Trying to avoid hyperocclosion in fixed c&b - Strategies?

S

semper:fi

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#1
Hi everybody from Germany,

i'm fairly new in fixed prosthodontics and i'm trying to overcome problems with hyperocclusion in crowns and bridges.

The impressions coming from the dentist are with impregum/permadyne and alginate. Bites are made with stonebite and there is a occlusion protocol.

Sawed models are made with a resin baseplate and both models are made with high quality plaster. The models are set into an articulator with articulating plaster and the occlusion protocol is transferred via reducing the plaster of the model. The front pin (i dont know what's the correct word in english) shows around -0,5 after that.

But theres still a lot of drilling for the dentist to achieve perfect static occlusion, wich takes a lot of time. :(

Can you explain me your strategies to avoid hyperocclusion or maybe any mistakes that I make in my working protocol?

Thank you very much
 
2thm8kr

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#2
Start with weighing the die stone. 100 gm to what ever the ratio of water to the stone you are using. This will give you more consistent results with the expansion.
Do not invert the impressions after pouring, let gravity be your friend during the setting of the stone rather than your enemy.
What type of articulator are you using? When we were using stone models we opened the pin to -1,0mm. Using articulating paper we removed the interferences between the two casts until the pin was closed.
 
S

semper:fi

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#5
Ok, i think this is not really easy to accomplish with the resin base plate, but i will give it a try.

But i dont think this is the main reason or failure because when I transfer doublesided triple-tray impression into the mouth the plaster hardens upside down and the results sadly arent any better..
 
CoolHandLuke

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#6
i've experienced poor fit of articulation plates, where material like wax and plaster from reused plates would interfere with new mounting. switched to magnetic plates, epoxied the permanent plate in place, and use magnetic washers to "home make" new magnetic mounting plates using stone and a washer.

the same can be true of Amann Girrbach's resin magnetic plates.

but you are experiencing the Opposite problem, your bites are too closed.

i'd look to the impression material age, and mix quality. assistants that are less experienced with this material, especially impragum, can take poor quality impressions without noticing the problem.
 
O

omsk

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#8
Do you have picture of the impression?

Is it problem with only 1 doctor or everyone?
 
S

semper:fi

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I'm the (young) doctor AND the dental technician myself, that is why the problem bugs me so much. ;) A lot of effort is put into the crowns but the occlusal drilling consumes a lot of time at the patient wich could be used for better things.

As you can see below the impressions are quite alright (in my opinion ;) but i could be biased) and the seating of the crowns is also quite good. The approximal contacts are almost always perfect as they are double checked on the model and the unsawed control-model. The only problem that remains is the amount of hyperocclusion that remains quite high.

Ah, and the provisionals always have perfect occlusal contact when the patient leaves the office. They are made from 3M Bis-GMA Resin

IMG_1561.jpg IMG_1189.jpg
 
Last edited:
rkm rdt

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#10
You say you checked the contacts on the solid model. Did you check the occlusion on the solid model also?
Mount the solid cast in your articulator.

What is stonebite? I always slice a lengthwise section from the bite material to verify it's seating accuracy.
 
S

semper:fi

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#11
Stone bite is a quite hard and brittle silicon-based bite registration material.

I do the same: After articulating the models i cut the bite registration material in half and put it back to control the seating.

Articulating the uncut model could be an idea, but regarding the fact that i already lowered the vertical dimension with the first model the fitting with another model should also be to high
 
rkm rdt

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#13
Stone bite is a quite hard and brittle silicon-based bite registration material.

I do the same: After articulating the models i cut the bite registration material in half and put it back to control the seating.
I think that could be your nemisis.
To be honest, I only use the bite registration as a last resort if I cannot find it naturally. I don't trust it and usually have to adjust the casts as 2thm8r said.

The fact that your contacts and I assume your marginal ridges are good indicates that it is not an expansion problem.
 
JMN

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Stone bite is a quite hard and brittle silicon-based bite registration material.

I do the same: After articulating the models i cut the bite registration material in half and put it back to control the seating.

Articulating the uncut model could be an idea, but regarding the fact that i already lowered the vertical dimension with the first model the fitting with another model should also be to high
There is your problem. If you don't have bite through at their occlusal contacts, and with a hard silicone you likely won't, it will not be a 'correct' bite registration. It may be in the arc of closure, but it will not be right on.
 
S

semper:fi

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#16
@JMN

Stone bite is very soft (similar to whipped cream) when it comes out of the dispenser and only gets hard after around 30 seconds
 
O

omsk

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#17
What type of stone are you using?

Impression is good.

Are you also designing the crowns?
 
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