Provisional Crown Fabrication Flashcards

An EFDA is fabricating a provisional crown using the direct technique with a bis-acryl composite material. After the initial set, the EFDA removes the provisional from the prepared tooth and notices a rough, sticky, oxygen-inhibited layer on the surface. What is the most appropriate next step to manage this layer before final finishing and polishing?

Answer: Wipe the surface with an alcohol-soaked gauze.

Bis-acryl and other composite materials form an oxygen-inhibited layer (a thin, sticky, uncured surface layer) when they polymerize in the presence of air. This layer should be removed before finishing and polishing. Wiping the surface with alcohol is an effective method to remove this tacky layer, allowing for proper finishing.

A patient calls the dental office stating that their recently placed provisional crown on tooth #30 has come off while eating. Which of the following instructions is MOST critical for the EFDA to provide to the patient?

Answer: Schedule an appointment to have the provisional re-cemented as soon as possible.

A lost provisional crown must be replaced promptly. The primary functions of a provisional are to protect the prepared tooth, prevent sensitivity, and maintain the space to ensure the final crown fits correctly. If the space is not maintained, adjacent and opposing teeth can drift or supra-erupt, preventing the permanent restoration from seating properly.

When an EFDA is checking the marginal fit of a newly fabricated provisional crown, what is the ideal characteristic they should be looking for?

Answer: A smooth, snug fit with no gaps or ledges at the finish line.

A well-fabricated provisional crown must have a precise marginal fit. The margin should be smooth and adapt closely to the preparation's finish line without any gaps, ledges, or overhangs. This prevents plaque accumulation, gingival irritation, and leakage, which are crucial for maintaining periodontal health while the permanent crown is being made.

An EFDA is providing post-operative instructions to a patient after cementing a provisional crown. Which instruction regarding flossing is correct?

Answer: Slide the floss out to the side (buccally or lingually) after passing it through the contact.

To prevent dislodging a temporarily cemented crown, patients should be instructed to floss carefully. After guiding the floss through the contact point, they should pull it out from the side rather than snapping it back up through the contact. This technique minimizes the vertical forces that could lift the provisional restoration off the tooth.

Which of the following materials used for provisional crown fabrication is known for its high esthetics, good strength, minimal setting shrinkage, and low exothermic heat reaction during polymerization?

Answer: Bis-acryl composite resin

Bis-acryl composite resins are widely used for provisional restorations because they offer a combination of favorable properties, including excellent esthetics, good strength, low polymerization shrinkage, and a minimal exothermic (heat-releasing) reaction compared to traditional acrylics like PMMA.

During the fabrication of a custom provisional crown, a matrix or stent is created before the tooth is prepared. What is the primary purpose of this matrix?

Answer: To serve as a mold for the external contours of the provisional crown.

A pre-preparation impression or matrix (often made of alginate or silicone putty) is taken to capture the original shape and contours of the tooth. After the tooth is prepared, this matrix is filled with the provisional material and reseated in the mouth. It acts as a mold, defining the external shape of the provisional restoration, which significantly streamlines the fabrication process.