Background: Dental resin composites undergo chemical and mechanical degradation.
Thus, the orthodontist should evaluate aged composite restoration surfaces to select the appropriate
protocol to successfully bond orthodontics accessories.
Objective: This study evaluated the shear bond strength (σ) of metal (M) and ceramic (C) brackets
bonded to aged resin-based composite restorations (ACR) after different surface treatments.
Method: ACR specimens (N=160) were fabricated and divided into 8 experimental groups (n=20)
as follows: Mo (control)- M bonded to ACR; MA- M bonded to ACR after acid etching using 38%
phosphoric acid for 20 s (A); MB- M bonded to ACR after surface roughing using a twelve-bladed
bur (B); MBA- M bonded to ACR after B and A; Co (control)- C bonded to ACR; CA- C bonded to
ACR after A; CB- C bonded to ACR after B; CBA- C bonded to ACR after B and A. All specimens
were stored for 24h before σ testing. Data were statistically analyzed using one-way ANOVA and
Tukey post-hoc (α=0.05). Fracture surfaces were examined to determine the failure mode.
Results: The surface treatments (A, B and BA) produced similar σ values (p>0.05) to ACR when
using the same bracket type. M bracket showed greater σ than C bracket (p<0.05), probably because
of different mechanical retention inherent from bracket type. Inhomogeneous stress distribution
generated complex failures.
Conclusion: Considering the needs of an orthodontic treatment and the surface treatments evaluated,
sufficient bond strength was produced to ACR, irrespective of bracket type.
Keywords: resin-based composite, ceramics, metals, aged biomaterials
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