Introduction:
Diagnosis is an important tool for disease identification. Proper diagnostic tests are necessary for determining ideal treatment options. Visual inspections are one of the main diagnostic procedures performed in dentistry. But visual inspections along with magnifications and transillumination can be an added benefit in identifying disease conditions.
What Is Transillumination Technique in Dentistry?
Transillumination test of teeth is a recent advancement in modern-day diagnostic dentistry. This provides the most accurate information regarding the various lesion of the tooth. Also, a visual representation of the tooth, whether a crack is present in the enamel or dentin part of the tooth structure, can be identified. The transillumination technique is based on a law of physics that states when a light beam penetrates through a substance, it continues until it encounters a specific space, after which the light beam is reflected. This principle results in the formation of a light and dark area in the tooth structure separated by a fracture line or cracks. Sources of light other than those that arise from the transilluminator should not be present ideally or used by the dental operator. Light arising from overhead lighting, dental chair, and operatory lighting can not be used as it can result in distorted results. Previously, a dental mirror was used by the surgeon to evaluate whether a fracture is present or not. Modern-day dental (surgical) or operating microscope is specifically useful in situations when the light source is turned off. Various transilluminators are now commercially available over the last decade. Many dentists prefer using the fiberoptic handpieces available for composite curing.
How to Perform a Transillumination Test?
The detection of a cracked tooth is difficult clinically and often requires CBCT (cone beam computed tomography) scanning. The Normal diagnostic tests which may otherwise prove useful in most dental diagnostic situations, such as sensitivity testing or radiographic evaluation, may still prove evasive or elusive in detecting cracks within the tooth structure or junction of the tooth crown or root. Fiber-optic transillumination (FOTI) is the most commonly used technique for this purpose. Methylene blue dye can be used along with the transilluminator machine for highlighting the cracks. Usually, a quartz halogen lamp and rheostat are used in the transilluminator device. The diameter of the probe is 0.2 inches. The light generated by such sources has an intensity of 4000 lux.
The cracked teeth have the potential to harbor bacterial byproducts. As a result of bacterial accumulation, these harmful pathogens may or may not completely extend to the pulp of the tooth or the root canal that preserves the vitality and vascularity of the tooth structure. The pulpal diagnosis for a tooth with a crack could be either normal, reversible pulpitis (pulpal damage that can be reversed), irreversible pulpitis (irreversible damage of the pulp), or pulpal necrosis. This diagnosis should be always accurately done by the surgeon as it can be very confusing from the clinical analysis or clinical perspective alone. Needless to say, such a diagnosis can not be made by a transillumination test. But, owing to the benefit of the transillumination technique, the dentist also may eliminate the need for recommending a test based on ionizing radiation. As a result, procedures like CBCT and intra-oral peri apical radiographs can be eliminated.
What Are the Indications of Translumination Tests?
Transillumination of teeth is a diagnostic technique used to detect the presence of cracks. Ideally, this technique should be performed in various situations, which include:
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Cracks on Marginal Ridge and Buccal Surface: These cracks may be found on the marginal ridge of the tooth or on the buccal surface of the anterior teeth. Such cracks are often referred to as "craze lines."
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Cracks in Cavity Preparation Floor: This technique can detect cracks present on the floor of cavity preparations.
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Visualization of Pulpal Floor after Endodontic Access Preparation: This method is beneficial for visualizing the pulpal floor following endodontic cavity access preparation of the tooth. It aids in identifying minor perforations on the pulpal floor.
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Detection of Proximal Caries: It is useful for identifying proximal caries located on tooth surfaces that are not easily accessible.
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Restoration Removal for Visualizing Vital Tooth Structure: After removing restorations, this technique helps in visualizing the remaining vital tooth structure and assists in detecting carious lesions.
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Detection of Fractured Lines on Cusp Tips: Transillumination can also detect fractured lines present on the cusp tips.
For proper diagnosis visualizing the teeth under magnification during the translumination test is ideal. Usually, 16 times magnification is preferred in such situations. Dental hygienists can refer patients to the dentist if they detect tooth cracks during the transillumination procedure. Though, it is difficult to diagnose the extent and the form of the crack through the translumination technique.
What Are the Drawbacks and Scopes of the Translumination Technique?
The true benefit of transillumination lies mainly in determining potential vertical tooth fractures. In conditions like cracked teeth, the tooth or the segment remains immobile whereas the fracture line extends from the enamel surface to the apical portion. Also, the transillumination test is a popular diagnostic modality for caries detection and crack or fracture detection. Multiple studies have also revealed that the use of near-infrared transillumination is excellent in terms of detecting dental caries lesions on proximal surfaces of the tooth and even below retained or older amalgam restorations (where the probability of secondary caries is more). Such areas are often difficult to evaluate properly with the naked eye and with hand instruments. Factors like the presence of gum, calculus, and posterior inaccessible areas are responsible for such difficulties. Even modern diagnostic radiographic techniques using RVG (radiovisiography) may provide inaccurate results due to a phenomenon known as cervical burnt out. Even the accuracy of bitewing radiograph in such cases is only 65 percent.
The vital tooth in this technique easily allows the passage of light whereas, a nonvital or dead tooth appears opaque in comparison to the contralateral vital teeth in the oral cavity. Compared as an adjuvant to the conventional pulp vitality testing procedures, the only drawback of the transillumination procedure is the frequency of potential errors in diagnosis that would occur in the most critical tooth category of nonvital teeth. Even the advanced fiber-optic transillumination, though it can reveal tooth discoloration is not a completely accurate way to determine the pulp vitality of the tooth. Also, one more disadvantage of this technique is that if there is an intrinsically discolored tooth, then the light will not pass through the tooth regardless of whether it may be ambient or focused light.
Conclusion
Transillumination as a diagnostic procedure is highly beneficial for dental operators. It is useful in detecting various pathologies such as proximal caries, crack lines, and fracture lines in the tooth structure. But such procedures may not be accurate for assessing pulp vitality. Also, such a procedure may provide inaccurate results if done on the nonvital tooth.
