Is an inlay better than a filling?

It depends on the size and location of the cavity. For small to moderate cavities, a filling is a perfectly effective and more affordable treatment. For larger cavities — particularly on the biting surface of back teeth — an inlay is often stronger, longer-lasting, and provides a more precise fit than a direct filling. Your dentist will assess the tooth and recommend the most appropriate option.

Which lasts longer, a filling or an inlay?

Inlays generally last longer than fillings. A well-placed dental inlay can last 10–20 years, while a composite filling typically lasts 7–10 years. The longevity of both depends on oral hygiene, the location of the restoration, and habits such as teeth grinding.

Are inlays stronger than fillings?

Yes. Inlays are fabricated from hard-wearing materials such as porcelain or composite in a dental laboratory, making them more resistant to biting forces than direct fillings. This is particularly important for larger restorations on back teeth where strength and durability are essential.

When do you need an inlay instead of a filling?

An inlay is typically recommended when the cavity is too large for a standard filling to provide adequate support, but not severe enough to require a full crown. This often includes moderate to large cavities on the biting surface of premolars and molars. Your dentist will determine suitability based on the extent of damage.

What is the difference between an inlay and an onlay?

An inlay sits within the grooves of a tooth — between the cusps — and is used for cavities that do not extend over the biting edges. An onlay is larger, covering one or more cusps of the tooth. Both are custom-fabricated in a laboratory, but an onlay provides more coverage and structural reinforcement than an inlay.

How many appointments does an inlay require?

An inlay typically requires two appointments. At the first visit, the dentist prepares the tooth, removes any decay, and takes an impression. A temporary filling is placed while the inlay is fabricated in a dental laboratory. At the second visit, the custom inlay is fitted and bonded permanently to the tooth.

Can I replace a filling with an inlay?

Yes. If an existing filling is failing, worn, or if the cavity has enlarged over time, your dentist may recommend replacing it with an inlay for a stronger, longer-lasting restoration. This is particularly common when a large filling has weakened the surrounding tooth structure and a more robust solution is needed.

Fillings vs Inlays: Which Is Right for You?

Both white fillings for repairing cavities and minor tooth damage and dental inlays are used to restore teeth affected by decay — but they differ in strength, durability, and suitability depending on the size of the cavity.

Fillings are placed directly into the tooth during a single appointment and are ideal for small to moderate cavities. Inlays are custom-made in a dental laboratory and fitted over two visits, offering a stronger and longer-lasting solution for larger cavities — particularly on the biting surface of back teeth.

This guide explains the key differences to help you understand your options. The most suitable treatment will always depend on a clinical assessment by your dentist.

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Quick Comparison: Fillings vs Inlays

Feature	Dental Fillings	Dental Inlays
Purpose	Repair small to moderate cavities	Restore moderate to large cavities with precision
Coverage of Tooth	Fills the cavity directly	Custom-fitted piece placed within the tooth cusps
Strength	Moderate — suitable for small to medium cavities	High — reinforces weakened tooth structure
Durability	7–10 years for composite	10–20 years depending on material
Aesthetic Result	Good — tooth-coloured composite blends well	Excellent — custom shade-matched in a laboratory
Treatment Time	Single appointment (30–45 minutes)	2 appointments over 1–2 weeks
Cost (Per Tooth)	From £92.50 (member) / £185	From £497.50 (member) / £995
Longevity	7–10 years with care	10–20 years with care
Tooth Preparation	Minimal — decay removed and filled directly	Conservative — cavity shaped to receive custom piece
Best Suited For	Small to moderate cavities on any tooth	Moderate to large cavities where a filling may not be strong enough

Purpose

Filling

Repair small to moderate cavities

Inlay

Restore moderate to large cavities with precision

Coverage of Tooth

Filling

Fills the cavity directly

Inlay

Custom-fitted piece placed within the tooth cusps

Strength

Filling

Moderate — suitable for small to medium cavities

Inlay

High — reinforces weakened tooth structure

Durability

Filling

7–10 years for composite

Inlay

10–20 years depending on material

Aesthetic Result

Filling

Good — tooth-coloured composite blends well

Inlay

Excellent — custom shade-matched in a laboratory

Treatment Time

Filling

Single appointment (30–45 minutes)

Inlay

2 appointments over 1–2 weeks

Cost (Per Tooth)

Filling

From £92.50 (member) / £185

Inlay

From £497.50 (member) / £995

Longevity

Filling

7–10 years with care

Inlay

10–20 years with care

Tooth Preparation

Filling

Minimal — decay removed and filled directly

Inlay

Conservative — cavity shaped to receive custom piece

Best Suited For

Filling

Small to moderate cavities on any tooth

Inlay

Moderate to large cavities where a filling may not be strong enough

What Are Dental Fillings?

A dental filling is a restorative treatment used to repair a tooth that has been damaged by decay. The decayed portion of the tooth is removed, and the resulting cavity is filled directly with a durable material — most commonly a tooth-coloured composite resin — to restore the tooth's shape and function.

Fillings are one of the most common dental treatments available. A composite filling is placed directly into the cavity during a single appointment, shaped by hand, and hardened with a curing light. Treatment typically takes 30–45 minutes per tooth and is suitable for small to moderate cavities on any tooth.

Benefits

Completed in a single appointment with minimal preparation
Affordable and widely available treatment
White composite fillings blend naturally with teeth
Mercury-free alternative to traditional amalgam
Preserves more natural tooth structure than a crown
Effective for treating small to moderate cavities

Suitable Candidates

Dental fillings are appropriate for patients with small to moderate cavities where the remaining tooth structure is strong enough to support a direct restoration. They are the standard treatment for early to moderate decay and are suitable for both front and back teeth.

What Are Dental Inlays?

A dental inlay is a custom-made restoration fabricated in a dental laboratory and designed to fit precisely within the grooves of a tooth — between the cusps. Inlays are used to repair moderate to large cavities where a standard filling may not provide sufficient strength or durability.

The process typically requires two appointments. At the first visit, the dentist prepares the tooth and takes an impression, which is sent to a laboratory where the inlay is custom-fabricated from porcelain, composite resin, or gold. At the second visit, the inlay is bonded permanently into place. The result is a strong, precisely fitting restoration that reinforces the tooth.

Benefits

Stronger and more durable than direct fillings
Custom-made for a precise and accurate fit
Long-lasting — typically 10–20 years
Resistant to wear, staining, and shrinkage
Preserves more natural tooth than a crown
Natural appearance with laboratory shade-matching

Suitable Candidates

Dental inlays are recommended for patients with moderate to large cavities on the biting surface of back teeth, where a direct filling may not provide enough strength. They are particularly suitable when the cavity is too large for a filling but not severe enough to require a full dental crown.

Key Differences Between Fillings and Inlays

Direct vs Indirect Restoration

Fillings are placed directly into the tooth in a single visit. Inlays are custom-fabricated in a dental laboratory from an impression and require two appointments to complete.

Strength and Durability

Inlays are significantly stronger than direct fillings because they are made from hard-wearing materials in a laboratory. This makes them better suited for larger cavities under heavy biting forces.

Longevity

Composite fillings typically last 7–10 years. Dental inlays can last 10–20 years depending on the material. Inlays offer a longer-lasting solution for moderate to large restorations.

Precision of Fit

Inlays are custom-made to fit the exact shape of the prepared cavity, reducing the risk of gaps or recurrent decay. Fillings are moulded by hand and may be less precise for larger cavities.

Shrinkage

Composite fillings can shrink slightly as they harden, potentially creating micro-gaps between the filling and the tooth. Inlays are cured in a laboratory and do not shrink after placement.

Cost

Fillings start from £92.50 per tooth for members (£185 non-members). Inlays start from £497.50 (£995 non-members). Fillings are more affordable, while inlays offer greater durability for larger restorations.

Pros and Cons

Dental Fillings

Completed in a single appointment

More affordable than laboratory-made restorations

Minimal tooth preparation required

White composite fillings blend with natural teeth

Mercury-free alternative to traditional amalgam

Suitable for small to medium-sized cavities

Less durable than inlays for larger cavities (7–10 years)

May shrink slightly during curing, creating micro-gaps

Large fillings can weaken the remaining tooth structure

May discolour or wear over time

Not ideal for extensive damage to the biting surface

Dental Inlays

Stronger and more durable than direct fillings (10–20 years)

Custom-made in a dental laboratory for a precise fit

Preserves more natural tooth structure than a crown

Resistant to wear and staining

Natural appearance with precise shade-matching

Does not shrink — avoids micro-gap formation

Higher cost than a direct filling

Requires two appointments (impression and fitting)

Laboratory fabrication adds to treatment time

Not suitable for very small cavities where a filling suffices

May not be covered by all dental insurance plans

Cost Comparison

Costs depend on the size of the cavity, the material used, and individual clinical needs. Below are the prices at our South Kensington practice.

Treatment	Cost (Per Tooth)	Typical Lifespan
White Filling (Small)	From £92.50 (member) / £185	7–10 years
White Filling (Medium)	From £130 (member) / £260	7–10 years
White Filling (Large)	From £152.50 (member) / £305	7–10 years
Dental Inlay	From £497.50 (member) / £995	10–20 years

White Filling (Small)

Cost: From £92.50 / £185Lasts: 7–10 years

White Filling (Medium)

Cost: From £130 / £260Lasts: 7–10 years

White Filling (Large)

Cost: From £152.50 / £305Lasts: 7–10 years

Dental Inlay

Cost: From £497.50 / £995Lasts: 10–20 years

Membership patients receive 50% off treatment costs. Final pricing depends on the extent of treatment, the material selected, and your individual treatment plan.

Which Option Is Best for You?

Best for Small Cavities

For small to moderate cavities, a composite filling is the most efficient and affordable solution — completed in a single appointment with minimal preparation.

Dental Filling

Best for Larger Restorations

For moderate to large cavities on the biting surface of back teeth, an inlay offers greater strength, durability, and a more precise fit than a direct filling.

Dental Inlay

Best for Budget

If cost is a primary concern and the cavity is small to moderate in size, a composite filling is the more affordable option while still providing an effective restoration.

Dental Filling

Best for Long-Term Durability

If you want a longer-lasting restoration that minimises the risk of future replacement, a dental inlay typically lasts 10–20 years — significantly longer than a filling.

Dental Inlay