title: The Effect of Cyclic Loading on the Compressive Strength of Core Build-Up Materials.
abstract: OBJECTIVE
  To evaluate the effect of cyclic loading on compressive strength of core build-up materials.
  
  
  METHODS
  Four dual-cured composites (Core.X Flow, Grandio Core, Bright Flow Core, Spee-Dee) and one light-cured reinforced resin-modified glass ionomer (Fuji II LC) were tested. One hundred cylindrical specimens (4 mm × 6 mm) were prepared. Each material had two groups (ten specimens to be tested under static loading and ten specimens to be tested after cyclic loading). The specimens were stored wet, and after 30 days, one group of each material was cyclically loaded (for 250,000 cycles with a frequency of 1.6 Hz under stress load of 68.6 N) in a chewing simulator CS-4.2. Then specimens were subjected to static compressive loading until failure in a universal testing machine.
  
  
  RESULTS
  Mean compressive strength values before cycling ranged from 144 MPa (15.8) for Fuji II LC to 277 MPa (23.2) for Grandio Core. Independent t-test showed no statistically significant difference (p > 0.05) in the compressive strength of each material before and after cycling (p = 0.7 Grandio Core, p = 0.3 Core.X Flow, p = 0.6 Bright Flow Core, p = 0.2 Spee-Dee, p = 0.6 Fuji II LC); however, there was a statistically significant difference between the materials when comparing before and after cycling.
  
  
  CONCLUSIONS
  All tested materials showed no reduction in the compressive strength after cycling. Therefore, the tested materials can survive 1 year in service without a reduction in compressive strength.
authors.affiliation: School of Dentistry, University of Manchester, Manchester, UK.|University of Tripoli for Medical Sciences, Faculty of Dentistry and Oral Surgery, Tripoli, Libya.
authors.forename: Muayed A
authors.initials: MA
authors.lastname: Zankuli
authors.affiliation: School of Dentistry, University of Manchester, Manchester, UK.
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.affiliation: School of Dentistry, University of Manchester, Manchester, UK.
authors.forename: Hugh
authors.initials: H
authors.lastname: Devlin
keywords: Core build-up materials; cyclic loading; mechanical properties