Interproximal Demineralization: Automated Detection and Analysis

by George Freedman, DDS, FAACD, FACD, FADFE

Oral radiography, in use for over a century, is well-established in the dental profession. A curiosity at first, it quickly carved out an important role in dental caries detection. Today, dental radiography is a standard part of the dental examination, identifying and locating sites of dental disease that are inaccessible to other diagnostic methods.

Digital radiography reduces exposure to radiation for the patient and the dental team by up to 80% or more, and creates images that the practitioner manipulates with a touch of a button to take advantage of a variety of diagnostic technologies (Table 1). Patient radiographs are integrated seamlessly with management software. Dental digital radiography provides greatly enhanced diagnostic visualization, easier communication of detailed clinical data to specialists, colleagues, and insurance companies, as well as the security of off-site data backup and multiple location storage. The current accuracy of digital radiography enables very early diagnosis, encouraging conservative treatment by caries reversal rather than surgical amputation.

Digital radiography systems such as the RVG 6100 System (Carestream Dental, Atlanta, GA) (Fig. 1) utilize high-resolution CMOS-sensors coupled with high-sensitivity CSI scintillators and dedicated electronics to capture and interpret radiographic data from x-ray sources that have passed through dental tissues (Fig. 2). Their image resolution is greater than 20 line pairs per millimeter, very similar to traditional analog film, offering the practitioner an excellent opportunity for comprehensive and early diagnosis. Digital magnification and/or image enhancement provide innovative tools that extend the professionals ability to analyze intraoral conditions, and thereby provide more effective, more efficient, and more confident treatment.

Dentists are always looking for techniques and technologies that can extend their clinical skills for the patient’s benefit; in this case, their ability to differentiate between the very similar, virtually undetectable variations of shades of gray that comprise a radiograph. It is also far more efficient, considering the cost of chairside time, to analyze all the at-risk interproximal areas visible on radiograph at once rather than individually. Suspicious areas can then be inspected with further diagnostic procedures, and frank lesions scheduled for restoration. The latest version of Logicon Caries Detector Software (5.0), developed by Dr. David Gakenheimer (Fig. 3) for the dental profession, analyzes the many shades of gray that are too similar for the human eye to differentiate, identifies those image features at the proximal areas that may be indicative of caries, and then correlates this information with a human caries database.1 The software then highlights the questionable and likely areas of dental disease on the screen, alerting the practitioner to examine these in greater detail. For the dental team member, this entire extended diagnostic activity requires one single click. Clinical studies have confirmed that Logicon is 20% more effective than visual analysis in identifying dentin-penetrating caries, and demonstrates a positive dentinal caries detection rate of 90%.2 The Software is effective in locating proximal caries, classifying it, and indicating the depth of penetration into the enamel or dentin. Logicon’s image analysis quantifies the gray gradient, and successfully estimates the probability of proximal caries in any particular location in the enamel and/or dentin.

Once the patient’s digital radiograph has been taken, interpreted and presented on the monitor (Fig. 4), Logicon Software’s internal process for caries detection (Fig. 5) goes through the following steps:

1. The software analyzes the image to identify all the distinct teeth that are present in the image.

2. The center of each tooth is determined (yellow square with + in the middle) (Fig. 6).

3. For each tooth, the software identifies the dentin-enamel junction (DEJ).

4. The tooth edges, both mesial and distal, are recognized.

5. Logicon Software watermarks 15 concentric contour lines over each proximal surface, inwards from the tooth edge. There are 10 separate green contour lines in the enamel, from the tooth edge to the DEJ, and five separate blue contour lines from the DEJ towards the pulp (not all displayed).

6. The V tool is anchored approximately at the center of the tooth, and the arms of the V are extended to the tooth edge.

7. Logicon Software performs a density scan inside the V tool arms by analyzing the gray shade variations.

8. The collected data is presented on screen as an outline overlay on the digital radiographic image and in two pictorial analysis and decision-making charts. The radiograph overlay specifically locates the areas of reduced density at the proximal surfaces of the teeth and classifies them in terms of severity and depth. One chart indicates the change in tooth density from the surface through the DEJ and into the dentin, layer by layer, for 15 layers as described above. The other chart evaluates the probability of decay in the enamel and dentin separately. The yellow threshold line is the marker that recommends restoration.

9. This information is stored permanently in the patient’s electronic chart, ready for transmission, consultation, re-evaluation and comparative analysis. The Logicon Software data clearly documents the practitioner’s rationale for proceeding with any necessary restorative treatment. It is also useful for patient education to demonstrate the need for restorations, reaffirm successful home care, and to increase the patient’s involvement in their own oral health.

10. The proof of the Logicon Software is the dental caries that is revealed through operative dentistry. In this case (Fig. 7), the lesions found on tooth number 15 (mesial, distal) and tooth number 14 (distal) correlate with the diagnostic data seen in Figure 5. They confirm the accuracy of the automatic caries detector, and verify the penetration depths seen on the radiograph.

Prior to the automated version of Logicon Software (5.0), the dentist performed all these steps manually, as a separate task for each individual interproximal site. Now, the simple click of a button activates all the caries detection processes for every single interproximal surface in the bitewing radiograph.

It is important to remember that Logicon Software’s PreScan feature is not designed as a final diagnostic assessment; the practitioner must further investigate the identified areas to verify the presence of caries or to eliminate that possibility of disease. It is essential that Logicon Software’s PreScan feature be utilized as one of the tools for identifying interproximal caries. The data obtained from Logicon Software should be correlated with visual confirmation of the radiograph, and visual and tactile examinations of the tooth in question. Further parameters that should be considered include the patient’s dietary habits, oral hygiene, age, and caries activity status.

In those situations where the PreScan data from Logicon Software and the supporting examinations do not correlate, the Region of Interest (ROI) tool may provide a more accurate result. In all cases, however, the clinical judgment of the dental practitioner is paramount.

The digital radiography evolution has been benefiting patients and dentists for a quarter of a century. Logicon Software’s PreScan feature is an innovative pattern recognition software that has been developed specifically for the dental profession. It increases the efficiency of the dental diagnostic procedure, focusing the dentist’s attention to at-risk areas, and identifying early lesions well before human eyesight can make the distinction. OH

Dr. George Freedman is a founder and past president of the AACD, a co-founder of the CAED and a Diplomate of the American Board of Aesthetic Den
tistry. Dr. Freedman sits on the Oral Health Editorial Board (Dental Materials and Technology) is a Team Member of REALITY and lectures internationally on dental esthetics and dental technology. Dr Freedman was recently awarded the Irwin Smigel Prize in Aesthetic Dentistry presented by NYU College of Dentistry. His most recent textbook, “Contemporary Esthetic Dentistry” is published by Elsevier. Dr. Freedman maintains a private practice limited to Esthetic Dentistry in Markham, ON, Canada.

Oral Health welcomes this original article.