Which is best for All-on-4, acrylic or porcelain?

The answer is it depends. The zirconia (all porcelain) option is the strongest.  The acrylic option is not as strong but often looks better cosmetically. Having an upper and lower zirconia all on four will often produce teeth clicking sounds that patients find annoying.
Then there are biting and wear issues. Zirconia is a better choice when the opposing teeth are natural or crowns especially if grinding is an issue. if an upper and lower all on four are done it the same time I will often make the top zirconia and the lower acrylic. Excessive grinding with upper and lower zirconia can place heavy strain on the dental implants and cause failure.
People lose teeth for different reasons including cavities,gum disease ,grinding and sometimes a combination of more than one.  The plan to replace your teeth should consider those factors. Your dentist should be able to guide you to the pros and cons of both materials and make a decision that would be the best for your situation 

Having done numerous cases it really depends on a number of factors. If you are a heavy teeth grinder then you will wear thru acrylic quickly. However if you have natural teeth, acrylic will be kinder to them. Also, the cost of zirconia is more, so you need to take that into account.

Most of the all on four prosthesis are made of acrylic, however many patients do upgrade to the Zirconia. At our office we do both and the Zirconia although is stronger and more aesthetic it is considerably a heavier prosthesis. Most patient won't notice the difference in weight.

Hi and thank you for your question.All the cases we do in our office are done with a final prosthesis made out of Zirconia. Acrylic prosthesis are subject to wear ,teeth can certainly break off and will at some point need to be replaced. Zirconia prosthesis are the best solutions, as these are unbreakeable, more esthetic and highly polished, so they won’t accumulate as much plaque as the acrylic prosthesis. So this are more hygienic.Good Luck,Dr. Juan C. Arroyo Oral and Maxillofacial Surgeon 

This is a very common question regarding All-On-4 dental implant treatment.  Some dentists say that porcelain or zirconia is "Always" best while others say that acrylic is always best.  For me, after doing more than 1,000 of these cases, the answer is that these teeth are very patient specific.  Items that must be considered are as follows: 1) what are your opposing teeth (natural, denture, acrylic hybrid, zirconia); 2) are you a grinder; 3) what is your budget; 4) what is your age; 5) are the implants being placed into regenerated bone; 6) what is the anterior-posterior spread of your implants
There are other factors to consider, even in addition to these.  If your dentist says that one type of restoration is "always" better than another, be wary.  One size does not fit all.  This is true for just about anything in life.  If one option was "always" the best, the other options would be eliminated.

There are pros and cons to each material used when restoring All on Four dental implants. The harder material, porcelain or zirconia, will look and feel more like teeth but don't wear down like acrylic or PMMA does. Instead of wearing down, they can fracture (but usually don't). Acrylic is not likely to last as long as zirconia, so one should budget for future costs to replace or upgrade. Acrylic by itself is not strong enough long term all by itself, so it should have a frame of some sort made out of metal, PEEK or PEKKTON but even those materials are so new that we aren't sure how long we should reasonably expect them to last.

there is a protocol, of ALL ON 4, BY NOBEL, developed by Dr Malo,and it says that needs to be a hybrid, you can  certainly perform zyrconia,but this will depend on the patients bone condition, and also on the diagnose from your doctor,this is not a matter if its going to be a long lasting material or not, this is something that if you are wearing down, because its hybrid, and you switch to zyrconia, then the bone will absorb that high impact of the structure, not because its zyrconia, it will not affect the bone, so you need to find out a ethical doctor.