Clinical evaluation of dental restorative materials - Part II: Modified Ryge criteria

Cvar and Ryge criteria[1] for clinical evaluation of dental restorative materials were first published in 1971 and re-evaluated in 1980 by Ryge.[2] Another post explains the original Cvar and Ryge criteria in greater detail. Also, read about the new FDI criteria in a separate post.

Modified criteria, often called modified Ryge criteria are mostly used in contemporary clinical evaluations of dental restorative materials. Modifications usually depend on the aim of the study i.e. the type(s) of restorations that are being compared. Here are some studies reporting on clinical performance of restorative materials based on modified Ryge criteria.

Gallo et al.[3] conducted a three-year clinical evaluation of two flowable composites, Tetric Flow (Ivoclar Vivadent) and Esthet-X Flow (Dentsply/Caulk) which were used to restore Class I caries lesions. The authors used the original Cvar and Ryge criteria with two additional criteria: (1) retention and (2) polishability. Table 1 presents the codes and descriptions for each criterion. It should be noted that polishability is rated using more than the original 4 codes, introducing subtle differences in rating. This may, however, affect the variability of diagnostic judgement and intra- or inter-examiner reliability as it becomes more difficult to differentiate between e.g. Bravo B-a and B-b or C and D. Also, the term “unacceptable polish” comes as a rather unexpected vague description in contrast to detailed codes A-D and it is unclear what unacceptable means. For some dentists, “Rough and dull or satin, not reflective” may be completely “Unacceptable polish”. An obvious principle adopted by Cvar and Ryge in their original criteria should also be applied when modifying these criteria by introducing new ones – keep it simple.

Table 1. Codes and descriptions of two additional criteria, as used in Gallo et al.
(Click on the table)

Poon et al.[4] conducted a 3.5-year clinical evaluation of a packable (SureFil, Dentsply DeTrey) and a conventional (SpectrumTPH, Dentsply DeTrey) composite used with a self-etch adhesive system. Not only did the authors add more criteria, they also modified the descriptions of the original Cvar and Ryge criteria. Additional criteria were: (1) Retention, (2) Surface texture, (3) Surface staining, (4) Postoperative sensitivity and (5) Gingival bleeding in Class II restorations. All criteria in this study, with the exception of Postoperative sensitivity and Gingival bleeding, were rated as Alfa (A) or Bravo (B), where A was defined as “restorations meet all clinical standards with a range of excellence” and B was “though not ideal, restorations have a range of acceptability”. The rating for Postoperative sensitivity and Gingival Bleeding were “absent” or “present”.

Swift et al.[5] compared the 3-year clinical performance of two-step total-etch adhesives (OptiBond Solo, SDS Kerr and Prime & Bond 2.1, Dentsply Caulk). Their additional criteria were: (1) Retention, codes as in Table 1, (2) Postoperative sensitivity and (3) Other failure. The latter two were rated as “none” or “present”.

Moncada et al.[6] conducted a 3-year clinical trial to compare various treatment options for Class I and II restorations (sealed margins, repair, refurbishment, replacement or no treatment). Unlike previous cited papers, Moncada et al. did not use all of the original Cvar and Ryge criteria but selected only the following: (1) Marginal adaptation, (2) Anatomic form and (3) Caries. Also, they added two new criteria: (1) Surface roughness and (2) Luster, described in Table 2.

Table 2. Codes and descriptions of two additional criteria, as used in Moncada et al.
(Click on the table)

Kihn and Barnes[7] investigated clinical longevity of porcelain veneers after 4 years. They substituted Anatomic form from the original Cvar and Ryge criteria with Postoperative sensitivity which was rates “absent” or “present”.

Hamilton et al.[8] used modified Ryge criteria to evaluate pit and fissure restorations after 1 year of clinical service. Instead of the original Caries criterion, the authors added Surface smoothness which was rated as follows:

A - As smooth as natural adjacent tooth structure
B - Not as smooth as natural tooth structure but not pitted
C - Not as smooth as natural tooth structure and pitted

Hamilton et al.[8] also modified Margin discoloration and Margin adaptation to include subrating as described in Table 3. Quantification of discoloration along the margin was used and restorations rated as B1 for less than 50% of exposed margin or B2 for greater than 50% of exposed margin. A subtle one-way catch with an explorer during the assessment of margin adaptation was tolerated and rated as A2 instead of B. Also, code D for margin adaptation (Restoration mobile, fractured or missing in part of the tooth) was not taken into account, most likely because none was found.

Table 3. Modifications of the original Cvar and Ryge criteria by Hamilton et al.
(Click on the table)

Conclusions

Based on this short literature review, it is apparent that in contemporary clinical evaluation of restorative materials and treatment modalities, the original Cvar and Ryge criteria are modified in some way based on study objectives. These modifications include:

(1) Additional criteria are introduced: Retention, Polishability, Postoperative sensitivity, Surface roughness, Surface staining, Luster, Gingival bleeding; 

(2) Not all of the original Cvar and Ryge criteria are used; 

(3) Subrating are introduced to increase the precision of clinical judgment or the quality of the original criteria is reduced either through poorer description of rating or by excluding rating.

Despite the limitations, Cvar and Ryge rating scales, with or without modifications, remain the most frequently used method of clinical evaluation of dental restorative materials and operative techniques.

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

3. Gallo JR, Burgess JO, Ripps AH, Walker RS, Maltezos MB, Mercante DE, Davidson JM. Three-year clinical evaluation of two flowable composites. Quintessence Int. 2010 Jun;41(6):497-503.

4. Poon EC, Smales RJ, Yip KH. Clinical evaluation of packable and conventional hybrid posterior resin-based composites: results at 3.5 years. J Am Dent Assoc. 2005 Nov;136(11):1533-40.

5. Swift EJ Jr, Perdigão J, Wilder AD Jr, Heymann HO, Sturdevant JR, Bayne SC. Clinical evaluation of two one-bottle dentin adhesives at three years. J Am Dent Assoc. 2001 Aug;132(8):1117-23.

6. Moncada G, Martin J, Fernández E, Hempel MC, Mjör IA, Gordan VV. Sealing, refurbishment and repair of Class I and Class II defective restorations: a three-year clinical trial. J Am Dent Assoc. 2009 Apr;140(4):425-32.

7. Kihn PW, Barnes DM. The clinical longevity of porcelain veneers: a 48-month clinical evaluation. J Am Dent Assoc. 1998 Jun;129(6):747-52.

8. Hamilton JC, Dennison JB, Stoffers KW, Welch KB. A clinical evaluation of air-abrasion treatment of questionable carious lesions. A 12-month report. J Am Dent Assoc. 2001 Jun;132(6):762-9.