For molding, I use a silicone based lab putty by Coultene (FIG. 22). It is faster and cheaper than a silicone casting material.

Coultene's Lab Putty comes in two parts, a putty and a paste (FIG. 23). I have always eyeballed the mixing ratios and have never had any problems. This is some really neat stuff. As I understand it, the folks over at Cinnovation thin this down to a pouring consistency and use it in various applications.

It can seem a little tricky and it may need some getting used to. Press the putty over the front of the cast with your sculpt and wrap it around over the top and onto the back (FIG. 25). Make sure to encompass the entire wax (or clay) sculpt.

With an exacto blade, cut through the midline (FIG. 27). I also will cut away any excess putty leaving one tooth on each side of the cap. Make sure you go two teeth back from the cap if you are using a lingual clasp on the 1st bicuspid.

With a wax sculpt, I can remove the wax easily from the cast with a little boiling water (FIG. 28).

There are quite a lot of dental stone separators out there. I got this small sample from JBC and I love it (FIG. 30). I go with two coats and this stuff works great! It won't bead up on wax, so if you used wax to block out any undercuts or imperfection in your cast, you won't have to worry about digging wax out of your acrylic casting.

FIG. 31 illustrates mixing the body acrylic monomer and polymer. Monomer is very bad to breathe so make sure that you have ample circulation and WEAR A RESPIRATOR! For this case we are using A-4. Again, I usually eyeball it. If you tend to mix a bit to thin, that's OK. You can wait a moment for it to start to kick.

In FIG. 32 you can see how thick I like to mix my body acrylic. A thicker mix will not only stay put but it will help to displace any air that otherwise could become trapped in the mold.

First, using a metal spatula or other small utensil, flow some body acrylic around the canine, in the interproximal areas and especially near the gum line (FIG. 33). This will help reduce the chance for air getting trapped in your casting.

Then spatulate some body acrylic into the putty negative. Work quickly here as the mix will begin to set up. Make sure you fill the mold with more acrylic than you will need.

Quickly push the negative putty mold down over the stone model positive (FIG. 35). You will know when the mold is seated by looking at where the putty meets the stone. Hold in this position for about 7 minutes.

Place the model into a bowl of cold water and let it set for half an hour (FIG. 36). This will give you a denser casting than if you let it bench set.

After carefully removing the putty negative, we are ready to make our incisal cutback. This is where the 'magic' happens. In FIG. 37, the red area is ground completely off, The violet area is ground back at a tapering angle (FIG. 38).

FIG. 39 After mixing the incisal acrylic, pouring it into the negative, etc., This is what we've got, ready for de-flashing and polishing. FIG. 40 shows the translucency of the incisal cutback.

Using a plaster knife, CAREFULLY remove any flashing around the cap and lingual wing (FIG. 41).
FIG. 42 shows the cap, front and back, after it has been removed from the stone model. The fang cap on the left side had an undercut that went undetected which caused it to break upon removal (FIG. 43).

In FIG. 44, the area in red is where the undercut was, in relation to the lingual wing. If I had designed this cap WITHOUT the wing I would have probably been OK. The arrows in FIG. 45 illustrate where the draw was undercut. As a solution, I ground off the area of the lingual clasp shown in red if FIG. 46. This allowed the cap to draw properly, plus I still had a bit of clasp for stability. Note the incisal translucency in FIG. 46.

To fix the broken cap, I ground back both broken edges about 3 mm, placed them onto the model, mixed up some body acrylic, flowed in into the gap and let it set in cold water. Later I dremeled down the excess so that the new acrylic blended in with the original.

Polishing is done in two parts. First, we start with pumice on a rag wheel. Pumice comes in powder form and is used mixed with water. You do not want to breathe this stuff, so wear a good dust mask! FIG. 48 shows the consistency I like to work with.

You really need a variable speed dremel tool to do this right. Ideally, a two-speed bench lathe is the way to go. Too high a speed will melt your acrylic and can eat away at your incisal edge, especially the cusp tip. The key here is to let the pumice do the work and not the rag wheel, so keep the cap covered with pumice.

After the primary polish with pumice, we move to acrylic polish, which will really make the caps shine. You want to use a separate rag wheel here. And remember, a low speed is the key here. I use a brand of acrylic polish made by Buffalo.

As with the pumice, you want the polish to do the work and not the rag wheel. The speed here can be slightly more than with the pumice, but be careful and go slow.

After cleaning with a mild detergent and a soft tooth brush, the caps are complete. Usually I will go over the caps with a coat of Lang's Jet Seal which is an acrylic glaze.