Should get extraction and implant or root canal with build-up, posts, and zirconium crown on tooth #19 ?

This is a legitimate question.  If the tooth is not abscessed everyone agrees it is best to restore and crown it.  Without more information there is no easy answer.  I have a tooth with a root canal in my mouth for over 40 years.  There is no good evidence that an implant will last longer than a properly restored tooth.Extracting a tooth will kill brain cells and extractions have risks as does surgical placement of implants.  These include TMJ injury, sinus openings, nerve damage etc.  Root canal treatment is 90-95% successful when the teeth are restored and can last a lifetime.  The best scenario is to restore the tooth with a crown and avoid the root canal completely.  You would have been well served with a crown when the composite was placed.

The general rule of thumb for me and my patients is if you can save the tooth and are able to get at least a few years out of it, that's the route I would suggest. If saving the tooth is not an option or it is likely to fail very soon after restoration, we talk about extraction and implant placement. Implants are the best option only if a tooth has a poor prognosis or cannot be saved. 
Best of luck with this tooth!

u will get different opinions on this. but in my practice i always go for rct first and i give implant as option once rct is no more option/possible. remember implant is last option.