What's the best material available now for All-on-4s? Is there continuing research and development into newer materials?

There really are only two choices: 1- time honored titanium in use for 40 years and ceramics. Only one company makes ceramics because the demand for ceramic implants is so low. The demand is low because titanium implants are uniformly successful. People who fear a titanium allergy, (with no proof whatsoever) or generally have phobias sometimes request ceramic implants. I personally have three titanium implants on my mouth replacing extracted teeth. I have zero problems. I have been placing titanium implants with great success for 30 years. And we have conducted scientific literature review with ongoing Resident training for decades.

Hello. There are many factors to choose the prosthesis material inAll-on-4 cases. For example patients with severe bone atrophy may have need bulky prosthesis to support their lips and soft tissues. In that circumstance the use of a zirconia prosthesis will be very heavy and susceptible against fractures. Or another patient may have less interoclusal space and this space does not allow for an acrylic prosthesis with metal framework .So that, I recommend to choose the right doctor and take your doctor's advice

Different material prostheses are used in different situations. There are specific indications for use of these different material types. The choice of material has to be based on individual patient conditions and clinical situations. Certain properties of certain materials is what offers the clinical applicability for a successful outcome. Dr. Ajay Kashi

A few of the examples you cite are registered trademarks created by individual dentists or labs to uniquely identify their own approaches. However, whether acrylic, PMMA, zirconia, nano composites or a combination of any of these with titanium substructures are best for you depends on your own set of personal circumstances. The best advice is to find an experienced doctor you can trust, then follow his/her recommendation on which material is best for you. Factors to consider include whether you have a tendency to grind or clench, what are the opposing teeth made of, and how much money you are looking to invest.

PMMA (Polymethyl methacrylate) is mostly used as a temporary prosthesis. For the called "Teeth in a Day." After three to six months of implant placement, you can load those implants with a Prettau Zirconia bridge, a durable and strong material. PMMA is for temporary teeth; Zirconia is for final teeth.

Zirconia is the strongest and hardest, but many people still use hybrid titanium with acrylic teeth. The advantage to this is the weak point is the acrylic teeth, so if a tooth breaks its an easy fix, whereas if the implant or connection is the weak point (because zirconia is so strong), it is much more difficult to replace an implant.

We are talking about two separate parts here. The implants themselves and the restorations to be attached to these implants.
Implants:
As far as the implants to be used, there are two mainstream options: Titanium and Ceramic implants.
Titanium Implants- The very foundation of dental implantology was initiated after the discovery of natural bone attachment to titanium. The scientific evidence, years of successful clinical cases, and a wide variety of applications have generated high levels of trust regarding the performance of titanium implants. The real difference between one implant system/brand vs another is found in the quality controls used by different manufacturers. All major brands have trustworthy quality controls, and even offer lifetime warranties on their products.
Ceramic (Zirconia) implants- Perhaps the most distinctive yet simple difference between titanium and ceramic implants is the color. As a white material, the aesthetic properties of ceramics are self-evident, At present, the clinical indications are limited compared to titanium implants. The current use of ceramic implants as a solution for tooth loss is mainly for single tooth replacement and bridge cases. There may be additional limitations in surgical and loading protocols.
As far as the restoration is concerned, there are several options in the market for you to choose from. Research and innovation are always part of the science of dentistry, and as new materials and techniques are developed, so are new product offerings in the market:
Restoration:
Here is a breakdown of the most common options for all-on-4 restorations:
PMMA (Poly(Methyl Methacrylate))- This is a type of acrylic that is lightweight and easy to manufacture. Generally speaking, dental offices offering “teeth in one day” are quickly fabricating these as long term restorations for you. More advanced dental offices use these only as a temporary restoration until a more robust and durable restoration can be fabricated.
PROS: Manufactured quickly, Can be relined, good options for gum shades, low cost
CONS: Not durable, weak structure, prone to breakage, not repairable if it breaks, stains easily, wears out quickly.
SOLID ZIRCONIA- One of the most commonly offered types of restorations. The whole appliance is milled out of a single piece of zirconia.
PROS: Very strong, High stain resistance, very low wear rate.
CONS: Not repairable if it breaks, poor compatibility with jaw bone (due to rigidity), clinky ceramic sound, opaque/dull appearance, high amounts of forces placed on implants, very heavy.
TITANIUM /ACRYLIC HYBRID- A titanium bar is milled, to which acrylic teeth are bonded. The HYBRID premise is to give you “the best of both worlds”.
PROS: Softer bite, repairable if it breaks, can be relined
CONS: Prone to breakage, Odd “soft bite” feeling, limited shade options, low stain resistance, teeth wear out quickly.
XIRCON HYBRIDS (ULTRA & ULTIMATE)- Highly advanced biomaterials are used to fabricate the bar, and teeth. These materials have been used to fabricate bone prosthetic for a long time, so they have a proven track record of bio-compatibility, flexure, and durability. These characteristics combined with advanced manufacturing processes give you the most advanced product in the market.
PROS: Fully repairable, Very customizable shades of gums and teeth, optimal translucency, shock-absorbent bite, real teeth feel, minimal forces on implants, best compatibility with jawbone, lowest wear rate, very high stain resistance.

Since there is so much happening, it would be hard to say definitively, there are pros and cons to all materials. The best thing to do is find a provider you trust, and then decide with THEM what is the best material. Zirconia is strongest, but hard to repair if something needs fixing and often more expensive. Every material has a different fee, so that might be a factor as well.

More than thinking in materials, you should be more worry about the doctor who performs it, all the materials are good, and this will depend on the bone quality and density.

You can certainly find a solution with this 2 proceedures ,the first one is SNAPINDENTURES,with 8 narrow implants ,8 uppers and 8 lowers you will have a removable solution that will change your life,and also there is a second proceedure ,The ALLON4,which is a screw retained bar that is connected to regular implants that are placed in strategic positions,2 tilted and 2 straight,and you will have a strong solution and also cosmetic.

Based on what you say here,it seems that you are a candidate,a clinical and x ray diagnose needs to be done,and its important for you to choose the right ALLON4 Specialist.

Shape,size and color can be changed and you will love the results

Just like with most things in dentistry, the best option depends on the situation. The most common materials are zirconia, which is very strong but can also be brittle, and a metal bar under acrylic/denture teeth, which may wear down faster but is more repairable and less costly. PMMA is becoming more common as well, but some of the other materials are fairly new to market and are not as tried and true.
The restoring dentist, surgeon, and dental lab typically plan these cases together. I recommend finding a treatment team you trust, who can thoroughly evaluate your situation and discuss the pros and cons of each material based on YOUR needs.
The dental lab will be the one with the material and fabrication expertise so you can even ask the lab for more specifics on each material if you would like.
Also, the first All-On-4 is normally temporary while the implants heal, so the material choice can be changed later on if needed. I wouldn’t worry too much about the final prosthesis material now, and more about finding a doctor you are comfortable with.
I hope this helps!