Aim: To assess the Vickers hardness of plastic brackets, after in vitro aging. The morphology
and structure of corresponding retrieved brackets were also studied to assess the reliability
of in vitro set-up in imposing effects comparable to intraoral aging. Materials and
Methods: Four types of plastic brackets were selected. Specimens were immersed in a
buffer solution to induce artificial aging; brackets of two groups were retrieved after orthodontic
treatment. The wings of brackets were subjected to Knoop hardness testing, and
scanning electron microscopy was employed to study the morphology and microstructure
of retrieved brackets. The results were statistically analyzed by two-way analysis of variance
and Tukey test ( = 0.05). Results: Differences were identified between the brands of brackets,
but not between the new and in vitro-aged appliances. The retrieved appliances
showed significant reduction in hardness when compared with their as-received counterparts.
Evidence of degradation was seen in the retrieved appliances. Conclusions: The
inability of ex vivo experimental configuration to simulate clinical conditions is stressed;
several clinical implications related to torque control, friction, and tie-wing strength of
brackets are discussed. World J Orthod 2004;5:62–66.