fixed attachments to RPD??

[rkycdt]

I provided my dentist with a crown that included an extracoronal male-ball type attatchment that connects to a pre-cast female housing. He asked me this morning if I knew what the partial tech will need in the impression..................I don't.

Does he need to attach the female housing to the abutment when taking the impression?

Thanks.

 

[TheLabGuy]

If I understand you correctly, I would say that most of these type of cases are done in tandem (a combination case). However, the best way now though would probably have the doctor seat the crown, then place the female end of the attachment on the male end of the ball on the crown and have the Dentist pick that female end up for accuracy purposes. Then I'd probably use some epoxy die stone or casted male attachment in that area and pour up the rest regularly and then fabricate the partial accordingly. Just having the Dentist taking an impression of the ball attachment isn't accurate at all and almost impossible because it will tear and be voids IMO.

 

[CYNOSURER]

Give him or his partial lab the name of the attachment manufacturer. Chances are, if it's Bredent for example, they'll have all the info they need online. I haven't done a Bredent VKS in awhile. The last time I did one they were telling the doc to simply take an impression and insert an analog into the ball recess (got to make sure you have the right size though). Seems they have changed to a impression coping now. Don't have time to check this a.m. and it might not even apply to your particular case, anyway. But I do need to double check and find out later for my own info.

I always thought that impressing with the female would be better and still use the analog inside that when pouring up... but, what do I know. I guess the danger here is if they don't stay put (or rotate to where the base isn't aligned properly but give enough to come out of the impression but screw up your path of insertion when locked into a framwork). So, when you impress the female, you could be locked into a bad position... though insetting the analog should give you the ability to fix that. Who knows?

 

[rkycdt]

Thanks.

Now Rob, bare with me - but am I to understand that (in the future anyway) before fabricating an abutment like that I should be contacting the partial tech or that the finished crown should be sent to them before it is seated?

 

[TheLabGuy]

Yes, the best way to attack these type of cases is to consider them Combination cases. Do the crown and partial at the same time. The Dentist would have to be made of aware of this so he can take a partial impression after prepping along with another impression for the traditional fixed case. Do the fixed case (crown w/attachment),then use that crown with the partial impression and then do the partial. The Dentist then will seat the crown and partial at the same time, takes longer but that's the best way in my opinion for accuracy, and it's all about accuracy in cases like this where a tenth of a millimeter could cause a severe migraine. Hope that helps.

 

[rkm rdt]

I agree with Rob.

You need to work closely with the removable tech on these cases...or be a removable tech as well.....ah monomer and pumice splashback...nectar of the Gods.

 

[rkycdt]

Yeah, I was bs-ing with him about the matter - which the process you mention is something he has done in the past but he said he felt that was too long for a temporary and that there was even potential for distortion there - so he tended towards the method of seating the crown first and then using self-curing resin to re-seat the female part to accuracy if need be.

for my own curiosity what are the thoughts on that?

 

[TheLabGuy]

That works, but it takes into account some chairside knowledge for the Dentist to do accurately in my opinion.

 

[JohnWilson]

All your questions are best suited to be answered by knowing the talents of your client. As others have stated the best results are achieved when two techs discuss what each needs to have a successful outcome. Labs that are equipped to do combination cases are valuable. Educating yourself as to what the removable lab needs is wise.

Since we are a full service lab its much easier to design these cases, however we still must rely on the client to sequence things properly. As to your particular question if the client wants to seat the crown I assume the patient does not have an existing appliance that will make this difficult to do.

If the client MUST seat the crown as Tim stated if its a VKS attachment there are two sizes to the ball attachment 1.8 and 2.2. Each have a corresponding lab analog that will be placed in the impression. If the prefabbed housing is available like Rob stated its easy to pick that up snap the analog in the impression and you have a master model for the partial. It also can be done with out an attachment if a very high durometer impression material is used and the client blocks out the bottom of the ball to the tissue. Then just insert the analog in the impression and glue it in place then pour it on up.

As for luting this particular attachment chair side I do not recommend it. Since the attachment will have to be blocked out from the bottom of the ball down to the tissue only the most competent of clients can achieve this with out locking the acrylic under the ball and making a mess of things.

With all this being said, picking up the crown in the final impression is the absolute easiest and most accurate way to finish the case up

Good luck

 

[Al.]

.....ah monomer and pumice splashback...nectar of the Gods.

I think Rob would say the smell of napalm in the morning is nectar of the gods.

 

[Al.]

With all this being said, picking up the crown in the final impression is the absolute easiest and most accurate way to finish the case up

Good luck

Thats good to know and what Ill recommend.

 

[rkm rdt]

I think Rob would say the smell of napalm in the morning is nectar of the gods.

I don't want to give him any ideas. lane::flame::flame::flame::target: