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Who Has Stronger Teeth: Girls or Boys?

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Dentists and scientists often find it difficult to determine why some people’s teeth are affected by dental erosion and others not, despite similar drinking and eating habits. Many studies show more severe dental erosion in men than in women. Studies have been carried out on dental erosion in wine tasters and people suffering from eating disorders with vomiting. These people frequently expose their teeth to acid and therefore have a high risk of developing dental erosion. However, research shows that not all of these patients at risk have dental erosion. Researchers at the Faculty of Dentistry, University of Oslo, are now attempting to find an explanation for this.

Not just acid

How do we explain that some individuals may have no signs of dental erosion despite frequently exposing their teeth to acid, while certain individuals who seem to do everything right, still develop dental erosion? Ph.D. candidate Marte-Mari Uhlen has been taking a closer look at this in her doctoral work.

“As dentists and researchers, we are often facing cases of dental erosion that we have difficulties explaining, and we meet patients who don’t have dental erosion although their lifestyle indicates that they should. It is also a general assumption that boys tend to have more erosion and more severe erosive lesions than girls. We believe that this disparity is due to something more than just the acidic effect,” explains Uhlen.

Clinical study

Uhlen and her colleagues conducted a clinical study on 66 patients with eating disorders and vomiting. The study consisted of a clinical examination and a questionnaire-based survey in which the patients were interviewed about their illness. The questionnaire included questions about the duration of the eating disorder and frequency of vomiting as well as the participants’ general health, oral hygiene habits and eating and drinking habits.

“The results from the study showed that 70 percent of the patients had dental erosion and that those who had been ill the longest had more dental erosion and more severe lesions than the ones with a shorter duration of disease. This finding confirms our assumptions that dental erosion is a common problem in patients with eating disorders and vomiting. Nevertheless, we were surprised to find that a third of the patients had no sign of dental erosion at all, even patients who had vomited regularly for up to 32 years”, explains Uhlen.

The researchers also examined the oral environment and the tooth enamel. The oral environment includes the volume of saliva, the contents of the saliva as well as the dental pellicle, which is a protein film that covers the surface of the teeth. All these elements are important factors in protecting the teeth against acid attacks. Dental enamel consists mainly of minerals, and the formation and structure of enamel are controlled by genes.

Simulating vomiting episodes in the laboratory

In their next study, the scientists collected teeth from eight people and placed samples of enamel from these teeth on a plate in the mouth of six other volunteers.

The plates with the enamel samples were subjected to simulated vomiting episodes: The plates were removed from the mouth and washed in hydrochloric acid twice a day for a total of nine days.

“We hoped to see how the teeth would respond to being exposed to acid in a different mouth than the one they came from,” explains Uhlen. “In this way, we could examine the protecting effect of both the oral environment and of the enamel itself”

The results revealed that susceptibility to dental erosion seems to be influenced both by the quality of the dental enamel and the oral environment: While in some subjects the degree of protection by the oral environment appeared to be most important, in others, the strength or weakness of their dental enamel was more significant.

Association with enamel formation genes

Then, the attention was aimed at genetics. Could a strong or weak enamel be inheritable? The hypothesis was that the genes responsible for enamel formation may give us more information about why a person develops dental erosion or not. Results from previous studies suggest that variations in these enamel formation genes could influence the susceptibility to dental caries and dental erosion.

The researchers then collected a tooth and a saliva sample from 90 people. Samples of enamel from these teeth were then mounted on a plate and exposed to acid. The amount of enamel loss was then measured using an advanced microscope.

The scientists extracted DNA from the saliva samples to investigate whether enamel formation genes might play a role in the susceptibility to dental erosion. Seven genes were selected.

“We selected these particular genes because they are important in different phases in the formation of the enamel”, says Uhlen.

Genetic variation affects susceptibility

Comparing the amount of enamel loss and the variation in the selected genes, the scientists discovered that some gene variations involved in the formation of the enamel seem to influence the susceptibility to dental erosion. The results from the genetic analyses also indicated that enamel from female donors is more protected against dental erosion than enamel from male donors. This supported the results from the eating disorder study, namely that the enamel in girls are genetically more protected against dental erosion than the enamel in boys.

“Our findings indicate that the susceptibility to dental erosion varies from individual to individual. Factors related to both the oral environment and the quality of the enamel seem to influence the susceptibility. In addition, the susceptibility to dental erosion appears to be affected by genetic variation”, Uhlen explains.

Furthermore, the findings confirm an assumption long held by clinicians and researchers that men are more prone to dental erosion than women.

Clinical significance

The results from these studies indicate that what is generally considered a normal intake of acidic food and beverages may cause dental erosion in subjects at risk. It is important that clinicians and researchers recognize this difference in susceptibility and inform their patients.

“Recognition of the fact that some people are more vulnerable or susceptible to dental erosion as well as an awareness of males possibly being particularly susceptible, dental professionals can distribute their resources better and devote more time to the patients who need it the most,” concludes Uhlen.

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Regrowing Dental Tissue With Stem Cells From Baby Teeth

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Sometimes kids trip and fall, and their teeth take the hit. Nearly half of children suffer some injury to a tooth during childhood. When that trauma affects an immature permanent tooth, it can hinder blood supply and root development, resulting in what is essentially a “dead” tooth.

Until now, the standard of care has entailed a procedure called apexification that encourages further root development, but it does not replace the lost tissue from the injury and, even in a best-case scenario, causes root development to proceed abnormally.

New results of a clinical trial, jointly led by Songtao Shi of the University of Pennsylvania and Yan Jin, Kun Xuan, and Bei Li of the Fourth Military Medicine University in Xi’an, China, suggest that there is a more promising path for children with these types of injuries: Using stem cells extracted from the patient’s baby teeth. The work was published in the journal Science Translational Medicine.

“This treatment gives patients sensation back in their teeth. If you give them a warm or cold stimulation, they can feel it; they have living teeth again,” says Shi, professor and chair in the Department of Anatomy and Cell Biology in Penn’s School of Dental Medicine.

“So far we have follow-up data for two, two and a half, even three years and have shown it’s a safe and effective therapy.”

Shi has been working for a decade to test the possibilities of dental stem cells after discovering them in his daughter’s baby tooth. He and colleagues have learned more about how these dental stem cells, officially called human deciduous pulp stem cells (hDPSC), work and how they could be safely employed to regrow dental tissue, known as pulp.

The Phase I trial, conducted in China, which has a research track for clinical trials, enrolled 40 children who had each injured one of their permanent incisors and still had baby teeth. Thirty were assigned to hDPSC treatment and 10 to the control treatment, apexification.

Those that received hDPSC treatment had tissue extracted from a healthy baby tooth. The stem cells from this pulp were allowed to reproduce in a laboratory culture, and the resulting cells were implanted into the injured tooth.

Upon follow-up, the researchers found that patients who received hDPSCs had more signs than the control group of healthy root development and thicker dentin, the hard part of a tooth beneath the enamel. Blood flow increased as well.

At the time the patients were initially seen, all had little sensation in the tissue of their injured teeth. A year following the procedure, only those who received hDPSCs had regained some sensation. Examining a variety of immune-system components, the team found no evidence of safety concerns.

As further support of the treatment’s efficacy, the researchers had the opportunity to directly examine the tissue of a treated tooth when the patient reinjured it and had to have it extracted. They found that the implanted stem cells regenerated different components of dental pulp, including the cells that produce dentin, connective tissue, and blood vessels.

“For me the results are very exciting,” Shi says.

“To see something we discovered take a step forward to potentially become a routine therapy in the clinic is gratifying.”

It is, however, just a first step. While using a patient’s own stem cells reduces the chances of immune rejection, it’s not possible in adult patients who have lost all of their baby teeth. Shi and colleagues are beginning to test the use of allogenic stem cells, or cells donated from another person, to regenerate dental tissue in adults. They are also hoping to secure FDA approval to conduct clinical trials using hDPSCs in the United States.

Eventually, they see even broader applications of hDPSCs for treating systemic disease, such as lupus, which Shi has worked on before.

“We’re really eager to see what we can do in the dental field,” Shi says, “and then building on that to open up channels for systemic disease therapy.”

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Antibiotics Destroy ‘Good Bacteria’ And Worsen Oral Infection

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New research shows that the body’s own microbes are effective in maintaining immune cells and killing certain oral infections.

A team of Case Western Reserve University researchers found that antibiotics actually kill the “good” bacteria keeping infection and inflammation at bay.

Scientists have long known that overuse of antibiotics can do more harm than good. For example, overuse can cause antibiotic resistance. But research into this phenomenon in oral health was uncharted territory.

Pushpa Pandiyan, an assistant professor of biological sciences in the School of Dental Medicine, led a team of researchers to examine “resident” bacteria, their fatty acids and their effect on certain types of white blood cells that combat infections in the mouth.

Specifically, researchers looked at the “short-term maintenance” of Tregs and Th-17 cells in fighting fungal infections, such as Candida, in a laboratory setting.

They found that those natural defenses were very effective in reducing infection and unwanted inflammation — and antibiotics can prevent such natural defenses. Their work was recently published in Frontiers in Microbiology.

“We set out to find out what happens when you don’t have bacteria to fight a fungal infection,” Pandiyan said.

“What we found was that antibiotics can kill short-chain fatty acids produced by body’s own good bacteria.”

“We have good bacteria doing good work every day, why kill them?” Pandiyan added.

“As is the case with many infections, if you leave them alone, they will leave on their own.”

“Of course, antibiotics are still needed for life threatening infections. No question about that. Our bodies have many natural defenses that we shouldn’t meddle with,” she said.

However, needless overuse of antibiotics is not helpful, she said.

“Also, we know there is a definite link between oral health and overall health,” she added.

Pandiyan said the study could have broader implications on protective effects of “resident microbiota” in other types of infections.

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New Findings On Chronic Pain Syndrome In The Mouth

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The picture is becoming clearer regarding the chronic oral pain condition known as Burning Mouth Syndrome, or BMS, which mainly affects women who are middle-aged and older. In a dissertation at Sahlgrenska Academy, additional steps are being taken toward better diagnosis and treatment.

“Our hope is that the new findings will contribute to the development of objective diagnostic criteria and effective individualized treatment both that are currently lacking,” says Shikha Acharya, who has a PhD in oral microbiology and immunology at the Institute of Odontology.

Burning Mouth Syndrome (BMS) is a chronic pain syndrome in the oral cavity that affects approximately 4% of the Swedish population. This chronic condition mainly affects middle-aged and elderly women.

The pain is experienced as burning or stinging. The tongue is most often afflicted, but the palate, lips and gums also may be affected. Other common symptoms include dry mouth and altered taste sensation, such as a bitter or metallic taste in the mouth.

BMS is a challenge for health care providers, particularly in dental care, and a debilitating condition for many of the patients. When they estimate their problem on a visual analogue scale (VAS) where 0 is “not at all difficult” and 100 is “unbearable,” the average response is 66, the dissertation indicates. The findings came from 56 women with BMS.

In her work Shikha Acharya also connected clinical findings and self-reported reported findings from questionnaires from patients with BMS about their symptoms and background (other diseases, use of medications, etc.) along with saliva-related factors. The results have been compared with a gender- and age-matched control group.

It turns out that 45 percent of the BMS patients reported to have altered taste sensations. A total of 73 percent experienced pain that was burning or stinging or a combination of the two, but stinging and numbness also occurred.

In addition to BMS, they have a higher incidence of other types of diseases, use more medications, are more prone to grinding their teeth and report more allergies than the control group. However, more advanced analyses show that BMS was strongly associated to self-reported skin diseases and subjective oral dryness.

The fact that the BMS patients, compared with people in the control group, report that they suffer considerably more from skin diseases and skin problems is a new discovery. Similarly, that the mucin proteins in BMS patients’ saliva are altered and contain lower amounts of carbohydrate structures that affect the oral cavity’s immune system.

Analysis of inflammatory constituents in saliva shows complex relationship between BMS and background inflammation, with some of the BMS patients having higher levels of inflammation than the control group while others had lower.

The dissertation work is part of a larger project aimed at finding a model for BMS that can facilitate diagnosis and treatment in the future. The new pieces of the puzzle are helping to characterize the disease and the persistent mouth pain associated with it.

“It’s important because the afflicted patients often feel that their surroundings and health care professionals doubt their ailment,” says Shikha.

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