Tooth Fillings

What is a filling, and how do I know if I need one?

A filling restores a hole — a cavity — caused by decay, wear or a chip. It repairs and rehabilitates the tooth, restoring its form, function and structural integrity.

The more useful answer to “how do I know” is uncomfortable: most cavities start silently, without symptoms or pain. By the time a cavity hurts, it is usually well established. This is the entire reason for routine check-ups and x-rays — they find decay while it is still small and cheap to fix.

Smile Solutions is at Level 1, 220 Collins Street, Manchester Unity Building, Melbourne CBD.

What causes cavities

Tooth decay. Bacteria produce acid that dissolves tooth structure. Left untreated, decay can lead to pain, infection or abscesses.

Enamel wear. Wear and abrasion remove enamel and can cause tooth sensitivity.

Fractures. Trauma or a blow to the mouth can break teeth.

Cracks. Heavy biting or grinding creates crack lines that propagate over time.

Broken fillings. Existing fillings can break or fall out, exposing the tooth beneath.

How decay actually works

Decay is not a one-way process, and understanding why explains almost every piece of prevention advice you have ever been given.

The World Health Organization sets out the mechanism in one sentence: decay “results when plaque forms on the surface of a tooth and converts the free sugars … contained in foods and beverages into acids that destroy the tooth over time”. Free sugars, in the WHO's definition, means all sugars added to foods and beverages by the manufacturer, cook or consumer, plus sugars naturally present in honey, syrups and fruit juices — a wider category than most people assume, and one that includes fruit juice.

Every time you eat or drink something containing fermentable carbohydrate, the bacteria in plaque produce acid within minutes. Below a certain acidity the enamel begins to lose mineral. Once saliva has neutralised the acid and washed the sugar away — which takes roughly twenty to forty minutes — minerals from saliva and from fluoride flow back in and the enamel regains some of what it lost.

A cavity is what happens when that balance runs in the wrong direction for long enough. The WHO names the three conditions that let it: a continued high intake of free sugars, inadequate exposure to fluoride, and a lack of plaque removal by toothbrushing with fluoride toothpaste containing 1,000–1,500 ppm. All three are on your side of the chair.

Two consequences follow, and they are the practical part:

• Frequency matters more than quantity. A can of soft drink sipped over an afternoon does far more damage than the same can drunk in five minutes, because each sip restarts the acid clock. Six snacks a day means six demineralising episodes; the total sugar is almost beside the point.
• Saliva is the defence. Anything that reduces saliva — medications, dehydration, mouth breathing, some medical conditions — removes the repair half of the cycle and raises decay risk sharply, often in people whose brushing has not changed at all.

On how much sugar is too much, the WHO's recommendation is to limit free sugars to less than 10% of total energy intake, and ideally to less than 5%, which it says “minimizes the risk of dental caries throughout the life course”.

Where cavities form

Decay is not random. It starts where plaque sits undisturbed:

• The grooves on the biting surfaces of molars, which are often narrower than a toothbrush bristle. This is what fissure sealants are for — see the role of fissure sealants.
• Between the teeth, just below the point where two teeth touch. Invisible from any angle, undetectable by a probe, and the classic reason for routine x-rays.
• Around the edges of existing fillings and crowns. Decay starting at the margin of an old restoration is the single most common reason fillings get replaced — which is why every check-up examines the work you already have, not just the untouched teeth.
• On exposed root surfaces, where gums have receded. Root surface is softer than enamel and decays at a lower acidity, so it is a particular risk in older adults and anyone with dry mouth.

Six signs you may need a filling

This is not an exhaustive list, and their absence does not mean you have no cavities.

1. Visible holes or discolouration. Cavities you can see or feel with your tongue, or grey shadows and discolouration on the tooth surface.

2. Sensitivity. Discomfort from heat, cold or sweet foods.

3. Tooth pain. General toothache, or pain when biting and chewing.

4. Flossing issues. Floss tearing repeatedly in the same spot between two teeth — a reliable and often-ignored early sign.

5. Rough tooth surfaces. Teeth that feel uneven or gritty to the tongue.

6. X-ray signs. Hidden decay your dentist can identify on an x-ray, catching problems early and allowing treatment to be planned before symptoms appear.

If you notice any of these, book an appointment rather than waiting to see whether it worsens. These are reasons to be examined, not a diagnosis — the same symptoms can come from a crack, a failing old filling, gum recession or a tooth that needs root canal treatment rather than a filling. See Toothache & Tooth Pain and Chipped & Cracked Teeth.

How decay is found

• Looking, with good light and dry teeth. Early enamel decay appears as a chalky white patch before there is any hole at all.
• Gentle probing. Modern practice is deliberately light-handed: jabbing a sharp probe into an early lesion can break through a surface that would otherwise have remineralised.
• Bitewing radiographs, which show the areas between teeth and under existing fillings that no examination can see. How often they are taken depends on your decay risk rather than a fixed calendar — someone with no new decay in years needs them far less often than someone with active disease. On the exposure involved, the International Atomic Energy Agency gives the typical effective dose of an intraoral dental x-ray as 1–8 μSv, against 4–30 μSv for a panoramic examination; it also cautions that effective dose is a measure for comparing techniques rather than for estimating any individual's risk. See how safe are dental x-rays.
• Transillumination — shining light through the tooth, which shows some interproximal lesions and cracks.

Not every cavity needs a filling

This is worth knowing before anyone drills.

Early decay confined to enamel can sometimes be arrested or remineralised with high-fluoride products, diet change and better cleaning, then monitored over time. Drilling is irreversible: once a tooth is prepared, it is restored and re-restored for the rest of its life, each time a little larger.

It is entirely reasonable to ask “does this need filling now, or can we watch it?” — and to expect a clear answer about how deep the lesion is and what happens if you wait. Deep decay, decay through into dentine, and anything causing symptoms generally does need treating.

The corollary is that “watch and review” is a real treatment decision, not a deferral, and it only works if the reviews actually happen and something changes in the meantime. Monitoring a lesion while nothing else changes is just waiting for it to get bigger.

On the fluoride half of that: the National Health and Medical Research Council's 2016 review of the evidence found that water fluoridation reduces tooth decay by 26 to 44% in children and adolescents, and by about 27% in adults. That is the population-level effect of fluoride in water, not the effect of a fluoride varnish on one lesion — but it is the reason fluoride is the first lever pulled when a lesion is being watched rather than drilled.

Filling materials

Material choice depends on the tooth's position, how much structure remains, and how much load the restoration will carry.

Composite resin — tooth-coloured, placed directly in a single visit. Well suited to smaller cavities.

CEREC porcelain — designed and milled on site and fitted in the same appointment. Most commonly used to replace old, large amalgam or composite fillings that have failed, fractured or decayed. On molar teeth needing a larger restoration, porcelain is often the material of choice, and wear on it is similar to that on natural tooth. See Same-Day CEREC Restorations.

Where a cavity is too large for any filling to be predictable, a crown or onlay is the appropriate restoration rather than more filling material. Dental Crowns.

One caution about comparing materials by longevity. We searched our library of independent sources — regulators, professional bodies and peer-reviewed reviews — for survival data on chairside-milled ceramic restorations and on composite in posterior teeth, and found none. Any figure you are quoted for how long a particular filling material lasts, here or anywhere, is clinical experience rather than published evidence. That is not a reason to distrust it; it is a reason to ask what it is based on.

Direct and indirect restorations

There is evidence behind the bottom-left cell, though it comes from the cracked-tooth literature rather than from studies of fillings. The European Society of Endodontology's 2024 position statement reports that cracked teeth managed with direct bonded composite restorations may be more likely to require root canal treatment, or repair of a fractured restoration, than those managed with cuspal coverage. That applies to a tooth that is already cracked — not to every large filling — but it is the clearest published reason why a compromised tooth is sometimes better covered than filled. See Chipped & Cracked Teeth.

A note on amalgam

Silver amalgam fillings are still present in a great many Australian mouths, and they raise two separate questions.

Are they being phased out? Yes, gradually, and the main reasons are environmental — Australia is party to an international agreement to reduce mercury use — alongside the wide availability of tooth-coloured alternatives.

Should existing ones be removed? That is a different question. Australian dental authorities do not recommend removing sound, intact amalgam fillings purely on health grounds; removing a filling that is doing its job means drilling more tooth away for no clinical gain. Amalgams that are fractured, leaking, decayed underneath, or in a tooth that has cracked are a different matter and are replaced on their merits.

We should be straight about the evidence for both answers. Our library of independent sources contains no regulator or professional-body statement on amalgam removal, on mercury in dental restorations, or on the safety of composite resin. The two paragraphs above reflect the settled position as Australian clinicians understand and practise it, but we cannot point you at the document. If this matters to you — and for some people it genuinely does — ask your dentist to show you the current position of the Australian Dental Association and the Therapeutic Goods Administration rather than taking a practice website's word for it, including ours.

If you would prefer your existing restorations replaced for other reasons, that is a legitimate conversation to have with your dentist about sequence, cost and what each tooth actually needs. See Holistic Dentistry.

What happens at the appointment

A straightforward filling usually takes twenty minutes to an hour, depending on size and site.

1. Numbing, where it is needed. Small, shallow fillings are sometimes done without it — your choice, discussed first.
2. Isolating the tooth so it stays dry. Bonding fails in the presence of saliva, so this is not fussiness; it is the step that decides whether the restoration seals.
3. Removing the decay, and only the decay. The aim is to conserve as much sound tooth as possible.
4. Preparing the surface — etching and bonding, so composite adheres to enamel and dentine rather than merely sitting in the hole.
5. Placing the material in layers, each set with a curing light, and rebuilding the tooth's original contour — including the contact against the neighbouring tooth, which is what stops food packing afterwards.
6. Checking the bite with marking paper and adjusting until it feels like your own tooth, then polishing.

Say something if the bite feels high before you leave. It is a thirty-second adjustment at the time and a fortnight of soreness if it is left.

If the appointment itself is the obstacle, say so when booking rather than not booking. See Dental Anxiety.

Afterwards

• Composite is set hard immediately — you can eat as soon as any anaesthetic has worn off.
• Wait until the numbness has gone before eating. Biting or scalding a numb lip, cheek or tongue is the most common post-filling injury, particularly in children.
• Sensitivity to cold for a few weeks is common after a deeper filling and usually settles.
• Come back if pain lingers more than about thirty seconds after something cold, if it wakes you at night, if biting on it hurts, or if the sensitivity is getting worse rather than better.

What to expect, and what can go wrong

Most fillings are straightforward. The things that do happen are worth hearing in advance:

• Sensitivity to cold or to biting for a few weeks afterwards is common, particularly with deeper fillings, and usually settles.
• A filling that feels high when you bite needs a quick adjustment. Do not live with it.
• Deep decay close to the nerve can mean the tooth needs root canal treatment later, even though the filling was done correctly. Your dentist should tell you before treatment if your tooth is in that category. Root Canal.
• Fillings do not last forever. They chip, wear, and eventually leak at the margins, and decay can start again underneath. Lifespan depends on size, site, material, your bite and your home care, so the figures quoted anywhere are ranges rather than promises.
• The tooth can fracture around a large restoration, which is why very large fillings are sometimes the wrong answer. The European Society of Endodontology names an extensively restored tooth, and the last standing molar or premolar, among the sites where a crack warrants active treatment rather than watching — which is the same point from the other direction.

What it costs

Cost depends on the site and size of the filling, and can only be quoted once your dentist has examined the tooth. Broadly, the fee rises with the number of tooth surfaces involved — a single-surface filling is the simplest case, and a restoration wrapping three or more surfaces is a considerably larger piece of work.

For context on how dental fees move, the Australian Dental Association's Dental Fees Survey 2022 — 3,535 general practitioners, 122 items, as at 1 July 2022 — found fees charged by general dentists had risen 3.7% over the two years since 1 July 2020, with the smallest increases in preventive services and periodontics (1.6%) and the largest in orthodontics (6.9%). It also records considerable variation in the fees charged within and between states, which is why a single national figure for a filling does not exist.

When comparing, consider longevity alongside the fee. Over the long run, one porcelain restoration can work out less expensive than replacing a composite resin filling on the same tooth several times — though that depends on how long each lasts in your mouth, which nobody can know in advance, and as noted above there is no published survival data to settle it. Price Guide.

Smile Solutions is a Bupa Members First Platinum provider; eligibility, limits and waiting periods are set by your fund. Payment plans are available through Payright for treatment from $150 to $20,000, over 3 to 30 months. Other finance options may also be available; provider eligibility, fees and terms can change. Where a plan is advertised as interest free, that describes the plan term only — a deposit may be required, an establishment fee and ongoing account fees may apply, and charges can apply if the balance is not cleared within the agreed period. The applicable terms depend on the provider and the amount financed, and are set out in writing before you commit — ask what the deposit and the establishment fee are, in dollars, and what the total will be by the end. Payment Plans.

Preventing them in the first place

To reduce the chance of decay:

• Maintain regular dental check-ups — this is how silent cavities are caught
• Brush twice daily with fluoride toothpaste. The WHO specifies 1,000–1,500 ppm fluoride as the working concentration, so it is worth checking the tube rather than assuming
• Spit, do not rinse after brushing. Rinsing washes away the fluoride that was about to do the work
• Clean between the teeth daily; the surfaces between teeth are where floss-tearing cavities form
• Keep regular professional cleans with a hygienist — see Dental Cleans & Hygienists
• Limit the frequency of sugar and acid exposure, not just the quantity — for the reason set out above, and with the WHO's free sugars definition in mind, which counts fruit juice and honey
• Raise dry mouth with your dentist if you have it; higher-fluoride products are often appropriate

If there are children in the house, the scale of the problem is worth knowing. The Australian Dental Association reports that 34% of Australian children aged 5–6 have experienced decay in their primary teeth, and 27% of those aged 5–10 have untreated decay in them. Fillings in adult mouths are very often the continuation of something that started long before. See Children's Dentistry.

Common questions

Does every early cavity need a filling?

No. A lesion confined to enamel may sometimes be monitored and managed by improving fluoride exposure, cleaning and diet. Once decay has progressed into dentine or created a cavity that cannot be cleaned, a restoration is more likely to be needed.

How does the dentist know how deep the decay is?

The decision uses the clinical examination, symptoms and often radiographs. The true depth can sometimes become clearer only after weakened material is removed. Ask whether the decay is limited to enamel, extends into dentine or is close to the nerve.

Which filling material is best?

It depends on the tooth, size and position of the cavity, bite forces, moisture control, appearance and remaining tooth structure. Direct composite and indirect ceramic restorations have different indications; the most conservative predictable option should be explained.

What nobody can give you is a survival figure to choose between them. Our library of independent sources holds no published survival data for chairside-milled ceramic or for posterior composite, so any comparison of how long each lasts is experience rather than evidence. Ask instead which option removes the least sound tooth while still being predictable for your cavity.

Will the tooth hurt after a filling?

Temporary sensitivity to cold, pressure or biting can occur, especially after a deep restoration. Contact the practice if pain is severe, worsening, wakes you, lingers after temperature changes or the bite feels high.

How long does a filling last?

No filling is permanent. Size, material, bonding conditions, bite forces, grinding, decay risk and home care all affect longevity. Larger restorations generally place the remaining tooth under more stress and may eventually require an onlay or crown.

What determines the price?

Fees commonly reflect the number of tooth surfaces restored, material and complexity. Ask for the item number, material, number of surfaces and whether any additional protective restoration may be needed. The ADA's 2022 fees survey found considerable variation within and between states, so a quote that differs from one you were given elsewhere is not in itself evidence that either is wrong.

Should an old amalgam filling be replaced just because it is amalgam?

Not necessarily. Replacement removes more tooth structure and should have a clinical reason, such as decay, fracture, leakage, symptoms or a restorative plan. Ask what problem has been identified and what happens if the filling is monitored.

And be aware of what this page cannot tell you. We hold no independent regulator or professional-body statement on amalgam safety or removal, so we are not in a position to cite anybody on it. If the question matters to you, ask to be shown the current Australian Dental Association and Therapeutic Goods Administration positions directly.

Who performs the treatment

At Smile Solutions, fillings are placed by the practice's general dentists. Registration can be verified free on the AHPRA public register at ahpra.gov.au.

Related pages: General Dentistry, Toothache & Tooth Pain, Root Canal, Chipped & Cracked Teeth, Same-Day CEREC Restorations, Dental Crowns, Dental Cleans & Hygienists, Children's Dentistry.

Practical details

General information only — it is not a diagnosis, a treatment plan, a quote or a promise of any particular clinical outcome, and it does not replace advice from your treating practitioner. Whether a tooth needs filling, which material suits it and how long the restoration lasts vary between individuals and can only be established by examination and, usually, radiographs. No filling is permanent, and no published survival data for these materials is cited here because we hold none — statements about longevity are clinical experience. Figures quoted are attributed to the bodies named alongside them. Fees are indicative and subject to change; confirm at your consultation. Health fund and payment plan terms are set by the relevant fund or credit provider and change; confirm current terms directly before you commit.

Smile Solutions trades under ABN 28 193 514 103.