The validation of 3D spiral CT-based measurements of simulated maxillofacial neoplasms

OBJECTIVE: The purpose of this study was to determine the precision and accuracy of 3-dimensional spiral computed tomography-based linear measurements of neoplasms associated with the mandible. STUDY DESIGN: Four cadaver heads, each with 2 simulated tumors made of clay, containing contrast medium, and positioned medial to the mandible, were examined by means of a subsecond spiral computed tomography unit. The computed tomography data were transferred to a computer workstation and analyzed through use of 3-dimensional reconstructed images. Linear measurements of the length, width, and depth of the simulated tumors were made by 2 observers, twice each. The soft tissues were then removed and the same measurements made by means of calipers. RESULTS: There were no statistically significant differences between the 3-dimensional computed tomography and physical measurements (P >.05). The mean difference was found to be less than 0.4 mm. CONCLUSIONS: Spiral computed tomography imaging allows for precise and accurate 3-dimensional computed tomography-based measurements for neoplastic lesions in the mandible.     

多层面螺旋CT的口腔种植体定位研究

目的 探讨多层面螺旋CT的后处理重建技术在口腔种植体植入术前精确定位及骨量测量的意义。方法测量比较带有3个放射标记物的模板在模型及多层面螺旋CT影像中的距离和相互角度,并在CT影像中虚拟植入种植体,观察种植体植入情况。结果 多层面螺旋CT中影像的放射标记物间的距离与模型上测量数据的差异无统计学意义,并能直观、准确提供种植体植入的骨量信息。结论 使用多层面螺旋CT能在术前准确评估牙槽骨骨量及确定种植体植入位置、方向、大小、长度。     

Quality of preimplant low-dose tomography

OBJECTIVES: The aim of this study was to test the influence of radiation dose on image quality in mandibular preimplant computed tomographic examinations and to compare the quality of computed and conventional spiral tomographic images. STUDY DESIGN: Cross-sectional images were obtained on 17 patients with conventional spiral tomography (Scanora technique) and reformatted computed tomography at 40 and 80 mAs. Observers graded the acceptability of images for implant planning and traced the contour of the mandibular body and canal. RESULTS: Conventional spiral tomographic images scored significantly higher than computed tomographic images whereas mean score differences between computed tomographic techniques were not statistically significant. Anatomic structures, in particular the mandibular canal, were more frequently untraceable in high-dose than in low-dose computed tomography but always traceable in conventional tomograms. CONCLUSION: Conventional spiral tomograms were subjectively preferred over computed tomographic images. For mandibular implant planning, computed tomography examinations can be performed with lower-than-standard mAs. Quantum noise seems to contribute to the visibility of anatomic structures in reformatted computed tomographic images.     

Spiral tomography for measuring bone width at different levels from the crest to the inferior border of the mandible in vitro

Introduction Tomography images provide sufficient detail for estimating the vertical and horizontal dimensions of alveolar bone and reducing surgical injuries. This study evaluated the role of spiral tomography in measuring mandibular alveolar bone width. Methods Cross-sectional tomography slices were taken using a Cranex Tome unit at three or four different locations on each side of three chosen mandibles, such that all the locations were distal to the mental foramen. In addition, artificial soft tissues were reconstructed using Play-Doh modeling clay. On the tomography image, a line was drawn from the crest to the inferior border of the mandible (MC), and the bone height to the mandibular canal and bone width were measured at one-third, two-thirds, and one-half MC, and the mandibular canal levels. Then, the mandibles were sectioned at the same sites, and the bone sections were measured. For statistical analysis, the sign test analysis was used. Results There was a statistically significant difference between the tomographic and real anatomical bone width at one-half and one-third MC, and the canal level (P < 0.05), while the difference between tomography and bone section measurements were not significant at two-thirds MC, or, the bone height to the mandibular canal (P > 0.05). Conclusions The bone width on tomographic images was overestimated by between 2.3 and 0.1 mm. Therefore, caution should be exercised when evaluating bone width measured from tomography images. In most locations, the measured height to the canal was underestimated by between 0.1 and 2.7 mm, which confirmed the safety of spiral tomography for estimating the distance related to the mandibular canal.     

颅面部螺旋CT三维线距测量的准确性评价

目的:研究颅面部螺旋CT三维线距测量与实测距离的一致性。方法:选择12个干燥头颅,采用GE公司16层螺旋CT常规扫描后,将头颅数据转至工作站,进行颅颌面三维重建。选择正畸常用的16个颅面骨性解剖标志点,分别使用DisplayTools测量工具和游标卡尺进行20个项目测量。采用SAS9.0统计软件包进行配对t检验,比较螺旋CT三维线距测量与实测距离的一致性。结果:螺旋CT三维线距测量与游标卡尺实测结果相比,P值范围为0.0995～0.9812,所有测量项目均无显著性差异。结论:螺旋CT体绘制图像颅面解剖标志点间线性距离与实测距离具有一致性,螺旋CT三维测量有望替代实际测量,用于头影测量分析。     

The use of 3 different imaging methods for the localization of the mandibular canal in dental implant planning

PURPOSE: The purpose of this study was to investigate the efficiency of panoramic radiography, conventional (cross-sectional) tomography, and computerized tomography for location of the mandibular canal before implant placement in the posterior region of the mandible. MATERIALS AND METHODS: Edentulous mandibles from 6 dry adult human skulls were used in this study. Four measurements (D1, D2, D3, D4) were made of 12 areas, one on each side of each mandible. Panoramic radiographs, conventional tomograms, and computerized tomograms were obtained. On each image, measurements were made for localization of the mandibular canal by one researcher. All measurements were repeated 3 times within a period of 3 weeks. Upon completion of imaging, the mandibles were surgically sectioned to provide direct measurements. The measurements obtained from the images were compared with direct measurements. Pearson correlation coefficients were calculated to detect statistical correlations between repeated measurements. The Dunnett t test was performed for statistical comparison of measurements from images and direct measurements. RESULTS: Pearson correlation coefficients showed strong linear correlation for all measurements (P < .01). No statistically significant difference was observed between direct measurement and D1, D2, or D4 (P < .05), but a statistically significant difference for D3 (buccolingual width 5 mm under mandibular crest; Dunnett t test; P > .05) between measurements was obtained from the images and direct measurements. CONCLUSION: The measurements obtained from computerized tomographic images were more consistent with direct measurements than the measurements obtained from panoramic radiographic images or conventional tomographic images.     

Reliability of spiral tomography with the Scanora® technique for dental implant planning

The Scanora X‐ray unit permits linear and rotational narrow beam radiography as well as spiral tomography, making it well suited for implant planning radiography. The purpose of this study was to evaluate the reliability of measurements made in spiral lower jaw tomograms of patients examined with the Scanora® technique. Six observers measured the distance between the alveolar crest and the mandibular canal in spiral tomographic images taken on 40 consecutive patients before implant surgery. In one randomly chosen image from each patient, the observers marked the measuring points at the two locations. The measurements were repeated 2 months later. Three of the observers, all radiologists. excluded in total 11 sets of images considered to improve if retaken. Analysis of variance showed an average standard deviation between observers of 1.67 mm. This was mainly due to the intraobserver variation, 1.07 mm. The variation between plots was significantly larger at the alveolar crest. Confidence intervals showed that reliability improves with multiple readings, either made independently by one observer or separately by several. The inter‐ and intraobserver variation decreased to 1.42 mm and 0.86 mm, respectively. without the images of inferior quality. Compared with a similar study based on hypocycloidal images, the variability was less due to the intraobserver variation and was affected positively by an optimized image quality.     

Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: experimental validation in vitro.

PURPOSE: This study evaluated the measurement accuracy of three-dimensional (3D) volumetric images from spiral computed tomography (CT) in vitro. MATERIALS AND METHODS: The study sample consisted of nine cadaver heads that were submitted to an impact force by a special device to promote blunt traumatic craniofacial fractures. The heads were subsequently scanned by a spiral CT scanner (Toshiba Xpress S/X). The archived CT data were transferred to networked computer workstations (Sun Microsystems with Cemax VIP version 1.4 software) to generate 3D volumetric images. The visualization software was used to make interactive linear measurements on the 3D images. Measurements were made on the images twice by two observers, based on conventional craniofacial anatomic landmarks. The soft tissues were subsequently removed, and the same measurements were repeated on the cadaver heads with an electromagnetic digitizer (3 Space, Polhemus, Colchester, VT). RESULTS: The results showed no statistically significant differences between the 3D-CT and the physical measurements, with P>.05 for all measurements. The mean difference between the image and real measurements was less than 2 mm in all instances. CONCLUSIONS: It is concluded that measurement of the skull and facial bone landmarks by 3D reconstruction is quantitatively accurate for surgical planning and treatment evaluation of craniofacial fractures.     

Preoperative assessment of the relationship between the mandibular third molar and the mandibular canal by axial computed tomography with coronal and sagittal reconstruction

OBJECTIVE: We sought to evaluate the relationship between the mandibular third molar and the mandibular canal by using axial computed tomography with coronal and sagittal reconstruction for third molar surgery. STUDY DESIGN: Forty-seven impacted third molars in 41 patients were found in close association with the mandibular canal during a panoramic radiographic assessment. The relationship between the mandibular third molar and the mandibular canal was evaluated by using computed tomography and compared in terms of operative exposure of the inferior alveolar nerve and postoperative labial dysesthesia. RESULTS: Twenty-four (51%) mandibular canals were buccal relative to the third molar, 12 were lingual, 9 were inferior, and 2 were between roots. At the time of the surgical procedure, the inferior alveolar nerve was visible in 7 patients. Postoperative lower lip dysesthesia occurred in 1 patient whose mandibular canal was in the lingual position. CONCLUSIONS: Axial computed tomography with coronal and sagittal reconstruction provides useful information to surgeons regarding the relationship between the mandibular third molar and the mandibular canal.     

Optimum conditions for detecting the inferior alveolar artery using phase-contrast magnetic resonance angiography

Objectives  

The inferior alveolar artery (IAA), accompanied by the inferior alveolar nerve, runs through the mandibular canal. The mandibular canal can be observed by conventional radiography and computed tomography, although it is sometimes difficult to identify on these images. This study examined visualization of the IAA with phase-contrast magnetic resonance angiography (PC-MRA).     

Third molar position: reliability of panoramic radiography.

PURPOSE: The purpose of the present study was to determine whether panoramic radiographs could predict physical contact between the mandibular third molar and the mandibular canal on limited cone-beam computed tomography, known as dental 3D-CT (3-dimensional computed tomography [3D-CT]). PATIENTS AND METHODS: The association of images between the panoramic radiograph and the dental 3D-CT was investigated in a cross-sectional study. Seventy-three lower third molars in 65 patients were examined. Findings of absence or presence of the white line of the mandibular canal wall on panoramic radiographs and contact or separation between the tooth and the mandibular canal on dental 3D-CT were compared. RESULTS: Absence of a superior white line on panoramic radiography was associated with an increased risk of contact between the third molar and the mandibular canal on dental 3D-CT, even when the effects of tooth position, age, and gender were taken into account. The multivariate adjusted odds ratio was 10.79. Women were more likely to have contact between the 2 structures on dental 3D-CT when their panoramic radiograph showed absence of the white line. CONCLUSIONS: Panoramic radiography is useful for predicting to a limited extent physical contact between the mandibular third molar and the mandibular canal on dental 3D-CT.     

锥形束CT对上牙槽后动脉骨孔的测量分析研究

目的 通过锥形束CT（CBCT）影像评估上牙槽后动脉骨孔位置、大小及与剩余牙槽骨的关系。方法 选择2011年4月-2012年9月前来南昌大学附属口腔医院种植科要求行上颌窦底提升手术和(或)上颌磨牙区种植手术,并且拍摄CBCT的患者116名,测量记录其上牙槽后动脉骨孔下缘至剩余牙槽嵴顶间距、上牙槽后动脉骨孔直径、剩余牙槽嵴高度,对各测量值进行统计分析。结果 入选116名患者中上牙槽后动脉骨孔的发现率为75.14%（133/177）;骨孔的平均直径为（0.96±0.29） mm;剩余牙槽嵴高度平均值为（7.14±3.64） mm;上牙槽后动脉骨孔下缘距剩余牙槽嵴顶间距均值为（17.92±5.68） mm。经采用独立样本t检验发现性别对骨孔直径影响差异有统计学意义（F= 0.187,P<0.05）;右侧和左侧骨孔间差异无统计学意义（F=0.295,P>0.05）。上牙槽后动脉骨孔下缘距牙槽嵴顶间距与剩余牙槽嵴高度显著正相关。结论 CBCT在发现上牙槽后动脉骨孔具有较明显的优势。     

Anatomical differences in lower third molars visualized by 2D and 3D X-ray imaging: clinical outcomes after extraction

The purpose of this study was to evaluate the relationship between third molars and the inferior alveolar canal using panoramic radiographs and cone beam computed tomography (CBCT) scans and to assess clinical outcomes after third molar removal retrospectively. The degree of superimposition, buccolingual position (buccal, central, and lingual) and physical relationship (separation, contact, and involved) were measured using CBCT scanning. Post-extraction complications were recorded. Based on radiographic evaluation, 45.9% of third molar roots were inside the inferior alveolar canal, 21.3% were in contact with the inferior alveolar canal, and 32.8% were separated from the canal. The frequency at which the mandibular canal was separated from the root apex was significantly higher when the canal was in the buccal position (80.0%) than in the central (20.0%) and lingual positions (0.0%). Although on panoramic radiographs all third molars were directly superimposed on the inferior alveolar canal, CBCT showed direct contact or canal involvement in 67.2% and separation of the canal from the root apex in 32.8%. Complications occurred in nine patients: eight had third molar root apices inside or in contact with the inferior alveolar canal. The prevalence of post-extraction complications correlated with the absence of cortication around the inferior alveolar canal.     

Accuracy of linear measurements before and after digitizing periapical and panoramic radiography images

The aim of this study was to evaluate the accuracy of linear measurements made on conventional and digitized periapical and panoramic radiographic images of dry human hemi-mandibles. Images from the posterior region of 22 dry human hemi-mandibles were obtained by conventional panoramic and periapical radiography technique. Using a digital caliper, 3 vertical measurements were marked directly on the dry hemi-mandibles (reference measurements) as well as on the tracing from the conventional radiographic images of the specimens made onto acetate paper sheet: Distance 1: between the upper limit of the alveolar ridge and the lower limit at the mandible base; Distance 2: between the upper limit of the alveolar ridge and the upper limit of the mandibular canal; Distance 3: between the lower limit of the mandibular canal and the lower limit of the mandible base. Next, the radiographs were digitized and the three measurements were made on the digital images using UTHSCSA Image Tool software. Data were analyzed statistically by one-way ANOVA (α=0.05). There was no statistically significant differences (p>0.05) between periapical and panoramic radiographs or between the measurements recorded using the digital caliper and UTHSCSA software compared with dry mandible specimens for Distances 1 (p=0.783), 2 (p=0.986) and 3 (p=0.129). In conclusion, the radiographic techniques evaluated in this study are reliable for vertical bone measurements on selected areas and the UTHSCA Image Tool software is an appropriate measurement method.     

The usefulness of cone-beam computed tomography gray values for alveolar bone linear measurements

Objectives:To test a proof-of-concept that the accuracy and reliability of alveolar bone height measurements from orthodontic grade (large field-of-view [FOV], large voxel-size) cone-beam computed tomography (CBCT) images may be improved by using pixel gray values.Materials and Methods:Twenty fresh cadaver pig heads underwent CBCT scans (17 × 23 cm FOV, 0.4-mm voxel size). Buccal alveolar bone heights of maxillary first molars were measured using the conventional vision-based (VB) and the proposed gray value–assisted (GVA) methods. The GVA methods entailed localization of landmarks through observation of gray value pattern changes across tissue boundaries followed by mathematical calculation of distances between landmark pixels. Interrater reliability and accuracy of CBCT measurements made by all methods were statistically analyzed by comparing with physical measurements (gold standards).Results:The interrater reliability of CBCT measurements made by GVA methods was comparable to physical measurements but higher than those made by the VB method. The GVA (bend-down pattern) method yielded average measurements similar to physical measurements, while those obtained by the VB and the GVA (straight pattern) methods were significantly larger (repeated measures analysis of variance, P < .001). The GVA (bend-down pattern) method also produced significantly more measurements within one voxel size of physical measurements than did the VB and GVA (straight pattern) methods (Chi-square tests, P < .017).Conclusions:These data confirm a concept that local gray value change patterns may be used to improve the accuracy and reliability of alveolar bone height measurement from large FOV and large voxel-size CBCT images.     

螺旋CT结合Dentascan软件在种植牙术前颌骨评估中的应用

目的：评价螺旋CT结合Dentascan软件和定位模板在种植牙术前颌骨评估中的应用价值。方法：将用压模机制作的透明树脂定位模板戴入植牙患者口内,以0．5mm层厚螺旋CT扫描颌骨。扫描的数据传至CT工作站用Dentascan软件处理后显示侧断层图、曲面断层图及三维重建图。结果：所有25例病例重建图均能清晰的显示颌骨的形态、质地和重要的解剖结构,如上领窦、颏孔、下牙槽神经管,并且能精确的测量缺牙区可用骨的高度、厚度和宽度。结论：螺旋CT结合Dentascan软件和定位模板在种植牙治疗计划的设计中起关键作用,尤其像前牙美容区域,并有利于提高种植牙的成功率。     

Study of mandibular alveolar distraction osteogenesis using a three-dimensional computed tomography measurement method: report of four patients, a preliminary study

OBJECTIVE: This study was conducted to show dimensional and volumetric changes after vertical alveolar distraction osteogenesis using a three-dimensional computed tomography measurement method. MATERIALS: Four patients with mandibular alveolar ridge atrophy were evaluated. Three-dimensional computed tomography reconstructions were obtained 2 weeks before and 3 months after the operation. The results of the three-dimensional computed tomography measurements were used for preoperative planning and for quantitative assessment of the mandibular alveolar distraction. The results of the preoperative and postoperative three-dimensional computed tomography measurements were compared statistically using paired t-test. RESULTS: The increase in distracted mandibular segment volume and surface area, height, and width of each slice after distraction were statistically significant (P < 0.001). CONCLUSION: In atrophic jaw cases, the dimensions of the present alveolar bone were clearly measured so that the amount of augmentation needed could be estimated. Three-dimensional computed tomography provided better understanding of the effects of distraction osteogenesis on the anterior mandible. Newly formed bone can be viewed as close to its real dimensions after distraction osteogenesis.     

Canal transportation after root canal instrumentation: a comparative study with computed tomography

This in vitro study used computed tomography (CT) to compare the occurrence of canal transportation in the apical third of mesiobuccal canals in maxillary molars instrumented with 3 techniques. Sixty teeth were assigned to 3 groups (n = 20), and the root canals were instrumented as follows: Group 1, hand instrumentation with K-files; Group 2, K-files coupled to an oscillatory system powered by an electric engine; Group 3, ProTaper NiTi rotary system powered by an electric engine. To compare the canal transportation produced by the different techniques, preinstrumentation and postinstrumentation 3-dimensional CT images were obtained from root cross-sections of the region located 3 mm short of the apical foramen of each root canal. The CT scans were exported to Adobe Photoshop software, and the initial and final images were superimposed to detect the root canal wall differences between them. Canal transportation was measured by the distance between the prepared canal center and the anatomic canal center. The manual technique produced lesser canal transportation (0.10 mm) than the oscillatory and rotary techniques (0.37 and 0.22 mm, respectively); this difference was statistically significant (P=.021). All studied techniques produced canal transportation.     

Proximity of Impacted Mandibular Third Molars to the Inferior Alveolar Canal and Its Radiographic Predictors: A Panoramic Radiographic Study

Purpose

To assess the radiographic proximity of impacted mandibular third molars to the inferior alveolar canal on panoramic radiographs. The radiographic distance between the impacted mandibular third molars and inferior alveolar canal and the reliable radiographic risk predictor signs that indicate close proximity between these two structures were evaluated.

Methods

The study comprised of 64 subjects with 68 symptomatic impacted mandibular third molars for whom panoramic radiographs were made. The radiographs were interpreted for type of impaction, radiographic distance between impacted mandibular third molars to inferior alveolar canal and presence of one or more of the seven radiographic risk predictor signs. Further, these teeth were surgically removed and the proximity was assessed based on the exposure of inferior alveolar canal/nerve which was considered as Gold standard.

Results

The overall mean distance from the impacted mandibular third molars to inferior alveolar canal was −0.50 mm. Most of the samples (61.8 %) extended beyond the superior border of the inferior alveolar canal with a mean distance of −1.40 mm. Mesioangular impactions were found to be in the close proximity (−1.14 mm) to inferior alveolar canal than any other type. Interruption of the white line was the only statistically significant radiographic risk predictor sign p = 0.006 (< 0.05) that indicated close proximity of impacted mandibular third molars to inferior alveolar canal.

Conclusion

It can be concluded that panoramic radiographs are reliable in assessing the proximity of impacted mandibular third molars to inferior alveolar canal. Mesioangular impactions are more closely placed to inferior alveolar canal and interruption of the white line is the most reliable risk predictor sign on the panoramic radiographs.     

COMPARATIVE STUDY OF SINGLE AND MULTISLICE COMPUTED TOMOGRAPHY FOR ASSESSMENT OF THE MANDIBULAR CANAL

Objective:

The purpose of this study was to evaluate the accuracy of relative measurements from the roof of the mandibular canal to the alveolar crest in multislice (multidetector) computed tomography (MDCT) and single-slice computed tomography (SSCT).

Material and Methods:

The sample consisted of 26 printed CT films (7 SSCT and 19 MDCT) from the files of the LABI-3D (3D Imaging Laboratory) of the School of Dentistry of the University of São Paulo (FOUSP), which had been acquired using different protocols. Two observers analyzed in a randomized and independent order a series of 22 oblique CT reconstructions of each patient. Each observer analyzed the CT scans twice. The length of the mandibular canal and the distance between the mandibular canal roof and the crest of the alveolar ridge were obtained. Dahlberg test was used for statistical analysis.

Results:

The mean error found for the mandibular canal length measurements obtained from SSCT was 0.53 mm in the interobserver analysis, and 0.38 mm for both observers. On MDCT images, the mean error was 0.0 mm in the interobserver analysis, and 0.0 and 0.23 mm in the intraobserver analysis. Regarding the distance between the mandibular canal roof and the alveolar bone crest, the SSCT images showed a mean error of 1.16 mm in the interobserver analysis and 0.66 and 0.59 mm in the intraobserver analysis. In the MDCT images, the mean error was 0.72 mm in the interobserver analysis and 0.50 and 0.54 mm in the intraobserver analysis.

Conclusion:

Multislice CT was demonstrated a more accurate method and demonstrated high reproducibility in the analysis of important anatomical landmarks for planning of mandibular dental implants, namely the mandibular canal pathway and alveolar crest height.