title: The effect of a resin-based sealer on crown retention for three types of cement.
abstract: 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.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of Washington, Seattle, 98195-7456, USA. gjohnson@u.washington.edu
authors.forename: Glen H
authors.initials: GH
authors.lastname: Johnson
authors.forename: Lance R
authors.initials: LR
authors.lastname: Hazelton
authors.forename: David J
authors.initials: DJ
authors.lastname: Bales
authors.forename: Xavier
authors.initials: X
authors.lastname: Lepe
mesh_terms: 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
chemical_list: 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