The five links in the chain of dental misery...

 Five[1] linkes in the chain of dental misery

1. Humans like sugar

2. Plaque can only be made from sugar

3. Plaque efficiently excludes oxygen

4. Normal, healthy mouth bacteria, when starved of oxygen, go into anerobic mode[2]

5. In anaerobic mode some mouth bacteria make lactic or acetic acid

6. Lactic acid disolves tooth minerla and causes gum inflammation.

[1] Well six then.

[2] Streptococcus mainly produces lactic acid; some species can also produce acetic acid and formic acid. 

Lactobacillus mainly produces lactic acid, butheterofermentative species may also produce acetic acid and, 

depending on the species and substrate, succinic acid.

Actinomyces mainly produces Lactic acid, but some species also produce succinic acid,acetic acid and formic acid.

The key acid is lactic acid, particularly from Streptococcus and Lactobacillus. 

No, NOOOOOOOOOOO, not flossing again...

 ...No, but a little background, and an explanation of why we dentists go on about it so much. Plaque isn't toxic or poisonous or anything like that. It's more-or-less starch. BUT it is very effective in preventing Oxygen moving though it.  If Oxygen could easily diffuse through plaque then most dental problems would never arise. Now you see where this is going, removing the plaque lets Oxygen in which stops the anaerobic activity immediately (aerobic respiration is fifteen times as efficient as anaerobic respiration). 

Correlation not equal to causation...

 The media and politician with an axe to grind, will conflate correlation and causation. I see this often because the correlation between heart disease and gum disease is being used to suggest that gum disease somehow causes heart disease. I even see this amongst proper academics. It is a highly misleading to say or suggest that gum disease causes heart disease. Check out the correlations on this web site:   https://www.tylervigen.com/spurious-correlations . I especially like the 'Google searches for how to build a light saber correlates with pest controllers in Washington DC'.

Just imagine you're a food manufacturer...

 ... You make food products. You have NO RESPONSIBILITY for the health of your customers. 'Do no harm'? Don't make me laugh. Your only responsibility is to stock holders, the owners of the business. Guess what, they're only interested in profit. To maximise profit you use the cheapest ingredients AND the ingredients that experience and your food technologists tell you will make the food most palatable. 

Brushing? Shirley that's straightforward?

 Yes, you'd think so wouldn't you. Brush your teeth...job done! Well, guess what, you can make brushing more effective and therefore more preventive. 'How!' I hear you cry. plaque hardens with time, so the longer the plaque has been there the more difficult it is to remove. CONSEQUENTLY[1] brushing more frequently boosts effectiveness. Example? Yes, if you brushed for four minutes once a day that would be much less effective than brushing for two minutes twice a day.

[1] Sorry about the shouting.

Biscuits, cakes, chocolate, sweets, I love them all...

We all love sweet things. It's a built in biochemical response and there no getting away from it. It can't be turned off and it absolutely will not stop until you are dead? (Sorry about that last bit I've been watching The Terminator again).  I think we all agree that sugar is a problem for teeth and the rest of the body. What can you do? 

Reduce - cutting down slowly helps, the endorphin reward system adjusts to lower levels of sugar.

Replace - substitute with alternative sweeteners like aspartame etc. Or even non-sweet thing, go nuts!

Refuse - try turning down sweet things occaisionally.

What exactly is plaque anyway?

Would Sir[1] prefer the long boring scientific answer or the tl;dr[2]?

The tl;dr it is then. It's the gunk created by mouth bacteria which has its malign effect because it prevents Oxygen reaching the bacteria in the lower levels. This forces the bacteria, starved of Oxygen, into anaerobic mode. Misery ensues.

[1] Other excellent genders are available. 

[2] Too long, didn't read. I'm down with the kids, me.