How many sessions of fractional laser is required for mild to moderate acne scars?

With regards to your question,

The number of sessions really depends on 2 main factors:

1. How your skin reacts to the treatment. For some individuals, good results may be seen after 3 sessions whilst others may require 6 or even more sessions.
2. The depth of penetration of the laser. If mild settings are used then more sessions may be required and results may not be as satisfactory.

Additionally, as Dr Chua CY has pointed out, combination treatments usually yield more effective results. I personally do not usually just stick with one kind of treatment modality to treat acne scars.

Hope that helps.

All the best!