In cases where there is significant loss of tooth structure, direct restoration of the tooth with fillings may be challenging due to the large amount of missing tooth structure. Sometimes, it may be difficult to restore the tooth to its original natural appearance, especially if it is in a location subject to heavy chewing forces, increasing the risk of fracture.
Additionally, in cases where the margins of the cavity are deep near the gum line, direct restoration may not effectively cover up to the gum line, increasing the risk of recurrent decay. Similarly, if the tooth has a large cavity, poor alignment, or cannot be adequately restored directly to achieve good contact points, indirect restoration may be necessary. This is known as inlays/onlays or partial coverage restorations, different from full coverage crowns.
In preparing teeth for inlays or onlays, the dentist removes less tooth structure and covers less tooth surface compared to crowns. That is, the tooth preparation and replacement of the restoration lie between that of fillings and full crowns. However, partial coverage restorations may not always be suitable, depending on the remaining tooth structure, position, and the dentist’s discretion.
Advantages:
- Ability to shape the tooth outside the mouth before adhering the material to the tooth.
- Better properties than conventional filling materials, providing strength and resistance to chewing forces.
- Preserves remaining tooth structure and protects against fracture.
- In some cases, the margin does not extend to the gum line, making it easier to clean around the restoration.
Procedure:
- Detailed examination of the teeth and radiographic imaging to assess the condition of the tooth nerve pulp and root apex.
- Impression of the mouth to create a model of the teeth, used for treatment planning and designing the shape of the restoration.
- Tooth preparation and temporary restoration to prevent tooth sensitivity.
- Fabrication of the final restoration based on the model, which takes about 1-2 weeks. Meanwhile, a temporary restoration is placed in the mouth.
- Try-in and adjustments of the final restoration for fit, margins, and occlusion before permanent cementation.
- Follow-up appointment after one week to assess the patient’s response and any post-treatment symptoms.
Types of Inlays and Onlays
Materials for inlays and onlays can be broadly categorized into two types: metal and tooth-colored materials. Metal materials mostly consist of alloys containing gold for strength and durability to protect the remaining tooth structure from fracture. Tooth-colored materials (resin, composite, or porcelain) are chosen for their aesthetic properties. However, these materials have limitations in high-stress areas, such as the second molars, due to the risk of fracture.
