Flexural properties of acrylic resin polymers reinforced with unidirectional and woven glass fibers.
BACKGROUND
Fiber-reinforced plastics for dental applications have been under development for some time. A major difficulty in using reinforcing fibers with multiphase acrylic resins, such as powderliquid resins, has been improper impregnation of fibers with the resin.


OBJECTIVE
The aim of this study was to describe and test a novel system to use polymer-preimpregnated reinforcing fibers with commonly used multiphase acrylic resins.


METHODS
Continuous unidirectional and woven preimpregnated glass fiber reinforcements (Stick and Stick Net) were used to reinforce heat-curing denture base and autopolymerizing denture base polymers. A temporary fixed partial denture polymer was also reinforced with Stick reinforcement material. Five test specimens were fabricated for unreinforced control groups and for Stick- and Stick Net-reinforced groups. A 3-point loading test was used to measure transverse strength and flexural modulus of the materials and ultimate strain at fracture was calculated. Cross-sections of test specimens were examined with a SEM to evaluate degree of impregnation of fibers with polymer matrix. Quantity of fibers in test specimens was determined by combustion analysis.


RESULTS
Transverse strength of heat-curing denture base polymer was 76 MPa, Stick reinforcement increased it to 341 MPa, and flexural modulus increased from 2550 to 19086 MPa. Stick Net reinforcement increased transverse strength of heat-curing denture base polymer to 99 MPa and flexural modulus to 3530 MPa. Transverse strength of autopolymerizing denture base polymer was 71 MPa; Stick increased it to 466 MPa; and flexural modulus increased from 2418 to 16749 MPa. Stick Net increased the transverse strength of autopolymerizing denture base polymer to 96 MPa and flexural modulus to 3573 MPa. Transverse strength of temporary fixed partial denture polymer increased from 58 to 241 MPa and flexural modulus from 1711 to 7227 MPa. ANOVA showed that reinforcement type and polymer brand affected transverse strength and modulus (P <.001). Stick Net reinforcement increased the strain at fracture, whereas Stick reinforcement decreased the strain values. SEM examination revealed well-impregnated glass fibers with polymer matrix. Quantity of glass fibers varied from 6 to 28 vol-%, the lowest being with Stick Net reinforcement and the highest with Stick reinforcement.


CONCLUSIONS
Novel glass fiber reinforcements may considerably enhance flexural properties of multiphase dental polymers, which is due to proper impregnation of fibers with polymer matrix. By using Stick or Stick Net reinforcement, the strain at fracture of the material can be modified.
Vallittu
P K
PK
University of Turku, Turku, Finland.
D000180:Acrylic Resins / Q000737:chemistry*; D000704:Analysis of Variance; D003764:Dental Materials / Q000737:chemistry*; D019232:Dental Restoration Failure; D003819:Denture Bases; D003830:Denture, Partial, Fixed; D003833:Denture, Partial, Temporary; D005898:Glass / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011095:Polyethylenes / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011208:Powders; D012996:Solutions; D013314:Stress, Mechanical; D013499:Surface Properties
D000180:Acrylic Resins; D003764:Dental Materials; D008768:Methylmethacrylates; D011095:Polyethylenes; D011108:Polymers; D011208:Powders; D012996:Solutions; C009753:fiberglass; C111601:ultra-high molecular weight polyethylene; D019904:Polymethyl Methacrylate