Comparison of Profilometric and Microindentation Analyses for Determining the Impact of Saliva on the Abrasion of Initially Eroded Enamel.

The aim of this in vitro study was to investigate the impact of saliva on the abrasion of eroded enamel using two measuring methods. A total of 80 bovine enamel specimens from 20 bovine incisors were allocated to four experimental groups (n = 20 specimens per group). After baseline surface microhardness (SMH) measurements and profilometry all specimens were subjected to erosion (2 min, 1% citric acid, pH: 3.6, 37°C). SMH was determined again, and the depths of the Knoop indentations were calculated. Thereafter, specimens were incubated in human saliva (group 1 - no incubation/control, group 2 - 0.5 h, group 3 - 1 h, group 4 - 2 h) before toothbrush abrasion was performed. After final SMH measurements and profilometry, indentations were remeasured, and surface loss was calculated. SMH did not return to baseline values regardless of the length of saliva incubation. Further, an irreversible substance loss was observed for all specimens. With the indentation method, significantly (p < 0.05) more substance loss was found for controls (least square means ± standard error of 198 ± 19 nm) than for groups 2-4 (110 ± 10, 114 ± 11, and 105 ± 14 nm). Profilometric assessment showed significantly more substance loss for controls (122 ± 8 nm) than for group 4 (106 ± 5 nm). Intraclass correlation for interrater reliability between measurement methods was low (0.21, CI: 0.1-0.3), indicating poor agreement. Exposure of eroded enamel to saliva for up to 2 h could not re-establish the original SMH. The amount of measured substance loss depended on the measurement method applied.

Inhibition of enamel erosion by stannous fluoride containing rinsing solutions.

This in vitro study investigated the erosion-inhibiting properties of dental rinses during erosion in the presence of the salivary pellicle. The erosion inhibition by a Sn/F containing dental rinse (800 ppm Sn2+, 500 ppm F ­, pH = 4.5) was compared with a fluoridated solution (500 ppm F ­, pH = 4.5) and water(control). Calcium release and enamel softening were significantly reduced among enamel samples exposed to the Sn/F rinse (group SF)compared to those treated with the fluoride solution (group F) and the control (p 0.05). SEM showed slightly etched enamel interfaces in group SF, whereas the erosion was more pronounced in group F and even more severe in the control group. In conclusion, the Sn/F combination provided the best inhibition of erosion among tested solutions. This study demonstrates the application of different analytical tools for comparative erosion quantification.A strong correlation (r2 ≥ 0.783) was shown between calcium release and enamel softening during demineralization.

Inhibition of enamel erosion by stannous and fluoride containing rinsing solutions.

This in vitro study investigated the erosion-inhibiting properties of dental rinses during erosion in the presence of the salivary pellicle. The erosion inhibition by a Sn/F containing dental rinse (800 ppm Sn(2+), 500 ppm F(-), pH = 4.5) was compared with a fluoridated solution (500 ppm F(-), pH = 4.5) and water (control). Calcium release and enamel softening were significantly reduced among enamel samples exposed to the Sn/F rinse (group SF) compared to those treated with the fluoride solution (group F) and the control (p < 0.05). SEM showed slightly etched enamel interfaces in group SF, whereas the erosion was more pronounced in group F and even more severe in the control group. In conclusion, the Sn/F combination provided the best inhibition of erosion among tested solutions. This study demonstrates the application of different analytical tools for comparative erosion quantification. A strong correlation (r(2) ≥0.783) was shown between calcium release and enamel softening during demineralization.

Effects of enamel abrasion, salivary pellicle, and measurement angle on the optical assessment of dental erosion.

The present study assessed the effects of abrasion, salivary proteins, and measurement angle on the quantification of early dental erosion by the analysis of reflection intensities from enamel. Enamel from 184 caries-free human molars was used for in vitro erosion in citric acid (pH 3.6). Abrasion of the eroded enamel resulted in a 6% to 14% increase in the specular reflection intensity compared to only eroded enamel, and the reflection increase depended on the erosion degree. Nevertheless, monitoring of early erosion by reflection analysis was possible even in the abraded eroded teeth. The presence of the salivary pellicle induced up to 22% higher reflection intensities due to the smoothing of the eroded enamel by the adhered proteins. However, this measurement artifact could be significantly minimized (p<0.05) by removing the pellicle layer with 3% NaOCl solution. Change of the measurement angles from 45 to 60 deg did not improve the sensitivity of the analysis at late erosion stages. The applicability of the method for monitoring the remineralization of eroded enamel remained unclear in a demineralization/remineralization cycling model of early dental erosion in vitro.

Application of the specular and diffuse reflection analysis for in vitro diagnostics of dental erosion: correlation with enamel softening, roughness, and calcium release.

We present assembly and application of an optical reflectometer for the analysis of dental erosion. The erosive procedure involved acid-induced softening and initial substance loss phases, which are considered to be difficult for visual diagnosis in a clinic. Change of the specular reflection signal showed the highest sensitivity for the detection of the early softening phase of erosion among tested methods. The exponential decrease of the specular reflection intensity with erosive duration was compared to the increase of enamel roughness. Surface roughness was measured by optical analysis, and the observed tendency was correlated with scanning electron microscopy images of eroded enamel. A high correlation between specular reflection intensity and measurement of enamel softening (r(2) ≥ -0.86) as well as calcium release (r(2) ≥ -0.86) was found during erosion progression. Measurement of diffuse reflection revealed higher tooth-to-tooth deviation in contrast to the analysis of specular reflection intensity and lower correlation with other applied methods (r(2) = 0.42-0.48). The proposed optical method allows simple and fast surface analysis and could be used for further optimization and construction of the first noncontact and cost-effective diagnostic tool for early erosion assessment in vivo.