Evaluation of Laser Fluorescence in the Monitoring of the Initial Stage of the De-/Remineralization Process: An in vitro and in situ Study

Abstract

This study aimed to evaluate laser fluorescence (LF) for monitoring the initial stage of subsurface de- and remineralization (<150 μm depth). Ninety-six sound blocks of bovine enamel, selected according to surface hardness (SH) and LF were used in two experimental studies, in vitro and in situ. In vitro, blocks were exposed to a demineralizing solution, then remineralized by pH cycling for 6 days. In situ, 10 volunteers wore acrylic palatal appliances, each containing 4 dental enamel blocks that were demineralized for 14 days by exposure to 20% sucrose solution. Following this treatment, blocks were submitted to remineralization for 1 week with fluoride dentifrice (1,100 μg F/g). In both experiments, SH and LH were measured after demineralization and after remineralization. Further, enamel blocks were selected after the demineralization/remineralization steps for measurement of cross-sectional hardness and integrated loss of subsurface hardness (ΔKHN). SH and ΔKHN showed significant differences among the phases in each study. LF values for sound, demineralized and remineralized enamel were: 5.2 ± 1.1, 8.1 ± 1.2 and 5.6 ± 0.8, respectively, in the in vitro study, and 5.3 ± 0.3, 16.5 ± 4.7 and 6.5 ± 2.5, respectively, in the in situ study, values for demineralized enamel being significantly higher than for sound and remineralized enamel in both studies. However, LF was correlated with ΔKHN only in situ. LF was capable of monitoring de- and remineralization in early lesions in situ, when bacteria are presumably present in the caries lesion body, but is not correlated with mineral changes in bacteria-free systems.

Occlusal Caries Depth Measurements Obtained by Five Different Imaging Modalities

“…DIAGNOdent (KaVo, Biberach, Germany), a quantitative laser fluorescence (LF) unit, is currently used as an aid in the diagnosis of occlusal carious lesions. LF was found to be capable of monitoring de-/re-mineralization process in early caries lesions in situ [26]. Electrical resistance measurement (ERM) which is proposed for occlusal caries detection uses a probe with a coaxial airflow and depends on the permeability changes due to caries demineralization of the tissues [27].…”

Cross-Sectional Microhardness of Human Enamel Subjected to Erosive, Cariogenic or Combined Erosive/Cariogenic Challenges

“…The 3 hardness measurements at each depth were then averaged. The ⌬ KHN was calculated according to Spiguel et al [2009].…”

“…This method has been widely used to evaluate caries lesions of enamel developed in situ [Aires et al, 2006;Spiguel et al, 2009;Takeshita et al, 2009].…”

In vitro Evaluation of the Effect of Mouth Rinse with Trimetaphosphate on Enamel Demineralization

“…Integrated area of the hardness (KHN × μm) for the lesion into sound enamel was calculated by the trapezoidal rule (GraphPad Prisma, version 3.02) and subtracted from the sound enamel to obtain the integrated area of the subsurface regions in the enamel, which was termed integrated loss of subsurface (ΔKHN; kgf/mm 2 × μm; fig. 1 g) [Spiguel et al, 2009]. To analyze the patterns of demineralization, differential hardness profiles for the negative control and TMP groups (i.e., placebo hardness values minus hardness value of each group) were calculated.…”