Intelligence in Toothbrushing

Elizabeth Monk
September 01, 2002
woman brushes teeth in mirror
James Collins

Brushing your teeth is simple ... or is it? The mind may play tricks on the body, making brushing more complex - and more difficult - than you think.

The careful scraping of fine metal against tooth enamel is familiar to anyone who visits the dentist. No matter how well you think you have brushed, your dental hygienist will always scrape plaque off areas you have missed. Plaque, the white gunk that collects on the surface of the tooth and gum line, is a combination of bacteria, saliva and food, Marti Sawyer tells me.

"Have you ever had a periodontal probing?" asks Sawyer, a full-time dental hygienist and part-time student at Penn State. She proceeds to roughly sketch a tooth, the surrounding bone, and the encompassing gum tissue. She points to the space where the gum surrounds the tooth—the gingiva—and lightly scribbles over it. "Plaque accumulates here and bacteria destroys parts of the gum," she explains. A small probe—marked in millimeters—is placed under the gum line to record how much has deteriorated. The procedure sounds intimidating but Sawyer insists "it almost hurts but doesn't." A normal probe reading is 2 to 3 millimeters. If a patient has higher probe readings, they are at risk for periodontal disease. The bacteria in the built-up plaque will destroy the bone and surrounding support structures of the teeth. Gingivitis is the first stage and the mildest form of the disease. Good brushing techniques can reverse the bacteria's progress. However, if gingivitis goes untreated, bone loss may progress—and—in the worst case possible, may call for the removal of the infected teeth.

Sawyer started to notice a pattern where plaque accumulated in her patients' teeth. "I've been working in the same dental office for 13, going on 14 years, and I discovered a certain segment of my patients had normal probe readings except in two distinct places": the outside of the upper left molars and the inside of the lower right molars. Sawyer was puzzled as to why these two specific areas of the mouth would have readings of 4 or more millimeters. "No matter how I went over brushing, the pocket readings continued to be high—and I am very specific about giving directions. Tooth brushing is not a generic craft," laughs Sawyer.

So she watched herself brush, and then watched her husband and daughter brush. Sawyer noticed that when people brush their teeth, they do not move their hand across their midline. The midline is where the body divides into vertical halves. If you are right handed, the toothbrush needs to be slightly left of the body's center to fully clean your lower right and upper left back molars. If your toothbrush doesn't cross the midline of your body, then it is difficult for the bristles to reach the areas effectively.

"Strange, isn't it?" says Sawyer, "The body knows it wants to clean those back teeth. Why won't it do it naturally?"

Sawyer believes the body has an inner intelligence that keeps the arms from crossing the midline; a self-established boundary. She equates her idea of body intelligence with intuition or instinct. "It's like when somebody you don't like comes too close, and your body tenses up without conscious thought," she explains.

To explore her theory, Sawyer videotaped 17 of her patients—all of whom had pockets in problem areas—through a two-way mirror to observe their brushing techniques. She found that only three of her subjects (all of whom were right-handed) crossed their midlines to get to their lower right molars. Others compensated by turning and tilting their heads, which may not allow for as thorough a cleaning. Sawyer acknowledges that other factors play into why it is difficult to brush those two specific areas—shape of the mouth, tongue size, width of the arch, time spent brushing —but the fact remains: the arm does not want to cross the midline. "Especially if you're brushing on auto-pilot," emphasizes Sawyer.

Sawyer acknowledges that hers is a preliminary study. The main goal of her undergraduate thesis is to raise awareness about the body movements involved in brushing. "I know I'm just hitting on one aspect of tooth brushing. Many people think tooth brushing is a simple craft, but it's incredibly complex," says Sawyer. "When we teach people to brush we never instruct patients about their hands, it's always been just about putting the bristles along the gum." She hopes if more attention is given to hand position, patients will be more likely to brush the areas where plaque builds up, thus preventing periodontal problems.

Marti Sawyer is a part-time honors student majoring in workforce education and development. Her adviser is Richard Walter, Ph.D., associate professor of education in the College of Education, 315 Keller Bldg., University Park, PA 16802; 814-865-2133;

Last Updated September 01, 2002