Effect of temporary cements on the shear bond strength of luting cements

OBJECTIVE: The purpose of this study was to evaluate, by shear bond strength (SBS) testing, the influence of different types of temporary cements on the final cementation using conventional and self-etching resin-based luting cements. Material and Methods: Forty human teeth divided in two halves were assigned to 8 groups (n=10): I and V (no temporary cementation); II and VI: Ca(OH)2-based cement; III and VII: zinc oxide (ZO)-based cement; IV and VIII: ZO-eugenol (ZOE)-based cement. Final cementation was done with RelyX ARC cement (groups I to IV) and RelyX Unicem cement (groups V to VIII). Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. RESULTS: Means were (MPa): I - 3.80 (&plusmn;1.481); II - 5.24 (&plusmn;2.297); III - 6.98 (&plusmn;1.885); IV - 6.54 (&plusmn;1.459); V - 5.22 (&plusmn;2.465); VI - 4.48 (&plusmn;1.705); VII - 6.29 (&plusmn;2.280); VIII - 2.47 (&plusmn;2.076). Comparison of the groups that had the same temporary cementation (Groups II and VI; III and VII; IV and VIII) showed statistically significant difference (p<0.001) only between Groups IV and VIII, in which ZOE-based cements were used. The use of either Ca(OH)2-based (Groups II and VI) or ZO-based (Groups III and VII) cements showed no statistically significant difference (p>0.05) for the different luting cements (RelyX TM ARC and RelyX TM Unicem). The groups that had no temporary cementation (Groups I and V) did not differ significantly from each other either (p>0.05). CONCLUSION: When temporary cementation was done with ZO- or ZOE-based cements and final cementation was done with RelyX ARC, there was an increase in the SBS compared to the control. In the groups cemented with RelyX Unicem, however, the use of a ZOE-based temporary cement affected negatively the SBS of the luting agent used for final cementation

Activation of the microsomal glutathione-S-transferase and reduction of the glutathione dependent protection against lipid peroxidation by acrolein

Allyl alcohol is hepatotoxic. It is generally believed that acrolein, generated out of allyl alcohol by cytosolic alcohol dehydrogenase, is responsible for this toxicity. The effect of acrolein in vitro and in vivo on the glutathione (GSH) dependent protection of liver microsomes against lipid peroxidation, and on the microsomal GSH-S-transferase (GSH-tr) in the rat was determined. In vitro incubation of liver microsomes with 5 mM acrolein for 30 sec resulted in a 2-fold activation of the GSH-tr. This activation probably proceeds via alkylation of the thiol group of the GSH-tr. In vivo administration of 1.1 mmol allyl alcohol/kg to rats did also result in a 2-fold stimulation of the GSH-tr activity. Administration of 375 mg pyrazole/kg, an inhibitor of the alcohol dehydrogenase, thus reducing the acrolein formation, prevented the in vivo stimulation of GSH-tr by allyl alcohol. This indicates that the activation of GSH-tr in vivo by allyl alcohol probably also proceeds via alkylation of the thiol group of the GSH-tr by acrolein. GSH protects liver microsomes against lipid peroxidation, probably via a free radical reductase that reduces vitamin E radicals at the expense of GSH. Incubating liver microsomes for 30 min with 0.1 mM acrolein reduced the GSH dependent protection against lipid peroxidation, probably because an essential thiol group(s) on the free radical reductase is alkylated. In vivo administration of allyl alcohol did not reduce the GSH dependent protection of the microsomes. Probably the thiol group(s) located on the free radical reductase is less accessible or less reactive than the thiol group on the GSH-tr. After administration of allyl alcohol we found no evidence for in vivo lipid peroxidation. Therefore we could not evaluate the importance of the GSH dependent protection against lipid peroxidation in vivo