What are the problems and maintenance issues with all on 4?
If you have an acrylic all on 4, according to Dhima it will almost certainly have problems of some sort at some time. The main issues we see are minor and involve the acrylic. Since acrylic is fairly weak we see damage in the form of teeth popping off, teeth wearing down, and acrylic breaking. The teeth popping off and acrylic wearing down can be avoided with use of a protective night guard, but given enough time these things are to be expected. Bozini shows in his 2011 study that this is common even after only 5 years of use.
If you are a grinder or clencher of your natural teeth you are likely to continue this habit and are at higher risk for problems. The costs of these issues will range from a few hundred to maybe a thousand in the worst case. To repair a broken AO4, the denture must be removed and given up for an entire day so that the lab can work on it.
Another issue that can happen is that a dental implant can fail. After the first year this is highly unlikely to happen in any given year. We usually over-engineer all on fours now to be all on 5 or more so the loss of one implant will not impact you. However, the loss of one in a critical are when there are only 4 can start a domino effect of losing more implants and eventual loss of the all on four. We have personally never seen this and it is very rare, but it can happen given enough time.
How to clean your all-on-four is on our all on 4 maintenance page.
We recommend yearly dental visits and cleanings and x-rays every 5 years, unless there is some sort for issue or concern. The details for cleaning and maintaining is in the link on the above title.
The rest of this page is more technical information on the all on 4.
The risk factors for a maxilla AO4 were found by 2 investigators to include all of the following items, which are labeled with a 1 or 2 for the different studies. 1 Parel 2011 / 2 Khorshid 2014
Traits that indicate high risk for all on four problems.
- Male 1
- Opposing natural dentition 1 or long term fixed implant supported full arch prosthesis 1-2
- Poor bone density 1-2
- Non-axial loading >20 degrees 2
- Nonrigid splinting 2
- Parafunction 2
- Thermal surgical injury if guided 2
Traits that indicate less risk for all on four problems.
- Systemic factors 1-2
- Local infection/pathology 1-2
- Opposing complete arch implant supported prosthesis 1
- Bone volume 1
- Smoking 1
- Bruxism 1
- Distal posterior implant site 1
- Cantilever 2
- Improper AP spread 2
- 6 or less implants 2
- Inadequate length/size implants 2
- Uncooperative patient 2
Dental research on the all on four will continue to grow as studies mature.
All on 4 is as good as an all on 6 according to Branemark 1995.
All acrylic all on four holds up as well as an all on four with a metal substructure. Crespi 2012 believes the acrylic may be beneficial to the implants as a shock absorber. That gives me further interest into using Pekk as a framework.
Double arch all on four has more complications than single arch, but survival is same according to Nobre JPD 2015.
EMG shows muscle activity same for dentate and all-on-4 but much less for denture patients according to DeRossi 2013.
Bidra 2012 lists the surgical options for gingival display all on four cases
- Ostectomy can be done with a saw or chisel for mild to moderate gingival display, but must have enough space beneath sinus and/or nasal floor.
- Lefort I was one suggestion but seems like a highly unrealistic option.
- Orthodontic intrusion is an option if just the anterior has supra-erupted.
- Plastic surgery is another great option for the right candidate and would utilize procedures like lip repositioning for hyper-mobile lip or Botox.
- Finally, one could abandon the all on four option and make an overdenture.
The bone loss on tilted implants is the same as vertical implants according to the meta-analysis by both Monje 2012 and Baggi 2013.