The effect of a resin-based sealer on crown retention for three types of cement.
BACKGROUND
In an effort to control postoperative sensitivity, dentin sealers are being applied following crown preparation with little knowledge of how crown retention might be affected. A previous study demonstrated no adverse effect when using a glutaraldehyde-based sealer, and existing studies have shown conflicting results for resin-based products.


OBJECTIVE
This study determined if a resin sealer applied to prepared dentin affected retention of cemented castings when using 3 common types of luting agents.


METHODS
Extracted human molars (n=55) were prepared with a flat occlusal, 20-degree taper, and 4-mm axial length. The axial surface area of each preparation was determined and specimens were distributed equally among groups (n=11). A 2-step, single-bottle adhesive system (One Step) was used to seal dentin following tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer) specimens that required use of adhesive with cementation. Using ceramometal high noble alloy (Olympia), a casting was produced for each specimen and cemented with a seating force of 20 Kg using either zinc phosphate (Fleck's), glass ionomer (Ketac-Cem) or modified-resin cement (Resinomer) with the single-bottle adhesive. Castings were thermal cycled at 5 degrees C and 55 degrees C for 2500 cycles; then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with alpha=.05. The nature of failure was also recorded and the data analyzed with a chi-square test.


RESULTS
Mean dislodgment stresses for unsealed and sealed conditions were 3.7 +/- 1.0 and 2.2 +/- 0.8 MPa for zinc phosphate; 2.7 +/- 1.2 and 4.2 +/- 0.9 MPa for glass ionomer, respectively (P<.001). Retentive stress of castings cemented with modified-resin cement was 6.4 +/- 1.7 MPa. With resin sealer in combination with zinc phosphate, cement resided totally on castings in 82% of the situations and was on both surfaces without sealer. The tooth failed before casting dislodgment in 9 of 11 specimens cemented with modified-resin cement.


CONCLUSIONS
Resin sealer decreased casting retentive stress by 42% when used with zinc phosphate. However, sealer use resulted in 55% increased retention when used with glass ionomer. The modified-resin cement produced the highest mean dislodgment stress, nearly always exceeding the strength of the tooth.
Johnson
Glen H
GH
Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, 98195-7456, USA. gjohnson@u.washington.edu
Hazelton
Lance R
LR
Bales
David J
DJ
Lepe
Xavier
X
D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D003738:Dental Cements / Q000737:chemistry*; D017268:Dental Prosthesis Retention; D019232:Dental Restoration Failure; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008277:Magnesium Oxide / Q000737:chemistry; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008689:Methacrylates / Q000737:chemistry; D011076:Polycarboxylate Cement / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D019246:Tooth Preparation; D015034:Zinc Oxide / Q000737:chemistry; D015036:Zinc Phosphate Cement / Q000737:chemistry
C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D003738:Dental Cements; D017220:Dentin-Bonding Agents; C061504:Flecks; D005899:Glass Ionomer Cements; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D008689:Methacrylates; D011076:Polycarboxylate Cement; D019279:Resin Cements; C110709:resinomer; D008277:Magnesium Oxide; C049241:olympia; D015036:Zinc Phosphate Cement; C040235:Ketac-cem; D015034:Zinc Oxide