Written by Brit Phillips, DDS, Sunday, 30 September 2007 19:00
As patients have more teeth restored with tooth-colored restorations, their desire to have aesthetic restorations is also increasing. For patients who care about aesthetics, an alternative to full crown preparation is the ceramic onlay. Since the tooth is already stressed from the large, old restoration, less preparation is very important to maintain healthy pulp tissue. Many old amalgam fillings can be replaced with bonded ceramic restorations (Figure 1). These preparations can be done quickly, since you only remove the necessary portions (eg, decay), and leave the rest. When the entire enamel shell of the tooth is removed for a crown preparation, this exposes all of the dentinal tubules to bacterial penetration. The onlay preparation leaves an enamel band almost all the way around the tooth (Figure 2), your ace in the hole for bonding. This allows for enamel and dentin bonding for the restoration, providing a strong bond and an excellent seal. In my experience, the chance for endodontic therapy decreases due to this less aggressive preparation of the tooth. If a large number of dentinal tubules are exposed, then the chance for a greater bacterial penetration into the tooth increases, causing pulpitis and potential nerve death.
Figure 1. Old amalgam fillings.
Figure 2. Onlay preparations leave an enamel band.
Figure 3. Impressions for the inlay/onlay are near perfect almost every time.
Figure 4. Temporaries without temporary cement.
Figure 5. The aesthetics is superior to restorations containing metal frameworks.
Figure 6. The final restorations blend in nicely with the surrounding teeth.
Figure 7. The final restorations as seen on the model prior to placement.
Aesthetic onlays have multiple advantages, such as restoration margins that can be placed supragingivally and still be invisible. The impressions are accurate on the first try nearly every time (Figure 3). The temporaries are shrink-wrapped onto the tooth, and no temporary cement is needed (Figure 4). The aesthetics is superior to restorations containing metal frameworks (Figures 5 and 6). No dark areas are visible at the gumline, since the restoration does not contain metal. The occlusion is usually very easy to adjust, since the remaining tooth structure gives you a good occlusal stop. Since these restorations are bonded in place, postoperative sensitivity is almost nonexistent. This bonding process allows for less microleakage than a conventionally cemented crown. This process is done while the teeth are isolated with a rubber dam, allowing for a very clean and neat uncontaminated bond.
In my practice I have found that the time needed to prepare teeth for onlays is significantly less than that needed for a crown, since onlay preparations are more conservative. The other observation is the decrease in pulpitis after these restorations. My patients rarely return after their restorations with complaints or adjustments. Another interesting fact is that patients now request this type of procedure when they require restorations. There is a learning curve to this type of procedure, but there are several educational centers that offer additional training (Figure 7).
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