Effects of Er:YAG laser irradiation and manipulation treatments on dentin components, part 2: energy-dispersive X-ray fluorescence spectrometry study.

The effects of laser etching, decontamination, and storage treatments on dentin components were studied by energy-dispersive X-ray fluorescence spectrometry (EDXRF). Thirty bovine incisors were prepared to expose the dentin surface and then divided into two main groups based upon the decontamination process and storage procedure: autoclaved (group A, n=15) or stored in aqueous thymol solution (group B, n=15). The surfaces of the dentin slices were schematically divided into four areas, with each one corresponding to a treatment subgroup. The specimens were either etched with phosphoric acid (control subgroup) or irradiated with erbium-doped yttrium-aluminum-garnet (Er:YAG) laser (subgroups: I-80 mJ, II-120 mJ, and III-180 mJ). Samples were analyzed by micro-EDXRF, yielding three spectra for each area (before and after treatment). Surface mappings covering an area of 80x60 points with steps of 20 mum were also performed on selected specimens. The amount of Ca and P in group A specimens decreased significantly (P<0.05) after the acid etching and the CaP ratio increased (P<0.001). Er:YAG laser-etching using lower laser energies did not produce significant changes in dentin components. The mapping data support the hypothesis that acid etching on dentin produced a more chemically homogeneous surface and thus a more favorable surface for the diffusion of adhesive monomers.

Effects of Er:YAG laser irradiation and manipulation treatments on dentin components, part 1: Fourier transform-Raman study.

The effects of laser etching, decontamination, and storage treatments on dentin components were studied using Fourier transform (FT)-Raman spectroscopy. Thirty bovine incisors were prepared to expose the dentin surface and then divided in two main groups based upon the decontamination process and storage procedure: autoclaved (group A, n=15) or stored in thymol aqueous solution (group B, n=15). The surfaces of the dentin slices were schematically divided into four areas, with each one corresponding to a treatment subgroup. The specimens were either etched with phosphoric acid (control subgroup) or irradiated with erbium-doped yttrium-aluminum-garnet (Er:YAG) laser (subgroups: I-80 mJ, II-120 mJ, and III-180 mJ, and total energy of 12 J). Samples were analyzed by FT-Raman spectroscopy; we collected three spectra for each area (before and after treatment). The integrated areas of five Raman peaks were calculated to yield average spectra. The areas of the peaks associated with phosphate content (P<0.001), type I collagen, and organic C-H bonds (P<0.05) were reduced significantly in group A (control). Analyses of samples irradiated with reduced laser energies did not show significant changes in the dentin components. These results suggest that thymol storage treatment is advised for in vitro study; furthermore, 12 J of Er:YAG laser energy does not affect dentin components.

Effects of Bleaching Agents Combined with Regular and Whitening Toothpastes on Surface Roughness and Mineral Content of Enamel.

OBJECTIVE: The purpose of this study was to evaluate surface roughness and changes in the composition of enamel submitted to different bleaching protocols and toothbrushing with regular and whitening toothpastes. BACKGROUND DATA: Bleaching treatment could promote morphological and chemical changes in enamel surface. METHODS: Enamel blocks were randomized into nine groups (n=10) according to the bleaching treatment (no bleaching, control group; 6% hydrogen peroxide, HP; or 10% carbamide peroxide, CP) and toothpaste used (placebo, PL; regular, R; or whitening dentifrice, W). Bleaching was performed according to manufacturers' instructions and all groups were submitted to 30,000 cycles of simulated toothbrushing with toothpaste (PL, R, or W). Mineral content evaluation and enamel roughness were evaluated initially (T1), after bleaching (T2), and after toothbrushing (T3), using an energy-dispersive micro X-ray fluorescence spectrometer and profilometry, respectively. Data were statistically analyzed with two way ANOVA, Tukey, and Dunnett tests (5%). RESULTS: Enamel surface roughness was influenced by bleaching and toothbrushing. Surface roughness increased for the groups that brushed with the placebo dentifrice (CP+PL, HP+PL, C+PL) and for the control group that brushed with whitening dentifrice (C+W). Enamel Ca/P ratio decreased after bleaching, but toothbrushing, regardless of the dentifrice used, did not reduce the enamel mineral content. CONCLUSIONS: The bleaching treatment resulted in a decrease of enamel mineral content, but the studied dentifrices did not contribute to surface mineral loss.

Erosion effects on chemical composition and morphology of dental materials and root dentin.

PURPOSE: This work aims to study the erosion on restorative materials and on surrounding dentin. Fifty root dentin samples were obtained from bovine incisors. METHODS: Twenty samples were not restored and thirty received cavity preparations. Samples were assigned to five groups: G1, G2: sound dentin (D); G3: composite resin (CR); G4: resin-modified glass-ionomer cement (RMGIC); G5: glass-ionomer cement (GIC). The samples of groups 2-5 were submitted to six cycles (demineralization-remineralization). Samples were analyzed by micro energy-dispersive X-ray fluorescence spectrometry (µ-EDXRF) and by scanning electron microscopy (SEM). RESULTS: Mineral loss was greater in G2 samples than in RMGI > CR > GIC > D (control). SEM images showed pronounced dentin demineralization in groups 2 and 4. The acid erosion has a significant effect on mineral loss (Ca and P) of root dentin without restoration. CONCLUSIONS: Composite resin had the best chemical resistance to erosion among all the materials. Fluoride contained in GIC seemed to cause some protection, however, with material degradation. Chemical interaction of tooth-colored dental materials with root dentin could be assessed by µ-EDXRF.

Energy dispersive X-ray spectrometry study of the protective effects of fluoride varnish and gel on enamel erosion.

BACKGROUND: Dental erosion is a risk factor for dental health, introduced by today's lifestyle. Topical fluoride applications in the form of varnishes and gel may lead to deposition of fluoride on enamel. PURPOSE: This in vitro study aimed to evaluate the effect of two fluoride varnishes and one fluoride gel on the dissolution of bovine enamel by acids. METHODS: Enamel samples (72) were divided (n = 8): artificial saliva (control-G1), Pepsi Twist® (G2), orange juice (G3), Duraphat® + Pepsi Twist® (G4), Duraphat® + orange juice (G5), Duofluorid® + Pepsi Twist® (G6), Duofluorid® + orange juice (G7), fluoride gel + Pepsi Twist® (G8), and fluoride gel + orange juice (G9). Fluoride gel was applied for 4 min and the varnishes were applied and removed after 6 h. The samples were submitted to six cycles (demineralization: Pepsi Twist® or orange juice, 10 min; remineralization: saliva, 1 h). Samples were analyzed by energy-dispersive X-ray fluorescence (144 line-scanning). RESULTS: The amount of Ca and P decreased significantly in the samples of G2 and G3, and the Ca/P ratio decreased in G3. Mineral gain (Ca) was greater in G9 samples than in G4 > G3 > G5 > G1, and (P) greater in G7 samples than in G9 > G4-6 > G2-3. CONCLUSIONS: The protective effect of Duofluorid® was significantly lower than fluoride gel against orange juice. The fluoride varnishes can interfere positively with the dissolution of dental enamel in the presence of acidic beverages. Fluoride gel showed the best protection level to extrinsic erosion with low costs.

FT-Raman and energy dispersive X-ray fluorescence spectrometric analyses of enamel submitted to 38% hydrogen peroxide bleaching, an acidic beverage, and simulated brushing.

OBJECTIVE: This study aimed to investigate the effects on enamel surface treated with hydrogen peroxide bleaching and acidic soft drink immersion and/or brushing with whitening dentifrices. MATERIALS AND METHODS: Fifty-six standardized enamel slabs obtained from labial surfaces of bovine incisors were used. Enamel slabs were ground flat, polished, and randomly assigned to one of seven treatment groups: (1) control, in which no treatment was performed, (2) soft drink immersion, (3) 38% hydrogen peroxide bleaching, (4) simulated toothbrushing with whitening dentifrice, (5) soft drink immersion and bleaching, (6) soft drink immersion, bleaching, and toothbrushing, and (7) bleaching and toothbrushing. The mineral concentration of enamel surfaces was determined before and after treatments by means of Fourier transform (FT)-Raman spectroscopy and energy dispersive x-ray fluorescence spectrometry (EDXRF). Data were statistically analyzed by ANOVA and Tukey test (p < 0.05). RESULTS: Raman spectroscopy results indicated that enamel mineral content decreased after all treatments except in group 1, whereas EDXRF results exhibited mineral decrease in groups 3, 4, 5, and 7. CONCLUSION: Bleaching alone or in combination with soft drink immersion and brushing decreases enamel mineral content.

Dental enamel irradiated with infrared diode laser and photoabsorbing cream: Part 1 -- FT-Raman Study.

OBJECTIVE: The aim of this FT-Raman study was to investigate laser-induced compositional changes in enamel after therapy with a low-level infrared diode laser and a photoabsorbing cream, in order to intensify the superficial light absorption before and after cariogenic challenge. BACKGROUND DATA: Dental caries remains the most prevalent disease during childhood and adolescence. Preventive modalities include the use of fluoride, reduction of dietary cariogenic refined carbohydrates, plaque removal and oral hygiene techniques, and antimicrobial prescriptions. A relatively simple and noninvasive caries preventive regimen is treating tooth enamel with laser irradiation, either alone or in combination with topical fluoride treatment, resulting in reduced enamel solubility and dissolution rates. Due to their high cost, high-powered lasers are still not widely employed in private practice in developing countries. Thus, low-power red and near-infrared lasers appear to be an appealing alternative. MATERIALS AND METHODS: Twenty-four extracted or exfoliated caries-free deciduous molars were divided into six groups: control group (no treatment; n = 8); infrared laser treatment (L; n = 8) (810 nm at 100 mW/cm(2) for 90 sec); infrared diode laser irradiation (810 nm at 100 mW/cm(2) for 90 sec) and photoabsorbing cream (IVL; n = 8); photoabsorbing cream alone (IV; n = 8); infrared diode laser irradiation (810 nm at 100 mW/cm(2) for 90 sec) and fluorinated photoabsorbing agent (IVLF; n = 8); and fluorinated photoabsorbing agent alone (IVF; n = 8). Samples were analyzed using FT-Raman spectroscopy before and after pH cycling cariogenic challenge. RESULTS: There was a significant laser-induced reduction and possible modification of the organic matrix content in enamel treated with the low-level diode laser (the L, IVL, and IVFL groups). CONCLUSION: The FT-Raman technique may be suitable for detecting compositional and structural changes occurring in mineral phases and organic phases of lased enamel under cariogenic challenge.

Dental enamel irradiated with infrared diode laser and photo-absorbing cream: part 2--EDX study.

OBJECTIVE: The effects of laser-induced compositional changes on the enamel were investigated by energy-dispersive X-ray fluorescence spectrometry (micro-EDX). After cariogenic challenge, we administered treatment of low-level infrared diode laser and a photo-absorbing cream (used to intensify the superficial light absorption). BACKGROUND DATA: Dental caries is considered the most prevalent oral disease. A simple and noninvasive caries preventive regimen is treating tooth enamel with a laser, either alone or in combination with fluoride, which reduces enamel solubility and dissolution rates. High power lasers are still not widely used in private practice. Low-power near-infrared lasers may be an alternative approach. Energy-dispersive micro-EDX is a versatile and nondestructive spectroscopic technique that allows for a qualitative and quantitative elemental analysis of inorganic enamel components, such as calcium and phosphorus. MATERIALS AND METHODS: Twenty-four extracted or exfoliated caries-free deciduous molars were divided into six groups: 1) control group (CTR-no treatment); 2) infrared laser treatment (L) (lambda = 810 nm, 100 mW/cm(2), 90 sec, 4.47 J/cm(2), 9 J); 3) infrared laser irradiation and photo-absorbing agent (CL); 4) photo-absorbing agent alone (C); 5) infrared laser irradiation and fluoridated photo-absorbing agent (FCL); and 6) fluoridated photo-absorbing agent alone (FC). Samples were analyzed using micro-EDX after two sets of treatments and pH cycling cariogenic challenges. RESULTS: The CL group showed statistically significant increases in calcium and phosphorus (wt%) compared with the CTR group. The Ca/P ratio was similar in the FCL and CTR groups. There was a significant laser-induced reduction compared with the CTR group, and there was a possible modification of the organic balance content in enamel treated with laser and cream. CONCLUSION: micro-EDX may be able to detect compositional changes in mineral phases of lased enamel under cariogenic challenge. Our results suggest that with a combined laser and photo-absorbing agent (CL) treatment, there was a possible disorganization of organic content in the tooth enamel with hydroxyapatite crystal reordering and reorganization.