title: A photoelastic and strain gauge comparison of two attachments for obturator prostheses.
abstract: BACKGROUND
  The rehabilitation of patients after a maxillectomy involves the use of an obturator to seal oral-nasal-sinus communication and to facilitate mastication, swallowing, and speech.
  
  
  OBJECTIVE
  The purpose of this in vitro study was to evaluate different attachment systems used for implant-retained obturators at dissipation loads and under shear forces.
  
  
  METHODS
  Photoelastic models were fabricated with 3 external hexagon implants at the incisor, canine, and first molar regions. Subsequently, overdentures were made, and metal hooks were placed at the incisor and first molar regions to displace the prostheses in the vertical, anterior, and posterior directions, with a constant speed of 50 mm/min. A photoelastic model with an O-ring or bar-clip system was placed in a circular polariscope, and tested with a universal testing machine. The images were recorded and high-intensity fringes were counted using software. For strain gauge analysis, each strain gauge was placed horizontally at the mesial and distal sides of the implants. The registered strains were submitted to 2-way ANOVA (α=.05).
  
  
  RESULTS
  The O-ring showed the lowest number of high-intensity fringes in photoelastic imaging, while the strain gauge analysis showed the lowest stress values in the bar-clip group (P=.007).
  
  
  CONCLUSIONS
  The stress around titanium implant necks was more damaging to surrounding bone, while the bar-clip attachment system had a better biomechanical performance. The bar-clip presented the lowest strain values around the dental implants and few high-intensity fringes.
authors.affiliation: Professor, Aracatuba Dental School, São Paulo State University (UNESP), São Paulo, Brazil. Electronic address: goiato@foa.unesp.br.
authors.forename: Marcelo Coelho
authors.initials: MC
authors.lastname: Goiato
authors.affiliation: Graduate student, Aracatuba Dental School, Sao Paulo State University (UNESP), São Paulo, Brazil.
authors.forename: Henrique Rinaldi
authors.initials: HR
authors.lastname: Matheus
authors.affiliation: Postgraduate student, Aracatuba Dental School, São Paulo State University (UNESP), São Paulo, Brazil.
authors.forename: Rodrigo Antonio
authors.initials: RA
authors.lastname: de Medeiros
authors.affiliation: Professor, Aracatuba Dental School, São Paulo State University (UNESP), São Paulo, Brazil.
authors.forename: Daniela Micheline
authors.initials: DM
authors.lastname: Dos Santos
authors.affiliation: Postgraduate student, Aracatuba Dental School, São Paulo State University (UNESP), São Paulo, Brazil.
authors.forename: Sandro Basso
authors.initials: SB
authors.lastname: Bitencourt
authors.affiliation: Professor, Aracatuba Dental School, São Paulo State University (UNESP), São Paulo, Brazil.
authors.forename: Aldiéris Alves
authors.initials: AA
authors.lastname: Pesqueira
mesh_terms: D017268:Dental Prosthesis Retention / Q000379:methods*; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods*; D003779:Denture Design; D003828:Denture, Overlay; D066298:In Vitro Techniques; D008422:Materials Testing; D003765:Models, Dental; D010158:Palatal Obturators; D013499:Surface Properties; D014025:Titanium
chemical_list: D014025:Titanium