Assessment of the preventive effects of Nd:YAG laser associated with fluoride on enamel caries using optical coherence tomography and FTIR spectroscopy

Objective This in vitro study characterized and monitored, by Optical Coherence Tomography (OCT) and Fourier Transformed Infrared Spectroscopy (FTIR), the effects of the association of acidulated phosphate fluoride gel (APF-gel) and Nd:YAG (neodymiun:yttrium-aluminum-garnet) laser, as sequencial treatments, in the prevention of incipient enamel caries lesions. Methods 120 human enamel samples were randomized into 3 groups (n = 40): APF-gel (1.23% F-, 4 min.); Laser+APF (Nd:YAG laser irradiation—0.6W, 84.9J/cm2, 10Hz, followed by APF-gel); and APF+Laser (APF-gel followed by laser irradiation). The samples were subjected to a 15-day pH-cycling, evaluated by OCT (quantification of optical attenuation coefficient–OAC) and FTIR (analysis of carbonate and phosphate content) before treatments, after treatments, and on the 5th, 10th and 15th days of pH-cycling. The statistical analysis was performed (α = 5%). Results The Optical Attenuation Coefficient (OAC) assessed by OCT increases with the progression of demineralization, and the Laser+APF presented the highest values of OAC in 10th and 15th days of pH-cycling. Nd:YAG decreased the carbonate content after treatment regardless of the application order of the APF-gel, while APF-gel did not interfere in the composition of enamel. The carbonate content was also changed in the first 5 days of the pH-cycling in all groups. Conclusion Nd:YAG laser irradiation before or after the application of APF-gel did not influence the appearance of incipient caries lesions, showing no synergistic effect. Regardless of the application order of the APF-gel, laser irradiation reduces the carbonate content of the enamel, which also changes during the demineralization process. However, irradiation before the application of APF-gel increased the speed of progression of the lesions, which positively impacts public health as it can prevent caries disease, even in high risk individuals. OCT and FTIR are suitable for assessing this effect.

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Using Optical Attenuation Coefficient to Monitor the Efficacy of Fluoride and Nd:YAG Laser to Control Dentine Erosion

Applied Sciences ◽

10.3390/app9071485 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1485

Author(s):

Marcia C. Dias-Moraes ◽

Cassio A. Lima ◽

Anderson Z. Freitas ◽

Ana Cecilia C. Aranha ◽

Denise M. Zezell

Keyword(s):

Optical Coherence Tomography ◽

Citric Acid ◽

Laser Irradiation ◽

Attenuation Coefficient ◽

Nd:Yag Laser ◽

Morphological Changes ◽

Optical Coherence ◽

Protective Effects ◽

Total Period ◽

Optical Attenuation

The present study evaluated the protective effects that are induced by fluoride and Nd:YAG laser irradiation to control dentine erosion. One hundred and twenty bovine dentine slabs were eroded with citric acid twice a day for a total period of 15 days. At day 10, the samples were randomly assigned into eight groups: C (Control); F (Fluoride); L1 (Nd:YAG laser, 1 W, 100 mJ, 79.5 J·cm−2); L2 (Nd:YAG laser, 0.7 W, 70 mJ, 55.7 J·cm−2); L3 (Nd:YAG laser, 0.5 W, 50 mJ, 39.7 J·cm−2); F + L1; F + L2; and, F + L3. Optical Coherence Tomography images were collected from the surface of the samples in order to monitor the alterations that were induced by erosion and the effectiveness of each treatment using the Optical Attenuation Coefficient (OAC). OAC values that were calculated for samples from groups C, F, L1, L3, FL1, and FL3 indicated no protective effects against the progression of erosive lesions. Samples from L2 and FL2 groups presented OAC values, indicating that laser irradiation under this condition did not induce the formation of craters on dentine tissue and promoted sufficient chemical and morphological changes to avoid the progression of dentine erosion.

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