Retention of metal-ceramic crowns with contemporary dental cements.
BACKGROUND
New types of crown and bridge cement are in use by practitioners, and independent studies are needed to assess their effectiveness. The authors conducted a study in three parts (study A, study B, and study C) and to determine how well these new cements retain metal-ceramic crowns.


METHODS
The authors prepared teeth with a 20-degree taper and a 4-millimeter length. They cast high-noble metal-ceramic copings, then fitted and cemented them with a force of 196 newtons. The types of cements they used were zinc phosphate, resin-modified glass ionomer, conventional resin and self-adhesive modified resin. They thermally cycled the cemented copings, then removed them. They recorded the removal force and calculated the stress of dislodgment by using the surface area of each preparation. They used a single-factor analysis of variance to analyze the data (alpha = .05).


RESULTS
The mean stresses necessary to remove crowns, in megapascals, were 8.0 for RelyX Luting (3M ESPE, St. Paul, Minn.), 7.3 for RelyX Unicem (3M ESPE), 5.7 for Panavia F (Kuraray America, New York) and 4.0 for Fuji Plus (GC America, Alsip, Ill.) in study A; 8.1 for RelyX Luting, 2.6 for RelyX Luting Plus (3M ESPE) and 2.8 for Fuji CEM (GC America) in study B; and 4.9 for Maxcem (Kerr, Orange, Calif.), 4.0 for BisCem (Bisco, Schaumburg, Ill.), 3.7 for RelyX Unicem Clicker (3M ESPE), 2.9 for iCEM (Heraeus Kulzer, Armonk, N.Y.) and 2.3 for Fleck's Zinc Cement (Keystone Industries, Cherry Hill, N.J.) in study C.


CONCLUSIONS
Powder-liquid versions of new cements were significantly more retentive than were paste-paste versions of the same cements. The mean value of crown removal stress for the new self-adhesive modified-resin cements varied appreciably among the four cements tested. All cements retained castings as well as or better than did zinc phosphate cement.


CONCLUSIONS
Powder-liquid versions of cements, although less convenient to mix, may be a better clinical choice when crown retention is an issue. All cements tested will retain castings adequately on ideal preparations because the corresponding removal stresses are comparable with or higher than those associated with zinc phosphate. Powder-liquid resin-modified glass ionomer cement, selected self-adhesive modified-resin cements and conventional resin cements provide additional retention when desired.
Johnson
Glen H
GH
Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, Wash. 98195-7456, USA. gjohnson@u.washington.edu
Lepe
Xavier
X
Zhang
Hai
H
Wataha
John C
JC
D002484:Cementation / Q000379:methods; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D003738:Dental Cements / Q000737:chemistry*; D017268:Dental Prosthesis Retention; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D015036:Zinc Phosphate Cement / Q000737:chemistry
C542562:BisCem cement; D020770:Compomers; D003188:Composite Resins; D003738:Dental Cements; C061504:Flecks; D005899:Glass Ionomer Cements; D006047:Gold Alloys; C515955:Maxcem; D016876:Metal Ceramic Alloys; C438843:Panavia-Fluoro; C483701:Rely X Unicem; D019279:Resin Cements; C084550:Vitremer; D012834:Silver; D010165:Palladium; D015036:Zinc Phosphate Cement