title: Dimensional tolerances and assembly accuracy of dental implants and machined versus cast-on abutments.
abstract: BACKGROUND
  The clinical application of prosthetic components obtained by different manufacturing processes lacks technological foundation: the dimensional tolerance of individual parts and their assembly accuracy are not known. The rotational misfit (RM) of the hexagonal connection is critical in single-tooth implant restorations, but no standard control procedures are available for its evaluation.
  
  
  OBJECTIVE
  The research aimed at proposing a new protocol for the dimensional assessment of implant-abutment connections, based on noncontact measurement and statistical data processing. The procedure was applied to machined- and cast-on abutments, as well of the matching implants.
  
  
  METHODS
  Three groups of five abutments each were studied: machined titanium abutments, pre-machined calcinable abutments before casting procedures and the same specimens after casting. A group of five corresponding implants was considered as well. Twice the apothem was measured on each hexagon through an optical measuring microscope. The data were processed to obtain the international tolerance (IT) grade. The RM was then calculated using the apothems of the external and the internal hexagon.
  
  
  RESULTS
  All the components were classified between IT8 and IT9, and the maximum RM was around 3-4° for all the assemblies, inferior to the critical limits for the screw joint stability.
  
  
  CONCLUSIONS
  An original measuring protocol was developed, independent of parts assembly and based on ITs. An objective dimensional characterization of prosthetic components and assemblies has been achieved, which is the basis for their reliability in clinical applications.
authors.affiliation: Department of Specialist Surgeries Head-Neck, Modena and Reggio Emilia University, Modena, Italy.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Malaguti
authors.forename: Lucia
authors.initials: L
authors.lastname: Denti
authors.forename: Elena
authors.initials: E
authors.lastname: Bassoli
authors.forename: Irene
authors.initials: I
authors.lastname: Franchi
authors.forename: Sergio
authors.initials: S
authors.lastname: Bortolini
authors.forename: Andrea
authors.initials: A
authors.lastname: Gatto
mesh_terms: D000465:Algorithms; D003300:Copper / Q000737:chemistry; D000044:Dental Abutments; D003735:Dental Casting Technique; D015921:Dental Implants; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D017267:Dental Prosthesis Design; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D016876:Metal Ceramic Alloys / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D013499:Surface Properties; D013674:Technology, Dental; D014025:Titanium / Q000737:chemistry
chemical_list: D015921:Dental Implants; D003764:Dental Materials; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D012834:Silver; D010984:Platinum; D010165:Palladium; D003300:Copper; D014025:Titanium