Max unsupported units on Porc-Zir bridge

[Levire]

Had a case come in today for porcelain to zirc 4-12. The only abutments are 4,5 and 12. Is this an accident waiting to happen? What is the norm for unsupported units in a zirc frame, or max distance between the abutments. Thx

 

[PDC]

It depends on the strength of the zirconia and the the manufacturer's indications relating to such. For example, 3M recommends not exceeding 48mm spans with pontics. Most manufacturers use mm to describe the span rather than just saying "6 or 7units" . One 6 unit bridge bridge might be 48mm and another 55mm depending on the patient.
In the case you described I would be more concerned with the fact that you only have 3 abutments supporting this entire case and none of them are canines. Looks like trouble to me.

 

[charles007]

Implants or floppy partial

 

[doug]

This case will fail.

 

[DMC]

Maxillary is less prone to flexing than the Mandible. That's a plus right off the bat.

Could work. Depends on available space (vertically) and how you design.

Keeping the Linguals and part of occlusal Full-Contour Zr may be the ticket to success?

Keeping the frame flush with ridge also add to rigidity of course.

Really depends on the specific situation. I love a challange.

Sounds like fun.

 

[Levire]

Need to make a correction. My memory fails me lately. The abutments are 4,5,11 and 12. Working on the case at the moment. For the record...not a fan of DW. It does some weird $#!t. Thx for the replies.

 

[NicelyMKV]

I would design full contour Linguals and occlusals with all pontics contacting the ridge in Zr. .7 to .8 mm facial cutback with slight lingual incisal/cusp ceramic overlap. I always maintain as much vertical Zr as possible in the bridgework areas.