The "nubs" or "rounded spike things" on this treat is contributing the most when it comes to THIS SPECIFIC TREAT. The idea is that while your dog chews on it, the nubs rub up against and gently massage the teeth, gums and cheeks. The different height between the grooves of the nubs and smooth parts of this bone will help reach parts of the teeth that a 100% smooth bone won't (imagine dog biting into it, teeth landing in between 2 nubs, dog gets more surface area of the treat rubbing on teeth than if it were just smooth or flat).
Also, powdered cellulose is, in my opinion a "crap ingredient" but it is as least good for one thing, it's an emulsifier. It is a low grade fiber source that is unnecessary for digestion if your dog is on a well balanced diet BUT it does add to the texture and tartar scrape-ability of this bone. This bone sounds like a tasty treat version of a "dental bone", maybe one I'd only recommend as a go-to last resort over other options (not wanting or able to brush your dogs teeth BUT your dog is also extremely picky and at least you can get your dog to chew on this??). It is definitely a "treat" not a necessary dietary supplement.
Other ingredients listed are not known as being "good for teeth" but alot of extra ingredients are added to dental treats, and the treat still serves it's purpose anyways. Wheat starch is specifically bad for tartar build up though.