Objective: It is claimed in the literature that laser-treated tooth surfaces are more acid-resistant then untreated surfaces. The purpose of this study was to compare the Ca/P ratio and ultra-morphological changes by Er:YAG (erbium-doped: yttrium-aluminium-garnet) laser irradiation of enamel and dentin, in order to gain more insight into the reasons for the acid resistance.
Methods: Cross-sectioned human premolar teeth (n=5) were irradiated with Er:YAG laser for 80mJ, 120mJ, 180mJ, respectively. Tooth surfaces were investigated with scanning electron microscopy (SEM) and quantitative X-ray dispersive analysis (EDX).
Results: The data were statistically analysed one-way ANOVA and Tukey's post-hoc test.
| Enamel (Ca/P)
| Dentin (Ca/P)
|
non-treated
| 1,96A ± 0,4
| 1,72a ± 0,2
|
80mJ
| 2,10A ± 0,3
| 2,01b ± 0,5
|
120mJ
| 2,09A ± 0,5
| 2,14b ± 0,3
|
180mJ
| 2,16A ± 0,7
| 2,22b ± 0,4
|
The results showed that the quantities of Ca and P (weight %) were changed after the laser application. The laser irradiated dentin groups' revealed statistical difference when compared with the control group. The energy dispersive X-ray analysis of enamel showed no significant difference between the Ca/P ratios of the test groups. The SEM observation revealed that the laser-treated tooth surfaces were irregular and the orifices of dentinal tubules were plugged.
Conclusion: In conclusion, the difference in Ca, P levels after laser-irradiation may help to explain the acquired acid resistance of the dentin surface after laser treatment.