Is Invisalign the Best Teeth Straightening Option for Really Crooked Teeth?

There are limits to all treatment options and there is not necessarily one treatment option that is "best". It's a relative question. Invisalign can correct and improve some very complex problems. Invisalign can also correct minor to severe crowding problems with or without removing teeth (extractions). In other words, you can get as complex as you want with Invisalign. (Note: A very, very limited number of providers have the skill to treat the very complex cases)
Complex treatments are not easy with Invisalign, but they can be accomplished. The most important factor in treating complex problems with Invisalign is the experience and skill of your doctor. For doctors, using Invisalign is an acquired skill that has its own unique skill set that is only learned through experience. There is no special school that teaches Invisalign.
Of course, there are limitations to Invisalign as there are with traditional braces. There are some things that Invisalign does better than traditional braces and vice verse. A good experienced provider will be able to give you the advantages and disadvantages of your treatment options. The best option, in my opinion, is always a combination of what is in the best interest of the patient from a health perspective and what achieves the patient's specific goals. Doctors have a hard time understanding,sometimes, that patients are not always looking for "perfection".

For the front teeth (upper or lower) that are really crooked, Invisalign is the best option. We are slightly uncomfortable with back (molars) teeth being "out of tone" for Invisalign treatment.