Clinical evaluation of dental restorative materials - Part I: Cvar and Ryge criteria

Nearly 40 years ago John F. Cvar and Gunnar Ryge wrote that, although mechanical properties of the available dental restorative materials were well known, clinical scientific data were scarce. The lack of evidence-based studies was the result of the lack of well-defined measures to evaluate the clinical performance of dental materials. As a fast and relatively reliable solution, Cvar and Ryge developed the rating scales which assess five characteristics of dental restorative materials indicative of their aesthetics and functionality.(1) With some modifications, these criteria are still used in clinical evaluation of dental materials and operative techniques. Read about modified criteria and the new FDI criteria in separate posts.

The original Cvar and Ryge criteria or characteristics used for material clinical evaluation are color match, cavo-surface marginal discoloration, anatomic form, marginal adaptation and caries. Codes Alfa, Bravo, Charlie and Delta are used to rate the restorations according to the assigned descriptive values for each characteristic (Table 1). The rating is conducted in a clinical setting, usually by two examiners (dentists) and a recorder (e.g. dental assistant), by visual inspection of the restoration with the use of a mirror if necessary. In addition, an explorer is used to rate marginal adaptation and the presence of caries.

In 1980, Ryge published another paper on clinical criteria in which he systematically set out an approach in clinical assessment of restorative materials using the original Cvar and Ryge criteria.(2) In addition to the previously developed rating scales, Ryge introduced a classification of restorations. The four categories are:

1. Restorations within a range of excellence,
2. Restorations which are acceptable although showing minor deviations from the ideal,
3. Restoration which should be replaced for preventive reasons to avoid the likelihood of future damage and
4. Restorations which require immediate replacement.

Table 1. Original Cvar and Ryge criteria used to evaluate non-metallic restorations. (Click on the table)

References

1. Cvar and Ryge criteria for the clinical evaluation of dental restorative materials. First published in U.S. Department of Health, Education, and Welfare, U.S. Public Health Service 790244, San Francisco Printing Office 1971:1–42. Reprinted in Clinical Oral Investigations 2005;9:215–232.

2. Ryge G. Clinical criteria. Int Dent J 1980;30:347-58