A Comparative Study of the Photosensitizer Penetration into Artificial Caries Lesions in Dentin Measured by the Confocal Raman Microscopy

Abstract

This study utilized the confocal Raman microspectroscopy (CRM) technique for the first time to investigate the degree of the penetration of toluidine blue-orto (TBO) in artificial caries lesions produced by two distinct caries-inducing models. The dentin specimens (n = 10) were divided into three groups: control, in vitro and in situ. Thereafter, the lesion depth and the demineralization level were evaluated by cross-sectional microhardness (CSMH). CRM mapping across the dentin surface was assessed after the dye application. The CSMH and CRM data were analyzed by t-test and ANOVA, respectively (P < 0.05). The values of the lesion depth and the demineralization areas were higher for in situ samples (P < 0.05). The TBO penetration values (μm) for the control, in vitro and in situ groups were 44.8 ± 5.6, 46.1 ± 4.5 and 51.2 ± 8.5, respectively. There were no statistically significant differences among the groups (P > 0.05). The rate of TBO penetration was detected up to about <50 μm and the demineralization level did not influence the results. These results have showed promising parameters to develop new protocols for deep caries lesions management using photodynamic antimicrobial chemotherapy.

Photodynamic antimicrobial chemotherapy and ultraconservative caries removal linked for management of deep caries lesions

“…Tissue-substrate related factors such as the ability of the photosensitizer to penetrate dentinal tubules to reach the bacteria in appropriate site and the requirement that light should be delivered to the microorganism with appropriated propagation in dentin tissue are considerable obstacles to the clinical use of PACT in caries lesions [32,33]. Dentin represents a unique substrate, in which the dye need to penetrate in demineralized area to reach the disinfection.…”

“…Previous study [32] evaluated the degree of the penetration of toluidine blue orto (TBO) in artificial caries lesions, in which the rate of TBO penetration was detected up to about ∼50 μm. However, PACT aim to reduce the bacterial core in caries-affected dentin and not reach the tissue sterilization.…”

Clinical effect of photodynamic therapy on primary carious dentin after partial caries removal

“…It has been shown that the penetration of toluidine blue and methylene blue in healthy dentin are, respectively, 130 and 190 µm, 26 and this penetration is even smaller in the carious dentin, only 52.6 µm below the surface. 27 Therefore, the altered structure of the carious dentin may not allow adequate penetration of the photosensitizer 28,14 and its interaction with microorganisms such as the ones in the mutans group, which have been observed in dental tubules at depths of 200 µm or more from the dentinal surface. 29 The study of new parameters such as the type and concentration of the dyes may give new perspectives for an antimicrobial effect of PDT.…”

Antimicrobial Photodynamic Therapy as an Adjunct for Clinical Partial Removal of Deciduous Carious Tissue: A Minimally Invasive Approach

“…In our study, we used the MB photosensitizer, so we supposed a large penetration, however, in carious dentin, the depth that the photosensitizer can penetrate is still uncertain because the photosensitizer may have difficulty dispersing in the inner layers of carious tissue, and the light may have difficulty being fully transmitted . The ability of the photosensitizer to penetrate the dentin tubules, to reach the bacteria in deeper stages and the requirement that the light be administered with appropriate propagation in dentin tissue represent obstacles for the clinical use of aPDT in deep carious lesions , since the penetration is limited, and may vary according to the solubility, concentration and size of the dye particle . Despite this, the study of Melo et al .…”