Effect of Er:YAG laser on enamel acid resistance: Morphlogical and atomic spectrometry analysis

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.

The effect of the Er,Cr:YSGG laser combined casein phosphopeptide amorphous calcium phosphate for enamel remineralisation: a systematic review and meta-analysis of in vitro studies

The purpose of this systematic review and meta-analysis of in vitro studies was to evaluate the effect of the 2780 nm Er,Cr:YSGG laser combined with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) for enamel remineralisation. The electronic PubMed, Cochrane Library, Web of Science, and EMBASE databases were searched, with no language or date restrictions, up to January 2023. Two reviewers independently performed research information extraction and quality assessment. Continuous variables were analysed by standard mean difference (SMD) with a 95% confidence interval (CI). The statistical analyses were conducted using Review Manager (Version 5.4; Rev Man) and Cochrane Collaboration (2020). Finally, four trials were included for meta-analysis. According to the comprehensive results, the effect of the Er,Cr:YSGG laser combined with CPP-ACP on enamel remineralisation was significantly better than that of CPP-ACP alone: surface microhardness (SMD =  - 1.83, 95% CI: [- 2.98, - 0.69], P = 0.002); lesion depth (SMD = 6.63, 95% CI: [4.98, 8.28], P < 0.001). Under the limitations of this meta-analysis, the results show that the Er,Cr:YSGG laser combined with CPP-ACP has a better effect on enamel remineralisation than CPP-ACP alone. The combination of the Er,Cr:YSGG laser and CPP-ACP may be a feasible method to prevent and treat enamel demineralisation.

Restoration Integrity in Primary Teeth Prepared Using Erbium/Yttrium-Aluminum-Garnet Laser: A Randomized Split-Mouth Clinical Study

The most frequently used and universally accepted technique for removing caries is mechanical ablation of decayed tissues by rotating drills. New minimally invasive strategies, such as the use of lasers to perform highly controlled tissue ablation, have been introduced in dental practice. The aim of this study was to assess and compare treatment with a 2940 nm erbium/yttrium-aluminum-garnet (Er:YAG) laser versus a conventional rotary treatment during cavity preparation in children with regard to restoration integrity. In a randomized, controlled, blinded trial using a split-mouth design, 40 (9-12-year-old) children with 80 carious primary molars were included. The cavity in one quadrant was randomized to be treated conventionally using a bur, while the cavity in the other quadrant was prepared using an Er:YAG laser. At the one-year follow-up, clinical examinations were conducted to assess the integrity of the restorations according to the Ryge criteria. The data were analyzed using SPSS version 22 (IBM Inc., Chicago, IL, USA). The average age of the participants was 9.4 ± 1.29 years. Males accounted for 51.4% of the participants. The Ryge criteria showed clinical success of restorations, and there was no discernible difference between the conventional and laser intervention techniques. Over one year, no statistically significant differences in the clinical integrity based on the Ryge criteria were found following class I cavity preparation in primary teeth with either procedure.

The Effect of Erbium-Doped Yttrium Aluminum Garnet Laser in Debonding of Orthodontic Brackets: A Systematic Review of the Literature

Objective: The purpose of this review is to systematically assess the existing literature and summarize the evidence regarding the effect of erbium-doped yttrium aluminum garnet (Er:YAG) laser on enamel surface roughness and pulp health compared with the conventional orthodontic debonding techniques. Materials and methods: Following the preferred reporting items for systematic reviews (Preferred Reporting Items for Systematic Reviews and Meta-analyses) statement, the electronic database, PubMed, Scopus, Web of Science, Google scholar, and Saudi Digital Library were searched for relevant published records. Data were collected following specific keywords: "debonding" "Er:YAG laser" etc. In vitro studies, and clinical randomized- and nonrandomized-controlled studies limited to the English language and published in peer-reviewed journals were included. Results: A total of 564 articles were identified as relevant to the topic. Duplicates were excluded resulting in 382 articles, out of which 374 articles were discarded upon screening titles and abstracts. The remaining eight articles were read to their entirety and included in the current qualitative review after fulfilling the eligibility criteria. In all the included studies, a total of 480 sound posterior teeth were used to evaluate the effect of Er:YAG laser on debonding of orthodontic brackets from the enamel surface. Conclusions: Er:YAG laser debonding has demonstrated a reduced risk of enamel damage (fracture or cracks) but resulted in increased enamel surface roughness and was time-consuming for adhesive removal procedures compared with the conventional debonding methods. Further, within the applied laser settings, Er:YAG lasers have found to exhibit low thermal exhaustion in relation to the pulp. The laser source with a wavelength of 2940 nm has been used with different setting ranges (power of 2.5-5 W, energy 125-600 mJ, frequency 4-30 Hz, and pulse duration 50-350 μsec) for debonding of orthodontic brackets.

Use of the Er:YAG Laser in Conservative Dentistry: Evaluation of the Microbial Population in Carious Lesions

The aim of this study is to investigate the Erbium:Yttrio-Aluminum-Granate (Er:YAG) laser photothermal and mechanical effects on cariogenic species concentration and on the microbial load composition of therapeutic cavities, in order to evaluate the possible micro-organisms reduction and make a comparison with manual and rotating conventional therapy (CT). A clinical trial was designed, including adults with active deep carious lesions on permanent teeth who were divided into two groups, i.e., control group and intervention group treated with CT and Er:YAG therapy, respectively. Before and after any conservative treatment, two oral samples were collected using a small sterile microbrush scrubbed within the base of the dentinal cavity tissue. The percentage of reduction and the colony-forming units (CFUs) count after Er:YAG and conventional treatments were compared for total microorganisms, including Candida spp., Streptococcus spp., and Lactobacillus spp. The microbial reduction varied from 90.2% to 100% and was significantly observed for total microorganisms and Streptococcus spp. (p < 0.05). The Er:YAG laser shows the potential for clinical applications, especially with paediatric and complicated patients, thanks to its minimally invasive properties and its effect on the reduction of microbial load.

Laser Conditioning: A Preferred Option Over Conventional Acid Etching for Orthodontic Bonding

Aim:

To evaluate the demineralization resistance and the shear bond strength of enamel surfaces after erbium, chromium: yttrium–scandium–gallium-garnet (Er,Cr:YSGG) laser etching (2 W/15 Hz, 2 W/25 Hz) and to compare them with conventional acid etching for orthodontic bonding.

Materials and Methods:

A total of 60 extracted human premolars with intact enamel surface were used for this study. Demineralization Resistance was estimated using ion-coupled plasma atomic emission spectrometer (ICP-AES). Shear bond strength was evaluated using Universal Testing Machine—Instron.

Results:

Statistically significant difference ( P < .001) was found in the concentration of dissolved calcium (Ca) and phosphorus (P), with the highest mean Ca and P in the acid-etched group, followed by 2 W/15 Hz laser-etched group and least with 2 W/25 Hz laser-etched group. Maximum bond strength was found in the acid-etched group (12.06 MPa), followed by the 2 W/25 Hz laser-etched group (9.01 MPa) and 2 W/15 Hz laser-etched group (8.39 MPa). The differences were statistically significant.

Conclusions:

Laser conditioning of enamel surface revealed significant demineralization resistance with a minimal dissolution of Ca and P ions in the demineralizing solution. Moreover, optimum bond strength was obtained similar to that of acid etching; hence, Er,Cr:YSGG laser conditioning of enamel surface is preferred over the conventional phosphoric acid etching for orthodontic bonding.

Use of Laser Systems in Orthodontics

Laser systems have been used in the practice of dentistry for >35 years. Laser systems have so many advantages, such as increase patient cooperation, reduce the duration of treatment time, and help the orthodontists to enhance the design of a patient's smile to improve treatment efficacy, and the success of orthodontic treatments can also be improved by diminishing the orthodontic pain and the discomfort of the patients. Laser systems also have some disadvantages, such as cost, large space requirements for some types, and high-risk potential for physician and patient if not used at the appropriate wavelength and power density, that is why before incorporating lasers into clinical practice, the physician must fully understand the basic science, safety protocol, and risks associated with them. Lasers have many applications in orthodontics, including accelerating tooth movement, bonding and debonding processes, pain reduction, bone regeneration, etching procedures, increase mini-implant stability, soft tissue procedures (gingivectomy, frenectomy, operculectomy, papilla flattening, uncovering temporary anchorage devices, ablation of aphthous ulcerations, and exposure of impacted teeth), fiberotomy, scanning systems, and welding procedures. In reviewing the literature on the use of laser in orthodontics, many studies have been conducted. The purpose of the present study was to give information about the use of laser in the field of orthodontics, the effects of laser during the postoperative period, and its advantages and disadvantages and to provide general information about the requirements to be considered during the use of laser.

Effects of Er:YAG Laser Treatment on the Mineral Content and Morphology of Primary Tooth Enamel

Objective: The aim of this study was to evaluate the mineral content and morphology of primary tooth enamel prepared using an Er:YAG laser at different power settings. Materials and methods: The buccal surfaces of 45 noncarious primary molars were assessed in this study. The surfaces were cleaned and the teeth were randomly divided into nine groups (n = 5 each) to evaluate the effects of Er:YAG laser treatment at different energy levels: 200 mJ, 2 Hz; 200 mJ, 3 Hz; 200 mJ, 10 Hz; 250 mJ, 2 Hz; 250 mJ, 3 Hz; 250 mJ, 10 Hz; 300 mJ, 2 Hz; 300 mJ, 3 Hz; and 300 mJ, 10 Hz. The mean percentage weight (wt%) of calcium (Ca), phosphorous (P), fluoride (F), magnesium (Mg), potassium (K), and sodium (Na) in the primary tooth enamel was calculated for each group using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy before and after laser application. The enamel morphology was also evaluated using SEM. The obtained data were statistically analyzed by one-way analysis of variance and Tukey's honest significant difference test. Results: The mean wt% of Ca, P, and F in the enamel exhibited a significant change after laser treatment (p < 0.05); the wt% of Mg, K, and Na remained unchanged (p > 0.05). There was no association between the power setting of the laser and changes in the wt% of minerals in the enamel (p > 0.05). SEM showed that enamel irradiated at different energy levels exhibited a characteristic lava flow appearance, and more surface irregularities were observed with the 250-mJ setting than with the 200-mJ setting. Conclusions: Our findings suggest that the mineral content and morphology of the enamel of primary teeth are affected by Er:YAG laser irradiation.

Adhesion of Streptococcus mutans and Streptococcus sanguinis on Er:YAG Laser-Irradiated Dental Enamel: Effect of Surface Roughness

Objective: To determine surface roughness caused by Er:YAG laser irradiation and its effect on the increase in bacterial adhesion. Background: Er:YAG laser was proposed as a strategic device to reduce caries by its ability to generate chemical and structural changes in tooth enamel; in turn, it produces undesirable effects on the tooth surface that could increase its roughness and allow a greater accumulation of microorganisms. Methods: Eighty-four samples of human enamel were divided into seven groups (n = 12): G1_control (no laser irradiation); G2_100/H₂O, G3_200/H₂O, and G4_300/H₂O were irradiated with Er:YAG laser (12.7, 25.5, and 38.2 J/cm², respectively) under water irrigation. In addition, G5_100, G6_200, and G7_300 were irradiated with the energy densities described above and no water irrigation. Surface roughness measurements were recorded before and after treatment using a profilometer. Afterward, three samples per group were incubated in a microorganism suspension for the tetrazolium salt (XTT) assay. Biofilm morphology was observed using scanning electron microscopy and confocal laser scanning microscope. One-way analysis of variance and t-tests were performed for statistical analysis (p < 0.05). Results: There were no statistically significant differences in roughness values in the G5_100 group before and after treatment, but there were statistically significant differences observed in the other groups evaluated (p < 0.05). No significant differences in adhesion of both strains were detected in irradiated groups compared with G1_control. Conclusions: The increase in roughness on dental enamel surfaces was proportional to the irradiation conditions. However, the increase in surface roughness caused by Er:YAG laser irradiation did not affect Streptococcus mutans and S. sanguinis adhesion.

Non-contact profilometry of eroded and abraded enamel irradiated with an Er:YAG laser

Literature has reported positive results regarding the use of lasers in the control of erosive lesions; however, evaluating whether they are effective in the control of the progression of erosive/abrasive lesions is important.

Influence of multi-wavelength laser irradiation of enamel and dentin surfaces at 0.355, 2.94, and 9.4 μm on surface morphology, permeability, and acid resistance

OBJECTIVE

Ultraviolet (UV) and infrared (IR) lasers can be used to specifically target protein, water, and mineral, respectively, in dental hard tissues to produce varying changes in surface morphology, permeability, reflectivity, and acid resistance. The purpose of this study was to explore the influence of laser irradiation and topical fluoride application on the surface morphology, permeability, reflectivity, and acid resistance of enamel and dentin to shed light on the mechanism of interaction and develop more effective treatments.

METHODS

Twelve bovine enamel surfaces and twelve bovine dentin surfaces were irradiated with various combinations of lasers operating at 0.355 (Freq.-tripled Nd:YAG (UV) laser), 2.94 (Er:YAG laser), and 9.4 μm (CO₂ laser), and surfaces were exposed to an acidulated phosphate fluoride gel and an acid challenge. Changes in the surface morphology, acid resistance, and permeability were measured using digital microscopy, polarized light microscopy, near-IR reflectance, fluorescence, polarization sensitive-optical coherence tomography (PS-OCT), and surface dehydration rate measurements.

RESULTS

Different laser treatments dramatically influenced the surface morphology and permeability of both enamel and dentin. CO₂ laser irradiation melted tooth surfaces. Er:YAG and UV lasers, while not melting tooth surfaces, showed markedly different surface roughness. Er:YAG irradiation led to significantly rougher enamel and dentin surfaces and led to higher permeability. There were significant differences in acid resistance among the various treatment groups.

CONCLUSION

Surface dehydration measurements showed significant changes in permeability after laser treatments, application of fluoride and after exposure to demineralization. CO₂ laser irradiation was most effective in inhibiting demineralization on enamel while topical fluoride was most effective for dentin surfaces. Lasers Surg. Med. 49:913-927, 2017. © 2017 Wiley Periodicals, Inc.

Er:YAG pre-treatment for bonding of orthodontic bracket: 1 year of in vitro treatment

Objective

The aim of this study was to evaluate in vitro bond strength of metal brackets bonded with: total etch, total etch with erbium: yttrium aluminum garnet laser (Er:YAG) and self-etching adhesive systems, submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment.

Materials and methods

For the study, 80 bovine incisors were randomly divided into 3 experimental groups (n=16 each): XT- acid etching + Transbond XT, XT/Er:YAG- Transbond XT associated with Er:YAG laser irradiation (λ=2.94 μm, 60 mJ, 10 Hz) and SEP- Transbond Plus Self Etching Primer. Samples were submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment. Afterward, the shear bond strength test was performed in a universal test machine at a speed of 0.5mm/min. Samples were evaluated under a stereomicroscope and by scanning electron microscopy for analysis of enamel surface and adhesive remnant index. Data were analyzed using Kruskal–Wallis and Mann–Whitney (with Bonferroni correction) statistical tests.

Results

Statistically significant difference was observed between the groups studied (p<0.05). Groups XT and SEP showed the highest bond strength values, without statistical difference between them, while group XT/Er:YAG showed reduction in bond strength values. Higher frequency of adhesive failures between enamel and adhesive system was verified for groups XT and XT/Er:YAG.

Conclusion

The conventional (XT) and self-etching (SEP) adhesive systems showed mean bond strength values, similar between them, whereas the previous application of Er:YAG laser promoted the lowest bond strength values.

Effect of Metalloproteinase Inhibitors on the Microtensile Bond Strength of Composite Resin to Er:YAG Laser-Irradiated Dentin

Abstract This study evaluated the effect of matrix metalloproteinase (MMP) inhibitors - 2% (CHX) and sodium fluoride (NaF) (5000 ppm) - on microtensile bond strength (μTBS) of composite resin to Er:YAG laser-irradiated dentin after chemical degradation of the bond interface. The occlusal surface of forty sound human molars was removed exposing the dentin surface (n=10), which was polished, irradiated with Er:YAG laser, acid etched and dried. Twenty specimens were rewetted with 2% CHX (control group) and 20 were rewetted with NaF (5000 ppm). The adhesive system was applied and a 4-mm-high plateau of light-cured composite resin was built up. Resin-dentin sticks were obtained with a rectangular cross-sectional area (0.8-1 mm2) and were either stored in water at 37 ?#61616;C for 24 h or submitted to chemical degradation. For chemical degradation, they were immersed in 10% NaOCl aqueous solution for 5 h and rinsed in water for 1 h. The sticks were submitted to microtensile test in a mechanical testing machine at 0.5 mm/min until failure. Fracture pattern was analyzed using SEM. μTBS values were calculated in MPa and submitted to analysis of variance ANOVA (α=0.05). The variance analysis showed that the 'MMP inhibitor' and 'degradation' factors (p=0.214 and p=0.093, respectively) and interaction between the factors were not statistically significant (p=0.143). Mixed failure predominated in all groups. In conclusion, the 2% CHX and NaF 5000 ppm presented similar μTBS of composite resin to laser-irradiated dentin before and after chemical degradation

Structural and Morphological Changes in Human Dentin after Ablative and Subablative Er:YAG Laser Irradiation

INTRODUCTION

This study investigated the influence of Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) laser on microhardness, chemical composition and subsurface morphology of dentin cavity walls.

METHODS

Forty sound human premolars were selected and randomly assigned into four groups. Class V cavities were prepared either with an Er:YAG laser (groups 1 and 2; 15 Hz, 250 mJ for enamel, 10 Hz, 200 mJ for dentin) or with a high speed handpiece (groups 3 and 4). The specimens in groups 1 and 3 served as the control, whereas those in groups 2 and 4 were exposed to subablative laser irradiation following cavity preparation (10 Hz, 50 mJ). After bisecting the specimens, one half was subjected to microhardness assessment and the other half was evaluated by SEM-EDS analysis.

RESULTS

Microhardness was significantly greater in the specimens prepared by both ablative and subablative laser irradiation (group 2) than that of the bur-prepared cavities (groups 3 and 4) (P < 0.05). The quantity of calcium ion was significantly greater in cavities prepared by the Er:YAG laser (groups 1 and 2) compared to that of the bur cavities (groups 3 and 4) (P < 0.05). Subablative irradiation improved microhardness and weight percentage of calcium ion in both laser and bur cavities, but the difference was not significant compared to that of the relevant control group (P > 0.05).

CONCLUSION

Cavity preparation with an Er:YAG laser could be considered as an alternative to the conventional method of drilling, as it enhances the mechanical and compositional properties of lased dentin, especially when combined by subablative irradiation.

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel

OBJECTIVE

This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel.

METHODS

Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM).

RESULTS

Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05).

CONCLUSIONS

The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz.

CO2 laser and topical fluoride therapy in the control of caries lesions on demineralized primary enamel

This study evaluated the effect of CO₂ laser irradiation and topical fluoride therapy in the control of caries progression on primary teeth enamel. 30 fragments (3 × 3 × 2 mm) from primary canines were submitted to an initial cariogenic challenge that consisted of immersion on demineralizing solution for 3 hours and remineralizing solution for 21 hours for 5 days. Fragments were randomly assigned into three groups (n = 10): L: CO₂ laser (λ = 10.6 μm), APF: 1.23% acidulated phosphate fluoride, and C: no treatment (control). CO₂ laser was applied with 0.5 W power and 0.44 J/cm² energy density. Fluoride application was performed with 0.1 g for 1 minute. Cariogenic challenge was conducted for 5 days following protocol previously described. Subsurface Knoop microhardness was measured at 30 μm from the edge. Obtained data were subjected to analysis the variance (ANOVA) and Duncan test with significance of 5%. It was found that the L group showed greater control of deciduous enamel demineralization and were similar to those of APF group, while being statistically different from C group (P ≤ 0.05) that showed the lowest microhardness values. It was concluded that CO₂ laser can be an additional resource in caries control progression on primary teeth enamel.

Influence of cavity preparation with Er,Cr:YSGG laser and restorative materials on in situ secondary caries development

OBJECTIVE

The aim of this study was to evaluate the influence of cavity preparation and restorative materials containing fluorides in the prevention of secondary caries lesion development in situ.

METHODS

A total of 120 blocks obtained from human teeth were divided into two groups and standardized cavities were prepared using diamond burs (DB) or Er,Cr:YSGG-laser [20 Hz, 4.0W, 55% water, 65% air (LA)]. They were divided into three subgroups according to the restorative material (n=20): glass-ionomer cement (GI), resin modified glass-ionomer (RM) or composite resin (CR). Blocks were fixed in palatal intra-oral appliances worn in situ by 20 human volunteers, who dropped 20% sucrose solution eight times daily. After 21 days, blocks were removed and restorations were cross-sectioned to evaluate microhardness [Knoop hardness number (KHN)] underneath enamel surface from 30 to 200 μm. Factors "cavity preparation," "restorative materials," and "depth" were evaluated by three way ANOVA, followed by Tukey test (p<0.05).

RESULTS

The results showed lower microhardness in cavities prepared with DB than in cavities prepared with LA. At 30 μm, there were no statistical significant differences with regard to "cavity preparation" or "restorative materials" factors. In depth evaluation, the enamel microhardness progressively increased as a function of depth for the GI groups. In the groups prepared with LA at 60 μm/90 μm, there were no significant differences between GI and RM materials, whose microhardnesses were significantly higher than that of CR.

CONCLUSIONS

Cavity preparation using Er,Cr:YSGG laser increases caries resistance of enamel walls, and reduce caries lesion depth development regardless of fluoride presence in the restorative material. CR showed higher caries lesion development than GI, and RM showed intermediate results.

Effect of erbium, chromium: yttrium, scandium, gallium, garnet laser and casein phosphopeptide-amorphous calcium phosphate on surface micro-hardness of primary tooth enamel

Objective:

The aim was to evaluate the effect of Er, Cr: YSGG laser and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on surface micro-hardness of primary tooth enamel.

Materials and Methods:

A total of 30 freshly extracted caries free primary anterior teeth were cleaned and stored in 1% thymol. Teeth were embedded in acrylic resin such that only their buccal surfaces were exposed and were divided into four groups. Group I: Five intact teeth (negative control). The remaining 25 teeth were immersed for 30 min in 1% citric acid for demineralization. Group II: Five demineralized teeth (positive control), Group III: CPP-ACP (GC tooth mousse-GC International, Itabashi-Ku, Tokyo, Japan) application and Group IV: Etching using Er, Cr: YSGG laser + CPP-ACP application. Groups III and IV were subjected to pH cycling for 5 days. Surface micro-hardness of all the teeth was measured using Brinell hardness tester (Fuel Instruments and Engineers Pvt. Ltd.). Data were analyzed using ANOVA.

Results:

Mean surface micro-hardness of Groups I and II were 177.43 kgf/mm² and 164.86 kgf/mm², respectively. Group IV showed a higher mean surface micro-hardness (230.68 kgf/mm²) compared with that of Group III (190.28 kgf/mm²). In comparison to all other groups, laser etching prior to CPP-ACP application increased surface micro-hardness significantly (P < 0.001).

Conclusion:

Laser irradiation of primary teeth followed by CPP-ACP application increased surface micro-hardness of enamel.

In vitro effects of two topical varnish materials and Er:YAG laser irradiation on enamel demineralization around orthodontic brackets

The aim of this in vitro was to evaluate the effects of tricalcium phosphate (TCP) and amorphous calcium phosphate (ACP) containing varnish materials and Er:YAG laser irradiation on enamel demineralization around orthodontic brackets. Forty extracted human premolar teeth were randomly divided into four treatment groups (i.e., 10 in each group): (1) 5% NaF-ACP varnish, (2) 5% NaF-TCP varnish, (3) Er:YAG laser, and (4) control (no treatment). Er:YAG laser was operated at a wavelength of 2.94 μm and the energy output was 80 mJ per pulse; a pulse duration of 200 μsec and and a frequency of 2 Hz were used with water cooling. All samples were then put into pH cycles. Surface microhardness values and representative SEM images were assessed. Surface microhardness values were evaluated using Kruskal-Wallis and Mann-Whitney U tests. The results revealed that demineralization was significantly lower in the TCP and ACP varnish groups, whereas mean surface microhardness values of the TCP varnish were found higher than the ACP (P < 0.05). TCP and ACP varnish materials were found effective for reducing enamel demineralization around orthodontic brackets. Use of Er:YAG laser irradiation as described in this study for inhibition of demineralization was found not satisfactory.

Er:YAG laser irradiation to control the progression of enamel erosion: an in situ study

This in situ study evaluated the effect of Er:YAG laser irradiation in controlling the progression of enamel erosion-like lesions. Fifty-six enamel slabs (330 KHN ± 10 %) with one fourth of the surface covered with resin composite (control area) were submitted to initial erosion-like lesion formation with citric acid. The slabs were divided into two groups: irradiated with Er:YAG laser and non-irradiated. Fourteen volunteers used an intraoral palatal appliance containing two slabs, in two phases of 5 days each. During the intraoral phase, in a crossed-over design, half of the volunteers immersed the appliance in citric acid while the other half used deionized water, both for 5 min, three times per day. Enamel wear was determined by an optical 3D profilometer. ANOVA revealed that when deionized water was used as immersion solution during the intraoral phase, lower values of wear were showed when compared with the groups that were eroded with citric acid, whether irradiated or non-irradiated with Er:YAG laser. When erosion with citric acid was performed, Er:YAG laser was not able to reduce enamel wear. Small changes on enamel surface were observed when it was irradiated with Er:YAG laser. It may be concluded that Er:YAG laser irradiation did not reduce the progression of erosive lesions on enamel submitted to in situ erosion with citric acid.

Morphological changes produced by acid dissolution in Er:YAG laser irradiated dental enamel

Several scientific reports have shown the effects of Er:YAG laser irradiation on enamel morphology. However, there is lack of information regarding the morphological alterations produced by the acid attack on the irradiated surfaces. The aim of this study was to evaluate the morphological changes produced by acid dissolution in Er:YAG laser irradiated dental enamel. Forty-eight enamel samples were divided into four groups (n = 12). GI (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, at 10 Hz without water irrigation. Enamel morphology was evaluated before-irradiation, after-irradiation, and after-acid dissolution, by scanning electron microscopy (SEM). Sample coating was avoided and SEM analysis was performed in a low-vacuum mode. To facilitate the location of the assessment area, a reference point was marked. Morphological changes produced by acid dissolution of irradiated enamel were observed, specifically on laser-induced undesired effects. These morphological changes were from mild to severe, depending on the presence of after-irradiation undesired effects.

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.

Comparison of Marginal Microleakage of Glass Ionomer Restorations in Primary Molars Prepared by Chemo-mechanical Caries Removal (CMCR), Erbium: Yttrium Aluminum-Garnet (Er:YAG) Laser and Atraumatic Restorative Technique (ART)

Background: It is important to emphasize that the aspects of pretreatment techniques, as well as the composition and mechanism of adhesion, may decisively influence the effectiveness of the restorative materials in sealing cavity margins and preventing marginal leakage.

Aims: This study assessed the in vitro influence of surface preparation techniques on the microleakage of glass ionomer restorations in primary teeth.

Materials and methods: The study groups were divided into three different techniques: (1) The chemomechanical caries removal (CMCR) method using the Apacaries gel, (2) the erbium:yttrium aluminum-garnet (Er:YAG) laser method and (3) the atraumatic restorative technique (ART). The teeth restored with a glass ionomer restorative material (Fuji IX GP capsule, GC Corporation, Tokyo, Japan). The dye penetration was measured in micrometers using a polarized light microscope and specific computer software.

Results: The results showed that the mean microleakage level after was lowest with the CMCR method using Apacaries gel and highest with the Er:YAG laser. There was a statistically significant difference regarding the mean microleakage level between the group with the CMCR method using Apacaries gel and the Er:YAG laser.

Conclusion: Marginal leakage was significantly higher with preparations made using the Er:YAG laser than with the CMCR method using Apacaries gel and spoon excavator (p < 0.05).

How to cite this article: Juntavee A, Juntavee N, Peerapattana J, Nualkaew N, Sutthisawat S. Comparison of Marginal Microleakage of Glass Ionomer Restorations in Primary Molars Prepared by Chemomechanical Caries Removal (CMCR), Erbium: Yttrium Aluminum-Garnet (Er:YAG) Laser and Atraumatic Restorative Technique (ART). Int J Clin Pediatr Dent 2013;6(2):75-79.

Orthodontic bonding to acid- or laser-etched prebleached enamel

OBJECTIVE

Bonding forces of brackets to enamel surfaces may be affected by the procedures used for bleaching and enamel etching. The aim of this study was to investigate the bonding strength of orthodontic brackets to laser-etched surfaces of bleached teeth.

METHODS

In a nonbleached control group, acid etching (group A) or Er:YAG laser application (group B) was performed prior to bracket bonding (n = 13 in each group). Similar surface treatments were performed at 1 day (groups C and D; n = 13 in each subgroup) or at 3 weeks (groups E and F; n = 13 in each subgroup) after 38% hydrogen peroxide bleaching in another set of teeth. The specimens were debonded after thermocycling.

RESULTS

Laser etching of bleached teeth resulted in clinically unacceptable low bonding strength. In the case of acid-etched teeth, waiting for 3 weeks before attachment of brackets to the bleached surfaces resulted in similar, but not identical, bond strength values as those obtained with nonbleached surfaces. However, in the laser-etched groups, the bonding strength after 3 weeks was the same as that for the nonbleached group.

CONCLUSIONS

When teeth bleached with 38% hydrogen peroxide are meant to be bonded immediately, acid etching is preferable.

Influence of different pulse durations of Er:YAG laser based on variable square pulse technology on microtensile bond strength of a self-etch adhesive to dentin

OBJECTIVE

The aim of the study was to evaluate the microtensile bond strength of a composite resin to dentin modified with three different pulse durations of the Er:YAG laser based on variable square pulse technology and with one self-etch adhesive.

MATERIALS AND METHODS

The entire occlusal enamel was removed to obtain flat dentin surface for 48 human molar teeth. The teeth were randomly divided into four experimental groups (n=12 per group), according to the pretreatment of dentin: (1) control group; (2) super short pulse (SSP) (50 μsec); (3) medium short pulse (MSP) (100 μsec); and (4) short pulse (SP) (300 μsec) with Er:YAG laser. The energy of the laser used was 80 mJ with average power of 0.8 W. The microtensile bond strength was tested with a universal testing machine. Two specimens from each experimental group were subjected to scanning electron microscopic (SEM) examination, to observe the irradiated surface.

RESULTS

Dentin surface treated with SSP showed significantly lower microtensile bond strength values (24±9.8 MPa) in comparison with the control group and SP group (35.3±12.8 and 32.9±10.7 MPa, respectively), (p<0.05). The MSP and SP groups did not show any statistically significant difference in microtensile bond strength in comparsion with the control group (p>0.05).

CONCLUSIONS

The use of SP and MSP of the Er:YAG laser with one step self-etch adhesive does not impair or improve the microtensile bond strength in dentin, whereas SSP may not be suitable for dentin surface treatment prior to bonding procedures.

Influence of laser irradiation on pits and fissures: an in situ study

OBJECTIVE

The aim of this in situ study was to analyze the influence of the Er:YAG, Nd:YAG, and CO(2) lasers on the enamel acid resistance of pits and fissures.

BACKGROUND DATA

The laser tissue interaction has been studied as a method of preventing occlusal caries.

METHODS

Thirteen volunteers wore palatal acrylic appliances containing human occlusal enamel blocks that were divided into four groups (G1, control; G2, Er:YAG; G3, Nd:YAG; G4, CO(2)). Each palatal acrylic appliance was used in the four studied groups and was used for 14 consecutive days. A sucrose solution was applied to the specimens six times per day. The specimens were then sectioned in half, and a microhardness test was applied. The other halves were analyzed using polarized light microscopy to measure the caries-like lesion areas, and a morphological analysis was conducted using a scanning electron microscope (SEM).

RESULTS

For the statistical analysis of the data obtained from the microhardness test (Knoop hardness number. [KHN]) (α=5%), Fisher's exact test was performed, and the group means were as follows: G1, 247±71; G2, 258±70; G3, 272±73; and G4, 298±56. The results demonstrated that the control group was significantly different from G3 and G4, which presented higher microhardness values. The Wilcoxon signed-rank test was used to analyze the data obtained from the caries-lesion area measurements (mm(2)) (α=5%) (G1, 0.01±1.08; G2, 0.13±0.18; G3, 0.05±0.17; and G4, 0.09±0.22). The results no showed significant differences among the groups in this analysis.

CONCLUSIONS

Based on the results from the present study, it may be concluded that the CO(2) and Nd:YAG lasers increased the enamel acid resistance in pits and fissures.

MATHEMATICAL MODELING FOR THE PREDICTION AND IMPROVEMENT OF TOOTH THERMAL PAIN: A REVIEW

Tooth pain, especially tooth thermal pain, is one of the most important symptoms and signs in dental clinic and daily life. As a special sensation, pain has been studied extensively in both clinic and experimental research aimed at reducing or eliminating the possible negative effects of pain. Unfortunately, the full underlying mechanism of pain is still unclear, because the pain could be influenced by many factors, including physiological, psychological, physical, chemical, and biological factors and so on. Besides, most studies on pain mechanisms in the literature are based on skin pain sensation and only few are based on tooth pain. In this paper, we present a comprehensive review on both neurophysiology of tooth pain mechanism, and corresponding thermal, mechanical, and thermomechanical behaviors of teeth. We also describe a multiscale modeling approach for quantifying tooth thermal pain by integrating the mathematic methods of engineering into the neuroscience. The mathematical model of tooth thermal pain will enable better understanding of thermal pain mechanism and optimization of existing diagnosis and treatment in dental clinic.

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.

Effects of Er:YAG laser irradiation on the microtensile bond strength to bleached enamel

OBJECTIVE

The objective of this study was to evaluate the influence of different Er:YAG laser (λ = 2.94  μm) energy parameters on the microtensile bond strength (μTBS) and superficial morphology of bovine enamel bleached with 16% carbamide peroxide.

BACKGROUND

Laser irradiation could improve adhesion to bleached enamel surfaces.

METHODS

Sixty bovine enamel blocks (7 × 3 × 3  mm(3)) were randomly assigned to six groups according to enamel preparation procedures (n = 10): G1-bleaching and Er:YAG laser irradiation with 25.52  J/cm(2) (laser A, LA); G2-bleaching and Er:YAG laser irradiation with 4.42 J/cm(2) (laser B, LB); G3-bleaching; G4-Er:YAG laser irradiation with 25.52  J/cm(2); G5-Er:YAG laser irradiation with 4.42 J/cm(2); G6-control, no treatment. G1 to G3 were bleached for 6  h during 21 days. Afterwards, enamel surfaces in all groups were slightly abraded with 600-grit SiC papers and G1, G2, G4 and G5 were irradiated according to each protocol. Enamel blocks were then restored with an etch-and-rinse adhesive system and a 4-mm thick composite buildup was made in two increments (n = 9). After 24  h, restored blocks were serially sectioned with a cross-section area of ∼1  mm(2) at the bonded interface and tested in tension in a universal testing machine (1  mm/min). Failure mode was determined at a magnification of x100 using a stereomicroscope. One treated block of each group was selected for scanning electron microscopy (SEM) analysis. μTBS data were analyzed by two-way ANOVA and no statistical differences were observed among groups.

RESULTS

Mean bond strengths (SD) in MPa were: G1-30.4(6.2); G2-27.9(8.5); G3-32.3(3.9); G4-23.7(5.8); G5-29.3(6.0); G6-29.1(6.1). A large number of adhesive failures was recorded for bleached and irradiated enamel surfaces.

CONCLUSIONS

Bleached enamel surfaces μTBS values were not significantly different from those of unbleached enamel. Even though Er:YAG laser irradiation with both parameters had no influence on μTBS for bleached and unbleached enamel, SEM analysis revealed that Er:YAG laser irradiation with 25.52  J/cm(2) should not be recommended, as enamel ablation was observed, whereas irradiation with 4.42 J/cm(2) did not promote any remarkable changes on enamel surface.

Micromorphology of resin-dentin interfaces using one-bottle etch&rinse and self-etching adhesive systems on laser-treated dentin surfaces: a confocal laser scanning microscope analysis

BACKGROUND AND OBJECTIVES

This study evaluated the hybrid layer (HL) morphology created by three adhesive systems (AS) on dentin surfaces treated with Er:YAG laser using two irradiation parameters.

STUDY DESIGN

Occlusal flat dentin surfaces of 36 human third molars were assigned into nine groups (n = 4) according to the following ASs: one bottle etch&rinse Single Bond Plus (3M ESPE), two-step Clearfil Protect Bond (Kuraray), and all-in-one S(3) Bond (Kuraray) self-etching, which were labeled with rhodamine B or fluorescein isothiocyanate-dextran and were applied to dentin surfaces that were irradiated with Er:YAG laser at either 120 (38.7 J/cm(2)) or 200 mJ/pulse (64.5 J/cm(2)), or were applied to untreated dentin surfaces (control group). The ASs were light-activated following MI and the bonded surfaces were restored with resin composite Z250 (3M ESPE). After 24 hours of storage in vegetable oil, the restored teeth were vertically, serially sectioned into 1-mm thick slabs, which had the adhesive interfaces analyzed with confocal laser microscope (CLSM-LSM 510 Meta). CLSM images were recorded in the fluorescent mode from three different regions along each bonded interface.

RESULTS

Non-uniform HL was created on laser-irradiated dentin surfaces regardless of laser irradiation protocol for all AS, while regular and uniform HL was observed in the control groups. "Stretch mark"-like red lines were found within the HL as a result of resin infiltration into dentin microfissures, which were predominantly observed in 200 mJ/pulse groups regardless of AS. Poor resin infiltration into peritubular dentin was observed in most regions of adhesive interfaces created by all ASs on laser-irradiated dentin, resulting in thin resin tags with neither funnel-shaped morphology nor lateral resin projections.

CONCLUSION

Laser irradiation of dentin surfaces at 120 or 200 mJ/pulse resulted in morphological changes in HL and resin tags for all ASs evaluated in the study.

Influence of the irradiation distance and the use of cooling to increase enamel-acid resistance with Er:YAG laser

OBJECTIVES

The aim of this study was to assess the influence of irradiation distance and the use of cooling in the Er:YAG laser efficacy in preventing enamel demineralization.

METHODS

84 enamel blocks were randomly assigned to seven groups (n=12): G1: control group - no treatment, G2-G7: experimental groups treated with Er:YAG laser (80mJ/2Hz) at different irradiation distances with or without cooling: G2: 4mm/2mL; G3: 4mm/no cooling; G4: 8mm/2mL; G5: 8mm/no cooling; G6: 16mm/2mL; G7: 16mm/no cooling. The samples were submitted to an in vitro pH cycles for 14 days. Next, the specimens were sectioned in sections of 80-100microm in thickness and the demineralization patterns of prepared slices were assessed using a polarized light microscope. Three samples from each group were analyzed with scanning electronic microscopy. Analysis of variance and the Fisher test were performed for the statistical analysis of the data obtained from the caries-lesion-depth measurements (CLDM) (alpha=5%).

RESULTS

The control group (CLDM=0.67mm) was statistically different from group 2 (CLDM=0.42mm), which presented a smaller lesion depth, and group 6 (0.91mm), which presented a greater lesion depth. The results of groups 3 (CLDM=0.74mm), 4 (CLDM=0.70mm), 5 (CLDM=0.67mm) and 7 (CLDM=0.89mm) presented statistical similarity. The scanning electronic microscopy analysis showed ablation areas in the samples from groups 4, 5, 6 and 7, and a slightly demineralized area in group 2.

CONCLUSIONS

It was possible to conclude that Er:YAG laser was efficient in preventing enamel demineralization at a 4-mm irradiation distance using cooling.

The effects of lasers and fluoride on the acid resistance of decalcified human enamel

OBJECTIVE

In order to preserve the maximum amount of healthy enamel and increase the acid resistance of decalcified enamel, a CO(2) laser, an Nd:YAG laser, and acidulated phosphate fluoride (APF) were used to treat incipient carious lesions, then their effects were compared.

MATERIALS AND METHODS

One hundred and sixty samples of human caries-free premolars were immersed in pH-cycling solution (pH = 5) for 2 d for decalcified lesion formation. Then the tooth samples were randomly divided into eight groups and the lesions were treated using the different modalities: a control group, an APF only group, an APF = Nd:YAG laser group, and APF = CO(2) laser group, an Nd:YAG laser = APF group, a CO(2) laser = APF group, a CO(2) laser only group, and an Nd:YAG laser only group. The energy density setting for the two types of lasers was 83.33 J/cm(2). After treatment the tooth samples were immersed in pH-cycling solution again for 2 d for acid challenge. As for the acid-resistance evaluation, the calcium concentration dissolved from the enamel surface was analyzed by an electrolyte analyzer. Scanning electron microscopy (SEM) was used to assess morphologic changes and polarized light microscopy (PLM) was used to evaluate optical changes in the lesions.

RESULTS

The control group showed a statistically significantly (p < 0.05) higher calcium concentration compared with all the other groups. The APF group also had a statistically significantly higher calcium concentration (p < 0.05) than did the laser groups. However, there was no statistically significant difference in any of the laser groups whether combined with fluoride or not (p > 0.05). Upon SEM analysis, melted surfaces and crater-like holes 1-20 microm in diameter were found in the CO(2) laser and Nd:YAG laser groups. On PLM, positive birefringence and reversal of birefringence after acid challenge of the lased enamel were seen.

CONCLUSIONS

Using lasers and fluoride on decalcified enamel appears to increase the enamel's acid resistance, and the effects of the lasers were better than those of fluoride treatment.

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.

Fluoride uptake and acid resistance of enamel irradiated with Er:YAG laser

This study evaluated the resistance to demineralization and fluoride incorporation of enamel irradiated with Er:YAG. A total of 110 bovine teeth were selected and divided into eight groups: unlased, 37% phosphoric acid, and samples irradiated with the Er:YAG laser at several fluences (31.84 J/cm(2), 25.47 J/cm(2), 19.10 J/cm(2), 2.08 J/cm(2), 1.8 J/cm(2), and 0.9 J/cm(2)). The application of acidulated phosphate fluoride was performed after treatments. All samples were immersed in 2 ml of 2.0 M acetic-acetate acid solution at pH 4.5 for 8 h, and fluoride, calcium, and phosphorus ions dissolved were analyzed by atomic absorption spectrometry and spectrophotometry. The phosphoric acid and 31.84 J/cm(2) groups presented the lowest dissolution of calcium and phosphorus ions. Higher fluoride incorporation was observed on 1.8 J/cm(2) and 0.9 J/cm(2) groups. Based on these results, Er:YAG laser was able to decrease acid dissolution and increase fluoride uptake and can be a promissory alternative for preventive dentistry.

Acid resistance of dentin after erbium:yttrium-aluminum-garnet laser irradiation

The purpose of this study was to evaluate the acid resistance of erbium:yttrium-aluminum-garnet (Er:YAG) lased sub-surface dentin using a scanning electron microscope (SEM). Dentin disks were exposed to a single pulse of Er:YAG laser irradiation at 80 mJ/pulse under water spray, with the contact sapphire tip vertical to the dentin surfaces (n = 15). Five specimens from the laser-ablated dentin surfaces were observed. Ten specimens were crosscut, exposing the center of the lased point. For five of the specimens, the sub-surface of the lased dentin, with or without 10% phosphoric acid treatment, was evaluated. We used the remaining five specimens to analyze the degree of acid treatment on crosscut surface by observing the re-crosscut surfaces at the lased point. The irradiated dentin surfaces were irregular, scaly or flaky. Three sub-layers were observed in the sub-surface: a superficial, less decalcified layer; an intermediate most decalcified layer; and a deep, normal shade layer. Er:YAG laser irradiation affected the acid resistance of sub-surface dentin.

Bond strength of self-etching primer to bur cut, Er,Cr:YSGG, and Er:YAG lased dental surfaces

OBJECTIVE

The purpose of this study was to evaluate the tensile bond strength of a self-etching primer system to enamel and dentin surfaces treated with Er:YAG and Er,Cr:YSGG lasers.

BACKGROUND DATA

The recently introduced self-etching primer systems have been shown to adhere better to dental surfaces with thin or no smear layers. Moreover, there have been no previous reports on the bond strength of these adhesives to Er,Cr:YSGG laser-irradiated enamel and dentin, which have been shown to be free of a smear layer.

METHODS

Thirty samples of enamel and thirty of dentin were divided into three groups. The first group of each substrate served as a control with a standardized bur cut, and the other two groups were conditioned with Er:YAG (350 mJ, 10 Hz, 20 J/cm(2) for enamel; 300 mJ, 6 Hz, 17 J/cm(2) for dentin) and Er,Cr:YSGG laser (125 mJ, 20 Hz, 16 J/cm(2) for both substrates). After the bonding procedure, samples were restored with composite resin, and the tensile bond strength test was performed.

RESULTS

The ANOVA two-way analysis and the Tukey test at 5% significance level showed that for enamel and dentin, the bond strength values were statistically higher in Er:YAG-laser treated than in Er,Cr:YSGG-laser treated surfaces (p = 0.0001). However, bond strength means for both laser-irradiated groups were statistically lower than for the bur cut group (Er:YAG: p = 0.0281 and Er,Cr:YSGG: p < 0.0001). SEM observation of laser-irradiated surfaces revealed a roughened aspect and absence of smear layer.

CONCLUSIONS

The self-etching system adhesion was influenced by the type of erbium laser used, and the bond strength was higher in the Er:YAG-laser irradiated than in the Er,Cr:YSGG-laser irradiated surfaces.

Adhesion to Er:YAG Laser-prepared Dentin After Long-term Water Storage and Thermocycling

Simulation of thermal stress and long-term degradation presented in the oral environment adversely affected the adhesion of an etch & rinse adhesive system to Er:YAG laser-irradiated dentin.

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.