Crown retention and flexural strength of eight provisional cements.
BACKGROUND
Few studies have compared the retention of resin-based and zinc-oxide noneugenol provisional cements. Crown retention testing is difficult and variable; therefore, a simpler method of testing by using flexural strength is indicated.


OBJECTIVE
The purpose of this study was to measure the retention of base metal alloy castings to dentin provided by 8 provisional cements (3 resin-based and 5 zinc oxide) and correlate the retention to their flexural strength.


METHODS
Flexural strength specimens (2.5 x 2.5 x 22 mm) were made of each cement. The specimens were placed in a 3-point bending testing mode and loaded at 1 mm/min until failure. Ten extracted teeth were milled to a standardized complete crown preparation, fitted with Rexillium III castings, and cemented with each provisional cement. The specimens were subjected to a tensile load (1 mm/min) until failure in a universal testing machine. The flexural strength for each cement was calculated in MPa and correlated to the retention. A 1-way ANOVA and Tukey HSD post hoc analysis were used to determine significant intergroup differences (alpha=.05). Linear regression was used to correlate flexural strength and crown retention (alpha=.05).


RESULTS
Significant differences were found in the flexural strengths and retention provided by the various cements. Flexure strength was correlated with cement retention for resin-based cements (r=0.998) but not zinc-oxide noneugenol cements (r=0.058).


CONCLUSIONS
Based on a 20-degree preparation, stronger cements provide increased retention. Therefore, the desired amount of retention should be based on both the cement and a clinical evaluation of the preparation.
School of Dentistry, University of Alabama at Birmingham, Birmingham, AL 35295-0007, USA.
Nathaniel C
NC
Lawson
John O
JO
Burgess
Donald
D
Mercante
D002858:Chromium Alloys / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D003722:Dental Alloys / Q000737:chemistry; D003738:Dental Cements / Q000737:chemistry*; D017268:Dental Prosthesis Retention; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D015034:Zinc Oxide / Q000737:chemistry
D002858:Chromium Alloys; D003188:Composite Resins; D003722:Dental Alloys; D003738:Dental Cements; D019279:Resin Cements; C449162:zinc oxide-non-eugenol cement; C036884:Rexillium III; D015034:Zinc Oxide