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

Fitting a Single Implant Retained Crown

In this page we will use the case of a single crown as an example. In most crown cases there will be an abutment which is fitted to the implant first and then the crown is fitted to the abutment. However it is also possible to screw a crown directly into an implant. This page will describe the most common situation which is fitting of an abutment followed by cementation of a crown. If you have used a standard abutment such as the "Express abutment" abutment, you just need to remove your temporary crown and then you can go straight to crown cementation below.


YOU WILL NEED:
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 torque wrench from the prosthetics kit
You will need this to tighten your abutment into place
An abutment
If you use a custom abutment this will be sent by your technician.  If you have used an Express abutment then the abutment will have already have been fitted.  See "Express abutment".
A positioning jig
For custom abutments it is very useful to have a positioning jig to help you set the abutment into the implant in the correct orientation. Your technician will make one for you, usually from duralay.
Your crown
There are options for your crown. Metal ceramic, all porcelain systems or even acrylic can be used.
Cement
There are a number of different options for this
Articulating paper
Miller forceps are useful to hold the articulating paper for you.


PROCEDURE:
In most cases, local anaesthesia is recommended.  It is good to lift the gingivae over the crown so that it looks as it it is emerging from the gingivae in a normal way.  Often you may need to relieve the gingivae at little to allow this, especially if you have used a standard abutment.  If you have used a Neoss tissue former then the gingivae will, most probably, have been formed into the best contour already..

Remove the healing abutment
Firstly you need to remove the healing abutment which is in place on the implant.  Use the screwdriver from the prosthetics kit.  The healing abutment should just be finger tight. 


When you have removed the healing abutment, you will be able to see directly down onto the implant head. Note the six internal locating notches.


Your technician will make you an abutment.  This is the connector between the implant itself and the crown.  It's essentially a "screw in" crown prep. There's a screw running right down the middle of the abutment, into the implant head. The abutment on the model will look like this:


Because the Neoss implant has six internal locating notches to prevent rotation, there are six positions in which you can place the abutment.  Only one of them will be right.  However, your technician should send you an acrylic positioning jig.  This is the way that you will fit the abutment in the right orientation.  Place the positioning jig in place on the abutment, like this:


You can then unscrew the abutment through the positioning jig with the Neoss screwdriver, lift it off the model and transfer the whole assembly onto the implant head.


You'll probably need to wiggle it a bit to get it down, or even start screwing the screw down into the implant.  It is obvious when it has dropped into place because the wings will sit nicely on the adjacent teeth as above. Keeping the positioning jig in place, you can screw the abutment fully down.


Use the Neoss torque wrench to tighten the abutment screw to the correct torque.  This is 32Ncm and you set it by twisting the end of the torque wrench until the scale on the side says 32.  Have the side of the torque wrench which says "IN" on the top and just slip it onto the screwdriver head.


When the screw reached the correct torque the torque wrench "breaks" in the middle so that you can't over tighten the screw.


You can now remove the positioning jig leaving the abutment, your "screw in crown prep", in place on the implant.


You can then pull off the positioning jig, leaving the abutment in place on the implant.  From this point it starts to feel a lot more like conventional crown work.  In this case the gingivae need to be lifted over the crown as it is fitted.  Without that, the crown won't seat correctly.  I would suggest taking a scalpel and cutting around the abutment with two little relieving incisions like this:


Then just raise what I call a "mini-flap".  In other words just raise the gingivae about a millimetre, no more, so that the crown will just slip under the gingivae, onto the abutment and fully seat.

Crown cementation
From this point it is almost a conventional jacket crown fit.  However you might want to recover the abutment one day so we're going to protect the screw head from getting cement in it.  That way, if it needs to come off again, we've got a fighting chance.  Take a small pledget of cotton wool or PTFE tape (plumbers tape) and place it into the cavity where the screw head is.  Make sure that it doesn't extend out of the cavity because this would stop your crown from fitting.

Now try in your crown.  If your abutment isn't seated properly you will soon know because your crown won't be anywhere near.  However with the Neoss system this is very unlikely, especially using a positioning jig. The other common reason for your crown not to fit is that the contacts are too tight, just like conventional crown work.


Again, you might want to recover the crown some day and so it is good to use a temporary cement.  However the abutments are usually so retentive that even temporary cements such as tempbond are extremely effective and make it difficult to remove your crown. There are also commercially available resin implant cements which are permanent but with some retrievability.  At the time of writing I'm using one called "Premier Implant Cement".

Cement your crown in the normal way but be careful with excess cement.  It is not good for implants to have cement around subgingivally so let the cement set and then remove all excess carefully.  One of the advantages of the "mini-flap" technique, is that it gives you access to clean off all excess cement after the crown is fitted.

It's good practice to take a radiograph at this stage.  This checks that the crown is well seated and acts as a reference image for future radiographs so that bone levels can be monitored.


That's it.  All that remains is to check and adjust the occlusion.  This is discussed on the "Occlusion" page.



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