Effect of low fluency dentin conditioning on tensile bond strength of composite bonded to Er:YAG laser-prepared dentin: a preliminary study

Abstract

Several studies in the literature have previously shown that the bond strength of a composite bonded to dentin is almost equivalent as when dentin is prepared by either bur or Er:YAG laser. The aim of this preliminary study is to assess the hypothesis that dentin conditioning at low fluency by means of Er:YAG laser can improve the value of adhesion of composites resin to dentin. Sixty surfaces of caries-free human third molars extracted for orthodontic purposes were randomly divided into five groups of 12 teeth. The bur group was the control, prepared using bur, group L was prepared using Er:YAG 200 mJ, SSP (50 µs), 20 Hz, 15 seconds of sweeping, for groups L80, L100, L120, they were prepared first, with the same parameters of the group L 200, and then they received a conditioning, which is, respectively, 15 s of irradiations at: 80 mJ (SSP, 10 Hz), 100 mJ (SSP, 10 Hz), and 120 mJ (SSP, 10 Hz). All samples were restored in a single-component adhesive system: Xenon (DENTSPLY), and ceramX (DENTSPLY) as the resin composite. The specimens were submitted to tensile bond strength test using a universal testing machine. Data were submitted to statistical analysis using ANOVA coupled to a Tukey-Kramer test at the 95% level. The mean values in MPa were 33.3 for group B, 36.73 for group L 200, 41.7 for group L80, 37.9 for group L100, and 39.1 for group L120. Our results showed that dentin conditioning at a low fluency of 12.58 J/cm(2) per pulse, with 80 mJ output energy and 50-µs pulse duration can significantly improve tensile bond strength of a composite bonded to Er:YAG laser-prepared dentine.

Impact of Er:YAG laser pulse duration on ultra-structure of dentin collagen fibrils

“…This technique provides a more comfortable treatment for the patient by reducing stress and vibration and allows ultra-conservative cavity preparations [7] as claimed in modern dentistry.…”

Long-term effect of Er:YAG laser on adhesion to caries-affected dentin

“…These cracks result from the increased pressure in the dentin subsurface due to water vaporization and subsequent ejection of organic material due to the ablation process [27]. When using a 50-μs pulse duration, fewer microcracks were expected [7,15]. It is important to note that these findings do not seem to compromise the long-term results of BS and NdHL.…”

“…These parameters were selected based on other studies [7,20] that revealed satisfactory results using an energy density of 13.33 J/cm 2 (laser 1). The results of those studies suggested the need to test the effectiveness of even lower energy densities for pretreating dentin prior to adhesive procedures; therefore, an energy density of 8.33 J/ cm 2 (laser 2) was also chosen [7]. Both Er:YAG laser surface pretreatment protocols in both substrates did not alter the BS of CF for both evaluation periods tested.…”

“…At shorter (50-μs) pulse durations, the output energy is fully absorbed by the target tissue with no or minimal heat created in the underlying tissue [12], less thermal damage [13][14][15], and shorter irradiation time. The reduced heat propagation into dentin can reduce the risk of micro-crack formation and collagen fibril denaturation [16], suggesting that a shorter pulse duration could be a better protocol for irradiating dentin where bonding will be performed [7], as unaltered collagen is key to effective hybrid layer formation and its durability.…”

“…Moreover, specific pretreatment (prior to adhesive procedures) parameters ablate sound dentin both macro-and microscopically, resulting in an irregular, smear layer-free dentine with open dentinal tubules, which is thought to be more prone to resin tag formation and thus more receptive to adhesion [7]. The question is whether it also occurs in CAD; to date, most of the studies using Er:YAG laser pretreatments focused on bonding to sound dentin-only a few studies used CAD [8].…”