A study published in the Journal of Biomedical Optics (JBO) evaluated imaging methods for detecting active tooth decay.
Dental restorations or fillings are commonplace. However, over time they can fail.
The material may not always bond well to the healthy tooth, creating leaks. This allows fluids and bacterial acids to penetrate beneath the filling leading to secondary caries.
Dr. Nai-Yuan N. Chang from the University of California, San Francisco (UCSF) said, “Dentists now spend more time replacing failed restorations than placing new ones due to the maladaptation of bonding materials to tooth structure.”
The Fried Group in the Department of Preventive and Restorative Dental Sciences at UCSF is considering new diagnostic methods to “detect active dental lesions.”
Nai-Yuan explains, “The traditional methods relying on tactile sensation via a dental explorer and visual inspection based on texture and colour are highly subjective and unreliable.
“However, there is currently no established dental imaging technology that can provide diagnostic information with high specificity and sensitivity when assessing dental decay activity.”
The research team decided to investigate using a combination of shortwave-infrared (SWIR) and thermal imaging for the accurate diagnosis of secondary caries. As the media outlet EurekaAlert! explains, “The idea underlying both these methods is that active lesions are more porous than healthy tooth, and these pores hold water. In the SWIR-based approach, one can indirectly detect active lesions by observing changes in the SWIR reflectivity as the tooth dries out. On the other hand, the thermal imaging-based approach relies on the fact that the temperature changes in active lesions during air drying are different from that in healthy tooth, owing to the water trapped in the pores of the lesion.”
After analysing 109 suspected secondary caries cases with both SWIR and thermal imaging, the team concluded that SWIR was superior. EurekaAlert! described the findings, “The SWIR permeability measurements were well correlated with the thickness of the transparent surface layer (TSL) of lesions measured via optical coherence tomography. The team found that the highly mineralised TSL was thickest when a lesion had been fully arrested and needed no further intervention. According to the OCT results, a TSL thicker than 70 µm was a potential indication that a lesion was no longer active.”
Nai-Yuan concluded, “Our work provides further developmental milestones towards meeting the need for better diagnostic and easily operable clinical devices.”