It's more complicated than a good brushing and flossing regimen.

Dentist Appointment
Credit: yoh4nn/Getty Images

Dentists would have you believe that a good brushing and flossing regimen paired with a puritanical avoidance of sweets is all it takes to keep your mouth a cavity-free zone.

We're not going to sugarcoat it: that's just not the case. The truth is, for reasons both in and out of their control, some people are simply more prone to cavities than others.

Scroll down for a few lesser-known reasons you might keep finding yourself under the drill:

Weak Enamel

Enamel is the hard, outer layer of your teeth that defends them against decay. Unfortunately, enamel can wear away, allowing bacteria and acid to sneak in and attack the softer layer below it, known as dentin. As Dr. Andy Gaertner of Gaertner Brothers Dentistry in Miami recently explained to Simplemost, some people are at higher risk for developing cavities faster because they have weak and fragile enamel. This can be due to genetics, or bad daily habits, like poor brushing or guzzling down sugary drinks which can lead to enamel erosion.

Your pH Level is Off

It might surprise you to learn that the human mouth functions a bit like a miniature ecosystem. Eating too much or too little of certain foods can throw the whole system off. Goodies such as candy, soda, bread and even natural fruit create an environment where bacteria thrive. Bacteria then, in turn, produces lactic acid, which causes tooth decay.

Tooth decay can occur when the pH level in the mouth is 5.5. (The neutral level is 7.0.) Your dentist can determine the acidity of your mouth using a simple test. Luckily, bringing your pH level back to balance is often as simple as eating more veggies and cutting out sugary snacks.

WATCH: 5 Affordable Ways to Whiten Your Teeth at Home

You're a Mouth Breather

There are a number of reasons people end up forsaking their nostrils in favor of their mouths. Whatever the cause, chronic breathing through your mouth can turn your gullet into a desert—prime real estate for cavities to bloom.

"Mouth breathing, for example, leads to dry mouth and with a dry mouth saliva cannot wash away bacteria, which can cause not only cavities but also gum disease," Dr. Gregg M. Festa, who owns a dental practice in Raleigh, North Carolina, explained to Simplemost.