This is a very good question as many people have already spent thousands of dollars on dental implants in their mouths.  However, there are some factors that can affect whether it will be possible to use your existing dental implants as support for your All on 4 or any sort of implant denture.  The first question I’m going to ask is, “are the current implants deep enough in the jaw to create enough space for the prosthesis?”

A prosthesis is defined as an imitation body part.  In this case, we’re talking about the actual gums and teeth that you can see and chew with.  The prosthesis must be a certain thickness or you risk the prosthesis fracturing when you chew.  There are many different types of prostheses for All on 4 or implant dentures.  These include Zirconia, nanoceramics like crystal ultra, acrylic, etc.  If any of these materials are not thick enough, then they risk fracturing as you see in this image.

These prostheses all must have a minimum thickness, depending on how strong the material is. The stronger the material, the thinner it can be. The weaker material, the thicker it must be.  For instance, a hybrid prosthesis, which is a titanium substructure with acrylic gums and teeth on top of it, must be at least 12-15 mm thick to ensure that there is enough bulk of material so it doesn’t break when chewing.  In order to ensure your prosthesis will be able to fit inside your mouth and not affect your bite height, also known as the vertical dimension of occlusion, your surgeon will have to ensure that the top of the implant to the edge of your prosthesis (or the edge of the tooth) has to not violate your vertical dimension.  In order to maintain that height, your surgeon will have to “clear space” in your mouth by bringing your bone and gum level down a few mm.  Your implant will be placed lower in the bone than it would have been normally had your implants been placed for a single tooth or bridge.  As a result, it’s most likely that your existing implants in your mouth most likely won’t be able to be used for an All on 4 or implant denture prosthesis.  However, every case is different so you would need a consultation to see if your existing implants could be used.

Also, there is another factor that is involved with the ability to use existing implants.  Are the existing implants placed at the proper angles?  If you’re doing an implant overdenture, also referred to as snap-on denture, then it’s critical that the implants be placed parallel to each other.  If the existing implants aren’t placed parallel to each other, they will give you issues later on with how your overdenture will fit and stay on when you’re chewing.

Another factor would include parts compatibility.  There are so many different implant systems out there.  Is your existing implant system compatible with an All on 4 type of system?  Your existing implants would need to have multi-unit abutments available.  Each system tends to have different size screwdrivers, parts, and pieces, that would complicate taking your prosthesis on and off, therefore allowing more potential complications to occur if your dentist gets confused.  

In regards to getting parts for overdentures (snap-on dentures), it’s pretty easy to make sure you will find compatible parts for these types of dentures.

If you need a dental implant now but you don’t need to take all your teeth out for an All on 4 right now, or you’re saving up for a future All on 4, then one piece of advice is to tell your dental surgeon that you would like to have your dental implant placed deeper so you can use it for a future All on 4.  This is not always possible due to several factors.  #1, it is more difficult to put a crown and abutment on an implant if it’s between existing natural teeth.  #2, you may have different anatomical factors such as your maxillary sinuses and your Inferior Alveolar Nerve that won’t allow you to place your implant too deep.  Hopefully, this information is helpful when considering a future All on 4.