Custom abutments help!

[wwcanoer]

I need help trying to figure out what I'm doing wrong!

I am trying to cast custom abutments, from Implant Direct, and not having much luck.

My recent misadventure: waxed up, sprued acording to their diagram, cleaned "platform's with burning alcohol before investing. Using Cristobalite from Whipmix using my normal "gold water/powder ratio". Bench set in a humidor environment for one hour. No de-bubblizer used

Burn-out at 148° C, with a 5 degree/minute climb held for 1.5 hrs.,. Then to 565°C at 5 degree/minute held for 1.5 hrs. ., bench cooled. Cast with type III (63% gold alloy),

As you can tell from picture number one, I had gold flash up and over the outside of the abutment-platform wall into the hexed. (I will admit, I am probably not calling the platform components by their proper names)

In picture number two: a different perspective of the gold flash. You'll also notice that I tried to run a fine bead of wax around the junction between the platform and my waxed crown. And yes, I would say that there was a separation, or short cast?, of some sort at that junction.

Called up the tech help people at Implant Direct, and had a not very satisfying conversation with them. Admittedly, upfront they admitted that they are not technicians but gave me the following advice. Never never have your holding time at the high temperature to exceed one hour. I also e-mailed them pictures of my problems. Again, their follow-up phone calls were great, and did notify me that their laboratory technician troubleshooter was unavailable. Maybe next week. . .

Picture number three:

New abutment, re-wax the crown with these changes
after cleaning everything with burning alcohol, which I do after everything is sprued, let bench set for about a half an hour to make sure all residue has evaporated, I also used a brand-new analog to hold my wax-up just to make sure that I didn't have any contamination from that source.

Then


1) first stage burnout held for only one hour
2) final burnout temperature held for only one hour

As you can see, I still have flash going up the side of the platform, only it stopped just short of the top. You also notice, that I still had "separation" between my waxed and platform junction.

Any thoughts? With custom abutments at $100 a pop, I need to figure this out real quick!

Carol E E

PICTURE # 1
[IMG][/IMG]

PICTURE #2
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PICTURE #3
[IMG][/IMG]

Carol

[disturbed]

your burnout time seems a little excessive, as does your bench cool. I prefer to put the rings into a hot oven while they are still hot themselves, I would bench set for maybe 3-5 mins. If you burnout the investment for to long it will start to break down and lead to flash issues like your pics, I prefer microstar investment. anyways..... first burnout stage to reach temp starting around 180 should be bout 15 minutes till at max temp around 700, then burnout for no more than 45 minutes. do this burnout time for ALL castings.. less chance of flash. bulk your margins in wax and finish them back after casting so you dont have shy margins around the interface..

thats what works for me anyways,, hope it helps

[TheLabGuy]

It's one of three things, you had some wax flash on that area, investment broke down (like Disturbed is stating), or an oxidation layer occurred during casting. I haven't seen the oxidation layer occur on implant directs ucla's but I have on Blue Sky Bio, so much so I had to stop ordering the titanium cast-to ucla from them. Was this a gold cast-to ucla abutment or a titanium cast-to ucla abutment?

[wwcanoer]

These are gold cast-to UCLA abutments.

Next one I'll dial back the first stage hold time to 15 min., and drop second stage to 45 min. hold, and these go into a cold oven.

I'll let you all know how it goes!

I've tried full gold crowns into a hot oven with Microstar HS, but not overly satisfied with the first couple tries. Do have it dialed down with my porcelain castings thou

Carol

[Labwa]

i dont do a two stage rise using speed burnout. i just put it in at its peak temp. let it sit for 45-50 minutes. make sure your setting time for investment is 15-20 minutes.
ive found messing with these times causes flash issues.
ill also say those straumann implants cause me the most problem with flash over any other.

[BobCDT]

Your waisting your time and money. Casting CLA's with AU cylinders and gold should be obsolete. Go digital and have the abutment milled from a solid blank of titanium. You can outsource them for a coulpe hundred bucks.
To correct you problem you can put anti flux on the gold interface prior to investing. Also, make sue you are not over winding your casting machine.

[DMC]

try more water and less special liq.

No need for any expansion!

Make sure burn-out is not too hot.

Calibration?

[wwcanoer]

Bobcdt: Dr wanted a screw retained gold crown, so the need to go with UCLA abutment.

DMC & labwa; With this case, I wasn't using speed (Microstar) investment. Using Cristobalite- water only- into a cold oven. The two stage burn-out technique is a hybred from Donny Poe's technique from the late 90's. Does that ever date me. Slow burn-out rate long heat soak equates more control with expansion if I remember correctly

And burn out temps aren't on the hot side, 1000F, and have already dropped from 3 1/2 turns down to 2 1/2 turns on casting machine. Oven was resently checked for calibration.

It's a week like this that will give me "silver hair"

C

[dmonwaxa]

Two things; your technique has to be meticulous so there is no need for alcohol,,,next,,,, you need to control your expansion, there's too much. The telltale sign is the gold marginal gap at the cast to ucla.

[DMC]

For this reason....I don't wax to the bottom edge....

Never had that problem ever again!

It creates an undercut on exposed UCLA for investment to "bite" and has better retention to part when your wax disappears. No floating of UCLA.

What Alloy to use (cast to UCLA Gold)

[wwcanoer]

Let me see if I understand you correctly. Are you saying that you do not carry the wax out to the edge of the platform, instead, leaving a shelf-exaggerated-as indicated with my red arrow in my funky drawing? If so, wouldn’t that open the door to a whole different set of problems?

[IMG][/IMG]

C

[DMC]

I go up even higher than that!

Never had issues at all.

[doug]

If you cut in at the junction of the wax and gold to create a small "V" type indention you shouldn't have any problems with the flash across the interface.

[wwcanoer]

What on earth do you do with the ledge then? I would think that if you left a “V”, it would become a bacteria – hygiene nightmare. If you finished back the platform to your gold junction, that would compromise your emergence angle. Wouldn’t it?

[DMC]

What ledge? Cover it with porc untill it looks right.

Maybe it defies law, but I have no problem covering with Porc. right to the Implant level. Right over Virgin Gold alloy NOT buried in other alloy.

Other do this as well (as in other thread)

[doug]

It's' not that deep. You rubber wheel the whole piece to make it a smooth transition.

[disturbed]

I go up even higher than that!

Never had issues at all.

again.. I love this site, I always learn something new.. thanks scott

[Labwa]

yeah once you layer the porc. down to the ledge and polish before glazing youll have a perfect interface. no cracking. thats a myth!

[araucaria]

looks like going off-track. Pardon me if I'm wrong but OP states in post 8 "Dr wanted a screw retained gold crown" and wishes to acheive a 'perfect' join without need for adjustments to contour.

[DMC]

He want's cake and wants to eat it too!

Absurd!