Nguy, Tom Hai-Tam.2012-12-052012-12-052012-09https://hdl.handle.net/11299/140127University of Minnesota M.S. thesis. September 2012. Major: Dentistry. Advisor: Scott B. McClanahan. 1 computer file (PDF); v, 41 pages.The purpose of this study was to investigate the effects of taper sizes on fracture resistance in root sections and determine if there is a difference in the fracture resistance of different regions within the same root. Thirty-six single-rooted mandibular premolars were divided into three groups for three different taper sizes (.02, .04, and .06). The specimens were instrumented and sectioned. Each section was photographed and the net average surface area was calculated using the ImageJ software (NIH, Bethesda, MD). Each individual root section was then subjected to a load to fracture test using the MTS 858 machine (MTS, Eden Praire, MN). A ratio of the load to fracture and average surface area was calculated. Statistical analysis was conducted using ANOVA, Tukey-Kramer, Pairwise Spearman, and Random Intercept Models. It was determined that fracture resistance increase with larger taper size and was higher in the apical region.en-USDentistryThesis or Dissertation