Evaluation and Management of the Occlusal Vertical Dimension: Generalised Tooth Wear
Subir Banerji and Shamir B. Mehta
For cases of generalised tooth wear (TW), active restorative intervention will invariably result in an increase in the patient’s occlusal vertical dimension (OVD).
It is generally accepted that a freeway space (FWS) of 2–4 mm is considered to be ‘physiological’. While the process of TW will usually culminate in a reduction in the vertical height of the tooth tissues, compensatory mechanisms have evolved (dento-alveolar compensation) to preserve the OVD, permitting masticatory function to continue at a physiological vertical dimension. The placement of dental restorations (which can have the effect of increasing the height of the clinical crown) may therefore result in a reduced or indeed obliterated FWS and manifest in an array of symptoms.
It is thus critical to assess the FWS when planning treatment provision.
For descriptive purposes, the restorative management of generalised TW patients may be considered according to the three categories described by Turner and Missirilian. 1 These are:
- Category 1 – Excessive wear with loss of vertical dimension of occlusion.
- Category 2 – Excessive wear without loss of vertical dimension, but with space available.
- Category 3 – Excessive wear without loss of vertical dimension, but with limited space.
Regardless of the category, for any case of generalised TW where active intervention is being sought, a set of diagnostic casts mounted in centric relation (CR) is strongly advised. A semi-adjustable articulator with an arbitrary facebow may be considered acceptable, although a kinematic transverse horizontal axis facebow enables a more accurate transfer of the terminal hinge axis, helping to plan an increase in the OVD without introducing many errors in the horizontal jaw relationship. 2
The desired increase in OVD will primarily be determined by what is necessary to produce functionally stable, aesthetic dental restorations and adequate FWS. Once this has been established, the planned increase may be programmed into the articulator (by raising the pin) and a diagnostic wax-up fabricated accordingly.
Category 1 patients may be considered the most straightforward of all three categories to manage, as the resultant interocclusal clearance created through the process of TW will provide most, if not all, of the required space for the restorative material, while maintaining a physiological FWS. 3
A full coverage, hard acrylic stabilisation splint such as a Michigan splint or Tanner appliance can be used to evaluate the patient’s tolerance/adaptability to the planned occlusal changes.
In Category 2 patients there is ‘excessive wear without loss of OVD, but with limited space available’; in such cases a discrepancy will usually exist between centric occlusion (CO) and CR. CR may provide space to accommodate restorative materials; however, it might not always be fully adequate and there may be a need to plan an increase in the OVD. The patient should be provided with a full coverage, hard acrylic occlusal splint that will provide an increase in the OVD to the required range, while the mandible is manipulated into its retrusive arc of closure.3
The occlusal prescription of the splint should aim to provide a removable, mutually protective scheme. The patient should be instructed to wear the splint continually for a period of one month (at all times other than when eating) to evaluate the tolerance of the increase in OVD.
Unpredictable compliance with splint therapy has prompted an alternative approach, as described by Vialati and Belser. 4 This suggests that a more realistic approach would involve the placement of indirect provisional resin composite onlay and/or palatal resin veneers at the same occlusal prescription as would be provided by a full coverage, hard occlusal splint.