[EP-8] Flexural Strength of Polymethyl Methacrylate Provisional Crown and Bridge Materials Fabricated by Mixing and Machining
[Abstract]
[Objective]
To evaluate the flexural strength of polymethyl methacrylate (PMMA) materials utilized for provisional crown and bridge applications, employing various fabrication techniques, and to assess their percentage weight changes followingthermocycling.
[Method]
This study involves CAD/CAM PMMA resin blocks produced through sawing (Telio CAD: TC, Bloomden: BD) and conventional PMMA resins (self-cured and heat-cured acrylic resins) fabricated via flasking (Ivocron Cold flasking technique: CF, Ivocron Press: PF) and pouring techniques (Ivocron Cold pouring technique: CP). Specimens (sized2x2x25 mm3) from each group were divided into 2 subsets (n=10) for non-thermocycling and thermocycling (5-55 ºC, 5,000 cycles). Flexural strength was determined using a universal testing machine, while the percentage weight change following thermocycling was computed. Data were analyzed using two-way ANOVA for the flexural strength test andone-way ANOVA for percentage weight change (α=.05). The fractured surface were examined using a scanning electron microscope.
[Results and Discussion]
Under non-thermocycling conditions, BD (138.35±3.86 MPa) and TC (133.30±7.01 MPa) exhibited significantly higher flexural strength than PF (95.70±13.10 MPa), CF (87.94±8.20 MPa), and CP (82.80±8.92 MPa) (p<.001). Flexural strength decreased significantly across all groups after thermocycling (p<.018) due to water-induce degradation.1) Under thermocycling conditions, BD (97.64±3.36 MPa) and TC (92.26±2.29 MPa) also displayed significantly higher flexural strength than CP (74.32±7.38 MPa), PF (69.79±9.32 MPa), and, CF (67.89±7.98 MPa) (p<.001). All specimens increased in weight after thermocycling due to water absorption.2) BD (1.47%) and TC (1.58%) demonstrated significantly lower weight change, while CF (2.44%) exhibited the highest weight change. Pores ranging from 2 to10 µm in diameter were widely distributed throughout all conventional PMMA resins, whereas the PMMA blocks exhibited a more homogenous structure. All PMMA resin blocks demonstrated better flexural strength and lower water absorption than all conventional PMMA resins.
[References]
1) Takahashi Y, Chai J, Kawaguchi M. Equilibrium strengths of denture polymers subjected to long-term water immersion. Int J Prosthodont 1999;12(4):348-52.
2) Yao J, Li J, Wang Y, Huang H. Comparison of the flexural strength and marginal accuracy of traditional and CAD/CAM interim materials before and after thermal cycling. J Prosthet Dent 2014;112(3):649-57.
[Objective]
To evaluate the flexural strength of polymethyl methacrylate (PMMA) materials utilized for provisional crown and bridge applications, employing various fabrication techniques, and to assess their percentage weight changes followingthermocycling.
[Method]
This study involves CAD/CAM PMMA resin blocks produced through sawing (Telio CAD: TC, Bloomden: BD) and conventional PMMA resins (self-cured and heat-cured acrylic resins) fabricated via flasking (Ivocron Cold flasking technique: CF, Ivocron Press: PF) and pouring techniques (Ivocron Cold pouring technique: CP). Specimens (sized2x2x25 mm3) from each group were divided into 2 subsets (n=10) for non-thermocycling and thermocycling (5-55 ºC, 5,000 cycles). Flexural strength was determined using a universal testing machine, while the percentage weight change following thermocycling was computed. Data were analyzed using two-way ANOVA for the flexural strength test andone-way ANOVA for percentage weight change (α=.05). The fractured surface were examined using a scanning electron microscope.
[Results and Discussion]
Under non-thermocycling conditions, BD (138.35±3.86 MPa) and TC (133.30±7.01 MPa) exhibited significantly higher flexural strength than PF (95.70±13.10 MPa), CF (87.94±8.20 MPa), and CP (82.80±8.92 MPa) (p<.001). Flexural strength decreased significantly across all groups after thermocycling (p<.018) due to water-induce degradation.1) Under thermocycling conditions, BD (97.64±3.36 MPa) and TC (92.26±2.29 MPa) also displayed significantly higher flexural strength than CP (74.32±7.38 MPa), PF (69.79±9.32 MPa), and, CF (67.89±7.98 MPa) (p<.001). All specimens increased in weight after thermocycling due to water absorption.2) BD (1.47%) and TC (1.58%) demonstrated significantly lower weight change, while CF (2.44%) exhibited the highest weight change. Pores ranging from 2 to10 µm in diameter were widely distributed throughout all conventional PMMA resins, whereas the PMMA blocks exhibited a more homogenous structure. All PMMA resin blocks demonstrated better flexural strength and lower water absorption than all conventional PMMA resins.
[References]
1) Takahashi Y, Chai J, Kawaguchi M. Equilibrium strengths of denture polymers subjected to long-term water immersion. Int J Prosthodont 1999;12(4):348-52.
2) Yao J, Li J, Wang Y, Huang H. Comparison of the flexural strength and marginal accuracy of traditional and CAD/CAM interim materials before and after thermal cycling. J Prosthet Dent 2014;112(3):649-57.