The use of flowable composites as filled adhesives.
OBJECTIVE
The effect of filled adhesives on bonding resin composites to dentin has not been fully understood. Due to their filler content, filled adhesives may act as stress breakers. The aim of this in vitro study was to evaluate the use of flowable composites of different viscosities on bonding to enamel and dentin without the use of an intermediate bonding resin.


METHODS
Enamel and dentin bond strengths of OptiBond FL, Syntac Classic, and EBS Multi combined either with their proprietary bonding agent or a flowable resin composite (Ultraseal XT Plus or Revolution) were measured. The tests were carried out with a microtensile device at a crosshead speed of 1mm/min after 24h of storage at 37 degrees C in water. Mean bond strengths were analyzed using the Wilcoxon test and multiple comparisons according to the Mann-Whitney U-test. The micro-morphology of corresponding resin-dentin interfaces of the same teeth were analyzed using SEM and TEM.


RESULTS
The control groups with adhesive systems used as per manufacturers' protocol showed bond strengths of 38.9-41.1 MPa to enamel and 28.8-33.4 MPa to dentin. With respect to bond strength to etched enamel, only Ultraseal XT Plus as bonding resin reached the level of the control groups. When used as bonding agents on dentin, both flowable composites produced lower microtensile bond strengths to etched and primed dentin than did the control groups. Micro-morphological analysis using SEM and TEM resulted in hybrid layer formation for both control and experimental groups. However, many areas of the resin-dentin interface showed insufficient penetration of the flowable composites at the top of the hybrid layer as well as numerous tubules obstructed by filler particles.


CONCLUSIONS
The flowable composites tested in this study should not be used to replace bonding agents. Flowable composites of thinner viscosity, such as Ultraseal XT Plus, may bond to enamel adequately without the requirement of an intermediate bonding resin.
Frankenberger
Roland
R
Policlinic for Operative Dentistry and Periodontology, University of Erlangen-Nuremberg, Glueckstrasse 11, D-91054 Erlangen, Germany. frankbg@dent.uni-erlangen.de
Lopes
Manuela
M
Perdigão
Jorge
J
Ambrose
Wallace W
WW
Rosa
Bruno T
BT
D000134:Acid Etching, Dental; D000269:Adhesives / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003743:Dental Enamel / Q000648:ultrastructure; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D016555:Matched-Pair Analysis; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids / Q000737:chemistry; D010895:Pit and Fissure Sealants / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013223:Statistics as Topic; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry
D000269:Adhesives; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C113072:EBS adhesive system; D008689:Methacrylates; C092987:Optibond; D010756:Phosphoric Acids; D010895:Pit and Fissure Sealants; D019279:Resin Cements; C102735:Revolution (composite resin); C078484:Syntac dentine adhesive; C106663:Ultra Seal XT; C111840:flowable hybrid composite; D014867:Water