Restorative & Materials · patient case question

Where should the bevel be placed for this Class IV composite restoration?

Patient case: A thin gingiva and a fractured incisal edge

Patient: Female, 29 years old

Chief Complaint: “I chipped the corner off my front tooth.”

Background: Healthy, non-smoker, excellent plaque control. No history of periodontal disease.

Vital Signs: BP 112/70 mmHg · HR 68 bpm

Findings: Tooth #8 has an uncomplicated fracture of the mesio-incisal angle involving enamel and dentine with no pulp exposure; a Class IV composite is planned. The gingiva is delicate and translucent with a highly scalloped margin, a narrow band of keratinised tissue, and root outlines visible through the soft tissue. Crowns are narrow and triangular.

  1. On the facial ENAMEL surrounding the preparation, as a long chamfer or bevel
  2. On the axiopulpal line angle
  3. On the incisal edge only
  4. On the lingual DENTINE
Show answer and explanation

Correct answer: A. On the facial ENAMEL surrounding the preparation, as a long chamfer or bevel

  • A. CORRECT. The bevel is cut in ENAMEL on the FACIAL surface, extending roughly 1 to 2 mm around the periphery of the preparation — often described as a long chamfer or a scalloped bevel. It serves three purposes, all of which matter in an anterior restoration. It exposes the ENDS of the enamel rods rather than their sides, which markedly improves the etch pattern and bond strength. It increases the SURFACE AREA available for bonding. And it creates a gradual, blended transition in restoration thickness that optically HIDES the margin — the aesthetic reason an unbevelled Class IV shows a visible line.
  • B. The axiopulpal line angle is bevelled in AMALGAM preparations, notably Class II, in order to reduce stress concentration within a brittle material. It is a different material serving a different purpose and has no application to a bonded anterior composite.
  • C. Bevelling only the incisal edge leaves the remainder of the margin as a butt joint, which is inferior both adhesively and aesthetically at precisely the visible margins that matter.
  • D. A bevel placed in dentine achieves nothing. The rod-geometry argument applies only to ENAMEL, and bevelled dentine simply thins the restoration at its margin without improving the bond.

Note: This appears frequently as an EXCEPT item, so note what a bevel does NOT do: it does not prevent marginal fracture. If anything, a very thin feather-edged composite margin is MORE prone to chipping. Its three genuine purposes are bond strength, surface area and aesthetic blending. Note also the favourable geometry here — a Class IV has a low configuration factor, so polymerisation shrinkage stress is much less of a problem than in a Class V or Class I.

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