If the chin is small but the jaw of good proportion then it may be appropriate to place a chin implant. However implants are made from different material and come in different shapes and sizes. They can come ready made, off the shelf or they can be custom made from a three dimensional model of the jaw.
Chin implants have limitations because they can not lengthen the chin and if the teeth are too far back they can make the crease between the lip and the chin too severe.
In appropriate cases a chin implant operation has the benefits of being a small procedure which can be carried out as a day-case. The incision can be hidden inside the mouth or the implant can be placed through a small incision under the chin where the scar will be hidden.