This question can depend on a cornucopia of different reasons. You can be more susceptible to getting cavities depending on your: age, dietary habits, saliva production, genetics, medications, and the list goes on. The more susceptible you are, then theoretically cavities can attack your teeth quicker. So if you are more at risk for cavities, you should definitely be seeking out your dentist for regular check ups every six months.
We know that diets high in processed sugars can cause cavities. Bacteria in our mouth eat and process those sugars and produce acids that eat away at tooth enamel starting the cavity. Sugary, acidic drinks have a similar effect and are capable of eroding away tooth enamel, also starting the cavity.
One interesting study set out to determine how quickly cavities can form using some poor dental students as lab rats back in 1970. Luckily, I made it through dental school without having to confirm the results myself. Students were instructed to swish a sugary sucrose solution in their mouth 9 times a day just like they would with mouthwash. They were also instructed to not use any oral hygiene throughout the study, no brushing or flossing. By the 23rd day of doing this, it was apparent that cavities were starting to form on some of their teeth. After this conclusion was made, the students were back on their normal oral hygiene schedule and the cavity process stopped and remineralization of the teeth occurred.
So on paper, 23 days could be the magic number for how quickly a cavity can form. That being said everyone is different, and everyone has different risk factors for cavity formation.
Professionally speaking, never ever, for the love of god, try to repeat this study. Always try to brush twice a day, use floss and mouthwash rinses, and of course check in with your dentist every six months or so!
Refer to this link below from one of my colleagues, Caitlin Rosemann, if you would like to learn more about preventing these cavities.
The Author of this post does not assume any liability for any injury and/or damage to persons or property as a matter of products liability, malpractice, negligence, or otherwise, or from any use or operation of any methods, instructions or ideas contained. The foregoing parties will not be liable for any direct, special, indirect, incidental, consequential, or punitive damages as a result of the reader’s use of this information.