IADR Abstract Archives
Does Camphorquinone Enantiomers Matter in Mechanical Properties of Resin Composites?
Objectives: Camphorquinone (CQ) is commonly used as excitation and activation for dimethacrylate-based resins. Chemically, CQ per se has two enantiomers in R- and S-forms, namely R-CQ and S-CQ. However, such a enantiomeric property of CQ has been ignored and never been discussed in dentistry. This seminal study was to study whether the CQ enantiomers would affect the mechanical properties in dental resins.
Methods: The resin was prepared by hand-mixing 70.0wt-% Urethane dimethacrylate (UEMA), 28.0wt-% Hydroxypropyl methylacrylate (HPMA) and 1.0wt-% N,N-dimethyl-p-toluidine (NPT) with respect to 1.0wt-% of RS-CQ (i.e. nominal CQ as control), S-CQ or R-CQ. After the resins preparation, they were moulded and light-cured for 20s in disk (Φ6.8×1.3mm, N=36) , cylindrical (Φ3.0×6.0mm, N=63) and one rectangular (25.0×2.0×2.0mm, N=63) forms for indentation, compressive and three-point bending tests to calculate the Vickers Hardness, Compressive Yield Point and Strain Energy. Before the test, 24 disk, 42 cylindrical and 42 rectangular specimens were separately stored 37oC water for 7 and 14 days, whilst remaining was tested immediately. One-way ANOVA and paired t-tests were used to statistically analyze the data at α=0.05.
Results: One-way ANOVA revealed that Vickers Hardness (p~4.60×10-41), Compressive Yield Point (p~3.65×10-8) and Strain Energy (p~1.80×10-27) are significantly different between groups. Paired t-tests showed the R-CQ could significantly improve the Hardness and Strain Energy (p<0.05) after 14 days water storage. After the 14 days water storage all R-CQ loaded resin achieve significantly (p<0.05) highest Hardness (4.94±0.61Hv), Strain Energy (15.42±1.40mJ) and Compressive Yield Point (19.83±2.86MPa) values among all other CQs.
Conclusions: R-CQ deemed to be a better activator for dental resins that could achieve a better mechanical properties.
Methods: The resin was prepared by hand-mixing 70.0wt-% Urethane dimethacrylate (UEMA), 28.0wt-% Hydroxypropyl methylacrylate (HPMA) and 1.0wt-% N,N-dimethyl-p-toluidine (NPT) with respect to 1.0wt-% of RS-CQ (i.e. nominal CQ as control), S-CQ or R-CQ. After the resins preparation, they were moulded and light-cured for 20s in disk (Φ6.8×1.3mm, N=36) , cylindrical (Φ3.0×6.0mm, N=63) and one rectangular (25.0×2.0×2.0mm, N=63) forms for indentation, compressive and three-point bending tests to calculate the Vickers Hardness, Compressive Yield Point and Strain Energy. Before the test, 24 disk, 42 cylindrical and 42 rectangular specimens were separately stored 37oC water for 7 and 14 days, whilst remaining was tested immediately. One-way ANOVA and paired t-tests were used to statistically analyze the data at α=0.05.
Results: One-way ANOVA revealed that Vickers Hardness (p~4.60×10-41), Compressive Yield Point (p~3.65×10-8) and Strain Energy (p~1.80×10-27) are significantly different between groups. Paired t-tests showed the R-CQ could significantly improve the Hardness and Strain Energy (p<0.05) after 14 days water storage. After the 14 days water storage all R-CQ loaded resin achieve significantly (p<0.05) highest Hardness (4.94±0.61Hv), Strain Energy (15.42±1.40mJ) and Compressive Yield Point (19.83±2.86MPa) values among all other CQs.
Conclusions: R-CQ deemed to be a better activator for dental resins that could achieve a better mechanical properties.