The aim of this study was to evaluate the performance of a pen-type laser fluorescence (LF) device (LFpen: DIAGNOdent pen) to detect and monitor the progression of caries-like lesions on smooth surfaces. Fifty-two bovine enamel blocks were submitted to three different demineralisation cycles for caries-like lesion induction using Streptococcus mutans, Lactobacillus casei and Actinomyces naeslundii. At baseline and after each cycle, the enamel blocks were analysed under Knoop surface micro-hardness (SMH) and an LFpen. One enamel block after each cycle was randomly chosen for Raman spectroscopy analysis. Cross-sectional micro-hardness (CSMH) was performed at different depths (20, 40, 60, 80 and 100 μm) in 26 enamel blocks after the second cycle and 26 enamel blocks after the third cycle. Average values of SMH (± standard deviation (SD)) were 319.3 (± 21.5), 80.5 (± 31.9), 39.8 (± 12.7), and 29.77 (± 10.34) at baseline and after the first, second and third cycles, respectively. Statistical significant difference was found among all periods (p < 0.01). The LFpen values were 4.3 (± 1.5), 7.5 (± 9.4), 7.1 (± 7.1) and 5.10 (± 3.58) at baseline and after the first, second, and third cycles, respectively, among all periods (p < 0.05). The CSMH values after the second and third cycles at 20, 40, 60, 80 and 100 μm were 182.8 (± 69.8), 226.1 (± 79.6), 247.20 (± 69.36), 262.35 (± 66.36) and 268.45 (± 65.49), and for the third cycle were 193.7 (± 73.4), 239.5 (± 81.5), 262.64 (± 82.46), 287.10 (± 78.44) and 284.79 (± 72.63) (n = 24 and 23), respectively. No correlation was observed between the LFpen and SMH values (p > 0.05). One sample of each cycle was characterised through Raman spectroscopy analysis. It can be concluded that LF was effective in detecting the first demineralisation on enamel; however, the method did not show any effect in monitoring lesion progression after three cycles of in vitro demineralisation.
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We acknowledge the Post-Graduate Programme in Dentistry of the Federal University of Paraná for the use of their laboratory for micro-hardness analysis and FAPERGS (Fundação de Amparo a Pesquisa do Estado do Rio Grande do Sul) for the financial support (grant ARD no. 11/1737-9). The funder had no role in study the design, data collection and analysis, decision to publish or preparation of the manuscript.
Compliance with ethical standards
This study was approved by the Research and Ethics Committee on Animal Use of the Federal University of Rio Grande do Sul (process no. 20576) since bovine teeth were used. Therefore, no informed consent was necessary.
Conflict of interest
The authors declare that they have no conflict of interest.
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