title: Clinical evaluation of an improved cementation technique for implant-supported restorations: a randomized controlled trial.
abstract: BACKGROUND
  Cement remnants were frequently associated with peri-implantitis. Recently, a shoulderless abutment was proposed, raising some concern about cement excess removal.
  
  
  OBJECTIVE
  To compare different cementation techniques for implant-supported restorations assessing the amount of cement remnants in the peri-implant sulcus. Additional aim was to compare the effect of these cementation techniques using two different abutment designs.
  
  
  METHODS
  Forty-six patients requiring double implant-supported restoration in the posterior maxilla were randomly divided in two groups according to the cementation modality: intraoral and extraoral. According to the abutment finishing line, implants in each patient were randomly assigned to shoulderless or chamfer subgroup. In the intraoral group, crowns were directly seated onto the titanium abutment. In the extraoral group, crowns were firstly seated onto a resin abutment replica and immediately removed, then cleansed of the cement excess and finally seated on the titanium abutment. After cement setting, in both groups, cement excess was carefully tried to remove. Three months later, framework/abutment complexes were disconnected and prepared for microscopic analysis: surface occupied by exposed cement remnants and marginal gaps were measured. Additionally, crown/abutment complexes were grinded, and voids of cement were measured at abutment/crown interface. Related-samples Friedman's two-way analysis of variance by ranks was used to detect differences between groups and subgroups (P ≤ 0.5).
  
  
  RESULTS
  At the end of the study, a mean value of 0.45 mm2(±0.80), 0.38 mm2(±0.84), and 0.065 mm2(±0.13) and 0.07 mm2(±0.15) described surface occupied by cement remnants in shoulderless and chamfer abutment with intraoral cementation and shoulderless and chamfer abutment with extraoral cementation, respectively. A mean value of 0.40 mm2(±0.377), 0.41 mm2(±0.39) and 0.485 mm2(±0.47) and 0.477 mm2(±0.43) described cement voids at the abutment/crown interface; a mean value of 0.062 mm (±0.03), 0.064 mm (±0.35), 0.055 mm (±0.016) and 0.054 mm (±0.024) described marginal gaps. Statistics showed tendency of intraoral cementation to have significantly higher cement remnants compared with abutments with extraoral cementation groups. At the same time, the presence of voids was significantly higher in case of extraoral cementation. No significant differences between groups for the variable "gap".
  
  
  CONCLUSIONS
  Despite the presence of more voids, extraoral cementation reduces cement excess. However, using low adhesivity cement and careful cement removal, a very limited quantity of cement remnants was observed also in the intraoral cementation.
authors.affiliation: Private Practice and Independent Researcher, Rome, Italy.|Department of Oral Surgery and Implantology, Valencia University Medical and Dental School, Valencia, Spain.
authors.forename: Luigi
authors.initials: L
authors.lastname: Canullo
authors.affiliation: Private Practice, Verona, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cocchetto
authors.affiliation: Laboratory Technician, Rome, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Marinotti
authors.affiliation: Department of Oral Surgery, Valencia University Medical and Dental School, Valencia, Spain.
authors.forename: David Peñarrocha
authors.initials: DP
authors.lastname: Oltra
authors.affiliation: Department of Oral Surgery, Valencia University Medical and Dental School, Valencia, Spain.
authors.forename: María Peñarrocha
authors.initials: MP
authors.lastname: Diago
authors.affiliation: Private Practice, Cagliari, Italy.
authors.forename: Ignazio
authors.initials: I
authors.lastname: Loi
mesh_terms: D002484:Cementation / Q000379:methods*; D003738:Dental Cements; D059605:Dental Implant-Abutment Design; D019094:Dental Prosthesis, Implant-Supported / Q000379:methods*; D006801:Humans; D011446:Prospective Studies; D016896:Treatment Outcome
chemical_list: D003738:Dental Cements
keywords: abutment design; cement remnants; chamfer; feather-edge abutment; peri-implantitis; shoulderless abutment