evaluate the usefulness of MPR-CT. Using three imaging systems, i.e. Quantum CT scanner, Scanora, and OP-100, a total of 6 sites were scanned in the molar regions of 3 cadaver mandibles. The images obtained were measured twice each by 4 radiologists. The anatomic structures measured were the height and thickness of the mandible, distance from the alveolar crest to the mandibular canal, and distance from the buccal cortical bone to the mandibular canal. After scanning, the scanned areas of the mandibles were sliced at a thickness of 2 mm, and soft X-ray images of these slices were obtained. The values of the above 4 anatomic structures obtained by measurements in the soft X-ray radiograms using digital-display calipers were regarded as true values. When compared with the true values, the errors in the distance from the alveolar crest to the mandibular canal were within 1 mm (+/- 1 mm) in 93.7% of the measurements by Direct-CT, 89.6% of the measurements by MPR-CT, 87.5% of the measurements by Scanora, and 47.9% of the measurements by OP-100, and the accuracy of the 4 methods ranked in the order of Direct-CT, MPR-CT, Scanora, and OP-100. A similar tendency was observed in the measurements of other anatomic structures, and statistically significant differences were observed among the methods. Thus, MPR-CT allows more accurate measurements than by the other 2 tomographic techniques,and to be useful as a preoperative examination for implant surgery.     

CBCT study of root and canal morphology of permanent mandibular incisors in a Chinese population

Objective. To evaluate root canal morphology of permanent mandibular incisor teeth in a Chinese population using cone-beam computed tomography (CBCT). Materials and methods. CBCT images of Chinese patients were collected and 1553 permanent mandibular incisors in the images were included. The following observations on the included teeth were to determine the number of roots, root morphology and canal configuration. The root canal configurations were classified. The effect of gender on the incidence of the second canal was investigated. Results. Of permanent mandibular incisors, 86.8% had a single root with single canal. Mandibular lateral incisors (17.5%) had a higher incidence of a second canal compared with mandibular central incisors (8.9%) (p = 0.000). A slightly higher percentage of incidence of a second canal was found in males (14.6%) than in females (11.9%) (p = 0.129). Conclusions. Permanent mandibular incisors with two canals had a relatively low incidence in this Chinese population. The incidence of a second canal did not differ between males and females. CBCT is a valuable aid during root canal treatment.     

下颌恒切牙根管形态的影像学研究

目的：探讨下颌恒切牙根管解剖形态的影像学特征，为临床采用X线片评估该牙根管系统提供依据。方法：中国人下颌恒切牙300个，采用传统X线胶片和数字化X线片从唇舌向和近中远中向投照牙片，两名牙体牙髓专科医师同时观察牙片，判读根管数目、根管类型、根管钙化程度，并根据根管直径推测根管横切面形状。结果：下颌恒切牙有1个根管（67．89％）和2个根管（32．11％），唇舌向X线片双根管检出率（3．34％）明显低于近中远中向（32．11％）（P〈0．05）。根管类型按Vertucci分类，Ⅰ型67．9％，Ⅱ型11．4％，Ⅲ型18．1％，Ⅳ型0．7％，Ⅴ型1．0％，Ⅵ型1．0％。根管钙化率：1级为89．67％，2级为7．33％，3级为3．0％。根管横切面形状扁长形以根中1／3最高，达85．6％。结论：下颌恒切牙根管解剖形态复杂，临床上唇舌向X线片可能掩盖部分根管解剖信息。