I had rhinoplasty 2 years ago and am unhappy. Can dorsal lines be restored?

It is best to be seen in person to determine what might've caused your issues and what can be done to improve the nose.  

It's very difficult to tell from the photographs, however the nasal bones can be narrowed with osteotomies. Spreader grafts are placed in the midportion of the nose to restore the dorsal aesthetic that lines  when the upper lateral cartilages are concave. A thorough in-person examination is going to be required to make a determination about can be accomplished with a revision rhinoplasty. Revisions are much more difficult than a primary rhinoplasty,  so choose your surgeon wisely based on extensive experience

you appear to have had a slightly over-resected dorsum which yields a blunted appearance and 'inverted v' deformity from the front view.... the solution to this issue is to properly place bilateral spreader grafts... this restores the 'keystone' area and the relationships between the nasal bones, dorsal septum and upper lateral cartilagesgood luck

There are a few options available to bring your bridge back to where you would like.  To learn which options are best for you, I would recommend you consult with at least 2 board certified facial plastic surgeons who are experienced in facial cosmetic surgery, specifically revision rhinoplasty.  Ask to see numerous patient before/after photos.  I would recommend you have digital computer imaging performed during your consultation so that you can see how your nose would appear following revision surgery.  This also ensures that you and your surgeon are in agreement as to the desired result.  Best,Dr. S.