Two ways to repair a tooth
When a tooth is damaged by caries or a fracture and a part of the substance is missing, there are two main categories of restorative care: the direct filling (composite) and the indirect restoration (inlay or onlay).
Both procedures are established. Composite is the most common solution because it is efficient, cost-effective and completed in one session. Inlay is the high-quality alternative with larger defects or high demands on lifespan and precision. This article explains the differences and the indications.
Composite filling
Composite is a tooth-colored plastic placed directly in the mouth in the tooth defect, shaped, polymerized (cured with blue light) and polished. The entire procedure takes place in one session of 20 to 60 minutes, depending on size.
Advantages:
- One session, no lab order.
- Substance-saving, because only the carious or defective substance is removed without additional preparation effort.
- Lower costs than an inlay.
- Tooth-colored, aesthetically inconspicuous.
- Repairable, smaller damages can be fixed in the practice.
Disadvantages:
- Shorter lifespan than inlay, usually 7 to 10 years, depending on loading.
- Discoloration susceptibility at the edges over the years.
- Shrinkage on curing, which can lead to gap formation with very large fillings.
- Less suitable with very large defects, because stability is insufficient.
Inlay (lab fabricated)
An inlay (Latin for “insert”) is a restoration that is not directly modeled in the mouth but is precisely fabricated in the lab and bonded into the tooth in a second session.
Materials:
- Ceramic (lithium disilicate or feldspar): tooth-colored, aesthetically very high-quality.
- Composite (lab-fabricated): tooth-colored, slightly cheaper than ceramic.
- Gold: very long lifespan, robust mechanical properties, clearly visible.
Advantages:
- Long lifespan, 15 to 25 years and more in studies.
- Highest precision in fit and bite adjustment, because fabricated in the lab under ideal conditions.
- High material strength, suitable for large defects and high loading.
- Discoloration resistance, especially with ceramic and gold.
- Ideal shape for contact points to neighboring teeth, which reduces caries risk.
Disadvantages:
- Two sessions plus lab waiting time of one to two weeks.
- Higher costs, depending on material double or triple a composite filling.
- Higher substance preparation, because space must be created for the inlay.
- With fracture often complete renewal needed, because repair in the mouth is difficult.
Comparison by criteria
Lifespan
Composite filling: on average 7 to 10 years, with large variation depending on position, loading and oral hygiene.
Inlay: on average 15 to 25 years for ceramic and composite inlay, up to 30 years for gold inlay.
Calculated over 20 years that means: a composite would need to be renewed one to two times during this time, an inlay presumably not. The total costs partly equalize.
Precision of fit
Inlay has a clear advantage. The lab fabrication allows micrometer-accurate fit at the contact surfaces to neighboring teeth and at the bite adjustment.
Composite is good in skilled hands and with modern technique (matrix bands, polymerization lamps) but not as precise as lab work.
Substance loss
Composite is slightly more substance-saving because only the defective substance is removed.
Inlay requires additional preparation to create space for the restoration. With modern inlay concepts (adhesive inlay) this preparation can be minimized.
Aesthetics
Both procedures deliver aesthetically high-quality results with tooth-colored materials. Ceramic inlays tend to have more depth and brilliance than composite; the difference, however, is clinically barely relevant in the posterior area.
Gold inlays are visible and have their own aesthetic. They are used today mainly in the very rear posterior area or with explicit patient preference.
Caries risk
Inlay reduces the caries risk at the contact surfaces slightly because the precise shape forms no plaque trap.
Composite has over the years a slightly higher caries tendency at the edges, especially when oral hygiene is not consistent.
Costs
Concrete amounts vary by material and effort. Bandwidths are not in a dedicated Resident article but are addressed in the general insurance context, in the article Health insurance at the dentist.
Rough tendency:
- Composite filling: lowest range.
- Composite inlay: middle range, about 1.5 times.
- Ceramic inlay: higher range, about 2 to 3 times.
- Gold inlay: highest range, about 3 to 4 times.
Treatment duration
Composite filling: 20 to 60 minutes in one session.
Inlay: two sessions of 30 to 60 minutes plus 1 to 2 weeks of lab time.
Which restoration for which indication
Small caries lesion
Recommendation: composite filling. Quick, cost-effective, fully sufficient.
Medium defects with two or three affected tooth surfaces
Recommendation: composite filling in most cases. With additional requirements (very high loading, visible area with aesthetic demand) an inlay is sensible.
Large defects with four or more affected surfaces
Recommendation: inlay or crown, because a large composite filling does not sufficiently restore the stability of the tooth. The choice between inlay and crown is the topic in the article Inlay vs crown.
Root-treated teeth in the posterior area
Recommendation: inlay (onlay) or crown. A root-treated posterior tooth needs a substance-supporting restoration that does more than a direct filling. More in the article on root canal treatment and Root canal or extraction.
Patient with high bite force
Recommendation: inlay, because larger composite fillings wear out or chip faster under strong loading.
Patient with preference for maximum lifespan
Recommendation: inlay, because the average lifespan is significantly higher and exchange treatments are rarely needed.
Patient with budget limit
Recommendation: composite filling as a proven standard solution. The restoration is high-quality, cost-effective and fulfills its purpose. With later necessity it can be switched to inlay.
Special case onlay
An onlay is a variant of the inlay that additionally to the inner surfaces also covers one or more cusps of the tooth. It is the solution for teeth with missing cusp substance that do not yet require a complete crown.
Onlay is often recommended after root canal treatments because the root-treated tooth needs protective cusp coverage without the whole crown being required.
How Resident proceeds
- Clinical examination of the affected tooth with caries diagnostics, sensitivity test and possibly X-ray.
- Treatment planning with choice of the suitable restoration. With multiple options we discuss the pros and cons transparently.
- Written cost estimate with inlay and larger restorations. More in the article on the cost estimate.
- Treatment in one session (composite) or two sessions (inlay) with precise course.
- Follow-up check in the next dental hygiene session, at the latest after six months.
We recommend the restoration that is medically and long-term sensible for your constellation. If composite is sufficient, we do not advise the more expensive inlay. If inlay is the better solution, we say so openly with justification.
Arrange an appointment for an assessment. We take time for the treatment planning and discuss the options without sales pressure.