Restorative & Materials · single question
A patient has a mesio-occlusal (MO) caries on tooth #30 (mandibular right first molar). What is the most appropriate approach to begin the cavity preparation?
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Correct answer: C. Occlusal approach
For a mesio-occlusal (MO) cavity on a posterior tooth, the preparation is started from the occlusal surface. The occlusal entry allows proper access, visualization, and establishment of the preparation outline form before extending to the mesial box. Starting occlusally provides the path of entry needed to access the proximal (mesial) box safely and without damaging adjacent structures.
- A. CORRECT. MO (or MOD) preparations begin with an occlusal entry point to establish access, then extend to the proximal box. The occlusal approach is always the starting point for posterior composite/amalgam preparations.
- B. Incorrect. A direct mesial approach would risk damage to the adjacent tooth and does not provide adequate access or visualization for the preparation.
- C. Incorrect. A buccal approach is used for class V preparations (cervical lesions) or specific access situations — not for MO cavities.
- D. Incorrect. A lingual approach is not standard for MO preparations on mandibular molars.
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