Codigo Civil Para El Df

Retention of zirconium oxide ceramic crowns with three types of cement
Rosario P. Palacios, DDS, MSD,a Glen H. Johnson, DDS, MS,b Keith M. Phillips, DMD, MSD,c and Ariel J. Raigrodski, DMD, MSd School of Dentistry, University of Washington, Seattle, Wash Statement of problem. Information about the retentive strength of luting agents for zirconium oxide–based
crowns is limited. It is unknown ifthis type of high-strength ceramic restoration requires adhesive cementation to enhance retention. Purpose. The purpose of this in vitro study was to determine the ability of selected luting agents to retain a representative zirconium oxide ceramic crown under clinically simulated conditions. Material and methods. Recently extracted human molars were prepared with a flat occlusal surface, 20degreetaper, and approximately 4-mm axial length. The axial and occlusal surface areas were determined, and specimens were distributed equally by total surface area into 3 cementation groups (n=12). Zirconium oxide ceramic copings (Procera AllZirkon) with an occlusal bar to facilitate removal were fabricated using computer-aided design/computer-assisted manufacturing (CAD/CAM) technology. All copingswere airborne-particle abraded with 50-mm Al2O3 and then cleaned in an ultrasonic bath with isopropyl alcohol. Provisional cement was removed from the prepared teeth, followed by a pumice prophy. After trial insertion, the copings were cleaned with phosphoric acid, rinsed, dried, and dehydrated with isopropyl alcohol. They were then cemented with a seating force of 10 kg per tooth, using either acomposite resin cement with adhesive agent (Panavia F 2.0 and ED Primer A & B [PAN]), a resin-modified glass ionomer cement (Rely X Luting [RXL]), or a self-adhesive modified composite resin (Rely X Unicem [RXU]). The cemented copings were thermal cycled at 5°C and 55°C for 5000 cycles with a 15 second dwell time, and then removed along the path of insertion using a universal testing machine at 0.5mm/min. The removal force was recorded, and the stress of dislodgement was calculated using the surface area of each preparation. A 1-way analysis of variance was used to analyze the data (a=.05). The nature of failure was also recorded. Results. Mean dislodgement stresses were 5.1, 6.1, and 5.0 MPa for PAN, RXL, and RXU, respectively. The 1-way analysis of variance revealed no differences in meancrown removal stress among the 3 cementation groups. The predominant mode of failure was cement remaining principally on the zirconium oxide copings in 46% of the specimens, followed by cement found on the tooth in 25.7% of the specimens. Conclusions. Within the limitations of this study, the 3 luting agents, with mean removal stresses ranging from 5.0 to 6.1 MPa were not significantly different.The use of a composite resin cement with a bonding agent did not yield higher coping retention compared to the other 2 cements tested. (J Prosthet Dent 2006;96:104-14.)

CLINICAL IMPLICATIONS
This in vitro study suggests that there is little difference among 3 different yet commonly used luting agents for retaining a representative zirconium oxide crown. All 3 are capable of retaining zirconiumoxide crowns successfully with no additional internal surface treatment other than airborne-particle abrasion with 50-mm aluminum oxide followed by appropriate cleaning of the crown prior to cementation.

T

he attractive properties of zirconium oxide ceramics such as high strength, excellent mechanical properties,1,2 and biocompatibility3 allow several

Presented in part at the 70th AnnualScientific Meeting of the Pacific Coast Society for Prosthodontics, June 2005, Marina del Rey, Calif. a Resident, Graduate Prosthodontics, Department of Restorative Dentistry; currently, Affiliate Instructor, Department of Restorative Dentistry. b Professor, Department of Restorative Dentistry. c Assistant Professor, Department of Restorative Dentistry. d Associate Professor and Director of Graduate...