I was wondering why are chin implant are so small, the largest offering horizontal projection increase by only 10mm?

Chin implants are available in a variety of sizes and shapes. In the vast majority of cases, off-the-shelf implants are adequate to create a pleasing facial contour. The size and shape are best dictated during a consultation between you and your chosen plastic surgeon. The best first step for you would be to arrange a consultation with a plastic surgeon that specializes in facial procedures. I hope this information is helpful.

Stephen Weber MD, FACS

Lone Tree Facial Plastic Surgeon

As you know, there are a variety of styles and sizes of chin implants that give varying amounts of augmentation to the chin.  In almost all cases, some style and size of implant normally exists that will be beneficial to the patient's appearance.  If for some reason you need more projection than an implant can provide, it's possible that some strips of GoreTex could be placed between the implant and the bone to give further projection.  Silicone chin implants have been shown to cause some bone erosion on some radiologic images, but this does not necessarily result in any physical change to the shape of the bone or any clinical problems.    

The sizes of chin implants that are available are based on what sizes are most commonly used. There are ways to increase the amount of horizontal augmentation of a chin implant by using  wedge or stacking technique with screw fixation for stability. Implants do not cause bone erosion which would be an active inflammatory process. Rather some chin implants may settle into the bone a few millimeters through a passive process of the bone adapting to pressure of the chin implant sitting on it from overlying soft tissue recoil.