Microstructural Changes of Human Dentin Tubules after Citric Acid Immersion of Specimens Treated with Different Desensitising Approaches: An SEM Analysis

Purpose: This in-vitro study aimed to evaluate the effectiveness and acid resistance on dentin surfaces following the application of a linear-oscillating device (LOD) with a hydroxyapatite-based polishing fluid, Er:YAG laser or sodium fluoride (NaF) used alone or in combinations for desensitising purposes.
Materials and Methods: Freshly extracted impacted third molars were used to obtain 120 specimens, all completely immersed in 1% citric acid for 5 min and divided randomly into 6 groups. Group I, with no treatment, served as the control; group II: Er:YAG laser (30 Hz, 60 mJ/pulse, 10 s); group III: NaF gel; group IV: LOD; groups V and VI: the combinations of NaF+Er:YAG and LOD+Er:YAG, respectively, were applied. Following these treatments, the effectiveness of each was evaluated in half of the specimens in each group (n = 10). The other half of the specimens (n = 10) served for acid-resistance testing. All evaluations were made on SEM photomicrographs.
Results: The post-treatment tubule diameters and numbers were the lowest with LOD+Er:YAG, followed by NaF+Er:YAG, LOD, Er:YAG and NaF. Paired comparisons revealed LOD+Er:YAG to be the best treatment method (p 0.05). After 3 h of acid immersion, all treatments revealed significant increases (p 0.05) in both tubule number and diameter study between post-treatment and post-acid immersion values. The exception was LOD+Er:YAG. LOD+Er:YAG showed the highest resistance to acid challenge, presenting the lowest increase in tubular diameters and numbers followed by NaF+Er:YAG, LOD, Er:YAG and NaF.
Conclusion: Combined LOD+Er:YAG treatment revealed the highest effectiveness and acid resistance. Further clinical studies are warranted to confirm these in-vitro results. Keywords: YAG laser, human dentin tubules, linear-oscillating device