Diagnostic Ability of Near Infrared Transillumination Detecting Interproximal Caries as Compared to Conventional Bitewing Radiographs

Dental caries is a common disease[1] affecting 621 million children in 2010[2]. Dental caries in children commonly result in dental pain, infection and missed school days [3]. The financial burden of childhood caries is also significant[3] due to involved time during care, transportation and missed work for appointments. Caries development and progression is a multifactorial process which is a preventable by controlling various contributing factors including good oral hygiene practices and healthy diet. Also, with early intervention by a dentist, small caries can be diagnosed early and treated conservatively with reduced financial burden to the patient and their family[4].

Carious lesions are initiated when bacterial biofilm organize onto the tooth surface and produce acid byproducts after metabolism of carbohydrates. This acid causes the degradation of the outer enamel shell of the tooth, eventually progressing into a cavitated lesion. If left untreated, carious lesion can reach the enamel-dentin junction and can spread to increase the lesion size. Thereafter, the carious lesion progress through the dentin and eventually to the dental pulp, causing inflammation and eventual necrosis of the pulp. Caries process can initiate on the occlusal (biting), smooth (buccal or lingual), or interproximal (in between the teeth) surfaces of the tooth. Interproximal surfaces of the teeth are in contact and hence, cannot be visualized clinically during routine dental examinations. Interproximal carious lesions become clinically detectable only when they are advanced with significant to loss of tooth structure[5]. When the interproximal lesions are detected clinically or by radiographs restorative management is warranted. Restorative management of the carious lesions by using various resin-composite materials is an esthetic choice which is often opted by the patient and family. However, secondary caries around the restoration is one of the leading causes of restoration failure[6]. Additionally, in the US, majority of the restorations placed each year are done to replace existing restorations[6]. Large carious lesions with pulpal symptoms may need pulp treatment or dental extractions to remove the source of infection.

In young children (primary or mixed-dentition stages) the contacts between teeth (interproximal) are wider and thicker[7]. Additionally, the outer enamel layer is thin and hence, carious lesions can progress quickly into dentin and eventually into the pulp. Traditionally, screening for interproximal caries in primary and mixed-dentition stages is achieved during routine dental examination by taking BWX. During BWX, a beam of X-ray passes from the cheek side of the tooth through the interproximal contacts and captured on to a film or sensor on the lingual (tongue) side of the tooth. This creates an image representing radiodense and radiolucent areas of the tooth. Radiodense areas have higher mineral content, and radiolucent areas have lower mineral content[5]. When looking at the outer enamel and middle dentin layers of the tooth, radiolucent areas indicate significant demineralization referred to as carious lesions. BWX allow for the evaluation of the interproximal surfaces for any carious lesions, which often cannot be visualized clinically due to closed contacts between the teeth[8, 9]. BWX are successful at detecting initial and well established carious lesions, but have some limitations in ability to detect small incipient (very early) lesions that have not caused enough demineralization to appear radiolucent on imaging [10, 11]. One of the major disadvantage of BWX is the exposure to small doses of radiation, which must be considered when determining the frequency of radiographs[12]. Some parents may have concerns to radiation and may decline intraoral radiographs. This may limit the clinician's ability to determine interproximal carious lesions[3]. Currently, the American Dental Association (ADA) recommends that BWX should be taken at every 6 to 18 months interval depending on caries-risk status of the patient in conformity with the ALARA (as low as reasonably achievable) principle for diagnostic purposes[13]. Despite the radiation concerns from parents, BWX have been a clinical standard of care.

BWX are indicated for children when their posterior molars are in contacts, and the interproximal surfaces could not be viewed clinically during routine dental exam[13]. Anatomically smaller size of the oral cavity and limited behavioral coping skills in children are important considerations while planning BWX. While obtaining BWX, children may have problems such as difficulty biting down on radiographic film holder, minor discomfort from the film touching the floor and roof of their mouth and staying still during exposure. If a child is not able to tolerate the radiographic techniques then radiographs can be undiagnostic[8] in spite of the small radiation exposure[14]. When longer intervals between radiographs are planned due to radiation concerns, caries can go unchecked with findings such as multiple carious lesions in advanced stages at subsequent dental visits. Multiple carious lesions in young children are managed with restorative treatments done under general anesthesia[2] which poses a significant medical risk to the young patients and a significant financial healthcare impact[15]. Hence, preventive and conservative management of caries has been the standard of pediatric dental care. Medical management of caries which includes early caries diagnosis for modifying the caries-initiating factors for a conservative approach has been advocated[16]. Early detection of carious lesions can be managed conservative treatment options such as frequent fluoride varnish applications and changes in oral hygiene and diet[8, 11].

Near Infrared transillumination (NIRT) is a method of caries detection that uses light (instead of X-rays) and a camera to capture information about the density of enamel and dentin at the interproximal contacts thereby eliminating risks of radiation[9]. Specifically, CariVu™ (Dexis) by Kavo, was developed in 2012 in Germany utilizing NIRT at 780nm and capturing the occlusal surface of the transilluminated tooth on a digital image[17]. The device comprises of elastic arms containing the optical fibers and a camera system with the near infrared light source, ranging from 700-1500nm wavelength. The arms approximate the alveolar process of the tooth, allowing transillumination of the crown of the tooth. The arms, unlike BWX films, does not contact the floor or roof of the mouth and therefore, can increase the acceptance by pediatric patients. Demineralized or porous areas of the tooth (indicative of carious lesions) can cause a change in light scatter and appear darker in the image captured by the camera[1, 5]. The CariVu™ (Dexis) image can be evaluated for interproximal caries in a similar manner as BWX for diagnosis and treatment planning.

Previous studies detected superiority of CariVu™ (Dexis) to detect incipient and small carious lesions in permanent dentition [4, 17, 18]. Earlier studies recommended utilizing CariVu™ (Dexis) as an adjunctive technology to BWX when diagnosing caries[1]. Recent studies claimed that CariVu™ (Dexis) could be utilized as a comparable alternative to BWX[9, 11, 17], with benefit of eliminating radiation. CariVu™ (Dexis) can be utilized to detect caries with frequent interproximal imaging[4], for early detection of incipient carious lesions [4, 9, 14, 17]. CariVu™ (Dexis) has been recommended as a safe alternative to ionizing radiation for children[17]. However, due to the anatomical differences in the contacts and interproximal lesions in permanent dentition as compared to primary dentition, it will not be wise to extrapolate inferences from these studies on permanent dentition to primary dentition. There are no studies evaluating the efficacy of CariVu™ (Dexis) in diagnosing interproximal carious lesions in children. Majority of the studies have established the safety of this NIRT technology and hence, utilization of such technology has tremendous potential in pediatric population over BWX due to growing concerns regarding radiation. Additionally, there are no studies evaluating the acceptability of NIRT in children over BWX. As previously discussed, ability to cooperate is an important factor for generating a diagnostic image for caries detection in children. If CariVu™ (Dexis) is tolerated more than BWX in children then, in addition to being safe it can be an effective and efficient tool in pediatric dental practice for diagnostic images to detect carious lesions.

This is a pilot study to determine the efficacy of CariVu™ (Dexis) in diagnosing interproximal carious lesions in children as compared to BWX (standard of care). This study will also evaluate the acceptability of CariVu imaging as compared to BWX in children. The overall chair-side time required for obtaining CariVu images will determine its clinical acceptability. The long-term goal of this study will be to investigate the newer NIRT technology for incorporation in pediatric dental practice as a diagnostic tool for effective reduction of radiation in children with efficient diagnosis of interproximal carious lesions in children with high caries-risk status.