Analysis of surface roughness of enamel and dentin after Er,Cr:YSGG laser irradiation

Application of laser on enamel surface with three types of bioactive glasses-based resin infiltrants: An in vitro study

OBJECTIVE

The study aimed to evaluate and compare the surface micro-hardness, roughness, color, and morphology of enamel after Er,Cr:YSGG laser irradiation, followed by application of three types of bioactive glasses-based resin infiltrants, and the samples groups were challenged with the pH cycle.

METHODOLOGY

Experimental photoactivated resin infiltrants were synthesized using dimethacrylate resins, whereby three different types of bioactive glasses (BGs), i.e., 45S5, fluoridated-BG (F-BG), and borosilicate-BG (B-BG), were incorporated into the resin system. Initially, white spot lesions were created artificially on the toosth enamel surface, then irradiated with Er,Cr:YSGG laser. Then, the resin-only and BG-based resins were infiltrated on the enamel surface. All samples were pH challenged for 14 days, and the micro-hardness, surface roughness, surface morphology, and color stability (ΔE) analyses were conducted before and after the 14 days pH challenge.

RESULTS

After laser irradiation, the micro-hardness was significantly high with 45S5 group compared to resin-only (p = 0.021), F-BG (p = 0.042), and B-BG (p = 0.001) groups. After the pH challenge, the micro-hardness values for all groups were reduced significantly (p ≤ 0.05). The surface roughness was least with the resin-only group and showed a non-significant difference with F-BG (p = 0.34) and significant differences with both B-BG (p = 0.005), and 45S5 (p = 0.010) groups. After the pH cycle, the roughness of all groups was increased significantly (p ≤ 0.05), except B-BG group showed a non-significant difference (p = 0.528). The B-BG group showed significantly high ΔE between day 0 and baseline compared to resin-only (p = 0.0008), F-BG (p = 0.017), and 45S5 (p = 0.029), whereas between day 14 and baseline, the lowest ΔE value was observed for B-BG (14.2 ± 2.10) and maximum for the resin-only (20.57 ± 2.47) group. The SEM images showed pitting on the surface of all resin infiltrant groups after 14 days of pH challenge.

CONCLUSION

The morphological difference was observed after the laser irradiation on the enamel surface. The differences in micro-hardness, surface roughness, and color were observed after the application of experimental resin infiltrants and significant differences were observed after the pH challenge.

Effect of Er: YAG laser irradiation with additional low energy on resin-dentin bonding and morphology of bonded interface

OBJECTIVES

To examine the micro tensile bond strength (μTBS) and the resin-dentin interface on a laser-irradiated dentin surface using two different irradiation methods, with or without additional low-energy irradiation.

METHODS

The flat bovine dentin surface was divided into three groups: i). control group (C group, no irradiation), ii) 80 mJ/pulse Er: YAG laser group (80 group), iii) 80 + 30 mJ/pulse Er: YAG laser group (80 + 30 group, with an additional 30 mJ/pulse). After the roughness of the dentin surface was recorded, Clearfil SE Bond 2 or Clearfil Universal Bond Quick (Kuraray Noritake Dental Inc., Tokyo, Japan) was applied. After the μTBS testing, the failure mode was observed. The bonded interface was assessed using Rhodamine-dye incorporated adhesives and observed by optical coherence tomography.

RESULTS

The dentin surface showed opened dentinal tubules without a smear layer after irradiation. For both adhesives, the μTBS was significantly higher in 80 + 30 group than in the 80 group (p < 0.05). In the 80 group, the thickness of the adhesive layer was not uniform, and the dentin surface was occasionally in direct contact with the composite resin. The failure mode images showed that most of the fractures in the 80 group were at the sub-surface of irradiated dentin. The adhesive layers of the 80 + 30 groups were homogeneous.

CONCLUSIONS

The dentin surface was rough and irregular by 80 mJ irradiation, which might result in an inadequate resin-dentin interface and the weak μTBS. The bonded integrity was mitigated by additional irradiation.

Effect of Er,Cr: YSGG Laser on Bonding of Laminate Veneers using CAD/CAM (In Vitro Study)

AIM: This in vitro study was designed to evaluate the shear bond strength after bonding between porcelain laminate veneers and the tooth surface using different etching methods METHODS: Thirty freshly extracted maxillary premolars were used and prepared for receiving Enamic laminate veneers. Specimens were divided into two groups (n = 15), according to the surface treatment protocol. The specimens were sandblasted with 50 μm Al2O3 for 20 s; 2 bar pressure was maintained for air abrasion. Distribution of groups was as follow G1: Prepared enamel surface treatment of each tooth was according to the manufacturer’s instructions. G2: The prepared enamel surface of each tooth was subjected to Erbium,Chromium-Doped: Yttrium, Scandium, Gallium, and Garnet laser application. Light cured adhesive resin cement was applied to fitting surface of each ceramic specimen. To simulate thermal aging, the samples were subjected to 5000 thermal cycling in a thermocycler. By dividing the failure load (N) by the bonding area (mm2), debonding loads were calculated as shear stress (MPa). Numerical data were presented as mean and standard deviation values. They were explored for normality by checking the data distribution using Shapiro–Wilk test. Data showed parametric distribution and were analyzed using independent t-test. The significance level was set at p ≤ 0.05 within all tests. Statistical analysis was performed with R statistical analysis software version 4.1.2 for Windows. RESULTS: Group (II) (15.84 ± 3.09) had significantly higher mean value than group (I) (13.69 ± 2.36) (t = 2.15, p = 0.041). CONCLUSION: Within the limitation of this study, it was revealed that the laser surface treatment for tooth substrate plays a significant role in increasing the shear bond strength of laminate veneers.

The Use of Laser Energy for Etching Enamel Surfaces in Dentistry-A Scoping Review

BACKGROUND

In dental practice, different situations require etching the enamel layer. Acid etching, the present golden standard, may be replaced by other methods, such as laser etching. The main focus of our scoping review is to assess the existent literature regarding the effectiveness of different types of lasers, to identify the main aspects studied so far, and to understand where new search strategies are needed.

METHODS

The search was conducted in several databases focusing on the laser etching of human definitive enamel. We included English language articles published between January 2000 and December 2021.

RESULTS

The 34 articles reviewed showed that hard lasers, Er:YAG, Er,Cr:YAG, may represent an alternative etching method on enamel surfaces. They create a fractured, irregular surface and open dentin tubules, highly suitable for adhesion but with a lower risk of cavity formation. Nd:YAG, CO₂, and Diode lasers do not help in creating sufficient shear bond strength. There is, however, evidence suggesting that microcracks in the enamel layer may appear after thermomechanical ablation using laser energy.

CONCLUSIONS

While the use of acid etching is still successfully used for enamel conditioning, some researchers have emphasized the role played by saliva in the enamel-remineralization process a few days after the procedure. In this context, laser energy can be used, especially for bonding ceramic brackets in the case of orthodontic treatments. However, as thermomechanical ablation can generate microcracks, further research is required in order to establish clear findings concerning the use of laser energy on enamel etching.

Application of Er,Cr:YSGG laser versus photopolymerization after silver diamine fluoride in primary teeth

Examine the effect of dental curing light and laser treatments applied after Silver Diamine Fluoride (SDF) on dentin hardness in carious primary molars. This in-vitro study consisted of 30 extracted primary molars with caries extending into dentin without pulpal involvement. The collected teeth were randomly divided into three groups: group 1: received SDF then Sub-ablative low-energy of Er,Cr:YSGG laser, group 2: received SDF followed by application of curing light for 40 s, group 3: had SDF treatment only. In all groups, 38% Ag (NH3)2F SDF was used. Vickers hardness test was performed on sound dentin below carious lesion. Kruskal-Wallis Test was used to determine the mean difference in dentin hardness of the groups at 5% Significance level using SPSS software. Surface hardness of sound dentin below the carious lesion was statistically significantly higher in the laser + SDF group (891.24 ± 37.33 kgf/mm2) versus the two other groups (Light cure + SDF = 266.65 ± 90.81 kgf/mm2 and SDF only = 117.91 ± 19.19 kgf/mm2) with p-value ≤ 0.001. Although Photopolymerization of SDF increases the surface hardness of sound dentin below the carious lesion, applying laser after SDF has the highest surface hardness due to the laser's sub-ablation of dentin.

Does laser etching have an effect on application mode of a universal adhesive?-A microleakage and scanning electron microscopy evaluation

This study aimed to evaluate the microleakage of a universal adhesive's different application modes incorporated with Er,Cr:YSGG laser on Class V resin composite restorations. Sound human molar teeth (n = 30) were used for microleakage evaluations. Specimens with 60 standardized Class V cavities were divided into five groups according to the adhesive modes of universal adhesive, Adhese Universal (n = 12). Group 1-etch-and-rinse mode with phosphoric acid; Group 2-etch-and-rinse mode with Er,Cr:YSGG laser; Group 3-selective-etch mode with phosphoric acid; Group 4-selective-etch mode with Er,Cr:YSGG laser; Group 5-self-etch. After restorations were performed with a resin composite, Tetric N-Ceram, the specimens were polished and subjected to thermocycling (10,000X). Following immersion in 0.5% basic fuschin for a day, the teeth were sectioned and the degree of microleakage was determined along the tooth-resin composite interface using a light microscopy(40X). Five specimens from each group were examined by scanning electron microscopy. The Kruskal-Wallis, Siegel Castello, and Wilcoxon tests were used for statistical analyses (α = .05). At the enamel margins, significant differences were obtained among the groups (p < .05). Significantly higher microleakage scores were detected in Group 5 in comparison with Groups 1, 2, and 3. There were no significant differences between different adhesive strategies at the dentin margins (p > .05). While analyzing enamel and dentin microleakage scores, no statistically significant differences were observed in Groups 4 and 5 (p > .05). The laser application time and the adhesive modes of universal adhesives could affect the microleakage at the enamel margins. Different adhesive modes of universal adhesives combined with laser etching had no influence on the microleakage scores of dentin margins.

Adhesive bond integrity of dentin conditioned by photobiomodulation and bonded to bioactive restorative material

AIM

The aim of this in-vitro study is to investigate the shear bond strength (SBS) of Bioactive bulk fill restorative material (BARM) (Activa) by surface pre-treatment using Er,Cr:YSGG (ECL) on dentin in comparison to conventional dentin conditioning techniques.

MATERIAL AND METHODS

Sixty extracted non-carious, non-fractured, restoration free human molars were collected and mounted vertically in acrylic resin. The buccal surface of all molars were ground and polished with abrasive paper. The specimens were randomly allocated into four groups (n = 15) according to the type of surface treatment. Group 1 ECL + BARM, Group 2 ECL + Ketac + BARM, Group 3 Conventional Etch and Rinse + BARM, Group 4 Self-etch + BARM. The specimens from each group were positioned in a universal testing machine for SBS testing. Ten samples from each group were assessed for modes of failure. Means and standard deviations were compared using analysis of variance (ANOVA) and Tukey's post hoc test at a significance level of p < 0.05.

RESULTS

BARM bonded to dentin surface etched with conventional etch and rinse technique (group 3) exhibited SBS value of 18.45 ± 1.34. Similarly, the lowest bond strength was observed by group 4 (self-etch regime) bonded to BARM (16.09 ± 0.81). The bond strength among groups 1 (ECL + BARM), 2 (ECL + Ketac + BARM) and 3 (etch and rinse + BARM) were found to be comparable (p > 0.05).

CONCLUSION

Conditioning of dentin with photobiomodulation for the adhesive bonding of BARM showed comparable bond strength outcomes to conventional conditioning techniques.

Relationship between Er,Cr:YSGG laser power and surface roughness of lased radicular dentin

Background: This study sought to assess the effect of Er,Cr:YSGG laser power on the surface roughness of lased radicular dentin using atomic force microscopy (AFM).

Methods: Fifteen human radicular dentin samples were randomly divided into five groups: one control (G1, intact) and four experimental groups treated with 0.25W (G2), 0.5W (G3), 0.75W (G4) and 1W (G5) powers of Er,Cr:YSGG laser (2.78µm) at a repetition rate of 20 Hz, with a 600-µm-diameter sapphire tip. After irradiation, surface topography was analyzed by AFM using a Si probe in tapping mode. Quantitative information concerning the arithmetic average roughness (Ra) and quadratic mean roughness (Rq) was obtained from three 5×5µm areas of each sample. The data were analyzed using one-way ANOVA (P<0.05).

Results: The Ra and Rq values increased in G2 and G5 and decreased in G3 and G4 groups compared to the control group. The maximum Ra and Rq values were noted in G5, which were significantly higher than the corresponding values in G3 (P<0.05).

Conclusion: No direct correlation was found between Er,Cr:YSGG laser power and surface roughness of lased radicular dentin. Laser therapy with a mean power of 0.5W and 1W caused the lowest and highest surface roughness, respectively.

Microshear bond strength of self-adhesive composite to ceramic after mechanical, chemical and laser surface treatments

Objectives

This study aimed to assess the microshear bond strength of a repairing self-adhesive flowable composite to ceramic after mechanical, chemical and laser treatment of the ceramic surface.

Materials and Methods

Forty zirconia and forty feldspathic ceramic blocks measuring 8 x 8 x 2 mm were fabricated. Feldspathic blocks were divided into four groups of control (1), laser (2780 nm) (2), sandblasting + hydrofluoric (HF) acid + silane (3) and laser (2780 nm) + HF acid + silane (4). Zirconia blocks were also divided into four groups of control (1), laser (2780 nm) (2), sandblasting + Z-Prime Plus (3) and laser (2780 nm) + Z-Prime Plus (4). Vertise Flow composite was bonded to treated ceramic surfaces as a repairing material, then the samples were subjected to 1000 thermal cycles. Repair bond strength was measured by Instron machine and data were analyzed using one-way ANOVA and post hoc test (P < 0.05).

Results

Maximum and minimum bond strength values were observed in zirconia-control (22.57 ± 4.76 MPa) and feldspathic-control (8.65 ± 6.41 MPa) groups, respectively. There was no significant differences between subgroups within the zirconia or feldspathic groups (P > 0.05), however the bond strength of zirconia subgroups was significantly higher than that of feldspathic subgroups.

Conclusion

Vertise Flow provides relatively good bond strength to ceramic even with no surface treatment.

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers. Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n=19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey posthoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite. Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups. Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin.

Effects of Er,Cr:YSGG Laser Pulse Frequency on Microtensile Bond Strength to Enamel

Literature regarding the influence of Er,Cr:YSGG laser pulse frequency with different output power levels on adhesion properties of adhesive resin to lased enamel is limited. Therefore, the aim of the present study was to evaluate the effects of laser pulse frequency (20, 35, and 50 Hz) at two different output power settings (3 and 6 W) of Er,Cr:YSGG on the microtensile bond strength (μTBS) of adhesive resin to enamel. Crowns of 35 intact bovine incisors were embedded into self-cure acrylic resin individually, and then flat enamel surfaces were prepared with 600-grit silicon carbide papers under water cooling. Teeth were divided randomly into seven groups. Enamel surfaces were irradiated with Er,Cr:YSGG laser operated at one of six output power–pulse frequency combinations (6 W20 Hz, 6 W–35 Hz, 6 W–50 Hz, 3 W–20 Hz, 3 W–35 Hz, and 3 W–50 Hz) in groups 1-6, respectively. Bur-treated surfaces served as a control in group 7. After surface treatments and bonding procedures, composite build-ups were done in three layers up to a height of 4 mm. Next, all bonded teeth were sectioned into the resin-enamel sticks to be tested in a μTBS testing machine. The μTBS data were analyzed with univariate analysis of variance under a general linear model with the factor ‘tooth' added as a random effect to the design. Resin-enamel interfaces were evaluated with scanning electron microscopy (SEM). The μTBS to laser-irradiated enamel in group 1 (6 W–20 Hz) was significantly lower than those of bur-treated enamel (p&lt;0.05). However, group 6 (3 W–50 Hz) showed significantly higher μTBS values than did bur-treated teeth (p&lt;0.05). SEM evaluation revealed enormous morphological alterations of laser-irradiated specimens, such as extensive vertical and horizontal microcracks and gaps, with the exception of group 6. The bonding effectiveness of adhesive resin to laser-irradiated enamel was affected by the pulse frequency of the Er,Cr:YSGG laser. Although the parameters recommended by the manufacturer lowered μTBS, increasing the pulse rate may maintain optimum μTBS.

Comparative Evaluation of the Etching Pattern of Er,Cr:YSGG & Acid Etching on Extracted Human Teeth-An ESEM Analysis

INTRODUCTION

Etching of enamel and dentin surfaces increases the surface area of the substrate for better bonding of the tooth colored restorative materials. Acid etching is the most commonly used method. Recently, hard tissue lasers have been used for this purpose.

AIM

The aim of the present study was to evaluate and compare the etching pattern of Er,Cr:YSGG and conventional etching on extracted human enamel and dentin specimens.

MATERIALS AND METHODS

Total 40 extracted non-diseased teeth were selected, 20 anterior and 20 posterior teeth each for enamel and dentin specimens respectively. The sectioned samples were polished by 400 grit Silicon Carbide (SiC) paper to a thickness of 1.0 ± 0.5 mm. The enamel and dentin specimens were grouped as: GrE1 & GrD1 as control specimens, GrE2 & GrD2 were acid etched and GrE3 & GrD3 were lased. Acid etching was done using Conditioner 36 (37 % phosphoric acid) according to manufacturer instructions. Laser etching was done using Er,Cr:YSGG (Erbium, Chromium : Ytrium Scandium Gallium Garnet) at power settings of 3W, air 70% and water 20%. After surface treatment with assigned agents the specimens were analyzed under ESEM (Environmental Scanning Electron Microscope) at X1000 and X5000 magnification.

RESULTS

Chi Square and Student "t" statistical analysis was used to compare smear layer removal and etching patterns between GrE2-GrE3. GrD2 and GrD3 were compared for smear layer removal and diameter of dentinal tubule opening using the same statistical analysis. Chi-square test for removal of smear layer in any of the treated surfaces i.e., GrE2-E3 and GrD2-D3 did not differ significantly (p>0.05). While GrE2 showed predominantly type I etching pattern (Chi-square=2.78, 0.05<p>0.10) and GrE3 showed type III etching (Chi-square=4.50, p<0.05). The tubule diameters were measured using GSA (Gesellschaft fur Softwareentwicklung und Analytik, Germany) image analyzer and the 't' value of student 't' test was 18.10 which was a highly significant result (p<.001). GrD2 had a mean dentinal tubule diameter of 2.78μm and GrD3 of 1.09μm.

CONCLUSION

The present study revealed type I etching pattern after acid etching, while type III etching pattern in enamel after laser etching. The lased dentin showed preferential removal of intertubular dentin while acid etching had more effect on the peritubular dentin. No significant differences was observed in removal of smear layer between the acid etched and lased groups. Although diameter of the exposed dentinal tubules was lesser after lased treatment in comparison to acid etching, further long term in vivo studies are needed with different parameters to establish the usage of Er,Cr:YSGG as a sole etching agent.

Effect of Er,Cr:YSGG Laser at Different Output Powers on the Micromorphology and the Bond Property of Non-Carious Sclerotic Dentin to Resin Composites

BACKGROUND

The objective of this study was to investigate the influence of Er,Cr:YSGG laser irradiated at different powers on the micromorphology and the bonding property of non-carious sclerotic dentin to resin composites.

METHODS

Two hundred bovine incisors characterized by non-carious sclerotic dentin were selected, and the seventy-two teeth of which for surface morphological analysis were divided into nine groups according to various treatments (A: the control group, B: only treated with the adhesive Adper Easy One, C: diamond bur polishing followed by Adper Easy One, D-I: Er,Cr:YSGG laser irradiating at 1W, 2W, 3W, 4W, 5W, 6W output power, respectively, followed by Adper Easy One). The surface roughness values were measured by the non-contact three-dimensional morphology scanner, then the surface micromorphologies of surfaces in all groups were assessed by scanning electron microscopy (SEM); meanwhile, Image Pro-Plus 6.0 software was used to measure the relative percentage of open tubules on SEM images. The rest, one hundred twenty-eight teeth for bond strength test, were divided into eight groups according to the different treatments (A: only treated with the adhesive Adper Easy One, B: diamond bur polishing followed by the above adhesive, C-H: Er,Cr:YSGG laser irradiating at 1 W, 2 W, 3 W, 4 W, 5 W, 6 W output power, respectively, followed by the above adhesive), and each group was subsequently divided into two subgroups according to whether aging is performed (immediately tested and after thermocycling). Micro-shear bond strength test was used to evaluate the bond strength.

RESULTS

The 4W laser group showed the highest roughness value (30.84±1.93μm), which was statistically higher than the control group and the diamond bur groups (p<0.05). The mean percentages ((27.8±1.8)%, (28.0±2.2)%, (30.0±1.9)%) of open tubules area in the 4W, 5W, 6W group were higher than other groups (p<0.05). The 4W laser group showed the highest micro-shear bond strength not only in immediately tested (17.60±2.55 PMa) but after thermocycling (14.35±2.08MPa).

CONCLUSION

The Er,Cr:YSGG laser at 4W power can effectively improve the bonding property between non-carious sclerotic dentin and resin composites by increasing the roughness and mean percentage area of open tubules.

Evaluation of the clinical success of class I cavities prepared by an Er:YAG laser-5-year follow-up study

The purpose of this study was to evaluate, after 5 years, the clinical success of preparing class 1 composite resin restorations with an Er:YAG laser. Sixty-five teeth of 30 patients were included in the study, and an Er:YAG laser emitting at a wavelength of 2.94 μm was used for the class I cavity preparations with not more than one third of the mesiodistal width of the occlusal surfaces of each tooth. All cavities were restored with a light-cured composite resin, following a single bond application. After the baseline examination, restorations were reevaluated by the same experienced clinician after 5 years, using the modified Ryge criteria. At the end of 5 years, 41 of the 65 restorations were evaluated in 22 patients and scored. With respect to marginal discoloration, anatomic form, color match, and surface texture, significant differences were found between baselines tested after 5 years. Clinical evaluation of postoperative sensitivity showed that 90.2 % were rated as alpha. All restorations evaluated in this study demonstrated acceptable clinical performance within the evaluation period based on the alpha and bravo ratings for clinically satisfactory restorations. Further evaluations are necessary for a better clinical performance analysis.

Effect of different temporary crown materials and surface roughening methods on the shear bond strengths of orthodontic brackets

OBJECTIVE

The aim of this study was to evaluate the effect of different temporary crown materials (TCMs) and surface roughening methods on the shear bond strength (SBS) of orthodontic brackets.

BACKGROUND DATA

TCMs are widely used during orthodontic treatment in teeth in need of prosthetic treatment, to prevent damage to the final restoration. However, there is no consensus considering the best method for roughening of the surface of TCMs.

METHODS

Five different TCMs [Dentalon Plus-(D), Basworth Trim II-(B), Voco Structure Premium-(V), 3M ESPE Protempt 4-(P), and Revotek LC-(R)] were used in this study. Different surface roughening methods (37% phosphoric acid, sandblasting, and Er:YAG laser) were employed in three subgroups (n=20). The SBS test was used to assess the durability of all groups. Scanning electron microscopy (SEM) analysis was performed on a representative specimen in each group.

RESULTS

The highest mean SBS value was observed in group V, followed by groups D and P, regardless of the surface treatment. The lowest SBS values were observed in group B. The laser-irradiated groups had higher SBS values than the sandblasted and acid-etched groups. Furthermore, a significant difference in SBS values was observed between the laser-irradiated group V and all other groups (p<0.005).

CONCLUSIONS

The effects of the chemical nature of TCMs on the SBS values appeared to be clinically negligible, whereas the type of surface treatments had a significant influence on bond strengths. Er:YAG laser irradiation caused a significant increase in bond strength between the TCMs and orthodontic brackets.

Effect of Er,Cr:YSGG laser application in the treatment of experimental periodontitis

The purpose of this study was to evaluate the influence of an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser in the absence or presence of manual scaling and root planning (SRP) for the treatment of induced periodontitis in rats. Ligatures were placed in the subgingival region of the maxillary first molar. After a 7-day period, the ligatures were removed, and 40 rats were randomly divided into four groups (G), as follows: (GI) no treatment, (GII) scaling and root planning (SRP) with curettes, (GIII) Er,Cr:YSGG laser irradiation and (GIV) SRP with curettes followed by Er,Cr:YSGG laser irradiation. Seven and 30 days after the treatment, the animals were sacrificed and histologic, histometric and immunohistochemistry analyses were performed. All groups showed similar histopathological characteristics during the evaluation period. The histometric analysis was confirmed using Bonferroni and paired t tests. At 7 and 30 days, groups II, III and IV exhibited greater bone formation in the furcation area when compared to group I (p < 0.0001; p < 0.05). During the 7-day period, the groups irradiated with the laser (III and IV) showed a statistically larger new bone area than the group treated with SRP (II) (p < 0.01). Immunohistochemistry analysis revealed that the control group exhibited a higher expression of tartrate-resistant acid phosphatase (TRAP) and the receptor activator of nuclear factor κΒ ligand (RANKL) when compared to groups II, III and IV (p < 0.05). All treatments were able to reduce the inflammatory processes, consequently enabling the repair of periodontal tissues. The results achieved with the application of the Er,Cr:YSGG laser suggest that this laser can stimulate greater bone formation, especially over a shorter period of time.

The effect of Er,Cr:YSGG laser irradiation on the push-out bond strength of RealSeal self-etch sealer

OBJECTIVE

The aim of this study was to evaluate the effect of an erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser on the push-out bond strength of RealSeal Self-Etch (SE) sealer.

BACKGROUND DATA

Various methods are used for smear layer removal in endodontics, such as the application of Er,Cr:YSGG lasers. This laser system may influence the bond strength of resin-based sealers.

METHODS

Sixty single-rooted extracted teeth were selected. After root canal preparation, samples were divided into two experimental groups and one positive control group (n=20 per group). In group 1, the smear layer was removed by irrigation with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl). In group 2, the smear layer was removed using a 2.78 μm Er,Cr:YSGG laser with radial firing tips (RFT3) (parameters: 1.5 W, 140 μs, 20 Hz, and 15% water to 15% air ratio), moving at 2 mm/sec in an apico-coronal direction. Group 3 served as a positive control group. Five specimens from each group were selected for scanning electron microscope (SEM) observation. The remaining 45 roots were obturated with RealSeal SE/Resilon and subjected to push-out tests. Data were analyzed using one way analysis of variance (ANOVA) and Tamhane's test.

RESULTS

The results showed no significant difference between push-out bond strength of root canal fillings in the EDTA+NaOCl group and the 1.5 W laser group (p>0.05). The positive control group showed the lowest push-out bond strength.

CONCLUSIONS

The results of the present study indicate that the application of an Er,Cr:YSGG laser with radial firing tips did not adversely affect the push-out bond strength of RealSeal SE sealer to dentin.

Shear bond strength of resin cement to an acid etched and a laser irradiated ceramic surface

PURPOSE

To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic.

MATERIALS AND METHODS

Fifty-five ceramic blocks (5 mm × 5 mm × 2 mm) were fabricated and embedded in acrylic resin. Their surfaces were finished with 1000-grit silicon carbide paper. The blocks were assigned to five groups: 1) 9.5% hydrofluoric-acid etching for 60 s; 2-4), 1.5-, 2.5-, and 6-W Er,Cr:YSGG laser applications for 60 seconds, respectively; and 5) no treatment (control). One specimen from each group was examined using scanning electron microscopy. Ceramic primer (Rely X ceramic primer) and adhesive (Adper Single Bond) were applied to the ceramic surfaces, followed by resin cement to bond the composite cylinders, and light curing. Bonded specimens were stored in distilled water at 37℃ for 24 hours. Shear bond strengths were determined by a universal testing machine at 1 mm/min crosshead speed. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (α=0.05).

RESULTS

Adhesion was significantly stronger in Group 2 (3.88 ± 1.94 MPa) and Group 3 (3.65 ± 1.87 MPa) than in Control group (1.95 ± 1.06 MPa), in which bonding values were lowest (P<.01). No significant difference was observed between Group 4 (3.59 ± 1.19 MPa) and Control group. Shear bond strength was highest in Group 1 (8.42 ± 1.86 MPa; P<.01).

CONCLUSION

Er,Cr:YSGG laser irradiation at 1.5 and 2.5 W increased shear bond strengths between ceramic and resin cement compared with untreated ceramic surfaces. Irradiation at 6 W may not be an efficient ceramic surface treatment technique.

Effect of Surface Treatment with Er;Cr:YSSG, Nd:YAG, and CO2 Lasers on Repair Shear Bond Strength of a Silorane-based Composite Resin

Background and aims. The aim of the present study was to compare the effect ofsurface treatment with Er; Cr:YSSG, Nd:YAG, and CO₂ lasers on repair shear bond strength of a silorane-based composite resin.

Materials and methods. Sixty eight cylindrical samples of a silorane-based composite resin (Filtek Silorane) were pre-pared and randomly divided into 4 groups as follows: group 1: without surface treatment; groups 2, 3 and 4 with surface treatments using Er; Cr:YSSG, Nd:YAG, and CO₂ lasers, respectively. A positive control group (group 5) was assigned in order to measure cohesive strength. Repair shear bond strength values were measured and data was analyzed using one-way ANOVA and a post hoc Tukey test at a significance level of α=0.05.

Results. There were statistically significant differences in repair shear bond strength values between group 2 and other groups (P < 0.05); and between group 1and groups 3and 4 (P < 0.001); however, there were no significant differences be-tween groups 3 and 4 (P = 0.91).

Conclusion. The repair shear bond strength of silorane-based composite resin was acceptable by surface treatment with lasers

Bond strength of two resin cements to dentin after disinfection pretreatment: effects of Er,Cr:YSGG laser compared with chemical antibacterial agent

OBJECTIVE

This study compared the effects of two disinfection procedures (2% chlorhexidine [CHX] solution versus Er,Cr:YSGG laser irradiation) on the shear bond strength of ED primer II/Panavia F2.0 (ED/P) and Excite DSC/Variolink N (Ex/V).

BACKGROUND DATA

Different methods are used for cavity disinfection prior to adhesive cementation, which may influence the bonding ability of resin cements.

METHODS

Flat dentin surfaces were prepared on 100 extracted premolars and randomly divided into 10 groups. In the eight experimental groups, indirect composite samples were cemented with either ED/P or Ex/V under three disinfecting conditions on the dentin surface as follows: (1) CHX application before ED primer II/ after etching, (2) wet laser irradiation (Er,Cr:YSGG laser, 20 Hz, 0.75 W, 15% water +15% air), (3) dry laser irradiation with no water and air cooling. The control groups had no disinfectant application. After 24 h water storage, bond strength test was performed. The data (MPa) were analyzed using two way ANOVA and Tukey tests.

RESULTS

The lowest and highest bond strengths were obtained by dry laser and wet laser (10.18±2.67 and 17.36±2.94 for ED/P, 9.64±2.66 and 20.07±3.36 for Ex/V, respectively). For each cement, two-by-two comparisons of four groups revealed significant differences only for dry laser with others (p<0.001).

CONCLUSIONS

The use of CHX and Er,Cr:YSGG laser at the low fluences with water/air cooling as the antibacterial agents does not adversely influence the bonding ability of the etch-and-rinse and the self-etch cements.

Er:YAG-laser and sodium hypochlorite influence on bond to dentin

PURPOSE

The aim of this in vitro study was to verify the interference of previous application of sodium hypochlorite in the bond strength to dentin irradiated with Er:YAG laser (80 mJ, 2 Hz, 25 J/cm(2)), using two adhesive systems with different solvents (Adper Single Bond2 - 3M ESPE [SB] and Prime&Bond 2.1 - Dentsply [PB].

STUDY DESIGN

Ninety standardized dentin disks were treatment with phosphoric acid etching (PA), PA and 10% sodium hypochlorite (SH), Er:YAG laser (ER), ER and 10% SH. After surface preparation, samples received SB or PB followed by composite resin Z250 (3M ESPE)(n = 10). Tensile bond strength test was performed (0.5 mm/min) 24 h after bonding procedure and one treated dentin disk of each group was selected to scanning and transmission electron microscopy (SEM and TEM) observations. Bond strength test data were evaluated by three-way ANOVA and Tukey (P < 0.05) tests.

RESULTS

Tested systems had similar bonding behavior when applied with conventional method. SH produced no improvement in bond strength. Phosphoric acid etching either associated with SH, or not, provided higher bond strength values than ER. SEM showed typical ablation pattern on dentin after ER irradiation. SH application after PA promoted greater porosity in intertubular dentin exposing secondary tubules. SH used after ER irradiation showed more evident peritubular dentin. TEM results showed that both PA and ER exposed inter- and peri-tubular dentin collagen fibers.

CONCLUSIONS

Er:YAG irradiation had a negative influence on SB adhesive, and in both methods, association of SH did not completely remove collagen fiber network, but altered its configuration.

Effect of surface treatment with sandblasting and Er,Cr:YSGG laser on bonding of stainless steel orthodontic brackets to silver amalgam

Objectives: Satisfactory bonding of orthodontic attachments to amalgam is a challenge for orthodontists. The aim of this in vitro study was to compare the shear bond strength of stainless steel orthodontic brackets to silver amalgam treated with sandblasting and Er,Cr:YSGG laser. Study Design: Fifty-four amalgam discs were prepared, polished and divided into three groups: In group 1 (the control group) the premolar brackets were bonded using Panavia F resin cement without any surface treatment; in groups 2 and 3, the specimens were subjected to sandblasting and Er,Cr:YSGG laser respectively, before bracket bonding. After immersing in distilled water at 37°C for 24 hours, all the specimens were tested for shear bond strength. Bond failure sites were evaluated under a stereomicroscope. Data was analyzed using one-way ANOVA and a post hoc Tukey test. Results: The highest and lowest shear bond strength values were recorded in the laser and control groups, respectively. There were significant differences in mean shear bond strength values between the laser and the other two groups (p<0.05). However, there were no significant differences between the sandblast and control groups (p=0.5). Conclusions: Amalgam surface treatment with Er,Cr:YSGG laser increased shear bond strength of stainless steel orthodontic brackets.

Key words: Amalgam, surface treatment, shear bond strength, sandblasting, Er,Cr:YSGG laser.

Bond strength of adhesive systems to Er,Cr:YSGG laser-irradiated dentin

OBJECTIVE

The purpose of this study was to evaluate the effects of Er,Cr:YSGG laser irradiation and different adhesive procedures on bond strength of two bonding agents to dentin.

BACKGROUND DATA

Studies have shown that laser-irradiated dentinal tissue yields lower bond strengths than does nonirradiated dentin. In this study, different treatment methods of laser irradiating dentin were studied to enhance the bond strength of bonding agents to nonirradiated dentin.

METHODS

Third molars were wet ground with SiC until the occlusal flat dentin surface was exposed, and the teeth were randomly assigned to six groups (n=5). A two-step self-etching primer (Clearfil SE Bond, G1) and a two-step etch-and-rinse adhesive (Single Bond Plus, G2) were applied to the nonirradiated dentin surface according to manufacturer's instructions, as control groups. In G3 and G4, the same adhesives were applied after Er,Cr:YSGG laser irradiation, whereas in G5 and G6 adhesives were applied after Er,Cr:YSGG laser irradiation, phosphoric acid etching, and NaOCl deproteinization of etched dentin. The Er,Cr:YSGG laser worked at 2.78??m and the repetition rate was fixed at 20?Hz. Composite blocks were built on bonded surfaces and the teeth were stored for 24?h at 37?C. Restored teeth were vertically and serially sectioned to obtain bonded specimens for the bond strength test. Data were analyzed by two-way ANOVA and Tukey test (?=5%).

RESULTS

Laser irradiation reduced bond strengths for the two adhesives, regardless of acid etching and deproteinization of dentin post-irradiation (p<0.05). The self-etching primer system showed higher bond strengths to laser irradiated dentin than did Single Bond Plus (p<0.05). The adhesive systems applied to normal dentin yielded higher bond strengths than when they were applied to laser irradiated dentin (p<0.05).

CONCLUSIONS

The self-etching primer seemed to be less affected by dentin irradiation with Er,Cr:YSGG laser. The additional etching and NaOCl solution did not overcome the effects of laser irradiation on dentin.

Effect of acid and laser etching on shear bond strength of conventional and resin-modified glass-ionomer cements to composite resin

Success in sandwich technique procedures can be achieved through an acceptable bond between the materials. The aim of this study was to compare the effect of 35% phosphoric acid and Er,Cr:YSGG laser on shear bond strength of conventional glass-ionomer cement (GIC) and resin-modified glass-ionomer cement (RMGIC) to composite resin in sandwich technique. Sixty-six specimens were prepared from each type of glass-ionomer cements and divided into three treatment groups as follows: without pretreatment, acid etching by 35% phosphoric acid for 15 s, and 1-W Er,Cr:YSGG laser treatment for 15 s with a 600-μm-diameter tip aligned perpendicular to the target area at a distance of 1 mm from the surface. Energy density of laser irradiation was 17.7 J/cm(2). Two specimens in each group were prepared for evaluation under a scanning electron microscope (SEM) after surface treatment and the remainder underwent bonding procedure with a bonding agent and composite resin. Then the shear bond strength was measured at a crosshead speed of 0.5 mm/min. Two-factor analysis of variance and post-hoc Tukey test showed that the cement type, surface treatment method, and the interaction of these two factors significantly affect the shear bond strength between glass-ionomer cements and composite resin (p < 0.05). Surface treatment with phosphoric acid or Er,Cr:YSGG laser increased the shear bond strength of GIC to composite resin; however, in RMGIC only laser etching resulted in significantly higher bond strength. These findings were supported by SEM results. The fracture mode was evaluated under a stereomicroscope at ×20.

Effects of ultramorphological changes on adhesion to lased dentin-Scanning electron microscopy and transmission electron microscopy analysis

Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin-dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (μTBS) of an adhesive to dentin. Seventy-two dentin disks were divided into nine groups (n = 8): G1-Control (600-grit SiC paper); Er:YAG groups: G2- 250 mJ/4 Hz; G3- 200 mJ/4 Hz; G4- 180 mJ/10 Hz; G5- 160 mJ/10 Hz; Er,Cr:YSGG groups: G6- 2 W/20 Hz; G7- 2.5 W/20 Hz; G8- 3 W/20 Hz; G9- 4 W/20 Hz. Specimens were processed for cross-sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty-five dentin samples (n = 5) were restored and submitted to μTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest μTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross-sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin.

Comparison of microleakage of three adhesive systems in class V composite restorations prepared with Er,Cr:YSGG laser

OBJECTIVE

This study compared microleakage of three adhesives in class V (CI V) composite restorations prepared with Er,Cr:YSGG laser.

BACKGROUND DATA

Changes produced on enamel and dentin surfaces subsequent to laser irradiation influence microleakage of composite restorations.

MATERIALS AND METHODS

CI V cavities were prepared in 80 sound extracted human premolars with Er,Cr:YSGG laser. The teeth were randomly divided into 4 groups (n = 20). In group 1, a total-etch adhesive was used, and two-step and one-step self-etch adhesives were used in groups 2 and 3, respectively. Group 4 was the control group with no adhesives. Following restoration and thermocycling, microleakage was evaluated. To compare microleakage in occlusal and gingival margins in each group, the Wilcoxon test was used. Kruskal-Wallis analysis was used for comparison of occlusal and gingival microleakage, and two-by-two comparisons were made using the Mann-Whitney U test.

RESULTS

There were significant differences in microleakage between occlusal and gingival margins in each group except for the control group. Significant differences were observed in occlusal and gingival microleakage among all the groups. Two-by-two comparisons revealed significant differences in occlusal microleakage between the control group and the other groups. There were significant differences in gingival microleakage between groups 1 and 2 and groups 1 and 3; however, differences in gingival microleakage between groups 2 and 3 were not significant.

CONCLUSION

With all the adhesives, microleakage was significantly higher in gingival margins compared with occlusal margins. In occlusal margins, there were no significant differences in microleakage among the three adhesives. In gingival margins, self-etch adhesives revealed less microleakage than the total-etch adhesive.

Effect of Er,Cr: YSGG Laser on the Microtensile Bond Strength of Two Different Adhesives to the Sound and Caries-affected Dentin

The microtensile bond strength of a three-step etch-and-rinse and a two-step self-etch adhesive is not negatively affected by Er,Cr:YSGG laser irradiation in sound and caries-affected dentin.

Shear bond strength of composite bonded to Er,Cr:YSGG laser-prepared dentin

OBJECTIVE

The purpose of this in vitro study was to evaluate dentin bond strength to resin composite following high-speed rotary or Er,Cr:YSGG laser preparation using two different adhesive systems.

MATERIALS AND METHODS

One hundred and forty dentin specimens were prepared from human molars. Seventy specimens were prepared with a high-speed diamond bur and 70 of the specimens were prepared with an Er,Cr:YSGG laser. Each group was subdivided into 7 groups of 10 teeth and etched with either 37% H3PO4, laser etched at two different power levels (1.25 W and 3 W), or not etched. Nano-hybrid composite resin cylinders 4 x 2 mm in size (Tetric EvoCeram, Vivadent) were bonded to the dentin surfaces with the application of an etch-and-rinse adhesive (Exite/Vivadent), or a self-etching adhesive (AdheSe/Vivadent). After storage in distilled water and thermocycling, a shear bond strength test was performed on all specimens and the data were statistically analyzed.

RESULTS

ANOVA detected significant differences between the tested groups (p < 0.001). Duncan's multiple comparison test showed that Excite-applied specimens that were prepared with laser and laser etched (1.25 W or 3 W) had higher mean bond strengths. Both AdheSe- and Excite-applied specimens prepared with the diamond bur and laser etched (1.25 W) showed the lowest mean bond strength values (p < 0.05).

CONCLUSION

The results suggest that dentin surfaces prepared with the Er,Cr:YSGG laser and etched with the laser (at either 1.25 or 3 W) may provide comparable or increased composite resin bond strengths, depending on the adhesive used.

Basic Study of Morphological Changes and Surface Roughness of Cavities Prepared by TEA CO2Laser Irradiation

OBJECTIVE

The purpose of this study was to investigate the morphological change of dental hard tissue and surface roughness of cavities prepared by transversely excited, atmospheric pressure (TEA) CO2 laser irradiation.

BACKGROUND DATA

It has been reported that dental hard tissues and bone can be removed by a long-pulse of TEA CO2 laser irradiation with minimal thermal damage. However, there are few reports on the surface roughness of lased teeth.

METHODS

The TEA CO2 laser was irradiated on the enamel and dentin surfaces of extracted human teeth under the following conditions: wavelength, 10.6 microm; output, 95 mJ/pulse; pulse repetition rate, 1 Hz; irradiation time, 7.5 microsec/shot; and energy density, 7.9 J/cm2. Morphological studies were performed by histological and scanning electron microscopic (SEM) examination. Surface roughness of prepared cavities was measured by three-dimensional laser microscopy.

RESULTS

Irradiated dentin produced a deeper defect (705 +/- 11 microm) than the enamel (501 +/- 10 microm). Histological appearance showed a basophilic line at the margin of lased dentin. SEM observation noted that the surfaces of the enamel cavity seem to be melted, and dentinal tubules were sealed. The surface roughness of the enamel cavity wall and dentin floor were 175 +/- 5 microm and 170 +/- 6 microm, respectively.

CONCLUSION

These findings suggest that it is possible to remove carious dental hard tissue or cavity preparation with the TEA CO2 laser irradiation. Lased dental hard tissue can facilitate caries prevention, and surface roughness of the cavities might improve the bond strength of restorative dental materials.

Morphological Study of the Er,Cr:YSGG Laser for Root Canal Preparation in Mandibular Incisors with Curved Root Canals

OBJECTIVE

The objectives of this study were to observe morphological changes of root canal walls and to evaluate the capability of Er,Cr:YSGG laser for preparation of curved mandibular incisor root canals in vitro.

BACKGROUND DATA

There are no published reports on the use of Er,Cr:YSGG laser for curved root canal preparation.

METHODS

Twenty curved mandibular incisor root canals (10 and 15 degrees) were prepared sequentially by laser irradiation at 20 Hz, 2 Wusing two different sizes of fine fiber tips (200 and 320 microm in diameters). After laser irradiation, the teeth were bisected longitudinally, and the specimens were observed by stereoscope and scanning electron microscope (SEM).

RESULTS

Root canal walls of the irradiated areas showed step-like appearances and openings of dentinal tubules, and root canal preparation, having curvatures of less than 10 degrees, could be carried out by this laser irradiation.

CONCLUSIONS

Er,Cr:YSGG laser irradiation is capable of preparing root canals having curvatures of less than 10 degrees.

Lasers in dentistry

BACKGROUND

During the last two decades, much has been written in both the scientific literature and the popular press about lasers and their use in the dental office. Both soft- and hard-tissue applications have been discussed, including frenectomy, gingival contouring, caries removal and bleaching.

OVERVIEW

Almost one-third of patients surveyed by the American Dental Association in the late 1990s thought it was very important that their dentists have lasers, which could put pressure on dentists to invest in this tool to attract patients. The authors describe the different types of dental lasers and examine the science behind their applications in dentistry.

CONCLUSION AND CLINICAL IMPLICATIONS

Although lasers do have legitimate uses in dentistry, they do not take the place of any of the more conventional tools in the dentist's armamentarium. Before investing in a laser, dentists should fully understand the differences between the various types, including what the scientific literature says about their applications.