The cementation of zirconia crowns is always the subject of considerations; the inability to have an adhesive bond with the material makes the fixing process always problematic. Many authors have pointed out that, on the basis of systematic reviews of the literature, the MDP-containing cements (a monomer now free on the market and usable by several companies) showed considerable advantages for the chemical bonding obtainable with the zirconia interface.
MATERIALS AND METHODS
The study published in the Operative Dentistry examined "self-adhesive" cements (cements that can be used without conditioning the dentin substrate): RelyX U-200 (RXU200; 3M ESPE, Seefeld, Germany), SmartCem 2 (SC2; Dentsply, Milford, DE, USA), and G-Cem Automix (GCA; GC, Alsip, IL, USA). Panavia 21 (PAN; Kuraray Dental Co Ltd, Osaka, Japan), cement containing MDP was chosen for control. Single crowns were performed on the same appropriately rectified abutments and the values related to the marginal precision, in microns, between the crown and the abutment, pre and post-cementation were measured. The adhesion strength was evaluated with a precision dynamometer after the samples were subjected to thermocycling to make the cementation process more similar to the natural conditions.
The marginal precision was 34.8 ± 17.4 μm (pre-cementation) and 72.1 ± 31 μm (post-cementation), no significant difference was found between the groups of cements, while the adhesion values were extremely variable, ie the highest values were recorded in the SC2 and GCA groups (1385 Pa and 1229 Pa, respectively), while the lowest values were found in the PAN and RXU200 groups (738 Pa and 489 Pa, respectively).
Not all so-called "self-adhesive" cements, or resinous cements that do not require preliminary conditioning of the dentin surface, offer equal resistance in the cementation process of zirconia crowns. The choice of cement seems to be fundamental in the cementation phase of the zirconia crowns; appropriate information should be provided by the manufacturers.
For additional informations:
Marginal Fit and Retention Strength of Zirconia Crowns Cemented by Self-adhesive Resin Cements.
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