A pilot study of nitric oxide blood levels in patients with chronic orofacial pain

BACKGROUND

Control of pain is the major goal in the management of chronic orofacial pain (COP) patients. The pathogenesis of COP is currently not well understood. Consequently, the treatment of COP may be suboptimal or even harmful. Based on independent observations, we propose that local elevated levels of nitric oxide (NO) may have a central role in the pathogenesis of COP.

HYPOTHESIS

NO level in the orofacial region of COP patients is elevated. A regional increased level of NO causes excessive vasodilatation. This hyperperfusion is manifested by hyperthermia of the overlying skin, while NO enhances nociception, aggravating orofacial pain. An alternative mechanism involving NO as a neurotransmitter at the CNS level may contribute to orofacial pain, but seems not to account for all the known clinical observations.

METHODS

Two groups of subjects were studied: 5 patients with COP and 59 control subjects. For each subject we collected blood samples for analysis of nitrite\nitrate (or NOx).

RESULTS

(1) NOx blood levels for 5 patients diagnosed with COP was 65.9 microM (SD of 10.4) verses 42.7 microM (SD of 24.2) for 59 control subjects, the difference being statistically significant, t-statistic = -2.12 (P > .05). (2) No statistical difference was found for NOx blood levels for 59 control subjects divided by gender (male vs female), with 23 female controls having NOx blood levels of 42.6 microM (SD of 25.2) and male controls having NOx blood levels of 42.8 microM (SD of 24.0), t-statistic = -0.03, P = .98.

CONCLUSION

This pilot study suggests that NO blood levels may have an association with COP. A better understanding of the mechanism of chronic orofacial pain is expected to lead to more precise diagnostic staging and management of this disorder.

The possible role of nitric oxide in the physiopathology of pain associated with temporomandibular joint disorders

Temporomandibular joint disorders (TMD) pose a significant challenge to the practice of oral and maxillofacial surgery. When painful, TMD are generally associated with hyperthermia of the overlying skin. It is hypothesized that this skin hyperthermia, caused by regional vasodilation, is induced by nitric oxide (NO) produced in the extravascular space of the joint. Extravascular NO can be produced by osteoblasts, chondrocytes and macrophages, or by stimulated neurons. It is suggested that this kind of pain is associated with NO-enhanced sensitivity of the peripheral nociceptors. Verification and clinical implications of the proposed mechanism are discussed.

Thermology and facial telethermography. Part I: History and technical review

This paper is a review of historical trends and technical advances in measurement of skin temperature. Most biochemical processes generate heat which must be dissipated. Skin is the major route for heat dissipation using blood as the heat exchange fluid. Skin temperature is an indicator of aberrations in metabolism, hemodynamics or in neuronal thermoregulatory processes. Since most of the heat dissipation of skin is by infrared blackbody emission, skin temperature should be measured without contact by monitoring the emitted infrared radiation. This has been the basis of telethermography. Recent advances in computing technology combined with advanced infrared sensor technology has led to the development of dynamic area telethermometry (DAT) which promises to be as an important new quantitative method to analyse the pathophysiology of thermoregulatory processes.

Thermology and facial telethermography: Part II. Current and future clinical applications in dentistry

Selected clinical applications using thermal imaging as an aid in dentistry are reviewed. Facial skin temperature can easily be measured in a clinical setting, without direct skin contact, by monitoring the emitted infrared radiation. This is the basis of static area telethermography (SAT) and dynamic area telethermography (DAT). SAT has recently been shown to be of help to the dentist in (1) the diagnosis of chronic orofacial pain, (2) as a unique tool in assessment of TMJ disorders, (3) as an aid in assessment of inferior alveolar nerve deficit, and (4) as a promising research tool. DAT, recently made possible by advances in computing technology combined with advanced infrared sensor technology, extracts quantitative information about hemodynamic processes from hundreds to thousands of digital thermal images of the affected facial areas, measured and collected within less than 3 min. DAT has promise of offering a better insight into aberrations of the neuronal control of facial skin perfusion and aiding our understanding of the correlation between orofacial pain and facial thermal abnormalities. This promising new insight may help in the management of orofacial pain.

Role of nitric oxide in the physiopathology of pain

Many painful disorders, including joint dysfunctions such as rheumatoid arthritis (RA) or temporomandibular joint disorders (TMD), are associated with hyperthermia of the overlying skin. The same is true of certain intractable chronic pain conditions, such as chronic orofacial pain, which may be associated with TMD. We suggest that this skin hyperthermia, caused by regional vasodilation, is induced by extravascular nitric oxide (NO). Extravascular NO can be produced in the affected joint by osteoblasts, chondrocytes, and macrophages, by mechanical stimulation of endothelial cells, or by stimulated neurons. In view of a strong correlation between pain and skin hyperthermia in these disorders, and the evidence that NO enhances the sensitivity of peripheral nociceptors, we also suggest that at least this kind of pain is associated with excessive local level of NO. This hypothesis can be verified by dynamic area telethermometry, assessing the effect of NO on the sympathetic nervous function. This mechanism, which is in line with the general role of NO as a mediator between different organ systems, also may be relevant to any pain associated with enhanced immune response. Clinical implications of the proposed mechanism are discussed.

Lateral cephalometric radiographs: an aid in detecting patients at risk of stroke

Stroke is often caused by atherosclerotic lesions in the bifurcation of the common carotid artery. The authors evaluated conventional lateral cephalometric radiographs of 1,063 healthy men aged 25 to 85 years for the presence of such lesions. Approximately 2 percent of these people had lesions, which were at the level fo the third and fourth cervical vertebrae and were superimposed over these structures, the pre-vertebral fascia and the pharyngeal air space. People with atherosclerotic lesions should be referred to their physicians because timely medical, surgical and lifestyle interventions can prevent strokes.

A 6-year clinical assessment of electronic facial thermography

OBJECTIVE

To report the findings a 6-year clinical application of ET on patients with orofacial pain.

METHODS

ET was conducted (in a blinded manner) using an Agema 870 unit at 0.1 degree C thermal accuracy. A newly devised thermal classification system was applied: 'normal' when zone delta T was from 0.0 to +/-0.25 degree C, "hot' when zone delta T was > +0.35 degree C, 'cold' when zone delta T was < -0.35 degree C, and 'equivocal' when zone delta T was +/-(0.26-0.35) degree C. Study populations consisted of 164 dental patients mainly with diagnostic problems and 164 matched (control) subjects.

RESULTS

Our prospective, matched study determined that subjects with 'hot' thermograms had the clinical diagnoses of sympathetically maintained pain, peripheral nerve mediated pain, TMJ arthropathy, and maxillary sinusitis. Subjects with 'cold' thermograms were found to have the clinical diagnoses of peripheral nerve-mediated pain and sympathetically independent pain. Subjects with 'normal' thermograms were found to have the clinical diagnosis of cracked tooth syndrome, trigeminal neuralgia, pretrigeminal neuralgia, or psychogenic facial pain. The new system of thermal classification resulted in 92% (301 of 328) agreement in classification of pain patients and matched controls.

CONCLUSION

These studies suggest that ET has promise in aiding the formation of a differential diagnosis of orofacial pain and may help in understanding mechanisms of pain as well as directing therapies.

Electronic thermography for the assessment of acute temporomandibular joint pain

Electronic thermography (ET) has the potential to be a nonionizing, noninvasive, low-cost diagnostic alternative for evaluating temporomandibular joint (TMJ) disorders. This study was designed to evaluate the use of ET as a diagnostic aid in the assessment of patients with acute TMJ pain. Computer measurements made using facial thermography were able to distinguish normal patient populations from symptomatic patients with acute TMJ pain. Additional studies are needed before thermographic diagnosis of TMJ disorders will be clinically accepted.

Thermographic assessment of temporomandibular disorders symptomology during orthodontic treatment

The relationship between orthodontic treatment and temporomandibular disorder (TMD) symptoms has been the focus of many subjective studies. Objective studies are now needed. Electronic thermography (ET) has shown promise as an objective tool for assessing temporomandibular disorders. Clinical TMD examinations and ET were performed on 21 control subjects, 18 subjects undergoing orthodontic treatment, and 20 subjects with TMD pain. Standardized blinded clinical examinations that used algometry were conducted. The ET was performed with an Agema 870 unit (Agema Infrared Systems, Secaucus, N.J.) under controlled conditions. Data were analyzed to determine the usefulness of ET as an objective measure of TMD symptoms. The ET alone identified the subjects with painful clicking TMD with a sensitivity of 87%. Subjects with no painful clicking (controls) were identified with a specificity of 86%. The ET findings also had a strong correlation with pain to muscle palpation. This study indicates that ET shows promise as an objective tool for selecting normal subjects from subjects with TMD symptoms. The ET could prove to be valuable in accessing the relationship between orthodontic treatment and TMD symptoms in future longitudinal studies.

Electronic thermography for the assessment of inferior alveolar nerve deficit

Neurosensory deficit is one of the major complications encountered in oral and maxillofacial surgery. OBJECTIVES. To determine the efficacy of electronic thermography in objectively assessing neurosensory deficits of the inferior alveolar nerve. STUDY DESIGN. Three studies were conducted measuring skin temperature over the chin region of the face at 0.1 degree C accuracy. RESULTS. (1) Thermal symmetry of the chin region in normal subjects (delta T = 0.2 degree C, SD = 0.02 degree C); (2) Induction of transient thermal asymmetry by local anesthetic injection (delta T = +0.4 degree C, SD = 0.2 degree C); (3) nine subjects with neurologic alterations of the inferior alveolar nerve (delta T = +0.5 degree C, SD = 0.2 degree C). Statistically significant differences were found between control group and experimental groups at p < 0.001 with the use of the Student's t test. CONCLUSIONS. These studies indicate that electronic thermography is capable of detecting sensory changes caused by inferior alveolar nerve injury or by pharmacologic nerve block.

Electronic thermography for the assessment of mild and moderate temporomandibular joint dysfunction

Today facial heat emission patterns may be rapidly obtained and quantified with the use of advanced electronic thermography units that have the promise of being a nonionizing, noninvasive, low-cost diagnostic alternative for the evaluation of temporomandibular joint disorders. This study design measured the use of electronic thermography as a tool to select between asymptomatic (control) subjects and a patient group with mild to moderate temporomandibular joint disorders. Study populations consisted of 24 asymptomatic (control) subjects and 20 patients with (1) either locked or unlocked temporomandibular joints, (2) varying degrees of limitation of mouth opening, (3) mild to moderate muscle pain, and (4) mild to moderate temporomandibular joint arthralgia. The results indicated that the control group demonstrated a high level of thermal symmetry over the temporomandibular joint region. The patient group demonstrated a low level of thermal symmetry with a delta T value of 0.4 degrees C. The control group was selected from the patient group with 85% sensitivity (17 of 20), and 92% specificity (22 of 24), and 89% overall accuracy (39 of 44), when selecting among the 44 subjects used in this study. The conclusion therefore is that electronic thermography shows promise as a method of diagnosing mild to moderate temporomandibular joint disorders.

Electronic facial thermography: an analysis of asymptomatic adult subjects

Vascular heat emissions that present on the human face can provide physiologic indicators of underlying health or disease. Electronic thermography may serve as a nonionizing, noninvasive alternative for solving diagnostic problems. This study was designed to quantify normal values of vascular heat emissions of the face. Electronic thermograms were taken of 102 subjects using an Agema 870 unit, at 0.1 degree C accuracy, under controlled conditions. Results indicated a high degree of mean thermal symmetry about the face. Using frontal and lateral electronic thermogram projections, the mean temperatures of 25 selected right-versus-left-side anatomic zones were within 0.1 degree C of each other. Analysis of frontally and laterally projected electronic thermograms also produced a new mapping of thermally distinct facial zones. Of greatest importance, the right-versus-left-side thermal differences (delta T) between many specific facial regions for individual subjects were demonstrated to be much smaller (< 0.4 degrees C) than previously reported delta T values of the same facial regions in a wide variety of chronic disorders. These differences in delta T values between asymptomatic subjects and patients with various facial pain syndromes may prove to be useful thresholds for determining normal versus abnormal facial thermograms.

Panoramic dental radiography as an aid in detecting patients at risk for stroke

PURPOSE

Atherosclerotic lesions in the region of the bifurcation of the common carotid artery and in the internal carotid artery are the most common cause of stroke. On occasion these lesions are calcified and visible on a panoramic dental radiograph.

METHODS

Six subjects receiving outpatient dental treatment and denying a history of previous transient ischemic attacks or stroke had bilateral calcified carotid arterial lesions noted on their routine panoramic dental radiograph.

RESULTS

Electronic thermography (ET) demonstrated that these patients had significant temperature differences bilaterally between their medial supraorbital region and the ipsilateral remainder of their forehead when compared with control subjects. These findings are consistent with the presence of calcified stenotic intraluminal plaques altering blood flow, tissue perfusion, and skin temperature readings. The presence of stenotic plaques was verified by Doppler spectral analysis and imaging.

CONCLUSION

ET of the face, currently considered an investigational procedure, demonstrates promise as an ancillary imaging system capable of confirming the diagnosis of patients at risk of stroke. Such individuals should be referred to an appropriate physician for consideration of medications and/or surgical removal of the plaque. In selected individuals, these are safe and relatively reliable methods of preventing stroke.

Thermographic assessment of reversible inferior alveolar nerve deficit

The purpose of this study was to investigate thermography's potential as a diagnostic alternative for evaluating neurosensory deficits of the inferior alveolar nerve. Electronic thermography was used to evaluate the alterations in facial thermal patterns attendant to a conduction defect of the inferior alveolar nerve induced in 12 subjects using 2% lidocaine. The rates of onset and duration of sensory block, as visualized by thermography, were related to the results of conventional neurosensory testing. Comparison of the rate of response change within each measurement system revealed that changes in facial skin temperature manifest the induced deficit earlier than discriminative tests. Also, the prolonged elevation of thermal asymmetry suggested that electronic thermography has the ability to detect subtle changes in nerve function that are not discernible by physical neurosensory tests relying on patient response. Although cutaneous temperature increases were highest in the field of observation near the sensory distribution of the mental nerve, an inexplicable warming of the contralateral side of the face and neck was also observed. These attendant findings emphasize the need for further studies on the pathophysiologic mechanisms of facial thermal changes to better understand thermography's diagnostic accuracy and clinical utility for monitoring inferior alveolar nerve dysfunction.

Evaluation of Niobi-X filtration in intraoral radiology

This investigation studied the effect of adding niobium filtration to the dental x-ray beam assessing reduction in patient x-ray exposure and changes in image quality. Clinical radiographs were made with the use of D- or E-speed film with either aluminum or aluminum plus 25 microns or 30 microns of added niobium filtration. Similar exposures were made on a head phantom, measuring the absorbed dose to radiosensitive sites in the head and neck. Results indicated that the addition of 25 microns or 30 microns of niobium filtration does not significantly degrade the subjective image quality of diagnostic radiographs when D-speed film is used. With E-speed film, however, the addition of niobium filtration significantly degrades the diagnostic image quality. The addition of niobium filtration results in a 20% to 30% reduction in patient dose. We conclude that the use of niobium filtration with D-speed dental film is a positive contribution to patient care.

Future applications of electronic thermography

The dental literature does not yet indicate the full range of facial thermographic findings in health and disease. Thermography is not useful in assessing some common dental problems, such as periapical granuloma. Promising reports, however, support its use in the diagnosis of neuralgias and atypical odontalgia, TMJ, nerve damage and repair after oral surgery, and in evaluating local dental anesthesia. Unfortunately, few if any of these studies were properly designed or conducted, limiting current attempts to define the value of thermography in dentistry. Until this situation resolves, ET of the face, for use in dentistry, can only be considered an investigational procedure. More research will clarify the precise contribution of thermography to dental problems.

Electronic thermography in the assessment of internal derangement of the temporomandibular joint. A pilot study

Current diagnostic imaging methods to evaluate internal derangement of the temporomandibular joint (TMJ) include arthrotomography, arthroscopy, computed tomography, and magnetic resonance imaging. Most of these techniques either require ionizing radiation or are invasive, and all are expensive. Electronic thermography (ET) is an alternative diagnostic imaging modality that is inexpensive, nonionizing, and noninvasive. The purpose of this pilot study was to assess ET in the diagnosis of internal derangements of the TMJ. The study population consisted of 11 patients with internal derangement, and 12 normal patients. ET was conducted with an infrared thermographic unit, at 1.0 degrees and 0.5 degrees C sensitivity. Results from subjective blinded interpretations by two experts for the diagnosis of internal derangement of the TMJ were as follows: sensitivity, 86% (+/- 7.8%); specificity, 78% (+/- 7.1%). Results from objective measurements of thermal symmetry of the TMJ region were as follows: normal subjects, 89.3% (+/- 3.0%); internal derangement patients, 66.1% (+/- 16.2%); t21 = -4.89, p less than 0.01. In conclusion, ET appears to have some promise as a diagnostic aid in the evaluation of internal derangement of the TMJ. Additional, more extensive studies are needed before thermographic diagnosis of internal derangement is accepted clinically.

A subjective study of dental diagnostic utility comparing xeroradiography and film radiography

This study determined the perceived strengths and weaknesses of xeroradiography, D-speed film, and E-speed film for intraoral radiography. Results indicated that xeroradiography was preferred for the imaging of structures useful in periodontics and endodontics whereas film demonstrated a low level of image artifacts and was judged to be better for the imaging requirements of routine restorative dentistry. D-speed film was rated higher than E-speed film. These subjective assessments are similar to previously reported pilot studies but differ from previously published objective studies, which showed no significant difference between the three imaging techniques. Although there are substantial subjective differences between xeroradiography, D-speed film radiography, and E-speed film radiography, all the techniques provide more than the threshold level of necessary diagnostic information and all techniques portray adequate information for evaluation of common abnormalities encountered in the oral cavity.

Electronic thermography in the diagnosis of atypical odontalgia: a pilot study

Atypical odontalgia (AO) is a dental condition that is usually diagnosed by exclusion after failure of multiple dental treatments. A functional definition of AO includes (1) continuous pain in and about a tooth or teeth, (2) pain present for longer than 4 months, (3) inadequate local cause (no abnormality detected on dental radiographs), and (4) anesthetic blockade gives equivocal relief of toothache. The purpose of this study was to assess the potential role of electronic thermography in the diagnosis of AO. Results from measurements of facial thermal symmetry indicated that normal subjects = 83.5%, AO group = 65.8% (p less than 0.01). Electronic thermography interpreted by thermography experts has promise as a diagnostic test for AO among patients with toothache for which the dentist can find no convincing dental explanation.

Electronic thermography of normal facial structures: a pilot study

New electronic thermographic instruments capable of routine clinical examination need to be evaluated for their potential as a diagnostic aid in dentistry. This study assessed thermal symmetry of the face and neck in 20 normal subjects with the use of frontal and lateral views, at 1.0 degree C and 0.5 degree C sensitivity, under controlled conditions. Electronic thermographic images were analyzed for thermal symmetry, by means of a grid matching technique, in 12 anatomic regions and the overall face. Results indicated that thermal symmetry for the entire face was high (70.2%). The 12 specific facial areas demonstrated varying levels of thermal symmetry. Regions of high symmetry on frontal projections included the anterior portion of the neck (82.0%), the TMJ (80.0%), the lower lip (78.6%), and the upper lip (77.3%). The temporal region (46.7%) was found to be of relatively low thermal symmetry. Regions of high symmetry on lateral projections included the nasal region (69.5%) and the inframandibular region (67.0%). The posterior neck region (44.2%) was found to be of relatively low thermal symmetry. In general, normal subjects demonstrated high levels of thermal symmetry over most regions of the face. This pilot investigation is an early step in the evaluation of electronic thermography for future use in dentistry.

Clinical recommendations for the use of D-speed film, E-speed film, and xeroradiography

This article assesses the diagnostic utility, radiation dose, equipment reliability, patient acceptance, and costs associated with D-speed film, E-speed film, and dental xeroradiographs for intraoral imaging. From the analysis and review of laboratory studies and clinical trials, conclusions and recommendations are offered.

A clinical comparison between xeroradiography and film radiography for the detection of recurrent caries

Xeroradiographs and conventional film radiographs (D- and E-speed) were compared in a clinical study with the use of one-half complete-mouth radiographs for the detection of recurrent dental caries in 200 teeth. The results indicated that film was the most useful in identification of noncarious restored teeth (91% correct versus 79% correct for xeroradiography); however, xeroradiography was better than film for detection of recurrent caries (67% versus 53%). With ROC analysis, both film and xeroradiography were equally useful, having the same ROC value of 0.78. At rates of 67% and 53% for detection of the presence of recurrent caries, neither imaging system can overcome basic geometric limitations of superimposition of metallic restorations. Thus, there is the continued need for careful clinical assessesment of existing restorations for the presence of recurrent caries.

A clinical comparison of xeroradiography and film radiography for the detection of proximal caries

Xeroradiographs and conventional film radiographs (D- and E-speed) were compared in a clinical study with the use of 1 complete-mouth radiographs for (1) the presence of interproximal caries and (2) the determination of the depth of interproximal caries with the use of 200 tooth surfaces. In addition, an analysis of correct classification rates making a comparison of the same techniques was conducted. The results with the use of ROC analysis indicated that when a comparison was made of xeroradiography and D- and E-speed film, all techniques were equally useful. A broad range of observer ROC area values was found, indicating that diagnostic performance varies greatly with observer. The results of the diagnostic decisions made on carious surfaces versus noncarious surfaces indicated that all techniques tested were similar: 90% correct for noncarious surfaces and 77% correct for carious surfaces.

E-speed dental films processed with rapid chemistry: a comparison with D-speed film

Image quality of E-speed film processed in four rapid chemistry solutions was evaluated and compared to that of D-speed film. One-hundred-twenty films (60 E-speed and 60 D-speed) were exposed with the use of a quality-control phantom and processed in four different rapid solutions. The images were evaluated for speed, contrast, fog and base, resolution, and granularity, and the useful lifetime of the solutions was determined. E-speed film processed with rapid chemistry produced images equal in quality to D-speed film in the range tested (70 to 90 kVp). Fog and base levels of E-speed film were greater than those of D-speed film. The resolution and granularity of the images were equal and were judged adequate in both film types, regardless of the chemistry used. Rapid processing solutions were found to have a 10% to 15% shorter useful lifetime with E-speed film than with D-speed film. The processing of E-speed film in rapid chemistry is recommended for emergency care and endodontics.

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.

Frequency of artifacts with xeroradiography using artifact-reduction techniques

Artifact-reduction techniques applied to intraoral xeroradiography have reduced the overall artifact level by 56.4% and the single-image retake rate from 17.4% to 11.3%. Nevertheless, the frequency of xeroradiography artifacts is greater than for intraoral film radiography, whether using manual processing (1.8% retake rate) or automatic processing (3.4% retake rate). Methods to identify and prevent xeroradiographic image artifacts are discussed in detail.

Radiographic quality control measurements comparing D-speed film, E-speed film, and xeroradiography

This study evaluated quality control (QC) measurements of D-speed film, E-speed film, and xeroradiography under clinical conditions. Automatic and manual (wet-tank) film-processing techniques were assessed. The results of QC tests (speed index, contrast index, and base + fog measurements) indicated that D-speed film and E-speed film react similarly under clinical conditions with regard to speed and contrast when processed automatically. E-speed film had an elevated base + fog measurement over D-speed film in both processing methods. Manually processed D-speed film had a greater contrast than did manually processed E-speed film. Xeroradiography maintained a consistent level of image processing under clinical conditions during this 90-day trial.

A cost analysis comparing xeroradiography to film technics for intraoral radiography

In the United States during 1978 $730 million was spent on dental radiographic services. Currently there are three alternatives for the processing of intraoral radiographs: manual wet-tanks, automatic film units, or xeroradiography. It was the intent of this study to determine which processing system is the most economical. Cost estimates were based on a usage rate of 750 patient images per month and included a calculation of the average cost per radiograph over a five-year period. Capital costs included initial processing equipment and site preparation. Operational costs included labor, supplies, utilities, darkroom rental, and breakdown costs. Clinical time trials were employed to measure examination times. Maintenance logs were employed to assess labor costs. Indirect costs of training were estimated. Results indicated that xeroradiography was the most cost effective ($0.81 per image) compared to either automatic film processing ($1.14 per image) or manual processing ($1.35 per image). Variations in projected costs indicated that if a dental practice performs primarily complete-mouth surveys, exposes less than 120 radiographs per month, and pays less than +6.50 per hour in wages, then manual (wet-tank) processing is the most economical method for producing intraoral radiographs.

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.

Biomedical image processing for age measurements of intact teeth

With increasing age the roots of teeth undergo sclerosis. The degree of dental root sclerosis can be demonstrated visually if light is transmitted through the specimen. However, this resultant image is only a two-dimensional (2-D) visualization which misrepresents what in truth is a three-dimensional (3-D) characteristic. We have described an image acquisition and computer processing system for imaging intact teeth, with special reference to the root transparency, which tends to progress from the root apex towards the neck of the teeth as a function of age. The components of our system involve: an energy source with light transmission through table-mounted dental specimens; an image processor with a digitizer; a step motor with a holder to rotate the tooth specimen; and a software package to computerize and reconstruct the sectional digital images. After rotating the position of the specimen, while at each rotation obtaining a 2-D image of the sample, we then can reconstruct the true 3-D cross-sectional or longitudinal morphology or both from these 2-D images. With this new approach, the reconstructed dental images represent segments from different angles of the tooth specimen. Picture element values in each image, quantitatively indicate the optical density, expressing the age dependent pattern of the 3-D anatomy in toto.

An evaluation of rare-earth imaging systems in panoramic radiography

Panoramic radiographs were made of ninety-nine consenting adult patients who had image-analysis test devices placed within their oral cavities. Quantitative characteristics and perceived image quality of eight screen-film combinations were investigated. The quantitative characteristics of the images evaluated included contrast, resolution (in three regions), and bead detection (a measure of noise). Perceived image quality assessed similar characteristics. In addition, expert observers rated the resultant patient radiographs for both general and specific diagnostic tasks. Calcium tungstate screen-film systems were found to have the highest contrast but with resolution comparable to rare-earth screen-film systems under clinical test conditions. Calcium tungstate systems required up to twice the radiation exposure of the patient. It was found that some rare-earth screen-film combinations may produce clinically acceptable panoramic radiographs while reducing the patient's radiation exposure.

Comparison of xeroradiographs and film for detection of periapical lesions

Xeroradiographs and Kodak Ektaspeed film were compared with Kodak Ultraspeed film for their ability to reveal periapical lesions. Cadaver specimens containing teeth which were normal or demonstrated periapical inflammatory disease were used as the test objects. These specimens were first radiographed using xeroradiographic plates or film. Following radiography, histologic analysis revealed the true presence or absence of disease. Ten oral radiologists scored all xeroradiographic and film images of the specimens for the presence of periapical disease. In general, the observers detected about 70% of the cases with periapical disease, while simultaneously considering about 10 to 15% of the normal surfaces to be abnormal. Receiver-operating-characteristic (ROC) analysis of the radiographic decisions revealed little difference in the diagnostic performance of the observers using the various image receptors, although both types of film and low-contrast xeroradiographs viewed in transmitted light were all more useful than low-contrast xeroradiographs viewed in reflected light. In terms of patient dose, both xeroradiographic images and Ektaspeed film are preferred over Ultraspeed film.

Sensitometric characteristics of dental xeroradiography

Dental xeroradiography is a high-quality intraoral imaging system which provides a potentially convenient, rapid, low-dose alternative to conventional film radiography. In this study the sensitometric properties of dental xeroradiography were investigated via assessment of high- and low-contrast xeroradiographic processor settings, transmission versus reflection densitometry, reciprocity-law failure, and kVp (tube voltage) plate dependence. Findings of the study indicated that imaging at high-contrast processor settings results in greater dynamic range but less exposure latitude than imaging at low-contrast processor settings. Determination of characteristic curves demonstrated greater contrast in reflection mode than imaging by transillumination for all but the very densest of images (greater than 1.6 O.D.). There was also little difference in characteristic curves produced from 50 to 90 kVp, indicating that the xeroradiographic plate exhibits a relatively constant sensitivity over the tube voltages tested if exposure is expressed in roentgens. Finally, no substantial reciprocity-law failure was observed for dental xeroradiography over a clinically relevant range of exposure times.

Time-delay image degradation with dental xeroradiography

Dental xeroradiography produces high-quality images of dental structures under ideal conditions. However, charged-but-not-developed xeroradiographic photoreceptor plates lose some of their charge with time, a phenomenon termed "dark decay." This investigation assesses the maximum allowable time delay between (1) charging and exposing the photoreceptor, (2) exposing and developing the photoreceptor, and (3) a combination of both delays. Measurements of resolution, background density, broad-area contrast, noise, point discharge artifacts, and diagnostic image quality indicate that photoreceptors should be processed within 5 to 10 minutes of charging in order to avoid substantial image degradation.