Are nanodiamond-encrusted teeth the future of dental implants?

UCLA researchers have discovered that diamonds on a much, much smaller scale than those used in jewelry could be used to promote bone growth and the durability of dental implants.

Nanodiamonds, which are created as byproducts of conventional mining and refining operations, are approximately four to five nanometers in diameter and are shaped like tiny soccer balls. Scientists from the UCLA School of Dentistry, the UCLA Department of Bioengineering and Northwestern University, along with collaborators at the NanoCarbon Research Institute in Japan, may have found a way to use them to improve bone growth and combat osteonecrosis, a potentially debilitating disease in which bones break down due to reduced blood flow.

When osteonecrosis affects the jaw, it can prevent people from eating and speaking; when it occurs near joints, it can restrict or preclude movement. Bone loss also occurs next to implants such as prosthetic joints or teeth, which leads to the implants becoming loose — or failing.

Implant failures necessitate additional procedures, which can be painful and expensive, and can jeopardize the function the patient had gained with an implant. These challenges are exacerbated when the disease occurs in the mouth, where there is a limited supply of local bone that can be used to secure the prosthetic tooth, a key consideration for both functional and aesthetic reasons.

The study, led by Dr. Dean Ho, professor of oral biology and medicine and co-director of the Jane and Jerry Weintraub Center for Reconstructive Biotechnology at the UCLA School of Dentistry, appears online in the peer-reviewed Journal of Dental Research.

During bone repair operations, which are typically costly and time-consuming, doctors insert a sponge through invasive surgery to locally administer proteins that promote bone growth, such as bone morphogenic protein.

Ho's team discovered that using nanodiamonds to deliver these proteins has the potential to be more effective than the conventional approaches. The study found that nanodiamonds, which are invisible to the human eye, bind rapidly to both bone morphogenetic protein and fibroblast growth factor, demonstrating that the proteins can be simultaneously delivered using one vehicle. The unique surface of the diamonds allows the proteins to be delivered more slowly, which may allow the affected area to be treated for a longer period of time. Furthermore, the nanodiamonds can be administered non-invasively, such as by an injection or an oral rinse.

"We've conducted several comprehensive studies, in both cells and animal models, looking at the safety of the nanodiamond particles," said Laura Moore, the first author of the study and an M.D.-Ph.D. student at Northwestern University under the mentorship of Dr. Ho. "Initial studies indicate that they are well tolerated, which further increases their potential in dental and bone repair applications."

"Nanodiamonds are versatile platforms," said Ho, who is also professor of bioengineering and a member of the Jonsson Comprehensive Cancer Center and the California NanoSystems Institute. "Because they are useful for delivering such a broad range of therapies, nanodiamonds have the potential to impact several other facets of oral, maxillofacial and orthopedic surgery, as well as regenerative medicine."

Ho's team previously showed that nanodiamonds in preclinical models were effective at treating multiple forms of cancer. Because osteonecrosis can be a side effect of chemotherapy, the group decided to examine whether nanodiamonds might help treat the bone loss as well. Results from the new study could open the door for this versatile material to be used to address multiple challenges in drug delivery, regenerative medicine and other fields.

"This discovery serves as a foundation for the future of nanotechnology in dentistry, orthopedics and other domains in medicine," said Dr. No-Hee Park, dean of the School of Dentistry. "Dr. Ho and his team have demonstrated the enormous potential of the nanodiamonds toward improving patient care. He is a pioneer in his field."

Bacteria responsible for gum disease facilitates development and progression of rheumatoid arthritis

Does gum disease indicate future joint problems? Although researchers and clinicians have long known about an association between two prevalent chronic inflammatory diseases - periodontal disease and rheumatoid arthritis (RA) - the microbiological mechanisms have remained unclear.

In an article published today in PLoS Pathogens, University of Louisville School of Dentistry Oral Health and Systemic Diseases group researcher Jan Potempa, PhD, DSc, and an international team of scientists from the European Union’s Gums and Joints project have uncovered how the bacterium responsible for periodontal disease, Porphyromonas gingivalis worsens RA by leading to earlier onset, faster progression and greater severity of the disease, including increased bone and cartilage destruction.

The scientists found that P. gingivalis produces a unique enzyme, peptidylarginine deiminanse (PAD) which then enhances collagen-induced arthritis (CIA), a form of arthritis similar to RA produced in the lab. PAD changes residues of certain proteins into citrulline, and the body recognizes citullinated proteins as intruders, leading to an immune attack. In RA patients, the subsequent result is chronic inflammation responsible for bone and cartilage destruction within the joints.

Potempa and his team studied another oral bacterium, Prevotella intermedia for the same affect, but learned it did not produce PAD, and did not affect CIA.

“Taken together, our results suggest that bacterial PAD may constitute the mechanistic link between P. gingivalis periodontal infection and rheumatoid arthritis, but this ground-breaking conclusion will need to be verified with further research,” he said.

Potempa said he is hopeful these findings will shed new light on the treatment and prevention of RA.

Studies indicate that compared to the general population, people with periodontal disease have an increased prevalence of RA and, periodontal disease is at least two times more prevalent in RA patients. Other research has shown that a P. gingivalis infection in the mouth will precede RA, and the bacterium is the likely culprit for onset and continuation of the autoimmune inflammatory responses that occur in the disease.

Expectant mothers' periodontal health vital to health of her baby

When a woman becomes pregnant, she knows it is important to maintain a healthy lifestyle to ensure both the health of herself and the health of her baby. New clinical recommendations from the American Academy of Periodontology (AAP) and the Eurpean Federation of Periodontology (EFP) urge pregnant women to maintain periodontal health as well. Research has indicated that women with periodontal disease may be at risk of adverse pregnancy outcomes, such giving birth to a pre-term or low-birth weight baby, reports the AAP and EFP.

Periodontal disease is a chronic, bacteria-induced, inflammatory condition that attacks the gum tissue and in more severe cases, the bone supporting the teeth. If left untreated, periodontal disease, also known as gum disease, can lead to tooth loss and has been associated with other systemic diseases, such as diabetes and cardiovascular disease.

"Tenderness, redness, or swollen gums are a few indications of periodontonal disease," warns Dr. Nancy L. Newhouse, DDS, MS, President of the AAP and a practicing periodontist in Independence, Missouri. "Other symptoms include gums that bleed with toothbrushing or eating, gums that are pulling away from the teeth, bad breath, and loose teeth. These signs, especially during pregnancy, should not be ignored and may require treatment from a dental professional."

Several research studies have suggested that women with periodontal disease may be more likely to deliver babies prematurely or with low-birth weight than mothers with healthy gums. According to the Center for Disease Control and Prevention (CDC), babies with a birth weight of less than 5.5 pounds may be at risk of long-term health problems such as delayed motor skills, social growth, or learning disabilities. Similar complications are true for babies born at least three weeks earlier than its due date. Other issues associated with pre-term birth include respiratory problems, vision and hearing loss, or feeding and digestive problems.

The medical and dental communities concur that maintaining periodontal health is an important part of a healthy pregnancy. The clinical recommendations released by the AAP and the EFP state that non-surgical periodontal therapy is safe for pregnant women, and can result in improved periodontal health. Published concurrently in the Journal of Periodontology and Journal of Clinical Periodontology, the report provides guidelines for both dental and medical professionals to use in diagnosing and treating periodontal disease in pregnant women. In addition, the American College of Obstetricians and Gynecologists recently released a statement encouraging pregnant women to sustain their oral health and recommended regular dental cleanings during pregnancy.

"Routine brushing and flossing, and seeing a periodontist, dentist, or dental hygienist for a comprehensive periodontal evaluation during pregnancy may decrease the chance of adverse pregnancy complications," says Dr. Newhouse. "It is important for expectant mothers to monitor their periodontal health and to have a conversation with their periodontist or dentist about the most appropriate care. By maintaining your periodontal health, you are not only supporting your overall health, but also helping to ensure a safe pregnancy and a healthy baby," says Dr. Newhouse.

Poor oral health linked to cancer-causing oral HPV infection

Poor oral health, including gum disease and dental problems, was found to be associated with oral human papillomavirus (HPV) infection, which causes about 40 percent to 80 percent of oropharyngeal cancers, according to a study published in Cancer Prevention Research, a journal of the American Association for Cancer Research.

"Poor oral health is a new independent risk factor for oral HPV infection and, to our knowledge, this is the first study to examine this association," said Thanh Cong Bui, Dr.P.H., postdoctoral research fellow in the School of Public Health at the University of Texas Health Sciences Center in Houston. "The good news is, this risk factor is modifiable — by maintaining good oral hygiene and good oral health, one can prevent HPV infection and subsequent HPV-related cancers."

The researchers found that among the study participants, those who reported poor oral health had a 56 percent higher prevalence of oral HPV infection, and those who had gum disease and dental problems had a 51 percent and 28 percent higher prevalence of oral HPV infection, respectively. In addition, the researchers were able to associate oral HPV infections with number of teeth lost.

Similar to genital HPV infection, oral HPV infection can be of two kinds: infection with low-risk HPV types that do not cause cancer, but can cause a variety of benign tumors or warts in the oral cavity, and infection with high-risk HPV types that can cause oropharyngeal cancers.

Bui, Christine Markham, Ph.D., and colleagues used data from the 2009-2010 National Health and Nutrition Examination Survey (NHANES) conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention. This survey consisted of a nationally representative sample of about 5,000 people recruited each year, located in counties across the United States.

The researchers identified 3,439 participants aged 30 to 69 years from NHANES, for whom data on oral health and the presence or absence of 19 low-risk HPV types and 18 high-risk HPV types in the oral cavity were available. Oral health data included four measures of oral health: self-rating of overall oral health, presence of gum disease, use of mouthwash to treat dental problems within past seven days of the survey, and number of teeth lost. They examined data on age, gender, marital status, marijuana use, cigarette smoking, and oral sex habits, among others, which influence HPV infection.

The researchers found that being male, smoking cigarettes, using marijuana, and oral sex habits increased the likelihood of oral HPV infection. They also found that self-rated overall oral health was an independent risk factor for oral HPV infection, because this association did not change regardless of whether or not the participants smoked or had multiple oral sex partners.

Because HPV needs wounds in the mouth to enter and infect the oral cavity, poor oral health, which may include ulcers, mucosal disruption, or chronic inflammation, may create an entry portal for HPV, said Bui. There is, however, currently not enough evidence to support this, and further research is needed to understand this relationship, he said.

"Although more research is needed to confirm the causal relationship between oral health and oral HPV infection, people may want to maintain good oral health for a variety of health benefits," said Bui. "Oral hygiene is fundamental for oral health, so good oral hygiene practices should become a personal habit."

A Glass of Milk After Eating Sugary Cereals May Prevent Cavities

Washing down sugary breakfast cereal with milk after eating reduces plaque acid levels and may prevent damage to tooth enamel that leads to cavities, according to new research at the University of Illinois at Chicago College of Dentistry.

Dry ready-to-eat, sugar-added cereals combine refined sugar and starch. When those carbohydrates are consumed, bacteria in the dental plaque on tooth surfaces produce acids, says Christine Wu, professor of pediatric dentistry and director of cariology, who served as principal investigator of the study.

The research is published in the July issue of the Journal of the American Dental Association.

Reports have shown that eating carbohydrates four times daily, or in quantities greater than 60 grams per person per day, increases the risk of cavities.

The new study, performed by Wu's former graduate student Shilpa Naval, involved 20 adults eating 20 grams of dry Froot Loops cereal, then drinking different beverages -- whole milk, 100 percent apple juice, or tap water.

Plaque pH, or acidity, was measured with a touch microelectrode between the premolar teeth before eating; at two and five minutes after eating; and then two to 30 minutes after drinking a liquid.

The pH in plaque dropped rapidly after consuming cereal alone, and remained acidic at pH 5.83 at 30 minutes. A pH below 7 is acidic; a pH greater than 7 is basic. Pure water has a pH close to 7.

Participants who drank milk after eating sugary cereal showed the highest pH rise, from 5.75 to 6.48 at 30 minutes. Those who drank apple juice remained at pH 5.84 at 30 minutes, while water raised the pH to 6.02.

Fruit juices are considered healthy food choices, but the added sugar can be a risk to dental health, Wu said.

"Our study results show that only milk was able to reduce acidity of dental plaque resulting from consuming sugary Froot Loops," said Naval, who is currently a fellow at the Centers for Disease Control and Prevention in Atlanta. "We believe that milk helped mitigate the damaging effect of fermentable carbohydrate and overcome the previously lowered plaque pH."

Milk, with a pH ranging from 6.4 to 6.7, is considered to be a functional food that fights cavities because it promotes tooth remineralization and inhibits the growth of plaque, Wu said.

Wu says most consumers think that since milk is considered to be cavity-fighting, acid production by plaque bacteria can be minimized by mixing it with cereal. However, in an unpublished study in her lab, it was discovered that the combination of Froot Loops and milk became syrupy. Eating cereal combined with milk lowered plaque pH to levels similar to that obtained after rinsing with a 10 percent sugar solution.

Eating sugar-added cereal with milk, followed by drinking fruit juice is thus a highly cavity-causing combination, Wu said.

Diet plays an important role in oral health, Wu said. Studies of food intake and cavities have focused mainly on the sugar, or carbohydrate, content. Fewer studies have looked at how combinations of food, and the order in which they are eaten, may help fight cavities.

"Results from a previous study suggested that the last food item consumed exerts the greatest influence on subsequent plaque pH," she said. For example, eating cheese after a sugary meal reduces acid production, and consumers can modify their diet in such a way as to prevent the cavity-causing effects of sugary foods."

"If understood and implemented properly, food sequencing can be used as a public health educational tool to maintain and preserve good oral health," said Naval.

Bacterium that causes gum disease packs a 1-2 punch to the jaw

The newly discovered bacterium that causes gum disease delivers a one-two punch by also triggering normally protective proteins in the mouth to actually destroy more bone, a University of Michigan study found.

Scientists and oral health care providers have known for decades that bacteria are responsible for periodontitis, or gum disease. Until now, however, they hadn't identified the bacterium.

"Identifying the mechanism that is responsible for periodontitis is a major discovery," said Yizu Jiao, a postdoctoral fellow at the U-M Health System, and lead author of the study appearing in the recent issue of the journal Cell Host and Microbe.

Jiao and Noahiro Inohara, research associate professor at the U-M Health System, worked with William Giannobile, professor of dentistry, and Julie Marchesan, formerly of Giannobile's lab.

The study yielded yet another significant finding: the bacterium that causes gum disease, called NI1060, also triggers a normally protective protein in the oral cavity, called Nod1, to turn traitorous and actually trigger bone-destroying cells. Under normal circumstances, Nod1 fights harmful bacterium in the body.

"Nod1 is a part of our protective mechanisms against bacterial infection. It helps us to fight infection by recruiting neutrophils, blood cells that act as bacterial killers," Inohara said. "It also removes harmful bacteria during infection. However, in the case of periodontitis, accumulation of NI1060 stimulates Nod1 to trigger neutrophils and osteoclasts, which are cells that destroy bone in the oral cavity."

Giannobile, who also chairs the Department of Periodontics and Oral Medicine at the U-M School of Dentistry, said understanding what causes gum disease at the molecular level could help develop personalized therapy for dental patients.

"The findings from this study underscore the connection between beneficial and harmful bacteria that normally reside in the oral cavity, how a harmful bacterium causes the disease, and how an at-risk patient might respond to such bacteria," Giannobile said.

Consuming cheese may help protect teeth against cavities

Consuming dairy products is vital to maintaining good overall health, and it's especially important to bone health. But there has been little research about how dairy products affect oral health in particular. However, according to a new study published in the May/June 2013 issue of General Dentistry, the peer-reviewed clinical journal of the Academy of General Dentistry (AGD), consuming cheese may help protect teeth against cavities.

The study sampled 68 subjects ranging in age from 12 to 15, and the authors looked at the dental plaque pH in the subjects' mouths before and after they consumed cheese, milk, or sugar-free yogurt. A pH level lower than 5.5 puts a person at risk for tooth erosion, which is a process that wears away the enamel (or protective outside layer) of teeth. "The higher the pH level is above 5.5, the lower the chance of developing cavities," explains Vipul Yadav, MDS, lead author of the study.

The subjects were assigned into groups randomly. Researchers instructed the first group to eat cheddar cheese, the second group to drink milk, and the third group to eat sugar-free yogurt. Each group consumed their product for three minutes and then swished with water. Researchers measured the pH level of each subject's mouth at 10, 20, and 30 minutes after consumption.

The groups who consumed milk and sugar-free yogurt experienced no changes in the pH levels in their mouths. Subjects who ate cheese, however, showed a rapid increase in pH levels at each time interval, suggesting that cheese has anti-cavity properties.

The study indicated that the rising pH levels from eating cheese may have occurred due to increased saliva production (the mouth's natural way to maintain a baseline acidity level), which could be caused by the action of chewing. Additionally, various compounds found in cheese may adhere to tooth enamel and help further protect teeth from acid.

"It looks like dairy does the mouth good," says AGD spokesperson Seung-Hee Rhee, DDS, FAGD. "Not only are dairy products a healthy alternative to carb- or sugar-filled snacks, they also may be considered as a preventive measure against cavities."