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A luting agent may be more than a cement

      Until the beginning of the 1970’s all the profession had was zinc phosphate cement (Mizzy and DeTrey), polycarboxylate cement (Durelon) and zinc oxide and eugenol (Fynal). The use of these materials has fallen way off the charts in terms of popularity. Polycarboxylate represents about 15% of the sales where as zinc phosphate cement has fallen to 5%. In addition, zinc oxide and eugenol based cements are not recommended due to their potential for killing the odontoblastic cells.

            The replacement over the last 10 to 15 years has been glass ionomers and resin modified glass ionomers as well of course, composite resin cements. More recently, the trend has been moving towards the “CEM” luting agents. These are classified as glass ionomer containing diacrylates.

There are many reasons for the changes. However, one of the important ones relates to the indirect restorative material itself. Ceramic full crown restorations as well as veneers require an agent that till contribute to the fracture resistance of the restoration. When all ceramic restorations for example were cemented with zinc phosphate cement, the fracture rate was very unacceptable. The newer cements tend to form a mechanism for the homogenous transfer of masticatory stresses.           

The question related to this change is this: if the composite resin and glass ionomer cements (and RMGI) were so successful in terms of extended clinical longevity, why should we change to this new class (“CEM”) of luting agents? Examples of this type of luting agent included:

Unicem             3MESPE

Maxcem           Sybron/Kerr

Monocem         Shofu

Fuji Cem          GC America

There are several reasons, but perhaps the most obvious is “ease of use”. By all comparison each of those listed about are far easier to mix, place and seat. In addition there are numerous other great properties which include:

No specific treatment of the prepare tooth

High fluoride release

No postoperative sensitivity

Potentially forms a hybrid zone

Bond strength to dentin of 6-8 MPa

Easy cleanup

One-step

Self etch

Can be used for everything except veneers

2 minute working time

3-5 minute setting time

Bonds to ceramic agents

            Sounds like the near perfect luting agent and clinical experience is highly acceptable. But wait a moment……no clinical data; short-term or long-term. That’s the only disappointment.