The effect of ultrasonic agitation on enamel bond strength of universal adhesives with light-cure versus self-cure activation: an in vitro comparative study

Introduction: Several variations of universal adhesives are available on the market, each with a unique curing method.However, it is unknown how application modes affect the adhesives' functionality. Objectives:The aim of the study was to compare the impact of ultrasonic agitation on micro-shear bond strength (SBS) of a self-cure universal adhesive system to enamel versus a light-cure universal adhesive system at different storage times.Material and methods: Based on the treatment mode (ultrasonic and manual), 48 specimens were divided into 2 major groups.Every major group was allocated to two sub-groups according to universal adhesive system: light-cure and self-cure.Then, every sub-group was evenly split according to storage times (3 and 6 months).After placing a specially designed silicon sheet above the occlusal surface and applying these 2 adhesive systems as per the manufacturer (manual group) or agitating the material with an ultrasonic device for 20 sec (ultrasonic group), the composite was inserted in sheet holes.SBS was assessed after two water storage intervals (3 and 6 months) using a universal testing device.Results: Compared with manual treatment, ultrasonic agitation demonstrated a statistically significantly greater SBS values for the tested adhesives.There were no significant differences between the 2 types of adhesive systems and storage times.However, the light-cure adhesive showed an insignificantly higher SBS value compared with self-cure adhesive, and all adhesives' SBSs decreased insignificantly with aging.Conclusions: Ultrasonic agitation can be considered as an efficient method for enhancing the enamel SBS of both light-cure and self-cure universal adhesive systems.