Clinical Applications of Self-Adhesive Resin Cements
These materials have become so versatile they can be used with very few exceptions.
Since the invention of the indirect dental restoration, there has always been a need to cement them into or onto the tooth. Just as the restorative materials have continually evolved, so too have the cements or retaining media. While glass-ionomer-based cements still retain the lion’s share of the cementation market,1 resin cements have long been valued for their high retentive strengths, resistance to wear,2 and insolubility. This makes them ideal for short clinical preparations with limited retention. One factor that has discouraged greater use of resin cements has been the need to etch the preparation and apply a separate adhesive or bonding agent. This requirement helps achieve desirable bond strengths but can occasionally lead to postoperative sensitivity. Self-etching adhesives have been helpful in reducing the sensitivity related to etching but have introduced a new challenge of adhesive/cement incompatibilities.
Yet another concern with resin cementation is their general intolerance to moisture. Usually, when a dry field is not present, conventional resin cements are contraindicated. The latest advancement in luting cements is what has been referred to as a self-adhesive resin cement. These materials have been developed to take advantage of some of the best properties of modern resin cements with the added advantages of improved tolerance to moisture and not requiring a separate adhesive application. Even though bond strengths appear to be less than conventional resin cements (ones that require a separate adhesive), 18% of dentists now report using self-adhesive resin cements on a regular basis.3They can be used for metal-containing crowns and bridges including porcelain-fused-to-metal (PFM) and full-cast metal, as well as ceramic and metal inlays and onlays. In fact, they can be used in virtually any clinical cementation situation except possibly bonding porcelain laminates or resin-bonded bridges. In the author’s opinion, there simply is no easier and more cost-effective way to make use of a resin cement.
The earliest versions of the self-adhesive resin cement were distributed by manufacturers in unit-dose capsules that required mixing in a standard triturator and were dispensed with a special applicator (Figure 1). These do offer the advantages of precise dosing, no cross-contamination, and minimal product waste. However, the capsules seem to work best for cementation of a single unit, such as a crown or inlay. Cementation of a multi-unit case or long-span bridge can be challenging because multiple capsules may be required. Some manufacturers have attempted to address this limitation by making larger single-dosing units available for multi-unit cases.
However, the best dispensing solution for these larger cases seems to be the latest delivery innovation—the automix syringe. This allows the user to precisely control the amount of cement that is dispensed while the disposable mixing tip delivers it properly mixed and ready to use. Material waste with such devices is minimal. Since self-adhesive resin cements are dual-cured, they are also suitable for cementation of posts into endodontically treated teeth. For post cementations, manufacturers have developed two convenient delivery options. One uses a snap-on “elongation” cannula for use with single-dose capsules (Figure 2), and the other one is an “extension tip” for automix syringes (Figure 3). Both allow the self-adhesive resin cement to be delivered directly into the root canal.
Clinical Case Applications
A routine single-crown cementation can be completed using a self-adhesive resin cement in either a single-dose or an automix syringe delivery. Working and setting times are different for each product and brand; however, the clinical steps are very similar. In the case demonstrated here, a porcelain-fused-to-gold crown was seated on tooth No. 14 (maxillary left first molar) with a self-adhesive resin cement dispensed from an automix syringe (G-CEM™ Automix, GC America, http://www.gcamerica.com). It is completed as described below.
Shade determination is normally the first step. However, because PFM crowns are opaque, they would not normally require any special shade considerations (for the luting cement). For this case, a syringe of G-CEM™ Translucent-Automix was prepared by “bleeding” to ensure flow and to remove air and contaminants from the orifices of the base and catalyst tubes. Bleeding is generally only necessary before the first clinical use of the syringe or after an extended interval since the last use. A standard mix-tip was then applied to the syringe (Figure 4). The crown was tried in clinically, adjusted, repolished, and the intaglio surface was cleaned. As a PFM crown, no special surface treatment of the intaglio surface is generally required. However, recent studies show that a significant improvement in the bond strength of self-adhesive resin cements may be possible for metal or oxide-based ceramic substrates (zirconia or alumina) if an intermediary primer such as Z-PRIME Plus™ (Bisco Dental, http://www.bisco.com) is applied.4When bonding to glass-based ceramics such as feldspathic porcelain, lithium disilicates (such as IPS e.max® Press, Ivoclar Vivadent, http://www.ivoclarvivadent.com) or other reinforced porcelains, a silane treatment of the intaglio surface is recommended. For this case, the resin cement was extruded directly from the mix-tip into the crown (Figure 5), liberally coating the intaglio surface. The tooth was isolated and the loaded crown was seated into place immediately (Figure 6). Working time for the automix version of G-CEM is approximately 3 minutes and 30 seconds from the start of the mix (at room temperature). To facilitate cleaning, the excess cement that extrudes from the seated crown is cured briefly for 2 to 4 seconds or allowed to self-cure until it reaches the gel stage. The excess cement can now be easily removed using a scaler or curette (Figure 7) and each contact flossed. After the initial cement removal, the manufacturer recommends that the crown margins be cured definitively for 20 seconds on each surface for light-conducting restorations or allowed to self-cure for 4 minutes for opaque restorations. To ensure complete setting, the author prefers to do both. After 4 minutes, the final fit, contacts, and occlusion were rechecked one last time to ensure nothing had changed during the cementation (Figure 8).
Endodontic Post Case
For endodontic posts, self-adhesive resin cements can provide an easy and predictable method for cementation. The use of this new type of resin cement eliminates both the need for etching the root canal and the application of a separate adhesive. As previously mentioned, virtually any type of metal, ceramic, or fiber post can be successfully cemented with a self-adhesive resin cement. For the case demonstrated here, the author chose to use a light-conducting fiber post (RelyX™ Fiber Post, 3M ESPE, http://www.3mespe.com) cemented with G-CEM Automix. A rubber dam was applied. Gutta-percha was removed from the coronal portion of the root canal using an end-cutting, Universal Starter Drill (3M ESPE). leaving an adequate apical seal. The final post preparation was completed using a #1-sized matched post drill. Following the cement manufacturer’s directions, the root canal was irrigated with a standard sodium hypochlorite solution, rinsed, and dried. The manufacturer specifically cautions against etching or using other irrigants such as EDTA, hydrogen peroxide, etc, when a self-adhesive resin cement is used. The post was tried in ensure a passive fit and then cleaned with alcohol and dried (Figure 9). An “extension” tip was applied to the cement syringe and the resin cement was applied to the post and extruded directly into the root canal/post preparation (Figure 10). The post was immediately seated into the prepared canal and excess cement was removed with a small spoon excavator. The cement within the post space was cured for 20 seconds using the light conduction of the post itself to carry light down into the root canal (Figure 11). Once the post was stabilized by the cured cement, the remaining tooth structure was etched, a light-cured adhesive was applied and thixotropic dual-curing core build-up material (Build-It® FR™ Fiber Reinforced Core Build Up Material, Pentron Clinical Technologies, http://www.pentron.com) was backfilled around the fiber post and light-cured according to the manufacturer’s instructions. The rubber dam was then removed and the tooth was ready to be prepared for the crown or other definitive indirect restoration (Figure 12).
While still relatively new, self-adhesive resin cements seem to offer clinicians an agent that is relatively easy to use and is suitable for the cementation of nearly all current indirect metal, composite, and porcelain restorations and endodontic posts; the only possible exceptions are bonded porcelain veneers and resin-bonded bridges. These cements are dual-cured, have higher tolerances for moisture, and are self-adhesive, meaning that etching or separate adhesives are not required. Manufacturers offer clinicians convenient single-dose and multiple-use dispensing options. Because many clinical applications will not be heavily influenced by the shade of the cement, an extensive palette of opacities and shades is not required. However, there seems to be a sufficient number available to meet current clinical needs. Although physical properties do seem to vary significantly from brand to brand and more testing is indicated, in vitro and early in vivo clinical tests of self-adhesive resin cements show satisfactory results.5-7 When the dentist believes that a resin cement may be clinically appropriate, he or she may now elect to use a self-adhesive resin cement with confidence.
1. Self-adhesive resin cements: A replacement or an alternative? Clinicians Report. 2009;2(11):1-3.
2. Belli R, Pelka M, Petschelt A, Lohbauer U. In vitro wear gap formation of self-adhesive resin cements: a CLSM evaluation. J Dent. 2009;37(12):984-993.
3. Christensen GJ. Why use resin cements? J Am Dent Assoc. 2010;141(2):204-206.
4. Millan G, Raad M, Attar M, Nathanson D. Primer effect on bond strength of resin cements to zirconia. J Dent Res. 2010;89(Special Issue A):Abstract 018.
5. Behr M, Rosentritt M, Wimmer J, et al. Self-adhesive resin cement versus zinc phosphate luting material: a prospective clinical trial begun 2003. Dent Mater. 2009;25(5):601-604.
6. Naughton W, Latta M. Shear bond strength of self-adhesive resin cements to dentin. J Dent Res. 2010;89(Special Issue A):Abstract 201.
7. Malmstron H, Cacciato R, Yunker M, et al. A 24-month clinical evaluation of a self-adhesive resin cement. J Dent Res. 2010;89(Special Issue A):Abstract 444.
About the Author
Mark L. Pitel, DMD
Clinical Associate Professor
New York University College of Dentistry
Post Graduate CDE Esthetic Program
New York University College of Dentistry
New York, New York
Poughkeepsie and Manhattan, New York