Storage influence on castor oil biopolymer compressive strength

Objectives: The aim of this study was to compare the compressive strength of an experimental polyurethane dental luting agent derived from castor oil (PUCO) with the compressive strength of a resin cement (Panavia^TM - control group) after storage in acid and ionic solutions. Methods: Sixty PUCO and 48 Panavia^TM specimens (6mm x 12mm) were prepared and divided in 2 groups according to storage time (G1-24hs or G2-90 days) and also to the storage solution (A-distilled water, B-chloride of sodium or C-lactic acid). The cements were manipulated in accordance with the manufacturers' instructions and poured into a Teflon matrix. The specimens remained under a constant load at 37^oC and 100% relative humidity of the air for 1h. They were polished and stored in their respective solutions for the determined period. Compressive strength was performed in a MTS-810 machine (10kN at 0.5mm/min). The data were analyzed by Kruskal-Wallis or two-way ANOVA tests (a=0.05). Results: The compressive strength means in MPa were: PUCO- G_1A – 16.77±2.47; G_2A – 3.20±0.75; G_1B - 13.10±2.95; G_2B - 2.94±0.29; G_1C - 16.14±5.68; G_2C - 6.66±1.47; Panavia^TM- G_1A – 204.39±28.84; G_2A – 131±23.70; G_1B - 188±19.29; G_2B - 120.53±35.46; G_1C - 192.33±23.77; G_2C - 134.97±20.73. The compressive strength of both cements was negatively influenced by the storage time (p>0.05) independently of the kind of solution (p<0.05). Conclusions: It was concluded that PUCO compared with the resin cement had an inferior compressive strength. The storage time was a negative factor for the evaluated property.