Clinical Performance of a Self-Adhesive Universal Resin Cement; Initial Findings
Howard E. Strassler, DMD
Burke FJT, Crisp RJ, Richter B. J Dent Res. 2005; 84(Special Issue A): abstract no. 564.
OBJECTIVES: A self-adhesive resin cement (RelyX Unicem, 3M ESPE, Seefeld, Germany) was introduced two years ago, and, as reported (Crisp et al 2003), was found by UK general dental practitioners (GDPs), in the placement of 144 restorations, to have handling advantages over both previously used ‘conventional' and resin-based luting materials. It is the purpose of this study to evaluate the performance of this material at 24-months, in terms of retention of the restorations, marginal adaptation and staining, and post-operative sensitivity. METHODS: A questionnaire, designed for completion by the participating GDPs, was completed when the patients with restorations cemented with the self-adhesive luting material returned for their routine recall examinations. Modified Ryge criteria were used for the scoring of marginal adaptation and marginal staining. Notation, age of the restoration and pain at cementation, with any subsequent pain and duration, and the presence of any porcelain cracks were also recorded. RESULTS: To date a total 31 restorations (comprised of 13 all-ceramic, 8 metal/ceramic and 10 all-metal) of mean age 20.3 months in 30 patients have been reviewed. All the restorations were present, a crack was detected in one porcelain component and no pain at all was reported. The other results were, (where 0 = Optimal and * = unacceptable): A. Marginal adaptation: 0 = 74%, 1 = 23%, 2* = 3%, 3*= 0% B. Marginal staining: 0 = 77%, 1 = 20%, 2 = 3%, 3* = 0% CONCLUSIONS: This initial report suggests that the material under investigation is performing satisfactorily in UK general dental practice after 20-months. However a longer evaluation period and a larger sample are needed to ensure continued performance.
As clinicians, the use of adhesive restorative materials is a standard of care. Manufacturers continually promise that the latest materials will exceed our expectations in their clinical success. Unfortunately, in many cases these new materials have not been well tested before they have been made available, and within a short period of time improved versions of the same product supplant the product we had just started using. It leads one to wonder what will happen with the restorations that have been placed with the “first generation” of a given product. While we can have a problem with direct-placement restorations when the latest bonding system does not meet our clinical expectations, it is more of an issue when the new product is a cement for indirect restorations. If the cement does not work as advertised the restoration will fail prematurely. As clinicians we take risks when we use new materials, and we would be well served to seek out clinical studies demonstrating the efficacy of these materials. Currently we are in the era of self-etching, self-adhesive systems. These two abstracts (a sampling of many) explore the evaluation of self-adhesive resin cements. The author chose one research study that was in vitro and one study that was in vivo to compare the results seen both on the bench top and when restorations are placed in patient’s teeth.
Currently the most common cements are resin-modified glass ionomer, etch-and-rinse adhesive dual-cure resin cements, and self-adhesive resin cements. The in vitro study performed at the University of Washington by Palacios and colleagues compared a resin-modified glass-ionomer cement (RelyX Luting, 3M-ESPE, St. Paul, MN), an etch-and-rinse adhesive resin cement (PANAVIA F 2.0 and ED PRIMER A & B, Kuraray America Co, New York, NY) and a self-adhesive resin cement (RelyX Unicem, 3M ESPE) when cementing Procera® (Nobel Biocare, Yorba Linda, CA) crowns to extracted human molars. The study design was well thought out and is relevant to what we see as clinicians. The results demonstrated no significant differences between the three cements. All three luting agents are capable of retaining zirconium-oxide crowns successfully.
The second abstract is a clinical research study evaluating the self-adhesive resin cement, RelyX Unicem, in the placement of indirect restorations including porcelain-fused-to-metal crowns, all-ceramic crowns, and all-metal crowns. This is a good clinical study because the researchers evaluated these restorations at 2 years for retention, marginal adaptation and staining, and postoperative sensitivity. Thirty-one restorations were evaluated, with 97% having acceptable margins. Postoperative sensitivity was not a problem with the restorations at the last recall. The conclusion was that this universal self-adhesive resin cement was performing satisfactorily after at least 20 months.
When cementing restorations, the fewer the steps and the easier a cement is to mix, the higher the expectation would be for improved clinical results in comparison to older cements. For those who remember mixing zinc phosphate cement on a cooled glass slab, incorporating small increments and mixing the cement over a large surface area of the slab to a consistency that was determined by using the cement spatula to determine viscosity, the introduction of easy-to-mix (in most cases self-mixing or mixing in a capsule with an automatic mixer) cements has been a fantastic change. Now that there is adequate research available, the change to the latest generation of cements makes sense. From both of these research studies it can be expected that a self-adhesive resin cement will be clinically successful in the cementation with any laboratory-fabricated restoration.
Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics, and Operative Dentistry
University of Maryland Dental School, Baltimore, Maryland