Tooth preparation: Control reduction.
Proper preparation is vital to the veneers’ esthetics, functionality, and longevity – and it should be performed meticulously and thoughtfully. The restorative material thickness required for each case depends on a number of factors, including material, desired shade, strength considerations, and the patient’s parafunctional habits, such as bruxing or clenching. These, along with several other factors, should be considered before preparing the teeth:
- Preparation depth should be confined to the enamel, when possible (in contrast, a full crown is preferable if there is little to no enamel present)
- There should be no more than 2mm of unsupported ceramic
- Existing restorations need to be included
- How far the proximal and incisal edges need to extend (whether a butt joint or feathered edge is used, or if interproximal contact needs to be broke)
- Note that in terms of color changes, depending on the material and its opacity, each shade change may require extra space to mask the substrate – usually 0.2mm additional facial thickness.
Start with the mock-up in the patient’s mouth – this enables better control of enamel removal and a more conservative prep. Beginning with the facial preparation, cut grooves into the mockup to the depth required by the material on the cervical third, mesial third, and incisal third of the tooth and mark with a pencil. Without these marks, it can be difficult to see exactly when you’ve reached the correct depth. However, with these marks in place, you stop when the bur touches the mark and know you have the space you need. After the facial reduction is complete, the proximal margins should be extended to the interproximal contact point. While it’s not always necessary to open the interproximal contacts, such as for diastemas or overlapping teeth, extending the preparation into the interproximal area helps to conceal margins, allow for more accurate impressions, and improve adhesion (Figure 6). Last is the incisal reduction with a minimum of 1.5mm, checking against the prep guides and periodontal probe as necessary. From there, any sharp internal angles in the prep should be rounded out with a disc, then a rubber point can be used to smooth the prep surface before any impressions are taken. Alternatively, the preparation can be polished with fine grain burs.

Figure 7: Step by step veneer preparation. Illustrations courtesy of Prof. Paulo Monteiro.
While extremely rare, there are a few circumstances that don’t require much prep at all. In these cases, commonly referred to as “no prep veneers,” ceramic is added on top of existing tooth structure. I prefer the term “prep less” over “no-prep,” as you almost always have to prep something. For example, even with no-prep veneers, I like to at least make some delineation on the cervical gingival margin – both for visualization and so the dental technician knows where the finishing line will be, so we don’t have any unfortunate surprises when we go to cement and find that it reaches the gingival margin.