ORE Part 2 · Dental Manikin (DM) guide
Class V Cavity Preparation
A Class V (Class 5) cavity sits in the cervical third of the buccal or palatal surface, sized to the caries you're shown. Our two videos prepare one under the mesiobuccal cusp and one under the distobuccal cusp of an upper molar. It's one of the most demanding tests of handpiece control: the outline has to follow the curve of the gingiva at a consistent height while the cavity stays centred, shallow and smooth.
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
- An outline centred under the cusp and sized to the caries shown
- A smile- or kidney-shaped outline with well-rounded corners that follows the gingival contour
- A gingival margin kept the same distance above the gingiva along its whole length
- A smooth, well-defined margin with a 90° cavo-surface angle and no excessive bevel
- A smooth floor at an even depth, cut with the bur perpendicular to the tooth surface
- No damage to the gingiva
Common mistakes
- Lowering the gingival margin towards the gum while widening the cavity
- Letting the outline drift to one side of the cusp instead of keeping it centred
- Leaving sharp or square corners where the walls meet
- Cutting back and forth through the cavity, which costs control
- Working without a firm finger rest, or touching the gingiva with the bur
Candidate questions
How do I widen the cavity without getting closer to the gum?
Once the gingival margin is at the right level, leave it alone. Widen only from the occlusal side, and blend the corners so they stay rounded.
Why does the outline curve?
Because it follows the gingiva. The gingival margin should stay the same distance above the gum all the way along, so on a curved gingival contour the outline curves with it, giving the smile shape.
Can I work in direct vision?
Access is often better in the exam than on a home manikin, and some candidates do part of the cavity directly. Keep the mirror in your other hand and use it: the guidance expects a mirror to assist vision. The course shows two working positions.