Enhanced Silver Diamine Fluoride Therapy Using the PILP System: A Nanoindentation Study

Objectives: Silver diamine fluoride (SDF) is a non-invasive procedure proven to be a successful and effective treatment for arresting caries. However, with current standard SDF treatment, remineralization kinetics and the extent of arrest is limited to the outer layer of the lesions, leaving the underlying layer of soft dentin infected and demineralized. Thus, there is a need for a modified strategy that promotes additional lesion remineralization in SDF treatment. In this study, we report on the design of SDF that contains poly-L-aspartic acid (pAsp) to apply the “polymer-induced liquid-precursor” (PILP) system to artificial lesions in dentin.
Methods: 100 mg/mL of pAsp was mixed into commercial 38% SDF solution (pAsp-SDF) and applied on standardized artificial lesions with a microbrush and allowed to absorb for 1 min; excess was removed and rinsed with water. Nanomechanical recovery of hardness and elastic modulus within deep demineralized artificial lesions following SDF application in the presence or absence of pAsp was measured in water using AFM-based nanoindentation.
Results: Our study (Figure, n = 3, taken from 9-10 lines of nanoindents) showed the topical SDF treatment led to a preferential enhancement of nanomechanical properties (i.e., arrest or rehardened caries lesions) of the outer lesion. Interestingly, pAsp-SDF showed a reduction in the preferential arrested caries of the outer lesion and an enhanced rate, depth of penetration, and extent of arrested lesions. However, the precise mechanism of action of pAsp-SDF is not completely understood. Remineralization follow-up will be evaluated in subsequent studies, in the clinical setting, where the pAsp would be readily diluted by pulpal fluid or saliva in the oral cavity and play a crucial role in the caries remineralization progress.
Conclusions: This initial study provides supporting data that integrating the PILP-process into a dental treatment is feasible and can optimize SDF penetration and caries arrestment.