engleski

Influence of fiber reinforcements depth alignment on polymer flexural strength.

Objectives: Fractures of denture base polymer material (DBPM) are one of the most frequent reasons for repair of removable dental prosthesis (RDP). Bending load applied on maxillary RDP (associated with material fatigue) is the reason for medial line fracture. There is a continuous strive to strengthen DBPM, and mechanical properties of acrylic RDPs could be enhanced by integration of reinforcement fibers into DBPM. According to the mechanical rules of bending test it is very important that reinforcements are placed as far as possible from the neutral axis (into tensile load area of the specimen) thus giving higher flexural strength. Methods: Quadratic specimens (n=300) made of DBPMs and E- glass fibers (dimensions 18 x 10 x 3 mm) were produced to determine the influence of different depth alignment of glass fiber reinforcements (unidirectional and net) onto specimens' flexural strength. Specimens were tested after (I) polymerization, (II) storage at 37şC temperature during 28 days, and (III) thermocycling using the “short beam” method. Microscopic examination was performed to determine the quality of bonding between glass fibers and matrix. Results: The study showed statistically significant higher flexural strength when fiber reinforcements were placed in DBPM of specimens 2 mm from the loading blade (130.63-158.55 MPa) compared to the 2.5 mm distance (117.83 – 153.68 MPa). Specimens tested after polymerization had significantly higher flexural strength values than specimens tested after storage in water at 37şC during 28 days, while specimens tested after thermocycling unexpectedly revealed the highest values. Conclusions: Fiber reinforcements should be positioned more than 0.5 mm (up to 1 mm) from the base surface of RDPs since lesser distance would diminish reinforcing effect. Both DBPM revealed higher flexural strength values after thermocycling thus suggesting that the increase of temperature (during thermocycling) had the effect of prolonged polymerization which enhanced polymer mechanical properties.

fiber reinforcements ; polymers ; flexural strength

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