Abstract
Objective: To evaluate the shear bond strength of orthodontic accessories bonded to a porcelain surface after storage in water.Methods: One-hundredand-twenty feldspathic porcelain discs were divided into 4 groups, according to the surface treatment: Group 1 – 37% phosphoric acid etching; Group 2 – 10% fluorhydric acid; Group 3 – 37% phosphoric acid and silane application; Group 4 – 10% fluorhydric acid and silane application. After the accessories were bonded, the sample was divided into two subgroups, according to the time interval of storage in distilled water: Control – 24 hours; and Test – 150 days. Shear bond strength was determined using a universal test machine, and failure type was verified by scanning electron microscopy.Results: In the test groups there was reduction in shear bond strength, particularly when silane was used. Test Groups 2 and 4 presented shear bond strength values within those proposed as adequate for orthodontic bonding. Groups 1 and 3 presented adhesive failures between porcelain and resin, whereas in Groups 2 and 4 cohesive failures in porcelain were recorded.Conclusion: Storage in water for 150 days decreased the bond strength at silanized interfaces. Fluorhydric acid etching generates adequate bond strength in wet conditions, however, increases the fracture rate in porcelain.
Highlights
The increasing number of adult orthodontic patients has led to challenges for Dentistry professionals, as they are increasingly faced with the need for bonding orthodontic accessories to surfaces that differ from tooth enamel, such as in the case of restorations with porcelain surfaces [1,2]
The images were classified as regards type of failure resulting from accessory debonding, as described below: – Cohesive in porcelain (CP) – in the case of fractures or cracks in the porcelain surface; – Adhesive (A) – in the case when there was no failure in porcelain, or resin remainder on the porcelain surface, and all the resin was retained on the base of the orthodontic accessory; or when all the resin was adhered to the porcelain surface, without any remainder on the orthodontic accessory; – Cohesive in resin (CR) – in the case when there was a resin remainder on the porcelain surface and at the base of the orthodontic accessory
A highest bond strength value was observed in Control Group 4, while in the test group the use of fluorhydric acid resulted in greater bond strength, irrespective of the use of silane (p
Summary
The increasing number of adult orthodontic patients has led to challenges for Dentistry professionals, as they are increasingly faced with the need for bonding orthodontic accessories to surfaces that differ from tooth enamel, such as in the case of restorations with porcelain surfaces [1,2]. In Orthodontics, orthodontic accessory bonding is temporary, the bond strength must be sufficient to resist the forces applied during treatment, and on the other hand, fragile enough to allow debonding at the end of treatment, without damaging the teeth and the restorations they may present [3]. There are many protocols proposed in the literature for bonding orthodontic accessories to porcelain surfaces, and they vary right from the different acids applied for various periods of time through to airborne particle abrasion or application of bonding agents such as silane. The aim of this study was to evaluate, in vitro, the shear bond strength of orthodontic accessories bonded to a porcelain surface under different bonding protocols, after storage in water, and the type of failure remaining on the porcelain surface after debonding of these accessories, in the different groups studied. The null hypothesis is that the humidity does not alter the shear bond strength between the orthodontic appliance and the porcelain surface in the experimental groups
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