**2.4 Shear Bond Strength (SBS) test**

Before loading, the tube mold was removed carefully with a sharp blade and the specimens were then placed in a custom-made fixture mounted on a Universal Testing Machine (INSTRON Model 5562, Norwood, MA). The specimens were loaded to failure under

Effect of the Er, Cr: YSGG Laser Parameters on

Fig. 1. Shear bond strength between the experimental groups.

**3.2 SEM (Scanning Electronic Microscopy)** 

the shear bond test (Figure 2-A, C, E).

after the failure test (D).

surface (F).

Shear Bond Strength and Microstructure on Human Dentin Surface 351

SEM revealed the fractured surface between the composite resin and dentin side, as shown in Figure 2. The representative SEM evaluation showed that thick layers of the adhesives were found on the fractured de-bonded surface of the composite resin (Figure 2-B, D, F). On the other hand, the fractured bonded surface of the dentin by the Clearfil SE bond adhesive treatment, as a result of the shear bond strength test followed by 37% phosphoric acid etching of some of the residues of the adhesives remaining on the surface of dentin side after

Regarding the failure mode of the control group in the types of adhesive system, some residual chips were found (A) on the surface of dentin side fractured after 37% phosphoric acid etching and single bond adhesion but the fractured bonded surface of dentin by the Clearfil SE bond adhesive treatment as a result of the shear bond strength test followed by 37% phosphoric acid etching showed thick layers of composite resin attached to the dentin

In the irradiation groups, 1.4 W of irradiation followed by the Single bond procedure left the fractured dentin surface with small particles after the failure test (B). On the other hand, the fractured dentin surface irradiated with a power intensity of 2.25 W had exposed dentinal tubules after the test (C). On the other hand, 1.4 W of power intensity irradiation followed by the SE bond procedure revealed exposed dentinal tubules after the failure test (E), whereas 2.25 W of power intensity irradiation followed by the SE bond procedure resulted in a thick layer of composite resin fractured cohesively on the dentin side of the fractured

compression using a knife-edge loading head at a cross-head speed of 1 mm/min. The investigator, who was blinded to the group treatment, performed the load testing procedure. The maximum load to failure was recorded for each sample and the Shear bond strength (SBS) was expressed in megapascals (MPa), which was derived by dividing the imposed force (Newtons) by the bonded area (mm2).
