One of the most common procedures in the dental practice is the preparation of teeth for full crown restorations. As common as it is, a step in this procedure that many dentists get hung up on is where to finish the gingival margins. The placement of the margin can be supragingival, equigingival or sub gingival; however, that decision must be based on the situation. In order to choose the correct placement for the gingiva, it's helpful to know the advantages and disadvantages of each one.
Supragingival Margins: Supragingival margins indicate you are going above the tissue to place the margin.
- Advantages: There is no doubt what the advantages are for staying supragingival. It's easy to finish with a burr because you won't hit tissue. Since the margin will be above the gingiva, it's very easy to take an impression. Also, with supragingival margins you can expect excellent gingival health because the margin is not below tissue.
- Disadvantages: Esthetics can be compromised when using certain restorative materials. If you're using zirconia, metal or alumina, the process will be more difficult because the margin itself is more opaque. Anytime you're using a more opaque restorative material of any thickness, there will be a difference in opacity of the margin and tooth shade causing a visible line at the junction where the restoration meets the tooth.
Equigingival Margins: Equigingival margins indicate you are remaining even with the tissue to place the margin.
- Advantages: Similar to supragingival margins, it's easy to impress and finish equigingival margins because you are not going below the tissue. You can also expect to see very healthy gingiva, although maybe not as healthy as it would be if you were to stay above the tissue.
- Disadvantages: Equigingival margins carry very similar disadvantages as the supragingival margins. Esthetics can become an issue but if you go in even to the tissue, it is less likely you will have an unaesthetic result. However, if your patient has discolored teeth and you're using an opaque material, a highly esthetic result is more difficult to achieve than if you stayed subgingival.
Subgingival Margins: Subgingival margins indicate you are going below the tissue to place the margin.
- Advantages: The advantage of going subgingival is really all about esthetics. When using restorative materials like metal, zirconia, alumina or lithium disilicate as a coping, it's necessary to go below the tissue to hide discolored teeth and the junction with the restorative material. It should also be noted that whenever you are using more opaque materials, it's ideal to go subgingivally to hide margins.
- Disadvantages: The disadvantages of going subgingivally are quite obvious. For one thing, the gingiva may start to recede after placing the margin. You run the risk of having unhealthy gingiva since you're probing below tissue. It's also much harder to make an impression since you have to retract the tissue.