It was early in the morning when I felt the painful sensation surge through my mouth. I had left my bleaching trays on my teeth while I slept the night before and was paying for it now. Photo Illustration by Megan Weltner Blinding white: Leaving whitening strips for longer than directed dehydrates the teeth, leaving them sensitive. Although whitening your teeth can leave you with a seriously sensitive mouth, says Pam Gotschall, certified dental assistant in Prairie Village, it is perfectly safe if you follow the directions. "People always think if they leave the trays in longer or the strips on for extra time it will make their teeth even whiter, but there is a point where the bleach stops working and they are only dehydrating your teeth." Gotschall says. "The dehydration causes the severe pain." Americans spent more than $2.3 billion on teeth whitening in 2008, according to a study conducted by the American Dental Association. From whitening strips that you can by at your local grocery store to thousand-dollar whitening procedures, people can't seem to get enough bleach for their pearly whites. Gotschall says because there is such a demand for these products, the ADA has been doing a lot of research to make sure there are no negative short- or long-term effects. VERDICT: GOOD FOR YOU, IF YOU FOLLOW THE DIRECTIONS Megan Weltner That's Sleeping without brushing your teeth DISGUSTING You fall into bed after barely finishing homework at 3 in the morning. Brushing your teeth may be the last thing on your mind, but you should know what will happen in your mouth when you skip brushing your teeth. Lack of proper oral hygiene also creates foul odor in the mouth. Claxton says using a tongue scraper helps keep your breath fresh. Claxton recommends brushing for three minutes in the morning and at night, and flossing "Different types of bacteria reside in the mouth and they can be really aggressive and active overnight," says Laura Claxton, registered dental hygienist at Enhance Dental Care of Lawrence. Harmful bacteria invade the teeth and gums over time, causing cavities and gum disease. She says brushing and flossing teeth decrease the amount of bacteria in the mouth and help keep the gum tissue and teeth healthy. Studies show that chewing sugar-free gum can help prevent tooth decay. She says, however, it cannot replace brushing teeth. Photo Illustration by Sekhiko Miyakawa Too ... tired ... need ... sleep! If you skip brushings those whitey hairs at night, a foul odor will overlap your mouth, leaving you with raunchy breath the next day. at least three times a week. She says using alcohol-free mouthwash is a great addition to the regular brushing routine. — Sachiko Miyakawa 10 April 2, 2009