Evaluation of Shear Bond Strength of Different Orthodontic Tubes

  • Dr Abilio Carvalho Neto, Lenza Institute for Postgraduate Studies, Brazil
  • Dr Rogerio Reges, Paulista University, Brazil
  • Dr Eduardo Lenza, University of São Paulo-Bauru/Lenza Institute for Posgraduate Studies, Brazil
  • Dr Florisberto Santos, Paulista University, Brazil
  • Dr Marcos Lenza, University of Goias School of Dentistry/Lenza Institute for Posgraduate Studies, Brazil

Objective: The purpose of this study was to evaluate the shear bond strength of several orthodontic tubes commonly used in the daily practice.
Material and Methods: First molar tubes from five different manufacturers were used in this study: Rocky Mountain Orthodontics, Ormco Corporation, 3M Unitek, G&H Wire Company and GAC. Six specimens from each group were bonded to bovine teeth using Transbond bracket adhesive system (3M Unitek). The tubes were debonded in shear at a cross-head speed of 5 mm/min in a EMIC testing machine, and the shear bond strength (SBS) calculated. The type of failure was visually determined. The numeric data were analyzed using three-way analysis of variance and Fisher test at p<.05.
Results: The mean SBS ranged from 4.51 MPa to 12.6 MPa. There was a significant difference in shear bond strength among the groups – in decreasing order: 3M Unitek, RMO, Ormco, GAC and G&H respectively (P < .0001). Bond failure for most specimens was of the cohesive type inside the composite resin layer (70%) and of adhesive type (30%)between bracket and the adhesive resin.
Conclusions: Shape and size of orthodontic tubes may be directly related to their bond strength. Despite significant statistical differences between the groups, all tubes were suitable for clinical use.