Provisional Restorations Flashcards
What are Requirements of Provisional restorations
1-Pulpal protection.
- An interim fixed restoration must seal and insulate the prepared tooth surface from the oral environment to prevent sensitivity and further irritation of the pulp.
- A certain degree of pulp trauma occur during tooth preparation because of the sectioning of dentinal tubules. Unless the environment around the exposed dentin is carefully controlled, adverse pulp effects can be expected
- And in severe situations, leakage can cause irreversible pulpitis, with the consequent need for root canal treatment.
2-Occlusal Compatibility and Tooth Position
- The tooth should not be allowed to extrude or drift in any way. Any such movement will require adjustments or a remake of the definitive restoration at the time of cementation.
- Supraeruption (extrude) is detected at the evaluation appointment, when the definitive restoration makes premature contact. It is sometimes possible to correct this in the operating room, but the effort is time consuming and the resulting restoration often has poor occlusal form and function. If supraeruption is severe, it may be necessary to reprepare the tooth and make a new impression.
- Horizontal movement (drift) results in excessive or deficient proximal contacts.
3-Occlusal function. Being able to function occlusally with the provisional restoration will aid patient comfort, ward off tooth migration, and possibly prevent joint or neuromuscular imbalance.
4-Ease of cleaning. The restoration must be made of a material and contour that will permit the patient to keep it clean during the time it is worn. If the gingival tissues remain healthy while the provisional crown is in place, there is less likelihood of a problem arising after cementation of the definitive restoration.
5- margins. It is of most importance that the margins of a provisional restoration not impinge upon the gingival tissue. When gingival tissue is impinged on, ischemia is likely to develop, If it is not corrected, a localized inflammation or necrosis can develop.
A restoration with a damaging overhang or drastically underextended margins are not accepted.
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So an interim restoration should have good marginal fit, proper contour, and a smooth surface finish.
6-Strength and retention. The restoration must stand up to the forces to which it is subjected without breaking or coming off the tooth.
7-Esthetics. In some cases, the restoration must provide a good esthetic effect, particularly on anterior teeth and premolars.
Explain this picture
A, A properly contoured interim restoration. It is smoothly continuous with the external surface of the tooth.
B,Overcontouring.The transition from the restoration to the root surface is irregular, and marginal adaptation is inadequate. These contribute to plaque accumulation and an unhealthy periodontium.
What are Types of Provisional Restorations?
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There are numerous ways of providing protective coverage for teeth while permanent restorations are being fabricated. These range from zinc oxide–eugenol or non eugenol cement for small intracoronal inlay preparations to provisional crowns and provisional fixed partial dentures.
Talk a bout materials and procedures in Provisional Restorations?
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Many techniques or procedures involving a wide variety of materials are available to make satisfactory interim restorations.
In all the procedures, a mold cavity is formed, into which a plastic material is poured .
Furthermore, the mold cavity is created by two correlated parts: one forming the external contour of the crown or FDP terms external surface form (ESF) , the other forming the prepared tooth surfaces tissue surface form (TSF).
Then this mold lined by specific materials.
What are materials for lining in provisional restorations
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PMMA
- Poly-Rʹ methacrylate
- Microfilled composite •
Light-polymerized resins
What’s the summary of techniques to fabricate interim crown?
Talk about prefabricated or custom made. ESF
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Prefabricated forms include aluminum cylinders or shell ,anatomical metal crown forms ( aluminum, tin-silver, stainless steal), clear cellulose acetate, and tooth-colored polycarbonate crown forms. They can be used only for single tooth restorations.
Custom made for crown and fixed partial dentures can be fabricated by several different materials by a variety of methods, direct or indirect.
Talk a bout Anterior polycarbonate crown
A suitable provisional restoration can be made for single anterior teeth through the use of polycarbonate crowns. However, they frequently will require extensive alteration to correct morphologic discrepancies and improper contours.
If they are not carefully contoured, they will have horizontal overhangs that are damaging to the gingiva.
To accomplish the recontouring that is required and to provide the necessary retention, the toothcolored crown form must be relined with a resin. This can be accomplished with the greatest accuracy by doing the reline on a quick-set plaster cast of the prepared tooth.
Talk about Preformed anatomical metal crown
Emergency cases involving fractured molars are one of the best indications for the use of preformed metal crowns. Zinc oxide and eugenol alone will not adhere to the tooth, and there is rarely enough time at the emergency appointment to fabricate a custom acrylic resin provisional crown. By using the preformed anatomical metal crown, it is possible to provide the patient with temporary coverage to protect the fractured tooth and prevent irritation of the tongue and mucosa.
The procedure for use consists of
- Minimal tooth preparation
- Measurement and selection of crown
- Trimming and adaptation of gingival margin
- Occlusal adjustment
- Cementation
What materials for custom ESF
A custom ESF can be produced from thermoplastic sheets. Transparent sheets are available in cellulose acetate or polypropylene of various sizes and thicknesses , which are heated and adapted to a stone cast with vacuum
Talk about Template-fabricated provisional fixed partial denture
When a fixed partial denture is to be made for a patient, the provisional restoration should also be in the form of a fixed partial denture rather than individual crowns. In the anterior region it will provide a better esthetic result, and in the posterior region a provisional fixed partial denture will better stabilize the teeth and will afford the patient the opportunity to become accustomed to having a tooth in the edentulous space again.
Talk a bout cementation?
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The restoration should be cemented with a temporary cement of moderate strength.
Zinc oxide–eugenol (ZOE) cements appear to be the most satisfactory. the zinc oxide–eugenol cement has been mixed to a thick, creamy consistency, (should follow manufacture instruction, no more eugenol ).
Why we use Petrolatum?
Some time Petrolatum can be mixed with equal parts of the interim cement base and catalyst to reduce the cement’s strength by more than half.
This will facilitate removal of the provisional restoration at a subsequent appointment. If the preparation is short or otherwise lacking in retention, the petrolatum should not be added
What do we Reinforced ZOE for?
Reinforced ZOE; another might be eugenol-free zinc oxide, which has slightly greater strength than cements containing eugenol.
It is not necessary to keep zinc oxide–eugenol cement dry while it is setting. In fact, moisture will accelerate the hardening.
Coating the outside of the restoration with a thin film of petrolatum prior to cementation will aid in the removal of excess cement.
