The critical bond strength of orthodontic brackets bonded to dental glass–ceramics
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To evaluate the critical bond strength (σ) of ceramic and metal brackets to a lithium disilicate-based glass–ceramic.
Materials and methods
Two hundred and forty ceramic specimens (IPS e-max CAD) were randomly distributed in 12 experimental groups (n = 20). Two ceramic brackets (monocrystalline, BCm; and polycrystalline, BCp) and a metal bracket (BM) were bonded to glass–ceramic specimens after one of the following surface treatments: HF—hydrofluoric acid applied for 60 s; S—silane applied for 3 min; HFS—HF followed by S; and MDP—application of an adhesive containing a phosphate monomer (MDP). All brackets were bonded to the treated glass–ceramic using a resin cement, stored in 37 °C water for 48 h before shear bond strength testing. Optical (OM) and scanning electron (SEM) microscopies were used for fractographic analysis. Data was statistically analyzed using Kruskal–Wallis and Student–Newman–Keuls (α = 0.05).
BCm bonded to glass–ceramic treated with either HFS or HF showed the highest median σ values, respectively, 10.5 MPa and 8.5 MPa. In contrast, the BCp bonded to glass–ceramic treated with MDP showed the lowest median σ value (0.8 MPa), which was not statistically different from other MDP-treated groups.
The failure mode was governed by the glass–ceramic surface treatment, not by the bracket type. Quantitative (σ values) and qualitative (fracture mode) data suggested a minimum of 5 MPa for brackets bonded to glass–ceramic, which is the lower critical limit bond strength for a comprehensive orthodontic treatment.
Bonding brackets to glass–ceramic requires micromechanical retention.
KeywordsAdhesion Ceramics Material strength Orthodontic brackets
The work was partially supported by Capes do Brazil and CNPq do Brasil (302587/2017-9).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
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