“Is brushing your teeth once a day okay?”

Twice is better then once. Don't forget to floss.

It depends on how thorough your brushing is. It also depends on your diet and life-style. If those are healthful, correct and thorough brushing along with proper flossing once daily may be adequate.

Best twice a day. Floss twice a day. Use Listerine first, swish for 30 seconds, floss, and brush with Colgate SF toothpaste for two minutes, not less on every surface of your teeth. This IS IT!

As a general rule it's best to brush after each time you eat. Once a day is not enough to maintain proper oral hygiene and prevent dental problems.
Flossing once per day is enough.

The easy answer is; It depends on the person. Plaque (a film of bacteria) starts forming immediately after you brush but it takes 12- 24 hours to fully form. Therefore, some people build plaque faster than others. There are many bacteria that cause plaque. Some bacteria is very aggressive and can cause damage quickly were other bacteria is not as destructive. Plaque needs to be removed on a daily basis so it doesn’t become destructive and cause periodontal disease or harden as calculus. So it is important to brush daily, some people can get away with brushing once a day but my recommendation is to brush twice daily and floss to remove as much bacteria as possible to make your mouth healthy. There are also healthier foods to help remove plaque like apples, carrots, celery etc, so eating a lot of these in your diet can also aid in a healthier mouth.

Brushing your teeth once a day is better than none at all, but the American Dental Association recommends brushing two times per day for two minutes each time. Brushing your teeth helps remove plaque buildup, which is the soft, sticky film on your teeth that contains millions of bacteria. The bacteria in plaque cause cavities and gum disease if not removed regularly
with brushing and flossing. When it's not removed in a timely manner, it turns hard and hard to remove, at which point it is referred to as calculus or tartar and only a professional dental cleaning can remove it effectively. The bacteria in plaque and tartar are what contribute to bad breath. When you wake up in the morning with 'morning breath', it's because that plaque has been accumulating on your teeth throughout the night. Brushing helps remove it and freshen your breath so your co-workers don't mind working with you! Brushing your teeth is also a big way to prevent cavities by using a fluoridated toothpaste. The fluoride in toothpaste helps to remineralize and repair teeth that have cavities starting by replacing the building blocks in the teeth that have been lost.

You should brush at a minimum twice a day and floss once a day. Some patients need more than this, but I would say that 2x/day is a minimum.