caries detection

NTRODUCTION
Modern restorative dentistry (MRD) relies on the protocol that all sound tooth structure should be saved during tooth preparation, and modern adhesive protocols should be utilized to restore form and function.1 Dentists have used many different tools to ascertain the presence of dental caries versus healthy/uninfected tooth structure including radiographs, tactile feel with explorers and excavators, and caries dye indicators. Defining new diagnostic and treatment strategies and related instrumentation that assists to identify carious lesions is consistent with the principles of MRD.
Dentists are adopting a more minimally invasive approach to restorative care, and as a result, patients are able to keep more of their tooth structure.2 Preservation of enamel vastly improves the seal of our adhesive restorations, and the preservation of dentin is critical to maintaining tooth strength.3 Therefore, the use of technology that allows clinicians to detect caries earlier will improve the lifespan of their patients’ dentition.
Processes focused on diagnosing early lesions with optimum sensitivity have employed laser, fluorescence, autoflorescence, image processing under magnification, and even electric current.4 Though these devices are readily available, their high cost and excessive variable sensitivity have prohibited their use on a daily basis.

LED TECHNOLOGY FOR CARIES DIAGNOSIS INTRODUCED
Now, there is a promising technology that offers the ability to detect tooth decay at different stages of its development with an accuracy that may often be missed by x-rays. The technology is based on the principle of fluorescence, where a specific wavelength of light shines on the tooth and is then reflected back in 2 basic colors: green when the dentin is healthy, and red when the dentin is infected. A device that combines high magnification intraoral imaging with fluorescence becomes a powerful time-saving tool for diagnosing and proposing treatment. The same device can then guide the clinician through the treatment of caries removal. This process has been named light-induced fluorescence evaluation for diagnosis and treatment (LIFEDT).
The SOPROLIFE Camera (ACTEON North America) is a new intraoral LED camera working as 2 devices in one; operating as an intraoral camera as well as a caries detection device. Patients who are routinely seen in hygiene and exam areas with the question in their mind, “Will my dentist find something today?” will find the diagnosis of early caries of asymptomatic teeth much easier to process. A moment of truth or trust issue at the time of this diagnosis can be much easier with this unique intraoral camera showing the patient through magnification the carious grooves and suspicious shadows of interproximal decay. An explanation of the fluorescence concept and reference colors facilitates a co-diagnostic experience.
For the dentist, use of the fluorescence mode becomes a treatment aid to differentiate diseased versus healthy tissue. Another benefit to using the SOPROLIFE camera is that a history of carious lesions can be documented, and changes in their development can guide treatment decisions. Instead of informing patients that you will “watch” this tooth, a pictorial reference is easily made into the patient record.

SCIENCE OF FLUORESCENCE AND AUTOFLUORESCENCE
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. Dental tissues have fluorescent molecules (fluorophores or fluorchromes) which absorb light, then emit the energy back as fluorescent light—this is called autofluorescence. This process was described by Banerjee, et al5 in 2000. It became the basis for a new method of diagnosing initial caries. Scientists and clinical researchers at SOPRO, a company specializing in dental imaging, found that a blue LED emitting light at 450 nm was able optimize the autofluorescence of the dental structures. The fluorescence signal reflected was extremely low intensity compared to the 450 nm intensity sent by the blue LEDs. By amplifying the fluorescent signal, a new level of tissue distinction could be made.
Healthy dentin could be clearly discriminated from carious dentin as it fluoresced a bright green signal. The wavelength of the autofluorescence signal varies according to the density and chemical composition of the surface tissue and subsurface. The determination was made that that one of either the inorganic or organic constituents of healthy dentin that emits the acid-green fluorescence partially disappeared during the caries process; subsequently, a red fluorescence signal would appear. The autofluorescence technology allowed detection of early occlusal, even interproximal, decay.
(The process evolved into the patented technology used to develop the SOPROLIFE Camera.)

LED CAMERA OPERATION AND SUGGESTED USE
The camera has a magnification range of more than 50x. Using this magnification reveals anatomy far more precisely then visual and hand probing.6 The use of conventional probing has also been considered controversial based on the possibility of “inoculating” or transferring lesion contents.
The camera has 3 modes: the daylight mode, the diagnostic mode, and the treatment mode. The daylight mode has 4 settings which allow clear images for portraits, smiles, intraoral and macro views.
The diagnostic mode, labeled mode I on the images, filters out colors of the surrounding soft tissues of the mouth, rendering them black and white. It amplifies and displays in color the fluorescence signal response sent by the dentin. A healthy tooth appears white with a homogeneous green hue on top of it. The diagnostic mode is focused more on enamel. Differences in thickness of enamel as well as material deposits will affect the fluorescence response. Thicker enamel reduces the fluorescence response and gives a slightly blue image. Demineralized enamel gives a white, color-free response. Since demineralization is the first stage of the caries destruction, noting white colors can be very important.
Significant amount of material deposits tend to give a black signal, which is considered an alert to clean the deposits and reassess the signal. Infected dentin gives a dark red autofluorescence signal. Incipient and evolving lesions magnified in the diagnostic mode tend to have mixed signal colors of red centers surrounded by black grooves and green islands. This is because material deposits shown as black can minimize the red signal of dentin caries.
The treatment mode, labeled mode II on the images, also filters out the surrounding soft tissues of the mouth, rendering them black and white. This mode also amplifies and displays in color the fluorescence signal of the dentin. The only difference in the treatment mode is that the red wavelengths are amplified more and the blue wavelengths are decreased. Carious dentin gives a red fluorescence signal so the amplified red color in the treatment modes assists in the excavation process—a photographic caries detector of sorts.