IADR Abstract Archives
Comparison of e.max Material Removal by Coarse and Fine-grit Diamond Burs
Objectives: Controversy exists concerning whether fine-grit or coarse-grit diamond burs are better for removal of existing all-ceramic crowns. This study compared these two types of burs in removal of all-ceramic material, specifically IPS e.max (Ivoclar Vivadent, Amherst, MA), a lithium disilicate ceramic.
Methods: Two types of single-patient-use round end taper dental burs were tested: a coarse grit bur (Model #1118.7C, Neodiamond, Microcopy, Kennesaw, GA), with a nominal particle size of 150m diamond; and a fine grit bur (Model #1118.7F, Neodiamond), with a nominal particle size of 50m diamond. Burs were tested using a universal testing machine (Instron E3000, Instron Norwood, MA) equipped with a custom-made fixture that rigidly held a high-speed dental hand-piece (25 LPA, Kavo, Charlotte NC) to the movable cross head. Blocks of IPS e.max were tempered in a process furnace (Programat CS, Ivoclar Vivadent) and secured to the lower crosshead.
The hand-piece was operated at a constant speed of 200,000 RPM with water spray. Load was applied to the bur using a cyclic, trapezoidal, wave pattern (Figure 1). The maximum load applied was 4N; the dwell time at load was 2 seconds. The loading and unloading times were 0.75 seconds. The minimum lower load was set at 0.5N and maintained for 1 second before again ramping to the higher load. The cycling was repeated for 320 seconds. Average volume of material removed was recorded, averaged and compared using Student’s T-test with α=0.05.
Results: The average volume removed with the fine grit bur was 22.14 ± 2.63 mm3 while the average volume removed with the coarse grit bur was 52.08 ± 3.75 mm3. Results were significantly different (p < 0.001) (Figure 2).
Conclusions: Coarse-grit burs removed a greater volume of material than fine-grit burs using the same application force and time. Thus, coarse-grit burs may provide for faster e.max crown removal.
Methods: Two types of single-patient-use round end taper dental burs were tested: a coarse grit bur (Model #1118.7C, Neodiamond, Microcopy, Kennesaw, GA), with a nominal particle size of 150m diamond; and a fine grit bur (Model #1118.7F, Neodiamond), with a nominal particle size of 50m diamond. Burs were tested using a universal testing machine (Instron E3000, Instron Norwood, MA) equipped with a custom-made fixture that rigidly held a high-speed dental hand-piece (25 LPA, Kavo, Charlotte NC) to the movable cross head. Blocks of IPS e.max were tempered in a process furnace (Programat CS, Ivoclar Vivadent) and secured to the lower crosshead.
The hand-piece was operated at a constant speed of 200,000 RPM with water spray. Load was applied to the bur using a cyclic, trapezoidal, wave pattern (Figure 1). The maximum load applied was 4N; the dwell time at load was 2 seconds. The loading and unloading times were 0.75 seconds. The minimum lower load was set at 0.5N and maintained for 1 second before again ramping to the higher load. The cycling was repeated for 320 seconds. Average volume of material removed was recorded, averaged and compared using Student’s T-test with α=0.05.
Results: The average volume removed with the fine grit bur was 22.14 ± 2.63 mm3 while the average volume removed with the coarse grit bur was 52.08 ± 3.75 mm3. Results were significantly different (p < 0.001) (Figure 2).
Conclusions: Coarse-grit burs removed a greater volume of material than fine-grit burs using the same application force and time. Thus, coarse-grit burs may provide for faster e.max crown removal.
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