A comparison of jaw dimensional and quality assessments of bone characteristics with cone-beam CT, spiral tomography, and multi-slice spiral CT

PURPOSE: For proper preoperative planning of oral implants, the need has increased for tomographic imaging for precise determination of anatomic dimensions. However, concern for radiation exposure, which is substantial with computerized tomography (CT), has also grown. In the present study, the validity of jawbone width assessment and delineation by means of cone-beam CT (CBCT) and spiral tomography on dry mandibles was compared. Secondly, the subjective image quality of CBCT images with those obtained by multi-slice spiral CT (MSCT) of a fixed ex vivo cadaver with its soft tissues was compared. MATERIALS AND METHODS: The study included 25 dry human mandibles for the dimensional study and 1 formalized maxilla for image quality assessment. Measurements of the mandibles by means of a digital sliding caliper acted as the gold standard. Radiographic examination of the premolar and canine regions was performed with both CBCT and spiral tomography. Observational measurements were carried out by postgraduates in oral imaging. Subjective image quality was assessed on the fixed maxilla, including soft tissues, by comparing CBCT and MSCT. Inter- and intraobserver variability were determined. RESULTS: Direct mandibular measurements were on average 0.23 mm (SD 0.49) and 0.34 mm (SD 0.90) larger than the CBCT and spiral tomography measurements, respectively. Subjective image quality of the CBCT was significantly better than for the MSCT with regard to visualization and delineation of the lamina dura and periodontal ligament space. Subjective image quality of the MSCT was significantly better for the MSCT than the CBCT for the gingiva and cortical bone. CONCLUSIONS: These results indicate that on dry mandibles, jawbone width measurements by means of CBCT and spiral tomography are reliable, even if on average they slightly underestimate the bone width. For the subjective image quality, the CBCT offered better visualization of details of the small bony structures. Spiral tomography offered better visualization of the cortical bone and the gingiva.     

Measurement accuracy of reconstructed 2-D images obtained by multi-slice helical computed tomography

The present dental reconstructed computed tomography (CT) images consist of continuously piled-up axial CT images that are perpendicular to the axial CT plane. In the mandibular posterior region, the angles of designed implants frequently differ from the angles perpendicular to the axial CT plane and the measurement of mandibular height is inaccurate. This study was performed to clarify the measurement accuracy of double-oblique reconstructed images in multi-slice helical CT, using dried mandibles. The mandibular height was measured from the alveolar crest immediately below the aluminum tube to the superior border of the mandibular canal using the double-oblique reconstructed images and the micro-CT average images of three semi-lateral dried mandibles. The mean of the differences between the double-oblique reconstructed images with a table pitch of 1.5 in a helical scan and the micro-CT average images was 0.31 mm. It is concluded that the accuracy of the double-oblique reconstructed image measurements with helical scan is high. So this double-oblique program can be applied to the imaging diagnosis in dental implant treatment.     

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.     

Accuracy of implant placement based on pre-surgical planning of three-dimensional cone-beam images: a pilot study

AIM: To evaluate the precision of transfer of a computer-based three-dimensional (3D) planning, using re-formatted cone-beam images, for oral implant placement in partially edentulous jaws. MATERIAL AND METHODS: Four formalin-fixed cadaver jaws were imaged in a 3D Accuitomo FPD cone-beam computed tomography (CT). Data were used to produce an accurate implant planning with a transfer to surgery by means of stereolithographic drill guides. Pre-operative cone-beam CT images were subsequently matched with post-operative ones to calculate the deviation between planned and installed implants. RESULTS: Placed implants (length: 10-15 mm) showed an average angular deviation of 2 degrees (SD: 0.8, range: 0.7-4.0 degrees ) as compared with the planning, while the mean linear deviation was 1.1 mm (SD: 0.7 mm, range 0.3-2.3 mm) at the hex and 2.0 mm (SD: 0.7 mm, range 0.7-2.4 mm) at the tip. CONCLUSIONS: Cone-beam images could be used for implant planning, taking into account a maximal 4 degrees angular and 2.4 mm linear deviation at the apical tip.     

Accuracy of magnetic resonance imaging compared with computed tomography for implant planning

Aim: The objective of this study was to evaluate the reliability of magnetic resonance imaging (MRI) compared with computed tomography (CT) for dental implant planning in respect to bone measurements. Methods: Five dry mandibles were submitted to MRI and CT examinations. Each mandible had three specific sites identified with markers, in a total of 15 sites to be studied. The images provided by the MRI and CT examinations were delivered to four specialists in Oral and Maxillofacial Radiology to measure the bone height at the specific sites. Subsequently, the bone height of the dry mandibles was directly measured in the determined sites. The measurements obtained by the specialists in MRI and CT images were compared with the measurements obtained directly from the dry mandibles using the ANOVA test with a 0.05 significance level. Results: The differences between the measurements obtained directly from the dry mandibles and the measurements from the MRI exams varied from 0.13 to 1.67 mm, with 10 sites being overestimated in MRI exams and five sites being underestimated. The differences between the measurements from the dry mandibles and CT exams varied from 0.02 to 1.25 mm, with nine sites being overestimated in CT exams and six sites being underestimated. The differences between the measurements from the MRI and CT exams varied from 0.03 to 1.00 mm, with nine sites giving higher values in MRI exams and six sites giving higher values in CT exams. There were no statistically significant differences between the three grous of measurements (P=0.98). Conclusion: The MRI, when compared with CT, shown to be reliable in respect to bone measurements for dental implant planning.     

Comparative assessment of subjective image quality of cross-sectional cone-beam computed tomography scans

Since the introduction of cone-beam computed tomography (CBCT), several novel systems with different technical specifications and settings have become commercially available. Therefore, it is essential to evaluate CBCT systems for differences in the subjective quality of images obtained for various dental procedures. We evaluated the subjective image quality of cross-sectional scans obtained from various CBCT systems. Images of three cadaver mandibles were obtained from four different CBCT units: 1) Veraviewepocs 3D 40 × 40 mm field of view (FOV) (voxel size: 0.125 × 0.125 × 0.125 mm), 2) Iluma, low-resolution (voxel size: 0.3 × 0.3 × 0.3 mm), 3) Kodak, 50 × 3.7 cm FOV (voxel size: 0.076 × 0.076 × 0.076 mm), and 4) Vatech 12 × 8.5cm FOV (voxel size: 0.160 × 0.160 × 0.160 mm). We assessed subjective image quality and the visibility of 10 specific features, namely, caries, amalgam restoration, final implant drill, root canal filling, metal crown, mandibular canal, mental foramen, tooth (periodontal ligament space and lamina dura), trabecular pattern, and soft tissue. Images were viewed and scored by five calibrated observers, and image quality was ranked from best to worst. The Veraviewepocs 3D had the highest quality images for most of the assessed features, whereas the Iluma low-resolution scans were rated as the lowest quality images.     

Evaluation of voxel values in mandibular cancellous bone: relationship between cone-beam computed tomography and multislice helical computed tomography

Objective: Measurements of bone density in designed sites are important in presurgical imaging for dental implant treatment. However, the pixel or voxel values obtained from cone-beam computed tomography (CT) images are not absolute values. Hence, the relationship between voxel values obtained from cone-beam CT with a limited-volume exposure field and a flat panel detector and bone mineral densities (BMDs) obtained from multislice CT was evaluated in the mandible.
Material and methods: A total of 16 (four males and 12 females) patients who had undergone imaging for mandibular dental implant treatment using cone-beam CT with Alphard VEGA and multislice CT were enrolled in this investigation.
Cross-sectional images of cone-beam and multislice CT were reconstructed, and values of regions of interest (ROIs) in images were calculated.
Results: A high-level correlation between voxel values of cone-beam CT and BMDs of multislice CT was observed ( r =0.965).
Conclusion: It was suggested that voxel values of mandibular cancellous bone in cone-beam CT could be used to estimate bone density.     

Cross-sectional imaging of the jaws for dental implant treatment: accuracy of linear tomography using a panoramic machine in comparison with reformatted computed tomography

PURPOSE: Although various panoramic X-ray machines with linear tomographic functions are now frequently applied to diagnosis related to dental implant treatment, the angles of the tomographic objective planes are automatically determined and cannot be adjusted for individual patients. To resolve this problem, a direct laser positioning (DLP) system was developed. In this investigation, the measurement accuracy of images obtained by the DLP system in comparison with those from reformatted computed tomography (CT) was assessed. MATERIALS AND METHODS: A rectangular parallel piped phantom was scanned with the system and the height and width were measured on linear tomograms. Ten sites in 3 dried mandibles and 21 mandibular molar sites in 15 patients were examined both with the DLP system and the reformatted CT to compare the measured values on both images. RESULTS: The phantom experiment showed that the difference between the actual and measured heights and widths of the phantom were within 1 mm. DISCUSSION: The difference between the values obtained by the DLP system and CT was slightly larger in the patients than those in the dried mandibles. CONCLUSION: The DLP measurement accuracy was deemed sufficient for clinical use.     

X线曲面体层摄影、螺旋CT用于牙槽骨测量的比较

目的：比较曲面体层摄影（OP），螺旋CT（SCT）与实体牙槽骨测量的差异，为牙种植手术提供客观依据。方法：将3副颅骨标本各在12个部位用铝管，直径6mm钢球标志，拍摄SCT、OP，测量颌骨高度和／或宽度，再将颌骨依冠状面锯开后测量实际高度，宽度。SCT三维重建，比较差异，结果：OP、SCT均有影象失真，放大率OP＞SCT，分别为22．39％，5．28％，OP，SCT，实测值间有极显著差异，P＜0．0001，OP钢球与牙槽骨放大率经Wilcoxon检验无显著差异，P＞0．5，相关系数r=0.8335，显示良好的正相关。结论：对于牙种植手术前的牙槽骨测量不宜直接以OP或以OP机固有放大率校正的牙槽骨数值作为手术参考。用参照物放大率校正OP值有实用价值，能较好计算该部位牙槽骨实际高度，SCT的放大率较小且恒定。     

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.     

Assessment of three-dimensional X-ray images: reconstruction from conventional tomograms, compact computerized tomography images, and multislice helical computerized tomography images

Three-dimensional X-ray images (3D images) were used for imaging diagnosis in the oral and maxillofacial region. These images could be fundamentally reconstructed from various tomograms, though clinical 3D images were mainly reconstructed from computerized tomography (CT) images. In this investigation, 3D images were reconstructed from conventional tomograms with a panoramic unit, compact CT images, and multislice helical CT images, and the usefulness of each system was subjectively assessed for dental implant treatment. Three hemilateral dried human mandibles were used and were examined by linear tomography with a panoramic unit, compact CT, and multislice helical CT, and 3D images were reconstructed by using the rendering software for each system. The 3D images were visually evaluated on a 5-point scale covering the alveolar ridge, buccal and lingual bone surface, mental foramen, and tooth sockets. As a result, 3D images reconstructed from conventional tomograms with the panoramic unit were assessed as fair to unsure, compact CT 3D images were assessed as unsure to good, and multislice helical CT 3D images were assessed as good to excellent. It was concluded that compact CT 3D images and multislice helical CT 3D images were useful in dental implant treatment.     

Imaging of root canal fillings: a comparison of subjective image quality between limited cone-beam CT, storage phosphor and film radiography

AIM: To compare the subjective quality of limited cone-beam computed tomography (LCBCT), storage phosphor plate (SPP) and F-speed film images for the evaluation of length and homogeneity of root fillings. METHODOLOGY: Root canals of 17 extracted permanent mandibular incisor teeth were filled. With the teeth placed in their jaws, images were obtained with Accu-I-Tomo LCBCT, Digora Optime image plate system and F-speed film using exposure parameters yielding 'clinically' acceptable density and contrast. Three radiologists and three endodontists independently rated the quality of all images in respect to homogeneity and the length of root fillings using a 3-graded scale. Evaluations were undertaken in two sessions. In the first, the coronal LCBCT images were not included. In the second, both coronal and sagittal LCBCT images were rated along with F-speed film and SPP images. RESULTS: were compared using the Friedman test (P < 0.05). Pair-wise comparisons of systems were completed using the Wilxocon signed-ranks test (P < 0.05). Kappa was used to measure interobserver agreement. Results Digora images were rated superior, consecutively followed by F-speed films and LCBCT images, for the evaluation of both homogeneity and length of root fillings in both the evaluation sessions (P < 0.05). Kappa ranged from slight to moderate for the length evaluation of root fillings and from poor to fair for the evaluation of homogeneity of root fillings. CONCLUSION: Image quality of storage phosphor images was subjectively as good as conventional film images and superior to LCBCT images for the evaluation of both homogeneity and length of root fillings in single-rooted teeth.     

成人颜面不对称患者颌面部骨性结构的三维立体分析

目的:通过锥体束CT(cone-beam computerized tomography,CBCT)资料分析颜面不对称患者颌面部骨性结构三维空间位置的改变。方法:对25例成人颜面不对称患者使用CBCT采集颅面部Dicom数据,使用Mimics 10.01对骨组织进行三维重建,并建立三维坐标系。选择描述上颌复合体及下颌骨形态的36个标志点,测量其三维坐标进行统计分析。结果:上颌复合体仅眶下点、梨状孔最外侧点、颧牙槽嵴点、上尖牙颈缘中点、上第一恒磨牙颈缘中点的位置左右侧差异有显著性,其它各点基本对称;下颌骨大部分标志点左右侧在三维方向上均差异显著,仅髁突顶点、下颌孔、下颌角点在某些方向显示出对称性。结论:颜面不对称患者颌面部畸形程度有从上到下逐步加重的趋势,主要表现为下颌骨形态异常,其立体空间结构发生了代偿性的旋转。     

颌面专用CT下颌骨检查技术

目的：研究颌面专用CT（QR-DVT 9000 NEWTOM）下颌骨检查技术的建立方法及技术要点,观察颌面专用CT下颌骨检查技术,在下颌骨X线检查中的优势.方法：对下颌骨疾病患者进行颌面专用CT扫描和重建成像,对其重建轴位影像进行曲面、矢状位、冠状位以及3D影像的后处理,并与常规X线片对比分析.结果：颌面专用CT下颌骨检查技术优于下颌骨常规X线检查,分别以水平位、曲面、矢状位、冠状位以及3D等多方位影像显示下颌骨的信息.结论：颌面专用CT下颌骨检查技术,在下颌骨的X线检查中有着明显的优势,并能够有效地指导临床手术.     

A survey of radiographic measurement estimation in assessment of dental implant length

The aim of this study is to survey radiographic measurement estimation in the assessment of dental implant length according to dentists' confidence. A 19-point questionnaire with closed-ended questions was used by two graduate students to interview 69 dentists during a dental implant meeting. Included were 12 questions related to over- and underestimation in three radiographic modalities: panoramic (P), conventional tomography (T), and computerized tomography (CT). The database was analyzed by Epi-Info 6.04 software and the values from two radiographic modalities, P and T, were compared using a chi2 test. The results showed that 38.24% of the dentists' confidence was in the overestimation of measurements in P, 30.56% in T, and 0% in CT. On the other hand, considering the underestimated measurements, the percentages were 47.06% in P, 33.33% in T, and 1.92% in CT. The frequency of under- and overestimation were statistically significant (chi2 = 6.32; P = .0425) between P and T. CT was the radiographic modality with higher measurement precision according to dentists' confidence. In conclusion, the interviewed dentists felt that CT was the best radiographic modality when considering the measurement estimation precision in preoperative dental implant assessment.     

Linear measurement accuracy of CBCT panoramic reconstructions: experimental study with dry human mandibles

Introduction

Studies on software accuracy of reformatted panoramic computed tomography (CT) images are scarce.

Objectives

The aim of this study was to evaluate the software accuracy of reformatted panoramic views from cone-beam computed tomography (CBCT).

Methods

Ten dry mandibles were scanned using CBCT with different voxel sizes. Following the reconstruction of panoramic views with three different software, horizontal and vertical linear measurements were performed using the electronic rules of each software. Measurements of the corresponding dry mandibles were taken with a digital caliper and defined as the gold standard.

Results

There were no statistically significant differences in linear distances among the dry mandibles and reformatted panoramic CT views. The relative error ranged from 1.3 to 8.0%, depending on the software and voxel size.

Conclusions

The linear measurements on reformatted panoramic views are reliable.

     

Three-dimensional display with quantitative analysis in alveolar bone resorption using cone-beam computerized tomography for dental use: a preliminary study

The current study used advanced three-dimensional (3-D) images with quantitative information to show the bottom of an intrabony defect. The 3-D data were corrected by means of a compact computerized tomography unit for dental use using a cone-beam method (3DX, Morita). 3-D images at the bottom of the intrabony defect in which the distance between the surface of the tooth and bone reached 0.5 mm were combined to provide a reconstructed image of the entire defect. Advanced 3-D images with quantitative information to show the bottom of an intrabony defect can display visually and in three dimensions the depth of an intrabony defect all around a tooth. Moreover, the distance between the cementoenamel junction and the bottom of an intrabony defect can be measured automatically using this technique.     

Bone density assessments of dental implant sites: 2. Quantitative cone-beam computerized tomography

PURPOSE: Bone density was evaluated in designated implant sites using a novel volumetric computerized tomographic device. Those measurements were then compared with traditional quantitative computerized axial tomography and subjective bone density evaluation. MATERIALS AND METHODS: Sixty-three potential sites for implant placement in jaws from 9 human cadavers were used. Indicator rods 2 mm in diameter were placed in all sites. Radiographic images representing 1-mm buccolingual slices immediately mesial and distal to the rods were selected. Bone density in Hounsfield units was assessed using quantitative cone-beam computerized tomography (QCBCT) and quantitative computerized tomography (QCT) in a standardized implant area superimposed on the images. Bone density was also subjectively evaluated by 2 independent examiners using the Lekholm and Zarb classification. RESULTS: The QCBCT bone density values were generally found to be higher than the corresponding QCT measurements. The correlations between the QCT and QCBCT values, however, were very high in spite of this systematic difference between the 2 methods. The Lekholm and Zarb ratings for the 2 examiners showed correlation coefficients ranging between 0.46 and 0.60 for the relationships with the QCBCT values. For each of the scores used for the subjective classification, however, a wide range of corresponding QCBCT values was observed. DISCUSSION: High dosage has been the major impediment to the utilization of CT in implant dentistry. The development of a reliable volumetric CT alternative with reduced radiation should provide an effective method for the assessment of both bone quantity and bone density. CONCLUSIONS: Access to objective radiographic bone density values should constitute a valuable supplement to subjective bone density evaluations prior to implant placement. QCBCT could be considered an alternative diagnostic tool for preoperative bone density evaluation, especially since the reported radiation dose is minimal.     

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.     

Navigated flapless transmucosal implant placement in the mandible: a pilot study in 20 patients

PURPOSE: The aim of this study was to assess whether navigated flapless transmucosal implant bed preparation allows placement of dental implants in edentulous mandibles. MATERIALS AND METHODS: Each patient was scheduled to receive 4 screw-shaped Ankylos (Dentsply Friadent) implants in the interforaminal region. The VISIT navigation system was used for guided drilling. The mucosa was penetrated without flap elevation. The study protocol did not allow direct visualization of the bone surface during surgery. Data analysis included computed measurements on pre- and postoperative computerized tomographic (CT) images. RESULTS: Twenty patients with fully edentulous mandibles (14 male, 6 female) were included in the study. Computer-based planning for 80 implants was performed intraoperatively. Two implants (2.5%) were not primarily stable because of buccal bone fenestration, which occurred because of uncontrollable shifting of the dental implant drill. These implants were immediately removed. Postoperative CT image evaluation revealed a mean deviation of 0.7 mm in all directions. CONCLUSIONS: Navigated flapless transmucosal interforaminal implant placement was found to be a precise, predictable, safe procedure in patients with smooth wide regular mandibular ridges. The technique was less accurate and more complicated in areas where irregular bone existed.