November 2007 | Courtesy of BEGO USA
Be Aware of the Trailing Edge
Short castings are easier to avoid than you may think.
Every time casts are made centrifugally, they're governed by Newton's first law of motion: an object in motion tends to stay in motion in the same direction. We see this in our daily lives. When a car turns left quickly, your body moves right. The same thing happens to alloy being cast into a casting ring.
Understanding this effect can help improve your casts.
- If the casting ring system has a dot in the base former, sprue the restorations over the dot.
- If the base former lacks an identifying dot, create one on the base in wax.
- After the waxed units are invested and removed from the ring, the indicating dot transfers into the investment, showing the position of the wax up in the mould.
- By knowing the location of the restoration in the invested mould, you can take advantage of the casting arm's forces.
- If the casting arm takes off clockwise, place the mould in the cradle with the identifying dot positioned away from the take-off direction. The alloy will move in conjunction with the natural flow direction.
Awareness of the trailing edge eliminates costly remakes for you and rescheduling problems for patients.
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