title: Fracture strength study of internally connected zirconia abutments reinforced with titanium inserts.
abstract: OBJECTIVE
  The implant-abutment connection area is known to be the weakest part of an internal-connection zirconia abutment and therefore the most likely to fracture. The aim of this study was to evaluate the complementary effect of a titanium insert on the fracture strength of a zirconia abutment.
  
  
  METHODS
  Three types of abutments with internal connection structures were selected and assembled: titanium abutment-titanium abutment screw (Ti-Ti), zirconia abutment-titanium abutment screw (Zr-Ti), and zirconia abutment-titanium insert-titanium abutment screw (Zr+Ti-Ti). Fifteen abutments and 15 implants were used and divided into three groups of five specimens each. Compressive loading was applied to the specimens at 30 degrees off-axis with dislocation speed of 1 mm/min and was increased until deformation occurred.
  
  
  RESULTS
  The Ti-Ti specimens showed the highest maximum fracture load, followed by the Zr+Ti-Ti specimens; the Zr-Ti assemblies were the weakest. Significant differences in fracture strength were found between the groups. All of the investigated Zr abutments fractured. However, in the Zr+Ti-Ti specimens, 60% of the Ti abutment screws fractured and 40% bent, whereas all of the abutment screws in the Zr-Ti group were only bent.
  
  
  CONCLUSIONS
  The Ti insert, as a substitute for the weakest part of a Zr abutment in an implant with an internal friction connection, can reinforce the fracture strength of a Zr abutment.
authors.forename: Hyo-Jung
authors.initials: HJ
authors.lastname: Chun
authors.forename: In-Sung
authors.initials: IS
authors.lastname: Yeo
authors.forename: Joo-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Seong-Kyun
authors.initials: SK
authors.lastname: Kim
authors.forename: Seong-Joo
authors.initials: SJ
authors.lastname: Heo
authors.forename: Jai-Young
authors.initials: JY
authors.lastname: Koak
authors.forename: Jung-Suk
authors.initials: JS
authors.lastname: Han
authors.forename: Shin-Jae
authors.initials: SJ
authors.lastname: Lee
mesh_terms: D000044:Dental Abutments; D059605:Dental Implant-Abutment Design / Q000379:methods*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D008422:Materials Testing; D014025:Titanium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide