Inlays and Onlays: Durable Tooth Restoration Solution

In the world of dental care, when a tooth is damaged by decay or a fracture, the go-to solution for many years was a simple filling. While modern fillings are fantastic for smaller issues, sometimes the damage is just too extensive. It’s a bit like a hole in your favourite jumper—a small tear can be patched quickly, but a larger rip needs a more robust, custom-tailored fix.

This is where Inlays and Onlays come into their own. These restorations are often called ‘partial crowns’ because they bridge the gap between a standard filling and a full crown. They offer a strong, precise, and durable alternative, preserving more of your natural tooth structure than a full crown would. For many Australians looking for a long-lasting and aesthetically pleasing way to repair a damaged back tooth, an Inlay or Onlay is the gold standard.

If you’ve been told you need more than a filling, or if you’re concerned about the long-term strength of a heavily restored tooth, keep reading. We’ll break down exactly what these incredible dental solutions are, why they are so durable, what the procedure involves, and how they stack up against other options.

What Are Inlays and Onlays?

The simplest way to understand Inlays and Onlays is to know that they are custom-made, laboratory-crafted restorations. Unlike a traditional filling, which a dentist places and shapes directly into your tooth cavity in one visit, inlays and onlays are made outside of your mouth—usually in a dental laboratory—to perfectly match the precise contours of your tooth. This ‘indirect’ method of restoration is what gives them their superior fit, strength, and durability.

The material—often a highly durable ceramic or porcelain—is moulded and fired under high heat and pressure, resulting in a restoration that is far stronger and more resistant to chewing forces than a direct filling. Once ready, your dentist will bond this custom-made piece permanently onto your prepared tooth.

Dental Inlays and Dental Onlays are very similar and are grouped together, but they cover slightly different areas of the tooth:

• Inlay: An Inlay sits inside the cusp tips (the raised points) of your chewing surface. Think of it as restoring the central grooves and pits of the tooth, like a puzzle piece that fits neatly within the boundaries. They are used when the decay is moderate and contained within the central chewing surface.
• Onlay: An Onlay is a more extensive restoration. It not only fills the central area but also sits on or over one or more of the cusps. This makes an Onlay a stronger choice when the decay or fracture has weakened a cusp, requiring it to be covered and protected to prevent the tooth from cracking under bite pressure.

Both options are a testament to conservative dentistry—they restore function and beauty while keeping as much of your healthy, natural tooth as possible.

Differences Between Inlays, Onlays, and Fillings

One of the most common questions people ask their dentist is, “Why can’t I just get a regular filling?” It comes down to the extent of the damage, the required strength, and the longevity of the repair.

1. The Traditional Dental Filling

The traditional filling—whether it’s the modern, tooth-coloured composite resin or the older, silver amalgam—is a direct restoration.

• Process: The material is applied directly into the prepared cavity and then hardened (cured) by the dentist during a single appointment.
• Best for: Small to medium-sized cavities.
• Pros: Quick, cost-effective, and minimal tooth preparation needed.
• Cons: The composite material can shrink slightly as it hardens, which can sometimes create microscopic gaps at the edges over time. It is also not strong enough to restore large areas or to cover cusps, and a very large filling can actually weaken the remaining tooth structure, making it prone to fracture.

2. Dental Inlays and Dental Onlays (The ‘Partial Crown’)

Inlays and Onlays are indirect restorations, which means they are fabricated outside the mouth. They are made from a solid piece of porcelain, composite, or gold, ensuring maximum strength and a precise fit.

Feature	Dental Filling (Direct Restoration)	Dental Inlay/Onlay (Indirect Restoration)
Fabrication	Made directly in the mouth during one visit.	Custom-made in a dental lab (or in-office machine).
Material Strength	Resin is strong, but susceptible to wear and tear over time, especially in large cavities.	Porcelain/Gold is highly durable, superior strength, and minimal wear.
Coverage	Only fills the hole (sits inside the cusps).	Inlay sits within the cusps; Onlay covers and protects one or more cusps.
Longevity	Generally 5-15 years.	Generally 10-30 years, often much longer.
Tooth Preservation	Good for small cavities.	Excellent for large cavities—saves more natural tooth than a full crown.

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3. Inlays vs Fillings: The Strength Factor

When a cavity is extensive, removing the decay leaves a significant gap. If a dentist uses a large filling, the force from chewing on that tooth can cause the remaining walls of the tooth to flex or split. This leads to fractures, which can often be catastrophic, sometimes resulting in the need for a root canal or even extraction.

Because an Inlay or Onlay is a single, solid piece of porcelain (or gold) that is bonded to the tooth, it acts like a structural brace, holding the remaining tooth together. The bonding process is incredibly strong, increasing the tooth’s resistance to fractures by up to 75%. This is the critical reason why dentists recommend them—they restore the strength of the tooth, not just fill a hole.

When Are Inlays and Onlays Recommended?

Choosing the right type of Tooth Restoration is crucial for the long-term health and function of your smile. Your dentist won’t recommend an Inlay or Onlay unless there is a specific clinical reason that makes it the superior choice over a standard filling or a crown.

Here are the key situations where Inlays and Onlays are the preferred treatment:

• Cavities Too Large for a Filling: If the decay is so extensive that a conventional filling would undermine the strength of the remaining tooth structure, an Inlay or Onlay provides the necessary structural support to handle heavy chewing forces.
• Cracked Tooth Syndrome: Sometimes, a tooth develops small, micro-fractures (cracks) that cause pain, especially when biting down. If these cracks are not severe enough for a full crown, an Onlay can be the perfect solution. By covering and holding the cracked cusps together, the Onlay effectively splints the tooth, stopping the movement and relieving the pain.
• Replacement of Large or Faulty Amalgam Fillings: If you have an old, large metal filling that is failing—perhaps it’s leaking, has recurrent decay underneath, or has caused a crack in the tooth—an Onlay is ideal. It allows the dentist to remove the failing filling and any further decay while using the Onlay to reinforce the tooth’s new structural integrity, all while offering a beautiful, tooth-coloured appearance.
• Cosmetic Restoration of Back Teeth: While they are primarily a restorative solution, inlays and onlays offer exceptional aesthetics. For teeth that are visible when you laugh or talk, a porcelain restoration can be colour-matched to your natural tooth, resulting in an almost invisible repair that preserves your smile’s natural look.

The decision is always about being conservative. If a crown requires the dentist to file down the entire tooth, and a filling is not strong enough, the Inlay or Onlay is the smart, durable middle ground that saves the most natural tooth structure.

Benefits of Inlays and Onlays

The advantages of choosing these indirect restorations extend well beyond simply filling a hole. They are an investment in the long-term health and stability of your teeth.

1. Superior Durability and Longevity

As mentioned, inlays and onlays are laboratory-created. They are fabricated from strong materials like porcelain or gold under controlled conditions, making them far denser and more durable than chairside composite fillings. This extreme durability means they can withstand the constant, heavy forces of chewing for much longer—often 10 to 30 years, and sometimes even more with excellent oral hygiene.

2. Maximum Tooth Preservation

This is one of the most significant benefits. Dental Inlays and Dental Onlays are considered a highly conservative treatment.

• Filling vs. Onlay: A filling only fills the hole.
• Onlay vs. Crown: A crown requires the dentist to reshape the entire tooth structure to accommodate a cap that fits over it.

The Onlay only covers the damaged areas and the weakened cusps, leaving the healthy parts of the tooth intact. By retaining more natural tooth structure, the tooth is less likely to need more complex and costly treatments, like a full crown, in the future.

3. Precise Fit and Protection Against Decay

Because the restoration is custom-made from a precise mould (impression) of your tooth, the fit is absolutely perfect. This precise fit ensures that the margins (the junction where the restoration meets the tooth) are seamless. A tighter seal is crucial for preventing what dentists call ‘microleakage’—the seepage of bacteria and food debris under the restoration—which is the main cause of recurrent decay. The tight seal provided by a custom-made Inlay or Onlay drastically reduces the risk of further decay.

4. Exceptional Aesthetics

Modern dentistry is all about blending function and appearance. Porcelain and ceramic inlays and onlays are made to match the natural shade and sheen of your existing tooth perfectly. They won’t discolour or stain over time, unlike some composite fillings, which can absorb pigments from coffee or red wine. The final result is a beautiful, virtually undetectable restoration that restores the function and aesthetics of your smile.

The Procedure for Getting Inlays and Onlays

Getting a dental Inlay or Onlay typically involves two separate appointments, as they are custom-made in a laboratory. However, some advanced dental practices (like your local dentist Kensington) use CAD/CAM technology (such as CEREC) to complete the entire procedure in a single, extended visit.

Appointment 1: Preparation and Impression

The first visit is focused on preparing the tooth and taking a precise mould for the laboratory.

1. Anaesthetic and Preparation: The dentist will begin by numbing the area with a local anaesthetic to ensure you are comfortable. They will then carefully remove all the decay, old filling material, and any compromised tooth structure, shaping the cavity to receive the final restoration.
2. Taking the Impression (Mould): Once the tooth is prepared, the dentist will take a highly accurate impression of the prepared tooth. This can be done using a putty-like material or, increasingly, with a digital scanner. This impression (or 3D scan) is then sent to a skilled dental laboratory, where the specialised technician will custom-craft your Inlay or Onlay to exact specifications.
3. Temporary Restoration: While your permanent restoration is being made (which usually takes 1-2 weeks), the dentist will place a temporary filling or cover over the prepared tooth. This protects the tooth from sensitivity, bacteria, and any damage until your next appointment.

Appointment 2: Fitting and Bonding

The second visit is where the magic happens and your new, durable restoration is permanently placed.

1. Removal of Temporary and Cleaning: The temporary restoration is gently removed, and the tooth is thoroughly cleaned to ensure a perfect, sterile bonding surface.
2. Trial Fit and Adjustment: Your dentist will carefully place the custom-made Inlay or Onlay into the cavity and check its fit. They will assess the contact points with adjacent teeth and ensure your bite is perfectly aligned. Minor adjustments may be made to the restoration to ensure a seamless and comfortable fit.
3. Permanent Bonding: The tooth is etched and prepared, and a high-strength dental resin cement is used to permanently bond the restoration to the tooth structure. A special light is used to cure and harden the cement, creating an incredibly tight and durable seal. Once polished, your new Inlay or Onlay will feel and function just like a natural tooth.

Types of Materials Used for Inlays and Onlays

The choice of material is a key factor in the final cost, aesthetic result, and long-term durability of your Tooth Restoration. The three main materials used for inlays and onlays are ceramic (porcelain), gold, and composite resin.

1. Porcelain/Ceramic Inlays and Onlays

Porcelain is by far the most popular choice in modern Australian dentistry, especially for visible back teeth.

• Aesthetics: Exceptional. Porcelain can be perfectly colour-matched to your surrounding natural teeth, making the restoration virtually invisible. It also mimics the light-reflecting qualities of natural enamel.
• Strength and Durability: Very high. Modern ceramics are incredibly strong and resistant to fracture and wear. They are also highly stain-resistant.
• Ideal For: Patients who prioritise a natural, aesthetic result, and those who require a strong restoration for a larger cavity.

2. Gold Inlays and Onlays

While less common now due to aesthetic preference, gold remains arguably the best restorative material in terms of sheer longevity and strength.

• Aesthetics: Non-tooth coloured (obviously gold). Used less frequently for teeth that are highly visible.
• Strength and Durability: Unmatched. Gold is highly biocompatible and wears down at a rate similar to natural tooth enamel, meaning it won’t wear down the opposing tooth. It has fantastic strength even in thin sections, which means the dentist can remove the absolute minimum amount of healthy tooth structure during preparation. Gold Inlays and Onlays are known to last over 30 years.
• Ideal For: Patients prioritising supreme strength and longevity over aesthetics, often for non-visible back molars, and for those who clench or grind their teeth (bruxism).

3. Composite Resin Inlays and Onlays (Indirect Composite)

This material is similar to what is used for direct fillings, but the restoration is made in the laboratory (indirectly).

• Aesthetics: Good, as the material is tooth-coloured.
• Strength and Durability: Good, but not as strong or wear-resistant as porcelain or gold. The benefit is that when composite is made outside the mouth and then bonded in, it experiences less internal shrinkage and stress than a massive direct filling, offering a better fit.
• Ideal For: Patients looking for a slightly more budget-friendly tooth-coloured option, or when the damage is moderate and does not require the maximum strength of porcelain.

Caring for Inlays and Onlays

One of the great pieces of news about having a dental Inlay or Onlay fitted is that the ongoing care is essentially the same as caring for your natural teeth. These durable restorations don’t require any complicated special treatments, but a few simple habits will ensure their incredible longevity.

Routine Oral Hygiene is Key

• Brush Twice Daily: Use a soft-bristled toothbrush and a fluoride toothpaste. Pay close attention to the gum line around the restored tooth, as this is where plaque can accumulate.
• Floss Daily: Flossing is crucial for cleaning the margins where the restoration meets the natural tooth. This tight seal must be kept clean to prevent recurrent decay. Use a gentle, back-and-forth motion, being careful not to ‘snap’ the floss too hard onto the restoration.
• Use Mouthwash (Optional): A non-alcoholic, fluoride mouthwash can help keep the entire mouth clean and provide extra protection against decay.

Protect Your Investment

• Avoid Hard or Sticky Foods: While your Inlay or Onlay is incredibly strong, constantly chewing on extremely hard items like ice, hard lollies, or pens can put unnecessary stress on the restoration and the remaining tooth structure. Cutting up hard foods like apples or crunchy vegetables is a good practice.
• Address Teeth Grinding (Bruxism): If you are a known teeth clencher or grinder, the constant force can eventually wear down or damage even the strongest restorations. Discuss this with your dentist. They will likely recommend a custom-fitted nightguard to protect your Inlay, Onlay, and all your natural teeth while you sleep.
• Regular Dental Check-ups: Consistency is vital. Schedule and keep your regular check-ups with your dentist in Kensington (or wherever you are). These professional visits, usually every six months, allow your dentist to:
  • Monitor the condition of the restoration.
  • Check the integrity of the margins (the seal).
  • Assess your bite and make sure the restoration isn’t causing wear on the opposing teeth.
  • Perform a professional scale and clean to remove hardened plaque (calculus).

How Long Do Inlays and Onlays Last?

When a dentist recommends an Inlay or Onlay, they are often referring to them as a long-term investment. Compared to a direct composite filling, which may need to be replaced after 5-15 years, the lifespan of a laboratory-made restoration is significantly longer.

With proper care, a high-quality Porcelain Inlay or Onlay can comfortably last between 10 to 30 years. Gold restorations, due to the material’s superior properties, are frequently known to last even longer—often 30 years or more.

The longevity depends on a few key variables:

1. Material: Gold is the longest-lasting, followed closely by modern ceramics.
2. Oral Hygiene: Excellent brushing and flossing are paramount to protecting the margin from decay.
3. Bite Forces: Patients with heavy bites or bruxism need proactive protection (like a nightguard) to prevent premature wear.
4. Dentist’s Expertise: The quality of the preparation and the bonding technique used by the dentist is crucial for achieving that long-lasting, perfect seal.

Cost and Insurance Coverage in Australia

The cost of a dental Inlay or Onlay in Australia is often higher than a standard filling but is generally less than a full dental crown. The price reflects the higher material cost (porcelain or gold), the significant laboratory fee for custom fabrication, and the extended time and expertise required by the dentist across two appointments.

Cost in Australia

In Australia, the cost of a single Inlay or Onlay typically ranges from $800 to $1,600 per tooth.

• Factors influencing cost include:
  • Size and Complexity: A larger Onlay covering multiple cusps will cost more than a small Inlay.
  • Material: Gold and advanced ceramics can be more expensive than indirect composite resin.
  • Laboratory Fees: The cost the dentist pays the dental technician for the custom-made piece is factored into the final price.
  • Location: Fees can vary between city and regional practices.

Health Fund and Insurance Coverage

Because Inlays and Onlays are restorative procedures—designed to repair and restore the health and function of a damaged tooth—they are typically covered under the Major Dental category of private health insurance (known in Australia as a ‘health fund’).

• Check Your Cover: You will need to check with your specific health fund provider and policy details. If you have “Extras” cover, you need to confirm that it includes Major Dental.
• Waiting Periods: If you are new to Major Dental cover, there is usually a waiting period of 6 to 12 months before you can claim for Inlays or Onlays.
• Rebate Amount: Health funds generally cover a percentage of the fee (e.g., 50% to 75%) up to a yearly limit. It is important to ask your dentist for the specific ADA Item Numbers (e.g., 552 for a 2-surface restoration) and contact your health fund before starting treatment to get a precise quote on your out-of-pocket expense.

The increased upfront cost of an Inlay or Onlay is often offset by its exceptional longevity. If a durable, custom restoration lasts 20 years, it can be significantly more cost-effective than replacing a cheaper, failing filling every five to ten years.

Conclusion

When a tooth has sustained damage that falls outside the scope of a simple filling—whether due to extensive decay, a fracture, or a failing old restoration—the Inlay and Onlay offers the perfect, durable middle ground. They are a modern, conservative, and structurally superior way to restore your teeth.

By choosing an Inlay or Onlay, you are opting for a custom-made, laboratory-crafted solution that promises:

• Superior Strength: Reinforcing the remaining tooth against chewing forces.
• Maximum Preservation: Retaining significantly more of your natural tooth than a full crown.
• Exceptional Aesthetics: Providing a seamless, natural-looking result with high-quality porcelain.

If you are looking for a long-lasting Tooth Restoration that is designed for both function and beauty, Inlays and Onlays are a smart investment in your oral health.

Call to Action

Ready to find out if an Inlay or Onlay is the right Tooth Restoration solution for you? The best next step is to have a comprehensive assessment.

Contact a trusted dental professional today to discuss your options. If you’re searching for a dentist Kensington locals trust for expert, high-quality restorative work, don’t put off your dental health any longer.

Book a consultation to get a personalised treatment plan and a clear breakdown of the costs. Give your smile the durable, long-term care it deserves.