00:00 Introduction
The multi-unit abutment was developed by Nobel Biocare over 20 years ago and it's been so successful that today compatible versions are available for most major implant systems.

In this video I'm going to discuss some of the features of the MUA, the restorative options, and when it's indicated and contraindicated for use.

00:27 About the MUA
Originally designed for the Branemark external hex implant, the multi-unit abutments are now available across nearly the entire line of Nobel Biocare implants. They're used for making multi-unit screw retained restorations and are not indicated for single units.

There are both straight and angled versions available and they come in multiple margin heights as well.

Even though the prosthetic connection is the same for both the straight and angled abutments, their designs have some significant differences.

00:57 Straight MUA Specifics
The straight multi-units abutments have a non-engaging connection to the implant. For the Branemark system they have a separate screw, but for the other Nobel systems they actually have a screw that is integrated in to the abutment. At the most coronal end of the prosthetic connection they feature a hex which is used to torque the abutment in to place. Each straight multi-unit abutment comes with a pre-mounted plastic holder which is used to transfer the abutment from the package to the implant. The holder is fairly long, but it can be shortened with scissors for use in tight occlusal spaces. Once the abutment has been rotated in to place with the holder, the holder can be removed just by pulling it off of the abutment. Instead of using the typical unigrip driver, these are torqued in to place with the multi-unit driver which fits on top of the hex. The recommended torque for the straight multi-unit abutments is 35Ncm for all Nobel implant systems.

02:00 Angled MUA Specifics
The angled multi-unit abutments are available in both 17 and 30 degree angulations and have an engaging connection to the implant and a screw that is independent from the abutment. The angled multi-unit abutments come with a pre-mounted metal holder as opposed to the plastic one. The holder is used to transfer the abutment to the implant and also makes it easier to rotate the abutment to the desired position before torquing the screw. The angled multi-unit abutment screws get torqued in to place using the standard unigrip screwdriver. The recommended torque for the angled multi-unit abutments is just 15Ncm instead of the 35 that is recommended for the straight abutments. Once the abutment has been torqued in to place, the holder can be unscrewed from the top of the abutment.

02:50 Margins and Angulations
Both the straight and angled abutments come in various margin heights between 1 and 5 mm. The exact heights that are available is dependent on the system and size. There are also 45 and 60 degree abutments for use on the Nobel zygomatic implants which are available in extended margin heights of 6 and 8mm and up to 10mm for the 45 degree abutment. Unlike the other angled multi-unit abutments, the 45 and 60 degree abutments get torqued to 35Ncm.

03:23 Prosthetic Screw
Each multi-unit abutment has internal threads at the top that is used for attaching the restorations. The screw that is used to fasten the restoration to the multi-unit abutment is called the prosthetic screw and it has a maximum recommended torque of just 15Ncm.

03:39 Advantages & Disadvantages
Although the multi-unit abutments are most often associated with full arch hybrid restorations, they can also be used for smaller bridge work. And there are some advantages and disadvantages of using them in this way.

One advantage is that when multi-unit abutments are placed at the time of surgery, they won't need to be removed for the impression and will therefore aid in preserving the adherent epithelial and connective tissues. Instead of taking an implant level impression, impression copings are screwed directly to the multi-unit abutments and a model is created using multi-unit replicas.

Having a multi-unit abutment in place will also bring the margin of the restoration closer to tissue level which can make it much easier to seat the restoration. On the other hand, this can also have a negative impact on the emergence profile of the restoration.

And of course, the angled multi-unit abutments give you the ability to place the access hole of the restoration in a more favorable position when needed.

04:37 Restorative Options
There are several options for restoring over the multi-unit abutments.

-Milled titanium frameworks which can be used to make attachment bars and acrylic hybrids
-UCLA abutments which can be used to make full cast or porcelain to metal bridges
-Milled zirconia which can be used to make a full zirconia hybrids or as a framework for layering.

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