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Clinical effectiveness of adhesives - simpler may not be better

Steven Armstrong DDS, PhD .


Systematic Review Conclusion

Glass ionomers, followed by three-step etch-and-rinse and two-step self-etch adhesives, had the highest retention rate in Class V restorations.

Critical Summary Assessment

A review lacking trial quality assessment finds that glass ionomers have a significantly higher retention rate than two-step etch-and-rinse and one-step self-etch adhesives in NCCLs.

Evidence Quality Rating

Good Evidence

Structured Abstract

Clinical Questions:

Do simplified adhesives retain restorations as effectively as conventional three-step adhesives when restoring non-carious Class V lesions (NCCLs)?

Review Methods:

A search from January 1998 to May 2004 of peer-reviewed journals and abstracts from 15 international meetings found 85 university centered clinical trials that reported retention rates of adhesively restored non-carious Class V lesions.

Main Results:

All 35 peer-reviewed papers and 50 abstracts selected from the literature were included in the review. Fourteen trials produced 23 retention rate curves from 11 three-step etch-and-rinse adhesives with 81% meeting retention criteria of 90% at 18 months (ADA Acceptance Program Guidelines, program discontinued in 2008) and an overall annualized failure rate (AFR) of 4.8% (±4.2%). Twenty-five trials produced 43 curves from 13 two-step etch-and-rinse adhesives with 51% meeting retention criteria and an AFR of 6.2% (±5.5%). Fourteen trials produced 17 curves from 9 two-step self-etch adhesives with 71% meeting retention criteria and an AFR of 4.7 (±5.0%). Thirty-two trials produced 38 curves from 17 one-step self-etch adhesives with 70% meeting retention criteria and an AFR of 8.1% (±11.3%). Eighteen trials produced 26 curves from 2 glass ionomer adhesives and 7 restoratives with 96% meeting retention criteria and an AFR of 1.9% (±1.8%). The AFR of glass ionomers was significantly lower than two-step etch-and-rinse (p = 0.0176) and one-step self-etch (p = 0.0003) adhesives.


Glass ionomers bond most effectively and durably to tooth tissue. Three-step etch-and-rinse and two-step self-etch adhesives showed a clinically reliable and predictably good clinical performance. Although there is a tendency from industry to develop adhesives with simplified application procedures, such a simplification so far appears to induce loss of effectiveness. In future, a standardized study design should be developed for clinical trials that evaluate the performance of adhesives so that results can be compared.

Source of Funding:

This study was supported in part by the Toshio Nakao Chair with two authors awarded as chairholders.


Importance and Context:

The dental bonding agent affects the clinical effectiveness of any direct or indirect adhesive restoration. Knowing which agent to use and then how to apply it can be a challenging, and confusing, process. The reasons are many that contribute to this confusion, including inadequate dental school training, exaggerated manufacturer product claims, a vast array of adhesive systems with their own application protocols, and the large amount of conflicting scientific literature on the topic. In recent years, simplified adhesive systems have become more popular. However, presently there is no definitive evidence to suggest these systems work as well or are superior to etch-and-rinse multi-step adhesives.

Strengths and Weaknesses of the Systematic Review:

This systematic review includes the richest data set of clinical trials yet available in the field of adhesive dentistry. However, according to AMSTAR and QUOROM, several of the criteria were not met for methodological quality and reporting of systematic reviews. Two individuals extracted data with no exclusion of studies or disagreement regarding data, since the only inclusion criteria was that the retention rate of adhesives in cervical non-carious Class V lesions from university centered clinical trials was reported (author communication). Ten of the 85 studies included data on retention rates of carious Class V and Class III lesions. This data were included in the analysis for determining the AFR of adhesives in NCCLs. Only English language papers were included. The authors failed to fully characterize and assess the methodological rigor and scientific quality of the studies. Randomized, controlled trials comparing conventional three-step adhesives to simplified adhesives were not separately analyzed. Additionally, the authors did not include other patient-oriented clinical measures related to adhesive effectiveness, such as marginal staining or sensitivity.

Strengths and Weaknesses of the Evidence:

The authors reviewed a large number of clinical trials that reported on objective patient-oriented measures of adhesive bond effectiveness, i.e., restoration retention. Many studies had heterogeneity in both study design and outcomes. Not all trials included a control or comparison adhesive group. A majority of the studies in this review were abstracts that lacked study detail. Several full papers lacked important details.

Implications for Dental Practice:

Glass ionomers, particularly resin-modified glass ionomers, should be considered for the restoration of NCCLs. However, this consideration should be weighed against their inferior esthetics and resistance to abrasion and erosion relative to resin-based composite. Although protocols for adhesive systems have been simplified, the effective retention rate for these reduced-step systems still remained lower than that of the traditional three-step etch-and-rinse adhesives.

Critical Summary Publication Date:


These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association © 2019