Digital Light Processing of Zirconia Suspensions Containing Photocurable Monomer/Camphor Vehicle for Dental Applications

초록

This study reports the utility of solid camphor as a novel diluent in photocurable hexanediol diacrylate (HDDA) monomer to manufacture 4 mol% yttria partially stabilized zirconia (4Y-PSZ) components for dental applications by digital light processing (DLP). The use of a 65 wt% HDDA-35 wt% camphor solution allowed 4Y-PSZ suspensions to have reasonably low viscosities (1399 +/- 55.8 mPa center dot s at a shear rate of 75 s(-1)), measured by a cone/plate viscometer, at a high solid loading of 48 vol%, where 4Y-PSZ particles prepared by calcination of as-received 4Y-PSZ granules, followed by a ball-milling process, were used with assistance of a dispersant. These 4Y-PSZ suspensions could be successfully applied to our custom-made DLP machine for manufacturing 4Y-PSZ components. To this end, several processing parameters, including layer thickness of 4Y-PSZ suspension, UV illumination time for layer-by-layer photocuring process, and initial dimensions of 4Y-PSZ objects, were tightly controlled. As sintering temperature increased from 1300 degrees C to 1500 degrees C, relative density and grain size of 4Y-PSZ objects increased, and cubic phase content also increased. Thus, after sintering at the highest temperature of 1500 degrees C for 3 h, high mechanical properties (biaxial flexural strength = 911 +/- 40.7 MPa, hardness = 1371 +/- 14.4 H-v) and reasonably high optical transmittance (translucency parameter = 7.77 +/- 0.32, contrast ratio = 0.809 +/- 0.007), evaluated by a spectrophotometer, were obtained due to a high relative density (97.2 +/- 1.38%), which would be useful for dental applications.

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