Effect of Er: YAG Laser Pulse Width on Shear Bond Strength Between Layered Ceramic and Zirconia Substructure

Objectives: The increasing applications of composite resins and the need for correction of defects developed over time call for strategies to increase the bond strength of new repair composite resin to old (aged) composite resin. Thus, this study aimed to assess the effect of erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiation with various power levels on shear bond strength (SBS) of repair to aged nanofilled composite resin. Materials and Methods: Thermocycled disc-shaped (4.0×7.0mm) nanofilled composite resin specimens were randomly assigned to 4 groups (n=15): bur abrasion and 35% phosphoric acid (control group), irradiation of 1 W Er:YAG laser, irradiation of 2W Er:YAG laser, and irradiation of 4.5W Er:YAG laser. The SBS was measured after the application of repair composite and thermocycling. Specimens were observed under a stereomicroscope to determine the mode of failure. Atomic force microscopy (AFM) was used to assess the surface topography. Data were analyzed with one-way ANOVA, Games-Howell, and Fisher's exact tests (α=0.05). Results: The mean SBS in the 1W and 2W laser groups was significantly lower than that in the 4.5W laser and control groups (P<0.05). The difference in SBS of the 1W and 2W laser (P=0.999), and the 4.5W laser and control (P=0.999) groups was not significant. Conclusion: Er:YAG laser irradiation with 4.5W power yielded a SBS comparable to that of the control group and significantly higher than that of the 1W and 2W laser groups.

Purpose: This study evaluated the effects of surface treatment of zirconia with erbium-doped yttrium aluminum garnet (Er-YAG) laser on shear bond strength to resin cement. Materials and Methods: Thirty disc-shaped zirconia specimens (10 mm in diameter and 2 mm in thickness) were fabricated, randomly assigned to 3 groups (n = 10) and treated surface with: Gr. N) no treated surface, Gr. S) sandblasted with 50 micron alumina and Gr. L) treated with an Er-YAG laser. Zirconia surface was then applied with metal/zirconia primer prior to be cemented to composite cylinder (5 mm in diameter and 4 mm in thickness) with resin cement. Shear bond strength test was performed at a crosshead speed of 0.5 mm/min. Data were analyzed by ANOVA and Tukey HSD tests. Results: The means and standard deviations of shear bond strength (MPa) were: Gr. N) 10.79 ± 1.03, Gr. S) 14.15 ± 3.07, Gr. L) 14.11 ± 1.98. The treatment of zirconia surface were significantly affected to shear bond of resin adhesive to zirconia (p 0.05). Conclusion: Pretreatment of zirconia by Er-YAG laser improved bond strength to resin cement. The study suggested that Y-TZP ceramics should be treated surface with Er-YAG laser before cementation. Keywords: Zirconia; Resin Cement; Er-YAG Laser; Shear Bond Strength

The effect of primers on shear bond strength of acrylic resins to different types of metals

The purpose of this study was to investigate the effects of carbon dioxide (CO2) and Erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiations on the shear bond strength (SBS) of differently sintered zirconia ceramics to resin cement. Eighty zirconia specimens were prepared, sintered in two different periods (short = Ss, long = Ls), and divided into four treatment groups (n = 10 each). These groups were (a) untreated (control), (b) Er:YAG laser irradiated with 6 W power for 5 sec, (c) CO2 laser with 2 W power for 10 sec, (d) CO2 laser with 4 W power for 10 sec. Scanning electron microscope (SEM) images were recorded for each of the eight groups. Eighty composite resin discs (3 × 3 mm) were fabricated and cemented with an adhesive resin cement to ceramic specimens. The SBS test was performed after specimens were stored in water for 24 h by an universal testing machine at a crosshead speed of 1 mm/min. Data were statistically analyzed with two way analysis of variance (ANOVA) and Tukey honest significant difference (HSD) test (α = 0.05). According to the ANOVA, the sintering time, surface treatments and their interaction were statistically significant (p < 0.05). Although each of the laser-irradiated groups were significantly higher than the control groups, there was no statistically significant difference among them (p > 0.05). Variation in sintering time from 2.5 to 5.0 h may have influenced the SBS of Yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics. Although CO2 and Er:YAG laser irradiation techniques may increase the SBS values of both tested zirconia ceramics, they are recommended for clinicians as an alternative pretreatment method.

Effects of Nd: YAG LASER irradiation and O2 plasma on the adhesive performance of poly-ether-ether-ketone (PEEK)

Introduction Brackets can be recycled by sending them to a commercial recycling company but it is time consuming and the bracket cannot be bonded in the same appointment. Hence in-house methods for recycling of brackets would be beneficial to both the orthodontist and the patient. Aim In our study, we compared the shear bond strength of brackets after being recycled with erbium-doped yttrium aluminum garnet (ER:YAG) laser, sandblasting and the thermal method. Materials and Methods The study was carried out on 126 extracted premolars. The bonding procedure was performed with mandibular premolar metal and premolar ceramic brackets. Eighty-four teeth were subdivided into three groups for each method of recycling. These groups were further subdivided into two groups of 14 teeth each for the types of brackets used. Prior to the initial bonding the bracket was also viewed under an environmental scanning electron microscope to examine the meshwork of the brackets and once again after the respective recycling methods had been performed. Results We found that for stainless steel brackets, the sandblasting method was superior to the ER:YAG laser, as the recycled brackets showed a higher shear bond strength. For ceramic brackets the ER:YAG laser recycled group had the highest recycled shear bond strength therefore was the best method of recycling ceramic brackets.

Although acid etching is routinely used to condition tooth surfaces, it increases the caries susceptibility of enamel and enhances enamel demineralization; thus the role of alternative surface treatments such as alumina air abrasion and erbium-doped yttrium aluminium garnet (Er:YAG) laser irradiation for tooth conditioning is controversial. This study was undertaken to compare the effects of different conditioning methods on the shear bond strength (SBS) of resin cement on enamel and dentin. Prepared permanent human dentin and enamel samples (N = 210) embedded in clear acrylic resin were conditioned by 37% phosphoric acid etching, 50-µm alumina air abrasion, Er:YAG laser irradiation (120 mJ, 10 Hz, medium short pulse mode), or their combinations. Porcelain laminates were cemented by using photopolymerizing luting composite. SBS was evaluated after thermal cycling (10,000 cycles, 5–55°C) and fracture types (adhesive, cohesive, or mixed) were observed by stereomicroscopy. Data were analyzed by Kruskal–Wallis analysis of variance and followed by Tamhane's test (p < 0.05). Enamel and dentin specimens showed significant differences in SBS (p < 0.000). Er:YAG laser etching presents successful alternatives to acid etching on dentin surfaces; it does not enhance adhesion of the resin cement on enamel surfaces.

Effect of different surface conditioning methods and low pH solutions on the shear bond strength of orthodontic brackets to newly introduced CAD/CAM materials

To compare the effect of laser irradiation at two different pulse settings and acid etching on the shear bond strength (SBS) of orthodontic brackets to enamel. Thirty-six premolars were allocated to three groups (n = 12): (1) 37% phosphoric acid etching, (2) erbium-doped yttrium aluminum garnet (Er:YAG) laser etching with medium-short pulse mode (MSP; 100 µs, 120 mj, 10 Hz, 1.2 W), and (3) Er:YAG laser etching with quantum-square pulse mode (QSP; 120 mj, 10 Hz, 1.2 W). Metallic brackets were bonded with Transbond XT. After photopolymerization, the samples were subjected to 5000 thermal cycles and debonded with a universal testing machine, and the SBS values were recorded. Surface morphology was evaluated with profilometric examination, scanning electron microscopy, and atomic force microscopy. The adhesive remnant index (ARI) was evaluated to assess the remaining adhesive. The results of SBS testing were analyzed by one-way analysis of variance and Tukey honestly significant diffference tests. The mean SBS values of QSP and MSP laser groups were 11.80 ± 2.7 MPa and 10.10 ± 4.5 MPa, respectively, and the QSP group demonstrated significantly higher SBS (P < .01) than that of the acid-etched group (6.6 ± 2.4 MPa). No significant difference was observed between the SBS values of the two laser groups (P < .05). The difference between the ARI scores of the laser groups and the acid-etched group was statistically significant (P < .05). Laser etching at MSP and QSP modes present successful alternatives to acid etching; however, long-term clinical studies are required to verify clinical success.

Introduction: Polyether ether ketone (PEEK) has low surface energy and high resistance to chemical surface treatments. Therefore, different surface treatments such as laser conditioning should be investigated. There is a gap of information regarding the efficacy of laser irradiation in the surface treatment of PEEK, and the efficacy of several laser types needs to be evaluated for this purpose. This study aimed to assess the effect of surface treatment with erbium-doped yttrium aluminum garnet (Er:YAG) and carbon dioxide (CO2) lasers on shear bond strength (SBS) of PEEK to composite resin veneers. Methods: In this experimental study, 60 rectangular-shaped PEEK samples (7 x 7 x 2 mm) were used. The samples were mounted in auto-polymerizing acrylic resin in such a way that only one surface measuring 7x7 mm remained exposed. The samples were then randomly divided into 3 groups (n=20) of control, Er:YAG laser surface treatment (Power=1.5 W, energy density=119.42 J/cm2 , irradiation time=20 s) and CO2 laser surface treatment (Power=4 W, energy density=159.22 J/cm2 , irradiation time=50 s). The bonding agent and PEEK opaque were applied on the surface of samples and they were veneered with a composite resin using a hollow plastic cylinder with an internal diameter of 4 mm. The SBS was then measured and the data were analyzed using one-way ANOVA, Tukey HSD test and Dunnett's test at 0.05 level of significance. Results: The SBS of the 3 groups was significantly different (P<0.001). The Tukey HSD test revealed that the Er:YAG laser had higher SBS than the CO2 laser group (P<0.001). The Dunnett's test showed that both Er:YAG and CO2 laser groups yielded higher SBS than the control group (P<0.001). Conclusion: The Er:YAG and CO2 laser treatments can increase the SBS of PEEK to composite resin veneers, although the Er:YAG laser seems to be more effective for this purpose.

Objectives: The aim of the present study was to investigate the shear bond strength of orthodontic brackets to zirconium oxide infrastructures treated with erbium-doped yttrium aluminum garnet (Er:YAG), neodymium-doped yttrium aluminum garnet (Nd:YAG) and potassium titanyl phosphate (KTP) laser modalities in in vitro settings. Materials and Methods: A total of 40 zirconium oxide infrastructures were prepared with CAD/CAM technology in accordance with ISO 11405 standard. The specimens were divided into 4 groups as following: Er:YAG, Nd:YAG, KTP, and control groups (n=10). Prior to the application of cementation of orthodontic brackets, the surfaces of the zirconium oxide infrastructures were irradiated using selected laser modailites. Shear bond strength tests were performed on each specimen by using a universal testing machine. Results: The shear bond strength value of Er:YAG laser group was significantly higher than those of all other groups (p&amp;lt;0.05); although the bonding strength of Nd:YAG laser was higher than that of the KTP laser, this difference was not reached statistical significance (p&amp;gt;0.05). The bonding strength values of Nd:YAG laser group were significantly higher than that of the control group (p&amp;lt;0.05); and the the bonding strength values of KTP laser group were significantly higher than that of control group (p&amp;lt;0.05). Conclusion: The bond strength between the orthodontic brackets and zirconium oxide infrastructures was improved upon using all the laser modalities in the present study, among which, application of the Er:YAG laser was the most successful.

The purpose of the present study was to evaluate the shear bond strength of orthodontic brackets bonded to porcelain following etching with erbium-doped yttrium aluminum garnet (Er:YAG) laser compared with 9.6% hydrofluoric acid (HF). A total of 100 porcelain disk samples were divided into four groups, and after removing their glazed layer, the first group was etched with 9.6% HF, and the other three groups were etched with Er:YAG lasers of 1.6, 2, and 3.2 W, respectively. After application of silane on the disk surfaces, central incisor brackets were bonded with composite on the disks. The disks were mounted on an acrylic stand for measuring the shear bond strengths. The shear bond strengths were measured by a testing machine. The mean shear bond strength in the laser group with power of 1.6 W (7.88 MPa) was more than that of the HF (7.4MPa), 2-W power (7.52 MPa), and 3.2-W power (7.45 MPa) groups, but this difference was not statistically significant. Examination with an electron microscope showed different patterns of etching by HF and laser. Also, etching by laser and HF had not resulted in cracks on the porcelain surface. Er:YAG laser can be a suitable method for bonding of orthodontic brackets to porcelain surfaces.

Effect of resin cement viscosities and surface roughness on shear bond strength of conditioned polymer infiltrated ceramic network

The purpose of this study was to investigate the effect of Erbium-doped yttrium aluminium garnet laser laser (Er: YAG laser), sandblast and several universal bonding on the shear bond strength of zirconia ceramic to composite resin. In this experimental study, 96 Y-TZP disks were used. They were divided into six groups based on surface preparation: 1-Er: YAG laser + single bond universal/ 3M, 2-Er: YAG laser + all bond universal/bisco, 3-Er: YAG laser + G-premio bond/GC, 4-sandblast + single bond universal/3M, 5-sandblast + all bond universal/bisco, 6-sandblast + G-Premio bond/GC; in the next step, composite discs were cured on the surface of the zirconia discs and their shear bond strength was evaluated using a mechanical test machine (universal testing machine). Two-way ANOVA showed that the surface preparation had a significant statistical effect on shear bond strength (p< 0.001). There was no association between these two variables with regards to the interaction of bonding and surface preparation (p = 0.064). Tukey's test showed that the shear bond strengths in the sandblast type group did not differ significantly between the groups according to the type of universal bonding, as well as in the Er: YAG laser treated group by type Universal bonding which was not significantly different between the groups of single bond universal and all bond universal, but there was a significant difference between the groups in terms of single bond universal and G-Premio, as well as all bond universal and G-Premio. Based on the results, the preparation of Er:YAG laser is a more appropriate method for increasing bond strength when compared with sandblasting, and among the universal bonding, G-Premio is also more suitable for this purpose. The present data indicate that bond strength of laser preparation and G-Premio adhesive might be reliable for clinical application Keywords: Er: YAG Laser, Sandblasting, Shear bond strength, Universal bonding.

Introduction: Providing reliable bonding of the bracket base and the zirconia surface is required to apply orthodontic force. The purpose of this scientific experiment was to evaluate the efficacy of three different methods of surface preparation for Zirconia, including surface roughening, sandblasting and the Nd: YAG laser, in the shear bond strength (SBS) of the orthodontic brackets. Methods: Fifty-four discs of zirconia were divided into three groups of 18: A) Hydrofluoric acid etching, B) sandblasting, and C) Nd: irradiation using the power of 1.5 W for 10 seconds. After bonding the brackets, the samples were slowly thermo-cycled (1000 times) for 24 hours. The SBS test was performed by a universal testing machine at a head speed of 0.5 mm/min. The adhesive remnant index (ARI) was scored at a magnification of 10 in the stereo microscope. All data were collected and analyzed using the variance, Kruskal-Wallis, Tukey, Don, and Weibull tests (α = 0.05). Results: The HF acid etching group (6.11± 0.94 MPa) had the highest SBS, which was followed by the laser group (6 ± 0.61 MPa) and the sandblast group (3.1080 ± 0.82 MPa). There was a significant statistical difference between the laser and HF groups and the sandblast group (P < 0.05) and no significant difference between the HF group and the laser group (P = 0.03). Conclusion: Based on the obtained bond strength, the Nd: YAG laser with a power of 1.5 W could be a substitute treatment method for the HF acid-etching.