To achieve proper bond strength for porcelains, adequate surface roughness is essential, which is traditionally gained by sandblasting or acid etching with hydrofluoric (HF) acid. Nowadays with the development of laser systems, serious efforts were made to apply this new instrument for surface etching of porcelains due to easy usage, safety, and more efficiency. There are different kinds of lasers and porcelains, so choosing the ones which will be good match for each other is crucial. Besides that, changing the irradiation setting can be beneficial as well. This article reviewed 33 related studies and summarized results of etching accomplished by Nd:YAG, Er:YAG, Er,Cr:YSGG and CO 2 lasers on different types of porcelains considering different laser settings and evaluation methods to bring a comprehensive insight.

This study investigated the effect of Er:YAG (smart 2940 Dplus, DEKA, Italy) and Er:CrYSGG (Waterlase iPlus, Biolase, USA) lasers on the shear bond strength (SBS) between the orthodontic brackets and dental porcelain in comparison with conventional acid etching with 9% hydrofluoric acid (HF, Ultradent, USA). A total of 60 specimens of maxillary incisor crown were prepared and randomly assigned to five groups; each group was subjected to a different porcelain surface conditioning: (1) etching with the 9% HF for 2 min; (2) etching with the 9% HF for 2 min followed by irradiation with the Er:CrYSGG laser (3-W power, 10-Hz frequency for 10 s); (3) etching with the 9% HF for 2 min followed by irradiation with the Er:YAG laser (3-W power, 10-Hz frequency for 10 s); (4) Irradiation with the Er:CrYSGG laser (3-W power, 10-Hz frequency for 10 s without acid etching) and (5) irradiation with the Er:YAG laser (3-W power,10-Hz frequency for 10 s without acid etching). After using Transbond XT primer and Transbond XT adhesive, the metal brackets (Dentaurum, Germany equilibrium 2, optimal design) bonded to the conditioned porcelain surface. Subsequently, the specimens were thermocycled for 5000 cycles and then debonded using the Universal Testing Machine (Zwick). In each group, one specimen was not bonded to brackets to allow further examination with electron microscopy. After debonding, the specimens were examined by stereomicroscope to determine their adhesive remnant index (ARI). The average SBS [Mean (SD)] values in the five groups were as follows: HF (32.58 ± 9.21 MPa), Er:CrYSGG + HF (27.81 ± 7.66 MPa), Er:YAG + HF (23.08 ± 9.55 MPa), Er:CrYSGG (14.11 ± 9.35 MPa), and Er:YAG (6.30 ± 3.09 MPa). A statistically significant difference in SBS existed between the first three groups and the two laser groups (df = 4, F = 18.555, p < 0.001). Evaluation of ARI values showed that bond failures in the first three groups were mostly of cohesive and mixed types, but in the laser groups, they were mostly adhesive. Chi-square was not significant between groups (p = 0.219). The Er:YAG laser with the stated specifications is not a suitable alternative to HF etching. In the case of Er:CrYSGG laser, although the conditioning outcome met the bond strength requirement for orthodontic brackets (that is, 6-8 MPa). Therefore, the bond strength must be further improved by fine-tuning the irradiation details.

Several techniques have been proposed to obtain a durable bond, and the efficacy of these techniques is assessed by measuring parameters such as bond strength. Laser has provided a bond strength as high as that of acid etching in vitro and has simpler use with shorter clinical time compared to acid etching. This study aimed to compare the efficacy of Er:YAG and Er,Cr:YSGG lasers for etching and bonding of composite to orthodontic brackets. No previous study has evaluated the effect of these particular types of laser. A total of 70 composite blocks were randomly divided into five groups (n = 14): group 1, etching with phosphoric acid for 20 s; group 2, Er:YAG laser irradiation with 2 W power for 10 s; group 3, Er:YAG laser with 3 W power for 10 s; group 4, Er,Cr:YSGG laser with 2 W power for 10 s; group 5, Er,Cr:YSGG laser with 3 W power for 10 s. Metal brackets were then bonded to composites, and after 5000 thermal cycles, they were subjected to shear bond strength test in a universal testing machine after 24 h of water storage. One sample of each group was evaluated under a scanning electron microscope (SEM) to assess changes in composite surface after etching. The adhesive remnant index (ARI) was calculated under a stereomicroscope. Data were statistically analyzed. The mean and standard deviation of shear bond strength were 18.65 ± 3.36, 19.68 ± 5.34, 21.31 ± 4.03, 17.38 ± 6.94, and 16.45 ± 4.26 MPa in groups 1-5, respectively. The ARI scores showed that the bond failure mode in all groups was mainly mixed. The groups were not significantly different in terms of shear bond strength. Er:YAG and Er,Cr:YSGG lasers with the mentioned parameters yield optimal shear bond strength and can be used as an alternative to acid etching for bracket bond to composite.

The aim of this study was to investigate orthodontics brackets shear bond strength (SBS) after pretreatment of bleached enamel surface with different laser types in comparison with antioxidants agent. A total of 150 sound human premolars were randomly assigned to into a control group which was experimental group (Group A) as bleached with 40% HP bleaching agent and not bleached (Group B). Then, both control and experimental groups were divided into five subgroups.Subgroup 1: no surface treatment Subgroup 2: treated by Nd:YAG laser (1 W, 100 µs, 10 Hz) for 30 s. Subgroup 3: treated by Er: YAG laser (0.5 W, 230 µs, 10 Hz, 5 mm distance) for 30 s. Subgroup 4: treated by CO 2 laser (0.5 W, 10 Hz, pulse width of 1 ms) for 30 s. Subgroup 5: conditioned by 10% sodium ascorbate solution for 10 min.Then, the metal premolar brackets were bonded to conditioned enamel surface. All the specimens were debonded using the Universal Testing Machine. The data were analyzed by One-way analysis of variance and the Tukey's HSD. The SBS values of brackets bonded to bleached enamel in subgroup 1(no surface pretreatment) and 2(surface pretreatment with Nd:YAG laser) were significantly lower than subgroup 3(surface pretreatment with Er: YAG laser) and subgroup 4 (surface pretreatment with CO 2 laser). The lowest SBS belonged to brackets bonded to bleached enamel in the subgroups 1 and 2, also the SBS values in subgroup 2 and subgroup 3 were significantly higher than subgroup 5. Pretreatment with Er: YAG and CO 2 laser will improve SBS on bleached enamel surface more efficiently than surface pretreatment with Nd:YAG laser or antioxidant agent.

Among the different methods of etching in orthodontic procedures, phosphoric acid etching is the most widely used method with the best bonding affinity, but it has its own drawbacks. To overcome these shortcomings new methods have been developed, among which laser-based approaches are of great importance due to ease of use and few side effects. In this study, the bonding strength of an Er:YAG laser was compared with those of acid etching and self-etching primers for the bonding of orthodontic brackets.One hundred teeth were randomly divided into five groups to evaluate the properties of each different adhesive system: acid etching, self-etching, Er:YAG laser etching, Er:YAG laser etching + self-etching and Er:YAG laser etching + acid etching. Adhesive remnant index (ARI) scores and shear bond strength (SBS) data were analyzed using the Kruskal-Wallis test and ANOVA test, respectively.The results of the ANOVA test implied that a significant difference exists between the mean SBS values of the study groups, where the acid-etched groups have the highest bond strengths. The results show that a statistically meaningful difference exists between the ARI scores of the groups.The results of this study imply that acid etching is the best etching method with regards to bonding strength, but the Er:YAG laser has acceptable bonding strength.