Effect of active bonding application after selective dentin etching on the immediate and long-term bond strength of two universal adhesives to dentin.

Description :

Forty-eight extracted bovine incisors teeth will be collected, cleansed of soft tissue, and stored in 0.5% Chloramine-T solution for seven days. Then, they will be removed from the disinfectant solution, washed abundantly, and stored in distilled water at 4 ◦C until use. Upon the approval of the ethical committee of the faculty of dental medicine at the university of Saint-Joseph, all these teeth will be used for determining micro-tensile bond strength (μTBS) and scanning electron microscopy (SEM). For specimen preparation, the root will be sectioned, and their crowns embedded in acrylic resin, allowing the buccal enamel surface to be exposed. Then, the enamel will be abraded with an orthodontic grinder (Essencedental, Araraquara/SP, Brazil) until exposure of a flat medium dentin surface. The exposed dentin surface will then wet-ground with P320 silicon carbide sandpaper using a speed grinder-polisher (Buehler Ltd., Lake Bluff, IL, USA) at a motor speed 70 rpm for 1 min under a water cooling conditions for 30 s to standardize the smear layer. Then, the teeth will be randomly divided into two groups based on the adhesive system used. Subsequently, the specimens will be divided into subgroups according to the protocol application (n= 5 teeth/group): self-etch (SE), selective dentin etching + active application for 15s (SDE15), selective dentin etching + active application for 20s (SED20), and selective dentin etching + active application for 25s (SED25). For SE group, the adhesive systems were applied according to the manufacturers’ instructions using the self-etch mode. For SDE15, SDE20 and SDE25, selective dentin etching will be performed by applying 32% phosphoric acid gel (Scotchbond Universal Etchant, 3M ESPE) for 3 s on the dentin surface, followed by copious rinsing with water for 15 s. The moisture control will be performed using absorbent paper. Thereafter, the adhesive system will be applied with active application by scrubbing the dentin surface under manual pressure for three different time 15 s, 20 s and 25 s respectively. The applied adhesive will be gently dried for 5 s to remove the excess solvent, followed by light-curing for 20 s using a light-emitting diode light-curing unit (Bluephase N, Ivoclar-Vivadent) at 1200 mW/cm2. After bonding procedures, resin composite build-ups (FiltekTM Z250, 3M ESPE, St. Paul, MN, USA or Ceram X Duo, Dentsply, Konstanz, Germany) will be constructed in 3 increments of 2 mm each and each layer will be polymerized for 30 s. All bonding procedures will be carried out by a single operator.