What is the purpose of proximal reduction in crown preparation?
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To permit the seating of the crown.
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What is the purpose of proximal reduction in crown preparation?
To permit the seating of the crown.
How is proximal reduction accomplished if a mesio-occlusodistal amalgam restoration is present?
By removing the amalgam in the boxes using a no. 170L or 171L bur.
What is the function of the measuring heads in the metal crown form kit?
To measure a 1.0-mm range and determine the dimension for selecting the proper crown form.
Why is the use of an alginate overimpression a popular technique in dental procedures?
Because it is always readily available in the dental operatory and easily adapted to intraoral use.
What materials can be used to make a thin shell crown or fixed partial denture?
Any of the acrylic resins.
What should be done if the gingival collar of the crown is too tight?
The crown should be placed on the appropriate post of the stretching block to obtain an adequate gingival flare.
What are the two methods for relining a thin shell crown or fixed partial denture?
Indirectly on a quick-set plaster cast or directly in the mouth.
What should be done if the tooth to be restored has obvious defects before making an overimpression?
The overimpression should be made from the diagnostic cast after filling and smoothing over the defects with red utility wax.
How is the occluso-gingival length of the crown evaluated?
By comparing the height of each marginal ridge of the crown with that of the adjacent tooth.
In what clinical situations might prefabricated provisional crowns be used?
When it is not possible or desirable to make a custom resin provisional crown, such as in emergency situations or when time is limited.
What type of methacrylate should be used if the reline is done directly?
A methacrylate other than polymethyl.
Why is the diagnostic cast immersed in water before applying alginate?
To keep the alginate from adhering to the cast.
What tool is used to smooth rough spots and irregularities in the gingival margin?
A sandpaper disk.
What materials are commonly used for prefabricated provisional crowns?
Polycarbonate or polymethyl methacrylate for anterior teeth, and preformed anatomical metal crowns for posterior teeth.
Why must care be taken not to make the shell too thick?
If too thick, the shell will not seat completely over the prepared teeth and will need to be trimmed internally, which can be time-consuming.
What is the purpose of trimming off excess alginate and thin flashes of impression material?
To ensure there are no impediments to the complete seating of the cast into the overimpression later.
How are open proximal contacts corrected during crown fitting?
By burnishing the proximal area from the inside of the crown.
Why is the indirect technique preferred over the direct technique for provisional restorations?
The indirect technique is preferred for its accuracy and better marginal fit.
What is a key consideration when using polycarbonate crowns for anterior teeth?
They often require extensive alteration to correct morphologic discrepancies and improper contours.
What is the purpose of using a plastic squeeze bottle with a fine tip during the overimpression technique?
To deposit one drop of monomer on the facial and one drop on the lingual surface of the imprint of each tooth to be restored.
What must be done to avoid locking into undercuts when using the direct technique for provisional restorations?
The resin provisional restoration must be removed from the tooth before it has completely polymerized.
What is applied to the outside of the crown to facilitate the removal of excess cement?
Petrolatum.
What can happen if polycarbonate crowns are not carefully contoured?
They can have horizontal overhangs that are damaging to the gingiva.
What tool is used to gently spray polymer onto the surface of the impression?
An insufflator (DeVilbiss Plastic Powder Blower, DeVilbiss).
What is the volumetric shrinkage of pure methyl methacrylate monomer when it polymerizes?
21%
What type of cement is used to seat the crown on the prepared tooth?
Zinc oxide and eugenol mixed to a thick, creamy consistency.
What should be avoided if the preparation is short or lacking in retention during provisional restoration?
Petrolatum should not be added.
How can the necessary retention and recontouring be achieved for polycarbonate crowns?
By relining the tooth-colored crown form with a resin on a quick-set plaster cast of the prepared tooth.
How should the overimpression be stored for later use?
It should be wrapped in a wet paper towel and placed in a resealable zipper plastic bag.
What is Protemp Crown and how is it used?
Protemp Crown is a malleable composite-based material that is anatomically preformed, adapted to the prepared tooth, and light cured.
What should be done if the shell binds when tried on the cast?
The inner surfaces of the shells should be relieved until the restoration seats completely and passively.
What type of resin is used to fabricate a provisional restoration on a quick-set plaster cast?
Bis-acryl composite resin (Integrity, Dentsply).
What did Crispin et al. show about the marginal fit of polymethyl methacrylate provisional restorations?
The marginal fit could be improved nearly 70% by fabricating them indirectly.
How does moisture affect zinc oxide-eugenol cement during setting?
Moisture accelerates the hardening.
How are the margins of the crown burnished before the cement hardens?
With an LL 6-7 curved burnisher.
What materials and tools are needed for making a provisional restoration with a polycarbonate crown?
Anterior sectional impression tray, alginate, rubber bowl, spatula, quick-set plaster, polycarbonate crown kit, pencil, straight handpiece, acrylic bur, coarse garnet disk, jeweler’s wheel, camel-hair brush, cement spatula, dappen dish, IPPA plastic instrument, separating medium, monomer and polymer, medicine dropper, muslin rag wheel, white polishing compound, Miller forceps, scissors, articulating paper, paper pad, zinc oxide-eugenol cement, petrolatum, explorer, mouth mirror, and dental floss.
What material is used to pour the quadrant impression after the tooth preparation is completed?
A thin mix of quick-setting plaster, such as Whip Mix mounting plaster.
What is a notable characteristic of bis-acryl composite provisional crown materials?
They exhibit brittleness and have a very short elastic stage, making it difficult to remove from adjacent undercut areas without fracture.
What is the benefit of using a pressure pot during the relining process?
It significantly increases the strength of the restoration.
What are the benefits of using bis-acryl composite resin for provisional restorations?
It produces very little heat during polymerization and has minimal toxic effects on soft tissues and the pulp.
What are the benefits of using the indirect technique for provisional restorations made from many resins?
The fit of provisional restorations can be improved.
What tool is used to remove hardened cement from the interproximal areas?
Dental floss.
What is the first step in the technique for making a provisional restoration with a polycarbonate crown?
Make an alginate impression of the prepared tooth using an anterior sextant tray.
What is the benefit of coating the outside of the restoration with petrolatum before cementation?
It aids in the removal of excess cement.
What should be checked on the trimmed quick-set plaster cast before seating it into the overimpression?
The occlusal surfaces and gingival crevices should be checked for any plaster nodules that will prevent complete seating.
What advantage does Luxatemp Solar Plus offer?
It provides an extended elastic stage and delayed light curing.
What should be done when the resin becomes rubbery during the direct technique?
The restoration should be elevated 2.0 mm, and the teeth under it should be flushed with water.
Why is it important to securely orient the cast in an upright position during the provisional restoration process?
To prevent distortion of the space between the cast and the impression filled with resin, ensuring uniform thickness of the provisional restoration.
What did Monday and Blais find about polyvinylethyl methacrylate crowns made indirectly?
They found better margins on polyvinylethyl methacrylate crowns made indirectly than those made either directly or by relining.
How is remaining subgingival cement removed?
With an explorer.
How is the proper mesiodistal size for the crown form determined?
Using the mold guide provided with the polycarbonate crown kit.
What tools are recommended for removing excess cement from the gingival crevice?
An explorer in accessible areas and knotted dental floss interproximally.
What is used to coat the prepared tooth and adjacent areas of the cast before mixing the acrylic resin?
An algin-based 'tin foil substitute' separating medium, such as Alcote.
What is the benefit of using VLC polymethyl methacrylate resin (Unifast LC)?
It allows user-controlled advancement from slurry through doughy and elastic stages to final cure.
What can happen if the cast is torqued to one side by the rubber band?
The cast may be forced through the soft resin in some areas, resulting in a provisional restoration that is thin in some areas and thicker than desirable in others.
Why is the indirect technique preferred for the protection of the pulp?
It avoids thermal and chemical irritation from the exothermic reaction and free monomer of polymerizing polymethyl methacrylate.
How should excess resin be trimmed from the provisional restoration?
With acrylic burs or coarse Moore disks.
What is done after selecting the proper size of the polycarbonate crown?
Place the crown on the prepared tooth on the cast or in the mouth and mark the gingival portion of the labial surface with a pencil.
Why should a provisional restoration for a fixed partial denture be in the form of a fixed partial denture rather than individual crowns?
It provides a better esthetic result in the anterior region and better stabilizes the teeth in the posterior region.
Which impression material is used for making a direct provisional restoration?
Polyvinyl siloxane (Extrude Extra, Kerr).
How is the tooth-colored acrylic resin prepared for the provisional restoration?
It is mixed in a dappen dish with a cement spatula, using twelve drops of monomer for each tooth being restored.
What materials are included in the armamentarium for creating provisional restorations?
Silicone impression putty, Triad resin, Triad model release agent (MRA), Triad air barrier coating (ABC) material, and Triad curing unit.
What is the effect of seating the cast with too much force or wrapping the rubber band too many times?
The cast may be forced through the resin occlusally, resulting in a provisional restoration with an occlusal surface that is too thin.
What are the advantages of using a heavy-bodied elastomeric material for impressions?
It is very stable and difficult to distort.
What are some key items in the template armamentarium for fabricating a provisional fixed partial denture?
Diagnostic cast, Mor-Tight putty, No. 7 wax spatula, denture tooth, crown form, vacuum forming machine, coping material, and temporary splint material.
What is critical when seating the cast into the alginate impression?
The force used to seat the cast; excessive force can overseat the cast, and uneven force can torque the cast, affecting the restoration.
What is the first step in the technique for creating a provisional restoration?
A template is fabricated on the diagnostic cast.
What is the benefit of allowing a polymethyl methacrylate provisional restoration to polymerize in a pressure pot under 20 psi?
It decreases porosity and increases the transverse strength of the restoration by 28%.
What is the purpose of filling embrasures with putty during the template technique?
To eliminate undercuts during adaptation of the resin template.
What are the disadvantages of using a heavy-bodied elastomeric material for impressions?
It is more expensive and requires extra time for the impression material to polymerize.
How is the template reinforced during the provisional restoration process?
A scoop of silicone impression putty is mixed with accelerator and molded around the template on the cast to reinforce it and prevent displacement by the highly viscous resin.
What indicates that the resin sheet is heated to the proper temperature?
It will droop or sag about 1.0 inch in the frame.
What types of resins are commonly used for making custom provisional restorations?
Polymethyl methacrylate, polyethyl methacrylate, polyvinylethyl methacrylate, bis-acryl composite resin, and visible light-cured (VLC) urethane dimethacrylate.
What tools are used to trim the excess resin from the provisional restoration?
Acrylic burs or coarse Moore disks.
What material is used to create the template in the vacuum forming machine?
A 5 × 5-inch sheet of 0.020-inch-thick resin (clear temporary splint vacuum forming material).
What is the purpose of trimming excess material from the borders of the impression?
To facilitate accurate placement back in the mouth.
What is the purpose of using Triad model release agent (MRA) in the provisional restoration process?
The cast is coated with a layer of MRA to facilitate the application of Triad resin around the finish lines of the abutment preparations.
What happens to the coping material when it is heated properly?
It loses its cloudy appearance and becomes completely clear.
What are the requirements for a good provisional restoration?
Appearance of a tooth where needed, physiologic axial contours adjacent to the gingiva, occlusion with opposing teeth, proximal contact, and marginal fit.
What should be done before attempting to seat the provisional restoration on the tooth?
All resin extending beyond the preparation finish line into undercut areas must be removed, and the axial surfaces near the margins should be smoothed with a fine sandpaper disk.
Why should the webs of material between the imprints of individual teeth in the impression be removed?
Because they could interfere with complete reseating of the overimpression.
How is the resin polymerized in the template during the provisional restoration process?
The cast is placed in the Triad curing unit to polymerize the resin in the template for 4 minutes, followed by additional curing after applying ABC material.
What is the first step after placing the cast in the center of the perforated stage of the vacuum forming machine?
Turn on the vacuum.
What materials are included in the cementation armamentarium?
Articulating paper, Miller forceps, straight handpiece, high-speed handpiece, No. 171L FG bur, muslin rag wheel, pumice, cement spatula, paper pad, zinc oxide-eugenol cement, petrolatum, explorer, mouth mirror, dental floss.
What materials can be used to shape the provisional restoration?
Both elastomeric and alginate overimpressions.
What is the purpose of cutting a trough in the gingival area of the facial and lingual surfaces of the tooth imprint?
To ensure adequate material in the margin of the resulting restoration.
What is the final step in finishing the provisional restoration?
The restoration is polished with pumice and a high-shine polishing material.
How long should the vacuum be left on after lowering the frame over the perforated stage?
Approximately 30 seconds.
How is the occlusion checked during the cementation of a provisional restoration?
The provisional restoration is seated on the tooth, and the occlusion is checked with thin articulating paper.
What is a benefit of using an elastomeric impression for provisional restorations?
It provides excellent stability.
What should be done before placing the resin if the core or adjacent restorations also consist of resin?
Petrolatum should be thinly applied to the prepared tooth and adjacent teeth.
What tool is used to cut through the resin after it is removed from the frame?
A laboratory knife with a sharp no. 25 blade.
What is the purpose of polishing the provisional restoration with damp pumice and polishing compound?
To make the provisional restoration easier to clean, more comfortable for the patient, and less likely to discolor.
How can a template formed from clear thermoplastic resin be used in provisional restorations?
It can be shaped on a diagnostic cast using a vacuum forming machine or an impression tray filled with silicone putty, then filled with resin and applied to the prepared teeth or a fast-setting plaster cast.
How long should the provisional restoration be allowed to self-cure?
7 minutes from the start of the mix.
What can be used to fabricate a template for a provisional restoration if a vacuum forming machine is not available?
A quadrant impression tray filled with Silly Putty and a sheet of coping material.
How should a provisional crown be fitted under an existing removable partial denture?
The crown should be undercontoured to avoid touching any rests or clasps, and resin should be added to the outside of the crown. The partial denture is lubricated with petrolatum and seated over the provisional crown to form the rest seat and guide planes.
What is a thin shell crown or fixed partial denture made of autopolymerizing resin used for?
It can be made in an impression prior to the preparation appointment and relined after the tooth or teeth are prepared.
What can be used to repair voids or deficient margins after the loss of the fresh surface of the provisional restoration?
Many light-cured flowable composite resins.
How can the cooling process be accelerated when using a silicone putty tray?
By blowing compressed air on the plastic sheet and the impression tray.
How is the strength of the temporary cement slightly reduced during the cementation of a provisional restoration?
By incorporating an amount of petrolatum equal to 5% to 10% of the cement volume into the mixed zinc oxide-eugenol cement.
What is the final step after contouring, finishing, and polishing the provisional restoration?
The restoration is seated with a temporary cement.
What should be done if the silicone putty sticks to the resin sheet?
Pull it off in quick jerks to exhibit brittleness and ensure easy removal.
What is the purpose of wrapping rubber bands around the template and cast?
To secure the template and cast, ensuring not to place them over the abutment preparations.
What should be done to the cast before adding acrylic resin for a provisional fixed partial denture?
Coat it with Alcote separating medium and allow it to dry.
Why is it important to protect the prepared tooth or teeth while a cast restoration is being fabricated?
To keep the patient comfortable and protect the tooth, gaining the patient's confidence and influencing the success of the definitive restoration.
What is the purpose of placing the cast in warm water during the polymerization process?
To hasten polymerization and prevent the monomer from boiling, which increases porosity.
What is another term for a provisional restoration?
Temporary restoration.
What should be done if there are voids or thin spots in the provisional restoration?
Add resin to the voids or thin spots and place the cast back in warm water.
What are the requirements for a good provisional restoration?
Pulpal protection, positional stability, occlusal function, ease of cleaning, nonimpinging margins, strength and retention, and esthetics.
What is the final step in trimming the fixed partial denture?
Use disks and burs to trim the axial surfaces down to the margins and open the proximal embrasures.
Why is pulpal protection important in a provisional restoration?
To prevent the conduction of temperature extremes and prevent leakage of saliva.
Why is a transparent template essential for using VLC resin?
Because the clear matrix allows light access to the resin to initiate polymerization.
What is the consequence of a provisional restoration not providing positional stability?
The tooth may extrude or drift, requiring adjustments or a remake of the definitive restoration.
What alternative resin can be used without a clear matrix for a VLC provisional restoration?
VLC urethane dimethacrylate putty stick resin (Revotek LC, GC).
How does occlusal function benefit the patient with a provisional restoration?
It aids patient comfort, prevents tooth migration, and possibly prevents joint or neuromuscular imbalance.
Why must a provisional restoration be easy to clean?
To keep the gingival tissues healthy and reduce the likelihood of problems after cementation of the definitive restoration.
What can result from a provisional restoration with impinging margins?
Gingival inflammation, proliferation, recession, or hemorrhage during impression or cementation.
Why is strength and retention important in a provisional restoration?
To withstand forces without breaking or coming off, avoiding time-consuming replacements and maintaining patient rapport.
In what cases is esthetics particularly important for a provisional restoration?
For anterior teeth and premolars.
What are the types of provisional restorations?
Zinc oxide-eugenol cement, provisional crowns, and provisional fixed partial dentures.
What are the two classifications of provisional restorations based on their fabrication?
Prefabricated and custom restorations.
What are some examples of prefabricated provisional restorations?
Stock aluminum cylinders, anatomical metal crown forms, clear celluloid shells, and tooth-colored polycarbonate crown forms.
What materials can custom crowns and fixed partial dentures be fabricated from?
Several different kinds of resins.
What are the two techniques for adapting provisional restorations to the teeth?
Direct and indirect techniques.
What is the direct technique for provisional restorations?
It is done on the actual prepared teeth in the mouth.
What is the indirect technique for provisional restorations?
It is accomplished outside of the mouth on a cast made of quick-set plaster.
Why might the direct technique be inviting to novices?
It eliminates the need for an alginate impression and plaster cast.
What is a potential drawback of the direct technique in restorative dentistry?
It can be technique-sensitive, especially if using a resin other than polymethyl methacrylate.
What should the gingival margin equal in provisional crown preparation?
The length discrepancy between the incisal edge of the crown form and the incisal edges of the adjacent teeth.
How is excess gingival length trimmed away during provisional crown preparation?
With a large carborundum stone or an acrylic bur, using a pencil line as a reference mark.
What is used to paint the cast of the prepared tooth and surrounding area?
A tin foil substitute separating medium (Alcote).
How is the drying of the separating medium accelerated?
With an air syringe.
What is used to fill the crown form with resin?
An IPPA plastic instrument.
How is the resin polymerization accelerated during provisional crown preparation?
By placing the crown form in a bowl of warm tap water.
What tool is used to trim away excess resin at the margins?
A coarse garnet disk on the straight handpiece.
What should be done if the tooth is nonvital or a resin other than polymethyl methacrylate is used?
The crown can be relined on the prepared tooth in the mouth.
How is the occlusion checked after placing the provisional crown?
With articulating paper.
What is used to polish all surfaces of the provisional restoration?
Polishing compound (Acrilustre) on a muslin rag wheel.
What is used to cement the provisional restoration?
Zinc oxide-eugenol cement.
What is a common challenge in fabricating a provisional restoration for a tooth prepared for a post and core?
There is often very little intact supragingival tooth structure.
What is used to provide temporary coverage for fractured molars in emergency cases?
Preformed anatomical metal crowns.
What are the steps involved in using a preformed anatomical metal crown?
What is the initial step in preparing a tooth for a preformed metal crown?
Occlusal reduction.
