Usefulness of subtraction thermography in the evaluation of blood vessels and lymphatic vessels in the dental pulp
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-01-01 |
| Journal | Acta of Bioengineering and Biomechanics |
| Authors | Maria WiĆniewska-Wrona, Maria Szymonowicz, Piotr Kuropka, Zbigniew Rybak, Natalia Struzik |
| Institutions | WrocĆaw University of Environmental and Life Sciences, WrocĆaw University of Science and Technology |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study validates Subtraction Thermography (ST) as a non-ionizing, quantitative method for evaluating vascular and lymphatic vessel density in dental pulp, correlating thermal dissipation rates with inflammatory status.
- Core Value Proposition: ST provides a high-resolution, non-invasive technique to map subsurface structural heterogeneity (porosity and fluid circulation) by analyzing transient heat dissipation.
- Key Achievement: Successfully differentiated cooling rates between healthy and carious teeth, demonstrating that inflammation (hyperaemia) leads to increased fluid circulation and slower temperature change in specific regions (ROI2).
- Methodology: Active thermography involving uniform thermal pulse (heating to 40 °C) followed by free cooling, analyzed using a subtraction technique (C = A - B) to eliminate surface emissivity effects.
- Quantitative Metrics: Temperature Contrast (C(t)) and Rate of Temperature Change (I) indices were calculated to quantify differences in thermal properties between regions of interest (ROI).
- Structural Inference: Regions exhibiting the smallest temperature difference (ÎT) after cooling (ROI2) are inferred to have higher vascular density and fluid flow, consistent with increased inflammation intensity.
- Engineering Relevance: The technique serves as a robust Non-Destructive Evaluation (NDE) method for characterizing thermal diffusivity and structural integrity in heterogeneous biological and composite materials.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Sample Size (Total) | 24 | Teeth | 10 Healthy, 14 Carious (Molars/Premolars) |
| Thermal Pulse Temperature (To) | 40 ± 0.5 | °C | Uniform heating target temperature. |
| IR Lamp Power | 250 | W | Used for thermal excitation pulse. |
| Heating Duration (Max) | 5 | min | Used for long thermal pulse determination. |
| Cooling Duration | 120 | s | Time window for free cooling measurement. |
| Ambient Temperature (Tamb) | 22 ± 0.5 | °C | Laboratory ambient conditions during cooling. |
| Thermal Camera Model | FLIR P640 | N/A | High-resolution thermal imaging camera used. |
| Camera Resolution | 640 x 320 | pixels | Resolution of recorded thermograms. |
| Recording Distance | approx. 3 | cm | Distance maintained using a spacer ring. |
| Sampling Frequency | 30 | Hz | Initial recording frequency of thermograms. |
| Analysis Interval | 2 | s | Interval used for statistical analysis (12 thermograms total). |
| Mean Temperature Contrast (C(t)) | 1.370 | N/A | Geometric mean contrast index (Example Tooth 12). |
| Absolute Pulp Limit (Restorative) | 41.5 | °C | Temperature limit to avoid pulp necrosis/pulpitis. |
Key Methodologies
Section titled âKey MethodologiesâThe study utilized active dynamic subtraction thermography combined with regional analysis (ROI) to quantify thermal dissipation differences in extracted teeth.
- Sample Preparation: Freshly extracted healthy and carious molars/premolars were cut transversely using a diamond saw, thoroughly dried, and placed in saline solution prior to testing.
- Thermal Excitation: Samples were uniformly heated using a 250 W Infrared (IR) lamp positioned 12 cm away, achieving a target surface temperature (To) of 40 ± 0.5 °C.
- Data Acquisition (Cooling Phase): A sequence of thermograms was recorded over 120 seconds of free convective cooling (Tamb = 22 ± 0.5 °C) using a high-resolution FLIR P640 camera (30 Hz sampling rate, 3 cm distance).
- Subtraction Thermography (ST): The temperature distribution matrix at the end of cooling (t = 120 s, Matrix B) was subtracted from the initial matrix (t = 0 s, Matrix A) to generate the resultant image (Matrix C). This process standardizes the measurement by eliminating the influence of varying surface emissivity coefficients (color, roughness).
- Equation Concept: C(i, j) = Standardization [A(i, j) - B(i, j)].
- Region of Interest (ROI) Analysis: Three specific regions were defined on the resultant thermogram (C):
- ROI1: The entire tooth cross-section contour.
- ROI2: The area exhibiting the smallest temperature difference (ÎT), indicating the slowest cooling rate (inferred high vascular/fluid density).
- ROI3: The area exhibiting the largest temperature difference (ÎT), indicating the fastest cooling rate (inferred homogeneous, less porous structure).
- Index Calculation: Quantitative indices were derived from the ROI data:
- Temperature Contrast (C(t)): Calculated as the ratio of ÎT in the high-difference region (ROI3) to the ÎT in the low-difference region (ROI2) at specific time points (e.g., 30s, 60s, 120s).
- Rate of Temperature Change (I): Calculated as the geometric mean of the percentage temperature decrease between successive 10-second intervals.
- Validation: Results were compared against the âgold standardâ techniques of lymphoscintigraphy and X-ray examination to verify the correlation between thermal indices and vascular/inflammatory status.
Commercial Applications
Section titled âCommercial ApplicationsâThe principles and techniques demonstrated in this researchâspecifically active dynamic subtraction thermography and quantitative analysis of thermal diffusivityâare highly relevant to several engineering and industrial sectors focused on Non-Destructive Evaluation (NDE) and material characterization.
- Non-Destructive Evaluation (NDE) of Composites:
- Detection of subsurface defects, delamination, and porosity in fiber-reinforced plastics, ceramics, and layered composite structures used in aerospace and automotive industries.
- Assessment of bonding quality and integrity in adhesive joints by mapping thermal conductivity variations.
- Material Characterization and Quality Control:
- Quantitative measurement of thermal diffusivity and conductivity (W/mK) in heterogeneous materials, providing insight into structural density and homogeneity.
- Monitoring curing processes in polymers and resins by tracking changes in thermal properties over time.
- Biomedical Device Manufacturing:
- Quality assurance for dental restorative materials (e.g., composites, glass ionomers) to ensure minimal thermal stress during placement and curing, preventing thermal damage to adjacent tissues.
- Development of Thermophotonic Lock-In Imaging (TPLI) systems for high-resolution subsurface inspection of biological tissues and biomaterials.
- Thermal Management Systems:
- Validation and testing of heat dissipation efficiency in microelectronics and heat sinks by mapping localized thermal gradients under transient loading conditions.
- Industrial Process Monitoring:
- Real-time monitoring of fluid flow and heat exchange in industrial piping or reactors, where changes in flow rate or blockage manifest as localized temperature anomalies.
View Original Abstract
Purpose Caries or iatrogenic thermal trauma of the teeth have a significant impact on the dental pulp structure connected with stimulation of angiogenesis and lymphangiogenesis. Therefore, the aim of the study was to identify the difference in the rate of heat dissipation by vessels present in the dental pulp. Methods Freshly extracted healthy and carious teeth were cut on a diamond saw and subjected to thermographic testing. Tooth samples were heated to 45±0,5°C using a lamp. A high-resolution thermal imaging camera was used to record the series of thermograms until the samples reached a temperature of 25±0,5°C. Results Thermographic examination of healthy and cariously changed teeth revealed areas of increased tissue fluid flow combined with heat release, which may indirectly indicate the existence of vessels in these areas. On a thermal imaging camera, variations in the rate of heating or cooling across several cross-sectional sections of the same tooth indicate changes in the dental structureâs density. Conclusions In caries-affected teeth, intracanalicular fluid flows are different than those of healthy teeth. Therefore, it can be concluded that the pulp vessels enabling circulation of body fluids - blood and lymphatic - increases with the intensity of inflammation. Maintaining the homeostasis of the dental pulp depends heavily on the circulation of bodily fluids within the dental organ.