Milled Bridges Rocking Again

vurban210

vurban210

Active Member
Full Member
Messages
387
Reaction score
75
That photo shows what the machine mills out when I add the stabilizer bar. Its just one solid piece and not sprued with wax. And I cut back the bar to reduce that suck back effect.
Today, after showing how to properly sprue and invest to these waxers yesterday, we had two big bridges that fit really well. One waxer tried to heat up the entire bar to bend it
for a full arch bridge that was milled yesterday, and she sprued it without allowing it time to set and cool. I made it known that this is a big no no. They seemed to have gotten
the point. As for the length of the sprues on the photo.....Ive tried to make them longer in the software, but it simply wont allow me to do so. All I have control of is the thickness
of the sprues.

I'm not quite sure i understand what you are saying. In fact, none of this makes any sense to me. I mean, I understand how you are milling but I am not sure what happens after that. Are you leaving the milled support bar in place just reducing its mass? Is that what you are saying?

IMO - once milled the bridge should be completely removed of support bars and the like, then fit to the model, adjustments made and then properly sprued. Sure, you can mills sprues on a single unit and leave them attached but when it comes to a multi element bridge it would be insane to think that there are not forces in that wax that need to be released.

On another topic, casting with bars is absolutely pointless. Casting without a button is also pointless. Both are also quick ways to have issues. When metal cools it creates a vacuum and it has to pull metal from somewhere otherwise it is going to create tensions as well as porosity.

Runner bars, reservoir sprues, indirect sprues, direct sprues, hollow sprues, square sprues, plastic bars, and on and on and on. It is all a complete and total waste of time. (Also a way to get more $$ out of your pocket) The only thing you need to properly sprue everything from a single anterior unit to a foll roundhouse is some rolls of spool/sprue wax and some utility wax. That is it.

This is just my $0.02 worth.
 
dmonwaxa

dmonwaxa

Well-Known Member
Full Member
Messages
2,740
Reaction score
233
Sold Zr doesn't cool down as fast as our think. So when your small unit program has a cooldown down of 1min and you long span program has a cooldown of 12 min then yeah the Zr straight sheers clean. And the case has Zr lingual with each connector was well in size.


Sent from my SM-G920V using Tapatalk

Sevan, Pics please if available.
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
I'm not quite sure i understand what you are saying. In fact, none of this makes any sense to me. I mean, I understand how you are milling but I am not sure what happens after that. Are you leaving the milled support bar in place just reducing its mass? Is that what you are saying?

IMO - once milled the bridge should be completely removed of support bars and the like, then fit to the model, adjustments made and then properly sprued. Sure, you can mills sprues on a single unit and leave them attached but when it comes to a multi element bridge it would be insane to think that there are not forces in that wax that need to be released.

On another topic, casting with bars is absolutely pointless. Casting without a button is also pointless. Both are also quick ways to have issues. When metal cools it creates a vacuum and it has to pull metal from somewhere otherwise it is going to create tensions as well as porosity.

Runner bars, reservoir sprues, indirect sprues, direct sprues, hollow sprues, square sprues, plastic bars, and on and on and on. It is all a complete and total waste of time. (Also a way to get more $$ out of your pocket) The only thing you need to properly sprue everything from a single anterior unit to a foll roundhouse is some rolls of spool/sprue wax and some utility wax. That is it.

This is just my $0.02 worth.

The waxers have been spruing a certain way....and on occasion I will mill and bridge with sprues/bar in order to keep them from incorrectly spruing it the way they have been.
Yet it appears what Im doing is also wrong?
So you're saying I shouldn't have a bar at all? Sounds odd to me since virtually every lab I know of does it. Im certainly open to not using bars though. Perhaps Ill experiment
with that soon if we have a slow day.
 
vurban210

vurban210

Active Member
Full Member
Messages
387
Reaction score
75
The waxers have been spruing a certain way....and on occasion I will mill and bridge with sprues/bar in order to keep them from incorrectly spruing it the way they have been.
Yet it appears what Im doing is also wrong?
So you're saying I shouldn't have a bar at all? Sounds odd to me since virtually every lab I know of does it. Im certainly open to not using bars though. Perhaps Ill experiment
with that soon if we have a slow day.

When it comes to the bars I am referring to only the spruing part, not the milling process. And I should correct myself, I do not use preformed bars but when a feeder bar is required I will make my own from wire wax. (hard to explain in writing and I will take some photos.) The reason is that when casting it is important to always cast thick to thin. (in mass) Most of these bars that are preformed have small feeders, then a large runner bar and then again small feeders. So it is thin-thick-thin and this makes for troubles.

More importantly is the placement of everything in the ring and controlling where the cooling happens. That is the key, you can't stop the forces but you can control them.
 
Sevan P

Sevan P

Well-Known Member
Full Member
Messages
3,413
Reaction score
641
I find that a 6ga or 8ga clear plastic sprue works very well for the main bar when casting a full arch, just heat it up and bend it to fit. Then sprue the frame off that. Casting the milled bar is just ridiculous imho.

Sent from my SM-G920V using Tapatalk
 
vurban210

vurban210

Active Member
Full Member
Messages
387
Reaction score
75
I find that a 6ga or 8ga clear plastic sprue works very well for the main bar when casting a full arch, just heat it up and bend it to fit. Then sprue the frame off that. Casting the milled bar is just ridiculous imho.

Sent from my SM-G920V using Tapatalk

Yes, that was what I was trying to say but you said it much more concisely.

Maybe I am just too set in my ways, but everything I understand about milling wax leads me to believe that casting the milled bar would be a huge issue. I've cut bridges out of pucks and seen them go one way or the other when the tension is released.

One other thing that I have learned is to cast in nothing less than ~150 grams for everything, and larger rings if needed. It is crazy when I see people trying to use a 60 gram ring to cast a ton of waxups.
 
S

Solid

Member
Full Member
Messages
39
Reaction score
0
That photo shows what the machine mills out when I add the stabilizer bar. Its just one solid piece and not sprued with wax. And I cut back the bar to reduce that suck back effect.
Today, after showing how to properly sprue and invest to these waxers yesterday, we had two big bridges that fit really well. One waxer tried to heat up the entire bar to bend it
for a full arch bridge that was milled yesterday, and she sprued it without allowing it time to set and cool. I made it known that this is a big no no. They seemed to have gotten
the point. As for the length of the sprues on the photo.....Ive tried to make them longer in the software, but it simply wont allow me to do so. All I have control of is the thickness
of the sprues.
you're casting with the milled bar after reducing it? how do you reduce that bar ..using heated wax knife?
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
We solved the bridge issue we were having a while back, but its now happening again. Ive been using the stabilizer bar feature in Sum3D, and it seems to help somewhat, but these little bastards have begun to rock again. I suspect its the same issue as before (waxers carelessly spruing).....so I decided to leave the connectors kind of long when cutting the bridge off of the wax ring......this allows the waxers to sprue the bridges without getting their hot wax too close to the bridge itself.

It seemed to work for a while. But now they rock like crazy again. Also having issues with the cement gap, as one setting doesnt mill out enough, it the dies wont seat and I have to use a high speed to dig it out. Then the next setting they fit a little loose after we make an adjustment. Its getting frustrating and the guy who came here to teach us this stuff from Zahn was kind of a goof ball and simply could not help us with any tips.

Starting to winder if this stuff was even worth it. Any help from your experience would be appreciated.
i know youve more or less reduced this to a problem you know how to solve already, i just wonder why you don't go straight to milling CoCr or Ti copings instead of wax and cast?
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
i know youve more or less reduced this to a problem you know how to solve already, i just wonder why you don't go straight to milling CoCr or Ti copings instead of wax and cast?

Ive seen those options when choosing the material when entering cases. What exactly are those?
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
you're casting with the milled bar after reducing it? how do you reduce that bar ..using heated wax knife?

No, I use no heat when doing this...only taking a bur and cutting away at it from the rear (away from bridge.)
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
Ive seen those options when choosing the material when entering cases. What exactly are those?
well, first you get a titanium disc to mill, such as:

Gr2%20Dia%2098mm%20titanium%20blank%20dental%20CAD_CAM%20milling_2.jpg


then you mill your coping in it.
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
well, first you get a titanium disc to mill, such as:

Gr2%20Dia%2098mm%20titanium%20blank%20dental%20CAD_CAM%20milling_2.jpg


then you mill your coping in it.

Ah, okay. I've never used Titanium. Works well? It can be used the same as if it were a non-precious or SP alloy as far as applying porcelain goes?
 
CatamountRob

CatamountRob

Banned Member
Full Member
Messages
7,384
Reaction score
1,531
Ah, okay. I've never used Titanium. Works well? It can be used the same as if it were a non-precious or SP alloy as far as applying porcelain goes?
How well it works seems to be debatable, some love it, others don't. I believe it requires a different porcelain system than run of the mill PFM's.
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
How well it works seems to be debatable, some love it, others don't. I believe it requires a different porcelain system than run of the mill PFM's.
that it does.

but it effectively eliminates the whole wax and cast stage for NP anyway. you can always outsource gold.
 
Top Bottom