243 SENB Fracture Toughness of Resin Composites after Storage in Water

Thursday, March 22, 2012: 2 p.m. - 3:15 p.m.
Presentation Type: Poster Session
S.S. KHAJOTIA1, L.E. YEARY1, and M.W. KELLER2, 1Department of Dental Materials, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 2Department of Mechanical Engineering, University of Tulsa, Tulsa, OK
Objectives: To determine the effect of storage in water at oral temperature for seven days on SENB fracture toughness of selected resin-composites using ASTM Standard D5045-99 (2007).  Methods: Seven SENB specimens each of resin-composites Esthet-X HD (EX; Dentsply/Caulk), 4-Seasons (FS; Ivoclar-Vivadent), Gradia Direct (GR; GC), Point 4 (PF; Kerr), and TPH3 (TP; Dentsply/Caulk) were fabricated in a custom-made metal mold (17.6x2.0x4.0mm; blade length approximately 2mm) to produce specimens having dimensions as per the ASTM Standard. Specimens were polymerized in 2mm increments (40-second light-activation/increment). Dimensions were measured with an electronic caliper at three equally-spaced positions and averaged to determine width (W), length (L), and thickness (B).  Crack-length (a) and crack-width (N) were measured using a stereomicroscope and digital camera both before and after fracture.  Specimens were stored in a water bath at 37±1°C for 1-day (control group) or 7-days (experimental group), and then fractured in three-point bending in air (33R4468 Instron universal testing machine; crosshead rate: 0.5mm/min, support span: 16mm). KIC fracture toughness values were calculated and validated as described in ASTM Standard D-5045-99(2007).  Mean KIC values in each group were compared using one-factor ANOVA and post hoc Student-Newman-Keuls tests (SNK; α=0.05).  A t-test was used to compare mean values of each product after storage for 1- and 7-days (α=0.05).  Results: Mean±StdDev KIC values (MPa·m1/2) were:


Storage duration


















Letters denote mean values in each row that are statistically different from each other (p<0.05)
* denotes mean values in each column that are statistically different from each other (p<0.05)

Conclusions: Mean KIC values of the resin-composites tested were not statistically different after storage in water at oral temperature for 1-day versus 7-days except for product FS, where a decrease in fracture toughness was observed. Mean KIC values of the resin-composites tested differed statistically within each test group. Funding: J. Dean Robertson Society, University of Oklahoma.

This abstract is based on research that was funded entirely or partially by an outside source: J. Dean Robertson Society, University of Oklahoma

Keywords: Composites, Dental materials, Fracture toughness and Physical
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