Restoration of the worn dentition

Although tooth wear is considered to be age dependent, an increasing number of both adult and young patients is experiencing tooth wear, usually erosive in nature. It can present in variety of forms and severity. Prevention of further tooth wear should form the basis of care but in severe cases interventive restorative treatment may be necessary in order to protect vulnerable tooth surfaces and re-establish satisfactory appearance and function. Indications for interventive restorative treatment are: unacceptable appearance of the teeth, loss of normal function and progressive tooth wear resulting in pulp necrosis and/or difficulty in teeth restoration. The restorative treatment options possible with today's materials and techniques include: conventional fixed restorations, removable onlay/overlay prostheses and minimal preparation adhesive restoration. This article will review the restorative treatment options available to restore the worn dentition.

may be necessary to protect vulnerable tooth surfaces and re-establish satisfactory appearance and function. Indications for interventive restorative treatment are: • Unacceptable appearance of the teeth • Loss of normal function • Progressive tooth wear resulting in pulp necrosis and/or difficulty in teeth restoration The restorative treatment options possible with today's materials and techniques include: • Conventional fixed restorations • Removable onlay/overlay prostheses • Minimal preparation adhesive restoration Overview (see Table 1)

Materials/instruments Conventional fixed restorations
• Porcelain-fused-to-metal (PFM) crowns • All-metal crowns • All-ceramic crowns Conventional crown restorations, being an invasive procedure, require adequate interocclusal space which is usually lost as a result of compensatory eruption of opposing teeth during the process of tooth wear. Conventional restorative techniques to overcome the reduced crown height and lack of interocclusal space are: • Opposing tooth reduction.
• Elective endodontic treatment and post retention.

Removable onlay/overlay prosthesis
It is recommended to construct a provisional acrylic resin removable prosthesis so that the shape, position, occlusal relationship of the prosthetic teeth and soft tissues as well as the patient's tolerance of a removable prosthesis can be assessed (Fig. 4).
The available space determines whether or not an anterior labial flange can be used or alternatively gingival fitting and/or butt-fitting tooth facings. The space demands are usually greatest in the anterior region both in the vertical and labiolingual dimensions (Fig. 5).

Cervical tooth wear
Depending on the type of the lesion, different materials can be used ( Fig. 6) (see Table 2).

Anterior tooth wear
Palatal tooth wear To manage this form of tooth wear resin-bonded palatal metal alloy veneers can be considered. The incisal and palatal peripheral enamel margins are smoothened and laboratory fabrication of the metal alloy veneers is either done    Moderate/severe tooth wear with an unfavourable occlusal relationship initially restored with a provisional onlay/overlay removable prosthesis to assess appearance and function. a Before restoration. b After restoration with removable prosthesis directly on a refractory working cast or by a wax/resin 'lift-off' technique. Interocclusal space is usually created to accommodate the thickness of the restoring material. When there is excessive tooth wear in the cervical region rubber dam isolation is used and occasionally gingival retraction cord. Cementation is done using luting cements that are usually resin-based and used in combination with the manufacturer's dentin bonding agent where appropriate (Fig. 7).
Incisal/palatal tooth wear The incisal portion of the tooth can be built with direct acid-etch retained composite resin and then a resin-bonded metal alloy palatal veneer can be constructed to cover both the palatal tooth tissue and composite resin by which the appearance of lost incisal and labial tooth tissue can be improved.  The incisal and palatal tooth surfaces can be restored conservatively with direct acid-etch retained composite resin at an increase in occlusal vertical dimension to accommodate the thickness of the restorative material.
Diagnostic wax-up is done on stone casts of planned restorations. Then rubber dam isolation of teeth is done prior to adhesive restorations. Silicone putty index and interproximal tape are used to aid restoration (Fig. 8).
A number of clinicians use modified porcelain laminate veneer restorations for the incisal and palatal worn tissue.
Indirect densified composite resins are the alternatives to using direct composite resins, with the potential advantages of improved physical properties and better control regarding occlusal and interproximal contouring.
Labial/incisal/palatal tooth wear All tooth surfaces can be restored with direct composite resin at an increased occlusal vertical dimension in an attempt to initially recreate lost interocclusal space. After that a decision can be taken either to continue with ongoing maintenance of the composite resin restorations or alternatively to consider proceeding to conventional crowns conforming to the newly established occlusion (Fig. 9).
In some cases with minimal tooth structure, localized crown lengthening surgery can be advantageous which will help to capture all remaining tooth enamel. If for any reason surgical crown lengthening is not available, then indirect splinted composite resin restorations can be considered to aid retention and durability (Fig. 10).

Posterior and generalized tooth wear
Resin-bonded heat-treated gold alloy restoration can be used in cases where aesthetics is not paramount (Fig. 11).
If aesthetics is a primary concern then a resin-bonded ceramic or indirect composite resin onlay can be considered.
In situations where retention and resistance form for conventional crowns are particularly compromised these techniques are helpful (Fig. 12).
In cases of generalized tooth wear, where a full mouth reconstruction of the dentition is indicated, the use of adhesive onlay restorations in the posterior quadrants can be considered in certain circumstances. If space is at a premium, the Fig. 7 Nickel-chromium alloy resin-bonded palatal veneers used to restore localized palatal tooth wear for maxillary incisor teeth. a Palatal view of veneers. b Labial view demonstrating re-establishment of posterior occlusal contacts selection of a gold alloy instead of porcelain will be advantageous. In some cases a full mouth reconstruction of the worn dentition using resin-bonded ceramic or indirect composite resin restorations is possible.  Removable onlay/overlay prostheses • Maintenance demands-material wear and fracture being common • Difficulty in adapting both functionally and psychologically

Minimal preparation adhesive restorations
Unpredictable longer-term durability, particularly of the posterior onlay restorations; characteristically small fracture lines can appear in time which may eventually result in a catastrophic failure.

Temporization
Procedures involving complete resin bonding of the temporary restoration to the underlying tooth tissue may compromise the subsequent adhesive bond for the final restoration.

Damage to tooth structure
Risk of damage to the tooth preparation during the removal of the interim resin lute.

Adhesive material
Using a less adhesive material or technique can result in the early loss of any temporary restorations, with the possible consequences of unplanned tooth movement. In try-in stage checking the occlusal relationship can be a challenge due to the relative lack of retention of the restorations before cementation.
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