OBJECTIVE The aim study to evaluates the effect of different diamond bur roughness on the shear bond strength of resin-based composite to the enamel superficial microroughness This may affect adhesion by modifying the substrates' characteristics when using an eighth-generation bonding agent adhesive. MATERIALS AND METHODS The 40 premolars were embedded in acrylic resin blocks, Samples were distributed 10 Samples into 4 groups according to burs: black, white, yellow burs, and polishing (control) prepared buccally with in the enamel flat surface, followed applied by eighth-generation bonding agent and A heavy-body silicone mold was used to form an accurate template for composite application, applied with composite resin restoration and polymerization. Shear bond strength (SBS) was tested using a Zwick Roell universal testing machine, and failure modes were analyzed. RESULTS showed white bur group exhibited the highest shear bond strength (SBS), with a mean value of 0.80 ± 0.118 MPa followed by yellow bur group 0.54 ± 0.119 MPa, followed by black bur group showed of 0.40 ± 0.071 MPa, followed by pumice polishing group had the lowest bond strength, at 0.34 ± 0.053 MPa, significant differences between the 4 uses groups (P value < 0.001). CONCLUSION. enamel surface roughness created by white diamond burs considerably influences the shear bond strength of resin bonded restorations.

Enamel, veneer, Bonding, Shear strength, Dental instruments

Group W demonstrated the highest bond strength, indicating that this bur type creates the most favorable dentin surface for bonding.

Groups P and Y exhibited significantly lower bond strength values, emphasizing that these preparation methods are not ideal for achieving durable adhesion.

Failure modes correlated with bond strength, with higher bond strength associated with more cohesive and mixed failures.

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