Detection of Short-period Remineralization of Early Caries by Human Saliva Using QLF Technology

Objectives: The aim of this in-vitro study was to monitor the ability of QLF technology to detect changes in the degree of remineralization occurring in a short period using human saliva.
Methods: Artificial caries lesions were formed on sound bovine incisors by a 3-day treatment with a demineralizing gel containing Carbopol 2050. Two types of stimulated saliva were collected from 6 healthy persons (3 males and 3 females, mean aged: 27.83±3.47), as follows: 3 hours after tooth brushing in the morning (stimulated saliva group) and immediately after tooth brushing with 1000 ppm NaF dentifrice (dentifrice saliva group). The tooth specimens were immersed in saliva and quantitative light-induced fluorescence-digital (QLF-D) images were taken after 2, 6, 12, 24, and 48 hours to evaluate changes in the fluorescence loss value (ΔF) of the lesions. The histological features were observed and lesion depths were digitally measured by polarized light microscopy (PLM). A paired t-test was performed to assess the differences between ΔF before and after the remineralization process, and the degree of remineralization of each group was compared using an independent t-test.
Results: Before the remineralization, the mean ΔF baseline (%) of the initial demineralized specimens was −13.88±3.47. In both groups, only the differences between the ΔF values obtained at baseline and after 2 hours were statistically significant (paired t-test, P < 0.001). After 2 hours, recovery rates were slightly higher for the ΔΔF in the dentifrice saliva group (8.06%) than in the stimulated saliva group (6.75%), but the difference was not statistically significant (P > 0.05). The PLM micrographs showed that remineralization only occurred on the surface of the lesion in dentifrice saliva group, whereas remineralization occurred in deeper parts in the stimulated saliva group.
Conclusions: The QLF technology could detect minute remineralizations by saliva in as short a period as 2 hours. However, no significantly higher effects of remineralization were observed in the dentifrice saliva group when compared to the stimulated saliva group.