Applications of xeroradiography in dentistry

Facial soft tissue thicknesses in craniofacial identification: Data collection protocols and associated measurement errors

Facial soft tissue thicknesses (FSTT) form a key component of craniofacial identification methods, but as for any data, embedded measurement errors are highly pertinent. These in part dictate the effective resolution of the measurements. As herein reviewed, measurement methods are highly varied in FSTT studies and associated measurement errors have generally not been paid much attention. Less than half (44%) of 95 FSTT studies comment on measurement error and not all of these provide specific quantification. Where informative error measurement protocols are employed (5% of studies), the mean error magnitudes range from 3% to 45% rTEM and are typically in the order of 10-20%. These values demonstrate that FSTT measurement errors are similar in size to (and likely larger than) the magnitudes of many biological effects being chased. As a result, the attribution of small millimeter or submillimeter differences in FSTT to biological variables must be undertaken with caution, especially where they have not been repeated across different studies/samples. To improve the integrity of FSTT studies and the reporting of FSTT measurement errors, we propose the following standard: (1) calculate the technical error of measurement (TEM or rTEM) in any FSTT research work; (2) assess the error embedded in the full data collection procedure; and (3) conduct validation testing of FSTT means proposed for point estimation prior to publication to ensure newly calculated FSTT means provide improvements. In order to facilitate the latter, a freely available R tool TDValidator that uses the C-Table data for validation testing is provided.

Xeroradiography and its application to dentistry

Xeroradiography is a highly accurate electrostatic imaging technique. In this technique a conventional single-phase dental x-ray unit is used as an x-ray source, but instead of a silver-halide film image, a uniformly charged selenium alloy plate housed in a light-proof cassette is used. In this article the equipment, procedure, properties and artifacts related to the xeroradiographic technique are described. An evaluation of the xeroradiographic images is also presented. Xeroradiography, which requires only about one-third of the dose required for conventional radiographs, is a valuable alternative to conventional radiography for detecting carious lesions, calculus deposits and periodontal disease. It is also of value in interpreting periapical structures.

A comparison between xeroradiographs and conventional radiographs as an aid in root canal therapy for maxillary molars

The purpose of this study was to compare the quality of images obtained with dental xeroradiography to that obtained with conventional dental radiography during performance of root canal therapy on maxillary molars. For each step requiring radiographic information during endodontic treatment of 12 maxillary molars, a conventional radiograph and a xeroradiograph were made. This produced four pairs of images for each tooth treated as follows: (1) preoperative, (2) initial files for length determination, (3) master cones fitted, and (4) completed obturation of the root canal systems. The same x-ray machine was used as the source of radiation for all exposures with a setting of 70 kVp and 15 mA and with near identical projection for each pair of images achieved through use of a modified film holder and a custom positioning occlusal index made for each patient. Exposure time for the radiographs was 60 impulses (1 impulse = 1/60 second) and for the xeroradiographs it was 42 impulses. Images of structures and items important in endodontic diagnosis and treatment were rated as unacceptable (0), poor (1), adequate (2), or optimal (3) by four independent evaluators. Analysis of data showed the following: images of bone trabeculae, periodontal ligament spaces, root morphology, root apices, and fine bony abnormalities were judged to be significantly better in the radiographs than in the xeroradiographs (p less than 0.01) whereas there were no significant differences in image quality of pulp chamber morphology, root canal morphology, metallic measuring instruments, or endodontic filling materials.

Exposure reduction in cephalometric radiology: a comprehensive approach

Various methods have been proposed and investigated for the purpose of reducing radiation exposures in cephalometric radiography. The purpose of this investigation was to use various dose-reducing methods from four major categories--(1) rare-earth intensifying screens, (2) rare-earth filtration, (3) prepatient soft-tissue enhancement methods, and (4) films varying in speed and latitude--to determine optimal combinations on the basis of exposure reduction and image quality achieved. In laboratory tests and clinical trials, radiation doses were compared along with various tests of image quality for the standard system currently used at this institution and for experimental systems. Image quality was assessed by standard panel-of-expert methods and more quantitative methods involving optical densitometry, contrast indices, and landmark envelopes of error. Results demonstrated that significant exposure reductions were achievable, often with improved image quality. The degree of exposure reduction was dependent largely upon the type of intensifying screen and to a lesser extent on beam filtration or film types. The greatest reduction in exposures were achieved with techniques using rare-earth beam filtration. Image quality was highest with a new wide-latitude type film. Because such significant reduction in radiation exposure for cephalometrics is possible with new techniques, we conclude that a change from the previous standard should occur. In establishing a new technique, orthodontists should consider adopting rare-earth screens and beam filters, flat-grained films, prepatient soft-tissue enhancement methods, and the elimination of grids.

A critical evaluation of xerocephalometry: absorbed dose and diagnostic information

The present study showed that the thyroid (60X) and active bone marrow (100X) doses are increased when xeroradiography is used in cephalometrics, as compared to a rare earth screen/film system. These results are compared to previously published articles. The rationale for advocating a kVp setting of approximately 100 and a negative development mode is presented. It is recommended that xeroradiographic cephalometric examinations be reserved for special cases in which image quality is a top-priority requirement.

Use of xeroradiography for length determination in endodontics

Files inserted and secured in forty-seven canals of maxillary and mandibular cadaver jaw sections were radiographed by conventional and xeroradiographic means, with the use of positioning devices and beam-guiding instruments. Measurements of the radiographically interpreted distance and the actual distance of files from the anatomic apex were made and compared. The data were analyzed by use of the Student's t test. There was no statistically significant difference between conventional and xeroradiographic methods. Xeroradiographs were subjectively judged better than conventional radiographs for maximum visualization of dental structures important to endodontics. Radiation levels needed for quality radiographs were found to be less with the xeroradiographic process.

A cephalometric appraisal of xeroradiography

The literature on the physics, the radiation hazard, and the current medicodental applications of xeroradiography is reviewed. A study is presented on estimating the effect of a xeroradiographic technique on the degree of inter- and intraobserver error in cephalometric landmark identification, as compared to a radiographic technique. This study involved identification by four observers of sixteen cephalometric landmarks on twelve xeroradiographs and twelve radiographs, on two separate occasions. The conclusions are that neither technique provided a significant reduction in interobserver differences. However, for eight of the thirty-two variables (nasion's Y axis, portion's X and Y axes, basion's X axis, Bolton point's X axis, anterior nasal spine's X axis, menton's Y axis, and the tip of the nose's X axis), as opposed to two (basion's Y axis and gonion's Y axis), xeroradiography produced a significant reduction in intraobserver error in comparison to radiography.

Xeroradiography for intraoral dental radiology. A process description

A novel x-ray imaging system for intraoral dental radiography is described. The imaging process is based on xeroradiographic principles. The surface of a small selenium photoreceptor is electrically charged. After insertion into a light-tight cassette, the photoreceptor is placed intraorally and x-ray exposed like film. The resultant electrostatic charge image is developed in a processor using liquid toner. The toner image is then transferred from the photoreceptor and fixed to a white plastic substrate for viewing. After cleaning, the photoreceptor is available for reuse. In contrast to film images, xeroradiographic images are exposed and processed sequentially. Processing time is approximately 20 seconds. Two image characteristics--edge enhancement and deletion--are primarily responsible for many advantageous qualities of xeroradiographic images over film images. An experimental processor was tested successfully at two dental schools.

Clinical trials of intraoral dental xeroradiography

A new dental xeroradiographic processor was clinically tested. In comparison with conventional radiographs, xeroradiographs often showed more anatomic detail of teeth and bone and required approximately half the exposure time. These characteristics, the speed of operation and the added features for convenience, suggest that xeroradiography may be important to dental radiography in the future.

Imaging properties of intraoral dental xeroradiography

A prototype imaging system for intraoral dental xeroradiography has been described. In vivo evaluations of image quality show that intraoral xeroradiographs are superior to conventional intraoral film radiographs primarily because of the wide latitude and edge enhancement properties of xeroradiography. In addition, intraoral xeroradiography requires only a third of the radiation dose of corresponding intraoral film techniques.

Patient radiation dose in conventional and xerographic cephalography

A comparison of the radiation doses for xeroradiographic and conventional film screen cephalography was made. Alderson tissue-equivalent phantoms were used for patient stimulation. An optimum technique in terms of patient dose and imaqe quality was established for the xeroradhe data indicated that the dose for the Xerox process ranged from five to eleven times greater than that for the conventional process for entrance and exit exposures, respectively. The most commonly reported dose, the entrance dose, was found to be 206 mrad, which is five Imes that for the conventional cephalogram. This dose, however, falls within an acceptable range for other dental and medical radiation doses. It is recommended that conventional cephalography be used for routine purposes and that xeroradiography be reserved for situations requiring the increased image quality that the process affords.

Xeroradiographic detection of tooth and bone pathology

Xeoradiography has gained limited use in oral surgery and orthodontics. Its wide exposure latitude, detailed image, and low operating costs recommend its use in general dentistry. In studies on real and simulted hard-tissue lesions, it was found to be slightly superior to conventional radiography in the detection of small lesions. When intraoral plates are marketed and low-KVP techniques are perfected, xeroradiography could assume an important role in dental radiology.

Intraoral xeroradiography

This study compared the diagnostic usefulness of images of dental structures made with two xeroradiographic (XR) processes with those made by conventional radiography. The xerographic systems employed were a Xerox 125 system (designed for mammography) as well as a new experimental xerographic instrument designed for dental use. Structures evaluated included osseous trabecular detail, caries, dental anatomy, soft tissue, and dental restorations. In general, the resolution and detail of these dental structures were noticeably better on conventional films than on the XR 125 images. In addition, the presence of artifacts around the margins of metallic restorations on the XR 125 image severely inhibited detection of recurrent caries. In contrast, XR images formed by the new experimental process were equal to or superior to conventional films in resolving detail of dental struitures. Also, the experimental XR process required less radiation exposure than conventional radiography.

A comparison of xeroradiographs with conventional lateral skull radiographs

Forty xeroradiographs were compared with forty conventional lateral skull radiographs, using a digitizer.

A double plotting method was used by one observer and the variation between plots was calculated. Xeroradiographs appeared to give better agreement between observations for most, but not all, of the landmarks.

Landmark identification accuracy in xeroradiographic cephalometry

Identification accuracy of fourteen cephalometric landmarks was compared between xeroradiographic cephalograms and conventional cephalograms. Four landmarks--point A, upper incisor tip, infradentale, and menton--were more accurately determined on the xeroradiograph, while two landmarks--point B and condylion--were more accurately determined on the conventional cephalogram. Although not conclusively demonstrated in this study, the xeroradiograph does appear to offer more clarity and detail than the conventional cephalogram. Further investigation of this new diagnostic medium will be necessary before its true significance to dentistry can be evaluated.

The advantages of xeroradiography for panoramic examination of the jaws and teeth

Xeroradiography is an electrostatic imaging method which was significant advantages over conventional radiographic techniques. This article introduces the use of xeroradiography for panoramic examination of the jaws. The resultant images not only contain superior local contrast and detail when compared to conventional panoramic radiographs but also correlate well with histopathologic changes. The investigation indicates that xeroradiography is an important new diagnostic tool for detection of disease of the jaws and teeth.

Xeroradiography of dental structures. I. Preliminary investigations

Xeroradiography has several inherent technical advantages over intraoral film radiography, as well as many convenience features. We found that a conventional dental x-ray unit can act as an excellent source of radiation for xeroradiography of dental structures. Furthermore, high-quality images of soft tissue, bone, and teeth were produced at radiation exposures up to seven times less than for conventional intraoral film radiography. This demonstration of reduced radiation exposure should further encourage research into the applicability of xeroradiography to the imaging of dental structures.

Application of xeroradiography in sialography

Sialography was carried out in healthy volunteers and in patients with Sjögren's syndrome. A comparison was made between xeroradiography and conventional radiography. Superior images were obtained with xeroradiography and this technique also tended to reveal glandular structure which was obscured by overlying bone when using conventional radiography. In addition to this, there was considerably greater latitude in exposure and the skin dose of radiation using xeroradiography was slightly less.