A dental restoration is a custom-made fixture designed to repair a tooth damaged by decay or fracture, returning it to full function. While many people are familiar with traditional fillings or full dental crowns, restorative dentistry offers a solution that occupies a space between these two options. This intermediate solution is the porcelain onlay, a precise, custom-fabricated restoration. It is an indirect restoration, meaning it is made outside of the mouth, which allows for superior strength and a highly accurate fit.
Defining the Porcelain Onlay
A porcelain onlay is a partial coverage restoration designed to repair teeth that have sustained moderate damage. It is fabricated as a single, solid piece, typically from a strong, tooth-colored ceramic material, and then bonded permanently onto the tooth. The distinguishing feature of an onlay is that it covers one or more of the cusps, which are the points on the chewing surface of the back teeth.
This differs from an inlay, which fits within the cusps, similar to a traditional filling, but is also a lab-made solid piece. It also contrasts with a full dental crown, which completely encases the entire visible portion of the tooth above the gum line. The porcelain material is highly valued for its ability to mimic the natural translucency and color of tooth enamel, making the restoration virtually undetectable while providing high durability and a strong repair.
When Are Onlays the Right Choice?
Onlays are often recommended when the damage to a tooth is too extensive for a direct filling, but not severe enough to warrant the complete structural coverage of a crown. A primary indication is when decay or a fractured filling has extended to weaken or break a cusp, which is a significant structural component of the tooth. If a cavity’s width takes up more than one-third of the tooth’s chewing surface, a direct filling may not provide enough long-term strength, increasing the risk of fracture.
The onlay’s main benefit is its conservative approach, preserving a significantly greater amount of healthy tooth structure compared to a full crown. Preparing a tooth for a crown requires the removal of tooth material from all sides, whereas an onlay only requires removing the damaged portions. By bonding the onlay to the remaining natural tooth structure, the restoration effectively strengthens a weakened tooth, reducing the risk of future fractures.
The Two-Visit Placement Procedure
Receiving a porcelain onlay requires two appointments to allow time for custom fabrication. During the first visit, the dentist numbs the area and removes decayed tissue or old filling material, carefully preparing the tooth surface. After preparation, a highly accurate impression or digital scan of the prepared tooth is taken and sent to a specialized dental laboratory.
The laboratory uses this data to design and mill the porcelain onlay, ensuring it perfectly matches the tooth’s anatomy and bite. Before leaving the first appointment, the dentist places a temporary restoration to protect the prepared tooth while the permanent onlay is being made. The second visit occurs once the custom onlay returns from the lab, usually within a few weeks.
The temporary restoration is removed, and the dentist checks the new porcelain onlay for an exact fit, ensuring proper contact with adjacent teeth and a comfortable bite. Once the fit is confirmed, the restoration is permanently bonded to the tooth using a strong adhesive cement. The final step involves polishing the bonded onlay and making minor adjustments to the bite to ensure a smooth transition between the porcelain and the natural tooth.
Maintaining and Protecting Your Restoration
The longevity of a porcelain onlay is directly related to consistent oral hygiene and preventative care, with well-maintained restorations lasting 10 to 15 years or longer. Daily maintenance involves brushing twice a day with a non-abrasive toothpaste and flossing once a day. It is important to pay close attention to the margins, where the onlay meets the natural tooth, to prevent plaque accumulation.
Avoiding habits that place excessive stress on the porcelain is important, including steering clear of chewing on ice, hard candies, or very firm objects. For patients who clench or grind their teeth (bruxism), wearing a custom-fitted night guard is highly recommended. Bruxism creates significant forces that can cause the porcelain to chip or fracture. Regular dental check-ups and professional cleanings allow the dentist to monitor the onlay’s integrity and address issues before they become major concerns.