The Thickness Effect of Laminated Alginate Impression on Dental Stone Surface

To fabricate optimum prostheses, the quality of working model, especially the surface is critical. When impression is taken by laminate alginate impression, the surface property of the model is crucial since itʼs amount of water increases than that of standard W/P ratios. This study examined the model surface quantitatively and qualitatively to identify their optimum thickness of the secondary laminated impression. The thickness of the secondary impression was set to 0.4mm (A0.4), 0.6mm (A0.6), and 0.8mm (A0.8). The surface roughness of A0.4, A0.6, and A0.8 andcontrol was quantitatively assessed by scanning laser microscope, measuring Ra, Ry, Rz, analyzed with ANOVA and Dunnettʼs multiple comparison post hoc test. Qualitative observation of the surface was done by scanning electron microscope (SEM), and crystal structure was assessed by X-ray diffraction. A0.4 significantly showed roughness surface compared to control in Ra andRz (p<0.01). Also Ry was significantly high with A0.4 and A0.6 compared to the control (p<0.05). From SEM observation, the size of crystal column was prominent with A0.4 among the samples, which exhibited a different image from the control. TheX-ray diffraction detect dental stone hardened body, gypsum (CaSO4·2H2O), and unhardened, anhydrite (γ-CaSO4). A0.4 detected strong peak of anhydrite that indicate unhardened characteristic of dental stone. From above optimum thickness of the secondary laminated impression was suggested at 0.8mm to keep comparable surface quality and surface texture of the single impression.