This study investigated the effect of the storage period of alginate impressions in sealed bags after spraying with 1% sodium hypochlorite solutions on the dimensional accuracy and deformation of stone models simulating a full crown preparation with adjacent teeth. Two alginate impression products, characterized by greater or smaller contraction in 100% relative humidity, were used. The storage periods were 1 hour, 2 hours and 3 hours. Dimensional changes in the stone models obtained from the impression characterized by greater contraction in 100% relative humidity increased as the storage period increased and 2-, 3-hour storage caused deformation of the stone models. However, storage of the impression characterized by the smaller contraction for up to 3 hours did not affect the dimensional accuracy or deformation of the stone models.

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This study evaluated the interactive effect of seven different self-adhesive resin cements (Maxcem (MA), Smartcem (SM), Unicem (UN), Breeze (BR), Biscem (BI), Set (SE), Clearfil SA luting (CL)) and three different surface treatments (#600 polishing, Silica coating and tribochemical treatment) on bond strength and failure mode of zirconia (Y-TZP). Silica coating and tribochemical treatment significantly increased the bond strength of the MA, UN, BR, BI, SE and CL to the zirconia compared to surface treatment with #600. MDP monomer containing resin cement (CL) is recommended for bonding zirconia ceramics, but surface treatments do not seem to be necessary.

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Novel monomers with relatively low viscosity were synthesized and the basic investigation was performed to accurately determine their usefulness as a base monomer for composite resin or adhesive cement in dentistry. As monomers with one or two central methyl groups of Bis-GMA skeleton replaced by hydrogen, which seemingly reduced the rigidity of whole molecule, 1,1-bis[4-(2-hydroxy-3-methacryloyloxy-propoxy)-phenyl]ethane (monomer I) and bis-[4-(2-hydroxy-3-methacryloyloxy-propoxy)-phenyl]-methane (monomer II) were synthesized. The viscosities of the monomers were measured, then mechanical properties of the polymers obtained from light-curing the monomers were investigated. The following conclusions were drawn. 1) The viscosities of monomers I and II were significantly smaller than that of Bis-GMA. 2) Monomers I and II can be easily polymerized using standard light-induced initiators. 3) The polymer obtained from monomer I has almost the same strength as that obtained from Bis-GMA and TEGDMA monomer mixture. Based on the above findings, monomer I seemed to hold great promise for use as the base monomer of dental composite resin or dental adhesive cements.

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