title: Resistance to dislodgement of zirconia copings cemented onto titanium abutments of different heights.
abstract: BACKGROUND
  For patients with limited interocclusal space, standard height implant abutments may not be usable. Shorter abutments may be desirable.
  
  
  OBJECTIVE
  The purpose of this study was to determine the effect of the height of titanium abutments on the tensile strength required to dislodge zirconia copings.
  
  
  METHODS
  Two experimental groups of abutments were prepared: (1) 4.3-mm platform width implant abutment with a 6.5-mm height (control), and (2) a 4.3-mm platform width implant abutment with a 5.5-mm height (shorter). Each abutment had 5 zirconia copings (custom designed) fabricated through a 3-dimensional computer-assisted design (3-D CAD) process by scanning an identical wax pattern. The zirconia copings were designed to have a 6-mm projection above the titanium abutment to accommodate a 2-mm hole. A wire was inserted through this hole to attach the zirconia coping to a universal testing machine. Each abutment was placed onto an implant embedded in a brass base designed to fit onto the universal testing machine. The zirconia copings were cemented onto the abutments with a provisional luting agent (Improv), and a tensile force was applied at a crosshead speed of 0.5 mm/min. The removal force was recorded for each specimen. An unpaired t test was used for the statistical analysis (alpha =.05).
  
  
  RESULTS
  The mean force (SD) necessary to remove the zirconia copings (Newtons) from the 6.5-mm titanium abutment (198.09 (28.83)) was higher (P=.0078) than for the 5.5-mm abutment (124.89 (36.388)).
  
  
  CONCLUSIONS
  By increasing the height of the abutment 1 mm and maintaining the diameter of the abutment, the resistance to tensile forces increased significantly between the 2 abutment dimensions evaluated.
authors.affiliation: Biologic and Materials Sciences, Division of Prosthodontics, University of Michigan, School of Dentistry, Ann Arbor, MI 48103, USA. abbovan@umich.edu
authors.forename: Bill
authors.initials: B
authors.lastname: Abbo
authors.forename: Michael E
authors.initials: ME
authors.lastname: Razzoog
authors.forename: Jose
authors.initials: J
authors.lastname: Vivas
authors.forename: Marianella
authors.initials: M
authors.lastname: Sierraalta
mesh_terms: D000044:Dental Abutments; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design / Q000379:methods*; D017268:Dental Prosthesis Retention / Q000379:methods*; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide