FTIR Analysis of Dentin after Laser and Bur Cavity Preparation

Objective: To assess the chemical  composition of irradiated dentin by Er: YAG laser through absorption spectrum using Fourier transformed infrared spectroscopy (FTIR).This technique can be a tool for the development of most suitable restorative materials when high power laser is used for cavity preparation. 

Method: The roots and occlusal portion of ten premolars were completely removed and the remaining enamel was completely worn out. The dentin specimens were immersed in demineralizing solution for six days at 37°C in order to produce artificial caries-like lesions. After demineralization, five specimens were prepared with Er: YAG laser (260 mJ, 3 Hz, 47 J/cm², 0.81 W) and five specimens were prepared with low-speed carbon steel round bur. The specimens were analyzed in three stages: sound dentin (control), after demineralization and after preparation (laser or bur). For the analysis, three portions of dentin tissue were scraped of each specimen, providing three absorption spectras at each stage of the analysis. The scraped tissue were positioned in a Fourier transform spectrometer for the experimental measurement, the equipment present resolution maxim of 0.5cm^-1 and each spectrum was collected over the range from 4000 to 400 cm⁻¹. The data were analyzed using t-Student test (p <0.05).

Result: The both groups (bur and laser) of demineralized tissue presented higher water (1.61±0.57; 1.03±0.23) and organic matter (0.025±0.009 ; 0.0224±0.0082) contends than the sound and prepared groups(p<0.05). The irradiated tissue presented a reduction of organic matter (0.0032 ± 0.0009) and carbonate (0. 0149 ± 0.0016) when compared to the sound dentin (0.006 ± 0.0018 and 0.0192 ± 0.0008, respectively)(p<0.05). In the cavity preparation with a low-speed bur it was observed increase in organic matter (0.0094 ± 0.0026) and reduced carbonate (0.0184 ± 0.0019) compared to sound dentin (0.0057 ± 0.008 and 0.0202 ± 0.0014, respectively)(p<0.05).

Conclusion: Er: YAG laser irradiation significantly reduced the amount of organic matter present in dentin tissue.