|Year : 2012 | Volume
| Issue : 2 | Page : 85-90
New vistas in endodontic diagnosis
Shashi Prabha Tyagi, Dakshita Joy Sinha, Radhika Verma, Udai Pratap Singh
Department of Conservative Dentistry and Endodontics, Kothiwal Dental College and Research Centre, Uttar Pradesh, India
|Date of Web Publication||6-Mar-2013|
Dakshita Joy Sinha
Department of Conservative Dentistry and Endodontics, Kothiwal Dental College and Research Centre, Moradabad, Uttar Pradesh - 244 001
Source of Support: None, Conflict of Interest: None
In the recent times no other field has shown so much growth in Endodontics as much as that of diagnosis. The human element in diagnosis is enriched by newer technologies available as adjuncts to the process of endodontic diagnosis. The trend of this development has been toward increasing objectivity sensitivity and reproducibility of the pulp tests while decreasing the patient discomfort. Methods like Pulse Oximetry, Laser Doppler Flowmetry, Ultrasound Doppler, Dual Wavelength Spectroscopy, Photoplethysmography besides the thermographic imaging and calorimetric pulp tests are being developed and evolved to suit the current clinical setting for the modern endodontist. A necessity arises here to keep abreast of all the new methods in order to be able to choose the best tools for the successful diagnostician. The aim of this review therefore was to assess the usefulness of some devices and techniques used in endodontic therapy to make the correct pulpal diagnosis.
Keywords: Endodontic diagnosis, photoplethysmography, pulp vitality, recent advances
|How to cite this article:|
Tyagi SP, Sinha DJ, Verma R, Singh UP. New vistas in endodontic diagnosis. Saudi Endod J 2012;2:85-90
| Introduction|| |
The purpose of diagnosis is to determine what problem the patient has and why does he have that problem. Ultimately, this will directly relate to what treatment, if any, will be necessary. Providing the wrong treatment for a patient could not only intensify patient's symptoms but make it even more difficult to arrive at a correct diagnosis.  In simple words, diagnosis is the process whereby the data obtained from questioning, examining and testing are combined by the dentist to identify deviation from normal. , The diagnostic aids can be wonderful allies to a judicious clinician in the process of decision making and can lead to both periapical and pulpal diagnosis. ,
What follows is a short description of the currently available recent modifications, tools and techniques to meet the challenges of the diagnostic riddles of the pulp this subsequently dictates correct treatment.
The oldest diagnostic tests were the simple percussion and palpation. In the early 1900s, the following tests were considered essential-roentgenograms (in particular, bitewings for children and adolescents), transillumination (noting the color changes between a tooth with a vital and nonvital pulp), percussion and palpation, thermal vitality tests (use of ice or hot water), electric pulp tester, mobility tests, test cavity and the anesthetic test.  Although these have served the dental clinician well over the many decades, these come with their share of limitations- putting the patient through any more pain than he already is in or invading the irreplaceable tissues, being not free from doctor and patient bias, along with the lack of correlation with the histological status of the pulp and dubious accuracy and therefore the need arose for newer methods to detect pulp vitality. 
Recently, various experimental techniques for assessing the dental pulp vitality have been reported in the literature. These include Pulse Oximetry, Laser Doppler Flowmetry (LDF), Ultrasound (US), Fiberoptics, Dual Wavelength Spectrophotometry (DWS), Thermographic Imaging, Crown Surface Temperature, Photoplethysmography (PPG), etc., Each method has been used with varying degrees of success. A short description of the development and use of these is presented.
Pulse Oximetry has recently been adapted for use in dentistry. This technique has been the most commonly used technique for the measurement of oxygen saturation in medicine because of its ease and affordability. ,,,, In 1940, Squire  recognized that changes of red and infrared light transmission caused by pneumatic tissue compression permitted saturation to be computed. In 1950, Wood  used this idea to compute absolute saturation continuously from the ratios of optical density changes with pressure in an ear oximeter. Takuo Aoyagi, an electrical engineer at Nihon Kohden company in Tokyo, realized that the pulsatile changes of oxygen saturation could be used to compute saturation from the ratio of ratios of pulse changes in the red and infrared. , His ideas, equations, and instrument were adapted, improved, and successfully marketed by Minolta about 1978, stimulating other firms to further improve and market pulse oximeters worldwide in the mid-1980s. 
This is a completely objective test, requiring no subjective response and measures the blood oxygen saturation level directly. Schnettler and Wallace  in 1991 have reported a correlation between pulp and systemic oxygen saturation readings using a modified pulse oximeter ear probe on a tooth. They recommended its use as a definitive pulp vitality tester. Kahan et al.  in 1996, designed, built and tested a reflectance tooth probe by using a Biox 3740 Oximeter, but it was not considered to have much predictive value. Gopikrishna et al. ,, developed a custom-made Pulse Oximeter sensor holder for an existing Nellcor OxiMax Dura- Y D- YS multisite oxygen sensor and showed the utility of the Pulse Oximeter dental probe on the assessment of human pulp vitality.
Pulse Oximetry uses red and infrared wavelengths in order to transilluminate a tissue and detects absorbance peaks due to pulsatile circulation and uses this information to calculate the pulse rate and oxygen saturation. The technology is based on a modification of Beer- Lambert's law: namely, the absorption of light by a solute is related to its concentration at a given wavelength. , Pulse Oximetry also uses the characteristics of hemoglobin in the red and infrared range 'oxy' hemoglobin absorbs more light in the red range than 'deoxy' hemoglobin and vice versa in the infrared range. The tooth being tested is sandwiched between a photoelectric detector and an light emitting diode of red (640-660 nm) and infrared (940 nm) lights held in a sensor holder. The devices may further be 'reflectance' type or 'transmission' type. The difference is in the type of light incident on the detector. This sensitivity test can be an ideal chair-side screening test. ,,
Laser doppler flowmetry
This is another noninvasive method of measuring pulpal blood flow. An apparatus for monitoring tissue blood flow based on the laser Doppler principle was developed in 1970s. Initially, it was used in medicine for measuring blood flow in the retina, skin, renal cortex, etc.  This method was used in dentistry to study blood flow in oral tissues. Gazelius et al.  used it first for measuring pulpal blood flow in 1986.The source of light used to measure the pulp blood flow was helium-neon (He-Ne) laser light. ,, Pettersson and Oberg  in 1991 used LDF instrument to assess the viability of pulp in intact and traumatized teeth. They used an infrared laser diode with a longer wavelength that gave better penetration than the He-Ne wavelength. Sasano et al.  designed, developed, and tested a transmitted laser-light flow meter that used high-powered laser light to monitor the pulpal blood flow of teeth rather than the conventional light flow-meter apparatus. , Konno et al. in 2007, modified the apparatus and demonstrated that a high powered (5 MW vs 2 MW) transmitted light flow meter apparatus is a better tool than the conventional back scattered light flow meter apparatus in evaluating changes in pulpal blood flow in molar intrusion (animal model). LDF has been found to be reliable and able to predict revascularization of the pulpal tissue. , Adaption of LDF in everyday dentistry is still being actively pursued.
This technique involves directing a "Laser" probe held steady by a stabilizing splint made of polyvinyl siloxane (PVS) or acrylic. ,, The PVS splinting also helps to hold the probe at an optimum angle (90°) and attenuate and reduce the 'noise' by providing a degree of isolation of a tooth from the surrounding tissue. The laser beam is directed toward the tissue being tested and reading the reflected light that is scattered back by the moving blood cells.  This reflected light is different from the incident light as it undergoes a Doppler frequency shift. This fraction of light that is scattered back from the illuminated area is detected and then processed to give a signal which is a measure of the blood flow in the dental pulp.  The total backscattered light is processed to produce an output signal which is commonly recorded as the concentration and velocity (flux) of cells using an arbitrary term "perfusion units" (PU), (2.5 volts of blood flow = 250 PU). It is thought that the predictive modeling may provide clinicians with the opportunity to identify such teeth and initiate specific treatments. ,, Adverse outcomes are seen associated with a significant decrease in values on subsequent visits as compared to normal control teeth and favorable outcomes were seen associated with significant increase in the values on subsequent visits.  It was shown that the laser can penetrate densely upto 4 mm depth and less densely for upto 13 mm length this would imply that even with good isolation, the signal contaminating nonpulpal artefactual signals aka 'noise' cannot be eliminated and therefore there is a likelihood of false results. 
Ultrasound in endodontic diagnosis
The use of ultrasound (US) in the medical field has been popular since the 1950s but its use in dentistry is fairly nascent. By using novel top of the range high frequency transducers, the device has been recently rapidly adapting itself for use in both endodontics and operative dentistry, though there had been studies carried to this end since the late 1960s. It has tremendous potential to compliment conventional radiography as an imaging technique in clinical dentistry. Due to the high resolution, three-dimensional images of the inner macrostructure of the tooth have been rendered. Cotti  reported the differential diagnosis of periapical granulomas and cystic lesions using US imaging which were confirmed by histopathology examinations of all cases. Rajendran and Sundaresan  in 2007 have determined the efficacy of US Doppler Imaging as a tool for monitoring the healing of periapical lesions treated by nonsurgical endodontics.
The device uses a transducer (a crystal containing probe), a coupling agent and software with customized electronic and digital signal processing algorithms. , US waves are generated when an alternating current (3-10 MHz) is applied to the crystal as a consequence of the piezoelectric effect. When the operator moves the probe in the examination area a change is created on the sector plane, thus producing a real-time three-dimensional image of that particular space. US has the ability to penetrate hard tissues and in principle can successfully detect discontinuities and pathosis even under existing radio-opaque restorations.  Because the different biological tissues in the body possess different mechanical and acoustic properties, the US waves at the interface between two tissues with different acoustic impedance undergo the phenomena of reflection and refraction. The echo is the part of the US wave that is reflected back from the tissue interface toward the transducer. , . The unit has been shown to successfully detect cracks in a simulated human tooth at frequencies up to 19MHz and is useful for detecting vertical root fractures in both vital and nonvital (including root canal filled) teeth. 
Ultrasound doppler or color power doppler
When applied to US examination, Color Power Doppler flowmetry allows the presence and direction of the blood flow within the tissue of interest to be observed. The intensity of the Doppler signal is represented by changes in real time on a graph (Doppler) and is also shown in the form of color spots on the gray scale image (color). Positive Doppler shifts are caused by the blood moving toward the transducer and are represented in red, whereas negative Doppler shifts are caused by blood moving in the opposite direction and are represented in blue. Power Doppler is associated with color Doppler to improve its sensitivity to low flow rates. It is based on the integrated power spectrum and can disclose the minor vessels. In a recent evaluation of the device the origin of the signals could also be differentiated with the aid of different Doppler graphic waveforms and sounds in vital teeth vs nonvital teeth. In vital teeth US Doppler reveals a 'pulsating' waveform and sound characteristic whereas root canal filled teeth shows linear nonpulsed waveform without pulsating sound.  The intravenous injection of contrast media is said to further increase the echogenicity of the area of interest. ,,
Fiberoptic fluorescent spectrometry
Employing fiberoptics and the principles of reflectance and fluorescence, marked differences in Spectral Signatures between the different dental tissues under investigation have been observed via fiberoptic fluorescent spectrometry. Excellent scope for endodontic microflora assessment also exists.  Incident ultra violet light , has the capability to induce fluorescence from some objects. Foreman  reported this phenomenon in the teeth. He reported that teeth with vital pulps fluoresced normally but the teeth with necrotic or absent pulps did not fluoresce when exposed to ultraviolet light. Differences in characteristic healthy dentin and decayed dentin fluorescence spectra at excitations of 405 nm and 440 nm were found to be statistically significant. Healthy dentin had characteristic peaks at 494 nm and 530 nm after excitation at 405 nm, whereas decayed dentin demonstrated characteristic peaks at 498, 533, 545, and 568 nm. After excitation at 440 nm, healthy and decayed dentin both showed an emission peak around 545 nm, with decayed dentin exhibiting a secondary peak around 570 nm. The differences in fluorescence spectra were attributed to the loss of mineralized tissue components and increased organic presence and water in decayed versus healthy dentin. Fluorescence from the pulp was found to be substantially lower than the healthy and decayed dentin fluorescence. The emission patterns for enamel are unique and can be differentiated from that of healthy and decayed dentin patterns providing a basis for differentiating between tissue categories.
Dual wavelength spectrophotometry
It is a class of studies in the field of dynamic light scattering related to the investigation of the dynamics of particles within very short time intervals. Diffusion wave spectroscopy was introduced by W.L. Butler in 1962 for measuring minute absorption changes of highly turbid biological materials in vivo.  It is a method independent of a pulsatile circulation. The presence of arterioles rather than arteries in the pulp and its rigid encapsulation by surrounding dentine and enamel make it difficult to detect a pulse in the pulp space. This method measures oxygenation changes in the capillary bed rather than in the supply vessels and hence does not depend on a pulsatile blood flow. Nissan et al. did an in vitro study to determine the feasibility of using DWS to identify teeth with pulp chambers that are either empty, filled with fixed pulp tissue or filled with oxygenated blood. Their findings indicated that continuous-wave spectrophotometry may be a useful method for testing pulp vitality.
Oximetry by spectrophotometer determines the level of oxygen saturation in the pulpal blood supply with a dual-wavelength light source (760 and 850 nm). This approach is applicable in the case of dense media with multiple scattering, which is very important for tissues. DWS uniquely suited for the measurements of the average size of particles and their motion within the turbid macroscopically homogeneous highly scattering media. 
This is an optical measurement technique that can be used to detect blood volume changes in the microvascular bed of tissue. The basic form of PPG technology requires only a few opto-electronic components: a light source to illuminate the tissue (e.g., skin or tooth) and a photodetector to measure the small variations in light intensity associated with changes in perfusion in the catchment (study) volume. The PPG sensing technology has been substantially improved since its origins in 1937. PPG has been compared with LDF in experiments on skin and was found to be of similar value. PPG has been applied in many different clinical settings, including clinical physiological monitoring, vascular assessment and autonomic function. ,,
It is proposed that circulatory changes in human dental pulp can also be investigated with the PPG technique. Hemoglobin absorbs certain wavelengths of light, while the remaining light passes through the tooth and is detected by a receptor. The heart rate variability is composed of low- and high-frequency fluctuations, which are mediated by the sympathetic and the parasympathetic nervous systems. The baseline and the amplitude of the PPG signal also show fluctuations in the same frequencies.  PPG assessments of dental pulp tissue viability have demonstrated pulsatile waveforms synchronous with a finger PPG reference in healthy subjects and the loss of pulsatility in patients with nonvital dental pulp.  There was a significant negative correlation between the tooth PPG signal and subject age in those with healthy teeth.
The concept of diagnosing tooth vitality by temperature measurement can provide valuable information about the integrity of the underlying pulp. Body temperature is related to the oxygen consumption of an organism. Due to differences in the blood supply and the rate of blood flow, different parts of the body show different thermal patterns.  The feasibility of temperature measurement as a diagnostic procedure in human teeth was demonstrated by Fanibunda in 1985 by a laboratory study.  He claimed that it is possible to test whether the tooth was vital by means of Crown Surface Temperature. In 1986, these results were published by him in a clinical study, using the Time-Temperature Relationship method. 
Cholesteric liquid crystals
Cholesteric crystals are a type of 'liquid' crystal, i.e. ordered fluids, with a helical structure ordered along the long axis known as chiral- nematic liquid crystals. Due to their fluidity these are easily influenced by temperature or pressure. The pitch of the very structure of the crystal varies when the pressure or temperature are altered thus changing their color heated i.e. they are thermochromic. These were used in a study by Howell et al.  in Lexington 1970. They found that nonvital teeth have lower temperature than vital teeth They experimented various liquid crystals until they arrived at a combination that would indicate temperatures in 30° to 40°C range. They used cholesteric compounds that were in a 10% solution in a chlorinated hydrocarbon solvent. When applied to the tooth surface, the crystals went through color changes that were compared with adjacent or contralateral-teeth. Their usage in detecting pulp vitality is based on the principle that the teeth in intact pulp blood supply have a higher tooth-surface temperature compared with teeth that had no blood supply.
Here a color image is produced which indicates a relative difference in temperature in both superficial and deep areas. Computer-controlled infrared thermographic imaging is another noninvasive method of recording the surface temperature of the body. , It is highly sensitive and has been used extensively in nonmedical military applications. The use of Huges Probeye 4300 Thermal Video System (Hughes Aircraft Co., Carlsbad, CA) was reported in 1989 by Pogrel et al. and was found to be sensitive enough to measure temperature differences as low as 0.1°C. Newer, less cumbersome, and easier to use models is now available.
Some other experimental techniques have also been considered for endodontic diagnostics. Work on developing Optical Reflection Vitalometry started in late 1990s and a preliminary report was published in 1997 by Oikarinen et al.  This method is another noninvasive method to detect pulp vitality. One can 'see' the pulse of the pulp or the oral mucosa. This device, too, is yet to be clinically accepted and commercially available.
| Conclusions|| |
Diagnosis forms the basis of treatment. The vistas of endodontic diagnosis are ever evolving. Careful attention to diagnostic aids and an understanding of both their usefulness and limitations is essential if they are to be employed most effectively in clinical dentistry.
Equipping ones natural diagnostic instinct with knowledge of contemporary advances would ensure that a clinician chooses the best possible diagnostic tools for his toolkit to help him and his patient along a safer and surer path of endodontic treatment.
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