Surface roughness and internal porosity of partial removable dental prosthesis frameworks fabricated from conventional wax and light-polymerized patterns: A comparative study Amal Ali Swelem, BDS, MS, PhD, a Mohamed Hussein Abdelnabi, BDS, MS, PhD, b Ayman A. Al-Dharrab, BDS, MS, PhD, c and Hanan Fouad AbdelMaguid, BDS, MS, PhD d King Abdulaziz University, Jeddah, Saudi Arabia; Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt; Faculty of Dentistry, Minia University, Minia, Egypt Statement of problem. 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. Purpose. 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. Material and 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 (mm), of the resultant castings was measured with a profilometer. Ra- diographs 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 (a¼.05). 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. (J Prosthet Dent 2014;111:335-341) Clinical Implications Newly introduced light-polymerized patterns produce partial removable dental prosthesis castings with a surface roughness and overall internal porosity comparable with those of conventional wax patterns and could be used to fabricate clinically acceptable frameworks. Poor fit and structural flaws in dental castings were found to be the 2 major factors that adversely affect the health of the remaining supporting structures. 1-3 Structural flaws may be external (as represented by surface roughness) or internal (presence of in- ternal voids and/or porosities), and both could be detrimental to the a Assistant Professor, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University; and Lecturer, Removable Prosthodontic Department, Faculty of Oral and Dental Medicine, Cairo University. b Associate Professor, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University, Removable Prosthodontic Department, Faculty of Dentistry, Minia University. c Assistant Professor, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University. d Assistant Professor, Oral and Basic Sciences Department, Faculty of Dentistry, King Abdulaziz University; and Lecturer, Radiology Department, Faculty of Oral and Dental Medicine, Cairo University. Swelem et al