Wonderful question! The best materials will depend on several factors such as your teeth alignment, bite forces (history of clench or grind habits), cosmetic concerns, and whether or not the opposing teeth are natural and what condition they are in. Zirconia is definitely the hardest material and is very durable and has very good aesthetics. Porcelain ceramic will give the highest cosmetic result but can be more expensive. Another option is hybrid composite which combines high aesthetics with a hardness that will not damage opposing teeth. It also has the advantage of being repairable in the mouth. Acrylic bonded to a metal bar was the original All-on-4 material and is still used in some situations but has the highest rate of breakage and wear. I hope this helps you to make the best decision for your needs!
