Artificial Caries Resistance in Enamel after Topical Fluoride Treatment and 445 nm Laser Irradiation

Abstract

Objective This in vitro study is aimed at investigating the caries preventive effectiveness of 445 nm diode laser in combination with topical fluoridation. Materials and methods A total of 30 caries-free bovine teeth were used in this study. Eighteen teeth were covered with nail varnish except four windows on the labial surface. The windows were assigned to no treatment/control (C), laser (L) (0.3 W, 60 s, and 90 J/cm2), fluoride (F), and fluoride followed by laser (FL) treatment groups. Artificial caries lesions were created, and the teeth were sectioned and investigated under polarized light microscopy for quantitative measurement of the resulted lesion depth. Ten teeth were used for surface temperature measurement and two teeth for scanning electron microscopy (SEM). Extra twelve human molars were used for the intrapulpal temperature measurement. The absorbance of fluoride at 445 nm was measured. Results The means of lesion depth for the C, L, F, and FL groups were 123.48 (±21.93), 112.33 (±20.42), 99.58 (±30.68), and 89.03 (±30.38) μm, respectively. The pairwise differences of the L, F, and FL groups compared with the C group were significant (p < 0.05). The differences between groups were tested: FL versus L p=0.02, F versus L p=0.16, and FL versus F p=0.91, and the difference of the F versus FL was not significant (p=0.91). Temperature increment at the enamel surface and pulp roof were ∆T = 16.67 (±4.11) and 2.12 (±0.66)°C, respectively. The topical fluoride absorbance at 445 nm is five orders higher than that at 810 nm. SEM shows that after laser irradiation the enamel surface was intact and without thermal damage. Conclusions The 445 nm laser irradiation may be useful for caries prevention, and its effectiveness is lower than those previously achieved using the argon ion laser.

Combined effects of a topical fluoride treatment and 445 nm laser irradiation of enamel against a demineralization challenge: A light and electron microscopic ex vivo study

“…The lasing parameters of 0.3 W and 90 J/cm2 were based on a previous study and were verified by pretesting experiments of irradiation at 0.3 W for 10 and 60 s, which corresponds to applied doses of 10 and 90 J/cm 2 , respectively [22], These settings were adjusted to those previously used for argon ion laser (0.2-0.3 W and 10-100 J/cm 2 ) [18,25,29].…”

“…A verified no transmission art paper containing a window of 5 mm in diameter was placed on the enamel surface to avoid irradiation of the adjacent areas. The irradiation was conducted in continuous wave mode at 0.3 W for 60 s with an applied dose of 90 J/cm 2 ( Table 1) [22]. The power emitted from the laser device was calibrated using a power meter (LabMax Top) and a detector (PM-10), both from Coherent, CA, USA.…”

“…Additionally, the absorbed 445 nm laser light by the topical amine fluoride is 22% (0.241 a.u. ), and the elevation of surface temperature of enamel to ΔT of 290.16˚K during lasing may accelerate the rate of the chemical reaction between the fluoride and enamel [22]. By increasing the CaF 2 formation both on the enamel surface and up to 40 μm of the subsurface, the diffusion pathways of the enamel will become occluded, leading to reduced dissolution of the enamel [6].…”

“…This difference may lead to different absorption properties of the laser light by the tissue chromophores, which in turn leads to variations in the preventive effectiveness. Although it was concluded that there is no significant difference if the fluoride is applied before or after laser irradiation, after conducting pre-experiments and based on previous studies, the fluoride was applied prior to laser irradiation [22,21]. When treatment efficacy of the fluoride plus laser of this histology study (77%) are compared with that of a recent 445 nm polarized light microscopy (PLM) study (28%) for prevention of white spot lesions, it shows a higher effectiveness [22]; although both studies irradiated bovine teeth with similar laser settings, the variation in the effectiveness of treatment could be explained by the difference in the investigation methodology.…”

The Effect of Silver Diamine Fluoride and Fluoride Varnish on Microhardness of Primary Teeth Enamel (An In Vitro Study)

“…Remineralizing agents make a super saturated environment around the decayed lesion, thus, it will prevent mineral loss and concentrate the phosphate and calcium ions in the vacant areas (5) . Fluoride is the most effective measure for the prevention of demineralization which can be used either topically or systemically (6) .…”