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.     

Effectiveness of dental computed tomography in diagnostic imaging of periradicular lesion of each root of a multirooted tooth: a case report

Radiography by use of the three-dimensional (3D) Accuitomo XYZ Slice View Tomograph (3DX), a device for compact computed tomography in dentistry, was performed as a new diagnostic imaging technique for a patient who needed endodontic therapy. The 3DX was used for examining and diagnosing the presence and expansion of periradicular lesions in each root of a multirooted tooth. High-resolution 3D images were observed and compared with those obtained by routine conventional radiography. It was difficult to diagnose the cause of clinical symptoms by general examinations including the usual intraoral radiography and panoramic radiography. The images obtained by the 3DX, however, clearly showed the apparent presence and expansion of a periradicular lesion in only one root of the multirooted tooth. The 3DX, a newly developed dental computed tomography, provides abundant new image information not attainable by either intraoral radiography or panoramic radiography, and its application for clinical use is very effective for examining and diagnosing regions of interest for endodontic therapy.     

Comparison of image performance between cone-beam computed tomography for dental use and four-row multidetector helical CT

The authors evaluated the imaging performance of cone-beam computed tomography (CBCT) for dental use using 3DX multi-image micro-CT (Morita Co., Kyoto, Japan) and four-row multi-detector helical computed tomography (MDCT) using an Asteion (Toshiba, Tokyo, Japan). A dried right maxillary bone was cut into eight slices 2 mm thick toward the zygomatico-palate and used as a phantom. Images of the phantom were then taken using 3DX and MDCT. The images of two bone slices were evaluated by five dentists for image quality and reproducibility of cancellous bone, as well as enamel, dentin, pulp cavity, periodontal ligament space, lamina dura and the overall image. Using the MDCT images as the standard, the 3DX images were evaluated with a subjective 5-level scale: 3 for an image equal to the MDCT image, 4 or greater for better, and 2 or lower for worse. The scores for all parameters exceeded 4 points. Maximum mean score was 4.8 for the lamina dura. Statistically significant differences were found for all items (P < 0.01). Our subjective evaluation of imaging performance clarified that 3DX was superior to MDCT. The results of this study suggest that 3DX is useful for imaging in the dental field.     

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.     

Three-dimensional facial imaging: accuracy and considerations for clinical applications in orthodontics

This study determined the accuracy of a camera system capable of recording three-dimensional facial images. A Rainbow 3D Camera Model 250 system (Genex Technologies Inc, Kensington, Md) was used to capture images of specific models: (1) a precalibrated precision model and (2) a mannequin model that served to simulate the human condition. To assess the accuracy of the camera system, repeated images of both models were recorded at two time points, one week apart. Repeated measurements of specific distances were recorded directly on the models and from each image. Means and standard deviations were calculated for all the repeated measurements at each time point. A two-tailed t-test was used to test for significant differences between (1) each distance measured directly on the precision model and the same distance measured on the images of the precision model, (2) each distance measured directly on the mannequin and the same distance measured on the images of the mannequin, and (3) the mean differences between the same distances measured at the two times. The findings showed that substantial image distortion occurred when images of sharp angles (90 degrees) were captured. Also, those images captured from the frontal perspective +/- 15 degrees were the most accurate.     

Diagnostic advantages and possibilities for secondary reconstruction of NewTom 9000 data sets using eFilm

In order to facilitate diagnosis of images generated with the NewTom 9000, the professional DICOM viewer eFilm Workstation was used for evaluation. Primary reconstructions of patient data of one hundred NewTom 9000 examinations were exported to the DICOM format and subsequently imported in the DICOM viewer eFilm Workstation. Multiplanar reconstructions (MPR) and three-dimensional reconstructions were computed for diagnostic purposes. All desired perspectives can be viewed with this software with CT-like printouts, offering several additional features and an uncomplicated print modus. The DICOM viewer eFilm Workstation is an easy-to-use alternative to the standard software provided by quantitative radiology.     

The use of a 3D laser scanner using superimpositional software to assess the accuracy of impression techniques

Objective. Several studies have made comparisons in the dimensional accuracy of different elastomeric impression materials. Most have used two-dimensional measuring devices, which neglect to account for the dimensional changes that exist along a three-dimensional surface.

Purpose. The aim of this study was to compare the dimensional accuracy of an impression technique using a polyether material (Impregum) and a vinyl poly siloxane material (President) using a laser scanner with three-dimensional superimpositional software.

Materials and methods. Twenty impressions, 10 with a polyether and 10 with addition silicone, of a stone master model that resembled a dental arch containing three acrylic posterior teeth were cast in orthodontic stone. One plastic tooth was prepared for a metal crown. The master model and the casts were digitised with the non-contacting laser scanner to produce a 3D image. 3D surface viewer software superimposed the master model to the stone replica and the difference between the images analysed.

Results. The mean difference between the model and the stone replica made from Impregum was 0.072 mm (SD 0.006) and that for the silicone 0.097 mm (SD 0.005) and this difference was statistically significantly, p=0.001.

Conclusions. Both impression materials provided an accurate replica of the prepared teeth supporting the view that these materials are highly accurate.     

Maxillofacial cone beam computed tomography: essence, elements and steps to interpretation

Maxillofacial cone beam computed tomography (CBCT) is one of the most significant advances in dental imaging since rotational panoramic radiography. While the acquisition of CBCT data is technically simple, numerous parameters should be considered so that CBCT imaging is performed appropriately and 'task specific'. This involves an understanding of not only exposure (e.g. geometric and software parameters to minimize patient dose, while sustaining diagnostic image quality) but also image formatting options to maximize image display. CBCT images contain far more detailed information of the maxillofacial region than do panoramic or other 2-D images and necessitate a thorough knowledge of the 3-D anatomy of the region and considerations of variability in the range of the anatomically normal. These principles, procedures and protocols, together with the interpretation of CBCT images form the basis of best practices in maxillofacial CBCT imaging. This communication aims to provide: (1) an overview of the fundamental principles of operation of maxillofacial CBCT technology; (2) an understanding of 'task specific' equipment, image selection and image display modes; and (3) a systematic methodology for sequencing interpretation of CBCT images.     

A preliminary study of the use of peripheral quantitative computed tomography for investigating root canal anatomy

Aim  To evaluate the use of peripheral quantitative computed tomography (pQCT) for qualitative and quantitative analysis of root canal anatomy and for assessing the extent of canal enlargement during root canal instrumentation.
Summary  The volume variation achieved by S1 ProTaper instruments in the coronal third of the root canals was analysed using peripheral computed tomography. The tooth was scanned in the horizontal plane producing 36 consecutive cross-sectional images. All images were the result of 360 projections with a section thickness of 250 μm, a distance between slices of 0.5 mm and an in-plane pixel size of 70 × 70 μm. The evaluation was completed before and after S1 ProTaper instrumentation (with or without circumferential filing) of one root canal of a freshly extracted maxillary first premolar tooth. The acquired images were realigned geometrically and processed using a 3D visualization software. pQCT scanning allowed 3D reconstruction of the root canal anatomy and the assessment of the extent of canal enlargement during root canal instrumentation with lateral displacement of canal walls and hence volume change being greater than the coefficient of variation. The densitometry evaluation showed uniform density along the root canal wall.
Key learning points • pQCT scanning allowed 3D reconstruction of the root canal anatomy and the assessment of the extent of canal enlargement during root canal instrumentation.
• pQCT shows promise for allowing qualitative and quantitative analysis of endodontic procedures.     

A comparison of a new limited cone beam computed tomography machine for dental use with a multidetector row helical CT machine

OBJECTIVE: We sought to compare a new limited cone beam computed tomography (CT) machine for dental use (3DX) with the multidetector CT machine for image quality and skin doses. STUDY DESIGN: Images of the right maxillary central incisor and the left mandibular first molar of an anthropomorphic phantom were taken by both the 3DX and the multidetector CT. A 5-point method was used to evaluate the depiction of cortical and cancellous bone, enamel, dentin, pulp cavity, periodontal ligament space, lamina dura, and overall impressions. Furthermore, the skin doses for both modalities were compared. RESULTS: The image quality of the 3DX was better than the multidetector CT for all items (P < .01). Moreover, the mean skin doses with the multidetector CT were 458 mSv per examination, whereas the doses with the 3DX were 1.19 mSv per examination. CONCLUSIONS: These results clearly indicate the superiority of the 3DX in the display of hard tissues in the dental area while substantially decreasing the dose to the patient.     

Three phosphor plate systems and film compared for imaging root canals

AIM: The aim of this study was to compare three phosphor plate intraoral imaging systems (Digora (DA), Digident (DT), Denoptix (DX)) and E-speed conventional film (CF) for the imaging of root canals. METHODOLOGY: Sixty extracted permanent teeth were exposed using CF, DA, DT and DX. The length of root canal visible from its most apical extent to a line drawn at the level of the cementoenamel junction was measured and this was expressed as a percentage of the distance between the radiographic apex and the cementoenamel line. All images were examined concurrently by two examiners. Films were viewed under standardized conditions and DA, DT and DX images were viewed directly from the monitor screen. The images on the monitor were enhanced to give the subjectively clearest image. RESULTS: The mean percentage of canal visible on CF was 90%, DA 78%, DT 81% and DX 83%. The difference was significant for CF-DA (P < 0.001) and CF-DT (P = 0.001). There was no statistically significant difference for CF-DX or between any of the three phosphor plate imaging systems. CONCLUSIONS: It is concluded that a greater length of root canal was visible on conventional film than on three phosphor plate imaging systems and that this may be of clinical significance.     

Further development of a versatile computer-assisted learning program for dental education with an exemplifying application on how to logically arrange and mount periapical and bitewing radiographs

Objectives To develop interactive computer-assisted learning software for teaching dental students to logically arrange periapical and bitewing radiographs. Methods Using the Microsoft Visual Basic.NET programming language, we developed software comprising an original object menu window, workspaces, and functions for radiograph shuffling, rotating, mounting, clock, evaluation, score, easy addition of images, a virtual teacher, and help menus. We also developed a program called “Mounting of Dental Radiographs,” which is composed of dental images, a menu window, workspaces, and functions. Results On starting the program, randomly ordered radiographs from a full-mouth X-ray exam are presented, and the clock starts. The student selects one image at a time and places it in the proper folder. An image may need to be rotated or turned. When all images are mounted, the virtual teacher checks the results. If the images have not all been placed correctly within the time limit, the student is given two more attempts before being told, “You lost.” This software can be easily and quickly modified, and dates and scores can be saved automatically. Conclusions We developed a versatile, interactive software program to help students understand how to mount dental X-ray images. It can be modified easily to suit the needs of different students.     

Considerations for the development and standardization of an intra-oral image reference system under the DICOM standard

Objectives

The purposes of this study were to identify the problems encountered during the operation of a hospital-based intra-oral (IO) image viewing system and to discuss measures for improvements required for its replacement with a more functional and standardized system.

Methods

We implemented a hospital information system consisting of a picture archiving and communication system (PACS) and a radiology information system, and developed our own IO image viewing system, thus achieving a hospital-wide filmless PACS operation. Dentists designated the tooth site to be X-rayed via an order form, and technicians took radiographs of the teeth. The images were then converted to electronic data and dental location information was assigned by DICOM modality worklist management (MWM), followed by transmission to the PACS. Images stored in the PACS were viewed in examination rooms via the image viewing system.

Results

This system enables viewing of images with the same layout used for analog film mounts, as well as the production of a matrix view arranged in a temporal sequence, which is useful when searching for previous images or making comparisons over time. However, problems were encountered in the display format and in the assignment of tooth codes that did not reflect the actual IO condition.

Conclusions

IO images could be displayed through the viewer while maintaining a similar display format to that of film images. However, the image position information should be managed separately for display purposes. Support functions to ensure that information on the actual IO condition is correctly reflected are also required.     

The usefulness of three-dimensional imaging in the diagnosis and treatment of clinically ambiguous gingival swelling

We evaluated and treated a 54-year-old woman with gingival swelling. Conventional intraoral and panoramic radiography did not provide sufficient information for either determining the cause of gingival swelling or planning treatment of clinical symptoms. The 3D Accuitomo XYZ Slice View Tomograph (3DX) is a compact dental computed tomography device that allowed for accurate identification and optimal treatment of the causes of gingival swelling. At four years after treatment, 3DX radiographs showed no abnormalities in treated teeth or healing of surrounding structures. We conclude that high-resolution 3D images obtained with 3DX promise to be very effective for diagnosing oral diseases and determining effective treatment.     

COMPARISON OF RADIOGRAPHIC MEASUREMENTS OBTAINED WITH CONVENTIONAL AND INDIRECT DIGITAL IMAGING DURING ENDODONTIC TREATMENT

The aims of this study were to evaluate the quality of indirect digitized radiographic images taken during endodontic procedures and to compare the measurements recorded with this technique to those obtained from conventional radiographs. Two-hundred conventional periapical radiographs taken at the undergraduate Endodontics Clinic of the Dental School of Bauru were digitized. The conventional and indirect digitized images were compared by three examiners as to the quality and accuracy of the measurements recorded during endodontic treatment, in canal length determination, gutta-percha adaptation, lateral condensation and final obturation. The conventional radiographs were observed on a film viewer, surrounded by a dark card, and measured with magnifying glass and a millimeter ruler; the indirect digitized images were evaluated on the Digora^® for Windows software, with free utilization of the bright/contrast tool. Unlike the conventional radiographic images, all indirect digitized images were considered as having a high quality. The distance between the filling material and the root apex was 0.117 mm larger, on average, for the Digora^® system (p<0.01). The measurements achieved by the investigated radiographic methods were clinically similar and they are thus equivalent. Changes in brightness and contrast of the images using Digora^® software improved the diagnosis.     

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。     

Video reconstructions in dentistry

Authors – Farag AA, Eid A Objectives – To present two practical techniques for three‐dimensional (3D) modeling of the human jaw from a sequence of intra‐oral images. Design – A data acquisition system consists of: 3D digitizing arm, CCD camera and a laser projector in addition to a software module of two 3D modeling techniques; shape from shading (SFS) and space carving (SC). Setting and sample population – Several experiments have been conducted on a sample of students at the Computer Vision and Image Processing (CVIP) Laboratory at the University of Louisville, Louisville, KY. Other experiments were performed on solid models of human jaw. Experimental variable – The SFS technique, using perspective projection and camera calibration, extracts the 3D information from a sequence of two‐dimensional images of the jaw. Data fusion of range data and 3D registration techniques develop the complete jaw model. The SC approach is implemented on a sequence of calibrated images. On the two reconstructions, we fit a mesh model to the data, in order to create a solid 3D model. Outcome measure – The accuracy of the reconstructed 3D model of human jaw is calculated based on the measurements on real jaws. Results – The SFS‐based technique seems to provide more faithful information about the shape of the tooth tops. However, the SC algorithm successfully reconstructed 3D models of the human jaw with sub‐millimeter accuracy, which is as accurate as (or even better than) the first technique without using any range measurements or laser projectors. The average error in distance calculation was found to be 0.74 mm, which is an acceptable resolution for many orthodontics and maxillofacial applications. Conclusion – Accurate 3D reconstruction of the human jaw enables many orthodontics and dental imaging research findings to be applied directly to a digital jaw model – not to a cast – using computer vision and medical imaging tools.     

正常人外鼻缺损种植区域三维测量

目的:为外鼻缺损的种植体植入提供影像解剖学资料.方法:使用mimics10.01软件对100 例正常人(男性50 例,女性50 例)头颅螺旋CT三维重建影像进行测量.结果:(1)中切牙根尖至前鼻底最小距离均值为13.03 mm(男),11.06 mm(女),侧切牙根尖至前鼻底最小距离均值为15.95 mm(男),13.04 mm(女);(2)侧切牙区上颌骨腭突最小厚度均值为9.96 mm;(3)中切牙区牙槽突上方最小骨厚度均值为11.12 mm,侧切牙区牙槽突上方最小骨厚度均值为11.24 mm;(4)眉间点位于窦腔部位时骨厚度均值为3.57 mm.结论:前鼻底侧切牙区域为较佳种植区,常规可纵向植入2 枚长度4～8 mm种植体,种植方向可根据需要选择向前倾斜或者向后倾斜;当纵向骨量不足时,可选择于侧切牙区域横向植入2 枚长度4～8 mm的种植体;眉间点作为种植体植入部位应慎重.     

A methodology for quantitative evaluation of root canal instrumentation using microcomputed tomography

AIM: The aim of this paper was to present an objective methodology for quantitative evaluation of root canal instrumentation using microcomputer tomography, together with developed software based on a constructed mathematical model. METHODOLOGY: A desktop X-ray micro-CT scanner (SkyScan 1072) was used to provide data sets of an extracted mandibular molar before and after instrumentation (ProFile 0.04 Taper instruments, Dentsply Maillefer, Ballaigues, Switzerland) that were stored for later use by software. A volume visualization package (T3D) was applied to obtain 3D renderings of the molar to illustrate the qualitative visualization capacity. Next, medical image volume fusion software was used to allow alignment of pre and post image volumes. Finally, software was developed to make quantitative measurements and to provide additional qualitative information on the registered image volumes. This procedure implemented a true 3D mathematical model for quantification of instrumentation effects. Using a local co-ordinate frame, perpendicular reslices were made at five different levels within the mesio-buccal canal to evaluate transportation and centring ability. RESULTS: At first accurate and detailed 3D renderings were obtained. The general and local canal shape before and after preparation could visually be examined in 360 degrees rotation. Numerical values were obtained for volume, volume changes and transportation. Centring ability was calculated by centring ratio and centre movement. CONCLUSIONS: This methodology is a new and objective way for quantitative evaluation of root canal instrumentation using microcomputer tomography and dedicated software.     

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.