title: An analysis of the effect of a vent hole on excess cement expressed at the crown-abutment margin for cement-retained implant crowns.
abstract: OBJECTIVE
  The labial margins of anterior implant-retained crowns are often positioned subgingivally for a superior esthetic appearance. One of the consequences of subgingival margins is the increased risk of leaving excess cement behind following cementation. This can lead to potential problems, including peri-implant inflammation, soft tissue swelling, soreness, bleeding or suppuration on probing, and bone loss. The purpose of this laboratory study was to investigate the effect of placement, location, and diameter of a vent hole on the amount of cement being expressed at the margin of an anterior implant abutment-retained crown.
  
  
  METHODS
  Three implant crown copings were fabricated to fit on the same custom abutment. Three vent diameters (0.75, 1.25, and 1.65 mm) and three locations on the palatal surface of the coping (cervico-palatally, mid-palatally, inciso-palatally) were chosen for vent hole placement. For each test, the coping was cemented onto the abutment under standardized conditions. A preweighed thin coating of cement was applied to the fit surface of the coping. The amount of cement expressed at the margin and vent hole was measured by weight and calculated as a proportion of the amount of cement placed in the coping before seating. The procedure was completed 15 times for each variable. The results were statistically analyzed using univariate ANOVA with post hoc Bonferroni-adjusted independent samples t-tests.
  
  
  RESULTS
  The presence of a vent hole influenced the proportion of cement expressed at the coping margin (p < 0.05). The location of a vent hole influenced the proportion of cement expressed at the coping margin (p < 0.05), with the exception of the mid-palatal and inciso-palatal positioning where there was no significant difference (p= 0.61) between groups. The diameter of the vent hole did not significantly influence the proportion of cement expressed at the coping margin (p= 0.096).
  
  
  CONCLUSIONS
  When using anterior cement-retained implant crowns, the use of a 0.75-mm mid-palatal or inciso-palatal vent hole to minimize the amount of cement expressed at the margin during cementation should be considered.
authors.affiliation: Unit of Prosthodontics, UCL Eastman Dental Institute, University College London, London, UK.
authors.forename: Dipan
authors.initials: D
authors.lastname: Patel
authors.forename: James C F
authors.initials: JC
authors.lastname: Invest
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Tredwin
authors.forename: Derrick J
authors.initials: DJ
authors.lastname: Setchell
authors.forename: David R
authors.initials: DR
authors.lastname: Moles
mesh_terms: D002484:Cementation / Q000009:adverse effects*; D003442:Crowns; D000044:Dental Abutments; D003735:Dental Casting Technique / Q000295:instrumentation*; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D005882:Gingival Diseases / Q000209:etiology / Q000517:prevention & control; D019231:Tooth Preparation, Prosthodontic