Effect of Water Storage on Properties of Self-Adhesive Resin Cements

Objective: This study was conducted to evaluate the effect of water storage on strength and dimensions of self-adhesive resin cements.  Methods: Five self-adhesive resin cements were selected: experimental automixed paste/paste self-adhesive cement, EXP-SAC (Dentsply/Caulk), Unicem (3M ESPE), Maxcem (Kerr), Monocem (SHOFU) and BisCEM (Bisco). For compressive specimens, cements were mixed, transferred to glass molds and allowed to self-cure.  Cylindrical specimens (4mm×6mm) were stored in 37⁰C deionized water for 24-hr, 1-month, 3-month and 6-month. Compressive strength (CS) was obtained with Instron 4400 at crosshead speed of 5-mm/min. To evaluate dimensional change of cements due to water sorption, cured discs (1mm×20mm) were stored in 0.9% sodium chloride aqueous solution at 37⁰C. Dimensions were measured with a micrometer. The data was analyzed with ANOVA (n=10, a=0.05, Tukey HSD test).  Results: Mean values with standard deviations for CS in MPa and maximum linear expansion (LE, %) after 6-month water storage are listed below:

		EXP-SAC	Unicem	Maxcem	Monocem	BisCEM
CS in Mpa (mean ± s.d.)	24 hr	281±20B	199±19C	345±8A	213±29C	229±6C
	1 Month	261±14A	195±16B	208±28B	204±28B	136±30C
	3 Month	253±18A	187±31B	221±11B	190±36B	140±26C
	6 Month	255±15A	189±36B	206±18B	190±23B	148±23C
LE (%,mean±s.d.)	6 Month	0.35±0.11D	0.59±0.03CD	0.75±0.12C	1.42±0.29B	1.82±0.27A

 *Within the same row, groups connected by the same letter are not significantly different.

Conclusion: The effect of water storage on mechanical strength and dimensions depends on specific cements. The experimental self-adhesive cement displayed insignificant change in compressive strength and exhibited highest compressive strength and lowest water-induced expansion after storage in water for 6 months.