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ADEX exam

ADEX Class III Preparation – Step-by-Step Exam Guide

How to complete a safe, pass-level Class III prep for the ADEX manikin exam — access, contact protection, dimensions, and mistakes that cost marks.

Quick Answers

What bur do I use for the Class III?

Use a small pear bur (330) or #2 round bur for access, then refine with a 56 or flame bur.

What causes most failures?

Adjacent tooth damage, unsupported enamel, over-widening the proximal area, and incorrect entry point.

What is the ideal axial depth?

Roughly 1.0 mm following the natural contour of the tooth.

Do I need to break contact?

Yes — but only minimally. Excessive clearance is a common deduction.

What is the biggest challenge?

Finding controlled access without gouging the facial or lingual surfaces.

How do I avoid overcutting?

Mark guidelines, open slowly, refine with hand instruments, and stop once criteria are met.

1. Why the Class III is deceptively difficult

Candidates often underestimate the Class III because it looks smaller than a Class II. But it tests precision, control, and enamel preservation — all areas that matter heavily in ADEX scoring.

The most common issue: candidates “chase the contact” and overcut the entire proximal wall.

2. Step 1 – Choosing the correct entry point

Entry must be controlled and minimal. Start on the lingual surface (if allowed for the tooth) to preserve esthetics.

  • Use a 330 or #2 round bur at slow speed.
  • Penetrate enamel gently until you reach dentin.
  • Do NOT enter too facially — this leads to unsupported enamel.
  • Keep the access small and rounded.

Exam tip

Start smaller than you think — you can always enlarge, but you cannot reverse an overcut.

3. Step 2 – Creating internal form and axial wall

The axial wall should follow tooth contour and remain smooth, around 1.0 mm depth.

  • Use the long axis of the tooth as your guide.
  • Avoid flattening the curve of the axial wall.
  • Avoid dips or irregular depth — this is a common deduction.

4. Step 3 – Proximal extension and breaking contact

Breaking contact is mandatory, but minimal clearance is preferred.

  • Carefully open the proximal wall toward the contact.
  • Switch to hand instruments to avoid adjacent tooth damage.
  • Clearance should be ≈0.25–0.5 mm — very small.
  • Avoid box-like shapes; keep it rounded and conservative.

Automatic failure risks

● Adjacent tooth nicked or scratched
● Via facial overextension
● Unsupported facial/lingual enamel

5. Step 4 – Smoothing and finishing

The finish should look controlled and intentional. Examiners dislike rough, jagged margins.

  • Use 56 bur or hand instruments for final refinement.
  • Check all margins for unsupported enamel and remove it gently.
  • Ensure the entry point is rounded and smooth.

6. The most common Class III errors (ADEX examiner data)

  • Over-widened proximal extension
  • Flat axial wall (not following contour)
  • Facial enamel unsupported or overcut
  • Contact not fully broken
  • Entry point too large or too facial

7. Compare this with Class II criteria

If you already read our ADEX Class II preparation guide, you will notice the same themes: controlled access, smooth axial wall, enamel preservation, and minimal extensions. Understanding both preps together gives a clearer sense of how examiners evaluate precision.

8. How DentAIstudy helps you master the Class III

DentAIstudy can transform the Class III scoring sheet into practical learning tools:

  • Short checklists to use beside the manikin
  • Flashcards for high-yield mistakes and fail points
  • OSCE-style scenarios for anterior restoration decisions
  • Step-by-step flow summaries for practice review

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References

  • ADEX Candidate Manual – Class III Performance Criteria.
  • Anterior restoration preparation guidelines.
  • Examiner calibration summaries from recent administrations.