Introduction to impressions
Open tray impressions
Closed tray impressions
Express Abutment
Fitting implant retained prostheses
Managing the occlusion
Glossary of terms

Closed Tray Impressions - The Express Abutment

This page describes the use of a standard abutment for the Neoss system, the "Express Abutment". These are good for posterior teeth. This technique uses a closed tray, abutment level impression using a transfer device. The Express abutment is essentially a screw in crown prep. The transfer device, in this case the Express Impression Cap, makes the impression very simple because it is already made to exactly fit the margins of the abutment.




YOU WILL NEED:
A tray
If using a special tray ask for acrylic, 3mm spacing, perforations and a stepped handle. For this technique you could use stock trays too, especially for single units.
The screwdriver from the prosthetics kit
One big advantage of the Neoss system is that there is only one screwdriver. There are different lengths though.
The ratchet from the prosthetics kit
You will need this to tighten the express abutment into place
An abutment
You will need an "express abutment" for each implant
A transfer device
You will need an "express impression cap" for each implant
An implant replica
You will need an express replica for each implant
A temporary crown
You will need an express healing cap or you can make a conventional temporary crown
Impression material
We recommend that you use impregum mixed in a pentamix machine. However, the material is is less critical for single units and other crown and bridge materials can be used successfully.


PROCEDURE:
You are unlikely to need local anaesthesia for these procedures. However if the healing abutment is not fully seated or has come loose there may be some soft tissue over the head of the implant. In this case you can use a gingival infiltration of local and remove the excess tissue with a scalpel or, to conserve gum tissue, simply raise a minimal flap of about 1mm and release the gum over the express abutment.

Also check for obvious undercuts such as bridge pontics. If you use impregum it is very rigid and you may need to block out undercuts with some wax first.

Express abutment Express impression cap Express replica Express healing cap


Remove the healing abutment
Firstly you need to remove the healing abutments which are in place on the implants. Use the screwdriver from the prosthetics kit. The healing abutments should just be finger tight. Don't remove the healing abutments too early because the gingivae will start to recoil over the implant head and it will be sore for the patient when you place the express abutment and impression coping.

Changing the length of the screwdriver Unscrew healing abutment


Fit the express abutment
Take a look at the top of an implant. You will see that it has internal grooves to prevent rotation.




The express abutment has corresponding slots that fit into it. Take an express abutment and introduce it to the implant. Twist it gently between your fingers and you will feel it drop into the implant. There is a screw head accessible from the top of the snappy abutment. Take the screwdriver again and secure the impression coping fully onto the implant by screwing it finger tight. Do this for each implant. A big advantage of the Neoss system is that it is, in fact, impossible to screw the abutment into the implant unless it is properly engaged into the internal grooves. Therefore, if you have screwed it down, you are engaged properly.




At this stage some people recommend that you take radiographs to check that the snappy abutments are fully seated. I have found that this is rarely necessary with the Neoss system. However if it is the first time you have done it or you are not sure, you may prefer to take radiographs. You now need to tighten the abutment into the implant. The abutment is going to stay in place permanently from now. The tightness is very specific. Too tight and you might strip the threads on the screw or even break it. Too loose and the abutment will come off. The correct tightness is 32 Ncm (Newton centimetres).

Firstly fit the screwdriver into the torque wrench.




Set 32 Ncm by turning the adjusting knob on the end of the ratchet. The whole assembly is now placed into the screw head of the express abutment as shown. Make sure that you have "IN" pointing upwards on the ratchet.




Place a finger on top of the screwdriver to stabilise it then tighten the screw by rotating the ratchet until you hear a click and the ratchet "breaks" as shown above. This means that you cannot over tighten the screw. The abutment is now fitted.


Take an impression
Take the impression coping and place it onto the express abutment. Twist it in your fingers until you feel it slip over the abutment then push to fit it in place. You will feel and hear a snap as you do this. You are then sure that the impression coping is fully seated.




Now take your impression in your closed tray. Syringe some material around the head of the impression coping first to make sure that it is engaged in the impression. You don't have to worry about margins here. It is all taken care of by the impression coping.




When you remove the impression, the impression coping will stay in the impression and snap off the abutments.





Fit a temporary crown
This can be extremely simple. Just take a healing cap and press it onto the abutment until it snaps. That's it. If you need a more anatomic temporary then other techniques are available. However in most cases the healing cap is sufficient.




Snap the express replicas onto the impression copings
You don't have to do this, the technician will do it for you if you ask him. However some operators like to make sure before sending the impression to the laboratory. Simply take your express replicas and snap them into the impression copings inside the impression. You will need to twist each replica in your fingers in the same way as before so that it slides into the impression coping and then clicks.. The impression is now ready for casting by the technician.





Crown and bridge stuff
You now need all the other bits of conventional crown and bridge like an opposing impression, shade etc.

There is further description of the the Neoss surgery procedures on the Neoss website Neoss Implant System Guidelines



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