Arguments for More Preparation

A presumption made earlier in this article was that it is easier for the dentist to do minimal-preparation veneers. There is a good argument for the preparation of low-preparation veneers being more technique-sensitive than normal-preparation veneers.6 This is especially true when the dental alignment is not perfect, diastemas exist, or there is a lot of gingival recession with large interproximal embrasures (interproximal space devoid of tissue).7 With well-aligned teeth that have tissue filling the interproximals, there is less wrap required to hide the margins. The porcelain can be more uniform in thickness and the anatomy of the teeth is only changed a little (buccal and incisal embrasures tend to be smaller). When teeth are misaligned or when more interproximal cavosurface is exposed, the porcelain needs to wrap more interproximally to fill the space so that all interproximal margins are tucked out of view. Many of these surfaces bend around more than 180° of the circumference, thus yielding undercuts and line-of-draw issues during fabrication and placement of the restorations. Laboratory fabrication issues escalate substantially. Trying to treat cases that exhibit path of insertion problems related to diastemas or rotations without adequate preparation can leave the ceramist in the undesirable situation where undercuts prevent adequate interproximal path of insertion and leave the ceramist with a choice of having to move the proximal contacts too far to the facial, resulting in a bulky appearance, or blocking out the undercut and extending the margins interproximally to allow ideal contour, but resulting in an open margin where the undercut was blocked out.

Advantages of Normal Preparation Over Low Preparation

  • Subtractive capabilities allow for more natural tooth contours
  • More control of buccal/lingual placement of incisal edges
  • Better control of midline alignment
  • Shade change without creating unnatural opacity
  • Less bulky emergence contours, especially on the cuspids
  • Easier placement with multiple line of draws
  • Less technique-sensitive for the dentist and technician
  • Easier to hide margins
  • Decreased tendency toward more closed/smaller buccal and incisal embrasures
  • More symmetrical shapes, especially of lateral incisors
  • Nicer surface textures
  • Nicer incisal characterization

The Ideal Patient

The ideal candidate for very conservative treatment is one with a slightly underfilled buccal corridor; slightly lingualized, small maxillary anterior teeth; closed or almost closed contacts; relatively even spacing of teeth; no gingival recession with gingival tissue filling interproximal areas; and no severe discoloration. Patients with full, slightly overdominant teeth are not good candidates, neither are severely tetracycline-stained cases.8 Patients exhibiting loss of interproximal soft tissue, crowding, and rotations require careful screening described earlier and usually require orthodontics before veneering.9 Patients exhibiting excessive spacing require orthodontic treatment before veneering as well.10 The patient population that has all of these characteristics is small.8