title: Clinical use of alumina-toughened zirconia abutments for implant-supported restoration: prospective cohort study of survival analysis.
abstract: OBJECTIVE
  The aim of this prospective cohort study was to compute the long-term clinical survival and complication rates of alumina-toughened zirconia abutments used for implant-supported restorations and to evaluate the effects of several clinical variables on these rates.
  
  
  METHODS
  From May 1998 to September 2010, 213 patients aged 18 years or older were recruited. The patients received 611 external hex implants and 328 implant-supported fixed restorations using alumina-toughened zirconia abutments. During the follow-up, each restoration was coded as a dental event, which included loosening or fracture of abutment screws, and abutment fracture. From the coded data, the effects of the investigated clinical variables-restored area (anterior/posterior), number of prosthodontic units (one/two units or over), prosthesis type (single-unit/multiunit without pontic/multiunit with pontic), implant system, and patient gender-on the survival of the abutments were evaluated. Survival analysis using Kaplan-Meier method and Cox proportional hazard model was applied. The 5-year survival and complication rates of the abutments were assessed.
  
  
  RESULTS
  The number of prosthodontic units and the type of prosthesis had a significant association with complication rates (P < 0.05). Kaplan-Meier survival analysis estimated that the cumulative 5-year complication rate of the abutments used in single restorations was 19.7%. Multiunit-fixed dental prostheses without and with pontics had complication rates of 3.9% and 3.8%, respectively. The 5-year survival rate of the abutments was more than 95%, regardless of the type of prosthesis.
  
  
  CONCLUSIONS
  Alumina-toughened zirconia abutments are likely to exhibit excellent long-term survival in clinical use for fixed restorations. Single tooth replacement with the abutment at the molar region may require special care and extra attention.
authors.affiliation: School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Seung-Soo
authors.initials: SS
authors.lastname: Kim
authors.forename: In-Sung
authors.initials: IS
authors.lastname: Yeo
authors.forename: Shin-Jae
authors.initials: SJ
authors.lastname: Lee
authors.forename: Dae-Joon
authors.initials: DJ
authors.lastname: Kim
authors.forename: Brian Myeongwoo
authors.initials: BM
authors.lastname: Jang
authors.forename: Soo-Hwan
authors.initials: SH
authors.lastname: Kim
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Han
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000537:Aluminum Oxide / Q000737:chemistry*; D000044:Dental Abutments; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011446:Prospective Studies; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015040:Zirconium; D000537:Aluminum Oxide; C028541:zirconium oxide