Infection can spread to adjacent teeth or sneak in alongside a loose filling or underneath a crown.
A wobbly tooth is likely infected and you might want to get it out to protect adjacent teeth.
I had a root canal in my 20s that failed 10 years later and was replaced by a bridge that had to be replaced every decade or so until a tooth supporting the bridge failed; so I ended up with two implants.
Implant technology is really good today. You will ultimately save money and misery by going straight to an implant if a root canal or bridge is suggested. You will still need to floss to prevent gum loss.
Even if you don't have good (or any) healthcare, simply thoroughly brushing and flossing everyday will make a world of differece. If you can scrape together a couple hundred bucks for cleanings once or twice a year, even better.
I spent years neglecting my teeth, really only brushing daily and doing nothing else. Once I started going to the dentist regularlyx I got incredibly lucky they weren't much worse. Minutes a day and a couple hundred a year will save you a lot of pain and money in the long run.
We'll likely find it also contributes to Alzheimer's (as, it seems, all pathogens and pollutants in the body seem to do).
those that fall to acute infection, or indeed gut/systemic infection, will show poor oral hygiene,
and both are implicated in diseases that shorten life expectancy.
This is probably the key of causation