Conservative preparation for a highly visible central incisor
32-year-old man requests replacement of a maxillary right central incisor crown (tooth 8). The existing PFM crown shows a grey cervical line at the free gingival margin. Tooth 9 is natural: shade A2 body, A3 at the cervical, with a translucent incisal halo. He has a high smile line, and only 0.8 mm of labial reduction is achievable without encroaching on the pulp - the pre-operative radiograph shows the pulp chamber 2.5 mm from the facial surface. Occlusion shows 1 mm overjet and no fremitus. He plays competitive basketball without a mouthguard. The gingival margin of 8 is 0.5 mm coronal to that of 9.
1. Which ceramic system do you choose for tooth 8, and what is the reasoning?
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Weigh three variables: available space, adhesive support, and aesthetics.
- Lithium disilicate can be used at reduced thickness (roughly 0.5–1.0 mm) in the anterior when adhesively bonded to enamel/dentine, which fits the 0.8 mm constraint and gives good translucency for matching an incisal halo. Risk: fracture and poor masking if the stump is dark.
- Zirconia offers high strength at low thickness but traditional 3Y zirconia is more opaque; multilayer/translucent generations narrow the gap but still struggle with the incisal halo of a natural central.
- Feldspathic gives the best optical match but needs lab support and adequate thickness and is the least forgiving at 0.8 mm.
Recommendation: adhesively bonded lithium disilicate, with a translucent incisal zone and layering to reproduce the halo. Warn that 0.8 mm is a compromise and that a mouthguard is mandatory given basketball and the fracture risk.
2. What are the risks of this conservative preparation, and how do you mitigate them?
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| Risk | Mitigation |
|---|---|
| Fracture of a thin restoration | Adhesive bonding to enamel margins; avoid sharp internal angles; mouthguard; consider zirconia if he refuses a guard |
| Poor masking of a dark stump | Assess stump shade before preparation; use an opaque liner or a stump-shade composite; do not simply thicken the ceramic |
| Pulpal insult | 0.8 mm is feasible with the pulp 2.5 mm away, but use water-cooled fine diamonds, avoid a shoulder that removes extra axial tooth, and check vitality post-operatively |
| Cervical grey line recurrence | Place the facial margin at or just incisal to the free gingival margin; avoid a metal substructure; consider a shoulder with a translucent cervical ceramic |
| Gingival asymmetry | 8 sits 0.5 mm coronal to 9 - plan the margin so the visible emergence matches 9, and consider minor gingivoplasty |
3. How do you plan the shade and incisal halo to match tooth 9?
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- Take a shade map, not a single shade: cervical A3, body A2, and a translucent incisal zone with a halo. A single A2 prescription will produce a flat, artificial result.
- Record under corrected lighting and include photographs with a grey card; send the photographs and the map to the technician.
- Stump shade matters: take it after preparation. A dark stump forces more opacity and kills the halo; a lighter stump gives the technician room to use translucency.
- Choose a layering technique that allows incisal translucency - pressed lithium disilicate with incisal cut-back and layering, or a refractory-die feldspathic veneer if thickness allowed.
- Try-in: use a translucent try-in paste, assess in natural light and in the dental chair, and check the halo against the adjacent central before final cementation.