Measured diagram
Does acid change the shape of a notch at the gum line?
A close-up of the neck of the upper premolar drawn in the other figures, with a 1 mm scale. In a laboratory study on extracted premolars, brushing alone made sharp wedges of about 60 degrees; with acid as well, more tooth was lost and the notches were open dishes of about 145 degrees. Both outlines are drawn on one tooth so that their shapes can be compared.
What the drawing is measured from
- Acid: on extracted premolars brushed for the same number of strokes, brushing alone made wedges in 94% at a mean angle of 59 degrees; with acid as well, more tooth was lost and the notches were open, at about 145 degrees, none of them a wedge. Denucci and colleagues, Arch Oral Biol 2025. DOI 1
- Shape: depth to height ratios measured over years in patients were 0.49 to 1.01 for wedges and 0.13 to 0.44 for rounded notches, so a wedge is at most about as deep as it is tall. Sugita and colleagues, a pilot study of 10 notches, J Dent 2017. DOI 2
- Position: in 50 teeth scanned by micro-CT, the edge of every notch on the crown side lay at or below the junction of enamel and root, which is why none is drawn cut high into the enamel. Hur and colleagues, J Oral Rehabil 2011. DOI 3
- Floor: the floor of a notch is smooth and hard, honey-coloured to dark brown and darkest along its deepest line; fine lines along the walls were seen on wedges, not on rounded notches. Stanusi and colleagues, 27 teeth under the stereomicroscope, Diagnostics 2023. DOI 4
- The tooth is an upper second premolar traced from Wheeler's Dental Anatomy (11th edition, Figs 9.17 and 9.20) and scaled to its measurement table: crown 8.5 mm, root 14 mm, 9 mm from cheek to palate. The depth and height of each notch follow the studies above; none is a measurement of one patient.
Use this diagram
Free to use, including commercially, with credit.
This diagram is published under CC BY 4.0. You may reproduce it in articles, teaching material, presentations and patient information, print or online, without asking. The one condition is that you credit Dr. Khalid Aletaibi and link back to this page.
It is published this way on purpose. The measurement in this drawing is not something the people selling the treatment tend to publish, so it is more useful spread than kept.
Credit line
The same brushing, with and without acid. Dr. Khalid Aletaibi, CC BY 4.0. https://khalidaletaibi.com/en/diagrams/lesion-wedge-dish
HTML embed
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<img src="https://khalidaletaibi.com/figures/lesion-wedge-dish-en.svg?v=2" alt="The same brushing, with and without acid" width="100%">
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The same brushing, with and without acid. <a href="https://khalidaletaibi.com/en/diagrams/lesion-wedge-dish">Dr. Khalid Aletaibi</a>,
<a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>
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