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.

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.

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.

Thermographic assessment of neuropathic facial pain.

Ongoing pain, intermittent sharp pain, or intermittent dull aching pain around the teeth can evoke the suspicion of tooth pathology. However, when no dental cause can be found clinically or radiographically, the differential diagnosis involving neuropathic pain and pulpal pathology is still a challenge. Neuropathic facial pains are still too often misdiagnosed as tooth pain of dental origin, resulting in unnecessary dental extraction or endodontic therapy. The purpose of this study was to determine if electronic thermography was able to differentiate neuropathic facial pains presenting as toothache from pulpal pathology. Electronic thermography was used to compare asymptomatic subjects and subjects with neuropathic facial pains. Asymptomatic subjects and subjects with trigeminal neuralgia, pre-trigeminal neuralgia, and pulpal pain without periapical pathology showed no thermographic difference in the territory of the pain complaint when compared to the opposite nonpainful side. Patients with sympathetically maintained traumatic trigeminal neuralgia (atypical odontalgia) and half of the group with sympathetically independent traumatic trigeminal neuralgia presented with "hot" thermograms. The other half of the patients with sympathetically independent traumatic trigeminal neuralgia displayed "cold" thermograms in the area of their pain complaints. Electronic thermography was the least selective test for the group showing "cold" thermogram patterns (80% agreement with the thermographic characterization criteria). These data suggest that electronic thermography may be helpful in differentiating neuropathic pains from pulpal pathology.

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 craniomandibular disorders: diagnostic interpretation versus temperature measurement analysis.

This study assessed electronic thermography as a diagnostic alternative for evaluation of temporomandibular disorders. The study populations consisted of 50 temporomandibular joint patients having internal derangement or osteoarthrosis and 30 normal temporomandibular joint subjects. An Agema 870 thermovision unit was used for analysis. Diagnostic evaluations by expert interpreters were made using standard procedures. Thermography measurements included mean absolute temperature measurements and right-left temperature differences for five anatomic zones and four spot areas. Statistical analysis of data included both linear discriminant analysis and classification-tree analysis. Results indicated that when differentiating between "abnormal" and "normal" temporomandibular joints using classification-tree analysis, correct classifications were made in 89% of the cases and observer diagnostic accuracy was 84%. When evaluating for specific diagnoses (eg, osteoarthrosis, internal derangement, or normal temporomandibular joint), correct classifications using classification-tree analysis were made in 73% of the cases and observer evaluation was correct in 59%. The three best temperature measures found were: (1) delta T of the zone immediately overlying the temporomandibular joint; (2) the zone temperature of the half-face; and (3) the spot temperature anterior to the external auditory meatus. Additional studies are needed before thermographic diagnosis of craniomandibular disorders is accepted clinically.

Thermography for the clinical assessment of inferior alveolar nerve deficit: a pilot study.

Neurosensory deficit is a major complication encountered in maxillofacial surgery. This study assessed the ability of electronic thermography to identify inferior alveolar nerve deficits in a pilot clinical study. The study population comprised six patients with inferior alveolar nerve deficit and 12 normal subjects. Frontally projected facial thermograms were taken on 18 subjects and measured using an Agema 870 unit and thermal image computer. Mathematical analysis of thermal measurements included temperature and delta T calculations of the anatomic zone over the mental region of the face. Results included (1) high levels of thermal symmetry of the chin in normal subjects (delta T = 0.1 degree C, standard deviation = 0.1 degree C); (2) low levels of thermal symmetry in patients with inferior alveolar nerve deficits (delta T = +0.5 degree C, standard deviation = 0.2 degree C); (3) statistically significant differences in delta T values (t = 4.82, P > .001) in patients with inferior alveolar nerve deficit; and (4) absolute temperature variations of the mental region in both groups. This pilot study demonstrated thermal asymmetry in patients with inferior alveolar nerve deficit and suggests that electronic thermography has promise as a simple, objective, noninvasive method for evaluating nerve deficits. However, more extensive studies are needed before thermographic procedures are accepted clinically.

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.

Traumatic dysesthesia of the trigeminal nerve.

Traumatic injury to the peripheral nerves often results in persistent discomfort. Substance P has been implicated as a mediator of pain, and depletion of this neurotransmitter has been shown to reduce pain. Subjects suffering from traumatic dysesthesia of the trigeminal nerve were treated with capsaicin, a substance P depleter with significant long-term effects. This form of therapy may be used individually or in combination with other pharmacologic interventions in the treatment of traumatic trigeminal dysesthesia.

Thermographic characterization of internal derangement of the temporomandibular joint.

This study assessed the ability of electronic thermography to identify internal derangement of the temporomandibular joint. The study population consisted of 30 patients with internal derangement verified by temporomandibular joint arthrotomography. Electronic thermography was conducted using an Agema 870 thermographic unit. Thermal assessments included: (1) pattern recognition; (2) pattern symmetry; (3) absolute temperature measurements; (4) delta T measurements; and (5) mean temperature measurements and differences within five designated anatomic zones. Results indicated: (1) low levels of thermal symmetry in patients with internal derangement of the temporomandibular joint, and (2) absolute temperature measurements and mean temperature zone measurements showing large delta T values (0.4 degrees C to 0.8 degrees C). Demonstration of characteristic thermal temporomandibular joint changes suggests that electronic thermography may have potential for assessing internal derangement of the temporomandibular joint. However, more extensive studies are needed before thermographic procedures can be accepted clinically.

Thermographic characterization of osteoarthrosis of the temporomandibular joint.

This study assessed the use of electronic thermography in the thermal image characterization of 20 patients with osteoarthrosis of the temporomandibular joint as proven by radiographic detection of bone erosions. Thermal assessments included: pattern recognition, pattern symmetry, absolute temperature, delta T measurements, and mean temperature measurements and differences within five designated anatomic zones. In patients with osteoarthrosis of the temporomandibular joint, results demonstrated some characteristically abnormal thermal patterns; low levels of thermal symmetry; and substantially elevated absolute temperature measurements, mean temperature zone measurements, and delta T values. These observations suggest that electronic thermography may prove to be clinically useful as a diagnostic method of assessing temporomandibular joint disorders, particularly osteoarthrosis. However, more extensive studies are needed before thermographic evaluation of the temporomandibular joint will be accepted clinically.