Common crown design flaws include bad margins, over-contoured cervical areas, black triangles, and occlusal high spots. Most come from one rushed or skipped step in the workflow, not from a designer lacking skill. Margin errors are the most likely to cause a chairside remake.
Most crown design flaws aren't the result of a designer not knowing what they're doing — they're the result of one step in the workflow getting rushed or skipped under deadline pressure. Here's what to look for, and where each flaw usually comes from.
Bad margin fit
Usually traces back to the margin-marking step: a prep line traced too quickly, or a subgingival margin inferred incorrectly from incomplete scan data. This is the flaw most likely to cause a chairside remake, since it affects whether the crown seats correctly at all.
Over-contoured cervical margins
Often happens when a library proposal is accepted too close to its default rather than adjusted for the actual prep, or when a designer compensates for a slightly under-reduced prep by adding bulk near the margin instead of flagging the issue.
Black triangles
Visible gaps below the contact point, usually caused by a contact placed too high or an emergence profile that doesn't fill the interproximal space the way the natural tooth did. More common on anterior cases, where it's also more visible.
Occlusal high spots
The single most common cause of a crown coming back for adjustment. Almost always traces to checking centric occlusion only, and skipping the lateral and protrusive excursion checks where the actual high spot was hiding.
Contacts too tight or too loose
Too tight makes flossing difficult for the patient; too loose lets food pack into the gap. Both are adjustment calls that should be made deliberately against the lab's stated preference, not left at the software's default.
Insufficient wall thickness for the material
Zirconia, e.max, and PFM each have different minimum thickness requirements. A design that looks fine anatomically can still fail in the mill or under bite force if this wasn't checked against the specific material being used.
Emergence profile that doesn't support the tissue
A crown that balloons out or pinches in near the gum line, rather than transitioning naturally. This one doesn't usually cause an immediate remake, but it shows up over time as tissue irritation or recession around the restoration.
What almost all of these have in common
Every flaw on this list traces back to a step in the design workflow that got rushed, skipped, or checked only partially — not to a designer lacking skill. That's true whether the design was done in-house or outsourced. The fix isn't finding a "better" designer; it's a workflow and a QC pass that doesn't let any of these steps get shortcut under deadline pressure.