Single bond 2

All cemented posts were cut by diamond disk 927 104 (Diaswiss, Geneva, Switzerland), 3 mm above the flattened root surfaces. Each flattened surfaces was etched for 15 s, rinsed for 10 s and dried with tissue papers (wet bonding). Subsequently, they were covered with two consecutive coats of adhesive resin (SingleBond 2, 3M ESPE, St. Paul, MN, USA). Adhesive resin was gently air dried for 5 s then light cured for 10 s. Cores were built in three increments with the particulate filler composite resin (Z250, 3M ESPE, St. Paul, MN, USA) using 5 mm height and 4 mm width cylindrical polyethylene molds. Each layer was light cured for 20 s. The molds were removed and the occlusobuccal third of the cores were beveled at 45° angle to the root long axis, providing a bevel with 2 mm height and width. Subsequently, the specimens were stored in distilled water at 37°C for 1 week.

Ninety single-root bovine teeth were cleansed with periodontal curettes and stored in
distilled water. Coronal portions were sectioned under water cooling to obtain a
standardized 16 mm root length. The most coronal diameter of the root canal was
measured with a digital caliper (Starrett 727, Starret, Itu, SP, Brazil), and any
tooth with a canal diameter larger than the fiber post diameter (Φ=1.8 mm, White Post
#3, FGM, Joinville, SC, Brazil) was discarded and replaced with a different
specimen.
The apical foramens were sealed using a photo activated adhesive (Single Bond 2, 3M
ESPE, Saint Paul, MN, USA) associated with a composite resin (Oppalis, FGM). The
canals were prepared with the same drill used in the posts system (White Post DC #3,
FGM) to a 12 mm length.

The occlusal faces of five human third molars were wet-ground to create a flat
surface in medium dentin. The surfaces were wet-polished with 600-grit SiC papers to
standardize the smear layer. The teeth were then restored using 35% phosphoric acid
(15 s), and the two-step, etch-and-rinse adhesive system Single Bond 2 (3M ESPE, St.
Paul, MN, USA) was applied to dentin according to the manufacturer's instructions and
then light cured for 20 s. A composite restoration was built-up on each dental
surface using 2 mm increments of a resin composite (Filtek Z250; 3M ESPE); each
increment was photoactivated for 20 s using a LED unit (Radii, SDI, Bayswater,
Victoria, Australia) with 800 mW/cm² irradiance. After storage in
distilled water at 37ºC, for 24 h, the specimens were sectioned perpendicular to the
bonded interfaces into resin-dentin beam-shaped specimens with a cross-sectional area
of approximately 0.5 mm². For each tooth, 24 beams were obtained. The
beams were separated according to tooth origin, protected with nail varnish (except
the adhesive interface region) and randomly assigned into six groups
(n=20) according to the aging conditions. Each group had beams
from every tooth proportionally distributed according to the randomization
procedure.

Immediately following the antioxidant application treatments, the dentin facets of all specimens and controls received two resin pillars to be shear tested. An adhesive tape with two holes of 1.1 mm was used to delimit the area where the bonding was completed.[24 (link)] The adhesive procedure followed the manufacturers' recommendations. The conditioning of the dentin was performed with 37% phosphoric acid (Condac, Joinville, Brazil) for 15 s, followed by rinsing with water for 15 s. Moisture was maintained with cotton balls. Two consecutive layers of adhesive (Single Bond 2, 3M™ ESPE™, St. Paul, MN, USA) were actively applied to the substrate for 15 s. The adhesives were gently air-dried for 5 s. Prior to adhesive polymerization, cylindrical matrices made of perforated noodles each with a diameter of 1.1 mm and a height of 1 mm (Furadinho 6, Pastifício Santa Amalia, SP, Brazil) were positioned onto the bounding tape's adhesive holes.[25 ] The adhesive was light cured for 10 s at 618 mW/cm² (FLASH lite 1401, Discus Dental, Culver City, CA, USA). The matrices were then filled with flowable resin composite (Filtek Z-350, 3M™ ESPE™, St. Paul, MN, USA), which was then light-cured for 40 s. Following 2-h storage in distilled water, the matrices were removed along with the adhesive tape.

In accordance with the instructions of single bond-2 (3M, ESPE, USA) company, the dentin surface of each specimen was acid-etched by 37% phosphoric acid gel for 15 s and then they were rinsed for 10 s by distilled water. The etched dentin was blot-dried according to wet bonding technique. Then single bond-2 was applied with micro brushes on the prepared dentin surface. Two layers of adhesive was applied and light cured by using light curing unit (Bluephase 20i, Vivadent, Lichtenestein, Germany) with a light intensity of 600 mw/cm² for 10 s. 3 mm Z250 resin composite (3M, ESPE, USA) in two layers were used to restore the bonded areas. The light curing distance was at a minimum distance for all of the samples, and each layer were light-cured for 40 s. All of the samples were mounted in self-curing acrylic resin with the level of 1 mm below the CEJ.

One hundred freshly extracted non-carious human
third molars were used for in vitro research based on a protocol approved
by the Ethics Committee of Nanjing Medical University, China [file
number (2019)277]. The dentin specimens were prepared using a low-speed
diamond saw (Isomet 1000, Buehler Ltd., Lake Bluff, IL, USA) and stored
in Hank’s balanced salt solution before analysis.
The
surface was ground with a 600 grit SiC abrasive paper for 60 s and
then etched using 35% phosphoric acid (Gluma Etch 35 Gel) for 15 s.
After rinsing, excess moisture was removed using an absorbent paper.
After treatment with the experimental primer solution, the surface
was coated with a commercial adhesive (Single Bond 2, 3M ESPE, St.
Paul, MN, USA). The composition and application procedures are listed
in Table 2.
The other dentin slabs
used for contact angle measurement were
demineralized with 10% phosphoric acid (695017, Sigma Chemical Co.,
St. Louis, MO, USA) for 5 h and then irrigated with deionized water.
After checking the demineralized dentine surface by digital radiography,
the dentin surfaces were treated with the MPS5, MPS10, or MPS15 primer
and air-dried for 20 s.