Thank you for providing the excellent photographs and also your queries!
There are various clear aligner options in the market now to straighten teeth, but invisalign has been in the market for the longest time and continual research and development in their aligners has allowed it to be one of the most reliable options for clear aligners.
To correct teeth alignment (crowding), the various methods to create the space would involve
1. Expansion "whereby we widen your teeth sideways" allowing you to have a wider and more beautiful smile
2. Protrusion whereby the front teeth are flared more forwards ( which is what we would minimise doing since protrusion is your main concern)
3. Interproximal reduction whereby we gently file the sides of teeth to create some space
4. Distalisation whereby we move the teeth backwards to minimise the flaring and protrusion of the front teeth.
5 Extraction which involves removing one or more teeth ( which sounds like you are quite averse to doing)
"If extraction is required, would it cause a flat profile after treatment?"
There are various factors whether a case requires an extraction, and the decision to extract the teeth would depend on several factors, which your dentist/orthodontist would be able to advise you clearer at the dental clinic.
At times, this would also involve taking some X-rays to check on the skeletal and tooth position to ensure we give you the best possible solutions to your primary concerns. We generally try to minimise extractions, unless really necessary as we believe we should "EXTRACT mainly for the FACE, rather than for the SPACE."
Hope this helps!
Best Regards
Dr Ooi
