Zirconia all on 4 - I am wondering if the zirconia will feel heavy?

If you put a Zirconia arch in one hand and a PMMA or PEKKTON arch in the other, you WILL fee a difference.  There are pros and cons for each, but ALL are fantastic options.

Hello. Permanent prostheses of All-on-4 system are mostly made of 3 materials.1-Acrylic: The lightest one but prone to stain and fractures. Mostly used for immediate temporary prosthesis.2-Zirconia: It's a kind of metal which has to be made thick enough to avoid fracture. Despite its aesthetic advantage, it sometimes may be risky in terms for fracture due to its rigid nature.3-Smart Hybrid Metal fused porcelain:It's an innovative material which differs from traditional metal fused porcelain. A standard metal ceramic has 45-50 gram weight while this material has 20-25 gram. This is due to the gappy metal framework which is also being used in civil engineering to make constructions lighter.

Zirconia wont feel heavy since it is screwed in to your implants, but it may wear down your lower teeth because the zirconia material is much harder than enamel on our teeth. It is almost as hard as diamond. If you hold the zirconia prosthetic in your hand it would seem heavy compared to the small size, but in your mouth you cannot tell.

I have hundreds of patients that have large bridges or full arch (all-on-four) type restorations and the vast majority of patients absolutely love them! True, zirconia is heavier that other restorative materials but it is also much much stronger for the long term.  As a general rule, zirconia can be a better long term restorative material due to the durability and natural cosmetic results.

Zirconia is usually bit heavy, but people get used to it very fast. The weight also depends on the designing of the the crowns. Also some prosthesis like Prettau Bridge are milled from a single block of Zirconia, they are usually heavy . Versatile dental labs can do titanium frameworks upon which zirconium crowns can be cemented. Please don’t compare these prosthesis with removable complete dentures, as these immediate dentures are not only big, but also have the most uncomfortable palatial extensions. So to conclude, these screwable prosthesis after All-on-4 are very comfortable. Always better to prefer clinics with In-house dental lab, for precision and quicker customized solutions. 

If you are calling immediate interim dentures heavy then you must reconsider getting zirconia as it will be definitely heavier probably one of the most heaviest prosthesis you can get.
Considering the fact that you have severe amount of bone loss that's why your dentist choose to do all on 4 implants instead of all on 6. your prosthesis will not just replace teeth but the whole amount of bone lost as well.
There are quite a few options of prosthesis which you can choose i am elaborating them so you can understand pros and cons of each of them
Hybrid prosthesis- It is one of the most traditional way of fabricating prosthesis for all on 4. titanium framework with acrylic wrap around has been successfully used since many years and and still is one of the most economical solution as prosthesis for all on 4.
Has resiliency that reduces impact forces so that it is not transferred to the implant.Easily repaired should you sustain trauma, which is a great advantage.It does stain over a period of time, but this can be readily cleaned and polished.This prosthetic denture is made of cured acrylic base; teeth can be dislodged; however, they are easily repaired.Acrylic is generally cheaper and lighter, but won't last as long as zirconia.Acrylic teeth have the longest track record.May wear and will chip, but they are easily repaired in a few days.Wear faster than natural teeth, but will not wear opposing natural teeth.
2. Smart Composite Hybrid Prosthesis-It is combination of milled CO/CR and Milled Monolithic Composite.
Strong, rigid metal bonded to resilient hybrid compositeHighly polishable, can be repaired in the mouth.Less likely to chip compared to acrylic options.Lightweight compared to Zirconia.Very durable, may not be quite as durable as full zirconia.
3.Zir.MAX.M Hybrid(Monolithic Zirconia Screw Retained Full Arch Prosthesis - One of the most esthetic and durable restorations for the edentulous patient seeking an implant-retained solution exhibit a flexural strength of up to 1200 MPa, allowing you to deliver a restoration that looks natural and definitely heavy.
This is the option with the greatest combination of strength and cosmetics.Most patients feel this is the option that is the closest to the feel of their natural teeth.It has been around for approximately 10 years.As far as durability, zirconia will tend to be the most durable option and will be least likely to chip.
4.PMMA/PEEK- these are few alternatives to zirconia with high aesthetics and light weighted.
5. Porcelain fused to metal prosthesis-
Requires the least vertical of any other hybrid option.This is the most esthetic option.Is more likely to chip than Monolithic Zirconia, but has decades of acceptable longevity.Typically the most expensive option.Has the most versatility of treatment solutions.
 

each case is different and also the bone structure that at the end is the one that is going to be supporting all the masticatory forces,hybrids can contain and supoort real good but they might change color with time but will be more implant friendly with vectors of force,if your case is ideal for porcelain its a great option also PMMA,and choosing the right specialist is a must,many doctors they advertise they do it,but they will swithch you to another technique or protocol because they are not experts in ALL ON4,and can be a great solution on expert hands