Axial taper on a crown prep: 12° or less per wall

Taper is measured against the line of draw, the path the crown seats along. Each wall is read on its own; the sheet’s numbers are per wall, so they are never doubled or added across opposing walls.

The 12°-per-wall limit

The 2026–27 crown-prep criteria sheet for a molar reads: “Taper is present, from nearly parallel to ≤ 12°.” A wall that leans more is “There is excessive taper that is > 12° and ≤ 16°.” and the worst band is “The taper is grossly over-reduced > 16° per wall.”

OslerPress scores a wall at 12° or less as within, the sheet’s acceptable band; over 12° to 16° and over 16° per wall score as outside.

Why 16° per wall fails

Too much taper loses retention and resistance. A wall measured at 16° is over the 12°-per-wall limit, so that checkpoint scores as outside, in numbers, and the fix is to close the walls.

Check your taper

Photograph the buccal and lingual views at the same distance and light. OslerPress measures the angle and compares it with your last prep.

Fix it

Hold the tapered diamond parallel to the line of draw and let its own taper make the wall. Students who over-taper usually tilt the bur on the buccal and lingual walls; one D2 wrote that they “always overtaper the buccal and lingual surfaces”.