IADR Abstract Archives
Pore-Size Image Analysis of Four Selected Chairside Traps
Objective: Dental-unit wastewater contains a mixture of irregularly shaped Hg-containing particulates of large to submicron (colloidal) size. Chairside trap pore size, which directly affects Hg emissions, has been reported to be 700μm (Cailas, et. al., 1994, 2002). This project used image analysis to obtain accurate estimates of trap pore size. Methods: Four different trap models were obtained from three dental supply companies: DentalEZ, Inc., Pinnacle Products, Inc., and PartsWarehouse, Inc. (one trap of each type was analyzed). Each trap was placed on the stage of a light microscope. Images were acquired with a camera, frame grabber, and computer. Image analysis was completed utilizing ImagePro-Plus version 4.1.00.00. Multiple pores from each trap were analyzed for size and aspect ratio. Results:
Table 1: Data (mean and SD) from square pore traps.
|
|
Length, μm |
Width, μm |
Feret's1, μm |
Aspect2 |
|
Trap 1 (n=99) |
1156.76(108.81) |
1121.51(103.51) |
1348.95(21.56) |
1.03(1.01) |
|
Trap 2 (n=110) |
1126.61(233.73) |
1038.54(293.90) |
1239.74(242.77) |
1.41(4.56) |
|
Trap 3 (n=200) |
749.18(77.79) |
600.44(122.99) |
889.45(87.36) |
1.43(1.44) |
1Feret's diameter is the greatest dimension between any two points along the boundary. 2Aspect is the ratio of the longest to shortest dimension.
Table 2: Data (mean and SD) from a round pore trap.
|
|
Diameter, μm (max) |
Diameter, μm (min) |
Diameter, μm (mean) |
Roundness3 |
|
Trap 4 (n=199) |
936.18(29.07) |
894.63(79.55) |
918.84(55.00) |
1.37(1.96) |
3Roundness is a measure of how far the pore shape differs from a circle.
Conclusions: All Traps surveyed had at least one dimension greater than 700μm. When traps are the only abatement mechanism, our findings suggest greater potential for Hg emissions than was previously assumed. Manufacturers, by re-engineering traps with reduced pore size, have the opportunity to contribute to the reduction of environmental Hg contamination. This study was supported by the US Navy and the USEPA.