Ultrashort pulsed laser conditioning of human enamel: in vitro study of the influence of geometrical processing parameters on shear bond strength of orthodontic brackets

Abstract

The surfaces of 63 extracted premolar teeth were processed with intense ultrashort laser pulses (λ = 795 nm; pulse duration, 120 fs; repetition rate, 1 kHz) to produce cross patterns with different pitches (s) in the micrometer range in order to evaluate the influence of such microstructures on the shear bond strengths of orthodontic brackets to enamel. The samples were classified in nine groups corresponding to the control group (raw samples) and eight different laser-processed groups (cross patterns with s increasing from 15 to 180 μm). Brackets were luted with Transbond(TM) XT adhesive resin to all the samples; after 72 h, they all were submitted to strength test in a universal testing machine. Additionally, a third of the samples underwent morphological analysis of the debonded surface by means of scanning electron microscope microscopy and an analysis of the failure mode based on the adhesive remnant index. The results showed that enamel microstructuring with ultrashort laser pulses remarkably increase the bond strength of brackets. Dense cross patterns (s < 90 μm) produce the highest increase of bond strengths as compared to control group whereas light ones (s > 90 μm) give rise to smaller improvements of the bond strength. A strong correlation of this behavior with the predominant failure mode in both scenarios was found. So far, the best compromise between suitable adhesive efficiency, processing time minimization, and enamel surface preservation suggests the performance of cross patterns with pitches in the order of 90 μm.

The Effect of Femtosecond Laser Treatment on the Effectiveness of Resin-Zirconia Adhesive: An In Vitro Study

“…Also, in the APA25 group, alumina particle sandblasting created a rough surface ( Figure 1D), but the surface irregularities had insufficient micro depth and therefore both groups exerted less mechanical retention than the FS group ( Figure 1H) and TSC group ( Figure 1F). In recent studies 27,28 an abrasion pattern similar to that obtained in our study when applying femtosecond laser on the enamel surface, also showing increased adhesive efficiency, has been reported. The use of a femtosecond laser may be valid for conditioning enamel and zirconia surfaces, as we showed here.…”

“…The use of a femtosecond laser may be valid for conditioning enamel and zirconia surfaces, as we showed here. Thus, the irradiation with femtosecond lasers is increasingly supported as an alternative in the field of adhesion in dentistry, replacing drills in conservative dentistry 33 and also serving as both a conditioning agent and for the ablation of different types of surfaces -whether they are biological, such as the enamel 27,28 or dentine, 34 or non-biological, such as porcelain 29 or zirconia, as in the present case-with a minimum amount of thermal and mechanical damage to the surfaces. 35,36 The TSC group had SBS values close to those of the FS group.…”

“…It would be of great clinical use if femtosecond lasers could be employed to perform the conditioning of biological and non-biological surfaces on which elements are cemented in Dentistry. Some studies have already addressed the enamel-bracket interface, 27,28 obtaining encouraging results in the sense of improvements in adhesive effectiveness and the possibility of replacing traditional conditioning agents that cause biological damage to tooth enamel. Regarding adhesion to porcelain, in a recent study, the authors analyzed zirconia surface conditioning with a femtosecond laser to improve the porcelain-bracket interface.…”

Effect of Different Surface Treatments on Porcelain‐Resin Bond Strength

“…Ultrashort-pulse laser systems are not suitable for direct clinical use; however, many studies have reported on the bond strength of dental tissues subjected to treatments using a UPLS. 26,[37][38][39] Lorenzo et al 26 reported stronger bonding of brackets to enamel treated with a UPLS rather than other laser systems. The ablation from UPLS's is induced by a plasma, which imparts less thermal damage than do the longer pulses of ER:YAG lasers.…”

Comparative Evaluation of Shear Bond Strength of Flowable Composite Bonded to Teeth Enamel with Laser Surface Treatment

“…Investigation of enamel surface roughness showed that laser irradiation yielded a comparable or smaller amount of surface roughness than acid etching (Hess 1990, Arcoria et al 1993. With regard to bond strengths of restorative materials, some studies indicated that acid-etched teeth had significantly more bond strength than laser-Laser_etch teeth (Ariyaratnam et al 1997), whereas other demonstrated that laser etching (Melendez et al 1992, Walsh et al 1994, Shahabi et al 2014,Lorenzo et al 2015. These variations could be attributed to the different types of lasers or different irradiation parameters used because the laser-hard tissue interaction is dependent on wavelength and irradiation energy.…”