Compositional, structural, and phase changes inin vitro laser-irradiated human tooth enamel

Kuroda, Shinji; Fowler, Bruce O.

doi:10.1007/bf02405347

Cited by 143 publications

(95 citation statements)

References 29 publications

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“…[21][22][23][24] The decomposed protein and other organic matrix products melt and swell and probably lead to a blockage of the interprismatic and intraprismatic spaces, which act as ion diffusion channels, and eventually result in the decrease of calcium loss. 25 Furthermore, the enamel crystalline structure improves with the decrease of enamel solubility in acid at temperatures of 250ЊC to ϳ400ЊC.…”

Section: Discussionmentioning

confidence: 99%

Acid Resistance of Erbium-doped Yttrium Aluminum Garnet Laser–Treated and Phosphoric Acid–Etched Enamels

Kim¹,

Kwon

Kim

et al. 2006

The Angle Orthodontist

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Objective:To compare the effects of erbium-doped yttrium aluminum garnet (Er:YAG) laser ablation and of phosphoric acid etching on the in vitro acid resistance of bovine enamel. Materials and Methods: Teeth were polished to make the surface flat. The polished enamel was either etched with 37% phosphoric acid for 30 seconds or ablated with a single 33 J/cm 2 pulse from an Er:YAG laser. The control specimens were free from acid etching and laser ablation. Changes in crystal structure, dissolved mineral (calcium [Ca] and phosphorus [P]) contents, and calcium distribution in the enamel subsurface after a pH-cycling process were evaluated. Results: After laser treatment, poor crystal structures improved without forming any new phases, such as tricalcium phosphates. Among the tested enamels, dissolved mineral contents were significantly different (P Ͻ .05). Er:YAG laser-treated enamels had the lowest mineral dissolution (Ca, 13.78 ppm; P, 6.33 ppm), whereas phosphoric acid-etched enamels had the highest (Ca, 15.90 ppm; P, 7.33 ppm). The reduction rate and reduced depth of calcium content along the subsurface were lowest in Er:YAG laser-treated enamels. Conclusion:The Er:YAG laser-treated enamels are more acid resistant to acid attack than phosphoric acid-etched enamels.

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Section: Discussionmentioning

confidence: 99%

Acid Resistance of Erbium-doped Yttrium Aluminum Garnet Laser–Treated and Phosphoric Acid–Etched Enamels

Kim¹,

Kwon

Kim

et al. 2006

The Angle Orthodontist

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“…We suspect that the added layer of water aids in preventing the formation of fused areas of the non-apatitic phases and results in a more desirable surface morphology. The modified enamel within the crater are lacking the two carbonate bands located near 1400 cm À1 , indicative of the formation of the desired purer phase hydroxyapatite with fewer chemical defects [20,30,35].…”

Section: Sr-ftirmentioning

confidence: 99%

“…The mineral, hydroxyapatite, found in bone and teeth contains carbonate inclusions that render it highly susceptible to acid dissolution by organic acids generated from bacteria in dental plaque. Upon heating to temperatures in excess of 4008C, the mineral decomposes to form a new mineral phase that has increased resistance to acid dissolution [19][20][21][22]. Recent studies suggest that as a side effect of laser ablation, the walls around the periphery of a cavity preparation will be transformed through laser heating into a more acid resistant phase with an enhanced resistance to future decay [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of water augmentation during IR laser ablation of dental enamel

et al. 2002

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Background and Objectives: The mechanism of water augmentation during IR laser ablation of dental hard tissues is controversial and poorly understood. The influence of an optically thick applied water layer on the laser ablation of enamel was investigated at wavelengths in which water is a primary absorber and the magnitude of absorption varies markedly. Study Design/Materials and Methods: Q-switched and free running Er: YSGG (2.79 mm) and Er:YAG (2.94 mm), free running Ho:YAG and 9.6 mm TEA CO 2 laser systems were used to produce linear incisions in dental enamel with and without water. Synchrotron-radiation IR spectromicroscopy with the Advanced Light Source at Lawrence Berkeley National Laboratory was used to determine the chemical changes across the laser ablation profiles with a spatial resolution of 10-mm. Results: The addition of water increased the rate of ablation and produced a more desirable surface morphology during enamel ablation with all the erbium systems. Moreover, ablation was markedly more efficient for Q-switched (0.15 microsecond) versus free-running (150 microsecond) erbium laser pulses with the added water layer. Although the addition of a thick water layer reduced the rate of ablation during CO 2 laser ablation, the addition of the water removed undesirable deposits of non-apatite mineral phases from the crater surface. IR spectromicroscopy indicates that the chemical composition of the crater walls deviates markedly from that of hydroxyapatite after Er:YAG and CO 2 laser irradiation without added water. New mineral phases were resolved that have not been previously observed using conventional IR spectroscopy. There was extensive peripheral damage after irradiation with the Ho:YAG laser with and without added water without effective ablation of enamel. Conclusions: We postulate that condensed mineral phases from the plume are deposited along the crater walls after repetitive laser pulses and such non-apatitic phases interfere with subsequent laser pulses during IR laser irradiation reducing the rate and efficiency of ablation. The ablative recoil associated with the displacement and vaporization of the applied water layer removes such loosely adherent phases maintaining efficient ablation during multiple pulse irradiation.

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“…[1][2][3][4][5][6][7] Carbon dioxide laser wavelengths of 9.3 and 9.6-μm have the strongest absorption in dental hard tissues and a pulse duration in the microsecond range is well-matched to the thermal relaxation time of the absorbed laser energy near the tooth surface for those wavelengths. Moreover, other studies have indicated that topical fluoride treatments can work synergistically with the laser treatment to further enhance its inhibitory effect [8][9][10][11] .…”

Section: Introductionmentioning

confidence: 99%

Imaging laser irradiated enamel surfaces with polarization sensitive optical coherence tomography

2008

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Several studies have shown that lasers can be used to modify the surface morphology and chemical composition of tooth enamel to render it less soluble. Other studies have shown that Polarization Sensitive Optical Coherence Tomography (PS-OCT) can be used to non-destructively measure the efficacy of fluoride in inhibiting the development of artificial caries lesions. The purpose of this study was to determine if PS-OCT can be used to measure inhibition of enamel demineralization after CO 2 laser irradiation. Polarized light microscopy and microradiography were used to measure lesion severity on histological thin sections for comparison. PS-OCT was able to measure a significant reduction in the integrated reflectivity due to inhibition by the laser even though the laser modification of the enamel surface caused a slight increase in reflectivity. This study shows that the PS-OCT is well-suited for in vivo measurements of caries inhibition after laser treatments. INTRODUCTIONSeveral studies over the past thirty years have indicated that lasers can be used to thermally modify the chemical composition of dental enamel to render it more resistant to acid dissolution and potentially more resistant to dental caries. [1][2][3][4][5][6][7] Carbon dioxide laser wavelengths of 9.3 and 9.6-μm have the strongest absorption in dental hard tissues and a pulse duration in the microsecond range is well-matched to the thermal relaxation time of the absorbed laser energy near the tooth surface for those wavelengths. Moreover, other studies have indicated that topical fluoride treatments can work synergistically with the laser treatment to further enhance its inhibitory effect [8][9][10][11] . Current methods of evaluating the efficacy of chemical and thermal methods of anti-caries agents requires teeth scheduled for extraction followed by assessment with either microradiography, microhardness or polarized light microscopy. Such methods require thin sectioning of the extracted tooth, hence the need to carry out studies on teeth scheduled for extraction. One major limitation of this approach is that these studies must be limited in duration to a maximum of a few months and that natural caries lesions, particularly in occlusal surfaces, require a more extended time for development. One promising new method for the assessment of early caries lesions "in vivo" is polarization sensitive optical coherence tomography (PS-OCT), which has been * daniel.fried@ucsf.edu, 415-502-6641. Optical coherence tomography (OCT) is a noninvasive technique for creating cross-sectional images of internal biological structure 14,15 . We have demonstrated that polarizationsensitive depth-resolved reflectivity measurements can be used to measure the severity of natural and artificial lesions on extracted teeth in the laboratory [16][17][18][19][20] . The reflectance at the air-enamel interface of the tooth surface is very strong due to the high refractive index of enamel, n=1.63. It poses a particular challenge for OCT because the surface reflectivity ...

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Compositional, structural, and phase changes inin vitro laser-irradiated human tooth enamel

Cited by 143 publications

References 29 publications

Acid Resistance of Erbium-doped Yttrium Aluminum Garnet Laser–Treated and Phosphoric Acid–Etched Enamels

Acid Resistance of Erbium-doped Yttrium Aluminum Garnet Laser–Treated and Phosphoric Acid–Etched Enamels

Mechanism of water augmentation during IR laser ablation of dental enamel

Imaging laser irradiated enamel surfaces with polarization sensitive optical coherence tomography

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