1221 Crown Retention After Long-Term Specimen Aging For Self-Adhesive Modified-Resin Cements

Saturday, March 24, 2012: 8 a.m. - 9:30 a.m.
Presentation Type: Oral Session
G.H. JOHNSON, K. SHOR, and M.H. KRONSTRÖM, University of Washington, Seattle, WA

Objectives:   Evaluate crown retention for self-adhesive, modified resin (SAMR) cements using long-term aging to assess durability. 



Methods:   Extracted human molars prepared with a flat occlusal, 20-degree taper and 4mm axial length.  Preparation surface area determined and specimens distributed by areas equally into three groups (n=13). See J Am Dent Assn 2009;149;1125-1136.   High noble alloy crowns (Special White, Ceramco) were cast. Non-eugenol temporary cement cleaned from preparations; teeth rinsed, dried, but not desiccated.  SAMR cements: 3M-ESPE RelyX Unicem Aplicap (RXU), RelyX Unicem 2 Automix (RXU2) and SDS/Kerr Maxcem Elite (MCE).  20 Kg cementation force used.  Aging achieved by thermocycling between 5-55 °C for 5000 cycles and repeated monthly for 6 months (30,000 cycles).  Castings were removed at 0.5mm/min. Removal force and nature of cement failure recorded.   Dislodgement stress calculated using surface area.   



Results:   Mean crown removal stress with SD's given below.  One-way ANOVA with mean comparisons revealed significant differences (≠) of RXU and RXU2 from MCE (P=0.006). The mode of failure for 37 of 39 specimens was cement residing on the internal of the crowns with little on dentin.  Χ2=1.054,P=0.590.








Crown Removal Stress (MPa)

5.0 (1.6)


4.5 (1.0)

3.4 (1.0)

Location of cement (%n)

92%-on crown;

8%-on crown & dentin


100%-on crown


92%-on crown;

8%-on crown & dentin



Conclusions:   (1) RXU and RXU2 achieved higher crown removal stresses than MCE, but (2) stresses for all three were greater than that shown for zinc phosphate (J Am Dent Assn 2009;149;1125-1136), thus clinically acceptable.  (3) Cement was uniformly found on the internal of the crown with very little on the dentin.  Although thought to be self-adhesive to dentin, the attachment of the SAMR cement is predominantly to the internal of the crown.  (4) Long-term aging of cemented crowns supports durability of crown retention.  Supported by 3M-ESPE.


This abstract is based on research that was funded entirely or partially by an outside source: 3M ESPE #63-0709

Keywords: Adhesion, Aging, Cements and Prosthodontics
See more of: Fixed Prosthodontics
See more of: Prosthodontics Research