What is a one-sentence summary of the following article?
Apples, celery, and carrots are crunchy, and eating them can help scrub surface stains off of your teeth. In addition, they may kill bacteria and improve your breath. These products (milk, cheese, yogurt, etc.) contain lactic acid, which might help protect your teeth. Some of them can also help whiten your teeth and/or prevent some stains:  Hard cheeses can scrub some surface stains from your teeth, and block some stain-causers such as wine or coffee from discoloring your teeth, if you eat some prior to drinking. Eating dairy products is good for your teeth, but don't consume too much of sugary foods such as ice cream, as these can contribute to tooth decay. Sage has an antiseptic effect, and for this reason is even found in some mouthwashes and gargles. It can also help to whiten your teeth. Simply rub fresh sage leaves on your teeth. Strawberries contain an enzyme called malic acid that may help to whiten your teeth. You can simply rub a sliced strawberry on your teeth, or mash fresh strawberries into a paste and rub it on your teeth. Leave it on your teeth for five minutes, and then rinse with water. Brush and floss your teeth as normal afterwards.  You can add half a teaspoon of baking soda to the paste, if desired. Research shows that a strawberry paste will only remove surface debris. If you want more intensive whitening, seek other treatments. Natural bleaching agents found in lemon can help whiten your teeth; however, the citric acid found lemons can also wear away your tooth enamel, so you should not overuse this method. Simply take a slice of lemon peel and rub it on your teeth.

Summary:
Eat crunchy fruits and vegetables. Eat more dairy products. Use sage to scrub your teeth. Make a strawberry paste. Use fresh lemon.