The effects of filling techniques and a low-viscosity composite liner on bond strength to class II cavities.
OBJECTIVE
The aim of this study was to test the hypothesis that the effects of filling technique, cavity configuration and use of a low-viscosity composite liner influence resin bond strength to the dentin of class II cavities gingival floor; and analyze the failure modes of fractured specimens.


METHODS
Standardized class II cavities were prepared in the proximal surfaces of freshly extracted third molars, which were randomly assigned to 10 experimental groups. All prepared surfaces were acid-etched, bonded with Single Bond adhesive system and restored with TPH composite, according to each technique: G1 and G2-horizontal layering, G3 and G4-faciolingual layering, G5 and G6-oblique layering, G7 and G8-bulk filling, G9 and G10-control (flat dentin surfaces). Groups were tested, with or without a low-viscosity composite liner (Tetric Flow Chroma). After storage in water for 24h, teeth were vertically serially sectioned to yield a series of 0.8mm thick slabs. Each slab was trimmed into an hourglass shape of approximately 0.8mm(2) area at the gingival resin-dentin interface. Specimens were tested in tension at 0.5mm/min until failure. Fractured specimens were analyzed in an SEM to determine the failure modes.


RESULTS
No significant difference was found between groups restored with and without a low-viscosity composite liner (p>0.05). Among filling techniques, the bulk filling groups presented the lowest bond strength values (p<0.05), while incremental filling groups did not differ from control (flat dentin surfaces). Failure modes varied significantly among groups restored with and without the low-viscosity composite liner.


CONCLUSIONS
Bond strengths were not improved when a low-viscosity composite liner was applied, but it remarkably influenced the failure modes. Incremental techniques improved bond strength.
Figueiredo Reis
André
A
Department of Restorative Dentistry/Operative Dentistry, Piracicaba School of Dentistry, UNICAMP. 901, 13414-900, Piracicaba, SP, Brazil.
Giannini
Marcelo
M
Ambrosano
Gláucia Maria Bovi
GM
Chan
Daniel C N
DC
D000134:Acid Etching, Dental; D000268:Adhesiveness; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003736:Dental Cavity Lining; D003737:Dental Cavity Preparation / Q000145:classification*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods*; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry
D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C420128:Spectrum composite resin; C113300:TPH hybrid; C115612:single bond; C452226:tetric flow composite resin; D014867:Water; D017438:Bisphenol A-Glycidyl Methacrylate