title: Retrievability of implant-supported crowns when using three different cements: a controlled clinical trial.
abstract: OBJECTIVE
  The purpose of this study was to analyze the removal of implant-supported crowns retained by three different cements using an air-accelerated crown remover and to evaluate the patients' response to the procedure.
  
  
  METHODS
  This controlled clinical trial was conducted with 21 patients (10 women, 11 men; mean age: 51 ± 10.2 years) who had received a total of 74 implants (all placed in the posterior zone of the mandible). Four months after implant surgery, the crowns were cemented on standard titanium abutments of different heights. Three different cements (two temporary: Harvard TEMP and Improv; and one definitive: Durelon) were used and randomly assigned to the patients. Eight months later, one blinded investigator removed all crowns. The number of activations of the instrument (CORONAflex, KaVo) required for crown removal was recorded. The patients completed a questionnaire retrospectively to determine the impact of the procedure and to gauge their subjective perception. A linear regression model and descriptive statistics were used for data analysis.
  
  
  RESULTS
  All crowns could be retrieved without any technical complications or damage. Both abutment height (P = .019) and cement type (P = .004) had a significant effect on the number of activations, but the type of cement was more important. An increased total number of activations had no or only a weak correlation to the patients' perception of concussion, noise, pain, and unwillingness to use the device.
  
  
  CONCLUSIONS
  Cemented implant crowns can be removed, and the application of an air-accelerated device is a practicable method. A type of cement with appropriate retention force has to be selected. The impact on the patients' subjective perception should be taken into account.
authors.forename: Andreas
authors.initials: A
authors.lastname: Worni
authors.forename: Hadi
authors.initials: H
authors.lastname: Gholami
authors.forename: Laurent
authors.initials: L
authors.lastname: Marchand
authors.forename: Joannis
authors.initials: J
authors.lastname: Katsoulis
authors.forename: Regina
authors.initials: R
authors.lastname: Mericske-Stern
authors.forename: Norbert
authors.initials: N
authors.lastname: Enkling
mesh_terms: D001294:Attitude to Health; D002484:Cementation / Q000379:methods; D003442:Crowns; D003738:Dental Cements / Q000737:chemistry*; D017005:Dental Debonding / Q000295:instrumentation; D059605:Dental Implant-Abutment Design; D019250:Dental Implants, Single-Tooth; D003764:Dental Materials / Q000737:chemistry; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D020878:Device Removal / Q000295:instrumentation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects; D010147:Pain Measurement; D011076:Polycarboxylate Cement / Q000737:chemistry; D011312:Pressure; D012189:Retrospective Studies; D014025:Titanium / Q000737:chemistry; D015036:Zinc Phosphate Cement / Q000737:chemistry
chemical_list: D003738:Dental Cements; D003764:Dental Materials; C413303:ImProv; D011076:Polycarboxylate Cement; C031374:zinc polyacrylate; D015036:Zinc Phosphate Cement; C074226:Harvard Cement; D014025:Titanium