Effect of a retention groove on the shear bond strength of dentin-bonded restorations.
BACKGROUND
With the increasing use of minimally invasive restorations, effective adhesion becomes more important. Applying mechanical retention to a flat dentin surface might improve the adhesion of ceramic and composite resin restorations.


OBJECTIVE
The purpose of this in vitro study was to evaluate the effect of a groove in a flat dentin surface on the bond strength of various restorative materials.


METHODS
Dentin specimens of bovine teeth were prepared with or without a groove. Identical disks were fabricated from direct composite resins (Filtek Supreme XTE [FS] and Clearfil AP-X [AP]) and indirect ceramics (Vita Mark II [VM] and IPS E.max CAD [EM]). These materials were bonded directly or cemented adhesively to the dentin specimens. Shear bond strength was tested with a universal testing machine. Finite element analysis (FEA) models of the test arrangement were made to further analyze the stress distribution.


RESULTS
VM (no groove, 5.1 ±3.0 MPa; groove, 8.7 ±1.5 MPa) and EM (no groove, 11.4 ±3.7 MPa; groove, 17.7 ±5.2 MPa) showed significant effect of a groove on the shear bond strength. FS (no groove, 18.6 ±4.9 MPa; groove, 16.3 ±4.3 MPa) and AP (no groove, 25.8 ±3.8 MPa; groove, 24.2 ±7.2 MPa) showed no significant effect of a groove. For the composite resins, the retention groove increased the shear stress along the dentin-restoration interface, and debonding at the contact surface started at lower load values than for the specimens without a groove.


CONCLUSIONS
Application of a groove to a flat dentin surface improved the shear bond strength for ceramic restorations. For direct composite resin restorations, exhibiting a lower elastic modulus, a groove had no significant effect on the shear bond strength, while it increased the shear stress along the dentin-restoration interface for composite resin.
Doctoral student and Clinical Instructor, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands. Electronic address: p.d.kok@acta.nl.
Paul
P
de Kok
Assistant Professor, Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
Niek
N
de Jager
Private practice, Amsterdam, The Netherlands.
Isabelle A M
IA
Veerman
Private practice, Amsterdam, The Netherlands.
Naila
N
Hafeez
Professor, Department of Biomaterials, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
Cornelis J
CJ
Kleverlaan
Professor, Department of Comprehensive Dentistry, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
Joost F M
JF
Roeters
D000818:Animals; D002417:Cattle; D002516:Ceramics / Q000627:therapeutic use; D003188:Composite Resins / Q000627:therapeutic use; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods / Q000592:standards; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents / Q000627:therapeutic use*; D066298:In Vitro Techniques; D033081:Shear Strength
D003188:Composite Resins; D017220:Dentin-Bonding Agents