Single-unit crowns.
Full coverage remains the most predictable restoration for a tooth that has lost substantial structure. The material choice is where most of the decision sits, and clearance decides it more than anything else.
When full coverage is the right answer
A tooth with multiple failed surfaces, one that has been endodontically treated and needs cuspal protection, one where partial coverage would leave inadequate retention, or one where the remaining structure will not support anything more conservative.
The counter-question is worth asking each time: is there enough sound structure that a partial coverage restoration would serve? Full coverage removes a substantial volume of sound tooth, including intact enamel that was contributing to strength.
Where the answer is genuinely borderline, three-quarter crowns and onlays covers the alternative.
Choosing the material
Start with available clearance, because it is the constraint that cannot be recovered after preparation. Generous clearance keeps every option open; limited clearance narrows it to zirconia or cast metal.
Then ask whether the field can be isolated well enough to bond. Then look at the antagonist and evidence of parafunction. Then assess how demanding the aesthetic requirement genuinely is.
Those four questions resolve most cases. The material selection guide sets out the options side by side.
What each option asks for
Zirconia performs in the least thickness and can be bonded or conventionally cemented. Lithium disilicate needs more room and depends on the bond, repaying it with the best optical performance. Empress is more translucent again and lower in strength.
PFM needs the most total reduction of the tooth-coloured options, because coping, opaque and veneering porcelain all consume space — but it handles long spans and non-ideal preparations that ceramics do not.
Cast metal performs in the thinnest section of anything on the form and is the kindest to opposing enamel.
Preparation fundamentals
Ten to twenty degrees total convergence, reduced anatomically rather than flat, with rounded internal line angles and a continuous, readable finish line on sound tooth structure.
Verify clearance with an index or bite registration material rather than by eye, and check in excursion as well as in maximum intercuspation. Review the preparation for undercuts along the intended path of insertion.
Where the clinical crown is short, add grooves or boxes at preparation. They cannot be introduced later without re-preparing and re-recording.
Try-in stages
The Rx form provides Try In and Finish date fields, and they exist for cases where seeing the restoration before it is finished changes the outcome.
For a metal-ceramic crown on a long span or a critical fit, a framework try-in before veneering catches a problem while correction is still inexpensive. For a demanding anterior unit, a biscuit-stage try-in lets the ceramist adjust form, characterization and colour while all three can still change.
Both cost an appointment and both convert a single high-risk delivery into two lower-risk ones. Use the field when the case warrants it.
Replacing an existing crown
Re-preparing an existing crown preparation carries a specific risk: the new finish line tends to be placed at or apical to the old one, progressively deepening with each replacement until it encroaches on the attachment.
Before deepening, ask whether the margin position was actually the problem. Frequently the failure was secondary caries on an accessible surface, or a margin that was never well adapted, and reproducing the same depth with better execution is the better answer.
Tell the laboratory what failed and why. A crown replaced for fracture is a different prescription from one replaced for a marginal deficiency.
What to put on the prescription
Tick the crown type, select the alloy where one applies, and choose the labial margin for metal-ceramic work. Give the shade with the guide named and mark the tooth on the design chart.
Add the antagonist, the interproximal contact form and tightness, and the occlusal relief. Note anything unusual — a short preparation, clearance accepted as tight, a margin uncertain on one aspect.
For anterior work, add photographs and the preparation shade.
More in Fixed Restorations
Send a case
Digital scans and conventional impressions are both accepted. Cases move by UPS and Purolator, and Fairmont works with practices throughout British Columbia and across Canada.