Three restoration options exist along a conservatism spectrum. Here is how to know which one fits your tooth.
Filling - the most conservative option
A filling replaces decayed or damaged tooth structure with composite resin bonded directly to the tooth. Best for: Small-to-medium cavities where most of the tooth is intact. Cost: $200-$450. Lifespan: 7-15 years. Limitations: Not suitable for large restorations where cusps need replacement; can fracture under heavy load.
Onlay - the middle ground
An onlay is a partial crown - covers one or more cusps but not the entire tooth. Made in a lab from porcelain, e.max, zirconia, or gold. Best for: Teeth with significant decay or fracture but still salvageable structure; replaces large failing fillings; protects after root canals on certain teeth. Cost: $1,000-$1,600. Lifespan: 15-20 years. Strengths: More conservative than a crown; preserves more natural enamel.
Crown - the comprehensive solution
A crown covers the entire visible portion of the tooth. Best for: Heavily damaged teeth, post-root canal protection, fractured teeth, severely worn teeth, or teeth needing significant aesthetic correction. Cost: $1,200-$1,800. Lifespan: 15-20 years. Trade-offs: Most aggressive preparation; removes the most natural enamel.
Decision logic
How we decide:
- <1/3 of tooth structure missing: Filling.
- 1/3 to 1/2 of tooth structure missing, no cusp involvement: Filling or onlay (depends on bite forces).
- 1/2 to 2/3 of tooth structure missing, one or more cusps weakened: Onlay.
- >2/3 of tooth structure missing OR after root canal on a back tooth: Crown.
- Severe fracture or aesthetic concern requiring full coverage: Crown.
We always discuss the most conservative option that will hold up.
When to upgrade an existing filling
Indications for upgrading a filling to onlay or crown:
- Recurrent cavity at the same filling.
- Filling becoming larger with each replacement.
- A vertical crack in the tooth visible under the filling.
- One or more cusps already showing fracture or fatigue.
- Sensitivity to biting that suggests structural compromise.
Upgrading at the right time prevents the much more expensive scenario of a fractured tooth that requires a root canal plus crown - or an extraction plus implant.
Frequently asked questions
- Why not just get a crown if it lasts longer?
- Crowns require more aggressive preparation, removing more healthy enamel. A successful filling that preserves enamel is biologically the better option for a tooth that doesn't need a crown.
- Do onlays last as long as crowns?
- Yes, in modern materials - onlays in zirconia or e.max can last 15-20+ years. Lifespans are comparable for the same patient and bite.
- Will insurance cover an onlay?
- Most plans cover onlays at the major-restorative tier (50%) - same as crowns. Some plans require pre-authorization.
- Can I have an onlay placed same-day?
- Yes - chairside CEREC technology can mill onlays in a single visit, similar to same-day crowns.