Infrared Photothermal Radiometry Dental Defect Detection
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Solution Overview
Problem
Current dental diagnostic techniques lack non-invasive, non-contact methods for early detection and monitoring of demineralization and caries beneath the enamel or on dental restorations, particularly in opaque media like hard dental tissues, and fail to provide depth profiling effectively.
Innovation Solution
The use of frequency-domain infrared photothermal radiometry (FD-PTR) and modulated laser luminescence (FD-LUM) for detecting defects in dental tissues, employing a handheld probe with optical fiber bundles and lock-in amplifiers to demodulate and compare photothermal and luminescence signals for depth profiling and defect identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dental diagnostic techniques are used, then the diagnostic process is simple and accessible, but the ability to detect early demineralization and caries beneath enamel or on restorations is insufficient
Solution Approach 1:
The patent combines photothermal radiometry (PTR) and luminescence (LUM) detection methods into a single integrated apparatus. The system uses a laser source that simultaneously generates both PTR and LUM signals, with optical fibers collecting both signal types through the same access point. This merging approach achieves high detection sensitivity for early demineralization while avoiding the need for multiple separate diagnostic devices, thus reducing overall system complexity.
Solution Approach 2:
The diagnostic apparatus is designed to perform multiple functions: it detects both photothermal radiometric signals and luminescence signals from the same tooth region, provides depth profiling capability, and can monitor both enamel and dentin structures. The single apparatus handles various diagnostic tasks (early caries detection, demineralization monitoring, restoration evaluation) that would otherwise require different specialized devices, thereby improving measurement precision without proportionally increasing device complexity.
2Length of stationary object
If optical imaging techniques are used to inspect dental tissues, then the equipment is simple and easy to operate, but the penetration depth into opaque media is limited
Solution Approach 1:
The patent utilizes the frequency dependence of thermal wave penetration depth to achieve depth profiling. By measuring PTR signals at multiple modulation frequencies, the system probes different depths within the tooth structure. Lower frequencies penetrate deeper while higher frequencies provide surface information, allowing the construction of depth-resolved profiles of dental tissues and defects without requiring physical sectioning or sacrificing depth resolution.
Solution Approach 2:
The patent employs thermal waves as an intermediary to overcome the limitations of direct optical imaging in opaque media. The laser-induced thermal waves can penetrate deeper into dental tissues than visible light, carrying information from subsurface regions. The PTR detection system measures these thermal waves to retrieve depth information about dental structures, effectively using thermal radiation as a mediator to access information beyond the optical penetration depth.
3Measurement precision
If pulsed laser photothermal or photoacoustic detection is used, then the detection capability is high, but the risk of optical damage to tissue increases
Solution Approach 1:
The patent employs continuous-wave laser radiation with intensity modulation instead of high-power pulsed laser irradiation. The laser intensity is modulated at frequencies between 1 Hz and 100 kHz, creating periodic thermal waves that penetrate dental tissues safely. This periodic action maintains high detection precision for defects and demineralization while avoiding the thermal damage and cavitation risks associated with pulsed laser techniques, as the average power remains low and the thermal effects are reversible.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables non-invasive, depth-profiling detection of dental defects, including demineralization and caries, with high sensitivity and specificity, complementing conventional techniques like QLF and OCT, and allowing for ongoing monitoring and treatment guidance.
Implementation Method 1
radiation absorption and non-radiative energy conversion followed by a small temperature rise
Implementation Method 2
modulated thermal infrared (black-body or Planck radiation) response of a turbid medium
Implementation Method 3
laser-induced fluorescence of enamel
Data Source
AI summary
There is provided a high-spatial-resolution dynamic diagnostic instrument which can provide simultaneous measurements of laser-induced frequency-domain infrared photothermal radiometric and alternating-current (ac) modulated luminescence signals from defects, demineralization, remineralization and caries in teeth intraorally. The emphasis is on the abilities of this instrument to approach important problems such as the detection, diagnosis and ongoing monitoring of carious lesions and or defects on the occlusal pits and fissures, smooth surfaces and interproximal areas between teeth which normally go undetected by x-ray radiographs or visual examination. The instrument is also able to detect early areas of demineralized tooth and or areas of remineralized tooth as well as defects along the margins of restorations. This capability of inspecting a local spot can be extended to a modulated imaging of sub-surface of target tooth by using a multi-array infrared camera. Two configurations of the instrument are presented.