A long-term provisional is the temporary restoration of prepared (ground) teeth intended for crown or bridge restoration over an extended period of time. Temporaries – for both short-term and long-term restoration – generally serve:
- Protect the prepared tooth from thermal, mechanical and chemical stimuli.
- The protection of the dentin wound (the ground tooth bone) from bacterial noxae (harmful substances).
- The aesthetics
- The assurance of the chewing function
- The assurance of phonetics (phonation)
- The securing of the position of the teeth
Long-term temporaries have tasks beyond this. With their help, planned changes in jaw relation (positional relationship of upper and lower jaw to each other) and occlusion (interaction of upper and lower teeth during chewing closure and chewing movements) can be carried out and the success of therapy can be observed over a longer period of time before the definitive (final) restoration is incorporated. Long-term temporary restorations may also be required to bridge healing phases after surgical procedures or endodontic (root) treatments to give the bone and soft tissue time to regenerate.
Indications (areas of application)
- Therapeutic changes in jaw relation or occlusion.
- Healing phases – e.g. after periodontal therapy.
- Observation period for teeth initially questionable in terms of their preservability, which are important for further prosthetic (tooth replacement) care – e.g. post-endodontic teeth (after root canal treatment).
- Changes in aesthetics – e.g. color or shape changes.
- Changes in phonetics – corrections of tooth position by means of crowns.
- Palliative care of tumor patients
Contraindications
- Prognostically favorable teeth
- No planned changes in jaw relation or occlusion.
Requirements for a long-term temporary
- Oral stability
- Mechanical strength
- Repair and supplement possibility – e.g. to change the occlusion or to adjust the crown margins.
- Color stability
- Abrasion resistance (low abrasion)
- Hygienic ability
The procedures
Long-term temporaries are usually made from the following resins:
- Polymethymethacrylates (PMMA)
- Bis-GMA composites
- Glass fiber reinforced composites
Long-term temporaries of smaller circumference can be made in the patient’s mouth using direct technique by means of impressions taken before preparation (grinding) of the tooth in question. After preparation, the impression is filled with acrylic in the area of the ground tooth and placed back in the mouth. The removal of substance results in a hollow form in which the acrylic hardens in the form of a crown within a short time. The temporary crown is finished with fine burs and polishers. Usually, however, long-term temporaries, especially those that are to influence the positional relationship of the jaws and the occlusion, are fabricated indirectly in the dental laboratory after the dentist has taken impressions of both rows of teeth:
- Making the working model and the opposing jaw model from plaster.
- Fabrication of the temporary in free layering technique – the acrylic is applied freehand to the model of the prepared tooth
- Alternative: fabrication in cuvette technique – First, a wax model is fabricated freehand. This is then embedded in plaster in a so-called cuvette. After removing the wax, the plastic is pressed into the resulting hollow mold.
- Alternative: manufacturing in key technique – The shape of an initially produced wax model is fixed with the help of a so-called key, e.g. made of silicone, which can be reproducibly placed on the working model. If the wax model is removed, again a hollow mold is created, in which the temporary resin is filled.
- Stability reasons may require the incorporation of a metal framework.
- After chemical curing of the resin – usually under pressure and exposure to temperature – the temporary is finished with fine burs and polishers.
The incorporation of the temporary takes place in the dental office.Zinc oxide-eugenol cements have proven to be suitable as temporary luting materials. However, these are unsuitable if the final restoration is to be cemented using the adhesive technique (by micromechanical interlocking with the tooth surface). In these cases, the temporary cement must be eugenol-free (free of clove oil).
Possible complications
- Fracture (breakage) of the temporary restoration
- Premature detachment of the temporary from the tooth
- Intolerance to the resin used, especially to the residual monomer (individual components of the resin cross-linked in a long chain in a chemical reaction and thus hardened) slightly contained therein.
