title: Evaluation of single-tooth implants in the second molar region: a 5-year life-table analysis of a retrospective study.
abstract: BACKGROUND
  To our knowledge, no study has evaluated the success or survival rate of single-tooth implants that replaced missing maxillary and mandibular second molars. The purpose of the present study was to evaluate the 1- to 5-year cumulative survival rate (CSR) for single-tooth implants placed in the second molar region and the effects of associated factors.
  
  
  METHODS
  Four hundred eighty-nine patients (298 males and 191 females; age range: 23 to 91 years; mean age: 47 years) who were admitted to the Seoul National University Dental Hospital between March 2003 and July 2008 and treated with single-tooth implants in the second molar region (227 maxillary implants and 294 mandibular implants; total: 521 implants) were included in the study. Thirty-two subjects received two implants each. A 1- to 5-year CSR was calculated using a life-table analysis. A comparison of CSRs between maxillary versus mandibular implants, one-stage versus two-stage implants, short (<or=8.5 mm) versus long (>10 mm) implants, and standard-diameter (<or=4.0 mm) versus wide-diameter (>or=5.0 mm) implants was performed using Wilcoxon (Gehan) statistics. P <0.05 was considered significant.
  
  
  RESULTS
  Fifteen of the 521 implants were lost between insertion and the follow-up examinations. The 1- to 5-year CSR was 95.1%. There were no statistically significant differences in CSRs between implants placed in maxillas and mandibles (96.3% versus 94.9%, respectively; P = 0.084), one- and two-stage implants (95.6% versus 94.7%, respectively; P = 0.267), short and long implants (100% versus 95.1%, respectively; P = 0.582), and standard- and wide-diameter implants (93.8% versus 96.8%, respectively; P = 0.065).
  
  
  CONCLUSIONS
  Within the limitations of the study, the placement of single-tooth implants in the second molar region was an effective and reliable treatment modality. Also, associated factors such as implant diameter, length, and location (the maxilla versus the mandible) may not have an impact on the long-term success of implants.
authors.affiliation: Department of Periodontology, School of Dentistry, and Dental Research Institute, Seoul National University, Seoul, Korea.
authors.forename: Ki-Tae
authors.initials: KT
authors.lastname: Koo
authors.forename: Ulf M E
authors.initials: UM
authors.lastname: Wikesjö
authors.forename: Jang-Yeol
authors.initials: JY
authors.lastname: Park
authors.forename: Tae-Il
authors.initials: TI
authors.lastname: Kim
authors.forename: Yang-Jo
authors.initials: YJ
authors.lastname: Seol
authors.forename: Young
authors.initials: Y
authors.lastname: Ku
authors.forename: In-Chul
authors.initials: IC
authors.lastname: Rhyu
authors.forename: Chong-Pyoung
authors.initials: CP
authors.lastname: Chung
authors.forename: Yong-Moo
authors.initials: YM
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003758:Dental Implantation, Endosseous / Q000379:methods*; D019250:Dental Implants, Single-Tooth; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D005260:Female; D006801:Humans; D015993:Life Tables; D008297:Male; D008875:Middle Aged; D008963:Molar; D012189:Retrospective Studies; D016896:Treatment Outcome; D055815:Young Adult