Dental inlays and onlays offer an excellent alternative to “direct” amalgam or composite fillings to restore teeth that have sustained some damage, but not enough to require a full coverage crown. While “direct” fillings such as dental amalgam and composite fillings are placed immediately after the decay or damage is removed and the tooth is prepared, inlays and onlays are known as “indirect” fillings. This means that they are fabricated outside of the mouth prior to final bonding or cementation.
While in the past, many inlays and onlays were caste from gold; today’s dental inlays and onlays are typically custom made of either the highest grade of dental porcelain or composite resins. In addition to providing an exact match to the color of tooth for a cosmetically pleasing result, inlays and onlays have the distinct advantages of being more durable than other fillings, preserving more underlying tooth structure and actually strengthening the tooth so that it can bear up to 50 to 75 percent more chewing forces.
Inlays and onlays only differ from each other in the amount of tooth structure they cover. An inlay is fabricated when the replacement of tooth structure does not require coverage of any cusp tips. If the damage from decay or injury is more extensive and involves more of the tooth’s chewing surface, including one or more cusp tips, an onlay is required.
Both inlays and onlays are fabricated outside of the mouth based upon the exact specifications provided by an impression of the prepared tooth. The final inlay or onlay is then custom made by either a dental laboratory or in-office with a same day system.
Dental inlays and onlays are indirect restorations custom made to repair a tooth that has been damaged by decay or trauma. An inlay fits within the cusps of a back tooth to restore the central chewing surface, while an onlay extends over one or more cusps and can restore a larger portion of the tooth. Both are fabricated outside the mouth from materials such as porcelain, composite resin, or metal for a precise fit.
These restorations are designed to preserve as much healthy tooth structure as possible while restoring function and aesthetics. Because they are bonded to the tooth, inlays and onlays can strengthen a damaged tooth and resist staining for a natural appearance. They are a conservative alternative when a traditional filling would not provide adequate support but a full crown may be more than necessary.
Fillings are placed directly into a prepared tooth and are typically used for small to moderate cavities, while inlays and onlays are made in a laboratory and cemented or bonded into place. A crown encases the entire visible portion of a tooth and is chosen when damage is extensive or when structural support is required. Inlays and onlays occupy a middle ground by providing more coverage and strength than a filling but preserving more natural tooth structure than a crown.
Because inlays and onlays are fabricated to fit precisely, they often offer superior marginal integrity compared with large direct restorations. They can reduce the risk of recurrent decay at margins and distribute chewing forces more evenly across the repaired tooth. This makes them particularly useful for restoring molars and premolars where chewing pressure is greatest.
Common materials for inlays and onlays include porcelain, composite resin, and various metals such as gold. Porcelain and ceramic options are prized for their color stability and natural appearance, making them a popular choice for patients who want restorations that blend with their teeth. Composite resin can be more conservative and is bonded directly to the tooth, while metal restorations offer excellent strength and longevity in high-stress areas.
Porcelain and ceramic restorations are often bonded with adhesive resins to create a strong interface with the tooth, and they resist staining over time. Metal inlays and onlays remain a reliable option when maximum durability is required, although they are more noticeable. Your dentist can recommend the best material based on the tooth’s location, the extent of damage, and aesthetic goals.
Good candidates are patients with moderate decay or damage that compromises the chewing surface but leaves enough healthy tooth structure to support a partial restoration. Inlays and onlays are especially appropriate when a filling would be too large to provide long-term stability, yet a crown would remove more healthy enamel than necessary. Patients who want a durable, tooth-conserving option with a natural appearance often choose these restorations.
Your dentist will evaluate the tooth using clinical examination and imaging to determine whether an inlay or onlay is the best choice. Factors such as bite forces, the tooth’s position, and existing restorations are considered when planning treatment. If you have concerns about aesthetics, function, or longevity, discuss them during your consultation so the plan can be tailored to your needs.
The procedure typically begins with removing decay and shaping the tooth to receive the restoration, followed by an impression or digital scan to capture the prepared tooth. Many practices, including those that use advanced digital tools, send this information to a laboratory or use chairside milling to fabricate a precise restoration. A temporary restoration may be placed when a laboratory is involved, and the custom inlay or onlay is bonded at a follow-up appointment.
The entire process is usually completed in two visits when laboratory fabrication is used or in a single visit with same-day technology. Local anesthesia is used to keep you comfortable during tooth preparation, and your dentist will check the fit, color, and bite before final bonding. The result is a strong, well-fitting restoration that restores chewing function and blends with the surrounding teeth.
After the custom restoration is tried in and adjusted for fit, the dentist prepares the tooth surface and the restoration for bonding using adhesive resin systems. A sequence of cleaning, etching, and application of bonding agents helps create a durable chemical and micromechanical bond between the porcelain or composite and the tooth structure. The restoration is then seated precisely and light-cured or chemically set according to the materials used.
Proper bonding is essential to restore strength and prevent microleakage at the margins, which reduces the risk of future decay. Modern adhesive protocols create a strong interface that can increase the restored tooth’s resistance to fracture. Your dentist will verify the occlusion and polish the margins to ensure comfort and longevity after bonding.
When properly designed, fabricated, and bonded, inlays and onlays can last many years and provide excellent durability under normal chewing forces. Longevity depends on factors such as material choice, oral hygiene, occlusal stress, and the quality of the bond between restoration and tooth. Porcelain and metal restorations tend to resist wear and staining, while well-bonded composites can perform very well in the right situations.
Regular dental checkups allow your dentist to monitor the restoration for signs of wear, marginal breakdown, or recurrent decay so issues can be addressed early. Good daily oral hygiene and avoiding habits such as chewing ice or hard objects help protect the restoration. With attentive care, many patients enjoy reliable function and aesthetics from inlays and onlays for a decade or longer.
Caring for an inlay or onlay is similar to caring for a natural tooth and includes regular brushing with fluoride toothpaste and daily flossing to prevent decay at the margins. Be mindful of chewing habits and avoid excessive force from grinding or clenching; if you have bruxism, your dentist may recommend a night guard to protect restorations. Routine dental visits are important so your provider can assess the restoration and address any minor adjustments before they become problems.
If you notice sensitivity, a change in bite, or roughness along the restoration’s edge, contact your dental team promptly for an evaluation. Early attention to these signs can prevent more extensive treatment down the road. Maintaining a partnership with your dentist and following their preventive recommendations will help your restoration perform well over time.
As with any dental procedure, inlays and onlays carry some risks, though complications are relatively uncommon when treatment is performed properly. Patients may experience temporary sensitivity after tooth preparation or bonding, which typically subsides within a few days to weeks as the tooth acclimates. Rarely, marginal breakdown or recurrent decay can occur if hygiene is insufficient or if the restoration becomes compromised by excessive force.
Proper case selection, high-quality materials, and careful bonding techniques minimize these risks and improve long-term outcomes. Your dentist will review potential complications and the expected course of recovery during the consultation so you can make an informed decision. Prompt follow-up for any unusual symptoms helps ensure the best possible result.
Yes. In many cases an onlay can restore and support enough tooth structure to avoid a full coverage crown while preserving more natural enamel. Onlays are designed to cover damaged cusps and reinforce the remaining tooth, which can be preferable when sufficient tooth structure remains and full coverage would be unnecessarily invasive. The decision depends on the extent of damage, the tooth’s structural integrity, and the occlusal forces it must withstand.
Your dentist will evaluate the tooth clinically and with imaging to determine whether an onlay is a protective, long-term solution or if a crown would offer better structural support. At Fay Hu General Dentistry, we use careful assessment and advanced restorative techniques to recommend the most conservative and durable option for each patient. If you would like a personalized evaluation, our office offers a complimentary 30-minute consultation to review treatment choices and answer your questions.
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