unit 3 / temporary (provisional restoration)

Provisional restoration, requirements

1. Biologic

2. Mechanical

3. Esthetic

Biological requirements

1. protect the pulp: to seal and insulate the pulp

2. maintain periodontal/ gingival health( good marginal fit, proper contours, smooth surface)

3. occlusal compatibility( establish and maintain proper contacts)

4. protect tooth against fracture( crown margins)

5. maintain tooth position and proximal contacts

Mechanical requirements

1. resist functional loads- chewing

   • increase connector size( sometimes dictated by esthetics). Do not over-contour near gingiva

   • good access for plaque control must have a priority

   • strength is about 20 times weaker than a completed restoration

2. resist displacement/ removal forces

   • closely adapted internal surface

   • generic preformed crowns should be avoided

   • excessive space creates greater demands on temporary cement

3. removal for reuse

• often need to be reused

• should break upon removal

Esthetic requirements

1. Easily contoured

• appearance particularly important for the anterior region

• allows the patient to see preliminary contours

• modified until appearance is mutually acceptable- lab

  2. color compatibility and translucency

• essential to match adjacent teeth

3. color stability

• many resins discolor after several months

• stains and bleach can affect

4. the definitive restoration closely matches the provisional in form

5. established function and form using provisional restoration

What is an external surface?

Refers to the exterior contour of the restoration( contour, shape, shade)

What is an internal surface?

refers to the prepared tooth surfaces and edentulous ridge included in the prosthetic fabrication(tooth preps)

External surface form

1. Custom Indirect

   • vacuum formed

   • waxed and fabricated

   • CAD/CAM

   • putty matrix

2. Direct/ In clinic

   • vacuum formed

   • alginate

   • base plate impression

   • putty matrix

3. Preformed /Direct in clinic

   • polycarbonate - natural appearance, color stable

   • aluminum and aluminum anatomic

   • tin-silver, nickel-chromium anatomic

Internal surface

Indirect/ lab/ fabricated outside in a lab from an impression on a cast

+ no contact of free monomer in the oral environment, better marginal fit, replacement restoration without having a patient present, avoids subjecting prepared tooth to heat from exothermic reaction

- takes longer than the direct method

Direct/mouth/ provided by the patient’s prepared teeth and gingival tissues

+ Fabrication is done in one appointment

- potential tissue trauma, inherently poor marginal fit, is not recommended when indirect techniques are feasible

Indirect-direct( mouth + lab)/ thin prefabricated shell made on a cast in a lab. Resin is used to fill the shell by the dentist and the mouth is used as the internal surface form

+ Chair time reduced, less heat generated in the mouth, minimized resin monomer contact with the soft tissues

- adjustments are frequently needed to seat the shell completely, the technician must minimally grind the tooth on the model to create a prep.

Examples of commonly used materials to fabricate provisional/ temporary restoration

• light-cure acrylic

• cold-cure acrylic

• composite

• tin

• aluminum

• nickel

• polycarbonate

An ideal provisional material characteristics

1. convenient handling - handling/working time

2. biocompatibility

3. dimensional stability during solidification

4. ease of contouring and polishing

5. adequate strength and abrasion resistance

6. good appearance- color controllable

7. good patient acceptance

8. ease of adding to/ repairing