Carolina Benetti

Changes in dental enamel oven heated or irradiated with Er,Cr:YSGG laser. Analysis by FTIR

This study evaluated the change that occurs in dental enamel under action of oven heating or Er,Cr:YSGG laser irradiation aiming to obtain a structure more resistant to demineralization. Enamel powder was obtained from bovine teeth. Samples were subjected to oven heating at temperatures of 200, 400, 600, 800, and 1000°C or during laser irradiation with energy densities of 7.53, 10.95, and 13.74 J/cm2. The infrared thermography was used to measure the surface temperature generated in the solid samples of enamel during lasers irradiation. The samples were analyzed by Fourier transform infrared spectroscopy (FTIR), which shows changes on enamel oven heated or laser irradiated, due to treatments, related to carbonates, adsorbed water and hydroxyl content. These compositional effects were more evident in lased samples. These changes may alter the material properties such as its solubility, and decrese of demineralization that is important for caries prevention.

Compositional and crystallographic changes on enamel when irradiated by Nd:YAG or Er,Cr:YSGG lasers and its resistance to demineralization when associated with fluoride

This study investigated the compositional and crystallographic changes on enamel when irradiated by Er,Cr:YSGG (λ=2.7μm, 8.5J/cm2) or Nd:YAG (λ=1064nm, 84.9J/cm2 associated with black coating), its resistance to demineralization when irradiation is associated with fluoride (APF-gel), and CaF2-like material formation and retention. Sample surfaces were analyzed by ATR-FTIR (4000-650cm-1, 4cm-1) resolution. Irradiation with Er,Cr:YSGG laser promoted a significant decrease on carbonate content of enamel. After Nd:YAG irradiation, it was observed a significant decrease of carbonate and amides I and II. X-ray diffraction showed that both laser irradiations promoted formation of α-tricalcium phosphate and tetracalcium phosphate, and a significant increase on the crystal growth of the enamel apatite (ANOVA, p<0.05 was used for all analysis). These changes can explain the improved resistance of enamel to demineralization observed in the second part of the study, in which 240 enamel slices were divided in 8 groups, received 4 min of professional fluoride gel (APF-gel 1.23%F-) applied before or after irradiation. After treatments, the formation of calcium fluoride (CaF2) was determined. The remaining slabs of each group were submitted to a 10-day pH-cycling model and, subsequently, enamel demineralization was evaluated by cross-sectional microhardness. Both lasers significantly reduced enamel demineralization (ANOVA, p<0.05), and the previous APF-gel application followed by laser showed the higher reduction of enamel demineralization. CaF2 formed before pH-cycling was significantly higher in groups were APF was associated with laser irradiation. After demineralization, these groups also presented higher CaF2 retention in respect to isolated treatments (only APF or only laser), suggesting its anticaries potential.

Influence of Er,Cr:YSGG Laser on CaF2‐like products formation because of professional acidulated fluoride or to domestic dentifrice application

This study evaluated the synergy of professional acidulated fluoride gel (APF) or fluoridated dentifrice application combined with Er,Cr:YSGG laser irradiation on the formation of CaF2‐like products (CaF2), in vitro. Thus, 272 bovine enamel slabs were randomly distributed among eight groups: G1: untreated enamel; G2: treated with fluoridated dentifrice (NaF, 1,100 μgF/g); G3: treated with acidulated phosphate fluoride gel (APF, 1.23% F‐); G4: irradiated with Er,Cr:YSGG laser at 8.5 J/cm2; G5 and G6: combination of pre‐irradiation with Er,Cr:YSGG followed by dentifrice or APF application, respectively; G7: combination of dentifrice application followed by Er,Cr:YSGG irradiation; G8: combination of APF application followed by Er,Cr:YSGG irradiation. After treatments, samples were evaluated by scanning electron microscopy, and the content of CaF2 was determined by an ion specific electrode. Both APF and dentifrice application promoted the formation of CaF2 on enamel, whereas Er,Cr:YSGG irradiation promoted an increase of roughness of the enamel, increasing the surface area. Laser irradiation before fluoridated products increased the content of CaF2 formed when compared to groups that APF or dentifrice were applied isolated. However, the content of CaF2 formed when irradiation was performed after APF or dentifrice was not statically significant when compared to the control groups. In conclusion, Er,Cr:YSGG laser increases the formation of CaF2 on enamel when the irradiation is performed before the application of APF or dentifrice. The association of laser with APF is most promissory for caries prevention because of the higher concentration of CaF2 formation and also the chemical changes promoted by laser irradiation demonstrated in literature. Microsc. Res. Tech. 76:704–713, 2013.

Mid-Infrared Spectroscopy Analysis of the Effects of Erbium, Chromium:Yattrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) Laser Irradiation on Bone Mineral and Organic Components

The effects of varying the energy density of a high-intensity erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the mineral and organic components of bone tissue were evaluated using Fourier transform infrared spectroscopy. Bone samples obtained from the tibias of rabbits were irradiated with five energy densities (3, 6, 8, 12, and 15 J/cm2), and the effects on the carbonate to phosphate ratio and in the organic components were compared with those of nonirradiated samples. The increased temperature during the laser irradiation was also measured using infrared thermography to relate the observed spectral changes to the laser thermal effects. The analyses of the infrared spectra suggests that the irradiation with Er,Cr:YSGG promoted changes in bone tissue in both the mineral and organic components that depend on the laser energy density, pointing to the importance of using the proper energy density in clinical procedures.

Detection of chemical changes in bone after irradiation with Er,Cr:YSGG laser

The use of laser for bone cutting can be more advantageous than the use of drill. However, for a safe clinical application, it is necessary to know the effects of laser irradiation on bone tissues. In this study, the Fourier Transform Infrared spectroscopy (FTIR) was used to verify the molecular and compositional changes promoted by laser irradiation on bone tissue. Bone slabs were obtained from rabbits tibia and analyzed using ATR-FTIR. After the initial analysis, the samples were irradiated using a pulsed Er,Cr:YSGG laser (2780nm), and analyzed one more time. In order to verify changes due to laser irradiation, the area under phosphate (1300-900cm-1), amides (1680-1200cm-1), water (3600-2400cm-1), and carbonate (around 870cm-1 and between 1600-1300cm-1) bands were calculated, and normalized by phosphate band area (1300-900cm-1). It was observed that Er,Cr:YSGG irradiation promoted a significant decrease in the content of water and amides I and III at irradiated bone, evidencing that laser procedure caused an evaporation of the organic content and changed the collagen structure, suggesting that these changes may interfere with the healing process. In this way, these changes should be considered in a clinical application of laser irradiation in surgeries.

Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopic analysis of regenerated bone

The cutting of bone is routinely required in medical procedures, especially in dental applications. In such cases, bone regeneration and new bone quality can determine the success of the treatment. This study investigated the main spectral differences of undamaged and healed bone using the ATR-FTIR spectroscopy technique. Three rabbits were submitted to a surgical procedure; a small piece of bone (3x3 mm2) was removed from both sides of their jaws using a high speed drill. After 15 days, the rabbits were euthanized and the jaws were removed. A bone slice was cut from each side of the jaw containing regions of undamaged and newly formed bone, resulting in six samples which were polished for spectroscopic comparison. The samples were analyzed by FTIR spectroscopy using a diamond ATR accessory. Spectral characteristics were compared and particular attention was paid to the proportion of phosphate to amide I bands and the width of the phosphate band. The results show that the ratio of phosphate to amide I is smaller in new bone tissue than in the undamaged bone, indicating a higher organic content in the newly formed bone. The analysis of the width of the phosphate band suggests a crystallinity difference between both tissues, since the width was higher in the new bone than in the natural bone. These results suggest that the differences observed in bone aging processes by FTIR spectroscopic can be applied to the study of healing processes.

Temperature measurement and Hsp47 immunoexpression in oral ulcers irradiated with defocused high-energy diode laser.

UNLABELLED Heat shock proteins (HSPs) are conservative protective proteins responsible for protein integrity during transcription in the cell under stress. Hsp47 is one of the most important chaperonins for collagen synthesis and release, and is up-regulated during wound repair. The aim of this study was to verify whether defocused high-energy diode laser (DDL) causes sufficient increase in local temperature to cause Hsp47 up-regulation during repair of oral ulcers. Chemically-induced ulcers in the rat tongue, and non-ulcerated tongue mucosa were irradiated using a high energy diode laser (non-contact - 4mm from surface, 500 mW, 10 Hz for 40s, energy density 80 J/cm(2), fixed ulcer area of 0.25 cm(2)). Afterwards the specimens were submitted to immunohistochemical test for Hsp47. Temperature oscillation during DDL irradiation was also measured using a thermographic camera. Irradiated specimens exhibited transient mild increase in local temperature and significant up-regulation of Hsp47 in the mucosa from the superficial region (p=0.035) to 1.7 mm deep (p=0.049). In the deepest region of the mucosa Hsp47 was up-regulated only in ulcerated specimens mainly at 24h (p=0.049) and 72 h (p=0.029) after ulcer induction. CONCLUSION DDL increases local temperature and Hsp47 expression, which may contribute to wound repair by improvement collagen synthesis and release.

Biochemical changes in cutaneous squamous cell carcinoma submitted to PDT using ATR-FTIR spectroscopy

Nonmelanoma skin cancers are the most common form of malignancy in humans. Between the traditional treatment ways, the photodynamic therapy (PDT) is a promising alternative which is minimally invasive and do not requires surgical intervention or exposure to ionizing radiation. The understanding of the cascade of effects playing role in PDT is not fully understood, so that define and understand the biochemical events caused by photodynamic effect will hopefully result in designing better PDT protocols. In this study we investigated the potential of the FTIR spectroscopy to assess the biochemical changes caused by photodynamic therapy after 10 and 20 days of treatment using 5-aminolevulinic acid (ALA) as precursor of the photosensitizer photoporphyrin IX (PpIX). The amplitude values of second derivative from vibrational modes obtained with FTIR spectroscopy showed similar behavior with the morphological features observed in histopathological analysis, which showed active lesions even 20 days after PDT. Thus, the technique has the potential to be used to complement the investigation of the main biochemical changes that photodynamic therapy promotes in tissue.

ATR-FTIR spectroscopy to study the effects of laser irradiation in bone tissue

The use of lasers on bone cut can provide a series of advantages for both the surgeon and the patient. However, for a safe and efficient application it is necessary to know the exact effects that the laser causes in the bone tissue. The aim of this work was to study the effects of Er,Cr:YSGG irradiation in bone tissue using the ATR-FTIR technique. Pieces of tibia rabbit bone were divided in six groups with three samples per group. In one of the groups the samples did not undergo any treatment; in the others the samples were laser irradiated with different energy densities. The infrared spectra acquisition was made using an ATR accessory. For a semi-quantitative analysis, the area under each band was calculated and normalized by the phosphate band area of the same spectrum. The results showed a gradual material loss as the energy density increased in the bands of water, amide I, and carbonate, amide II, amide II and collagen. This is probably caused by the temperature rise due to laser irradiation. These results are the first steps in testing the Er,Cr:YSGG laser efficacy as a cutting tool, a pivotal aspect of its consolidation in clinical procedures.

Variation on Molecular Structure, Crystallinity, and Optical Properties of Dentin Due to Nd:YAG Laser and Fluoride Aimed at Tooth Erosion Prevention

This in vitro study evaluated the compositional, crystalline, and morphological effects promoted by Nd:YAG laser on root dentin, and verified the effects of laser and topical acidulated phosphate fluoride application (APF-gel) on dentin erosion. 180 bovine dentin slabs were randomized into 4 groups (n = 45): G1–untreated, G2–APF-gel (1.23% F−, 4 min), G3–Nd:YAG (1064 nm, 84.9 J/cm2, 10 Hz), and G4–APF-gel application followed by Nd:YAG laser irradiation. The compositional, crystalline, and morphological effects promoted by treatments were investigated on five samples of each experimental group. The other samples were submitted to a 5-day, 10-day, or 15-day erosive and abrasive demineralization and remineralization cycling in order to create erosion lesions. The area and depth of lesions, as well as the optical attenuation coefficient, were assessed, and all data were statistically analysed (p < 0.05). Nd:YAG laser promoted the reduction of carbonate, the formation of tetracalcium phosphate, as well as the melting and recrystallization of the dentin surface. Laser significantly decreased the area and depth of erosion lesions and altered the optical attenuation coefficient when compared to untreated and APF-gel groups, but the association of APF-gel and laser did not promote an additional effect. Nd:YAG laser irradiation can be a promissory treatment to prevent dentin erosion and the abrasion process.