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The Journal of Adhesive Dentistry
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J Adhes Dent 20 (2018), No. 5     16. Nov. 2018
J Adhes Dent 20 (2018), No. 5  (16.11.2018)

Page 417-424, doi:10.3290/j.jad.a41308, PubMed:30349906


Creep Behavior of Resin Composite Interface Between Orthodontic Brackets and Enamel
Durgesh, Bangalore H. / Alkheraif, Abdulaziz A. / Musaibah, Abobaker Salem / Asiry, Moshabab A. / Varrela, Juha / Vallittu, Pekka K.
Purpose: The present study investigated the creep of adhesive resin under constant loading at the orthodontic bracket/enamel interface with an orthodontic bracket-tooth model (shear creep) and three-point bending test (bending creep).
Materials and Methods: For the bracket-tooth model, sixty premolars were assigned to 4 groups (n = 15). Orthodontic brackets were bonded onto the enamel surface using four different bonding agents: conventional, homogeneous Transbond XT orthodontic composite (group 1/TBC); Transbond XT composite reinforced with photopolymerized glass-fiber-reinforced composite (FRC with bidirectional fibers) (group 2/TBE); Transbond XT reinforced with FRC of vertically oriented unidirectional fibers (group 3/TBV); and Transbond XT reinforced with FRC of horizontally oriented fibers (group 4/TBH). Load was applied at the bracket/tooth interface and from the bracket wire slot. In the three-point bending test, the creep and recovery of the rectangular interface materials were tested by a dynamic mechanical analyzer. The data obtained were statistically analyzed with ANOVA and a post-hoc test using SPSS v20 statistical software.
Results: The groups exhibited significant differences in strain % and time for bracket deflection at the interface (p < 0.05). The interface loading with unidirectional fibers (groups TBV and TBH) were statistically significantly different compared to the interface with bidirectional fibers and control group (groups TBE and TBC). The three-point test showed the least creep compliance (ie, creep deformation occurring at each time point [J]) with group TBC, followed by groups TBV and TBE. Group TBC showed the highest nanohardness and elastic modulus; the lowest values were seen in group TBE, reflecting differences in polymer matrix composition.
Conclusion: The creep and time for debonding the bracket increased with incorporation of glass fibers at the interface between bracket and enamel.

Keywords: adhesive resin, fiber reinforced composites, interpenetrating polymer network, cross linking, creep, recovery