title: Surface roughness and internal porosity of partial removable dental prosthesis frameworks fabricated from conventional wax and light-polymerized patterns: a comparative study.
abstract: BACKGROUND
  Surface roughness and internal porosity are 2 potential risk factors that threaten the biocompatibility and long-term mechanical stability of cast partial removable dental prostheses frameworks.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the influence of the material, of conventional wax patterns, and the recently introduced light-polymerized patterns on the initial surface roughness and internal porosity of the cobalt-chromium castings of partial removable dental prostheses.
  
  
  METHODS
  Twenty-eight identical partial removable dental prosthesis frameworks were fabricated on a cast of a maxillary Kennedy Class III modification 1 partially edentulous patient. Fourteen frameworks were fabricated from each pattern material. The initial surface roughness, Ra (μm), of the resultant castings was measured with a profilometer. Radiographs of the castings were made on dental occlusal films with a dental x-ray unit with the following exposure conditions: tube voltage 70 kV; exposure time 1.0 seconds; tube current 7 mA; and source-film distance 35 cm. The number and size of porosities in the 3 main components (clasp units, major connectors, denture base meshwork) were assessed. Statistical analysis was conducted with the independent sample t test for surface roughness and the Mann Whitney test for internal porosity (α=.05).
  
  
  RESULTS
  The statistical analysis of mean surface roughness and internal porosity revealed no significant difference between the 2 groups.
  
  
  CONCLUSIONS
  The surface roughness and internal porosity of frameworks fabricated from conventional wax and Liwa patterns were comparable, with no significant differences between the 2 pattern materials.
authors.affiliation: Assistant Professor, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia; and Lecturer, Removable Prosthodontic Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. Electronic address: amalswelem@hotmail.com.
authors.forename: Amal Ali
authors.initials: AA
authors.lastname: Swelem
authors.affiliation: Associate Professor, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University, Removable Prosthodontic Department, Faculty of Dentistry, Minia University, Minia, Egypt.
authors.forename: Mohamed Hussein
authors.initials: MH
authors.lastname: Abdelnabi
authors.affiliation: Assistant Professor, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Ayman A
authors.initials: AA
authors.lastname: Al-Dharrab
authors.affiliation: Assistant Professor, Oral and Basic Sciences Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia; and Lecturer, Radiology Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
authors.forename: Hanan Fouad
authors.initials: HF
authors.lastname: AbdelMaguid
mesh_terms: D000179:Acrylates / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique; D016734:Dental Clasps; D003764:Dental Materials / Q000737:chemistry*; D003819:Denture Bases; D003832:Denture, Partial, Removable; D006801:Humans; D008422:Materials Testing; D058105:Polymerization; D016062:Porosity; D011861:Radiography, Dental; D013314:Stress, Mechanical; D013499:Surface Properties; D014885:Waxes / Q000737:chemistry*
chemical_list: D000179:Acrylates; D001672:Biocompatible Materials; D002858:Chromium Alloys; D003734:Dental Casting Investment; D003764:Dental Materials; D014885:Waxes