Micro‑shear bond strength of composite to deep dentin by using mild and ultra‑mild universal adhesives

Abstract

Background: Considering the increasing demand for tooth‑colored restorations, this study sought
to assess the micro‑shear bond strength (μSBS) of composite to deep dentin by using mild and
ultra‑mild universal adhesives.
Materials and Methods: This in vitro, experimental study evaluated 75 sound third molar teeth
randomized into five groups (n = 15) of Clearfil self‑etch (SE) Bond (control), Tokuyama Universal
Bond (TUB), and All‑Bond Universal (ABU) in etch and rinse (E and R) and SE modes. The occlusal
surfaces of the teeth were trimmed to expose deep dentin at 0.5 mm distance from the pulp
chamber. Adhesives were applied on the dentin surface according to the manufacturers’ instructions,
and Z350XT composite cylinders were bonded to dentin using Tygon tubes (0.9 mm internal
diameter, 2 mm height). After incubation at 37°C and 100% humidity for 24 h, the teeth underwent
μSBS test in a universal testing machine. The mode of failure was also determined under a
stereomicroscope. Analysis of variance, Bonferroni test, and Fisher’s exact test were applied for
data analysis (alpha = 0.05).
Results: TUB in E and R mode (13.78 MPa) and ABU in SE mode (7.85 MPa) yielded the maximum
and minimum μSBS values, respectively. No significant difference was noted in μSBS of tested
universal adhesives in E and R and SE modes to deep dentin (P > 0.05). TUB yielded significantly
higher μSBS than ABU (P < 0.05). No significant difference was noted in mode of failure of the
groups (P > 0.05).
Conclusion: Type of adhesive affected the μSBS but etching mode of universal adhesives had no
significant effect on their μSBS to deep dentin.
Key Words: Clearfil self‑etch bond, Composite Resins, Dentin, Dentin Bonding Agents, Shear
Strength