Effect of Er:YAG laser and diamond drill on hybrid layer morphology obtained with self-etch adhesive – analysis by SEM and confocal laser scanning microscopy (CLSM)

Resumo

This study aimed to evaluate the
effect of Er:YAG (L) and diamond drills (DD) on: 1) the microshear
bond strength (MPa); 2) the adhesive interface of two-step (TS)
– Adper Scotchbond Multipurpose and one-step (OS) adhesives
– Adper EasyOne, both from 3M ESPE. Material and methods:
According to the preparation condition and adhesives, the samples
were divided into four groups: DD_TS (control); DD_OS; L_TS and
L_OS. 60 bovine incisors were randomly divided into experimental
and groups: 40 for microshear bond strength (n = 10) and 20 for
the adhesive interface morphology [6 to measure the thickness of
the hybrid layer (HL) and length of tags (t) by CLSM (n = 3); 12
to the adhesive interface morphology by SEM (n = 3) and 2 to
illustrate the effect of the instruments on dentine by SEM (n = 1)].
To conduct the microshear bond strength test, four cylinders (0.7
mm in diameter and 1 mm in height with area of adhesion of
0.38 mm) were constructed with resin composite (Filtek Z350 XT – 3M ESPE) on each dentin surface treated by either L or DD and after
adhesives application. Microshear bond strength was performed in
universal testing machine (EMIC 2000) with load cell of 500 kgf and a
crosshead speed of 0.5 mm / min. Adhesive interface was characterized
by thickness of hybrid layer (HL) and length of tags (t) in nm, with the
aid of UTHSCSA ImageTool software. Results: Microshear bond strength
values were: L_TS 34.10 ± 19.07, DD_TS 24.26 ± 9.35, L_OS 33.18 ±
12.46, DD_OS 21.24 ± 13.96. Two-way ANOVA resulted in statistically
significant differences only for instruments (p = 0.047). Mann-Whitney
identified the instruments which determined significant differences for
HL thickness and tag length (t). Concerning to the adhesive types, these
differences were only observed for (t). Conclusion: It can be concluded
that 1) laser Er:YAG results in higher microshear bond strength values
regardless of the adhesive system (TS and OS); 2) the tags did not
significant affect the microshear bond strength; 3) the adhesive interface
was affected by both the instruments for cavity preparation and the type
of adhesive system used.