Morphological and chemical alterations of root surface after Er:Yag laser, Nd:Yag laser irradiation: A scanning electron microscopic and infrared spectroscopy study

Aims and Objectives: This study aimed to evaluate the efficacy of Nd:YAG and Er:YAG lasers in removing the smear layer and to study the morphological and chemical alterations of the root surface using scanning electron microscopy (SEM) and infrared (IR) spectroscopy. Material and Methods: Fifty-five extracted upper incisor teeth were collected and 110 specimens of size 3 mm x 4 mm x 1 mm were prepared. For SEM evaluation, these samples were divided into six groups: A, B, and C. Group A comprised five samples that served as control. Groups B and C were further divided into five subgroups and each subgroup comprised five samples. All the specimens within the subgroups of B and C irradiated with 100, 200, 300, 400, and 500 mJ of Er:YAG laser and 211.66, 423.33, 635, 846.66, and 1058.33 J/cm2 of Nd:YAG laser, respectively. The morphological changes of the laser-treated sites were observed qualitatively using an arbitrary scale under SEM. The data obtained were statistically analyzed by one-way analysis of variance (ANOVA) multiple range test by Turkey's honestly significant difference and Mann-Whitney U test. In chemical structural changes, Group D comprised five samples that served as nonirradiated control and Groups E and F were irradiated with the same aforementioned parameter and evaluated using Fourier-transform infrared spectroscopy. Results: Er:YAG laser at 100 mJ effectively removed smear layer without any crater formation. The Nd:YAG laser removed the smear layer at the energy density of 211.66 J/cm2 and 423.33J/cm2. The energy density of 1058.33 J/cm2 showed visible charring and deep crater with increased area of melted and resolidified minerals in SEM. In the chemical changes, IR spectroscopy graph showed the reduction in peak intensity beyond 846.66 J/cm2 of and new absorption band was noticed (2010cm-1 and 2017cm-1) at samples treated with 846.66 and 1058.33 J/cm2 of Nd:YAG laser. Conclusion: Er:YAG laser at lower energy density effectively removed smear layer without production of toxic substance as compared with Nd:YAG laser. Thus, Er:YAG laser can be used as an effective root biomodification agent.