4. Berrong JM, Weed RM, Young JM. Fracture resistance of Kevlar-reinforced poly (methyl methacrylate) resin: a preliminary study. Int J Prosthodont 1990;3:391-5. 5. Braden M, Davy KWM, Parker S, Ladizesky NH, Ward IM. Denture base poly (methyl methacrylate) reinforced with ultra-high modulus polyethylene fibres. Br Dent J 1988,164:109-13. 6. Gutteridge DL. The effect of including ultra-high modulus polyethylene fibre on the impact strength of acrylic resin. Br Dent J 1988;164:17780. 7. Dixon DL, Ekstrand KG, Breeding LC. The transverse strengths of three denture base resins. J PROSTHET DENT 1991;66:510-3. 8. DeBoer J, Vermilyea SG, Brady RE. The effect of carbon fiber orientation on the fatigue resistance and bending properties of two denture resins. J PROSTHET DENT 1984;51:119-21.
cessed resin may not always be smoothly finished, which may result in intraoral irritations.*
CONCLUSION The incorporation of polyethylene fibers does not significantly increase the mean transverse strengths of either Lucitone 199 or Accelar 20 denture base resins. The mean transverse strength of Triad denture base resin, however, is significantly increased by fiber incorporation. REFERENCES
1. Manley TR, Bowman AJ, Cook M. Denture bases reinforced with carbon fibres. Br Dent J 1979;146:25. 2. Schreiber CK. Polymethylmethacrylate reinforced with carbon fibres. Br Dent J 1971;130:29-30. 3. Yazdanie N, Mahood M. Carbon fiber acrylic resin composite: an investigation of transverse strength. J PROSTHET DENT 1985;54:543-7.
DR. DONNA L. DIXON COLLEGE OF DENTISTRY UNIVEFSITY OF IOWA IOWA CITY, IA 52242
Shear strength of laboratory-processed composite bonded to a silane-coated nickel-chromium-beryllium Harold
Schoolof Dentistry, Jackson,Miss.
The shear bond strengths of three commercial laboratory curing composite resin veneers bonded to a nickel-chromium-beryllium alloy treated with the Silicoater system were evaluated. Two light-cured resins and one heat- and pressure-cured resin were evaluated. No statistically significant difference in bond strengths among the three resins was found. Microscopic analysis of the fracture surfaces indicated that all failures were complex and cohesive in nature within the resin and composite. On the basis of the shear bond strengths measured, any of the composite resin veneers tested appear to be clinically acceptable. (J PROSTHET DENT 1992;67:419-22.)
aboratory-cured resin veneers have been introducedasan alternative veneeringmaterial to porcelain and acrylic resin. They are microfilled compositeresinsbased on the BisGMA and urethane dimethacrylate resin systems. A number of these materials have becomecommercially availab1e.lThesematerialsvary in their composition2 and physical properties.3 Principle variations in chemical composition are monomer composition and concentration of filler particles. Physical properties of a particular resin are generally not superior in all characteristics and may vary according to the specific physical property tested.4 Advantages of resin veneersinclude favorable esthetics,
*Assistant Professor, Department bThird year dental student.
abrasionsimilar to natural tooth substance,and the ability to be repaired. Polymerization is initiated by light curing or heat and pressurepolymerization. Applications of theseprosthetic veneering resinsinclude pontics for resinbonded fixed partial dentures, overlay removable partial dentures, veneered crowns, and fixed partial dentures. Bonding of laboratory polymerized composite resin to metal has traditionally been provided by mechanical retention such as beads, mesh, and loops. The chemicalbonding resin veneerseliminate the need for these bulkier macroretentive features and the pooling of opaquing material around retention beadsis eliminated. Several methods have been introduced to enhancethe bonding of resinveneersto castalloys. One method is based on the Silicoating system (Kulzer Inc., Irvine, Calif.). The Silicoating system provides a pyrolytically applied silica surface (SiO,-C) to which composite resin will bond by 419
I. Resin-to-alloy shear bond strengths (megapascals)
Mean shear bond strength Standard deviation
There was no statistical difference between Newman-Keuls test (N = 15, N