provisionals indirect technique

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Crest® Oral-B® at dentalcare.com Continuing Education Course, February 21, 2012

The days of being “just” a dental assistant are gone. As we continually strive to learn new things and improve our skills, the role of a dental assistant changes. In many states, laws concerning dental assistants are changing and the dental assistant is now able to perform more, such as fabricating provisional crowns and bridges. With this growth comes new responsibilities.

This course is designed to teach dental assistants how to fabricate provisional crowns or bridges. The term provisional also can refer to an interim or temporary restoration. Learning the techniques, materials, and procedures should give you a better understanding of what it takes to fabricate a provisional restoration.

Conflict of Interest Disclosure Statement• The authors report no conflicts of interest associated with this course.

ADA CERPThe Procter & Gamble Company is an ADA CERP Recognized Provider.

ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry.

Concerns or complaints about a CE provider may be directed to the provider or to ADA CERP at:http://www.ada.org/prof/ed/ce/cerp/index.asp

Cynthia M. Cleveland, CDA; Angela D. Allen, CDA; Niki Henson, RDA, AS

Continuing Education Units: 3 hours

Fabrication of Provisional Crowns and Bridges

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OverviewThe days of being “just” a dental assistant are gone. As we continually strive to learn new things and improve our skills, the role of a dental assistant changes. In many states, laws concerning dental assistants are changing and the dental assistant is now able to perform more, such as fabricating provisional crowns and bridges. With this growth comes new responsibilities.

This course is designed to teach dental assistants how to fabricate provisional crowns or bridges. The term provisional also can refer to an interim or temporary restoration. Learning the techniques, materials, and procedures should give you a better understanding of what it takes to fabricate a provisional restoration.

Laws and regulations concerning dental assistant duties vary from state to state. In many states fabricating and seating provisional crowns or bridges could be considered an expanded function and additional state approved education may be required. Always refer to the State Dental Practice Act before performing any of these functions.

Learning ObjectivesUpon completion of this course, the dental professional should be able to: • Explain the purposes and importance of a well-fitting provisional.• Compare the three techniques available for making provisional crowns and bridges.• Summarize the advantages and disadvantages of each technique.• Identify the procedure and material best suited for the needs of the patient and your practice.• Describe the appropriate protocol for each procedure.• Discuss special considerations for fabricating the provisional.• Compare and contrast problems associated with making provisionals directly and indirectly.• Show the steps of the vacuum adaptation method.• Explain the importance of assessing the patient’s needs.• Recite the post-operative instructions given to the patient.• Describe the polishing procedure.• Identify ways to keep the patient comfortable while managing the fabrication of the provisional.• Consider potential concerns of the patient and how to address them.• Explain how to facilitate the setting of stone and acrylic.• Describe the cementation procedure and its importance.• Understand the materials available for fabrication of provisional crowns.

Course Contents• Glossary• Importance and Purpose• Provisional Crown and Bridge Materials Bis-acrylics Acrylics Pre-Fabricated

• Techniques Advantages/Disadvantages Direct Techniques Polycarbonate Crown Form Technique Wax Technique Alginate Paint Thin Shell Technique Free-hand (Block) Technique Preformed Metal Crown Technique

Aluminum Shell Technique Pre-fabricated Light-cured Composite Crown

Technique Acrylic Preliminary Impression Technique Composite Resin Preliminary Impression

Technique Vacuum Form Acetate Shell Technique Reline Previous Crown Technique Celluloid Crown Form Technique Indirect Techniques Indirect/Direct

• Advanced Techniques Inlay and Onlay Provisional Technique Provisional Over Implant Technique Long-term Provisional Technique

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Abutment For Partial Technique Laminate Provisional Technique

• Finishing Procedures Trimming Trimming Recommended Materials Initial Trimming Try-In Stage Final Trimming Polishing Polishing Recommended Materials

• Cementation Excess Cement Removal

• Post Operative Instructions• Arranging Appointments• Conclusion• Course Test• References• About the Authors

Glossary Abutment – a tooth, root, or implant used for the support or retention in a fixed removable prosthesis.

Acrylic – an organic resin from which various types of dental restorations, prostheses and appliances are constructed.

Bridge – a fixed prosthetic device consisting of artificial teeth (pontics) that are supported by attaching them to abutment teeth.

Buccal – of, or pertaining to, the cheek.

Contact – the point on the proximal surface of a tooth where it touches a neighboring tooth.

Contour – the shape, form or surface configuration of an object.

Copolymers – two or more different monomers.

Crown, clinical – the portion of the tooth visible in the mouth above the gingiva.

Cure, dual – hardening of a material brought about by both self-curing and light curing.

Cure, light – hardening of a material in response to exposure to a curing light.

Cure, self – hardening of a material in response to mixing two chemicals together.

Curing – the act of polymerization of a chemical compound.

Distal – away from the midline.

Embrasure – a V-shaped space in a gingival direction between the proximal surfaces of two adjoining teeth.

Exothermic – the heat given off during a chemical reaction.

Facial – of, or pertaining to, both the labial and buccal surfaces of the teeth.

Flash – the excess material that extrudes beyond the intended margins of a restoration or a mold.

Gingival Margin – the most coronal portion of the gingiva surrounding the tooth.

Gingival Sulcus – the shallow furrow formed where the gingival tip meets the tooth enamel.

Homogenous – having a uniform quality and consistency throughout.

Hypertrophy – abnormally large growth.

Incisal – of, or pertaining to, the biting edge of an anterior tooth.

Labial – of, or pertaining to, the lip.

Lingual – of, or pertaining to, the tongue.

Mesial – toward the midline.

Monomer – one unit.

Occlusion – the contact of the posterior maxillary and mandibular teeth when brought together.

Polymerization – the conversion of low-molecular weight compounds called monomers to high-molecular weight compounds called polymers. The process of curing a material to change it from a plastic to a rigid state.

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Phonetics – pertaining to speech.

Polymer – organic molecules of high molecular weight, made up of many repeating units.

Pumice – ground volcanic ash that is used for polishing.

Undercut – the portion of a tooth that lies between the height of contour and the gingiva. Also, recessed areas in the surface cast.

Viscosity – the property of a liquid that causes it not to flow easily.

Importance and Purpose Provisional restorations are used as a short-term or interim (medium-term) step. They aid in diagnosis, treatment planning and communication to the laboratory for the clinical success of definitive fixed restorations. They may also provide coverage and support during periodontal treatment including implant therapy in developing the morphology of perio-implant periodontal tissues, over strategic extraction sites, during grafting techniques, furcation and endodontic treatment, and serve as a guide for the final restoration. Changes can be made during this phase to correct esthetics, phonetics, and function. The provisional may only be required for two to six weeks, or in some situations, must remain in a satisfactory condition in the oral cavity for twelve to eighteen months.

It is important to provide protection for the teeth during these times. The provisional must be properly fabricated and cemented. The treatment performed reflects the entire dental practice. Therefore, when a provisional is esthetically pleasing, remains intact, cemented and is comfortable, you have gained much more than a well-fitting provisional.

There are five basic purposes for a provisional. Each purpose relates both to the individual tooth or teeth and the patient as a whole.1. Protection of tooth and/or restoration – The

provisional provides protection for the tooth from the time of preparation until the final crown is cemented.

2. Tissue conditioning and healing – The provisional restoration can be used to assist

the gingival tissue in establishing good contour, and with the healing process. Ideally, the tooth should not be prepared more than 1/2 mm under the gingiva unless it is necessary for retention, esthetics, or function.

3. Esthetics – The provisional crown can act as a “rough draft” for the dentist and patient to discuss the appearance of the permanent crown. After wearing the provisional for some time, the patient may request changes to the final crown. Changes may include color, shape, length, embrasure, and many others. Provisional crowns allow the patient to become accustomed to the new shape, contour, and length if these were altered for cosmetic or functional purposes.

4. Maintaining Space for New Restoration – The provisional restoration is responsible for maintaining space for the final restoration. The provisional must touch the tooth to the mesial and distal of the prepared tooth as well as the opposing tooth. This contact will help reduce, and hopefully prevent, the adjacent teeth from moving. If the provisional is too small and does not provide adequate contact, the adjacent teeth will move into the open space. When the restoration is complete and ready to be seated, it may be too tight or not fit at all. An accurately sized provisional, both mesially and distally, will also prevent food from being trapped between the teeth. Trapped food can cause gingival inflammation, pain, and infection.

5. Function – Function is one of the most basic purposes of a provisional crown. The patient needs to be able to eat (on a modified diet) during the period of time he/she is waiting for the permanent crown. Occlusion should be slightly lighter than traditional occlusion to allow the pulp and periodontal ligament (PDL) to heal after the procedure.

With these five primary purposes in mind, evaluate the tooth, surrounding tissues and teeth, and identify any special circumstances. Use this knowledge to determine the best material, fabrication technique, necessary adjustments, cementation, and post operative instructions for the patient’s provisional restoration.

Provisional Crown and Bridge Materials Today, we have many choices of materials to

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Figure 1. Properly Trimmed ProvisionalCourtesy of 3M ESPE

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fabricate a provisional crown and bridge. We can choose from the traditional self-cured acrylic polymers, or the more advanced light-cured or dual-cured resins, as well as pre-fabricated provisional crowns.

Provisional materials can be categorized as follows:I. Bis-acrylic

a. Dimethacrylate- identified as:i. bisphenol A-glycidyl methacrylate (BIS-

GMA)ii. urethane dimethacrylate (UDMA)

II. Acrylics a. Methal Methacrylate (MMA) b. Ethyl Methacrylate (EMA) c. Polymethyl methacrylate (PMMA) d. Polyethyl methacrylate (PEMA)

III. Pre-Fabricated a. Metal (Ion)

i. stainless steelii. aluminumiii. anodized goldiv. tinv. tin-silver

b. Polycarbonate c. Light-cured methacrylate composite crown

There are many advantages and disadvantages to each of these common materials. You should thoroughly investigate the brands you are interested in before you discuss using a new material with your dentist. Be ready to discuss the pros and cons of using different materials and/or techniques.

Bis-acrylicsAmong the possible materials available are composite fillers such as dimethacrylate, identified as bisphenol A-glycidyl methacrylate (BIS-GMA), or urethane dimethacrylate (UDMA). These materials are classified as Bis-acrylics.

Bis-acrylics are multi-functional methacrylate esters filled with glass and/or silica particles. Bis-acrylic materials are popular because of their easy manipulation and comfort for the patient. They produce minimal odor, heat and shrinkage during the polymerization process. Shade variations are somewhat limited, ranging from two to five shade options.

Materials that are compatible with composite resins, such as Integrity® by Dentsply Caulk or Protemp™ Plus by 3M ESPE, are available in an automix cartridge. This can open up the door to an almost perfect color match. These materials are polymerized either by being chemically activated or visible-light activated. Chemically activated materials are packaged as a catalyst and base. They must be stored in two separate containers and mixed just prior to use. Many of these materials are dispensed in an automix cartridge. The automix cartridge prevents operator error, allows for easy clean up and avoids unnecessary waste (Figure 2).

Directions for some chemically activated bis-acrylic materials recommend utilizing a pressure pot for the final cure (Figure 3). Examples of these chemically cured materials are Ultra Trim® by The Bosworth Company and BIS-Jet® by Lang Dental Manufacturer. Provipoint® by Ivoclar Vivadent is a dual-cured material and so is TCB Dual Cure® by SciCan. Radica® by Dentsply also uses a tri-ad oven to fully cure the material.

The final stage of curing using a dual-cured material can be achieved by self-cure or light-cure. Light curing the material will reduce setting time by half. Initial polymerization is achieved by mixing the catalyst and base together. When you are ready for the final set, you expose the material to a visible-light curing machine. Light-activated materials must be stored in a light-proof container to prevent the material from polymerizing prematurely. An example of this type of material is Revotek LC® from G C America.

Figure 2. Automix CartridgeCourtesy of 3M ESPE

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AcrylicsTraditional acrylic resins are also known as Methal methacrylate (MMA), Ethyl methacrylate (EMA), Polymethyl methacrylate (PMMA), and Polyethyl methacrylate (PEMA). These materials have been used in dentistry for many years. Self-cured acrylic polymers, which are chemically activated, require a liquid (monomer) and powder (polymer) that are mixed to a fluid consistency.

Exothermic reactions are part of the polymerization process of polymethyl methacrylate. The larger the amount of this material used, the larger the exothermic reaction. Completion of the curing process is increased by this temperature rise and explains why frail, thin areas of cold-curing acrylic do not reach maximal hardness.

Polyethyl methacrylate materials have a longer working time between the initial and final set. They also produce a lower exothermic reaction. This material lacks resistance to abrasion, hardness and color stability. Using a pressure pot at 20 to 25 psi for 5 minutes will alleviate the hardness and color stability problem. Trim® from The Bosworth Company is an example of a polyethyl methacrylate acrylic resin (Figure 4).

Both of these acrylics are affected by the eugenol in provisional cements. This makes repair of the

acrylic difficult. To overcome this, lubricate the outer surface of the provisional before placing the cement inside. Different materials have different shrinkage rates. When acrylic polymerizes, the crown undergoes a shrinkage of approximately seven percent. If the final curing takes place without a supporting form, there will be distortion and a less optimal fit. A study of the marginal adaptation of provisional restorations found that the marginal fit of ethyl methacrylate provisional restorations can be improved by nearly 70 percent by fabricating them using the indirect technique (see Technique section).

When using acrylics, we recommend that you submerge the provisional in water if it is kept outside the mouth for an extended length of time.

Pre-FabricatedPrefabricated provisionals come in a variety of materials. They can be used for anterior or posterior, and are often used when a preliminary impression is not possible. Metal pre-fabricated crowns are used in the posterior. They provide good coverage, strength, and fit best when the interior is customized. Stainless steel as a provisional crown will last longer (in most cases) than the other materials. Metal crowns come in a variety of sizes and are grouped by type of tooth. For a slightly more esthetic posterior provisional, the tooth colored methacrylate composite crown should be used. Polycarbonates are anterior prefabricated anterior crowns. They may be used alone, with acrylic to customize the interior, or as a template to create a preliminary impression.

All characteristics of a material should be acknowledged and proper steps taken to prevent any undesirable post-operative sensitivity or

Figure 3. Pressure PotCourtesy of The Bosworth Company

Figure 4. PEMA - Monomer and PolymerCourtesy of The Bosworth Company

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pulp pathology. With the proper knowledge, an assistant can safely utilize these materials.

TechniquesThere are many techniques available to provide provisional coverage for teeth while you are fabricating permanent restorations. The type of provisional needed, condition of the gingiva, desired outcome, and any special circumstances all should influence which technique you choose. There are three basic techniques we will explore in this text: direct, indirect, and a combination of the two.

The direct provisional technique is where a provisional restoration is made inside the patient’s mouth. The indirect technique uses a model to fabricate the provisional (outside of the patient’s mouth). The indirect/direct technique utilizes both techniques.

Advantages/DisadvantagesThe indirect technique has advantages and disadvantages. When a patient reports a previous history of tissue irritation after a provisional crown was fabricated directly, you can decrease the possibility of sensitivity by utilizing the indirect technique. You would also use the indirect technique to fabricate a multiple unit bridge. This allows the patient to be comfortable while the bridge is being constructed. It also allows better visibility of margins, contours and contacts. By using this technique, you can allow the material to completely set on the prepared model. The indirect technique does, however, require several additional steps. These additional steps result in increased chair time and materials. The indirect technique is preferred over the direct technique for pulpal protection and accuracy. The use of acrylic monomers and polymers on a freshly cut tooth can be an irritant. The tooth has probably already had a large restoration, may have additional caries and has been subjected to the trauma of a high-speed handpiece.

The direct technique decreases chair time and material, however the patient is more uncomfortable because the mouth has to stay open while the provisional is being fabricated. The patient may be subjected to the unpleasant aroma from the materials and to the injurious effects of the placement and removal of the

provisional until final set is achieved. If the restoration is not removed from the tooth during the curing process, it may be necessary to destroy the provisional in order to remove it from the preparation.

The indirect-direct technique is usually chosen when multiple units are involved. This allows for relining at the chair with minimal contouring and improved esthetics. This technique requires preliminary work, additional chair time and laboratory costs.

All three techniques described have advantages and disadvantages. In consultation with the dentist, an assistant who knows these procedures and the associated effects can choose an appropriate technique to meet the needs of the patient.

Direct TechniquesThe direct technique is performed by making the provisional directly in the mouth. It is usually chosen when a single unit or small span bridge is being fabricated. It is cost-effective to fabricate the provisional directly and requires less chair time.

Using the direct technique can be quite simple. For instance, choosing a polycarbonate crown form for an anterior tooth and relining it with acrylic will save time since it is not necessary to take impressions, pour models or make a template. There are numerous ways to fabricate a provisional utilizing the direct technique. The most common ones are the polycarbonate crown forms, alginate impressions, preformed crowns, clear matrices and baseplate wax.

Polycarbonate Crown Form TechniqueA polycarbonate crown is a tooth-colored plastic form that comes in a variety of sizes. This technique may only be used for single units. The technique described does not involve using the crown form by itself, but requires relining it with acrylic. You can, however, use a preformed acrylic crown without relining, if it is properly trimmed and cemented with a provisional cement (Figure 5).

Hints• Keep the plastic tab on the polycarbonate

crown form until it is ready to be trimmed. This will help in trying in and removing the crown form during fitting.

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Alginate Paint Thin Shell TechniqueThis technique utilizes an alginate impression prior to the tooth preparation. If you cannot obtain an impression, you cannot use this technique.

Free-hand (Block) TechniqueYou can choose the freehand technique when you have become more skilled at making a provisional. No matrices or impressions are used with this technique. It allows for good marginal adaptation and proper occlusion.

Preformed Metal Crown TechniqueAluminum, gold anodized and stainless steel crown forms all fall into this category. They come in a variety of sizes for premolars and molars. They can be used by themselves, relined with acrylic or a combination of both. These crown forms cannot be utilized for multiple units. They can provide all the requirements of a well-made provisional when prepared properly. The technique

• Do not allow the acrylic to completely set on the model or prepared tooth. This will cause the provisional to lock onto the preparation.

Wax TechniqueThis technique can be used to easily fabricate all single unit provisionals. No crown forms or alginate impressions are necessary, which make this technique fairly inexpensive.

Figure 5. Polycarbonate Crown FormsCourtesy of www.doctorspiller.com

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Aluminum Shell TechniqueA posterior tooth can be protected by an aluminum provisional crown. These are available in a wide range of sizes. Always remember that crowns tried and not used must be sterilized before reuse. You may need to use a millimeter ruler to determine the size, measuring the mesial-to-distal distance.

Hint• If you don’t reline the aluminum crown with

acrylic, cement it using IRM or Zinc Oxide Eugenol (ZOE).

Pre-fabricated Light-cured Composite Crown TechniqueThese crowns are malleable, light cured,

utilized for these crowns is a bit different than what you may be used to. The gold anodized forms seem to work the best for this technique because of the softness of the material (Figure 6).

Figure 6. Preformed Metal CrownsCourtesy of www.doctorspiller.com

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preformed, and are available in a variety of shapes and sizes. They are a simple and esthetic solution for posterior provisionals. These types of tooth-colored pre-fabricated crowns can be quickly adjusted prior to light curing. With no impression or matrix needed, fabrication is quick and relatively easy (Figure 7).

Hints• Start with the smaller size crown, as it can

easily be contoured to modify to a slightly larger size.

• Trim the crown short, rather that leaving it too long.

• The tack cure should be no longer than 2-3 seconds per surface.

Figure 7. Pre-fabricated Light-cured Composite Crown FormCourtesy of 3M ESPE

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Composite Resin Preliminary Impression TechniqueThis procedure requires an accurate impression prior to and after the tooth preparation. If the tooth is broken down, or a bridge is being constructed to replace a missing tooth, this technique may not be effective without adding wax to those areas.

Hint• Select the provisional material that is the

closest to the natural tooth color. You can

Acrylic Preliminary Impression TechniqueThis procedure requires an accurate impression prior to and after the tooth preparation. If the tooth is broken down, or a bridge is being constructed to replace a missing tooth, this technique may not be effective without adding wax to those areas.

Hint• Always remember to place the provisional

on and off during setting to prevent locking provisional on the tooth.

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• Provides a smooth, void-free surface that gives a better finish to the surface of the provisional.

• Can be used with self- or light-cured materials.• Is inexpensive to produce.

Reline Previous Crown TechniqueAn existing crown can be used as a provisional if it remains intact upon removal and is smooth and aesthetically pleasing. When a crown is removed or remade, keep in mind the reasons

adjust the color by mixing colors or by adding a veneer of flowable composite to the exterior of the provisional after adjusting.

Vacuum Form Acetate Shell TechniqueThis procedure utilizes the vacuum forming machine. It allows you to duplicate existing teeth prior to preparation. However, it also duplicates broken or missing portions of the teeth. Therefore, after the alginate is taken and poured, you should repair any existing discrepancies prior to using the vacuum former. If a tooth is missing, there are many ways to fill the space prior to making your template. They include: use of an acrylic tooth (denture tooth), use of a mix of acrylic formed using opposing model to establish occlusion, and the use of light-cured resin to form a tooth (Figure 8).

The clear matrix has the following advantages:• Allows easy access and visibility throughout

the procedure.• Can serve as a tooth preparation/reduction

guide.

Figure 8. Vacuum Form Acetate Shell

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patient is not subjected to the unpleasant odor and taste of the acrylic resin materials, and the resin is allowed to completely cure under pressure on a cast of the prepared teeth. This results in a well-fitting, nonporous provisional restoration. The indirect technique is the most effective technique to fabricate a large multiple unit provisional.

Hints• Use separating mediums to prevent the

provisional material from sticking to the tooth or model. In most cases, a tooth moist with saliva will not allow the acrylic to adhere. It is a good idea to use the air/water syringe and, using the air, blow the excess separating medium off the tooth.

• When taking an alginate, apply a small amount of impression material to the critical areas before placing the tray. Make sure the teeth remain moist. If the teeth are too dry, the alginate will remain on the preparation and the impression will not be accurate. It is important to obtain an accurate impression so that the secondary retentive features, such as grooves, box forms and the gingival third of the perforations are accurately reproduced.

• Slurry water: To facilitate the setting time of the stone, slurry water can be used. You can sometimes obtain slurry water from the water residue of your model trimmer. Some model trimmers are set up in such a way that it is impossible to obtain slurry water. In such cases, you can make a solution of slurry water. You can use a plastic jug to save such water so it is on hand when needed. Always shake the bottle of slurry water before adding the water to stone. From start to finish, the setting time should be about 5 minutes. Work fast when using slurry water or the stone will start to set.

• Take care to avoid incorporating air bubbles into the acrylic, as air bubbles can cause voids in the restoration. When you use vacuum

for replacement. If it is for esthetics, you would want to make a new provisional. If it is because of poor fit, you can reline with acrylic to serve as a provisional. In most cases, it is best to make a new well-fitting provisional.

Celluloid Crown Form TechniqueA celluloid crown form can be used to fabricate a single unit provisional. It is extremely helpful when using light-cured materials because the material can be cured through the clear form.

Indirect TechniquesThe indirect fabrication of provisional restorations has several advantages over the direct technique. The main advantage is the patient does not have to keep their mouth open during the fabrication of the provisional. In addition, if acrylic material is used in fabrication, injurious effects of applying acrylic monomer to the tooth are eliminated, the

Figure 9. Vacuum FormerCourtesy of Keystone Industries

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Indirect/DirectWhen the doctor chooses to use the indirect/direct technique, he/she has chosen to have the labo-ratory fabricate a thin acrylic shell over mocked preparations that were done on a study model of the patient. This provisional shell will then be relined in the patient’s mouth. The laboratory

formed acetate templates, you should not see air bubbles. You can eliminate air bubbles by penetrating the template with a sharp instrument, such as an explorer.

• To ensure proper alignment of your core, you may need to make index marks using a permanent marker (Figure 10).

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Provisional Over Implant TechniqueTo fabricate a provisional over an implant, the assistant must be familiar with implants and their coordinating parts. We suggest using the indirect technique.

Long-term Provisional TechniqueProvisional crowns may have to be fabricated to last several months. In such instances, metal bars or a mesh material may be used to help provide durability. For an anterior provisional, the material should be placed on the lingual surface; for posterior teeth, the material should be placed on the occlusal surface.

Placing mesh prior to pouring material can be very difficult. The mesh may move during the pouring process and be in the wrong position while final set occurs. For the inexperienced, it is easier to cut a long groove in the occlusal or lingual surface. Then place the bar or mesh and cover with material.

indirectly fabricates the provisional on the model and the doctor or assistant relines it directly in the mouth, giving the technique its name. Refer to steps 3 through 8 in the polycarbonate technique.

Advanced TechniquesOnce an assistant has mastered the single unit and multiple units, he/she can move on to more challenges, such as fabricating a provisional over an implant or fabricating a provisional as an abutment for an existing partial. The following are a few advanced techniques.

Inlay and Onlay Provisional TechniqueAn inlay and onlay should be fabricated by a proficient assistant. This technique requires skill to achieve good marginal adaptation. The small size and intricate margins require precise fabrication and trimming. This technique closely relates to the freehand technique discussed earlier. The only difference with this technique is that the whole clinical crown is not covered.

Figure10.Figure 11.

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composite temporarily. This technique is rather simple, but does tend to stain around the edges over time. Make sure to tell the patient that this can happen. When a patient is aware of what to expect, there will be no phone calls to ask questions later.

Finishing ProceduresFinishing a provisional crown or bridge takes skill using materials and a proper slow speed technique. This entails correct positioning of the handpiece in relation to the area being trimmed. A well-finished provisional will provide a smooth and an esthetically pleasing appearance.

TrimmingAn operator must have general knowledge of proper handpiece operation, including how to correctly position the handpiece in relation to the area to be trimmed. Check state regulations for laws or rules regarding assistant permitted duties to see if you are permitted to adjust intraorally.

When trimming margins, place the cone-shaped acrylic bur parallel to the crown, but avoid disturbing contact points. A cone-shaped bur has a sharp point for definition and a large base

Hint• Before placing the material over a metal bar

reinforcement, make sure the bar will not interfere with the patient’s occlusion.

Abutment For Partial TechniqueWhen making a provisional as an abutment for an existing partial, use a free-hand or custom-made technique. This will allow for proper clasp placement, rests and correct size. This technique requires some practice. It also requires a skillful eye to know how much and where to trim.

Laminate Provisional TechniqueDepending upon the length of time between preparation and cementation appointments, a provisional may be placed. If the laboratory can process the laminate within a week, a provisional might not be necessary.

For multiple units, the provisional is made using a matrix and acrylic. However, laminate provisionals tend to come off frequently and you should cement the final restoration as soon as possible.

For single units, the doctor can etch a few spots on the facial and you can form and place the

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Final TrimmingTrim excess again and adjust occlusion using articulating paper. At this point you should check:• margins to make sure they are closed and

there are no overhangs.• for proper contours.• occlusion with articulating paper. Confirm

fit by asking patient how it feels. If it feels strange, make adjustments.

• for any irregularities that might make the provisional uncomfortable.

PolishingThe polishing of a provisional crown is an important step. A non-polished crown will have a rough surface which can cause plaque to build up. This is especially dangerous around gingival margins. Periodontal problems can result from a non-polished crown. Because of the constant movement of the tongue, the patient may also become uncomfortable if the surface is rough.

Polishing Recommended MaterialsYou will need a sterile rag wheel and pumice.

To use the dental lathe:1. Moisten the rag wheel and place it on the lathe

mandrel.2. Cover the tray with aluminum foil and place the

pumice on top.3. Mix a small amount of water with the pumice

in a dappen dish or small paper cup to make a thick consistency.

4. Make sure the protective plastic shield is in position and the operator is wearing personal protective equipment (PPE) and turn the machine on low.

5. Using gloves, coat the provisional with pumice, and secure your grasp on the crown. Use care because a rag wheel can cause overheating and warpage during polishing.

6. The incisal edge or occlusal surface should be facing you. With a back-to-front motion, run the provisional along the bottom side of the rag wheel. Carefully turn provisional to polish all sides except the contact areas. When you use all acrylic resins, take care when polishing so as not to buff away margin areas.

7. Replenish the provisional with pumice when necessary.

8. Once you have completely polished the provisional with pumice, place a dry rag wheel

for bulk reduction. A larger bur will be easier to maneuver since it requires less revolutions and/or vibrations.

Trimming Recommended MaterialsStraight handpiece using the following attachments:• Diamond disc for separating teeth and opening

the embrasure areas.• #8 bur for hollowing out prior to relining or

removing any internal imperfections and reduction in occlusal height.

• #35 bur to help define anatomy on the occlusal surface.

• Long, pointed acrylic bur to define embrasure areas and final contours.

• Carbide egg shaped bur to adjust occlusion.• Cone-shaped acrylic bur for bulk reduction and

initial trimming of margins.

Initial Trimming1. Determine your margins first. You may mark

the margins with pencil to clearly identify them. Start with a cone-shaped bur and trim close to margins. Continue until all margins are clearly trimmed. Margins should be trimmed to 1 mm. The margins must remain thin and intact.

2. When constructing a multiple unit provisional• Change burs to a separating disc, such

as a diamond disc. Start by separating the teeth following the original lines on the provisional.

• Separate and open the embrasure areas.• To shape further, switch to a cone shaped

bur.• Use the long, pointed acrylic bur to further

open your embrasure areas from the buccal and lingual. This is best done on the prepared model. This will help you see any additional trimming and shaping that you will need to do.

Try-In StageTry the provisional in the mouth at this point. It may be necessary to remove additional undercuts internally, which may prevent the provisional from seating properly. A #8 acrylic bur is sometimes used to hollow out the inside of the crown. Close marginal discrepancies by using a small brush, powder and liquid to fill the deficient areas when using acrylic.

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4. Continue polishing using increasingly less coarse discs until the provisional is smooth.

5. Use your gloved finger to feel for any sharp edges, and look closely to observe any significant texture change.

6. For an ultra smooth finish, follow the sandpaper discs up with a composite polishing cup or disc without without polishing compound.

7. For an extra touch, brush on a light glaze (such as Luxa Glaze) and light cure.

CementationRemember that eugenol containing cements can interfere with the setting of acrylic and prevent bonding of the final restoration. This may become important if repairs are needed. Cements that are light-cured and dual-cured are also available.• Isolate the area with cotton rolls and/or 2 x 2’s

and keep area dry. (Use air/water syringe to blow dry tooth.)

• Mix the cement according to directions.• Coat the inside of the crown with cement. (Be

careful not to overfill the crown. This could result in improper placement and the need for excessive cement to be removed).

• Request patient to bite down.

Excess Cement RemovalInsuring all excess cement is removed is important to the health of the gingiva. If all the cement is not removed, the gingiva can become irritated and inflamed.• When the cement has set, use an explorer

to remove the excess along the margins and contacts.

• Use the air/water syringe to keep the area clean and give you a view into the gingival sulcus.

on the lathe and add polishing compound to the turning rag wheel. Completely polish the provisional with the compound.

You can do the same technique utilizing the slow speed and laboratory handpiece. This also provides a high shine. You also may use a glaze to provide a high gloss. If the provisional restoration is on an anterior tooth, the patient may insist on a close color match. This can be accomplished with stains and glazes after the provisional has been polished. Minute stains cure and bond to all dental resins, including ethyl and methyl methacrylates, polycarbonates, vinyl methacrylate copolymers, resin crowns and laminates.

To Use Sandpaper Discs:1. This technique is typically only used for tooth

color composite resin based materials, but can be used in with other materials.

2. Beginning with the most coarse disc, attach the disc to a mandrel (Figure 13).

3. Using the slow speed handpiece, lightly polish any areas of the provisional that were rough or had been adjusted with a handpiece.

Figure 12. Dental LatheCourtesy of National Dental Supplies

Figure 13. Sandpaper DiscsCourtesy of Shofu Dental

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should also avoid chewing on the side of the provisional for a few hours. This will allow some materials, such as cements, to fully set. During the time the provisional is in place, the patient should avoid sticky foods, such as gum, caramel and taffy. Instruct the patient to contact the office as soon as possible if the provisional becomes dislodged. In the meantime, the patient can place a little petroleum jelly in the crown and place it back on the prepared tooth. It is always important to give post operative instructions to the patient both verbally and in written form.

Arranging AppointmentsIt is important to establish a routine technique for provisionals, so you can determine how long to make appointments. To achieve the desired results in provisional therapy, the dentist must allot adequate time to fabricate the interim restoration. You should allow adequate time to prepare the teeth and make a final impression.

A properly trained assistant can take over the role of fabricating and cementing the provisional restoration. Appointment times must be altered to accommodate these changes in staff and roles. The dentist/assistant time with the patient must be shortened and assistant-only time be lengthened. This time will include time for final cementation and clean up after fabrication of provisional.

Once a routine has been established, a designated amount of time should be allotted for each unit of the provisional. During this time, utilizing an assistant, the dentist can be performing another procedure, making full use of his/her talents.

ConclusionThe provisional restoration is an important stage in the prosthetic treatment. It must provide a suitable means for an provisional restoration. It is the responsibility of the dentist and dental assistant to provide the best possible coverage with the minimal amount of discomfort, and to meet the criteria for a well fitting provisional.

• Take a piece of floss and pass it down through the occlusal contact and out the buccal or lingual. Do not remove the floss through the contact area. If cementing a bridge, you need floss threaders.

• Take a wet cotton roll and wipe crown clean.• Instruct the patient to bite down to see how it

feels.

Hints• If it feels high, the provisional may not be

seated correctly or the occlusion may not have been adjusted properly during try in. To see which is the case, check your margins. If they are open, you have not seated the provisional correctly. In this case, remove the provisional, clean out the cement and repeat the process. If the margins are closed, the provisional is seated properly, but the occlusion is high. Mark it with articulating paper and have your dentist adjust the height. This should only take a few minutes to do. It should, however, be avoided by checking your occlusion several times before cementation. Make sure to have the patient bite down several times and slide teeth from side to side to check for proper occlusion.

• Coat the outside of the crowns with petroleum jelly before placing the cement internally.

• Tie knots in the floss. This will help remove large pieces of cement interproximally.

• Tie floss around the pontic of a bridge and make a loop prior to cementation. This will avoid the need for floss threaders. Make sure to tie the floss loosely and have the ends easily accessible so it can be untied and manipulated for cleaning cement under the pontic areas of a bridge.

Post Operative InstructionsInform the patient to continue brushing the area as usual. Good home care is essential. Flossing is necessary, but the floss should be pulled through the buccal or lingual. The patient should use a floss threader to floss under a bridge. Pulling the floss through the contact can help prevent the crown from dislodging. The patient

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Course Test PreviewTo receive Continuing Education credit for this course, you must complete the online test. Please go to www.dentalcare.com and find this course in the Continuing Education section.

1. The indirect technique is preferred _______________.a. for cost effectivenessb. for efficient use of timec. for pulpal protectiond. because of a low shrinkage rate

2. Light activated materials should be _______________.a. stored in a warm roomb. stored in a dark containerc. mixed welld. fluid in consistency

3. A good provisional should provide _______________.a. stabilityb. provide occlusal functionc. promote temperature changesd. Both A and B

4. Margins that are impinging on the gingival tissue can cause inflammation, resulting in _______________.a. gingival recessionb. hemorrhagec. hypertrophyd. All of the above.

5. Exothermic reaction increases when _______________.a. used with increasing amounts of acrylicb. using light cured materialsc. working time is increasedd. the final set has occurred

6. Provisional materials include __________ cured.a. chemicallyb. lightc. duald. All of the above.

7. When determining your margins, you should _______________.a. start trimming right awayb. take a lead pencil and outline your marginsc. look for bubbles or discrepancies in the provisionald. allow the material to set completely

8. When polishing with a lathe, make sure _______________.a. a sterile rag wheel is usedb. the protective shield is downc. PPE is wornd. All of the above.

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9. The switch(es) left on during the “suck down” stage when using a vacuum former is(are) the ____________.a. heat switchb. vacuum switchc. Both A and Bd. None of the above.

10. Pre-Fabricated Light-cured Composite Crowns are complicated to fabricate. Prefabricated Light cured Composite Crowns need an impression and matrix for fabrication.a. The first statement is true. The second statement is false.b. The first statement is false. The second statement is true.c. Both statements are true.d. Both statements are false.

11. Dental assistants should _______________.a. choose their own materials and techniquesb. consult the doctor when choosing materials and techniquesc. not talk to the patient during the procedured. not worry about the characteristics of materials

12. Post operative instructions should include _______________.a. telling the patient to floss regularlyb. instructing patient to snap the floss through the contactsc. not to change dietd. not to brush area involved

13. The setting time for the stone mixed with slurry water should take approximately ____________.a. 10 minutesb. 3 minutesc. 2 minutesd. 5 minutes

14. Bis-acrylic materials are popular because there is _______________.a. minimal odorb. easy manipulationc. minimal shrinkage during polymerizationd. All of the above.

15. An explorer is used to _______________.a. remove air bubbles from the template during the pouring of acrylicb. remove the template off the modelc. mix the acrylicd. Both A and C

16. During the try on stage, you should _______________.a. be concerned if you break the preparations off the modelb. be concerned if the provisional does not seat properlyc. force the provisional in placed. cement the crown

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17. A provisional may remain in the oral cavity for _______________.a. two to four weeksb. two weeks to eighteen monthsc. four weeks to one yeard. two years

18. When using the indirect technique, a vacuum formed matrix must _______________.a. be trimmed along the marginb. fit exactly on the model of the prepared teethc. rest on the frenumd. include three or more teeth mesially and distally

19. The bur that would not be used in trimming a provisional bridge is the ____________.a. #330b. #35 acrylic burc. #8 round burd. diamond disc

20. Diamond discs are used for _______________.a. trimming the margins of the provisionalb. placing anatomy on the occlusal portion of the provisionalc. separating the teeth of the provisionald. polishing the provisional

21. Bis-acrylic materials _______________.a. produce extreme heat during polymerizingb. are cost effectivec. have a wide range of shadesd. produce minimal heat when polymerizing

22. The pressure pot should be pressurized to _____ p.s.i.a. 32b. 20c. 10d. 5

23. Traditional acrylics _______________.a. are affected by eugenolb. have a 7% shrinkage ratec. produce an exothermic reactiond. All of the above.

24. Polishing is important because _______________.a. it allows for ease of cleaning of the provisionalb. it aids in placement of the provisionalc. a non-polished provisional would be roughd. Both A and C

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25. Traditional acrylic resins are also known as _______________.a. polyethyl methacrylateb. polymethyl methacrylatec. monomer and polymerd. All of the above.

26. A provisional crown or bridge is also called a/an _______________.a. temporary restorationb. immediate restorationc. interim restorationd. Both A and C

27. A long span and long term provisional bridge should be _______________.a. cemented permanentlyb. reinforced with metal or meshc. removed periodicallyd. None of the above.

28. Esthetics is considered one of the five basic purposes for a provisional. Prefabricated provisionals should only be used in the posterior.a. The first statement is true. The second statement is false.b. The first statement is false. The second statement is true.c. Both statements are true.d. Both statements are false.

29. When cementing the provisional _______________.a. it is not necessary to flossb. you should not dry the teethc. use a plastic instrument to remove cementd. instruct the patient to bite down

30. Bis-acrylics are _______________.a. composite fillersb. diamethacrylatesc. BIS-GMAd. All of the above.

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References1. Anusavice KJ. Phillips’ Science of Dental Materials, 11th Edition. W. B. Saunders, (2003).2. Berry T, Troendle K. Provisional restorations. Guidelines for proper selection, placement. Dent

Teamwork. 1995 Nov-Dec;8(6):25-31.3. Craig RG, O’Brien W, Powers J. Dental Materials. Missouri: Mosby-Year Book Inc., 6th Edition,

(1996): 60-69, 267-277, 286-289.4. Clinical Research Associates Newsletter, Provo, Utah, February 1997, Pg. 3.5. Dietz-Bourguignon E. Materials and Procedures for Today’s Dental Assistant. Thomson/Delmar

Learning, 2006.6. Dofka CM. Dental Terminology. Thomson/Delmar Learning, 2000.7. Frederick DR, George Taub Products & Fusion Company, Pamphlet on Stains and Glazes.8. Miyasaki-Ching C. Chasteen’s Essentials of Clinical Dental Assisting. Missouri: Mosby-Year Book

Inc., (1997): 290-298, 304-311.9. Anderson PC, Pendleton AE. The Dental Assistant. 007 ed. Thomson/Delmar Learning, 2001.10. Phinney DJ, Halstead JH. Delmar’s Dental Assisting: A Comprehensive Approach. 3rd ed. Albany,

NY: Delmar Learning/A part of Thomson Corp., 2008.11. Reisback MH. Dental Materials in Clinical Dentistry. Massachusetts: PSG Publishing Co., (1982):

259-279.12. Robinson DS, Bird DL. Ehrlich and Torres Essentials of Dental Assisting. 4th ed. Philadelphia:

Elsevier/Saunders Publishing Company, 2007.13. Bird D, Robinson D. Torres and Ehrlich Modern Dental Assisting . Pennsylvania: W. B. Saunders,

(2009): 694-702.

About the Authors

Cynthia M. Cleveland, CDACynthia Cleveland graduated from the Dental Assisting Program at Robert Morris Junior College in June 1976. She obtained her Expanded Duties through Broward Community College. Working with many doctors through the years, she has gained a tremendous enjoyment for fabricating provisionals and learned techniques from all of them. She has particularly benefited from the knowledge that Dr. Gene Tonn has shared with her. She assisted Dr. Tonn in presenting the course for making provisionals at Broward Community College. For the last two years she has worked hand in hand with Angela Allen to present this same course to Dental Assistants through the Continuing Education Department at Broward Community College.

Angela D. Allen, CDAAngela Allen is a graduate of the Dental Assisting Program at Broward Community College. She has worked with numerous general dentists from whom she has gained valuable experience. She is currently working for the Dental Assisting and Hygiene Programs at Broward Community College. She has worked with Cynthia Cleveland for the past two years providing hands-on experience to dental professionals in the fabrication of provisional crowns at Broward Community College.

Niki Henson, RDA, ASNiki Henson is a graduate of North Harris College. She is the President of Cornerstone Dental Academy where she authored the curriculum and provides continuing education to dentists, hygienists, and dental auxiliaries. She travels as a speaker, consultant, and presents a variety of seminars and clinical programs including provisional workshops at dental meetings across the country.

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