IADR Abstract Archives
Mechanisms and Loss Rates of Enamel Using air-Abrasion and Nanoimpact
Objectives: To use air-abrasion to determine whether engineering erosion theory can be applied to enamel to differentiate the damage mechanisms (brittle or ductile) using rates of loss at different angles and resultant scar shape. In addition, nano-impact will be used to determine if the link between D/d ratio and damage mechanism, (D: contact footprint diameter of the impacting particle, d: column diameter) for columnar structured engineering materials also applies to enamel.
Methods: Bovine enamel samples (n = 10) were subjected to air abrasion for 5 periods of 2 seconds, at an air pressure of 5 Bar using a 54 µm Al2O3 powder. The incident angle of the particle flow was set at either 900 (n = 5) or 450 (n = 5). The samples were weighed (scales accurate to 0.01 mg), and the scar imaged after each period using a Proscan 2100 (Scantron, Taunton, UK). A bovine enamel samples was subjected to 10 nanoimpacts at a load of 10mN at flight distances of 4, 8, 12, 16, 20 and 24μm for each of the spherical tip sizes: 5, 10, 50, 100, 200, 500 μm. The coefficient of restitution (COR), dynamic hardness (DH) and dynamic depth (DD) was determined for each impact.
Results: The air-abrasion testing demonstrated a higher loss rate when particle impingement was at 90o, with u shaped scars, indicating a brittle loss mechanism. The nanoimpact experiments showed a direct linkage between the nanoimpact response and the D/d ratio, with a clear inflection in the COR and DD when the D/d ratio was <2.
Conclusions: The air-abrasion of enamel enabled the application of engineering erosion theory to identify the brittle behaviour of enamel during air abrasion, while the nanoimpact experiments demonstrated the influence of the D/d ratio on the enamel’s response to single particle impacts.
Methods: Bovine enamel samples (n = 10) were subjected to air abrasion for 5 periods of 2 seconds, at an air pressure of 5 Bar using a 54 µm Al2O3 powder. The incident angle of the particle flow was set at either 900 (n = 5) or 450 (n = 5). The samples were weighed (scales accurate to 0.01 mg), and the scar imaged after each period using a Proscan 2100 (Scantron, Taunton, UK). A bovine enamel samples was subjected to 10 nanoimpacts at a load of 10mN at flight distances of 4, 8, 12, 16, 20 and 24μm for each of the spherical tip sizes: 5, 10, 50, 100, 200, 500 μm. The coefficient of restitution (COR), dynamic hardness (DH) and dynamic depth (DD) was determined for each impact.
Results: The air-abrasion testing demonstrated a higher loss rate when particle impingement was at 90o, with u shaped scars, indicating a brittle loss mechanism. The nanoimpact experiments showed a direct linkage between the nanoimpact response and the D/d ratio, with a clear inflection in the COR and DD when the D/d ratio was <2.
Conclusions: The air-abrasion of enamel enabled the application of engineering erosion theory to identify the brittle behaviour of enamel during air abrasion, while the nanoimpact experiments demonstrated the influence of the D/d ratio on the enamel’s response to single particle impacts.