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.     

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.     

Use of a "sandwich" technique to control image geometry in clinical studies comparing intraoral xeroradiographs and E-speed films

A method of superimposing a film on a xeroradiographic (XR) cassette for simultaneous intraoral exposure is evaluated for use as an imaging technique in clinical studies comparing Ektaspeed film and XR images. Sandwich images were indistinguishable from those produced by conventional technique. Pilot studies were conducted with 104 patients who had symptomatic dental problems. No significant differences were found in diagnostic usefulness or image quality between XR and film radiographs when sign test analysis was used. The sandwich technique yielded film and XR images with duplicate image geometry while reducing patient exposures to one half of that used in conventional image comparison protocols.     

Clinical assessment of anatomic positioning and patient comfort for intraoral radiography: a comparison of xeroradiography versus film

The Xerox 110 dental system employs rigid beveled-edge cassettes containing charged selenium-alloy plates for intraoral xeroradiography. This study evaluates the ability of a skilled operator to position these cassettes accurately within the oral cavity as compared to the ability to position conventional film packets using two types of image holders. Results indicate that xeroradiographic cassettes are significantly more difficult to use for complete-mouth radiographs than comparable conventional film packets. Also, the use of xeroradiographic cassettes causes a slight increase in patient discomfort. In addition, two types of rectangular collimating devices were shown to be useful. The greatest shortcoming of the xeroradiographic cassette is not its greater thickness or rigidity but the reduced dimensions of its internal surface area.     

Xeroradiography in root fracture diagnosis

Root fracture is a clinical problem that often is difficult to diagnose. The purpose of this study was to compare diagnostic value of conventional radiographic and xeroradiographic images of experimentally fractured teeth. Forty-five extracted human single-rooted teeth were used. The roots of the teeth were coated with wax to simulate periodontal ligament and invested in acrylic to the cementoenamel junction. An access cavity was prepared and para-post, size 4 to 12 mm, was placed into the root canal. Each tooth with post was placed on the load cell table of an Instron testing machine. The Instron continuously recorded load on a moving graph paper. The load was increased until the tooth fractured. Determination of fracture was made by the sound of a sharp "crack" and by a sudden release of load on the post, as seen on the Instron recording graph. After fracture, conventional radiograph and xeroradiograph were obtained for each tooth by use of the paralleling technique. The x-ray beam angle, film distance, and tooth placement were held constant in both techniques by use of a Rinn instrument. All films were evaluated by use of light from a masked viewbox, while all of the xeroradiographs were viewed in reflected light. A magnifying glass was used to aid in the examination process. The samples were examined and categorized for root fracture by the examiners with the use of the following scores: 0 = unacceptably poor, 1 = poor but diagnostic, 2 = adequate for diagnostic information, and 3 = optimal for diagnostic information.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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.     

Applications of xeroradiography in dentistry-a review.

Xeroradiography is the technique in which electrostatically charged plates sensitive to X-rays are used in diagnostic radiology in place of conventional film. There has however been anxiety that radiation dosage for xeroradiography may be at unacceptably high levels. James et al., however, in 1973 showed that by increasing the kilovoltage to at least 120 the exposure could be reduced by 60 per cent. Using higher kV lateral oblique jaw and lateral and anteroposterior skull xeroradiographs have been produced with lower radiation exposure than conventional film. Bony detail is much more sharply delineated on xeroradiographs and soft tissues are visible on the same picture without use of a grid or wedge filter. These features are of obvious advantage in cephalometrics and orthognathic surgery. Panoramic techniques are potentially the most useful way of applying xeroradiography. The combination of full jaw coverage with the sharp definition only possible at present with intra-oral radiographs would provide more information for the dentist, save time for the radiographer and reduce the dose to the patient. Excellent results have been obtained with autopsy specimens on machines which develop 90kVp, but optimal exposure for a normal adult requires a panoramic X-ray machine development 120 kVp. Xeroradiography has the advantage, therefore, of providing more detail of diagnostic value with lower radiation exposure to the patient. The process requires no silver, which is in increasingly short supply.     

Xeroradiography of dental structures. III. Pilot clinical studies.

A new experimental intraoral dental xeroradiographic system was evaluated for future application in dentistry. Similar projections on conventional film radiographs and experimental dental xeroradiographs were compared visually and radiation exposure for both techniques was measured by thermoluminescent dosimetry. The xeroradiographic system was judged superior for imaging most structures, especially oral soft tissues, subtle bony abnormalities, and fine calculus deposits. Furthermore, xeroradiography requires only one third the radiation exposure of corresponding conventional film techniques. Dental xeroradiography appears to have great promise in radiographic interpretation of oral disease.     

Applications of xeroradiography in dentistry

Xeroradiography is the technique in which electrostatically charged plates sensitive to X-rays are used in diagnostic radiology in place of conventional film. Comparison between these different types of radiographs of both lateral skull and lateral oblique mandibular projections shows xeroradiography to have many advantages. Hard and soft tissue details are more clearly defined and visible on the same picture. Radiation dosage is slightly less and this, combined with the need for fewer exposures, reduces the incident skin dose to the patient. The plates are re-usable and the process requires no silver.These factors strongly suggest that xeroradiography may be of great value in routine dental radiology and further investigation is in progress.     

Xeroradiography of dental structures. II. Image analysis.

Xeroradiography provides an attractive, convenient, low-radiation-dose alternative to conventional intraoral film radiography. In this study the image properties of the two techniques were compared quantitatively and qualitatively. Over all, image quality was very similar, but xeroradiography delivered radiation doses seven to fourteen times less than conventional film radiography.     

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.     

A modified phosphate-bonded casting investment

Abstract – An experimental phosphate-bonded casting investment with negligible setting'expansion and a thermal expansion of 1.6%, sufficient to compensate for the solid thermal shrinkage of conventional dental gold alloys and high-precious alloys for die porcelain fused to metal technique, is described. When used in a ringless casting technique the investment makes it possible to produce cast restorations with a consistent slidefit. In combination with a die spacer technique the new investment makes it possible routinely to produce cast restorations with a consistent and known, degree of loosefu.     

Comparison of dental xeroradiography and conventional film techniques for the frequency and significance of image artifacts

The frequency of occurrence and the classification of image artifacts were determined during a large-scale clinical dental radiographic study in which two conventional film techniques and xeroradiography were used. The resultant 1,220 radiographic images were evaluated for the presence of image artifacts. A list of commonly occurring artifacts was compiled, and frequency tables were constructed. Xeroradiography showed more image artifacts and also a higher retake rate due to artifacts (17.4% for individual images and 4.3% when images were evaluated as part of a complete-mouth survey). Many of the artifacts observed for xeroradiography were related to incomplete operator training and unfamiliarity with specialized imaging techniques.     

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.     

Electronic system for digital acquisition of rotational panoramic radiographs

A prototype system for digital panoramic imaging of the maxillofacial complex has been developed. In this system x-ray film is replaced by an electronic sensor that delivers the image information to a computer for storage in digital format. The images, which are similar to conventional panoramic radiographs, are displayed on a high-resolution video monitor and may be stored on optical disk for future use. Hard-copy output is also available. The present prototype system has been installed on an Orthopantomograph model OP10 panoramic x-ray machine is programmed for operation with this machine, but in principle the system can be installed on any such device. The system may be incorporated into the design of future panoramic x-ray systems or may be used to retrofit panoramic x-ray systems now using photographic film to record the radiographic image. Greater sensitivity of electronic sensors should make possible a reduction of x-ray dose to the patient, compared with film-based systems.     

Complete Denture Education in U.S. Dental Schools

PURPOSE: In 2001, a survey of U.S. dental schools was conducted to determine curricular content, teaching philosophies, and techniques used in clinical complete denture programs. MATERIALS AND METHODS: The questionnaire was mailed to the chairperson of the prosthodontic/restorative department of 54 U.S. dental schools. Of these, 44 schools returned the completed survey, resulting in a response rate of 82%. The mean, median, and range of responses were computed where applicable. RESULTS: Results from this survey show that a large majority of schools are using similar materials in clinical complete denture treatment: irreversible hydrocolloid for preliminary impression (87%); light-cured composite resin for record base fabrication (70%); a semiadjustable articulator (98%); and semianatomic posterior tooth form used exclusively or in combination with other tooth forms (75%). In addition, a large majority of schools are using similar techniques in clinical complete denture treatment: use of a protrusive record (80%); use of extra-oral measurements, speech, and esthetics for establishing the occlusal vertical dimension (59%); use of the conventional compression molding method for processing complete dentures (82%); occlusal equilibration and face-bow preservation (75%); and the clinical remount procedure (91%). A quality control program is present for cases sent to and returned from the laboratory in 73% and 84% of responding schools, respectively. CONCLUSIONS: Clinical complete denture predoctoral programs vary from school to school, yet a large percentage of schools agree on many topics. Only 55% of schools reported incorporating new educational materials such as the use of dental implants and treatment of patients with implant-retained overdentures at the predoctoral level. Sixteen percent are allowing students to graduate without a set number of required complete dentures as has traditionally been the case. Sixteen percent are using newer techniques such as injection molding and microwave processing technique in addition to the conventional processing technique.     

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.     

Radiopacity of resin-based materials measured in film radiographs and storage phosphor plate (Digora)

This study compared the radiopacity of 41 resin-based materials using conventional dental x-ray film (Ultraspeed-D) and a digital system (Digora) based on storage phosphor plate technology. For the film-based technique, optical density measurements were carried out using an X-Rite densitometer. Al equivalents (mm) were calculated as described in the literature using a calibration curve of Optical Density versus the thickness of aluminum. Regarding the digital system after exposures of 0.16 and 0.32 seconds, the images were exported to an image processing software (NIH Image Engineering). An approach similar to that used for optical density was used to generate a calibration curve for gray pixel values. Linear correlations were found between the percentage of fillers by weight and x-ray film radiopacity and the Digora system, and the same coefficient of estimation was recorded (r=0.60; p< or = 0.05). A linear correlation was also observed between the conventional x-ray film technique and the Digora system (r=0.93;p< or = 0.05). Using two different exposure times did not affect the radiopacity. Considerable differences were found among materials of the same category. Flowable resin composites were more radiopaque than dentin, while microfine composites were "radiolucent." Most of the available resin-based materials were more radiopaque than enamel. The radiopacity of resin composites depended on their fillers (percentage and type). Using elements with low atomic numbers (Si) resulted in radiolucent materials, while adding elements with high molecular numbers (Ba, Y, Yb), resulted in radiopaque resin composites. Despite the numerous benefits offered by the digital imaging system (low irradiation dose, instant image, image manipulation), the conventional x-ray film technique seems to be more accurate for radiopacity measurements.     

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.