Abstract
ABSTRACTObjective: To evaluate the effect of silica dioxide (SiO2) nanofillers in different bonding systems on shear bond strength (SBS) and mode of failure of orthodontic brackets at two experimental times. Methods: Ninety-six intact premolars were divided into four groups: A) Conventional acid-etch and primer Transbond XT; B) Transbond Plus self-etch primer; and two self-etch bonding systems reinforced with silica dioxide nanofiller at different concentrations: C) Futurabond DC at 1%; D) Optibond All-in-One at 7%. Each group was allocated into two subgroups (n = 12) according to experimental time (12 and 24 hours). SBS test was performed using a universal testing machine. ARI scores were determined under a stereomicroscope. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to determine the size and distribution of nanofillers. One-way ANOVA was used to compare SBS followed by the post-hoc Tukey test. The chi-square test was used to evaluate ARI scores.Results: Mean SBS of Futurabond DC and Optibond All-in-One were significantly lower than conventional system, and there were no significant differences between means SBS obtained with all self-etch bonding systems used in the study. Lower ARI scores were found for Futurabond DC and Optibond All-in-One. There was no significant difference of SBS and ARI obtained at either time points for all bonding systems. Relative homogeneous distribution of the fillers was observed with the bonding systems.Conclusion: Two nanofilled systems revealed the lowest bond strengths, but still clinically acceptable and less adhesive was left on enamel. It is advisable not to load the brackets immediately to the maximum.
Highlights
Bonding to enamel has always been a challenge in dental materials; Buonocore pioneered the use of acidetch technique in 19551 and Newman was the first to recommend this technique in orthodontics.[2]
The mean shear bond strength (SBS) observed with all different bonding systems at 12 hours were not statistically significant, the mean SBS obtained with the conventional system was statistically significant higher than that observed with Optibond All-in-One bonding system at 24 hours (p < 0.05)
The combination showed that the SBS obtained with the two nanofilled systems used in this study were statistically significant lower than conventional system (p < 0.05), but there was no statistically significant difference between them
Summary
Bonding to enamel has always been a challenge in dental materials; Buonocore pioneered the use of acidetch technique in 19551 and Newman was the first to recommend this technique in orthodontics.[2] Despite the reliability and acceptability of phosphoric acid-etching technique, it is necessary to decrease the number of eroded enamel rods and reduce the chair time without affecting the bond strength.[3]. Self-etching primer (SEP) combining the acid-etching and primer have been introduced in orthodontics. Beside being a more simple and time-effective technique — by decreasing the bonding steps and dispensing the need for etching and priming —, it avoids the undesirable effects of acid-etching and prevents salivary contamination bonding failure.[4,5] traditional multi-procedures etch and prime systems have shown higher shear bond strength (SBS).[3,6]. Many theoretical predications based on the potential application of nanotechnology in dentistry have been made in the last 20 years, with varying levels of optimism.[9]
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