Flexural Properties of Injection-Molded Thermoplastic Denture Base Resins

Objectives: To investigate the flexural properties of injection-molded thermoplastic denture base resins for future materials.
Methods: Six injection-molded thermoplastic resins [two polyamides (Valplast, Lucitone FRS), one polyethylene terephthalate (Estheshot Bright), one polycarbonate (Reining N), two acrylic (Acry Tone, Acry Jet)] and auto-polymerized polymethyl methacrylate (Procast DSP, Procast DSP with wire, Ivo Base High Impact) , conventional heat-polymerized polymethyl methacrylate (Pro Impact), and a conventional heat-polymerized polymethyl methacrylate(Acron) as a control were used in this study. Ten specimens were fabricated for each denture base materials according to the manufacturer’s instructions in 65mm long × 10mm width × 3.3mm thickness. The flexural strength at the maximum load and the elastic modulus of the denture base resins were measured using universal testing machine (TG-5kN；Minebea, Nagano, Japan) with a distance of 50mm between the two supporting points and a crosshead speed of 5mm/min according to International Organization for Standardization (ISO) 20795-1.
Results: Descending order of flexural strength were Procast DSP wire > Reining N > Ivo Base High Impact > Procast DSP > Acron > Pro Impact > Estheshot Bright > Lucitone FRS > Acry Tone > AcryJet > Valplast. Descending order of elastic modulus were Procast DSP wire > Acron > Procast DSP > Ivo Base High Impact > Reining N > Pro Impact > Estheshot Bright > AcryTone > Acry Jet > Lucitone FRS > Valplast.
Conclusions: Type 3 denture base resins were required more than 65 MPa on flexural strength and 2000 MPa on elastic modulus according to the ISO standard. From this study, Procast DSP wire, Reining N, Procast DSP, Acron, Ivo Base High Impact, Pro Impact showed enough flexural strength and elastic modulus in both properties which are required in ISO standard.