title: [The loss of interproximal contact between posterior fixed implant prostheses and adjacent teeth: a retrospective study].
abstract: OBJECTIVE
  To investigate the interproximal contact(IC) loss rate and the associated risk factors of IC loss between posterior fixed implant prostheses and the adjacent teeth.
  
  
  METHODS
  Ninety-seven posterior fixed implant prostheses including 165 IC in 78 patients(34 men, 44 women) between 23 and 76 years of age were investigated. The period after restoration ranged from 1 to 44 months. The IC between implant prostheses and adjacent teeth was evaluated using a 30-μm-thick contact gauge and dental floss, and the IC was regarded as lost when the gauge or dental floss was inserted into an IC without any resistance at follow-up visits. The state of IC, region of implant prostheses, the condition of opposing dentition, the vitality of the adjacent teeth and the time interval of tooth loss were also confirmed for correlation analysis.
  
  
  RESULTS
  All 78 patients finished follow-up examination. Forty-eight of 165 IC(29%) were regarded as lost. The IC loss rate at the mesial aspect[75%(36/48)] was significantly greater than that at the distal aspect[25%(12/48)](χ(2)=7.344,P=0.007). The difference between IC loss rate in the maxilla[46% (22/48)] and that in the mandible[54%(26/48)] was not significant(χ(2)=2.992,P=0.084). Free-end[hazard ratio (HR)=2.870], and the time interval of tooth loss(HR=0.919) affected the loss of IC significantly(P<0.05, Cox regression analysis).
  
  
  CONCLUSIONS
  Loss of IC between posterior fixed implant prostheses and adjacent teeth was one of biological complications, which was observed frequently at follow-up visits. Patients who have the free-end fixed implant prostheses, or undergo short time interval of tooth loss before restoration may have high risk of the IC loss.
authors.affiliation: Department of Prosthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China (Present address of Luo Q: Department of Operative Dentistry and Endodontics, General Hospital of Chinese PLA, Beijing 100853, China).
authors.forename: Q
authors.initials: Q
authors.lastname: Luo
authors.forename: Q
authors.initials: Q
authors.lastname: Ding
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: D
authors.initials: D
authors.lastname: Peng
authors.forename: Q F
authors.initials: QF
authors.lastname: Xie
mesh_terms: D000328:Adult; D000368:Aged; D015921:Dental Implants; D019232:Dental Restoration Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008334:Mandible; D008437:Maxilla; D008875:Middle Aged; D014070:Tooth; D016388:Tooth Loss / Q000209:etiology*
chemical_list: D015921:Dental Implants