Poor cervical margin adaptation (especially deep boxes)
What it is
In Class II restorations with a deep cervical/gingival margin (often at or below the CEJ), the composite does not adapt or seal well at the cervical margin. This can produce marginal gaps, which are strongly associated with microleakage, marginal staining, food packing, postoperative sensitivity, and recurrent caries — and these problems are more likely when the cervical margin is on dentin/cementum and access/isolation are difficult.
Why it happens
• Margin location below CEJ: bonding to dentin/cementum is generally more technique-sensitive than enamel, and deep margins are harder to visualize and finish. • Moisture contamination from sulcular fluid/bleeding at deep margins → compromised adhesive interface. • Matrix band adaptation problems at the gingival seat (band lift, inadequate wedging/retraction) → poor cervical seal and gaps. • Polymerization shrinkage stress in a deep, high C-factor area can pull composite away from the cervical margin if adaptation is weak.
The full clinical mistake entry includes
- How to avoid it — the prevention protocol
- The clinical tip experienced clinicians use
- The documented reference behind the mistake
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