Cementation of indirect restorations: most recent data on resin modified glass ionomers, and self-adhesive resin cements

The purpose of the luting procedure is to achieve a durable bond between tooth and restoration and a good marginal adaptation of both. Adhesive cementation is the best current luting approach for all – ceramic restorations. Resin cements are superior to traditional cements in their sealing ability. Adhesive cementation in the past required the use of total-etch, or certain 2 bottle self-etches for successful bonding to dentin. The systems varied in technique sensitivity, and ideally required isolation to control moisture (from saliva, sulcular fluid, and blood), which can result in deterioration of the bond. The current trend is toward self-etch which works by not requiring a conditioning and/or a bonding system or the need for dental dam isolation during placement of the restoration.  Some method of blood, saliva, and water isolation is still recommended.

The mechanism of action of the self-etch resin results in both micromechanical and chemical bonding, according to Terry, Leinfelder, and Trajtenberg.[1] The etching and priming occur simultaneously. Most often this results in a lack of post-operative sensitivity.

For ceramics, to enhance wettability for the self-etch resin, the internal surface may be roughened with either air-abrasion, or acid-etched, followed by a silane coupling agent, after which the restoration is luted into or onto the tooth. Surface treatment procedures (as above) cannot be utilized for high-strength polycrystallanics (aluminum oxide, zirconium). Nevertheless, if the latter materials are treated with a silica coating (brand name Rocatec-CoJet Sand (3M ESPE)), the shear bond strength would be increased. Long term studies[2] indicate that silica/silane coatings fail to provide durable bonds to densely sintered aluminum oxide ceramic, but may be successfully implemented for zirconia ceramics.

To avoid weakening of bond strength, it is important to avoid contamination of pre-treated ceramic surfaces. If contaminated, one should clean with phosphoric acid for 15 seconds and wash. The Terry, Leinfelder, and Trajtenberg article[3] is an excellent article with a very extensive bibliography and should be referred to by serious clinicians seeking optimum technique.

In 2007, de Rijk and Simon published an excellent paper[4]. To compare several of the new self-adhesive cements to a cement that requires a bonding agent, the authors conducted the hollow-notch shear bond strength test. Of the 5 cements tested: BixCem, GCem, Max Cem, RelyX Unicem, and MultiLink (which requires a dentin bonding agent), MultiLink had double the shear bond strength of the other 4 self-adhesive cements. The study seemed to indicate the potential for great variability. It is not uncommon for self-adhesive systems, be they dentin bonding agents or self-adhesive resin cements, to show a coefficient of variation in the order of 50% or greater. The authors conclude that “for a good bond to dentin, the use of a bonding agent is recommended when a resin cement is used. When the preparation design assists in the retention of the restoration, almost any of the new cements will work adequately.”[5]

Reality reports on product studies of at least 3 months use by at least 10-12 clinicians. They divide resin cements into 4 categories: Dual-Cured Only; Light-Cured/Dual-Cured; Light-Cured Only, Self-Cured Only. Their ratings for each of their categories were as follows:

Dual-Cure Only: The 2 highest rated were: Panavia F 2.0 (Kuraray), and Multilink Automix (Ivoclar Vivident). The next in order was RelyX ARC (3M ESPE). This was followed by RelyX Unicem (3M ESPE), and EMBRACE WetBond Resin Cement (Pulpdent). RelyX Unicem is now available in a Clicker Dispenser, which was voted the top dispensing system in 2008 by The Dental Advisor.

Based on the review of the literature and a dentist’s desire to avoid sensitivity, to avoid a soluble cement, and to get adhesion, the author has concluded that if one were cementing a metal inlay or a PFM crown or a zirconium based crown, one would most likely use a resin modified glass ionomer. The advantages of the resin modified glass ionomer (FujiCem, RelyX Luting Plus) are that there is fluoride release and high strength.

If one were cementing ceramic crowns as well as PFM or zirconia, one would use the self-adhesive resin cements. A recent review (2007) by CRA[6] reported on self-adhesive resin cements (as well as resin modified glass ionomers). (For technique simplicity and to avoid post-operative sensitivity, one would probably eliminate total-etch from consideration.) This leaves either a self-etch primer, plus the resin cement (Multilink Automix, Panavia F 2.0) or self-adhesive cements (Breeze, Embrace, WetBond, G-Cem, Maxcem, Monocem, Multilink Sprint, RelyX Unicem, and RelyX Unicem Clicker).

If one were to use either Multilink Automix or Panavia, there is a first step requiring a self-etch primer before using a cement. Even with the self-adhesive cements, according to Harrison, et al, “it does appear that for a good bond to dentin, a use of a bonding agent is recommended when a resin cement is used.” [7]

According to CRA, of the self-adhesive resin cements, RelyX Unicem Applicap, and GCem tested best. However, self primer adhesives Multilink Automix and especially NX3 w/Optibond All-In-One tested significantly stronger in shear bond strength to dentin than the self-adhesive cements. Lastly, the total etch cements Variolink II and NX3 with Optibond Solo Plus tested the strongest. Since these total-etch cements can cause sensitivity, it might be better to use Optibond All-In-One (self etch) and not take the risk of sensitivity.

The CRA article did not review Bifix QM (Voco), which lutes metal and non-metal alloys, ceramics, and resin restorations. It can be used with light cure or as a chemical cure. It has the highest transverse strength with light curing, with Variolink II and Multilink Automix right behind. With chemical curing, it is also the highest with Calibra equal and Variolink II right behind.FuturabondDC (a self etching dual curing bond to dentin) is considerably stronger in MPa to Xeno IV, andAdheSEDC.

CRA data shows most cement expansion takes place within the first 1 to 2 weeks in vitro. All self-adhesive resin cements reviewed expanded less than 2% by 2 months, indicating they are ok to use with all ceramic crowns. In the same publication, CRA reported on 149 of 180 clinicians who used self etch primer resin cements[8]. The 2 most commonly used were RelyX Unicem and Maxcem. Of the 2, RelyX is considerably stronger. G-Cem is still stronger, but requires capsule trituration. Overall clinical experience was reported as good to excellent, with low to no post-op sensitivity, few to no debonds, and easy to use and clean up. They all lack significant fluoride release.

Summary: Where operative simplicity and time are important, based on the CRA data, this author would be most comfortable with Multlink Auto Mix or NX3 with OptiBond All-In-One (self-etch). Where high strength is needed, one might use  NX3 with OptiBond Solo Plus (total-etch) . Where one prefers a self-adhesive resin cement and fluoride release is not important, the author prefers Breeze, because of its simplicity. One would still use the technique of double-etching the enamel for greater marginal strength and rubbing in the self-etch primer several times to increase bond strength.

It should be repeated that cavity sterilization before cementation is important. 2% chlorhexidine (Consepsis (Ultradent Products)) rinse is recommended. If not using rubber dam, throat packing with gauze to prevent swallowing of the restoration is always recommended.