# Influence of Er:YAG and ND:YAG laser irradiation and fluoride application on surface roughness and dentin surface wear after erosive challenge - An in vitro study

## TL;DR

This study tests how Er:YAG and Nd:YAG lasers, with or without fluoride, affect dentin surface roughness and wear after acid exposure.

## Contribution

The study introduces a novel in vitro comparison of Er:YAG and Nd:YAG lasers combined with fluoride for dentin hypersensitivity prevention.

## Key findings

- Er:YAG laser treatment resulted in lower dentin volume loss compared to other methods.
- Groups treated with Nd:YAG showed similar wear to the control group.
- Fluoride application combined with Er:YAG did not significantly reduce surface roughness.

## Abstract

To evaluate the effectiveness of Er:YAG and Nd:YAG laser on dentin hypersensitivity prevention, associated or not to acidulated phosphate fluoride (APF) after erosive challenge.

104 specimens were obtained from bovine dentine and divided into groups (n=13): G1: Er:YAG; G2: Er:YAG followed by application of APF; G3: application of APF followed by Er:YAG, simultaneously; G4: Nd:YAG; G5: Nd:YAG followed by application of APF; G6: application of APF followed by Nd:YAG, simultaneously; G7:application of APF; G8: untreated. The parameters for Er:YAG were:10s, distance of 4mm, water cooling flow of 2mL/min, 2Hz, 3.92J/cm2. For the Nd:YAG: 10s, distance of 1mm, without cooling, 10Hz, 70.7J/cm2. The erosive drink was a cola at 4°C, 3×/day for 1 minute, for 5 days. Roughness and wear analysis were done in confocal laser microscope. Data were statistically analyzed (α=0.05).

As regards roughness, there was no statistically difference among the groups. The groups irradiated with Er:YAG had a volume loss lower. G6 showed higher values than the groups irradiated with Er:YAG and lower than the other groups. The other groups irradiated with Nd:YAG showed similar wear results to the control.

The Er:YAG laser showed the lowest volume loss from wear analysis, suggesting the increased the acid resistance of dentin.

Key words:Dentine sensitivity, Lasers, Sodium fluoride.