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FTIR and SEM Analysis of CO2 Laser Irradiated Human Enamel

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FTIR and SEM Analysis of CO2 Laser Irradiated Human Enamel a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 1 1 5 3 – 1 1 5 8 Available online at www.sciencedirect.com journal homepage: http://www.elsevier.com/locate/aob FTIR and SEM analysis of CO2 laser irradiated human enamel a, b a Alessandra Marques Correˆa-Afonso *, Luciano Bachmann , Cı´ntia Guimara˜ es de Almeida , c a Silmara Aparecida Milori Corona , Maria Cristina Borsatto a Departamento de Clı´nica Infantil, Odontologia Preventiva e Social, Faculdade de Odontologia de Ribeira˜o Preto, Universidade de Sa˜ o Paulo, Ribeira˜ o Preto, SP 14040-904, Brazil b Departamento de Fı´sica, Faculdade de Filosofia, Cieˆncias e Letras de Ribeira˜ o Preto, Universidade de Sa˜ o Paulo, Ribeira˜ o Preto, SP 14040-901, Brazil c Departamento de Odontologia Restauradora, Faculdade de Odontologia de Ribeira˜ o Preto, Universidade de Sa˜ o Paulo, Ribeira˜ o Preto, SP 14040-904, Brazil a r t i c l e i n f o a b s t r a c t Article history: Objectives: Considering the enamel chemical structure, especially carbonate band, which Accepted 2 February 2012 has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO2 laser by means of FTIR spectroscopy Keywords: and SEM analysis. Design: The enamel surfaces were analysed on a spectrometer for acquisition of the Carbon dioxide laser absorption spectrum relative to the chemical composition of the control sample. The Fourier transform infrared 2 spectroscopy irradiation was conducted with a 10.6-mm CO2 laser (0.55 W, 660 W/cm ). The carbonate À1 À1 SEM absorption band at 1600–1291 cm as well as the water absorption band at 3793–2652 cm Enamel was measured in each sample after the irradiation. The water band was measured again 24- h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was À1 normalized by the phosphate band (1190–702 cm ). Results: There was a statistically significant decrease ( p < 0.05) in the water content after irradiation (control: 0.184 Æ 0.04; irradiated: 0.078 Æ 0.026), which increased again after rehy- dration (0.145 Æ 0.038). The carbonate/phosphate ratio was measured initially (0.112 Æ 0.029) and its reduction after irradiation indicated the carbonate loss (0.088 Æ 0.014) ( p < 0.05). Conclusion: The 10.6-mm CO2 laser irradiation diminishes the carbonate and water contents in the enamel after irradiation. # 2012 Elsevier Ltd. Open access under the Elsevier OA license. on the enamel surface and have shown significant inhibition 1. Introduction of enamel demineralization of 50–98% upon CO2 laser treatment, depending on the laser beam type, wavelength, 1 The CO2 laser was developed by Patel et al. and uses a mixture operational mode, and energy output. These studies have of CO2, N2, and He, with CO2 being the active laser medium. attempted to explain the effectiveness of this method by 2–6 Many previous studies have explored the effect of CO2 laser considering that the energy absorption by the enamel during * Corresponding author at: Departamento de Clı´nica Infantil, Odontologia Preventiva e Social, Faculdade de Odontologia de Ribeira˜o Preto, Universidade de Sa˜o Paulo (USP), Av. do Cafe´, S/N Monte Alegre, CEP: 14040-904, Ribeira˜o Preto, SP, Brazil. Tel.: +55 16 3602 4113; fax: +55 16 3633 0999. E-mail addresses: [email protected], [email protected] (A.M. Correˆa-Afonso), [email protected] (L. Bachmann), [email protected] (C.G. de Almeida), [email protected] (S.A.M. Corona), [email protected] (M.C. Borsatto). 0003–9969 # 2012 Elsevier Ltd. Open access under the Elsevier OA license. doi:10.1016/j.archoralbio.2012.02.004 1154 a r c h i v e s o f o r a l b i o l o g y 5 7 ( 2 0 1 2 ) 1 1 5 3 – 1 1 5 8 À1 the irradiation promotes alterations that diminish tissue spectrum acquisitions between 4000 and 900 cm under the solubility. This theory is based on the fact that the CO2 laser Attenuated Total Reflectance (ATR) mode. wavelength is compatible with the absorption peak of The irradiation was conducted with a CO2 laser system carbonated hydroxyapatite, which is the major component emitting at a wavelength of 10.6 mm (PC015D Shangai Jue Hua 7 of the dental enamel (85%) and then the energy is strongly Laser Technology Development Co., China). The laser beam absorbed and efficiently converted to heat without damage to was delivered in the no contact mode. The irradiation distance 8 the underlying or surrounding tissues, thereby causing from the target site was 4 mm. The parameter settings were as ultrastructural and chemical modifications on the irradiated follows: mean power 0.5 W, energy per pulse 0.05 mJ, idle time enamel and enhancing enamel acid resistance. 0.001 s and duty time (pulse width) 100 ms. The emitted power In this sense, knowledge about the chemical composition was measured as 0.55 W by means of a power meter (Coherent of irradiated enamel is of paramount importance for the Field Max II; Coherent, USA) and each specimen was irradiated development of studies on caries prevention using laser. The for 10 s. Using the knife edge method and considering the number of works focusing on infrared (IR) spectroscopic Gaussian distribution and the radial symmetry of the laser 2 features of human tissues has increased, since IR spectrosco- beam, the beam diameter at 1/e of the intensity level was py provides valuable information about their chemical determined as being 0.31 cm, so the mean irradiance and the structure. Fourier transform infrared (FT-IR) spectroscopy is energy density could be appropriately determined as 660 W/ 2 2 an absorption spectroscopy technique that evaluates the cm and 0.066 J/cm , respectively. In the same way, the interaction between electromagnetic radiation and the target frequency of irradiation was calculated (P = E  f) resulting in material by using the infrared radiation of the electromagnetic 10 kHz. spectrum. It is commonly employed for the examination of The absorption spectra were uploaded by using the both inorganic and organic materials and has been used for OriginPro 8.0 software (Origin Lab Corporation, Northampton, establishment of quantitative measurements for mineralized MA, USA) and the carbonate absorption band at 1600– À1 tissue composition and for investigation of physical properties 1291 cm as well as the water absorption band at 3793– À1 with a view to gaining insight into qualitative aspects. The 2652 cm was measured in each sample after the irradiation. FTIR method has been successfully utilized for analysis of The water band was measured again 24-h after the irradiation. 9–11 dental hard tissue. The band area of each chemical compound was delimited, the In this context, the objective of the present study was to background was subtracted, and the area under each band assess the chemical alterations on the enamel irradiated was integrated by utilizing the appropriate tools of the with CO2 laser by means of FTIR spectroscopy and SEM program OriginPro 8.0. Each area was normalized by the À1 analysis. phosphate band (1190–702 cm ). The final CO3/PO4 and H2O/ PO4 area ratios correspond to the relative concentration of carbonate and water, respectively. 2. Materials and methods As for the SEM analyses, three untreated samples and three treated samples were cleaned by ultrasound for 10 min. The Ten unerupted third molars (from the Human Tooth Bank of samples were then immersed in 2.5% glutaraldehyde solution Ribeira˜o Preto School of Dentistry-USP) that were being stored buffered with 0.1 M sodium cacodylate, which was followed by in distilled water were used in this study. The teeth were rinsing in distilled water. Next, the specimens were dehy- thoroughly cleaned with a hand scaler and rubber cup/pumice drated with ethanol in increasing percentage solutions, prophylaxis and were then maintained in distilled water at namely 25% (20 min), 50% (20 min), 75% (20 min), 90% 4 8C until use. (30 min), and 100% (60 min), and dried with absorbing paper. The tooth was sectioned with the aid of a water-cooled The samples were then fixed with aluminium stubs, and their diamond saw in a sectioning machine (Minitom, Struers A/S, treated surfaces were positioned so that they would face Copenhagen, Denmark), so that ten fragments measuring upwards. Specimen coating with a gold–palladium layer was 2.0 mm  2.0 mm  1.5 mm were obtained from the occlusal conducted by means of a sputtering device (SDC 050). The surface of crowns. One of the sides of the specimen consisted surfaces were examined under the scanning electron micro- of enamel, while the other side was dentine. The enamel scope EVO (Carl Zeiss, Oberkochen, Baden-Wuttemberg, surfaces were manually finished and polished with 1200-grit Germany – Chemical Sciences Department of Faculdade de silicon carbide paper (Hermes Abrasives Ltd.) under water Cieˆncias e Letras de Ribeira˜o Preto), operating at 20 kV. A cooling, and then with 0.3-mm and 0.05-mm alumina paste on standardized series of photomicrographs was taken on cloth, which was followed by ultrasonic cleaning. representative areas, with different magnifications. A consen- After the polishing procedure, the surfaces were analysed sus was reached for selection of representative illustrations on a spectrometer for acquisition of the absorption spectrum for each group.
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