mounting casts on articulator

[bucktooth]

Hi all,

Just wondering what the best technique is to mount a cast on an articulator so that it looks presentable for grading if and when we need to for certain procedures (e.g. three unit bridge, crowns, etc...). Are there premolded rubber thingys that you can use to pour into to make a nice base? Just curious.

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[UBTom]

You can indeed get those rubber molds with the shape of the base... But I've never needed them.

When I pour up my dx cast impressions, I first flow a thinner consistency stone mix into the tooth impressions up to the vestibules, then build up the rest of the cast with a REALLY thick, non-flowing stacking consistency stone mix. Let set, then trim the casts with the rotary trimmer.

Same thing for pouring up the dies for fixed, except you use Jade Stone or Die Keen... Let set, drill the Pindex holes and place the Pindex pins, then stack up the base with the thick nonflowing stone mix.

I can finish mounting my Dx casts or fixed prostho dies on an articulator in under an hour and they will look decent too.

 

[no2thdk999]

Pour up your models however you need to to get a nice void free cast with a base slightly larger, I like the vac-u-spat. Trim it like the ortho guys tell you, to the height of the vestibule with all the fancy angles, the preformed base will pretty much do that for you. Mount it on your articulator with whatever you use for mounting plaster. Glob it on there, don't leave any spaces. Once its set trim the gross excess with a Buffalo knife. Then take fine wet sandpaper (from any hardware store) and make the transition from model to plaster to mounting bracket silky smooth. You can soap your models if you want them to have that shiny look. Repeat for opposing.

Tom if by thinner consistency you mean adding water you can't really fool around with the water/powder ratio without getting too much or too little expansion of the stone. It won't hurt you with study models or bleaching trays but your fixed and cast removable will come back too tight until the lab gets sick of remakes and they will over block out your casts. In the real world the lab will pour everything up for you and do it precisely.


Bob

 

[UBTom]

Hi Bob,

Yep, the Die Keen and Jade Stone (which my school uses for fixed dies and RPD master casts) do have their prescribed water-to-powder ratios and I definitely follow those. They do mix up pretty flowable though so that's not a problem.

As far as the stone mix goes for dx casts, the regular consistency is the thinner consistency-- it flows. I would add powder to the mix until it is getting REAL thick (non-flowing) for the stacking consistency to build up the base, with which over/underexpansion is not an issue (since you will be trimming it anyway!).

Yep, I'm looking forward to the day when I'll have others pour up the dies for me.