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How does tooth enamel last a lifetime?

If we cut our skin or break a bone, these tissues will repair themselves; our bodies are excellent at recovering from injury.

Tooth enamel, however, cannot regenerate, and the oral cavity is a hostile environment.

Every mealtime, enamel is put under incredible stress; it also weathers extreme changes in both pH and temperature.

Despite this adversity, the tooth enamel that we develop as a child remains with us throughout our days.

Researchers have long been interested in how enamel manages to stay functional and intact for a lifetime.

As one of the authors of the latest study, Prof. Pupa Gilbert from the University of Wisconsin–Madison puts it, «How does it prevent catastrophic failure?»

The secrets of enamel

With assistance from researchers at the Massachusetts Institute of Technology (MIT) in Cambridge and the University of Pittsburgh, PA, Prof. Gilbert took a detailed look at the structure of enamel.

The team of scientists has now published the results of its study in the journal Nature Communications.

Enamel is made up of so-called enamel rods, which consist of hydroxyapatite crystals. These long, thin enamel rods are around 50 nanometers wide and 10 micrometers long.

By using cutting edge imaging technology, the scientists could visualize how individual crystals in tooth enamel are aligned. The technique, which Prof. Gilbert designed, is called polarization-dependent imaging contrast (PIC) mapping.

Before the advent of PIC mapping, it was impossible to study enamel with this level of detail. «[Y]ou can measure and visualize, in color, the orientation of individual nanocrystals and see many millions of them at once,» explains Prof. Gilbert.

The architecture of complex biominerals, such as enamel, becomes immediately visible to the naked eye in a PIC map.

When they viewed the structure of enamel, the researchers uncovered patterns. «By and large, we saw that there was not a single orientation in each rod, but a gradual change in crystal orientations between adjacent nanocrystals,» explains Gilbert. «And then the question was, ‘Is this a useful observation?'»

The importance of crystal orientation

To test whether the change in crystal alignment influences the way that enamel responds to stress, the team recruited help from Prof. Markus Buehler of MIT. Using a computer model, they simulated the forces that hydroxyapatite crystals would experience when a person chews.

Within the model, they placed two blocks of crystals next to each other so that the blocks touched along one edge. The crystals within each of the two blocks were aligned, but where they came in contact with the other block, the crystals met at an angle.

To investigate, co-author Cayla Stifler returned to the original PIC mapping information and measured the angles between adjacent crystals. After generating millions of data points, Stifler found that 1 degree was the most common size of misorientation, and the maximum was 30 degrees.

This observation agreed with the simulation — smaller angles seem better able to deflect cracks.

Now we know that cracks are deflected at the nanoscale and, thus, can’t propagate very far. That’s the reason our teeth can last a lifetime without being replaced.

Prof. Pupa Gilbert

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How to get rid of a toothache at night

However, there are a number of remedies that may help people find relief and get to sleep, including taking pain relievers or applying a cold compress or even cloves to the tooth.

In this article, learn more about nine home remedies for relieving a toothache at night.

6 ways to treat a toothache at night

Treating a toothache at night may be more difficult, as there is not much to distract a person from the pain.

However, people can try the following methods to relieve pain:

1. Oral pain medication

Taking over-the-counter (OTC) pain medications such as acetaminophen (Tylenol) or ibuprofen (Advil) is a quick, simple way for many people to effectively reduce mild-to-moderate toothaches.

Always stay within the recommended dosage on the packaging.

If the toothache is severe, it is best to see a dentist and speak to them about stronger pain relievers.

2. Cold compress

Using a cold compress may help ease the pain of a toothache.

Applying a bag of ice wrapped in a towel to the affected side of the face or jaw helps constrict the blood vessels in the area, which can reduce pain to allow a person to fall asleep.

Applying a cold compress to the area for 15–20 minutes every few hours in the evening may also help prevent pain when going to bed.

3. Elevation

Pooling blood in the head may cause additional pain and inflammation. For some people, elevating the head with an extra pillow or two may relieve the pain enough for them to fall asleep.

4. Medicated ointments

Some medicated ointments may also help reduce toothache pain. OTC numbing gels and ointments that contain ingredients such as benzocaine may numb the area.

However, benzocaine is not suitable for use by young children.

5. Salt water rinse

A simple salt water rinse is a common home remedy for a toothache.

Salt water is a natural antibacterial agent, so it may reduce inflammation. This, in turn, helps protect damaged teeth from infection.

Rinsing with salt water may also help remove any food particles or debris stuck in the teeth or gums.

6. Hydrogen peroxide rinse

Periodontitis is a serious gum infection that generally occurs as a result of poor oral hygiene. It can cause issues such as soreness, bleeding gums, and teeth that come loose in their sockets.

The author of a 2016 study found that rinsing with hydrogen peroxide mouthwash helped reduce plaque and symptoms of periodontitis.

People should always dilute food-grade hydrogen peroxide with equal parts water. Swish the solution in the mouth, but do not swallow it.

This remedy is not suitable for children, as there is a risk they may accidentally swallow the mixture.

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Brushing your teeth may keep your heart healthy

The bacteria in our mouths may hold the key to many facets of our health.

Researchers have found intriguing clues about pancreatic and esophageal cancer risk in mouth bacteria, and some studies have linked poor oral hygiene with respiratory problems.

Mounting evidence is also strengthening the link between oral health and cardiovascular health.

For instance, some studies have found oral bacteria in the blood clots of people receiving emergency treatment for stroke, and experts have linked severe gum disease with a significantly higher risk of hypertension.

Conversely, destroying «friendly» oral bacteria that help maintain a healthy and balanced oral microbiome could disrupt blood pressure levels and also lead to hypertension.

Maintaining good oral health, therefore, seems to be key to cardiovascular health.

Now, a new study that appears in the European Journal of Preventive Cardiology suggests that regular toothbrushing may keep heart failure and atrial fibrillation (A-fib) — a type of arrhythmia — at bay.

Dr. Tae-Jin Song of Ewha Womans University in Seoul, Korea, is the senior author of the new study.

In their paper, Dr. Song and team explain that the motivation for the study hinges on the mediating role of inflammation. They write, «Poor oral hygiene can provoke transient bacteremia and systemic inflammation, a mediator of atrial fibrillation and heart failure.»

Studying A-fib, heart failure, and oral hygiene

In their study, Dr. Song and team examined atrial fibrillation’s associations with both heart failure and poor oral hygiene. They used data from 161,286 people who were part of the Korean National Health Insurance System-Health Screening Cohort.

A-fib is a condition affecting at least 2.7 million people in the United States. In people with A-fib, the heart cannot efficiently pump blood to the rest of the body because it does not beat regularly.

The heart also does not pump blood as it should in people with heart failure. This inefficiency results in fatigue and, sometimes, breathing difficulties, as insufficient oxygen reaches the other organs in the body.

The participants of the current study were 40–79 years old and had no history of either A-fib or heart failure. During enrollment, which took place between 2003 and 2004, the team measured the height and weight of each of the participants and asked them questions about their lifestyle, oral health, and oral hygiene habits.

The participants also underwent some laboratory tests, which included blood tests, urine tests, and blood pressure readings.

Brushing lowers heart failure risk by 12%

Over a median follow-up period of 10.5 years, 4,911 participants received a diagnosis of A-fib, and 7,971 developed heart failure.

Brushing the teeth three times or more a day was linked with a 10% lower chance of developing A-fib and a 12% lower risk of heart failure.

Confounding factors — including age, sex, socioeconomic status, physical activity, alcohol intake, body mass index, and other coexisting conditions, such as hypertension — did not influence these results, as the researchers accounted for them in their analysis.

The authors conclude:

Improved oral hygiene care was associated with decreased risk of atrial fibrillation and heart failure. Healthier oral hygiene by frequent toothbrushing and professional dental cleanings may reduce risk of atrial fibrillation and heart failure.

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