IADR Abstract Archives
Effect of Thermocycling on Compressive Strength of Four Cements
Objectives: To compare 10,000 thermocycles’ effect on the compressive strength of four cements; Group 1: ACTIVA™ BioACTIVE-Cement™ (Pulpdent Corporation); Group 2: RelyX™ Unicem 2 Automix (3M); Group 3: FujiCEM™2 (GC America); and Group 4: Ceramir® Crown & Bridge (Doxa).
Methods: Eighty cylindrical samples (n=10), measuring 4mm by 8mm were prepared as follows: a glass plate was placed on the bottom of the mold followed by a Mylar® strip. Cement was extruded into the mold. A second Mylar film followed, which was covered by a second glass plate placed on top of the filled mold. Steady pressure was applied to the glass to displace any excess material. The cements were cured (DEMI™, Kerr) in accordance with manufacturers’ instructions and removed from the holder. Samples were wet-ground using 400-grit sandpaper (EcoMet™250, Buehler) to standardize dimensions and then stored in 37°C distilled water for 24 hours. Baseline samples were tested for compressive strength after 24 hours of storage. Samples were thermocycled for 10,000 cycles with a dwell time of 15 seconds between 5°C and 55°C to simulate aging. All compressive strength testing was measured using a universal testing machine (Instron®5566A) with 1K load cell and 1mm/min cross-head speed.
Results: Descriptive statistics were calculated for all groups’ compressive strengths. Kruskal-Wallis tests were used to compare the materials at baseline and after aging. Mann-Whitney U tests were used for post-hoc pairwise comparisons. P-values were corrected for multiple comparisons using the Bonferroni adjustment. There was statistical significance when comparing materials at baseline and after aging. For both baseline and aged samples, Group 1 was statistically significant from Groups 3 and 4 (Table 1 and 2). When comparing baseline to aged, statistically significant differences were between Groups 2 and 4 (Table 3).
Conclusions: Thermocycling had a significant negative effect on all groups except Groups 1 and 3.
Methods: Eighty cylindrical samples (n=10), measuring 4mm by 8mm were prepared as follows: a glass plate was placed on the bottom of the mold followed by a Mylar® strip. Cement was extruded into the mold. A second Mylar film followed, which was covered by a second glass plate placed on top of the filled mold. Steady pressure was applied to the glass to displace any excess material. The cements were cured (DEMI™, Kerr) in accordance with manufacturers’ instructions and removed from the holder. Samples were wet-ground using 400-grit sandpaper (EcoMet™250, Buehler) to standardize dimensions and then stored in 37°C distilled water for 24 hours. Baseline samples were tested for compressive strength after 24 hours of storage. Samples were thermocycled for 10,000 cycles with a dwell time of 15 seconds between 5°C and 55°C to simulate aging. All compressive strength testing was measured using a universal testing machine (Instron®5566A) with 1K load cell and 1mm/min cross-head speed.
Results: Descriptive statistics were calculated for all groups’ compressive strengths. Kruskal-Wallis tests were used to compare the materials at baseline and after aging. Mann-Whitney U tests were used for post-hoc pairwise comparisons. P-values were corrected for multiple comparisons using the Bonferroni adjustment. There was statistical significance when comparing materials at baseline and after aging. For both baseline and aged samples, Group 1 was statistically significant from Groups 3 and 4 (Table 1 and 2). When comparing baseline to aged, statistically significant differences were between Groups 2 and 4 (Table 3).
Conclusions: Thermocycling had a significant negative effect on all groups except Groups 1 and 3.
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