Root canal on front upper tooth four years ago. do i need to get a crown/cap essential now?

Maybe Not: Root canals do weaken teeth. Biting forces are very heavy on back teeth and depending on your bite, generally much lower on front teeth. If a large portion of the tooth is missing from decay or fracture, then a crown would be appropriate to regain strength. In my practice i probably recommend crowns on front teeth 20% of the time, 95-98 % on back teeth.

See your dentist: Only your dentist can make this treatment decision, and only after he/she has had an opportunity to evaluate your specific and individual situation.

Depends: Depends on circumstances. Ask your dentist for opinion. Consider second opinion.