Abstract

Abstract Introduction In recent years, there has been an increasing demand for esthetic treatments, especially among orthodontic patients. Objective This study determined the fracture strength of monocrystalline and polycrystalline ceramic brackets of different manufacturers during archwire torque. Material and method Sixty ceramic brackets (Roth, right upper central incisors, 0.022 x 0.028-inch slot) were allocated into two groups (30 specimens per group) according to the type of ceramics: monocrystalline and polycrystalline. Subsequently, the groups were divided into three subgroups (n = 10) according to the manufacturer: Orthometric, Eurodonto and Ortho Technology. Sixty PVC cylinders were filled with chemically activated acrylic resin (CAAR), the brackets were fixed with CAAR onto the cylinder surface and the excess material was used to partially cover the base of the bracket. After 24h, the U-shaped wire base (0.019 x 0.025 inches; 6 mm height and width) was inserted into the bracket slot and fixed thereon with a stainless-steel wire. Vertical folds were made at the ends of the “U” to support the universal test machine chisel. The fracture strength test was performed at a speed of 1.0 mm/min until fracture into a universal test machine (Instron). The data were recorded, transformed into g.mm and submitted to two-way ANOVA followed by Tukey’s post-hoc test (SAS Institute Inc., Cary, NC, USA, version 9.3) (α=5%). Result Monocrystalline brackets showed a higher fracture strength than polycrystalline brackets, regardless of the manufacturer (p<0.05). The highest fracture strength values were observed in Ortho Technology and Orthometric brackets, with no significant difference between them (p>0.05). Conclusion Monocrystalline ceramic brackets have a higher fracture strength than polycrystalline brackets, with significant manufacturer-dependent differences.

Highlights

  • In recent years, there has been an increasing demand for esthetic treatments, especially among orthodontic patients

  • Ceramic brackets are composed of aluminum oxide (Al2O3), with a monocrystalline or polycrystalline structure fused at high temperatures[5]

  • Monocrystalline ceramic brackets showed a significantly higher fracture strength than polycrystalline brackets, which is in line with the reports by Vhanbatte et al.[15]

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Summary

Introduction

There has been an increasing demand for esthetic treatments, especially among orthodontic patients. Objective: This study determined the fracture strength of monocrystalline and polycrystalline ceramic brackets of different manufacturers during archwire torque. Polycarbonate brackets were the first of this kind to be commercialized[2] They did not have adequate mechanical behavior, presented color alterations, limited adhesiveness, low dimensional stability and a higher coefficient of friction when in contact with metallic wires[3]. To overcome these shortcomings, ceramic brackets were introduced in the dental market in the late 1980s4. Previous studies have shown that monocrystalline ceramic brackets have a higher fracture strength and translucency than polycrystalline brackets[4,6,7]. The manufacturing process plays an important role in the clinical performance of ceramic brackets as well as does the presence of pores, machining and propagation of cracks which may induce fracture of the bracket[9]

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