Replacing two anterior crowns in a high-smile-line patient with a five-month deadline
A 34-year-old woman attends asking for the 'grey crowns' on her two front teeth to be replaced before her wedding in five months. Both crowns were placed after a bicycle accident eight years ago. She has a high lip line that shows 3 mm of gingiva at a full smile and states that she wants 'no metal and no grey line in two years'. Examination shows metal-ceramic crowns on 11 and 21 with dark margins visible at the gingival third, 4 mm of clinical crown height, probing depths of 3 mm with no bleeding, 2 mm of buccal keratinized tissue, and gingival zeniths of 11 and 21 that are 1.5 mm more coronal than those of 12 and 22. Both teeth are root-filled with 5 mm of apical gutta-percha and no periapical pathology. She grinds at night, has wear facets on the canines and premolars, and marked masseter hypertrophy. She is a non-smoker, takes no medication and has no relevant medical history. No diagnostic wax-up has yet been made.
1. Would you choose surgical crown lengthening or forced orthodontic extrusion to gain ferrule and correct the margin position? Justify the choice in this patient.
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What both options must achieve
At least 1.5-2 mm of circumferential sound tooth structure (ferrule) and a margin placed where a 3 mm gingival display will not reveal it, with about 3 mm from the margin to bone to re-establish the biologic width.
Surgical crown lengthening
Moving the margin 3-4 mm apically means removing 3-4 mm of labial bone. In a patient with a high smile line and only 2 mm of buccal keratinized tissue this will elongate 11 and 21, flatten the interdental papillae and make the asymmetry with 12 and 22 worse. Keratinized tissue of 2 mm is borderline for healing. It solves the ferrule problem but creates an aesthetic one that cannot be undone.
Forced eruption
Orthodontic extrusion at roughly 1 mm per week, with a supracrestal fibreotomy at each visit to prevent the bone and gingiva travelling with the tooth, moves the margin coronally while the bone level stays where it is. The zenith and the bone are preserved, which is exactly what this patient needs. Three millimetres over three to four weeks, then four to six weeks of stabilisation, is realistic inside the five-month window.
The limiting factor
If ferrule after extrusion is still under 1.5 mm, restorability - not material choice - determines the outcome, and the tooth may need a post-core or extraction. Reserve surgical lengthening for a defect that extends so far apically that extrusion would exceed 4 mm.
2. How would you choose the crown material, given her aesthetic demand, her root-filled abutments and her nocturnal grinding?
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The competing demands
- Aesthetic: a high smile line with a translucent incisal third, and a demand for no grey show-through.
- Substrate: root-filled teeth, so the core is dentine and composite, not enamel - adhesive bonding is weaker than it would be to enamel.
- Parafunction: wear facets and masseter hypertrophy mean the restorations will be loaded far beyond normal function.
The options
- Metal-ceramic: the most documented, but opaque and the very thing she is complaining about.
- Lithium disilicate: flexural strength around 360-400 MPa, the most lifelike of the three, but it depends on a good adhesive bond and 1.0-1.5 mm of reduction; it is the least forgiving in a grinder.
- Monolithic zirconia: 3Y-TZP in the order of 1000 MPa or more, chip-resistant, can be thinner, but more opaque and harder to resin-bond.
A defensible decision
Either is justifiable, but the reasoning must be stated: lithium disilicate if the occlusion can be controlled and she will wear a night guard; monolithic zirconia, built up only in the incisal third if at all, if the parafunction is judged severe. Do not choose on shade alone. Regardless of material, the design decisions matter most: adequate ferrule, no cantilever, and a verified occlusion with a protective splint.
3. Outline the clinical and laboratory sequence you would use to deliver the crowns in five months with a stable, aesthetic gingival result.
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Provisional restorations are the try-out
The provisionals, not the final crowns, decide incisal edge position, midline, smile line, phonetics and the gingival zenith. Everything else is executed to reproduce them.
Sequence
- Week 0: diagnostic wax-up from the planned post-extrusion position; photographs, shade map, facebow or CR record as indicated.
- Weeks 0-4: forced eruption of 11 and 21 with fibreotomy; provisional crowns relined to follow the teeth.
- Weeks 4-10: prepare, then provisional restorations with correct emergence and a convex profile to mould the papillae. Review at two and six weeks; adjust if the zenith does not match 12 and 22.
- Weeks 10-12: final impression only when the gingival margin has been stable for two to four weeks, with retraction cord and a verify record.
- Weeks 12-16: try-in, refine contacts and guidance, glaze and cement.
- Week 20: review and fit a night guard.
The honest conversation
Five months leaves no slack for a lost crown or a second extrusion. Tell her so at the first visit, offer a later fitting date after the wedding as a fallback, and record that the risk of the deadline was discussed.