title: Clinical evaluation of the incidence of prosthetic complications in implant crowns constructed with UCLA castable abutments. A cohort follow-up study.
abstract: OBJECTIVE
  To evaluate the incidence of prosthetic complications in implant-retained crowns made with UCLA castable abutments and to identify possible risk factors with a view to establishing recommendations to help predict the success of such restorations.
  
  
  METHODS
  A cohort follow-up study was carried out in 71 partially dentate patients rehabilitated with 93 implant-retained single crowns. Data regarding socio-demographic background, anatomical features, implant-, and prosthesis-related variables were recorded. The incidence rate (%), relative risk (RR) and odds ratio (OR) were applied for predictive risk factors. ANOVA and Student t-tests were used to compare quantitative variables, the chi-square test was used to compare proportions and also a logistic regression analysis was performed. The statistical significance was set at α = 0.05.
  
  
  RESULTS
  Two implants (2.2%) were lost during the first year of function. The incidence of prosthetic complications in the observed mean period (26.2 ± 15.4 months) was 11.9%, consisting of screw loosening (10.8%) and ceramic fracture (1.1%). A higher tendency for prosthetic complications was noticed in posterior mandibular crowns restoring saddles longer than 10 mm with mesiodistal cantilevers longer than 6mm, having natural antagonists, after long-term use (>20 months), with initial torque values superior than 30 Ncm.
  
  
  CONCLUSIONS
  Screw loosening is the most frequent complication in implant-retained crowns fabricated with UCLA abutments cast in cobalt-chromium. Nevertheless, the connection usually remains stable after retightening the screws. A high survival rate was recorded, and these prostheses may be a suitable treatment option.
  
  
  CONCLUSIONS
  Based on the study findings, the risk of prosthetic complications is expected to increase when long-span posterior edentulous areas are rehabilitated with single implant-supported crowns. The antagonist occlusal plane should be restored to prevent torsional forces and overloading. Implant systems with initial torque values less than 30 Ncm should be selected.
authors.affiliation: Prosthodontics, Department of Surgery, Faculty of Medicine, University of Salamanca (USAL), C/Alfonso X el Sabio, s/n, Campus de Unamuno, E-37007 Salamanca, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Montero
authors.forename: Guillermo
authors.initials: G
authors.lastname: Manzano
authors.forename: David
authors.initials: D
authors.lastname: Beltrán
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Lynch
authors.forename: María-Jesús
authors.initials: MJ
authors.lastname: Suárez-García
authors.forename: Raquel
authors.initials: R
authors.lastname: Castillo-Oyagüe
mesh_terms: D000328:Adult; D000368:Aged; D002484:Cementation / Q000379:methods; D002858:Chromium Alloys / Q000737:chemistry; D015331:Cohort Studies; D003442:Crowns; D003735:Dental Casting Technique; D059605:Dental Implant-Abutment Design; D019250:Dental Implants, Single-Tooth; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007576:Jaw, Edentulous, Partially / Q000534:rehabilitation; D008297:Male; D016876:Metal Ceramic Alloys / Q000737:chemistry; D008875:Middle Aged; D016348:Osseointegration / Q000502:physiology; D012307:Risk Factors; D012907:Smoking; D016019:Survival Analysis; D019415:Torque; D054159:Torsion, Mechanical; D016896:Treatment Outcome
chemical_list: D002858:Chromium Alloys; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain