Effects of Water Flow Rate on Shear Bond Strength of Orthodontic Bracket Bonded to Enamel Surface After Er:YAG Laser Ablation

Effect of Er: YAG laser etching on shear bond strength of orthodontic bracket

OBJECTIVES

To evaluate and compare the shear bond strength (SBS) of Erbium laser etched enamel to acid etched and to detect morphological changes on laser etched enamel surface using scanning electron microscope (SEM). Moreover, Laser induced caries resistance is advantageous in Orthodontics.

METHODS

This is an Ex vivo study between January 2016 and December 2017, which comprises a total of 50 human premolars, extracted for orthodontic purpose, were used in this study. The samples were randomly divided into 2 groups of 25 each. The first group was etched using 37% phosphoric for 30 seconds. As for the second group, enamel was treated by Er: YAG laser operating at wavelength 2.94µm, power 1.5W and repetition rate 15Hz. Five teeth from each group were selected for SEM evaluation and the study were continued on 20 teeth from each group.Teeth were subjected to shear bond strength test.

RESULTS

It showed, no-significant difference between the mean of shear bond strength and of the etched groups (p=0.016).

CONCLUSION

It was concluded that, laser etched group (1.5W/15Hz) resulted in clinically accepted bond strength and could be an alternative to conventional acid etching.

Comparative study of the effect of Er:YAG and Er:Cr;YSGG lasers on porcelain: etching for the bonding of orthodontic brackets

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.

Comparative efficacy of Er,Cr:YSGG and Er:YAG lasers for etching of composite for orthodontic bracket bonding

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.

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.