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rev port estomatol med dent cir maxilofac . 2021;62(1):16-22 21

groups suffered a substrate failure. This observation has im- Overall, the weakest adhesive link was found at the acrylic-
portant clinical implications, particularly during the removal -adhesive interface, and the cohesive failures observed were
of brackets bonded to sandblasted PMMA temporary crowns, associated with surface treatment with ASB.
as the risk of crown fracture is considerable.
The literature is inconclusive regarding the effects of ap-
plying the MMA monomer to PMMA surfaces and its effective Acknowledgements
application time. Several exposure times to MMA have been
proposed, from 15 to 60 33,34 to several minutes. 35,36 Some au- The authors thank ORMCO, 3M, and Ivoclar Vivadent for the
35
thors stated that, with a 180 -second application, MMA dis- donation of products used in the study.
solves the surface structure of PMMA, increasing its potential
for chemical adhesion. According to other researchers, 37 the
surface of dissolved PMMA provides free bonds that can copo- Ethical disclosures
lymerize with composite resin. The polymerization process of
MMA and composite matrix (Bis -GMA) follows a similar pat- Protection of human and animal subjects. The authors
tern of activation and cross -linking since the molecules’ reac- declare that no experiments were performed on humans or
tive methacrylate groups are similar. Thus, chemical adhesion animals for this study.

could occur.
However, this study’s results showed that the tested adhe- Confidentiality of data. The authors declare that no patient

sive systems do not ensure clinically effective PMMA bracket data appear in this article.
adhesion, even when applying MMA for 25 seconds. In the Right to privacy and informed consent. The authors declare
absence of mechanical surface treatment, adhesion was very that no patient data appear in this article.
weak for both adhesive systems, suggesting that neither could
achieve a chemical bond between the composite and the
PMMA. No differences were found between adhesive systems, Conflict of interest
a result that was similar to a previous study using PMMA and
sandblasting treatment. 38 The authors have no conflicts of interest to declare.
Regarding the type of failure, ARI 1, which corresponds to
the largest amount of adhesive on the bracket base, was pre-
dominant in the groups submitted to sandblasting; this is in references
line with a previous report. However, another study found 1. Kokich VG, Spear FM. Guidelines for managing the
14
22
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served; these correspond to the acrylic -adhesive interface’s Koutsoukis T, Zinelis S. Effects of surface treatment and
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39
and forces acting in various directions. Although thermocy- 6. Jardim L. Estudo da adesão de brackets ortodônticos a
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According to the objectives of this study, it can be concluded methods on the shear bond strengths of orthodontic
that bracket adhesion to PMMA was lower than adhesion to brackets. Photomed Laser Surg. 2015;33:55 -60.
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