title: An In Vitro Evaluation of the Loosening of Different Interchangeable Abutments in Internal-Connection-Type Implants.
abstract: OBJECTIVE
  The aim of this study was to compare the loosening of interchangeable one-piece abutments connected to internal-connection-type implants after cyclic loading.
  
  
  METHODS
  Four implant abutment groups (n = 7 in each group) with Straumann tissue-level implants were assessed: Straumann solid abutment (group S), Southern Implants solid abutment (group SI), Implant Direct straight abutment (group ID), and Blue Sky Bio regular platform abutment (group BSB). The implant was firmly held in a special jig to ensure fixation. Abutment screws were tightened to manufacturers' recommended torque with a digital torque gauge. The hemispherical loading members were fabricated for the load cell of a universal testing machine to evenly distribute the force on the specimens and to fulfill the ISO 14801:2007 standard. A cyclic loading of 25 N at 30 degrees to the implant's long axis was applied for a duty of a half million cycles. Tightening torques were measured prior to the loading. Removal torques were measured after cyclic loading. The data were analyzed with one-way analysis of variance (ANOVA), and the significance level was set at P < .05.
  
  
  RESULTS
  The mean removal torques after cyclic loading were 34.0 ± 1.1 Ncm (group S), 25.0 ± 1.5 Ncm (group SI), 23.9 ± 2.1 Ncm (group ID), and 27.9 ± 1.3 Ncm (group BSB). Removal torques of each group were statistically different in the order of group S > group BSB > groups SI and ID (P < .05). The mean reduction rates were -2.9% ± 3.2% (group S), -21.9% ± 4.8% (group SI), -20.2% ± 7.2% (group ID), and -6.9% ± 4.3% (group BSB) after a half million cycles, respectively. Reduction rates of groups S and BSB were statistically lower than those of groups SI and ID (P < .01). The standard deviation of group S was lower than group BSB.
  
  
  CONCLUSIONS
  The removal torque of the original Straumann abutment was significantly higher than those of the copy abutments. The reduction rate of the groups S and BSB abutments was lower than those of the other copy abutments.
authors.forename: Ji-Man
authors.initials: JM
authors.lastname: Park
authors.forename: Chang-Hyun
authors.initials: CH
authors.lastname: Baek
authors.forename: Seong-Joo
authors.initials: SJ
authors.lastname: Heo
authors.forename: Seong-Kyun
authors.initials: SK
authors.lastname: Kim
authors.forename: Jai-Young
authors.initials: JY
authors.lastname: Koak
authors.forename: Shin-Koo
authors.initials: SK
authors.lastname: Kim
authors.forename: Urs C
authors.initials: UC
authors.lastname: Belser
mesh_terms: D000704:Analysis of Variance; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design / Q000592:standards*; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation / Q000592:standards*; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D019415:Torque
chemical_list: D015921:Dental Implants