Spectroscopic characterization of enamel surfaces irradiated with Er:YAG laser

Study on the effect of crystal changes on acid resistance of erbium laser etched enamel surface

To investigate the mechanism underlying high acid resistance of enamel after erbium laser etching. Forty-five premolars were collected and assigned to three groups. A 4×4×1 mm enamel sample was prepared, the left side was the control side, the right side was the treated side, which was treated with different surface treatments, including 35% phosphoric acid etching, Er:YAG laser etching, and Er,Cr:YSGG laser etching. The hydroxyapatite crystal size on the enamel surface of the samples was observed. The contents of Ca, P, O, F, Cl, C, Mg were detected. The crystallinity of the hydroxyapatite crystal was analyzed. After erbium laser etching, the enamel surface had high hydroxyapatite crystal size, beneficial content of chemical elements and crystallinity. The morphological and composition changes of crystals in the enamel surface after erbium laser etching may be one of the crucial mechanisms underlying the enhancement of acid resistance of enamel after erbium laser etching.

Does Er,Cr:YSGG reduce the microleakage of restorations when used for cavity preparation? A systematic review and meta-analysis

Background

As the member of erbium laser family, Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) has obtained the approval for caries removal and cavity preparation by Food and Drug Administration (FDA). However, there is still controversy over the beneficial effects of Er,Cr:YSGG preparations on microleakage. The present study is the first systematic review and meta-analysis to compare the microleakage of cavities prepared by Er,Cr:YSGG lasers with that by traditional burs. In addition, the effect of acid etching on the adhesive potential of self-etch and etch-and-rinse adhesives was assessed after laser preparation.

Methods

An electronic search was performed in Pubmed, EBSCO, Embase, and the Cochrane Controlled Register of Trials (CENTRAL).

Results

Totally, 357 articles were identified. Finally, 13 met the inclusion criteria, of which 11 were selected for meta-analysis. All the included studies exhibited a moderate risk of bias. Based on the meta-analysis, no significant difference was observed between the Er,Cr:YSGG and traditional bur groups in terms of the incidence of microleakage. Self-etch adhesives, in combination with prior acid etching, showed less microleakage than those without acid etching in the laser-prepared cavities.

Conclusions

Current studies do not support the beneficial effects of Er,Cr:YSGG preparations on microleakage. Additional acid etching with self-etching adhesives is recommended after Er,Cr:YSGG preparations. Further high-quality studies are needed to draw a convincing conclusion in the future.

Chemical composition and morphology study of bovine enamel submitted to different sterilization methods

OBJECTIVES

The morphology and chemical composition of enamel submitted to different sterilization methods was studied.

METHODS

X-ray photoelectron spectroscopy (XPS), field emission gun scanning electron microscopy (FEG-SEM), and energy-dispersive X-ray spectroscopy (EDS) were performed to evaluate 50 bovine enamel specimens sterilized using four methods: microwaving (MI), gamma irradiation (GI), ethylene oxide (EO), and steam autoclave (SA). Non-sterilized specimens were used as control.

RESULTS

XPS indicated that the concentration of P (phosphorus), CO₃ (carbonate), and CO₃/P was not changed in all groups. GI produced no significant change on elemental composition. SA produced the major decrease in calcium (Ca), Ca/P ratio, and increase in N (nitrogen). MI was found to decrease Ca, Ca/P ratio and O (oxygen), and increase in C (carbon) and N. EO produced decrease in Ca and O with increased C concentration. FEG-SEM revealed surface and in-depth morphological changes on SA specimens. Minor surface alterations were observed for EO and for MI groups, and no alteration was observed on GI group. EDS indicated no difference on elemental composition of enamel bulk among groups.

CONCLUSIONS

SA produced mineral loss and morphological alterations on surface and in depth. MI and EO sterilization caused mineral loss showing only slight alteration on enamel surface. GI sterilization preserves the morphological characteristics of enamel. The sterilization methods could be classified from lower to high damage as GI < MI < EO < SA.

CLINICAL RELEVANCE

This is a comprehensive comparative study where different methods for enamel sterilization were investigated in terms of chemical changes. The results presented here may help researchers to choose the most appropriate method for their research setting and purpose.

Chemical changes associated with increased acid resistance of Er:YAG laser irradiated enamel

BACKGROUND

An increase in the acid resistance of dental enamel, as well as morphological and structural changes produced by Er:YAG laser irradiation, has been reported.

PURPOSE

To evaluate the chemical changes associated with acid resistance of enamel treated with Er:YAG laser. Methods. Forty-eight enamel samples were divided into 4 groups (n = 12). Group I (control); Groups II, III, and IV were irradiated with Er:YAG at 100 mJ (12.7 J/cm(2)), 200 mJ (25.5 J/cm(2)), and 300 mJ (38.2 J/cm(2)), respectively.

RESULTS

There were significant differences in composition of irradiated groups (with the exception of chlorine) and in the amount of calcium released.

CONCLUSIONS

Chemical changes associated with an increase in acid resistance of enamel treated with Er:YAG laser showed a clear postirradiation pattern characterized by a decrease in C at.% and an increase in O, P, and Ca at.% and no changes in Cl at.%. An increased Ca/P ratio after Er:YAG laser irradiation was associated with the use of higher laser energy densities. Chemical changes produced by acid dissolution showed a similar trend among experimental groups. Stable or increased Ca/P ratio after acid dissolution was observed in the irradiated groups, with reduction of Ca released into the acid solution.

Morphological and structural changes on human dental enamel after Er:YAG laser irradiation: AFM, SEM, and EDS evaluation

OBJECTIVE

The purpose of this study was to evaluate, using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), the morphological and structural changes of the enamel after irradiation with the Er:YAG laser.

BACKGROUND DATA

A previous study showed that subablative Er:YAG laser irradiation produced undesirable morphological changes on the enamel surface, such as craters and cracks; however, the enamel acid resistance was not increased.

METHODS

Fifty-two samples of human enamel were divided into four groups (n = 13): Group I was the control (no laser irradiation), whereas Groups II, III, and IV were irradiated with the Er:YAG 100 mJ (12.7 J/cm(2)), 100 mJ (7.5 J/cm(2)), and 150 mJ (11 J/cm(2)), respectively, at 10 Hz with water spray. The morphological changes were observed by AFM and SEM. The weight percentages (wt%) of calcium (Ca), phosphorus (P), oxygen (O) and chlorine (Cl) were determined in the resultant craters and their periphery using EDS. Kruskal-Wallis and Mann-Whitney U tests were performed (p ≤ 0.05) to distinguish significant differences among the groups.

RESULTS

The AFM images showed cracks with depths between 250 nm and 750 nm for Groups II and IV, respectively, and the widths of these cracks were 5.37 μm and 2.58 μm. The interior of the cracks showed a rough surface. The SEM micrographs revealed morphological changes. Significant differences were detected in Ca, P, and Cl in the crater and its periphery.

CONCLUSIONS

AFM observations showed triangular-shaped cracks, whereas craters and cracks were evident by SEM in all irradiated samples. It was not possible to establish a characteristic chemical pattern in the craters.

Influence of Er,Cr:YSGG Laser Treatment on Microtensile Bond Strength of Adhesives to Enamel

Er,Cr:YSGG laser irradiation produced morphological alterations on enamel, which may adversely influence the bond strength of certain adhesives, depending on their approach and composition.