What the choice of restoration really depends on
- What decides the solution is not the name of the material, but how many of the tooth’s own walls have survived decay and earlier treatment.
- There is no evidence that, for the same cavity, a composite inlay made outside the mouth will last longer than composite placed in the chair.
- All three solutions are described here for cavities of various sizes; a separate decision is the boundary beyond which an overlay, that is a restoration covering the whole chewing surface, stops being enough - it is described in the article on what overlays and onlays are.
- A composite filling is placed in the mouth during a single appointment and works well for cavities involving one or two surfaces.
- A ceramic inlay is made outside the patient’s mouth and comes in where the cavity is wide and the cusps need covering.
- A crown encircles the tooth and costs the most sound tissue, so it is sometimes the last solution rather than the first.
How much sound tooth remains - the right criterion
Patients usually ask about the material. The dentist’s first question is a different one: how much of the tooth is still standing. A molar works like a vault resting on walls. Cusps are the raised points of the chewing surface where the tooth meets its opposing tooth; the surfaces are the tooth’s four sides plus its top. The dentist counts how many of them decay has taken - and each one taken removes a piece of the vault. The tooth weakens faster than the hole itself grows. A cavity on two surfaces and a cavity on three do not differ by one third. They differ in whether the cusp still has anything to rest on.
The data show this. In a retrospective analysis of 900 composite restorations in posterior teeth in 479 patients, cavities reaching three surfaces or more failed more often than smaller ones, and the difference was statistically significant. So the direction in which the number of surfaces works is known. By how much is not. The restorations were placed by students at a university clinic. These figures therefore describe something closer to the lower bound of what can be achieved, and they do not transfer directly to a practice where an experienced dentist works under magnification, with the tooth isolated from saliva by a rubber sheet - the rubber dam. The direction stays the same: as the cavity extends, what grows is not so much the risk carried by the material as the risk carried by the tooth itself.
The same material can therefore be the right call in one tooth and a risky one in the tooth next to it. The disease itself has its own scale as well, described in the article on what the successive stages of tooth decay look like.
The composite filling: where it makes sense
Composite is a resin with fine particles of glass or ceramic, which hardens under a curing light and is bonded to enamel and dentine. The dentist builds such a tooth filling up in layers directly in the cavity, during a single appointment. No sound tissue has to be cut away to make room for laboratory work to seat. Its natural territory is cavities on one or two surfaces, with the cusps intact and the walls of reasonable thickness; there a composite filling restores the shape of the tooth, its colour and the contact point with the neighbouring tooth, and once damaged it can be repaired without replacing the whole. How long a composite filling lasts was measured in the same analysis of 900 restorations: 78% were still serviceable after at least five years. About 2% of restorations failed per year. The caveat about student placement applies here too.
One more thing changes the conversation about the brand of material: a review by the American Dental Association gathered 38 trials with random allocation to groups and compared materials placed straight into the cavity, in primary and permanent teeth: composites, amalgam, glass ionomer cements and compomers. The data are not sufficient to identify differences between them that matter to the patient, and the authors rated the certainty of the evidence from moderate to very low. What decides is case selection and workmanship. The name on the package does not decide. The scope of the procedure is described on the page about how we carry out fillings and tooth restoration.
The ceramic inlay: what it gives in return for the tissue removed
Three names describe the same idea in versions that differ in how far they reach:
- inlay: a restoration lying inside the outline of the cusps, without covering them;
- onlay: a restoration that additionally covers at least one cusp;
- overlay: a restoration covering the whole chewing surface.
Work of this kind is designed and made outside the patient’s mouth, from ceramic or a hybrid material, and then bonded into the cavity. The gain is mainly mechanical: the shape of the chewing surface and the contact point are created under controlled conditions, away from the field where saliva gets in the way.
In a series of 556 restorations made from lithium disilicate, a strong glass ceramic, in 304 patients, survival after ten years was 95.6%, and the risk of failure was estimated at 0.3% per year. The split within the series is more interesting: inlays did worse than onlays, and all the failures occurred in molars. Covering the cusp may have helped the tooth, though it cost some tissue. Who received an onlay was decided by the clinical indication. Nobody randomised it.
The shorter horizon looks more modest. In a review of six trials with random allocation, the estimated three-year survival of partial coverage restorations was 93.7% for lithium disilicate and 89.3% for hybrid ceramics. These two numbers do not contradict each other, because they do not come from the same world: the 95.6% came from a single private practice and from patients who themselves chose ceramic. The 93.7% is a pooled estimate from 119 restorations followed for one to three years, with a confidence interval from 83.7% to 97.7%. The long-term durability of these restorations remains uncertain. A promise of twenty years of service has limited support in the literature today.
When a tooth needs a crown
A crown encircles the tooth and spreads the load over its whole body. The indication is sometimes a situation in which there are no walls left to cover: extensive loss of tissue, a crack running through a cusp, a tooth after root canal treatment with a destroyed clinical crown, that is the part visible in the mouth.
The price is paid in tissue. Preparing a tooth for a crown removes a layer all the way around, including where the tissue was sound. Enamel once removed cannot be restored by anyone.
Even after root canal treatment it is worth asking about something smaller than a crown. In a review of eleven studies of restorations made from hybrid materials in root-treated teeth, partial coverage restorations failed less often than endocrowns, that is crowns made in one piece with a part reaching into the pulp chamber. That is not the same as a crown prepared all the way around the tooth, and this review did not cover that comparison. Across the whole group, survival was 90.2% at three years and 84.2% at five. Most often the restoration debonded, that is it failed in a way that is usually reversible. When a crown after root canal treatment is necessary is described in a separate article.
How much tooth is left and which restoration: the situations side by side
The question of which filling to choose - a filling or an inlay - is answered in this table by the left column, not the right one.
| How much tooth is left | Typical solution | What the data say (different studies, do not compare the numbers between rows) | What you pay with |
|---|---|---|---|
| Cavity on one or two surfaces, cusps and walls intact | Composite filling, one appointment | Restorations up to two surfaces fail less often than those involving three or more | The least tissue removed; over time the margin discolours and the surface wears |
| Three-surface cavity, thin walls, undermined cusps, that is cusps with no support from beneath | Onlay or overlay, less often an extensive composite filling | Partial coverage restorations from lithium disilicate: 93.7% at three years; long-term durability uncertain | Two appointments, laboratory work, some tissue given up to the shape of the inlay |
| One or more cusps missing, the tooth still has walls of its own | Overlay covering the chewing surface | In ten-year follow-up onlays did better than inlays | Covering the cusps costs tissue, but it relieves the walls |
| Clinical crown destroyed, crack through a cusp, tooth after root canal treatment with major loss | Crown | A proven solution; where the walls remain, a partial coverage restoration can be no worse than an endocrown | The largest and irreversible loss of sound tissue |
The choice is decided by the thickness of the walls and by the condition of the pulp.
Will a laboratory-made inlay last longer than a composite filling
A composite filling has some drawbacks. Over time the bond to dentine weakens, the margin of the restoration darkens, and the chewing surface wears faster than ceramic. In cavities reaching below the gum there is an entirely ordinary obstacle: without a dry field, bonding fails, and moisture in such a place sometimes cannot be brought under control. From the perspective of the clinical team at Modern Dental & Orthodontics (Klinika MDO), what matters is that the decisive factor here is not the material but access: a margin running below the gum can change the prognosis of the same restoration more than swapping composite for ceramic. The second condition, which a patient cannot see in themselves, is the occlusion, that is the way the teeth meet when the jaws close. In someone who clenches their teeth or grinds them at night, the same restoration in the same tooth has a different prognosis.
There is, however, a place in this picture where intuition parts ways with the data.
It seems obvious that in a large cavity laboratory work will last longer than composite built up in the mouth. A synthesis of five trials with random allocation, covering 627 restorations in posterior teeth, including extensive cavities with cusp coverage, showed the opposite: the risk of failure was about 40% lower for restorations placed straight into the tooth. What was compared there was direct composite against composite made outside the patient’s mouth. The authors themselves temper this result, because they rated the certainty of the evidence as very low and judged all the included trials to be at high risk of bias. The honest conclusion is therefore this: we have no evidence that, for the same cavity, laboratory work lasts longer than composite. For composite inlays this was tested directly and came out the other way round; for ceramic, these studies contain no such comparison.
One thing we do know for certain.
A composite filling takes away less of the tooth.
What else decides how long a restoration lasts
The material is one of many factors, and not the most important one. In an analysis of data from four clinical trials, covering 618 restorations in teeth after root canal treatment followed for up to seventeen years, what said most about whether the restoration stayed in the tooth at all was the patient’s age and whether the tooth was a molar. What said most about whether it survived without any repair along the way was the dentist’s experience. In these data, however, “experienced” means a dentist in private practice and “inexperienced” means a student, and the split coincides with a split between countries. The two measures are not the same: the first counts as a success a restoration that came off and was bonded back on, the second does not. These were predictive models, not an experiment; they describe associations, not causes. The dentist’s experience is, moreover, the only factor on this list that the patient decides on. To this add caries risk and hygiene: in a survey of more than three thousand dentists from twenty-one countries, it was high caries risk that most often tipped the scales from repair towards replacing the whole restoration. A composite filling placed in such a mouth usually lasts a shorter time than the same filling in someone with no active disease, even though the material and the technique are the same. The survey itself did not measure this: it asked about dentists’ decisions, not about what became of the restorations.
That leaves repair. A damaged restoration can often be repaired instead of being replaced whole, and every replacement enlarges the cavity by another piece of sound tissue. In the same survey, dentists most often repaired a fractured composite, while decay at the margin and a leaking margin were treated by replacing the whole restoration. The survey describes, however, what dentists say they do. Whether it works out well for patients is something it did not check.
Frequently asked questions
How long does a composite filling last?
In an analysis of 900 restorations in posterior teeth, 78% were still serviceable after at least five years. About 2% of restorations failed per year (a result from a university clinic, so a conservative one). One- and two-surface restorations did better in that analysis than those involving three surfaces or more. The state of the mouth counts as well: where caries risk is high, the fate of a restoration is more often decided by its margin than by the strength of the material.
Do old amalgam fillings have to be replaced?
The age of a restoration alone is not an indication for replacement. A well-sealed amalgam tooth filling may go on working; what justifies replacement is leakage, decay at the margin, a cracked tooth or a fracture of the filling itself. Replacement always enlarges the cavity, because sound tissue at the border is removed along with it. The decision is made on the basis of the examination and the radiograph, not on the basis of the restoration’s age.
Is a ceramic inlay worth the difference in price?
It depends on the size of the cavity. The price of the work is not the criterion here. For small cavities there are no studies confirming an advantage of ceramic over composite: a higher price does not buy evidence of longer service here, and the composite filling remains the tissue-sparing choice. For wide cavities with undermined cusps, a partial coverage restoration gives a shape made outside the mouth and coverage of the cusp, which relieves the walls of the tooth.
Why does the margin of a filling darken over time?
Discolouration of the margin is usually dietary pigment deposited in the microgap between the material and the enamel. In itself it does not mean decay and is not an indication for replacement. It becomes a concern when it is accompanied by the explorer catching, a break in the continuity of the margin, or a shadow visible on the radiograph.
How many appointments does a ceramic inlay take?
Usually two. The first is preparation of the cavity, an impression or scan and a temporary restoration; the second is the try-in and the bonding of the finished work. In practices working with a chairside milling unit it is sometimes a single longer appointment. The number of appointments depends on the technology used to make the restoration, not on how long the restoration itself lasts.
Can a tooth be restored without a crown after root canal treatment?
This is sometimes possible when the walls of the tooth have survived. In a review of studies of restorations made from hybrid materials, partial coverage restorations failed less often than endocrowns, that is crowns made in one piece with a part reaching into the pulp chamber. No comparison was made with a crown prepared all the way around the tooth. What decides eligibility is the amount of remaining tissue and the distribution of occlusal forces. Having had root canal treatment alone does not settle the question of a crown.
What does the cost of restoring a tooth depend on?
On the scope of the work, not on the name of the material. The cost is made up of: the number of surfaces involved in the cavity, whether the restoration is built straight in the tooth or in a laboratory, the number of appointments, the technology used to make the inlay, and whether the tooth required root canal treatment. That is why two restorations recorded under the same word in the notes may call for a different amount of work. The scope of treatment is established after the examination and the radiograph.
Can a composite filling hurt after it is placed?
Sensitivity to cold and to biting for a few days after the procedure is common and usually resolves on its own. What is worrying is pain that arises spontaneously, wakes you at night, builds from week to week, or lasts longer than half a minute after the stimulus. Do not wait for a follow-up appointment in that case - contact the practice. A swollen cheek or a fever is a reason to be seen the same day.
How do I know whether I am being offered more than I need?
Ask directly about the criterion rather than about the material: how many walls of my tooth are sound, whether the cusps are undermined, and whether this restoration can be done at a smaller cost in tissue. The answer should refer to the condition of the tooth and to the radiograph. The name of the material alone is not an answer.
How much tooth will be left after this restoration
The three solutions in the title do not form a ladder on which higher means longer-lasting. They form a scale of extent: the less tooth is left, the further the restoration has to reach and the more sound tissue the patient loses along the way.
The question worth asking before the procedure is therefore a different one from the question about the material. How much of my tooth will be left after this restoration? And what happens when it has to be replaced ten years from now?
Read more:
- Aesthetic and Restorative Dentistry in Warsaw
- Overlay and Onlay — When Instead of a Crown, When Instead of a Filling?
- Tooth decay stages: when can it be stopped without drilling
- A crown on a tooth after root canal treatment - when it is necessary
- Zirconia, all-ceramic or metal-based crown? A comparison of modern prosthetic solutions
Content and liability disclaimer
This article is informational and educational in nature and does not constitute medical advice, a diagnosis or a therapeutic recommendation — it does not replace a consultation with a specialist. If you are experiencing symptoms, have doubts or are facing a decision about treatment, consult a dentist. The methods described and the data cited are general in nature. The results of scientific studies relate to populations, not to an individual patient. The course and outcome of therapy depend on the individual clinical situation and may vary between patients. No information contained in this article constitutes a guarantee of result. The content has been prepared with due care, based on publicly available medical knowledge and the scientific publications indicated in the Sources section. We do not advise taking or refraining from any health-related action solely on the basis of the content of this article, without prior consultation with a doctor.
Sources
Source 1
Links https://doi.org/10.1007/s00784-024-05631-4 │ https://pubmed.ncbi.nlm.nih.gov/38630376/
Description Alonso ALL, Tirapelli C, Cruvinel PB, i wsp. „Longevity of composite restorations in posterior teeth placed by dental students: a 12-year retrospective study.” Clin Oral Investig. 2024;28(5):253.
Source 2
Links https://doi.org/10.1016/j.dental.2024.07.033 │ https://pubmed.ncbi.nlm.nih.gov/39122602/
Description Tennert C, Maliakal C, Suarèz Machado L, i wsp. „Longevity of posterior direct versus indirect composite restorations: A systematic review and meta-analysis.” Dent Mater. 2024;40(11):e95-e101.
Source 3
Links https://doi.org/10.1111/jerd.13353 │ https://pubmed.ncbi.nlm.nih.gov/39558793/
Description Prott LS, Pieralli S, Klein P, i wsp. „Survival and Complications of Partial Coverage Restorations on Posterior Teeth – A Systematic Review and Meta-Analysis.” J Esthet Restor Dent. 2025;37(3):620-641.
Source 4
Links https://doi.org/10.1016/j.prosdent.2020.07.015 │ https://pubmed.ncbi.nlm.nih.gov/33012530/
Description Malament KA, Margvelashvili-Malament M, Natto ZS, i wsp. „10.9-year survival of pressed acid etched monolithic e.max lithium disilicate glass-ceramic partial coverage restorations: Performance and outcomes as a function of tooth position, age, sex, and the type of partial coverage restoration (inlay or onlay).” J Prosthet Dent. 2021;126(4):523-532.
Source 5
Links https://doi.org/10.1016/j.prosdent.2025.01.019 │ https://pubmed.ncbi.nlm.nih.gov/39922746/
Description Yuen JJX, Saw ZK, Chua HS, Beh YH. „Clinical behavior and survival of CAD-CAM resin nanoceramic and polymer interpenetrating ceramic network material restorations on endodontically treated teeth: A systematic review and meta-analysis.” J Prosthet Dent. 2025;133(6):1437.e1-1437.e9.
Source 6
Links https://doi.org/10.1016/j.adaj.2022.09.012 │ https://pubmed.ncbi.nlm.nih.gov/36610925/
Description Pilcher L, Pahlke S, Urquhart O, i wsp. „Direct materials for restoring caries lesions: Systematic review and meta-analysis – a report of the American Dental Association Council on Scientific Affairs.” J Am Dent Assoc. 2023;154(2):e1-e98.
Source 7
Links https://doi.org/10.1111/jerd.13321 │ https://pubmed.ncbi.nlm.nih.gov/39487728/
Description Hatipoğlu Ö, Martins JFB, Karobari MI, i wsp. „Clinical Decision-Making of Repair vs. Replacement of Defective Direct Dental Restorations: A Multinational Cross-Sectional Study With Meta-Analysis.” J Esthet Restor Dent. 2025;37(4):977-991.
Source 8
Links https://doi.org/10.1111/iej.70048 │ https://pubmed.ncbi.nlm.nih.gov/41094683/
Description Chisini LA, Cenci MS, Skupien JA, i wsp. „Restoration’s Longevity in Endodontically Treated Teeth: A Machine Learning Survival Analysis From Randomised Clinical Trials.” Int Endod J. 2026;59(2):251-261.