SNAP: What a Bunch of Crap

SNAP. Ya know, that wacky crappy liquid shit we use to make temporary (provisional) crowns in dental school? Yeah, that crap. What can I say about SNAP? Umm…nothing good. Oh wait, it’s cheap (and you always get what you pay for!). SNAP, the horrible crap that’s a sadistic rite of passage for every student dentist past and present. SNAP, the stuff that shrinks before your very eyes. SNAP, the crap that develops open margins and interproximal contacts even though you never even touched said contacts and margins. SNAP, the stuff that gives me recurring nightmares and PTSD symptoms. And guess what? I get to teach student dentists how to use the crap (ARGHHH)! Why? Cuz it ain’t goin’ away any time soon (damn)! Students (and faculty) STILL need to suffer through the crap. Worse, students need to be COMPETENT in its use in order to graduate! Oh the fantastic temporary crown materials that await students after dental school: Integrity; ProTemp; CoolTemp; VersaTemp; LuxaTemp; etc.

So at least for now it’s here to stay. And I have experimented heavily with ways to make it work in MY hands. Perhaps a few of my techniques may be of some use to someone out there (I make no guarantees).

1. Thermoplastic matrix…We have to make working with SNAP extra hard so we always use those damn thermoplastic suck down matrices that really suck (but they’re really cheap). And then people cut corners in their constructing said matrices thinking that it will save time. WRONG!!! Thermoplastic matrices are single use pieces of junk. In other words, constructing several matching practice temporary crowns on the same crown prep requires SEVERAL thermoplastic matrices. And those matrices need to be made on a stone model made from an impression (or duplicated stone model) of the exact same tooth/typodont/mouth that you’re prepping. The stone model should be no more than 10-15mm tall from the base of the model to the free gingival margin and the tongue/palate need to be cut out of the model so that the vacuum forming machine can have a chance to make a somewhat adequately adapted matrix. Trying to use a big thick typodont, especially the wrong typodont (fixed vs. operative) will only result in an ill fitting thermoplastic matrix that will be HARDER to work with. Cut your matrix in such a way: that there are two teeth on either side of the tooth you’re prepping; that there’s matrix covering 2-3mm of gingiva.

2. Mixing SNAP…I keep adding more and more powder to the liquid with constant stirring so that I can get to a honey consistency as quick as possible. Adding too little powder will result in extra shrinkage. So, adding adding adding powder with stirring stirring stirring and quickly arriving at HONEY will help prevent some shrinkage.

3. Loading SNAP into the thermoplastic matrix…Just like using a swizzle stick to add honey to tea I will pick up honey consistency SNAP on the back end of a bend-a-brush (or something similar) and swizzle/drip a string of SNAP snot into the proper tooth slot within the thermoplastic matrix.

4. Smoosh the thermoplastic matrix/SNAP combo into place over the right teeth in the mouth…We have to start to work fast and smart. The SNAP will be starting to set up fairly quickly at this point. Keep in mind that SNAP goes from liquid shit to kind of gooey shit to honey shit to doughy shit to rubbery shit to set shit, in that order, fairly quickly if we mix the right amount of powder shit into the plain clear liquid shit. We want the thermoplastic matrix/SNAP combo going into the mouth and onto the teeth right in between the honey shit consistency and the doughy shit consistency so that the SNAP doesn’t flow everywhere.

5. Make a test piece of SNAP…Take all the extra SNAP that didn’t go into the thermoplastic matrix and roll it into a ball. As it turns into a doughier consistency roll it into a hot dog shape (cylinder). The SNAP will start to get rubbery. We want to remove the SNAP from the mouth when rubbery. How do we know when it’s rubbery enough? When we bend an end of the hot dog and it “snaps” back into the same hot dog shape. If we bend the hot dog and it doesn’t snap back then it’s still too doughy.

6. Take the thermoplastic matrix/SNAP combo out of the mouth…Take the matrix with adequately rubbery SNAP and give it just a little 0.5mm to 1.0mm push up (burp it) and then push it back down into place. That little burp will break any kind of seal that may have formed. Further, we don’t want to burp more than 0.5-1.0mm because any further lifting (and/or multiple lifts) could wreck the temporary crown’s margin. After we’ve reseated the matrix/crown we then lift the entire matrix/crown out of the mouth and place the matrix/crown in hot water (this will speed the final setting and help prevent more shrinkage).

7. Remove the fully set crown from the matrix and separate the crown from big pieces of flash/excess.

8. Remove big pieces of flash around the papillae/interproximal contact areas…We now try to remove big interproximal pieces of SNAP around the papillae and the interproximal contact areas (please don’t touch the actual interproximal contacts) that prevent seating of the crown. We won’t do much margin refinement yet and, once again, don’t touch the interproximal contacts. We just want to remove enough stuff to get the crown to seat.

9. Reline the provisional crown…We now remove a little bit of material (0.1-0.2mm) from the intaglio/inside of the crown with a small bur in a slow or high speed handpiece (try to limit the removal of material from the intaglio side of the incisal/occlusal as this area will eventually serve as a stop). Make sure that the crown fits back onto the tooth easily after reaming out the intaglio. Now, mix up some more honey consistency SNAP, swizzle the SNAP into the inside of the crown and smoosh it back onto the tooth (now is when that untouched intaglio side of the incisal/occlusal will give you that good firm stopping point). Take any excess SNAP that oozed out beyond the crown margin and pack it/shape it snug around the crown margin/finish line of the tooth with a cord packer/composite instrument. Remove the crown from the tooth when the SNAP becomes rubbery. Put the crown back in hot water to fully set.

10. Trim the crown…Mark the interproximal contacts with a sharpie and remember that those are “no fly zones”. Trim the margins in a vertical orientation parallel to the long axis of the tooth. We thin the margin areas in this orientation from the outside of the crown moving closer and closer to the actual margin until the flash surrounding the margin becomes paper thin and flakes off with a fingernail (this means that the bur or disk never actually makes any kind of contact with the margin). Then we can go around the remainder of the crown removing any remaining flash and shaping the interproximal areas with no touching/losing the contacts (“no fly zone”).

11. Polish with composite finishers/polishers (red and yellow stripe finishing carbides if needed, green sandpaper disks, pink sandpaper disks, pink rubber points, blue rubber points).

So what am I accomplishing? With the thermoplastic matrix I make a custom provisional crown and then I use the reamed out crown and reline to further customize my custom provisional. As SNAP shrinks SOOOOOO much I defeat that shrinkage with the reline. And that reline usually helps to cut down on open and/or short margins that require “salting and peppering”. Also, if I lose a proximal contact I can cut a hole through the crown at the contact area and use a reline to smoosh SNAP out that hole establishing a new proximal contact.

Hope this helps a little. I can’t make SNAP go away but I sure hope there’s a pearl somewhere in my writing. And hey, if one can master SNAP then making temporary crowns with the good stuff (expensive stuff) will be EASY!