ORE Part 2 · Dental Manikin (DM) guide
Full Gold Crown Preparation
A full-coverage gold crown preparation, checked against a sectioned putty index throughout. The challenge is an even occlusal reduction that keeps the tooth's cuspal anatomy, a functional cusp bevel at the right angle, continuous margins at an even level, and axial walls whose taper comes from a straight bur — all without touching the neighbouring teeth.
Our video demonstrates this on an upper first molar (26). In the exam, the tooth and exercise are set on the day.
What examiners look for
- Occlusal reduction cut one cusp at a time, preserving the central fissure and cusp slopes rather than flattening the table
- A functional cusp bevel on the palatal cusp, cut at the same angle as the buccal cusp plane
- Planar axial reduction — bur tip out for the occlusal third, straight for the middle third, in for the gingival third
- A continuous margin of even width (the tip of a 170 bur) about 1 mm above the gingival margin on every surface, flat rather than inverted
- Proximal walls cut with the bur dead straight — its natural shape supplies the taper — and margins that meet the buccal and palatal margins at the same level
- No undercuts, no nicks on the adjacent teeth, and a smooth finish
Common mistakes
- Flattening the occlusal surface in one pass instead of reducing cusp by cusp with the bur tip at the central fissure
- Skipping or under-cutting the functional cusp bevel, leaving too little bulk for the gold
- Checking the putty index too rarely and over-reducing — or reading only one half of the sectioned index
- Using the whole bur body at the gingival third, over-reducing the wall while widening the margin: use only the tip there
- Letting the bur slip into the adjacent tooth during proximal reduction — a double matrix band and a wedge against the non-working tooth protect it
- Leaving the margin inverted or rough instead of flat and smooth (the hatchet cleans it up)
What the official DM Guidance states
- Occlusal reduction: 1 mm even reduction over the whole occlusal surface, with a 1.5 mm functional cusp bevel
- Axial reduction giving a 6°–20° taper, with no undercuts
- Margin: a 0.5–0.75 mm chamfer, continuous and even around the tooth, about 1 mm above the gingival margin
- Contacts cleared with the adjacent teeth by about 0.5 mm
- Smooth finish with no sharp angles; path of insertion perpendicular to the occlusal plane
- Checked with an index sectioned once in the middle of the tooth
Source: ORE Part 2 Dental Manikin (DM) Guidance, version 2.0, effective 1 March 2026, p. 18. Values marked “about” are approximate in the guidance. Check the current version before your exam. How to reach these, step by step, is in the course.
Candidate questions
Why reduce one cusp at a time?
Keeping the bur tip at the central fissure and sweeping one cusp with the whole bur body reproduces that cusp's plane in miniature — the reduced surface keeps the tooth's anatomy, which is exactly what the examiners want to see under the putty index.
What is the functional cusp bevel for?
The palatal (functional) cusp takes the occlusal load, so the crown needs extra metal thickness there. The bevel is cut at the same angle as the buccal cusp plane to create room for that bulk.
Where does the taper come from?
From keeping the 170 bur straight: its natural shape gives the required taper on the axial walls. Tilting the bur changes the taper and risks undercuts — if one appears, it is removed by tilting slightly towards the tooth being prepared.