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of Andrew Shelley
Introduction to impressions
Open tray impressions
Closed tray impressions
Express Abutment
Fitting implant retained prostheses
Managing the occlusion
Glossary of terms
Open Tray Impressions
This page shows how to take an open tray implant level impression. These are often called "fixture head impressions". This example will show the impression for Neoss implants. With one exception ( the very narrow 3.25mm implant) all the Neoss implants have the same width of restorative platform regardless of the width of the implant itself. This is how it works:
As you can see, the top bit, the restorative platform, is always the same at 4.1mm. This means that, unlike other systems, you don't have to use different sized components for different widths of implants. They're all the same and this makes things very much easier. You just order an impression coping and you know that it will be the right diameter.
YOU WILL NEED:
A transfer device
You will need an impression coping for each implant, They come in different lengths, 8mm, 11mm and 18mm but they are all the same width. The 11mm impression coping will be good for pretty well all your impressions. You would only need the 8mm or 18mm if the adjacent teeth are exceptionally short or long.
An implant replica
You will need an implant replica for each implant but they come in the pack with the impression coping.
The screwdriver from the Neoss prosthetics kit
Another advantage of the Neoss system is that there is only one screwdriver. There are different lengths though.
A special tray
Ask for acrylic, 3mm spacing, perforations, a stepped handle and a window cut over the implant. It is also possible to cut a window in a disposable plastic stock tray.
Impression material
We recommend that you use impregum mixed in a pentamix machine. The material is is less critical for single units and other crown and bridge materials can be used successfully.
A sheet of wax
You will need some regular sheet model wax which you will soften over a flame.
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.
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. Another good tip is to prescribe your tray, for upper teeth, as a horseshoe shape. If you have a full palate, the impression material can form a really good peripheral seal making it difficult to remove the impression.
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. Keep the healing abutment safely. You will need it again. I like to soak it in 0.02% chlorhexidine mouth rinse until I need it again. Don't remove the healing abutment too early because the gingivae will start to recoil over the implant head and it will be sore for the patient to place the impression coping. If there is more than one implant then remove the healing abutment and place the impression coping one implant at a time. Also keep the healing abutments in order so that they can go back onto the same implants. They may be of different heights.
Fit the transfer device
Take a look at the top of a Neoss implant. You will see that it has six locating "slots".
The impression coping has to locate into the slots in the head of the implant. Take an impression coping and place it into the implant with the screw end first. It has a plastic tube fitted to the other end....more of that in a minute. Screw the impression coping lightly into the head of the implant. You can hold it by the plastic tube to do this. A big advantage of the Neoss system is that you cannot screw the impression coping into the implant head unless it is properly located. The thread is deliberately too short to allow you to do that. In other words, if you are screwed into the implant head then you are properly located.
The screw head is accessible through the plastic tube. Take the screwdriver again and secure the impression coping fully onto the implant by screwing it finger tight. The screwdriver will go down the tube to engage the screw head. At this stage some people recommend that you take radiographs to check that the impression copings are fully seated. This is not necessary with the Neoss system because of the short thread. However if it is the first time you have done it and you are not sure, you may prefer to take a radiograph. You will be checking that there is no gap between the head of the implant and the impression coping. (There won't be).
Try in the tray
Try the tray in the mouth and make sure that the impression coping has some clearance around it in the window.
Lay wax over the tray window
In order to prevent your impression material from flowing all over the place, lay some softened wax over the tray window and onto the surrounding acrylic. Place the tray in the mouth again and push the impression coping through the wax.
Take the impression
Mix your impression material and load the tray. You may like to syringe a little around the impression coping too. Place the tray in the mouth so that the impression coping pokes through the wax again.
Unscrew the impression copings
When the impression material has set you get to see the big advantage of the plastic tubes. Take hold of the end of the tube and give it a sharp pull. You can use a pair of pliers for this if it is difficult to grasp. You can now see right down, through the impression material, to the screw head.
With some other systems you have to go searching with a scalpel through the impression material to find the screw head. The Neoss plastic tube is really useful to avoid that problem. Now unscrew the impression coping from the implant. If you apply a little downward pressure as you unscrew the impression coping you will hear and feel a click as the screw reaches the end of the thread. You can then be sure that it is no longer engaging the implant.
Remove the tray
Your impression coping will be picked up in the impression. If you feel undue resistance check again that the coping is fully unscrewed. You have now transferred the position of the implant to your impression. In some ways this is a lot easier than a conventional crown and bridge impression. You haven't had to worry about margins. It was all taken care of by the impression coping.
Replace the healing abutment
All that remains is to replace the healing abutment. Just screw it back in finger tight.
Screw the implant replica onto the impression coping
You don't have to do this yourself, your technician will do it for you if you ask. However some operators like to make sure before sending the impression to the laboratory. Simply take your implant replica and place it onto the impression coping inside the impression. It will engage in the same way as before. Use the screwdriver again in the other end of the impression coping to finger tighten the replica into place. Hold the implant replica between your fingers of one hand and the screwdriver with the fingers of the other hand. Don't try and tighten the screw whilst supporting the impression. That could lead to the coping getting turned in the impression and then everything will be wrong. Your impression is now ready for casting by the technician.
To understand why the impression technique is the way it is, it is very helpful to see how the technician converts this impression into a working cast. You can see that on this video. It also shows how to hold the implant replica whilst tightening the screw of the impression coping.
Crown and bridge stuff
You now need all the other bits of conventional crown and bridge like an opposing impression, shade etc.
Open tray impressions
Closed tray impressions
Express Abutment
Fitting implant retained prostheses
Managing the occlusion
Glossary of terms
Open Tray Impressions
This page shows how to take an open tray implant level impression. These are often called "fixture head impressions". This example will show the impression for Neoss implants. With one exception ( the very narrow 3.25mm implant) all the Neoss implants have the same width of restorative platform regardless of the width of the implant itself. This is how it works:
As you can see, the top bit, the restorative platform, is always the same at 4.1mm. This means that, unlike other systems, you don't have to use different sized components for different widths of implants. They're all the same and this makes things very much easier. You just order an impression coping and you know that it will be the right diameter.
YOU WILL NEED:
A transfer device
You will need an impression coping for each implant, They come in different lengths, 8mm, 11mm and 18mm but they are all the same width. The 11mm impression coping will be good for pretty well all your impressions. You would only need the 8mm or 18mm if the adjacent teeth are exceptionally short or long.
An implant replica
You will need an implant replica for each implant but they come in the pack with the impression coping.
The screwdriver from the Neoss prosthetics kit
Another advantage of the Neoss system is that there is only one screwdriver. There are different lengths though.
A special tray
Ask for acrylic, 3mm spacing, perforations, a stepped handle and a window cut over the implant. It is also possible to cut a window in a disposable plastic stock tray.
Impression material
We recommend that you use impregum mixed in a pentamix machine. The material is is less critical for single units and other crown and bridge materials can be used successfully.
A sheet of wax
You will need some regular sheet model wax which you will soften over a flame.
 When you receive the impression coping from Neoss, it will look like this. It comes with an implant replica already in the packet. You can ignore the red bit for this. You don't need it for open tray impressions. |
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.
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. Another good tip is to prescribe your tray, for upper teeth, as a horseshoe shape. If you have a full palate, the impression material can form a really good peripheral seal making it difficult to remove the impression.
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. Keep the healing abutment safely. You will need it again. I like to soak it in 0.02% chlorhexidine mouth rinse until I need it again. Don't remove the healing abutment too early because the gingivae will start to recoil over the implant head and it will be sore for the patient to place the impression coping. If there is more than one implant then remove the healing abutment and place the impression coping one implant at a time. Also keep the healing abutments in order so that they can go back onto the same implants. They may be of different heights.
 Neoss healing abutment in place |
Fit the transfer device
Take a look at the top of a Neoss implant. You will see that it has six locating "slots".
 |
The impression coping has to locate into the slots in the head of the implant. Take an impression coping and place it into the implant with the screw end first. It has a plastic tube fitted to the other end....more of that in a minute. Screw the impression coping lightly into the head of the implant. You can hold it by the plastic tube to do this. A big advantage of the Neoss system is that you cannot screw the impression coping into the implant head unless it is properly located. The thread is deliberately too short to allow you to do that. In other words, if you are screwed into the implant head then you are properly located.
 |
The screw head is accessible through the plastic tube. Take the screwdriver again and secure the impression coping fully onto the implant by screwing it finger tight. The screwdriver will go down the tube to engage the screw head. At this stage some people recommend that you take radiographs to check that the impression copings are fully seated. This is not necessary with the Neoss system because of the short thread. However if it is the first time you have done it and you are not sure, you may prefer to take a radiograph. You will be checking that there is no gap between the head of the implant and the impression coping. (There won't be).
Try in the tray
Try the tray in the mouth and make sure that the impression coping has some clearance around it in the window.
 |
Lay wax over the tray window
In order to prevent your impression material from flowing all over the place, lay some softened wax over the tray window and onto the surrounding acrylic. Place the tray in the mouth again and push the impression coping through the wax.
 |
Take the impression
Mix your impression material and load the tray. You may like to syringe a little around the impression coping too. Place the tray in the mouth so that the impression coping pokes through the wax again.
 |
Unscrew the impression copings
When the impression material has set you get to see the big advantage of the plastic tubes. Take hold of the end of the tube and give it a sharp pull. You can use a pair of pliers for this if it is difficult to grasp. You can now see right down, through the impression material, to the screw head.
 |
With some other systems you have to go searching with a scalpel through the impression material to find the screw head. The Neoss plastic tube is really useful to avoid that problem. Now unscrew the impression coping from the implant. If you apply a little downward pressure as you unscrew the impression coping you will hear and feel a click as the screw reaches the end of the thread. You can then be sure that it is no longer engaging the implant.
Remove the tray
Your impression coping will be picked up in the impression. If you feel undue resistance check again that the coping is fully unscrewed. You have now transferred the position of the implant to your impression. In some ways this is a lot easier than a conventional crown and bridge impression. You haven't had to worry about margins. It was all taken care of by the impression coping.
 |
Replace the healing abutment
All that remains is to replace the healing abutment. Just screw it back in finger tight.
Screw the implant replica onto the impression coping
You don't have to do this yourself, your technician will do it for you if you ask. However some operators like to make sure before sending the impression to the laboratory. Simply take your implant replica and place it onto the impression coping inside the impression. It will engage in the same way as before. Use the screwdriver again in the other end of the impression coping to finger tighten the replica into place. Hold the implant replica between your fingers of one hand and the screwdriver with the fingers of the other hand. Don't try and tighten the screw whilst supporting the impression. That could lead to the coping getting turned in the impression and then everything will be wrong. Your impression is now ready for casting by the technician.
 |
To understand why the impression technique is the way it is, it is very helpful to see how the technician converts this impression into a working cast. You can see that on this video. It also shows how to hold the implant replica whilst tightening the screw of the impression coping.
Crown and bridge stuff
You now need all the other bits of conventional crown and bridge like an opposing impression, shade etc.