This is something that may also happen by wearing dentures. They are others that have developed fine wrinkles that run into their lips giving them the lipstick lines or the smokers lines . Collagen is commercially available through plastic surgeons, but before having this procedure, you must first pass a collagen allergy test. Its advantages are, it does not require surgery and it is relatively inexpensive. Its disadvantage is that it is not permanent and usually lasts 3-5 months.
Fat injection is another similar method.
I usually do not recommend it because as the fat gets absorbed the lip can become lumpy and have an irregular surface and appearance. Gortex is a synthetic non-dissolvable material that can be inserted at the periphery of the lip giving it more contrast as well as eliminating the lines that run into the lips. Although it is also available in a form for augmenting the body of the lip, I feel that it is not ideal for this purpose because it feels too hard. Alloderm is natural collagen matrix that is harvested from donors. It has the same consistency and feel of the skin.