Biomedical Engineering Reference
In-Depth Information
depends on the hybridization of the resin within the exposed collagen mesh as well as to the
dentin tubules (Abdalla & Davidson, 1998), creating a micromechanical interlocking of the
resin within the exposed collagen fibril scaffold. The second is the “self-etch” adhesives
(SEA) which employs acidic monomers that simultaneously condition and prime dentin.
The smear layer remains partially but is used to hybridize with the underlying dentin
(Perdigao et al., 2000). The last is an all-in-one system, but the stability of the bond strength
decreases with time by because it contains many hydrophilic monomers.
According to previous reports, a tiny flake surface formed by the laser irradiation of dentin
can be removed with 30-40 % acid etching, but the primer of SEA cannot. This study
hypothesized that the primer of SEA cannot improve the free surface energy of irradiated
dentin. Therefore, it is unable to make a proper environment for sufficient bond strength.
The null hypothesis was that the shear bond strength with “self-etch” adhesives (SEA) did
not show a difference from that with the etch-and-rinse (ER) technique after a pretreatment
with a laser in dentin.
This study examined the shear bond strength of a hybrid composite resin bonded with two
different adhesive systems to the dentin surfaces prepared with Er,Cr:YSGG laser etching,
and evaluated the morphologic structure of de-bonded dentin surface after Shear Bond
Strength (SBS) Test by scanning electron microscopy.
2. Materials and methods
2.1 Tooth preparation
Tables 1 and 2 list the materials used in this study and the study design, respectively.
Twenty four freshly extracted caries and restoration-free permanent human molars stored in
distilled water were used. The teeth were embedded in improved stone with the occlusal
surface of the crown exposed and parallel to the base of the stone, and the embedded teeth
were sectioned at one third of the occlusal surfaces to expose the dentin surface. Each tooth
was wet-ground with 320-grit silicon carbide paper and polished with 1200-grit to obtain a
flat dentin surface. The specimens were stored in distilled water at 37 °C. The teeth were
divided randomly into two groups, control and laser irradiated groups. The control groups
without laser irradiation were divided randomly into two subgroups (SE bond and Single
bond), and the laser irradiated groups were divided into four subgroups (SE bond with 1.4
W, 2.25 W and Single bond with 1.4W, 2.25W).
2.2 Laser irradiation
The Er,Cr:YSGG laser (Waterlase, BioLase Technology, Inc., San Clemente, CA) with a 2780
nm wavelength and 20 Hz of power with a sapphire tip was used. Laser irradiation was
performed on the dentin surface with either 1.4 W or 2.25 W. The flattened dentin surfaces
of the teeth were irradiated at 90° in non-contact mode with a fixed distance of 6 mm away
from the laser tip in a sweeping motion to achieve an even surface coverage by overlapping
the laser impact. The laser handpiece was attached to a modified surveyor to ensure a
consistent energy density, spot size, distance and handpiece angle.
2.3 Bonding procedures
In all groups, including laser irradiated groups and control groups, the bonding procedures
recommended by the manufacturer' instruction were followed strictly. In the single bond
