title: An in vitro assessment of a ceramic-pressed-to-metal system as an alternative to conventional metal ceramic systems.
abstract: OBJECTIVE
  This article reviews a press-on metal (POM) ceramic versus a conventional veneering system regarding marginal gaps, fracture resistance, microhardness, and surface roughness. This was done to provide clinical recommendations for its use.
  
  
  METHODS
  Forty crowns were constructed and divided into two main groups according to the metal coping design. Group 1: Twenty metal copings with metal margin extending to the axiogingival line angle. Group 2: Twenty metal copings with metal margin 1 mm occlusal to the axiogingival line angle. The specimens of each group were further subdivided into two subgroups (A and B) according to the veneering porcelain used. The vertical marginal gaps of the crowns were measured after veneering placement. For fracture resistance testing, the crowns were subjected to compressive load to failure. Representative samples of the two main groups were selected to measure surface roughness and microhardness.
  
  
  RESULTS
  No statistically significant difference was evident regarding the vertical marginal gap distance in relation to the margin design of both tested groups (p= 0.249, p= 0.815); however, the POM veneer group with metal porcelain margin showed statistically lower marginal gaps than the conventional ceramic veneer group (p= 0.043). Fracture resistance values did not show statistically significant difference regarding the margin design (p= 0.858, p= 0.659) or type of the ceramic veneer material (p= 0.592, p= 0.165). Both groups showed no significant difference in their mean roughness values (p= 0.235). Conventional ceramics showed statistically significantly higher mean microhardness values than POM did (p= 0.008).
  
  
  CONCLUSIONS
  This study showed superior marginal adaptation, decreased microhardness, and similar load to failure and roughness values of the POM ceramic system. Moreover, considerable ease and speed of fabrication of this system were evident. The high variation in range values of some tested groups is among the limitations of this study, along with the lack of clinical trials to test the system in vivo.
authors.affiliation: Department of Fixed Prosthodontics, Faculty of Oral and Dental Medicine, Cairo, Egypt. nadiafahmyz@hotmail.com
authors.forename: Nadia Z
authors.initials: NZ
authors.lastname: Fahmy
authors.forename: Eman
authors.initials: E
authors.lastname: Salah
mesh_terms: D019245:Compressive Strength; D003442:Crowns; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006244:Hardness; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D011312:Pressure; D013499:Surface Properties
chemical_list: D016876:Metal Ceramic Alloys