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.
Inlays and onlays are indirect restorations fabricated outside the mouth to repair moderate tooth damage while preserving healthy structure. An inlay fits within the cusps on the chewing surface of a back tooth, whereas an onlay restores one or more cusps and can act as a partial crown. Both types are bonded to the prepared tooth to restore form and function and to distribute chewing forces more evenly.
These restorations are typically made from tooth-colored ceramics, high-strength composite, or metal alloys depending on clinical needs. Because they are custom-made, they provide a precise anatomical fit that supports proper occlusion and makes cleaning easier. When properly placed and maintained, inlays and onlays offer a conservative alternative to full crowns for many posterior teeth.
Direct fillings are placed and shaped in the mouth during a single appointment and are best for smaller defects, while crowns fully encircle the tooth and require more removal of healthy structure. Inlays and onlays occupy the middle ground: they are laboratory- or mill-fabricated restorations that preserve more tooth than a crown but are stronger and more precise than large direct fillings. This balance makes them especially useful when the remaining tooth structure is adequate but a filling would be too weak.
Because inlays and onlays are fabricated outside the mouth, they can be made from materials that resist staining and wear better than many direct composites. Their indirect fabrication also allows for a highly accurate occlusal anatomy and contact points that help maintain adjacent tooth relationships. Clinically, the choice among a filling, inlay/onlay, or crown depends on how much tooth remains and the functional demands on the tooth.
An inlay or onlay is often recommended when decay or fracture is too extensive for a direct filling but does not justify the removal of healthy tooth required for a full crown. These restorations are particularly appropriate for molars and premolars where chewing forces are greatest and preservation of cusps is beneficial. Dentists also consider the tooth’s remaining structure, the size and location of the defect, and the tooth’s role in the bite before recommending this approach.
Other factors that influence the recommendation include the presence of existing restorations, the patient’s oral hygiene habits, and aesthetic goals. For patients who prioritize conservative care and long-term tooth preservation, inlays and onlays can provide a durable and tooth-sparing solution. Your dentist will discuss the advantages and limitations of each option as part of a collaborative treatment plan.
Common materials for inlays and onlays include tooth-colored ceramics or porcelain, high-strength composite resin, and metal alloys such as gold. Ceramic and porcelain offer excellent aesthetics and resistance to staining, making them a popular choice for visible areas, while metal alloys can provide superior durability in high-stress situations. Material selection is based on functional requirements, aesthetic priorities, and the long-term health of the tooth.
The dentist evaluates occlusal forces, adjacent tooth color, and the patient’s bite pattern to recommend the most appropriate material. Advances in dental ceramics and adhesive technology have expanded the use of tooth-colored options even in posterior teeth. Ultimately, the decision balances appearance, strength, and conservation of tooth structure to support predictable outcomes.
Treatment typically begins with a clinical exam and diagnostic images to assess the extent of damage and plan preparation. Decay is removed and the tooth is shaped to provide a stable, retentive form for the restoration, after which an impression or digital scan captures the exact contours of the prepared tooth and bite. Digital intraoral scanning is increasingly common because it enhances patient comfort and communication with the lab or in-office milling system.
Once the restoration is fabricated, the dentist checks fit, shade, and occlusion before permanently bonding the piece with a strong resin cement. Proper adhesive technique and precise occlusal adjustments are critical to integrate the restoration with the tooth and restore function. A final polish and patient instructions complete the appointment, and follow-up visits confirm comfort and performance.
Longevity depends on material selection, quality of the fit, oral hygiene, and the functional demands placed on the tooth, but well-made inlays and onlays frequently last many years. Regular dental exams and professional cleanings allow the dentist to monitor margins, contacts, and wear so that minor problems can be addressed early. Good home care—brushing twice daily with fluoride toothpaste and cleaning between teeth—helps protect both the restoration and the surrounding tooth structure.
Avoiding parafunctional habits such as using teeth to open objects or chronic nail biting reduces stress on restorations and prolongs service life. If a restoration shows signs of marginal breakdown, wear, or fracture, early evaluation often allows for repair or replacement before more extensive treatment is necessary. Routine monitoring and prompt attention to changes support predictable, long-lasting results.
When fabricated from tooth-colored ceramics or composite materials, inlays and onlays are designed to blend with adjacent teeth and are typically hard to detect in normal conversation or smiling. Modern shading techniques and careful selection of translucency help match the restoration to surrounding enamel for a natural appearance. Because these restorations are confined to the chewing surface and cusps of posterior teeth, they are less visible than restorations on front teeth.
Metal-based inlays, such as gold, are more visible but can be indicated when maximum durability is required. Your dentist will discuss aesthetic goals during treatment planning and recommend materials that align with both function and appearance. In many cases, a tooth-colored option provides an excellent balance of strength and discreet aesthetics.
If an inlay or onlay experiences minor chipping or marginal issues, some repairs may be possible depending on the material and extent of damage. Composite repairs can sometimes be bonded to ceramic or composite restorations, but the success of repair depends on access, the condition of the existing margins, and the restoration material. When damage is more extensive or the restoration has lost its seal, replacement is often the most predictable solution.
Early detection through routine exams improves the likelihood of conservative repair. The dentist will assess the restoration’s integrity, check for recurrent decay, and recommend the least invasive option that reliably restores function and protects the underlying tooth. Timely attention to changes reduces the risk of more invasive procedures later.
Precision begins with careful tooth preparation and accurate impressions or digital scans that capture the prepared margins and occlusal relationships. Modern digital workflows and quality laboratory processes produce restorations that closely replicate the natural anatomy of the tooth, while chairside milling systems can deliver same-day solutions with high accuracy. At the try-in appointment the dentist evaluates fit, contacts with adjacent teeth, and how the restoration engages the opposing dentition.
Final cementation includes adhesive protocols that bond the restoration to the tooth and restore structural integrity. The dentist performs fine occlusal adjustments to eliminate high spots and ensure the restoration functions comfortably during chewing. Follow-up checks help confirm long-term comfort and allow adjustments if the bite or wear pattern changes.
Choosing the optimal restoration is a collaborative process that combines clinical examination, diagnostic imaging, and patient preferences to achieve the best long-term outcome. The dentist considers the amount of remaining tooth structure, the pattern of decay or fracture, occlusal forces, aesthetic priorities, and the condition of neighboring restorations when recommending an approach. In many cases an inlay or onlay is selected to conserve healthy tooth structure while providing strength and a predictable fit.
At Mercer Island Dental Associates the treatment recommendation is explained clearly so patients understand the rationale and expected results for each option. When uncertainties remain, clinicians may review alternatives and the risks and benefits to support informed decision making. The ultimate goal is to choose a restoration that protects oral health, restores comfort and function, and aligns with the patient’s long-term dental goals.
