What's the number of hairs needed for maximum thickness in a philtrum hair transplant?

Thanks for the question. Based on your photos, you might be a good candidate for hair transplant. I recommend you to contact a Board Certified Surgeon for consultation. I wish you all the best. 

Following hair transplant the donor area is safe for combing after just a few days.  The recipient site should be avoided for a longer period of time.  By 2 weeks is likely a safe time to comb, but some would advise sooner.  It is best to get a recommendation from your surgeon and follow th...

Rogaine or Propecia will not restore front hair line.  Hair transplant surgery is an option to restore your front hairline. 

It is always a good idea to follow up with your doctor. You don't have to be upset.  If you believe something is not right, just call your doctor.  Transplanted hairs fall out weeks after surgery.  It starts to grow several months after surgery (6-12).

No growth after 1 year and 8 months means no growth.  Your surgery was likely a failure.  It is a good idea to follow up with your doctor for a recheck.

You can use a laser comb but it probably will not help.  Laser combs are safe to use but its efficacy is controversial.