ABSTRACT
Aim: This study evaluated the effect of varying the powder/liquid (P/L) ratio on the shear bond to dentin (SBS) and flexural strength (FS) of glass ionomer cements (GIC)s. Methods: Three types of GICs (Fuji II, Fuji II LCi and Fuji IX GP) were mixed using the following P/L ratios: 20% lower than the manufacturer's ratio, manufacturer's ratio, 20% higher than the manufacturer's ratio (9 groups). SBS (MPa) was evaluated and the mode of failure checked under stereomicroscope. FS (MPa), of the specimens (25×2×2mm) assessed using a universal testing machine at a crosshead speed of 1 mm/min. The data were subjected to two-way ANOVA and Tukey's test for analysis (p< 0.05). Results: The highest SBS and FS (MPa) obtained for Fuji II, Fuji II LCi and Fuji IX were 6.12±2.11 and 16.96±2.73; 11.60±3.19 and 49.58±8.75; 7.39±2.77 and 20.32±2.09, respectively. The interaction between materials and P/L ratios had no significant effect on the properties tested in this study. Fuji II LCi exhibited significantly higher SBS and FS than the other two GICs in all P/L ratios. Conclusions: No significant differences were observed between Fuji II and Fuji IX. Twenty percent variation in P/L ratio had no significant effect on SBS and FS of GICs.
Subject(s)
Dentin , Flexural Strength , Glass Ionomer CementsABSTRACT
STATEMENT OF PROBLEM: Volume stability, microstructure reproducibility and fluidity along with compatibility with dental stone must be in consideration in order to use tissue conditioner as a material for functional impression. There are few studies concerning the influence of time factor in oral condition on surface roughness of the stone and optimal retention period in the oral cavity considering such changes in surface roughness. PURPOSE: The purpose of this study was to find out the influence of various kinds of tissue conditioner, its powder/liquid ratio and immersion time on surface roughness of the stone. MATERIAL AND METHODS: Materials used in this study were the three kinds of tissue conditioners (Coe-Comfort, Visco-Gel, Soft-Liner) and were grouped into three: group R - mixed with standard powder/liquid ratio that was recommended by the manufacturers, group M - mixed with 20% more powder, group L - mixed with 20% less powder. Specimens were made with the size of 20 mm diameter and 2 mm width. Each tissue conditioner specimens were subdivided into 5 groups according to the immersion time (0 hour, 1 day, 3 days, 5 days, 7 days), completely immersed into artificial saliva and were stored under 37degrees C. Specimens of which the given immersion time elapsed were taken out and were poured with improved stone, making the stone specimens. Surface roughness of the stone specimens was measured by a profilometer. RESULTS: Within the limitation of this study, the following results were drawn. 1. Major influencing factor on surface roughness of the stone model made from tissue conditioner was the retention period (contribution ratio (rho) = 62.86%, P < .05) of the tissue conditioner in oral cavity to make functional impression. 2. In case of Coe-Comfort, higher mean surface roughness value of the stone model with statistical significance was observed compared to that of Soft-Liner and Visco-Gel as immersion time changes (P < .05). 3. In case of group L (less), higher mean surface roughness value of the stone model with statistical significance was observed compared to that of R (recommended) and M (more) group as immersion time changes (P < .05). CONCLUSION: We may conclude that as the retention period of time in oral cavity influences surface roughness of the stone model the most and as the kind of tissue conditioner and its P/L ratio may influence also, clinician should well understand the optimal retention period in oral cavity and choose the right tissue conditioner for the functional impression, thus making the functional impression with tissue conditioner usefully.