Real-time Observations of Silver Diamine Fluoride (SDF) Activity in Primary Teeth by Synchrotron X-ray Micro-CT

Objectives: Our goal is to determine the innate tooth structures and elements that regulate the formation and kinetics of these silver microstructures. Previously, we found that silver diamine fluoride (SDF) treatment leads to formation of silver microstructures templated by the native tooth structure. These microstructures strengthen the lesion and are likely involved in preventing recurrent caries. The aim of this study is to accurately describe the microstructures and kinetics of formation.

Methods: Recently, we investigated the physical, structural activity of SDF treatment in real-time in order to capture the early formation and kinetics of these microstructures as they occur in the tooth. With the use of a novel in situ method to simulate the physiological, hydrostatic pressure of teeth (at 79 mm Hg to simulate hydraulic equilibria) inside the mouth coupled with synchrotron-based micro-CT methods, we observe in primary teeth the progression of SDF as it is initially applied and over the course of SDF activity.
Results: We find that SDF penetrates the tooth at 1 mm/min (SD = 0.1310 mm/min), and formation of silver-based microstructures occurs over 14 days (SD = 0.35 days).

Conclusions: Using synchrotron microCT with 1.3 µm resolution, we observe filamentous densities up to 500 µm in length and 0.25-7.0 µm in diameter, formed in situ by applying SDF to caries lesions. We show that these “microwires” fill voids in the lesion caused by disease, and permeate through surrounding dentinal tubules over a period of 14 days. These observations can inform clinical application protocols and frequency to optimize SDF-mediated caries arrest.