The Challenge: Developing a system with a fast, reliable, easy-to-use interface for use with an intraoral camera to continuously acquire frequency-domain photothermal radiometry (PTR) and modulated luminescence (LUM) responses from two detectors in less than five seconds while modulating a laser that illuminates the tooth surface.
The Solution: Replacing two bulky and expensive hardware lock-in amplifiers with a single cost-effective OEM data acquisition module from National Instruments and NI LabVIEW software installed on a netbook to miniaturize the system further.
Tooth decay is one of the most prevalent diseases worldwide and one of the most common chronic childhood diseases. Traditional treatment has been to wait until the lesions have
enlarged to consume all of the enamel shell and then place a dental filling in the tooth. If detected earlier, decay in these small areas may be halted and reversed with the application of fluoride and other preventive therapies. Early detection and treatment may prevent painful dental appointments, preserve teeth, and save money.
Using frequency-domain PTR and modulated LUM diagnostics at Quantum Dental Technologies (QDT) we developed and tested a portable PTR-LUM instrument called the Canary System, which uses a low-power laser to examine the tooth surface. When laser light is shone on a tooth, the tooth glows (luminescence) and releases heat (the photothermal effect).
A majority of new dental technologies on the market examine only the glow when light is shone on a tooth. However, our instrument has two unique features: 1) the laser light is pulsed, which allows us to examine below the tooth surface, and 2) both the released heat and luminescence are detected, which provides an accurate measure of the decay. The temperature rise in the tooth is less than 1° C, which is imperceptible to the patient. As tooth decay worsens, the heat and light signals change. As the decay remineralizes, the signal reverses.
The Canary System can detect and monitor areas of decay as small as 50 µ on smooth enamel or root surfaces, the biting surfaces of teeth, and between teeth. It can also detect erosive lesions caused by exposure to acidic liquids and decay around the margins of dental fillings. The Canary System is portable, has a footprint not much larger then a netbook, and has Internet access so dentists can upload data to a Web-based server.
LabVIEW software with an NI OEM data acquisition (DAQ) module fully controls the PTR-LUM signal acquisition in the Canary System. A USB intraoral camera captures images, and real-time video images are captured in a LabVIEW GUI. We use text-to-voice functionality to interact with the operator for better operation performance in a real-life clinical situation.
Classified as a Class II medical device, QDT engaged in investigational testing for the Canary System (Figure 1). For our clinical studies, we use the analog output channel of the DAQ module to generate a sinusoidal signal to modulate a low-power laser beam. We shine the laser beam on a tooth surface and quickly measure PTR and LUM responses from the corresponding detectors through analog input channels of the DAQ module.
Mechanical shutters control precise exposure time of the laser light shone on human tooth surfaces through a digital output channel of the DAQ module while user inputs during measurements are communicated through a digital input channel of the DAQ module. Images of the scanning tooth surfaces are captured in a LabVIEW environment through DirectShow drivers. The DAQ module controls the functionality of the camera and LED power supply. All information related to the trial subjects and operators are input into the LabVIEW GUI according to good clinical practice (GCP). Complex functionality of the operation in the clinical trial is simplified with real-time voice feedback to the operator.
After acquiring the response signals from the analog input channels, we use software lock-in amplifier algorithms to compute the amplitude and phase of the PTR and LUM signals. Data is analyzed and a Canary number is created as an indicator for early dental caries detection. Furthermore, the validity of the Canary number is determined from the error analysis of the response signals, and the feedback is sent to the operator as a voice response in real time.
We successfully completed our first investigational study using the Canary System on 50 subjects (Prototype 1) under the approval of Health Canada. In the study, we measured PTR, LUM amplitude (A), and phase (P) responses at various modulation frequencies from healthy and carious dental enamel. The Canary System did not cause any adverse events or soft or hard tissue trauma. There was no difference in signal from wet or dry tooth surfaces; anterior and posterior healthy tooth surfaces provided the same signal, and the presence of surface stain and biofilm did not affect the signal from healthy tooth surfaces. Overall, results from this first clinical trial showed that the Canary System is safe and discriminates between healthy and carious enamel.
Over the course of our testing before and during the six-month investigational study, the Canary System did not experience any problems in terms of the DAQ module or LabVIEW software functionalities. We used our experience from our first investigational study to develop the second generation of the Canary System (Figure 2).
Figure 2. The Canary System (Prototype 2) Hand piece, Electronic Box in Second Clinical Trial
We developed the pretested second-generation instrument with more user-friendly software features. QDT is currently conducting its second Health Canada-approved investigational study and enrolling 150 patients among three test sites (Figure 3).
Figure 3. Detecting Decay Between Teeth with the Canary System
Based on the second-generation instrument specifications, we contacted a manufacturer to develop our final prototype. This device, approved by regulatory authorities in the U.S., Canada, and European Union, will be fully controlled by LabVIEW software with a similar NI USB OEM DAQ module. An NI affiliated software company has started the final software build for the Canary System device (Figures 4 and 5).
Figure 4. Healthy Tooth Images Captured with LabVIEW with the Canary System Version 3.0.
Figure 5. The Canary System (Prototype 2): An Early Carious Tooth Image Captured in LabVIEW with a Brown Spot
In October 2010, we will launch and market the Canary System to dental clinics and university research labs across Canada, the U.S., and Europe. There are approximately 100,000 dental practices consisting of 200,000 dentists in North America. The European and Japanese markets, which consist of 350,000 dentists, could potentially more than double our sales. Some of our early sales will come from the laboratory and clinical trial market as companies search for accurate, noninvasive technologies for detecting and measuring tooth decay. Our key markets include pediatric dentists, suburban/family offices, and independent dental hygienists and dental therapists.
In dental practice, lower-cost dental assistants could be used to deliver this program under the supervision of a dentist. Our economic model concludes that scanning and treating only 42 patients per month (less than 12 percent of a typical Canadian dental practice) would generate a significant profit.
Advantages of the Canary System
The Canary System offers five major advantages over new and existing technologies. First, it detects tooth decay on all tooth surfaces and around filling materials that are not detected by current technologies, including X-rays. It is noninvasive and patients can avoid unnecessary X-ray radiation. It also captures images of the tooth to provide documentation for billing, patient education, and record keeping. Its accuracy is not affected by saliva, tooth coloration, or plaque, and teeth do not have to be dried, cleaned, or isolated for scanning. Lastly, it collects data including risk factors for tooth decay, providing prognosis for future problems.
Author Information:
Dr. Koneswaran Sivagurunathan Quantum Dental Technologies
748 Briar Hill Ave Toronto M68 163 Canada Tel: (416) 523-8453
National Instruments provides a graphical system design platform for test, control, and embedded design applications that is transforming the way engineers and scientists design, prototype, and deploy systems.
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