STEP BY STEP MODEL PREPARATION FOR THE LABORATORY ASSISTANT

Handling The Impression Disinfection:

1. Take suitable precautions to disinfect the impressions before working with them and wear gloves. This should effectively cut the risk of disease transmission to the laboratory assistant.

2. All impressions should be very well rinsed and cleaned with Tubulicid Red [Temrex] to remove the smear layer, as well as any blood or saliva, etc. that may be present. Failure to do so will compromise the quality of the stone pour. Thoroughly rinse away the Tubulicid Red because it will inhibit the set of stone.

3. Alginate must be poured within a very few minutes, so the lab assistant must work quickly. For this material, spray the impression with Birex SE [Biotrol] then rinse thoroughly. Excess water can be blown out using minimal pressure. Disinfectant left in the impression will cause an improper set of the stone pour.

4. Master impressions made with VPS should be checked either under the microscope or with powerful loupes for accuracy as well as potential defects. With very fine tweezers, remove any loose unsupported tags of impression material apical to the margins, which could droop over during the stone pour and compromise the stone margin.

5. After disinfection with Birex SE, spray the impression lightly with Debubblizer [Delar] and tap out any excess. Vigorously shake out (5 shakes) Debubblizer, leaving a light film for stone to flow better.

Pouring the Die Models:

1. Measure stone and liquid carefully. Measured amounts gives greater control in producing die models of consistent quality.

2. Completely dry mixing bowl with paper towel, then add 20.0 ml. of distilled water.

3. Add 100.0 gm. of Resinrock [Whip Mix], mixi quickly by hand spatulation. Then vacuum mix for 80 seconds at greater than -0.8 atmosphere.

4. Use a vibrator to assist in flowing stone into the prep areas first working from one side of the impression to the other. The vibrator should only be set high enough to facilitate the flow of stone through the impression. Use a small instrument, such as a number 7A wax spatula, to give more control over filling the impression. Work quickly but carefully. Drizzle the stone in and watch as one prep after another fills from the bottom up. Be very careful not to trap any air bubbles. If air bubbles appear use the instrument to quickly lift them out of the fluid stone material.

5. When the entire impression has been filled with stone tilt it on the vibrator so that most of the stone flows out of the impression and away from the preps. This flushes out the excess fluid rich stone. Debubblizer rich stone will harm the accuracy and detail of the model.

6. Use a larger spatula to fill the impression again. Stack it to about 3⁄4-inch thickness. This will allow sufficient strength to avoid breaking the model when it is retrieved.

7. Allow the impression to set up for 1 hour. Remove the model from the impression at that time and label it right away with the patient’s name, date and a number “1” (indicating the first pour) to avoid any mix up with subsequent pours.

8. Make a second pour using the same technique. This model will serve as a solid model on which contacts can be perfected. The

solid model will be used for accurate contacts and can as security in case anything should happen to the original die model. Follow exactly the same procedure used in the first pour. Pull the model after an hour and label it with the patient’s name, date and a number “2” on it. Alginate cannot be poured twice.

PREPARING THE DIE MODEL Model TrimmIng And Setting Dowel Pins:

1. Pull the die model from the impression. Trim the base on a model trimmer. Trim the first pour on the model trimmer to a thickness of about 10 mm with the base trimmed parallel to the horizontal plane of the case. To verify the correct plane of the base has been created, place the model (base down) on a flat surface and verify that the anatomical points chosen for the horizontal plane of the case line up perfectly on the Straight Smile Guide [Crown & Bridge UPDATE]. Trim the lower base parallel to the upper base. Avoid slurry water contact on the dies at all times because this will compromise stone quality. Stone dissolves in water and slurry water sediment sets up when the water dries out thus creating an inaccurate die.

2. Trim out the lingual area of the first pour model with an arbor band on a lathe. Trim the lingual flange at an angle of 45 degrees to add stability to the dies when the base is poured.

3. Use the Whaledent Pindex System [Coltene Whaledent] to drill holes for the dowel pins in the base of the die model. Place multiple pins for the unprepared teeth for adequate stability.

4. Each abutment prep, pontic and abutment will need 6 holes – one for the Knurled Dowel Pin and 5 for the reverse dowel pins [Gresco Products]. Pin the rest of the model for stability with multiple Knurled Dowel Pins.

5. Apply Insta-Cure [Devine Dental Supplies] to one of the holes drilled for the abutment prep or pontic. Put a knurled dowel pin in those holes so the shoulder of the pin is flush with the base. Allow glue to set for 15 minutes. Place Reverse Dowel Pins [Gresco Products] in the other holes. (DO NOT use glue in the other holes.) Glue pins knurled dowel pins in the rest of the model for stability of the unprepared teeth segments. Remove excess glue with a cotton swab.

6. Apply Isofix 2000 [Renfert/Denerica] to the underside of the model. Follow the manufacturer’s directions. This will act as a separating agent between the die model and stone base and will allow the dies to be easily separated from the base.

7. Attach Dowel Aids [Coopers Dowel Aid Products/Zahn] to each knurled pin. These will allow access to the end of the dowel pins after the base is poured and the dowel aids are removed.

Basing the models:

1. To create a base for the die model, prepare the following ingredients in a vacuum mixing bowl: 34.0 cc. of distilled water to 150.0 gm. of Die-Stone Peach [Modern Materials]. Mix this for 60 seconds under vacuum.

2. Use a very small spatula to apply stone to the underside of the die model. Be sure to get it in all of the retention grooves and between each of the dowel pins. Use a large spatula to apply larger amounts of stone to the underside of the model between the dowel pins. This should build up so that the stone is almost to the height of the dowel aids.

3. Scrape the remaining stone from the bowl and put it on a sheet of .150 Tray Material [Dental Resources].

4. Place the die model with the dowel aids down into the patty of stone and with a large spatula press the stone from the patty around the outer edges of the die model to form a good seal and

solid base. Use a spatula (not your finger) to smooth out the pink stone in the palate area. (Remember, now is the proper time to wash out the mixing bowl!)

5. Be careful during this whole process not to get any stone on your dies or on the margins! If this does occur, try to remove it immediately with a damp cotton applicator. Be extremely gentle with the dies.

6. Use a small spatula to scrape around the inner edge of the lingual surface where the die stone and the pink stone meet. Visualize this area in order to easily separate the base from the die model.

7. Clean around the area of the lingual surface again with a spatula for a very clean, smooth finish.

8. Allow the model to set completely for 1 hour.

9. After at least 1 hour remove the dowel aids.

10. Trim the base on the model trimmer parallel to the horizontal plane of the case as verified by a Straight Smile Guide.

11. Use an Arbor Band [Dentsply] to smooth off and give a final finish to the pink base. Examine the base and the first pour model to be sure that the juncture between die stone and base stone can be seen. If the juncture cannot be seen at any point, take a large size bur in the handpiece and smooth back so they can be seen.

12. At this point, put the patient’s full name and the prep date on the back of the model along with the number “1” to show this is the primary pour which has been based.

SAWING AND TRIMMING THE DIES

1. Examine the die and the opposing models very carefully. Using a quarter round bur, remove any occlusal blebs or imperfections on these models. These models must fit together perfectly occlusally or the restoration to be created will be incorrect.

2. Remove the dies from the base. Use h33C450 diamond discs [Axis] to saw from the apical of the dies toward the occlusal if vertical access is limited due to die proximity. Wear loupes to properly visualize the working area.

3. In dies that are too close together, remove that entire section and saw very carefully from underneath. A disc can also be used for this procedure. We use a #365220 [Brasseler] and a #911-400 [Diatech]. This must be done with the utmost caution as the preps are approached. If the dies break apart unexpectedly, it is possible to hit a margin or the die itself with the blade disc and damage it. Special care also needs to be taken not to damage neighboring teeth if they are going to be needed to establish contact.

4. It is best to wait 24 hours before final trimming the dies, because that is when the stone die has reached its maximum hardness. Use a special h-77ef.11.029 Bur [Brasseler] for this purpose and wear loupes or use a microscope to trim dies.

5. Create a slight ditch in the die beginning about 1 mm below the margin. Gradually work upwards slowly and carefully with the handpiece until the margin is clearly and cleanly exposed. Be extra careful not to knock off any little blebs of stone or chip off a questionable area in the margin. Go around these and go back to them later for trimming by hand or allow the dentist to do them.

6. Next, refine and trim the die by hand using a Bard Parker scalpel blade or Brasseler Miller small/medium spoon.

7. After the dies have been trimmed, be sure the model is clean and free of any dust or small plaster par- ticles. Clean out the dowel pin holes with a ball-point applicator or steamer and be sure, as the dies are put back in place on the model properly, that they seat 100%. Dies that are not seated perfectly on the model will cause a bridge to fit improperly and will cause the occlusion on crowns to be inaccurate.

REFRACTORY DIE MODELS 1. Coat the master dies with die-aid [Dillon Co.] and blow dry. This

hardens the die and protects it from chipping.

2. Apply 1 coat of die spacer pro art [Ivoclar] to the master dies using a #3/0 sable brush [Dentsply] under the microscope. For all ceramic restorations the coat of the die spacer is applied 1.0 mm short of the margin. An ultra smooth die is needed to make an all ceramic restoration of a refractory die, but a rough preparation adds to the longevity and predictability of the restoration. When die spacer is properly applied, both objectives can be achieved.

3. Apply the isolit die lube [Degussa] under the margin all around the die.

4. Clear master die dowel pinholes with air under high pressure and check to make absolutely sure that there is no debris present that could prevent the dies from completely and accurately seating. Seat the master dies in the master die model base.

5. Fill in between the stable and seated master dies with heated Thowax wax [Yeti Dental], using an ultra Waxer (blue tip #172-141 [Kerr]) electric waxing instrument [Almore] set at 400-450°F. Accurate seating of the dies is monitored under the microscope and throughout this process. Wax is applied under the lighted magnifier. After waxing out the saw cuts, the dies are once again checked under the microscope to determine whether they were displaced as the wax cooled. If the master dies are not

positioned precisely in the correct spatial relationship before the impression is made that will be used for the refractory dies, the refractory dies will also be in the wrong position. The mistakes that are made at this point in the process will be magnified exponentially later. For this reason it is important to take the time to stabilize the master dies properly.

6. Apply hot glue to “seal” the master model to the stone base. It is applied throughout the entire periphery, palatally and facially to prevent movement of the dies.

7. Spray the master die model with silfact impression lubricant and Conditioner [Gresco Products] to facilitate an even flow and easy removal of the duplicated impression material.

8. Soak the solid model (second pour of the master impression) in water for 2 minutes

9. Blow off excess water but leave it slightly moist which will prevent the vinyl polysiloxane putty from sticking to the model.

10. Measure two scoops each of white and orange elite hd impression putty [Zhermack] and mix together by hand without latex gloves. The set of the putty is inhibited when exposed to latex.

11. Place the putty in a stock impression Tray [Getz] that fits the model. A slight indentation is made in the putty, forming a lip over the edge of the tray

12. Press the moist solid model (second pour, not the master die model) into the putty to create an indentation that will serve as a custom tray effect when the model is immediately removed.

13. Inject light Body impression material [Zhermack] around the master dies and into the unset and indented putty in the tray – use a large volume. This impression material is preferred because its softness facilitates the withdrawal of the fragile refractory die material from the duplicate impression of the

master dies without chipping or fracturing in the process. By using a large volume of light Body, the impression is not damaged when the refractory cast is withdrawn. Consequently, a second refractory die cast can be easily made should the case need to be remade. With no damage, the second pour will be as accurate at the first. Be generous with the light Body material.

Seconds before use, the mixing tip is placed on the cartridge after is has been cleared. A “test” amount of the Light Body material is injected onto a paper towel for control purposes. Vinyl polysiloxane impression mate- rial is easily contaminated and will not be accurate if there is any unset material. The dies are meticulously injected so as not to create voids or bubbles. The occlusal surfaces of the master die model are also injected to provide a perfect impression of the occlusal surfaces of the previously spotted-in case. Future mounting of the refractory model is more likely to be correct as a result of this attention to detail.

14. Seat the master die model into the tray filled with unset putty and light Body material until the entire periphery is captured in the impression. Manipulate the putty with your fingers against the tray and into the undercuts of the tray to lock it into position. The putty must not pull out or off the tray when the cast is removed.

15. Let sit for 2 hours.

16. To remove the master die model from the impression, blow air under the periphery for easier removal. Be careful not to dislodge the impression material from the tray, in case a second pour is needed.

17. Spray the duplicate impression with Silfact [Gresco] and leave to soak for 2 minutes.

18. Mix 2 packages of G-Cera Vest White [GC America] with 12 cc of missing liquid in a Multivac vacuum mixing device [Degussa] for 30 seconds.

Do not mix longer than 30 seconds or the working time of the refractory material is shortened. The bowl, spatula, mixing blades and scouring pad are dedicated for use with refractory material only. If used with any- thing else, they will contaminate the refractory and such contamination will cause bubbles in the porcelain. After use, wash bowl, spatula and mixing blades immediately using dedicated scouring pad.

19. Blow excess silfact from the impression with clean and dry air while mixing occurs. The impression must be totally dry.

20. Pour the refractory material into the preps first without capturing any bubbles. Then fill the unprepared teeth. Support the impression in a horizontal position with a knife handle, and fill to the top of the edge to capture all of the anatomy of the master die model. The result is a thicker cast that is less likely to fracture when retrieved from the impression.

21. Allow to set 1 hour.

22. To remove the model after 1 hour, use a blast of air at the periphery to break the vacuum.

23. Trim the base of the model flat on a model trimmer avoiding slurry from the model trimmer on the dies. Rinse the model immediately after model trimming it.

24. Use a dedicated Arbor Band [Super Dent/Darby Dental] to rout out the lingual aspect of the refractory cast.

Arbor Bands used on stone casts will contaminate the refractory with stone and cause significant problems in fabrication. Treat refractory die models with a surgical-like cleanliness. Only the lingual aspect is trimmed, not the facial periphery. This procedure is performed under a magnified light. Human hands should never touch the refractory dies as oil produced by skin will contaminate the refractory material.

25. Fashion a 45° angle bevel on the entire lingual aspect of the base. This provides a positive seat and anti- rotation for the dies.

26. De-gassing stage 1 – place refractory cast on honey comb tray in a cold oven with the target temperature set to 700°C, with a rate of temperature climb of 35°C per minute.

27. Remove the honey comb with refractory model from the burnout oven when the target temperature is reached.

28. De-gassing stage 2 – Place the hot cast immediately in the porcelain oven. Start the oven at 700°C, with no vacuum, a temperature climb factor of 60°C per minute and a target temperature of 1060°C. Hold the target temperature for 6 minutes with no vacuum.

The model must not be allowed to cool between de-gassing stages. The highest temperature the cast will ever reach is during burnout. All porcelain firings must occur at a lower temperature that the de-gassing temperature.

29. After de-gassing and cooling, us a pindex laser pinsetter [Coltene-Whaledent] to place holes for the plastic reverse dowel pins. A minimum of 2 dowel pins (if lower anterior) are used for each prep die but 4-6 pins are needed for all other teeth for stability. Place several holes in the section of the cast where there are no prepared teeth (and hence will not go back into a porcelain oven) and glue brass pins in these holes using instaset [Sterngold Impla Med]. The non-prep section will have more stability with brass dowel pins and since they will not be fired, they can be used.

30. After the glue sets, coat the base of refractory model with a small amount of Vaseline so it can easily be removed from the base. Clean as much Vaseline as possible out of the reverse dowel pinholes using a Ball-point abdicators [Pinnacle].

31. Firmly seat pozi pins [Preat] in the holes. These are reverse plastic dowel pins that will stay in the stone base. The pin holes, not the pins, in the refractory go into the oven.

32. Mix Tru-stone [Heracus Kulzer/Darby Dental Laboratory Supply] with distilled water (125 gm to 30 cc water) for 80 seconds in the Multivac using the dedicated stone bowl.

33. Pour the stone directly into the pins for positive seating. Do not let the stone drool onto the periphery of the cast.

34. Seat the cast into a base former. Do not let the stone run up to the lingual aspect of the case, because it makes it difficult to remove the dies from the cast and it will block your view for determining if the dies are completely seated.

35. Let stone set for 30 minutes.

36. Trim the model on the model trimmer to get a smooth ledge. It is important to not get stone slurry on the refractory dies while trimming because it will contaminate the dies. Do not touch the dies with fingers.

37. Grind an “X” into the stone base supporting the refractory dies.

38. Mount the refractory to the opposing model using Mounting stone [Whip Mix], using glue, nails and a bite record if necessary.

If a bite record is needed to mount the case accurately, it is made in the laboratory while the case is mounted on the articulator. Inject occlufast [Zhermack] occlusal registration material [3M] between the opposing model and the already die-spaced master die model. The bite record that was made in the mouth will not fit the refractory die model accurately enough because of the addition of the die spacer to the master dies. The bite record made in the laboratory requires very little trimming because the refractory model is an exact replica of the die-spaced master die mode. The mounting of the refractory model that results is in the exact spatial relationship as the die-spaced

master die model. Any indexes, except soft tissue indexes, that can be used on the mast die model can also be used on the refractory die model, including, but not limited to, facial indexes; lingual indexes; incisal edge indexes; custom incisal guide tables; sectioned, but not segmented, indexes; soft shims; wax incisal guides etc. Soft tissue can be added to the refractory die model, but must be customized for the refractory model.

39. Saw the refractory dies with a large, double-sided diamond disk (#h340C-450) [Horico]. Remove the refractory model completely from the base to saw them.

40. Saw the dies partially through and then fracture the last few millimeter by hand. The fracture zone helps stabilize the dies mesiodistally and is invaluable to perfecting contacts on the refractory

41. Mark the margin with a VhT refractory marking pencil [Whip Mix] under a microscope.

42. Inscribe the tooth number with the VhT refractory marking pencil on the facial aspect of each die for identification during fabrication

43. Fire all parts of the pencil marked refractory die model at the same time to set the marks. Set the oven at 600°C with no vacuum and the temperature raise of 65° per minute to 1040°C and then hold for 3 minutes.

44. Cool the refractory model that now has precise marks for margins and contacts.

The ability to see the margin through the porcelain after it is fired makes the precise fitting of an all ceramic restoration less challenging. Refractory models made this way are easy for technicians to use and under- stand. Knowing where the margins must be placed, what the seating sequence must be and where the con- tacts should be located will make the technician’s job less difficult and the end product more predictable.

45. Form a lingual index to stabilize the dies. Mix Zetalabor platinum 85 [Zhermack] and smooth into the lingual areas of the base and against the lingual aspect of all the dies using an ungloved index finger to avoid latex contamination. Include prepared and unprepared teeth. Drape the most distal aspect of the putty over the model

46. After the lingual index sets, make a labial index that overlaps the lingual index. The 2 indexes do not stick to each other for some reason.

DIE MODELS TO THE OPPOSING Use of Study Models or Pre models

1. The use of an accurate study or pre model will enable the technician to establish correct occlusal relationships, prevent over-contouring, and guide in setting proper incisal edge position.

2. A good study model is essential in creating a successful anterior crown and bridge case.

3. Begin with accurate models that are free of blebs or imperfections, especially on the occlusal surfaces.

4. Set them together so that the teeth are in a solid centric relationship. If the bite is difficult to establish, have the doctor check it.

5. Lute the two models together with a nail on each side held in place with hot glue. Hold models together until glue has hardened.

6. Now the models can be mounted on the articulator. Follow the steps given in the next section.

7. If centric relation and centric occlusion are not coincidental – use a bite record to mount the case. This will require the use of a face bow and a centric relation bite record at an open vertical dimension of occlusion.

Trimming and Placing the Bite

1. Using a sharp Bard Parker blade, trim the bite record buccolingually so as to discard all bite record material that sits on unprepared teeth.

2. Now trim down the length of the bite record lingually and labially, leaving in view the registration of the cusp tips of the preps.

3. Trim away interproximal tissue areas and remove any blebs or imperfections.

4. On the opposing side, trim away bite material to allow full seating of the cusps.

5. Now try the bite on the die model. It should be perfectly flush to the preps and not held up anywhere. If the case involves a pontic area, remove that section of the die model and keep it in the case pan for now. Try not to use the bite over edentulous areas, as it will not be accurate. Try the bite record on the opposing model. It should seat fully and not rock.

6. When the bite seats cleanly on the die model, add the opposing model and hold together using firm pressure.

7. Visualize die model/preps, bite material and opposing model all sandwiched smoothly together with no voids.

8. Still holding the models together firmly, lute them in place using nails held in place with hot glue. Use 3 nails - usually one on each side and one in the back.

9. Do not release the pressure until glue is completely hardened! If not completely hardened, the bite will open slightly and be

inaccurate.

10. In some small cases, where the die model and opposing fit together in centric without using the bite, go ahead and lute the models together without using the bite record.

MOUNTING THE CASE Articulator and Rings

1. Keeping the articulator clean and functional is basic to preparing accurate crown and bridge work.

2. Knock the plaster off the rings with small hammer and lab knife. Soak them, if necessary, in a glass/plastic beaker of stone remover according to manufacturer’s directions. Rinse them well. (Some labs use a coat of Vaseline on the rings to make them easier to clean, but we find that the Vaseline can easily contaminate the models and dies.)

3. Use a firm toothbrush and a little water to scrub old plaster off the articulator and blow dry. A very light spray of liquid Wrench silicone spray [Gunk] on the moving parts will keep them functioning smoothly. For hard-to-reach areas, use cotton applicators dipped in alcohol.

4. Before articulating any case, check all settings and be sure they are in the normal position. Make sure the pin is set at the red line and all screw/fasteners are tight and in place. Rings should fit flush to the articulator.

5. Do not use an articulator that is not “up to par”, and discard any rings that have warped.

6. When mounting the case, use the straight smile Guide [Crown & Bridge UPDATE] to assure the horizontal plane of the case is correct.

Articulating the Models

1. Before the models have been luted together (i.e.: study model to opposing or die model to opposing) “key” the top and bottom with an “x” using a bur or lathe, and dampen these surfaces. This will enhance contact between the mounting plaster and the models.

2. Use a rubber mixing bowl to hand spatulate a small amount of mounting plaster (26 gm plaster per 100 ml distilled water) – Mounting stone White [Whip Mix] and tap water. Mixture should be firm enough to support the weight of the model. Stack the plaster onto the lower articulator ring and place model on top. Center model so facial midline is behind pin and posterior teeth are equidistant from condyles. Check case from side, being sure to create a normal mandibular angle. An accurate incisal plane relative to the horizontal plane is what should be accomplished in hand mounting without a face bow.

3. Working quickly, smooth away excess plaster with your fingers.

4. Allow lower mounting to set about 15 minutes before proceeding.

5. To complete mounting case, mix up more plaster as in step 2; stack it onto dampened upper model. Close the articulator until pin touches the table and plaster is imbedded in upper ring. Again, smooth away excess plaster with your fingers; allow case to set 15 minutes.

6. Break off the nails, clean off the excess glue with a lab knife, and “spot in” the case.

Spotting in the Bite

1. Loosen and raise the articulator pin.

2. Place a piece of red articulating ribbon between the teeth and tap the upper model firmly against the lower, moving the ribbon around the entire arch. Check the models - the red marks should be fairly uniform and even in color. Areas where the bite is heavy

can be relieved slightly using a small instrument. This should make the bite more even all around. Make sure the unprepared teeth adjacent to prepared teeth have contact to opposing.

3. After spotting in the bite, brush in Pledge FloorCare [Johnson] an even coat on both the master and solid models and opposing model but not on the die(s). Air dry. This process helps harden the models and prevent chipping.

4. When the bite is done, remove all the prep dies and examine them under magnification. Any under- cut areas should be blocked out at this time using Zapit [Dental Ventures of America] with a small instrument such as a probe. Spray with accelerator. Die spacer as necessary. Return dies to the model.

INDEXES

Soft Tissue models Using Kerr Soft Tissue moulage

1. Soft tissue models are usually utilized for all esthetic cases, anteriors, and bridges because they allow the technician to study the relationship between the restoration and the patient’s tissue. It will:

• Ensure the proper contour around papilla areas, embrasure spaces, and subgingival zones.

• Give assurance that metal will not show in critical cosmetic zones and that adequate room is avail- able for porcelain.

• Act as a guide for the exact contour of the metal in the subgingival zone to allow for negative con- touring of the porcelain in that zone.

• Guide in the precise location of connectors, precision attachments and necks of pontics. In short, when the technician can see the exact position of the tissue, he/she

can construct an appliance that will not impinge on soft tissue, yet will cover all the metal that could be seen in a cosmetic area.

2. Since the soft tissue model is created on the second pour model, it is wise to make a third pour to have on hand in these cases.

3. First, make an index by taking a platinum 85 [Zhermack] impression of the prepared teeth using the second pour model. Be sure to pick up the interproximal tissue and one or more of the unprepared teeth on either side of the preps as a stop for your impression.

4. When the putty has set, remove it from the model and check to be sure that all pertinent tissue has been registered.

5. Perforate only the buccal walls of the putty index with a bur to create small openings that can be used to inject the soft tissue silicone material. Try the index back on the trimmed first pour model to ensure proper fit and to check that the small openings are positioned over the trimmed (void) areas on the model. This will allow proper injection of the soft tissue material.

6. Lightly apply separator [Zhermack] that comes with the soft tissue packet to the inside of the putty index being sure to cover the prep areas, their surrounding soft tissue and the injection openings. separator acts as a release agent so the soft tissue silicone will not stick to the index. Wipe off excess separator .

7. Reposition the putty index on the trimmed first pour model. Make sure the model is sufficiently trimmed; end result will be a thicker, more sturdy soft tissue index. Inject the Gingifast [Zhermack] through the openings into the void areas on the model. Clean away any excess material from the injection openings. Allow the material about 15 minutes to set.

8. After the Gingifast has set, carefully remove the index from the model. The soft tissue material should remain in place on the

model and any excess material can be trimmed away. All pertinent gingival areas should have been picked up by the Gingifast, giving an accurate representation of the tissue.

Wax Incisal Guide

1. Warm two pieces of pink base plate wax and stack them together. Fold them in half so there are four thicknesses of base plate wax.

2. Warm the wax so it is flexible but not sticky and place it on a smooth counter top.

3. Force the model into the wax, being sure that all cusp tips and incisal edges are registered. Be careful not to over or under seat the model.

4. Allow the wax to cool. Trim the facial surface of the wax in a plane with the incisal/facial third of each individual tooth with a warm, sharp Bard Parker blade. A straight instrument such as a probe should lay flat on the facial/incisal third and flat on the facial aspect of the wax when this is done.

Express lncisal Guide

1. Mix a small amount of platinum 85 [Zhermack] according to manufacturers directions and quickly roll out to form a rope the length of the upper arch that will be worked on.

2. Wrap the rope of platinum 85 around the lower arch.

3. Quickly close the articulated model so that the articulator pin contacts the table, and the incisal edge/ buccal cusp tips of the upper model register in the platinum 85. Press it gently in place around the upper model.

4. Allow the platinum 85 to set about 10 minutes before reopening the articulator. At that time, carefully remove the platinum 85 from the model and trim the guide so that it fits snugly, but easily, on the

lower model. Then trim away excess on the maxillary surface, so just the very edges incisally are left.

5. After the guide is complete, remove the study/premodel and place the mounted die model on the articulator. With the guide in place and the articulator closed, the relationship between the preps and desired incisal position should be seen.

Custom lncisal Guide (study/pre model and opposing)

1. Release the articulator pin and raise it about 2 mm off the table.

2. To avoid chipping the models, seal them with clear nail polish or cyanoacrylate as necessary.

3. Make a putty out of enough tray acrylic and monomer (pantacrylic lncisal Guidance polymer) so it will not stick to your hands.

4. Put a ball of acrylic putty (about the size of a nickel) on the articulator table. Lubricate the acrylic with isolit [Degussa Dental].

5. Close articulator so pin registers in acrylic and slowly work models through lateral and protrusive excursions. The pin will register these movements in the acrylic.

6. After the acrylic sets, you can trim away any excess and leave the “ditches” created by the articulator pin clearly visible.

JOHNSON SCREW

Fabricating Lingual Silicone Index

Before beginning the wax up of substructure abutment and wing, a silicone putty index must be fabricated. Pre-operative or provisional models are suitable for silicone index purposes. platinum 85 [Zhermack] is the preference for this technique.

The putty is placed and manipulated along the lingual surfaces as well as partially along the occlusal surfaces. Extend the putty along adjacent areas to help lock in index. After a 5 minute setting time the index may be lifted from the pre-op or provisional model and transferred to working model. The index will need to be trimmed slightly at the location of the pontic to better see the lingual contour.

Measure 2.0 mm in from lingual contour of pontic and mark a line on the ridge with red pencil. That mark will be the lingual surface location of the wing. Note: lightly scraping the ridge before marking is recommended.

Fabricating Wax-Up Of Substructure

Remove the index and begin wax-up of the substructure abutment coping. Next begin wax-up of the wing starting at the red line of the ridge and connecting wing to the coping. Use a traditional lingual collar design on the coping and carry that over to a proximal guide plane design to establish path of insertion. The wing must have a slight taper from the ridge to the occlusal area. A slight mesiodistal convex design lingually is also recommended. The idea is to provide more substructure stability to the suprastructure.

Survey wax-up to verify parallel line of draw with suprastructure abutment. For added retention a lingual box may be cut into the wing. This is optional but is considered beneficial. The belief is you can never have too much retention.

To cut the hole into the wing wax-up, place the silicone index back on the model. Carefully cut a hole through the wing from the buccal

surface using the index as a guide to position the hole in the middle of the pontic. A number 2 round carbide bur works well for this procedure. Also, the large reamer in the Screw-Block attachment kit works quite well. It may be helpful to mark the index with a red pen for the purpose of an exact hole placement.

Spruce the wax-up with an 8 ga sprue on the coping and an 8 ga sprue on the wing. Sometimes the wing is large enough to require the use of a 6 ga sprue. Common sense sprueing technique applies here. Use care to flow investment through the hole in wing. Casting in precious or semi-precious metal is recommended.

Tapping threads into non-precious metal could be difficult.

Preparing Substructure metal For Suprastructure Fabrication

Divest and air-abrade casting with 50 micron aluminum oxide abrasive. Leave the casting on the sprue button.

Very carefully, under magnification slightly enlarge the hole through the wing with a sharp number 2 round carbide bur. This step is only to help minimize the difficulty in tapping threads.

To tap the threads the following will be useful:

1. A 1.4 mm x .03 mm micro cut tap [Attachments International].

2. A tap wrench [local hardware store]

3. All purpose lubricating oil (3-in-1 oil or Liquid Wrench).

Begin tapping threads with the cut tap, twist drill handle and liberal amounts of oil. Turn the tap using only 1/8 and 1/4 turns until most of the threads are cut. As the tap emerges from the other side, 1⁄2 and full turns may be employed until the tap is passed completely through. Carefully back the tap all the way out.

Ultrasonic clean the casting and remove from the sprue button. Finish down the sprues and fit the coping to the die. The wing must be rubber wheeled using a black silicone wheel. For the lingual retentive

box a red all-purpose occlusal access point followed by a green high-luster occlusal access point may be used.

All of the wheels and points used for polishing are available from Brasseler.

Fabricating Suprastructure

The objective in the fabrication of the lingual silicone index is to insure optimum placement of the Branemark gold hexagonal implant screw. The screw should be flush with the lingual contour of the pontic. Place the implant screw into the lingual surface of the wing. Position the coping, wing and screw assembly on the working model then position the silicone index. The screw will have to be adjusted until it touches the lingual contour represented by the index passively.

Upon completion of this step, measure the distance between the lingual of the wing and the screw head.

Remove the index as well as the gold hex screw, and then position a Branemark standard guide pin into the wing. Re-measure providing the same distance as with the gold screw.

Fill in the buccal side of hole with wax if the screw does not reach through the wing. Using GC Pattern Resin and a small brush, carefully manipulate a small amount of resin around the gap between the wing and guide pin and inside the retentive lingual box. GC Pattern Resin is available through local supplier. Allow pattern resin to set for 4 minutes.

Continue to build a pattern resin core covering the entire wing. Note: be sure that ridge area of the model is lubricated with die lubricant. The entire pontic may be designed using GC Pattern Resin. It is perfectly acceptable to slightly over-build and then cut back with various carbide burs.

The final stages of the pontic design may be in wax in much the same way a conventional bridge wax-up.

Note: It is important that the lingual of pontic around the screw access hole be designed with pattern resin. The lingual contour being made flush with the screw is better facilitated with the resin.

Personal preference in final contouring of lingual is to remove the guide pin, lift the pattern resin pontic from wing, and examine for resin over extension or flash at the finish lines. The core must fit the wing intimately when re-placed. Substitute the guide pin with the gold screw.

Note: The threads in the pontic suprastructure may be tapped using the cut tap to better facilitate reintroduction of the gold screw. The threads and the suprastructure pontic may also be eliminated using a number 2 round carbide bur and magnification to carefully cut them away. The personal preference here is the latter just simply because of mechanics. If the threads in the pattern resin pontic are to be removed, then it must be emphasized that only the threads and not the actual flange beyond the threads be compromised.

After the pontic fabrication is complete the abutment may be luted to the pontic in any desirable technique. Sprue the suprastructure in the indirect method. Remove gold screw, lift the bridge from the working model and place on a sprue former. It is advisable to place an 18 ga vent opposite the sprue on the pontic. Invest using care to flow the investment into the wing housing and out through the lingual access hole.

Cast, divest, remove from sprue button and fit abutment to the die and pontic to the wing. After both halves of bridge are adequately fitted, place and tighten gold screw.

Note: If there are threads still present in the pontic, they must be removed using a #2 carbide bur. In this case lubricating the threads already present is not necessary. Remove the pontic threads first, then assemble bridge with a gold screw.

With the gold screw in place the bridge may then be metal finished. Proximal and embrasure areas may also be finalized at this stage. Remove the gold screw, and bridge is ready for porcelain processing.

TECHNIQUES FOR

MICROSCOPIC CAST GOLD RESTORATIONS

Wax-up

1. Spot in articulated models

2. Block out all undercuts on die

3. Lubricate dies and contact areas

4. Mark margins with red pencil

5. Wax-up crown

6. Seal margin and cut back

Investing

1. Attach sprue to thickest area of wax-up

2. Remove wax-up from die, place on sprue former

3. Place ring on sprue former [Darby] small or large

4. Use (Micro Star Expansion Liquid) 14 ml liquid to 11 ml distilled H2O per Micro Star Investment powder.

5. Hand mix then spatulate under vacuum 60 seconds

6. Bench set for 18 minutes (for fast burnout)

Burnout and Casting

1. Scrape top of ring

2. Place ring in 1,600°F hot oven

3. Keep in oven 30 minutes (additional 10 minutes for each extra 100 gm.

4. Lower oven temperature to 1,150°F and leave for 30 minutes. Then cast.

5. Ready a 50/50 combination of used and new alloy for casting

6. Set casting machine with 3 turns and lock with pin

7. Remove ring from oven and place in casting machine

8. Push crucible toward ring

9. Light casting torch and adjust for proper flame -- 3-5 psi O2

10. Preheat crucible with torch until cherry red

11. Place used metal in crucible first and melt, then add new metal

12. Release pin and gently release casting machine arm while raising torch

13. Let casting machine spin until it stops

14. Retrieve ring and no quench – for inlays, let onlays and full crowns bench set.

15.

Divesting and Finishing

1. With an instrument, remove as much investment as possible

2. Lightly air abrade casting with 50 micron aluminum oxide

3. Separate casting from sprue and weigh casting

4. Finish down sprue

5. Fit crown on die, adjust contacts and occlusion

6. Finalize contact adjustments on solid model

7. Redefine anatomy and rubber wheel and rubber point entire surface

8. Polish crown with saphire polishing compound

9. Ultrasonic clean crown with ammonia, then steam clean

Wax-up Procedures

Before proceeding with crown wax-up, the spotting-in of articulated models is necessary. It is recommended that full upper and lower models be used. With articulating tape held between models, tap together while moving tape along entire arch. The occlusal contact points will be revealed. If some contact points appear too heavy while others barely register, scrape heavy areas lightly with an instrument. The models are properly tapped-in when even articulating tape registration around the complete arch is achieved.

With a very sharp instrument, preferably a sharp Bard-Parker number 25 blade, the cold carve technique will be used to seal the margins. Carefully, and with very little pressure, carve away the overextended wax to red margin line under the microscope.

After margins have been sealed, the bulk of wax above the margin may be carefully trimmed away with a 1/2 hollenback instrument. A piece of nylon stocking may be used to burnish the margin down to a fine knife edge. After burnishing, go back to microscope with wax-up and carefully lift wax-up just enough to reveal any over-extensions at the margin. Carefully carve away with Bard Parker and reburnish area.

Investing

Select a wax reservoir sprue ranging in size of 8 ga to 10 ga for full crowns and onlays and 12 ga for inlays. Choose the thickest area of wax-up to attach the sprue. Attach sprue without involving functioning cusp tips and contacts if possible. Keep sprue reservoir as close to crown as possible. Inlays such as a DO or MO may be sprued on the marginal ridge or the occlusal. Sometimes with inlays, distortion can occur during the pulling of wax-up from the die when sprued at marginal ridge.

The sprue length should be 10 to 15 mm to allow proper clearance from the top of the ring. Remove the wax-up and place on the sprue former, securing it with wax. Place casting ring on the sprue former to ensure the wax-up is 1/4” from the top of ring. Remove ring and line with asbestos-free liner. The liner must be 1/4” from the top of the ring, and the 2 ends of the liner must butt together, not overlap. The liner may be secured by a drop of sticky wax. Place the lined ring in water until moistened, then remove the ring without touching the liner so as not to compress it. Shake it, then set aside. Spray or paint wax-up with debubblizer, such as surfactant [Delar], and allow to dry. Light air-blowing may be used to hasten drying. Place the ring back on sprue former. Pour Novocast investment by Whip Mix into vacuum mixer bowl with premeasured distilled water. Inlays will require approximately 1 ml more water to assure proper expansion of investment, hence a better fit. Hand spatulate until blended then spatulate with vacuum mixer under full vacuum for 45 seconds.

Remove from mixer and carefully, with a small brush or instrument, flow investment in and around wax-up then slowly pour in investment until the wax-up is covered by 1/4”. Bench set invested ring for at least 1/2 hour, then scrape the ring.

Burnout and Casting

Place in a room temperature oven, and over a 40 minute period, bring the temperature to 1200°F for 3 hours, then cast. For onlays and full crowns, heat soak at 1200°F for 30 minutes.

The alloy to be cast should consist of 50% old and 50% new metal. Ultrasonic clean the old alloy in distilled water for 10 to 12 minutes prior to casting.

Wind the casting machine two turns and set with pin. Remove the ring from the oven and place in casting machine. Push the crucible toward ring. Light the oxygen/gas or propane torch and adjust oxygen to 3-5 lbs psi. Gas or propane should be adjusted to 10 lbs psi. With the proper flame, preheat a clay crucible in the casting machine until it is cherry red. Drop the old metal in crucible and heat until molten. Add new metal and heat until all metal is molten and begins to roll. Sprinkle borax flux such as Degussa Veriflux over molten metal to clean away surface impurities. As the metal begins to turn cherry red and develop a mirror surface. Pull back casting machine arm to drop pin, and gently release arm while raising torch.

Allow the machine to spin freely until it stops. Cast inlays may be quenched and onlays and full crowns should bench cool. If a type IV hard alloy has been used, allow the ring to bench cool.

Divesting and Finishing

Remove as much of the investment as possible with an instrument then lightly air abrade with 50 micron aluminum abrasive.

Remove casting from sprue, remove vent and weigh casting, then finish down sprue and vent area. Fitting the casting on the die is accomplished with 1/4 round, 1/2 round, and .700 fissure burs. All carbide burs are from Brasseler. The location of high spots and possible nodules dictates the type of bur used in fitting. The 1/4 round and 1/2 round work well in corner and side areas while the .700 fissure is ideal for the internal walls of inlays and onlays.

For ideal contact points mesially and distally a solid model should be used for final contact adjustment. After the first model is poured and pulled from impression, a second pour should be carried out. With this

second model, precise contact adjustments, as well as accurate gingival contours for subgingival castings may be obtained.

TECHNIQUES FOR PRESSED LITHIUM DISILICATE

Investing

1. Preheat Vulcan Burnout oven [Ney] to 1,600° F. Set program for e.max pressoven [Ivoclar].

2. Prepare sprued wax up and use 200 gram investment ring as per e.max instructions

3. Mix 22 ml distilled water with 32 ml of e.max speed liquid [Ivoclar] in bowl for crowns, veneers and onlays. Note: Use 27 ml distilled H2O with 27 ml e.max speed liquid for inlays.

4. Add 100 gm e.max pressvest speed powder [Ivoclar] to mixture in step 3. Mix with spatula by hand until all powder is absorbed.

5. Cover bowl and put into multi vac mixer for 120 seconds at 350 rpm.

6. Pour investment into ring to the top.

7. Set aside for 40 minutes.

8. Remove invest from the ring and dry scrape the top.

9. Grasp with tongs and place in Vulcan Burnout oven for 75 minutes with hole face down.

10. Prepare plunger (add separating power) and ingot on the cooling grid.

11. Remove investment from burnout oven. Within 30 seconds: Invert on to cooling grid, place ingot inside investment hole, add plunger on top and transfer investment into press oven.

12. Press start.

13. Remove ring from Press oven and place on cooling grid for approximately 60 minutes.

Divesting

After cooling to room temperature (approximately 75 minutes for 200 gm ring), the investment ring may show cracks.

These cracks developed during cooling (immediately around the Alox plunger), as a result of the different CTE of the various materials (Alox plunger, investment material pressed materials). They do not compromise the press results.

Divest the investment ring as follows:

1. Mark the length of the Alox plunger on the cooled investment ring.

2. Separate the investment ring using a separating disk. This predetermined breaking point enables reliable separation of the Alox plunger and ceramic material.

3. Break the investment at the predetermined breaking point using a plaster knife.

4. Always use polishing beads to divest the pressed objects (rough and fine divestment). Do not use Al2O3.

5. Rough divestment is carried out with polishing beads at 4 bar (60 psi) pressure.

6. Fine divestment is carried out with polishing beads at 2 bar (30 max psi) pressure. Note: glass beads must be an 80 micron and Al2O3 must be 100 micron (per Ivoclar).

7. Observe the blasting direction and distance to prevent damage to the object margins during divestment.

8. Remove possible ceramic residue at the Alox plunger with type 100 Al2O3.

Remove the Reaction Layer

After fine divestment, the reaction layer formed during the press procedure is removed using ips e.max press invex liquid [Ivoclar].

The procedure is carried out as follows:

1. Pour the invex liquid into a plastic cup.

2. Immerse the pressed object in the invex liquid and clean in an ultrasonic cleaner for at least 10 minutes and a maximum of 30 minutes. Make sure the objects are completely covered with invex liquid.

3. Remove the restoration from the invex liquid and clean the object under running water and blow dry.

4. Carefully remove the white reaction layer with type 100 Al2O3 max. 1-2 bar (15-30 psi) pressure.

5. Make sure that the reaction layer is completely removed, both on the cavity side and on the outer side of the object (repeat the procedure, if necessary).

6. If the reaction layer is not completely removed, bubbles may develop, which subsequently may lead to bonding problems and cracks in the layering ceramic.

7. Replace the ips e.max invex liquid after 20 applications or after sedimentation of the liquid.

Staining Technique

In the staining technique, the pressed restorations are completed by the application of stains (IPS e.max Ceramic Shades, Essence) and glazing materials. In this way, the use of translucent IPS e.max Press ingots permit the fabrication of very esthetic restoration on only slightly or non-discolored preparation with minimum effort.

Finishing

It is of critical importance to use the correct grinding instruments for finishing and adjusting high-strength glass-ceramics. If unsuitable grinding instruments are used, chipping of the edges and local overheating my occur (please observe the Ivoclar Vivadent Glow Chart "Recommended grinding tools for IPS e.max glass- ceramics".

Observed the following procedure for finishing IPS e.max Press restorations:

1. Even though adjustment by grinding of pressed ips e.max press restoration is possible, it should be kept to a minimum.

2. Wet the area to be ground and us a fine diamond disk to cut the sprues

3. Overheating of the ceramic must be avoided. Low speed and light pressure is recommended.

4. Smooth out the attachment points of the sprues.

5. Remove the spacer from the die. The restorations are tried in on the dies and carefully finished.

6. Do not "post separate" the framework connectors with separating disks. This may result in undesired predetermined breaking points, which will subsequently compromise the stability of the all-ceramic restoration.

7. Make sure that the minimum thicknesses are maintained even after the minor adjustments.

8. Check the occlusion and articulation and grind in the appropriate adjustments, if necessary.

9. Design surface textures.

10. To clean the restoration, briefly blast with Al2O3 at 1 bar (15 psi) pressure and clean with the steam jet.

11. Some blasting devices my require different pressure settings to accomplish this procedure.

Stain and Characterization Firing

The following paragraphs will explain the most important steps for staining and characterizing with IPS e.max Ceram Essence and Shade. For further information on the nano-fluorapatite layering ceramic and its processing, please refer to the IPS e.max Ceram Instructions for Use.

1. ips e.max Ceram shades [Ivoclar] are ready-to-use stains in syringes.

2. ips e.max Ceram essence are intensively shaded powdered stains which are mixed with ips e.max Ceram Glaze and stain liquid.

3. IPS e.max Ceram Glaze Paste is ready-to-use glaze paste supplied in a syringe.

4. IPS e.max Ceram Glaze Spray is a ready-to-use glaze spray.

5. IPS e.max Ceram Glaze Powder is a powdered glaze which is mixed with IPS e.max Ceram Glaze and Stain Liquid.

Before the Stain and Characterization firing, the restoration must be free of dirt and grease. Any contamination after cleaning must be prevented. The following steps must be observed:

1. For better wetting of the stain, a small quantity of IPS e.max Ceram Glaze and Stain Liquid my be slightly rubbed into the restoration surface.

2. Mix the paste or powder with the IPS e.max Ceram Glaze and Stain Liquids all round or long life to the desired consistency.

3. More intensive shades are achieved by several staining procedures and repeated firing, no by applying thicker layers.

4. To imitate the incisal area and translucency in the incisal third, IPS e.max Ceram Shade Incisal may be used.

5. The cusps and fissures can be individualized using Essence.

6. Conduct the Stain and Characterization firing using the indicated firing parameter.

ALGINATE IMPRESSIONS USING THE

GRASER TECHNIQUE 1. Pre measure powder into Poly-Cons [Markson Science] (plastic

containers with attached lids.) Tumble the alginate container to fluff powder and measure powder exactly. Store distilled water in a Portion Aid Dispenser [Almore Inc.]

2. Place rope wax on perforated trays to allow for full border extension.

3. Follow manufacturer’s instructions exactly for water powder ratio. To change setting time, either use different set alginate (i.e.: fast or

regular) or change temperature of water. Warmer water speeds set and colder water slows set. Use distilled water.

4. Set countdown timer and mix alginate in alginator for exact time specified in directions. Load tray and force alginate into the occlusal, facial, and lingual surfaces of the teeth and the embrasures with your fingers. Place tray in the mouth within time specified in directions.

5. Hold the tray motionless for the specified time. 6. Snap the impression from the mouth. Do not rock or remove slowly.

Using an air syringe under the anterior lip of the tray will “hydraulically lift” the impression out of the mouth very easily.

7. Rinse in operatory. Wrap in a wet paper towel. 8. Pour immediately. Do not store in water. Do not store for more than

3 minutes before pouring. Use Resin Rock [Whip Mix] to pour opposing models for all crown & bridge cases.

DISINFECTION OF IMPRESSIONS 1. All Hydrophobic Impressions - Thoroughly rinse in operatory

immediately upon removal from the mouth, using the 3-way syringe. Scrub the impression of the preparations and tissue areas with Tubulicid Red [Temerex]. Rinse thoroughly. Spray with Birex [Biotrol International].

2. Irreversible Hydrocolloid - Thoroughly rinse in operatory immediately upon removal from the mouth, and wrap in a moist paper towel. Spray with Birex [Biotrol International]. DO NOT SOAK.

STERILE TECHNIQUE FOR PUMICE PAN1. After each use, wash rag wheels, then autoclave or cold-sterilize in

cold sterile solution.

2. Keep several small Tupperware containers with covers partially filled with dry pumice on hand. Wet before using.

3. Discard pumice after each patient use. 4. Line pumice pan with plastic Tray Sleeve [Pinnacle] to catch

splatter. Change frequently.

STERILE TECHNIQUE FOR LAB BURS 1. After removing Provisionals from the mouth, scrub with Pure 4%

CHG [Best Buy Discount Dental Supply] and spray with Birex [Biotrol International] (10-1 dilution).

2. Set up lab burs in clean containers ready for next use. NOTE: Do not use gloves in the lab while grinding or using the rag wheels due to possible danger of gloves being caught in grinding equipment.

FABRICATION OF CUSTOM TRAYS 1. Adapt 8 layers of a wet paper towel over model for spacer. Add 4

layers more over the teeth to be prepared. 2. Remove paper sheets from ProCure Tray Material [Dental

Resources]. 3. Form tray material over spacers and model and trim excess with a

blade. 4. Excess is used to form a tray handle. 5. Place in light curing oven for 5 minutes. 6. Remove tray from model and pull out spacer. 7. Cut any excess material with lab handpiece and any crosscut bur. 8. Wash tray with soap and water to remove air inhibited layer. 9. Drill holes and slots in tray with a #H261 Ecarbide bur [Brasseler]. 10. For better retention, flatten the outside holes and slots with a

#H77-060 carbide bur [Brasseler]. 11. Dry tray thoroughly before painting tray with the appropriate

impression adhesive.

12. Mark the mid-line of the two centrals on the tray with a Sharpie pen. Carry the mark from the periphery of the tray onto the handle.