Extraction
CALCULATOR
about this calculator
PURPOSE
The Extraction Calculator helps clinicians evaluate the impact of extractions on the buccal occlusion using the mathematics of anchorage and space closure. It predicts how spaces will close based on which teeth are removed and guides the selection of extractions to correct Class II and Class III malocclusions.
HOW TO USE
Measure the buccal occlusion (in mm) using the Katz classification:
Class I → Katz = 0
Class II → Katz = +
Class III → Katz = -
Enter the value into the calculator.
INTERPRETING YOUR SCORE
For each possible extraction pattern, the Extraction Calculator will display the new Predicted Katz measurement based on expected space closure (with moderate anchorage) of the extraction site.
Search for the Predicted Katz value closest to 0
This is the extraction that will minimize anchorage demands and reliance on patient compliance with their rubber band wear to achieve Class I occlusion
The calculator assumes:
Moderate anchorage (think powerchain 6-6) unless otherwise stated
Teeth of 7.5mm M-D widths
If maximum or absolute anchorage are indicated, you will need to use auxiliaries to manage anchorage, such as inter-arch elastics or TADs respectively
REFERENCES
Please visit the references page and scroll down to the “Extractions” section. If you need a more thorough description of the rationale behind the Extraction Calculator, click HERE.
EXAMPLE
Please watch the video below for an example that shows how the Extraction Calculator works.