| Summary: | OBJECTIVES: To determine the effects of sintering cycle and curing technique on the translucency, refractive index and flexural strength of novel polymer-infiltrated ceramics.
MATERIALS AND METHODS: Alumina and spinel matrix specimens were fabricated by slip casting (15mm diameter × 2mm thickness). Alumina and spinel specimens were divided into 7 and 6 groups respectively (n=10/group). Alumina groups AHP1, AH1and AM1 were sintered at 1150°C, groups AHP2, AH2 and AM2 at 1200°C and group AFD was fully sintered at 1550°C. Spinel groups SHP1, SH1 and SM1 were sintered at 1500°C and groups SHP2, SH2, SM2 at 1600°C. Density was calculated for each specimen. Groups AM1, AM2, AFD, SM1 and SM2 were the control groups and received no further treatment. Other groups were silanated and dried overnight at 90°C. Then, UDMA-TEGDMA (50-50 mole) resin was prepared and infiltrated into the ceramic specimens under vacuum. Groups AHP1, AHP2, SHP1 and SHP2 were cured by heat at 90°C under pressure of 138 MPa. Groups AH1, AH2, SH1 and SH2 were cured by heat at 90°C. Specimens were polished (1.5mm thickness) and density measured. The total transmission was evaluated with a spectrophotometer (X-rite Ci7600). Refractive index was measured (Presidium Refractive Index Meter II). Biaxial flexural strength was obtained (Instron 5566A) with a crosshead speed of 0.5mm/min. The microstructure was examined using a field emission scanning electron microscope (FESEM-VP, Hitachi SU6600). Statistical analyses were performed using Excel 2016 (Microsoft Office) and JMP 13 (SAS).
RESULTS: Polymer-infiltrated alumina and spinel showed significantly lower refractive index (p< .0001), higher translucency (p< .0001) and higher flexural strength (p< .0001) than their corresponding ceramic matrix groups. Sintering temperature of the ceramic matrix had a significant influence on the flexural strength of polymer-infiltrated ceramics. The application of pressure during polymerization significantly improved the translucency but did not influence significantly the flexural strength of polymer-infiltrated ceramics. Groups AHP2 and AH2 showed high strength (comparable to fully sintered alumina). Polymer-infiltrated spinel showed better translucency but lower strength than alumina groups.
CONCLUSION: Sintering temperature and curing technique had a significant influence on optical and mechanical properties of polymer-infiltrated ceramics. === 2020-10-24
|
|---|
