Physical Properties of Temporary Cements

Objective: The purpose of this study was to evaluate the physical properties of resin-based, zinc oxide/eugenol and non-eugenol temporary cements. Method: Two resin based cements: experimental material (EXP, Kerr), Tempbond Clear (TBC, Kerr); one zinc oxide/eugenol cement: Embonte (EMB, Dux); two zinc oxide/non-eugenol cements: Tempbond NE (TBN, Kerr) and TempoCem NE Smartmix (TCN, DMG) were tested.  Shore D hardness (SD, n=3) was measured according to ASTM D2240. Film thickness (FT, n=5) was tested according to ISO 6876 standard. For the bonding strength (BS) to human dentin a pre-cured knob made of a temporary crown and bridge material: Temphase (Kerr) in a cylindrical mold (D=3.1mm, H=4mm) was bonded to the dentin with a temporary cement. The specimens (n=6) were stored at 37°C for 24 hours and then subjected to shear force on an Instron mechanical tester. Results: The mean values of the test data were reported in the following table. ANOVA analysis of the data showed that EXP and EMB had significantly lower hardness and film thickness than TBC, TBN and TCN. EXP had significantly lower bonding strength than TBC, TBN and TCN. TBC had no significant differences in bonding strength among the tested materials due to the large standard deviation.

	EXP	TBC	EMB	TBN	TCN
SD	31±0a	46±1c	36±2b	49±0c	46±2c
FT(µm)	3.4±2a	19.8±5b	3.3±1a	18.9±6b	19.7±6b
BS(MPa)	0.25±0.11a	0.44±0.40 a,b	0.50±0.21b	0.53±0.1b	0.45±0.04b

*Mean with the same letters are not significantly different (p<0.05) within the same row.

Conclusion:  EXP is a softer material and is weaker in bonding to the dentin surface, thus leading to lower retention of the temporaries and allowing for easy removal.