Build a better toothbrush: Aural feedback for oral hygiene

Researchers in Japan have discovered that how effectively we clean our teeth and how satisfied we are with the brushing job we do depends a lot on the sound of the bristles scrubbing against the enamel. In trials with volunteer teeth cleaners, the team has used a tiny microphone in a modified toothbrush to 'sample' the sound being made in the mouth during brushing and to modulate it and then feed that sound back to the volunteer via headphones to see what effect it would have on cleaning efficacy and satisfaction. They describe details in the International Journal of Arts and Technology.

Taku Hachisu and Hiroyuki Kajimoto of The University of Electro-Communications, in Chofu, Japan explain how modulating the brush sound affects brushing efficacy and satisfaction. The team found that if they manipulated the pitch, or frequency and loudness, of the brushing sound they could alter the volunteers' perception of comfort and accomplishment. They also showed that if they gradually increased the frequency as teeth cleaning progressed, the volunteers felt like the process was more comfortable and that their teeth were cleaner at the end of the process.

"Tooth brushing provides a 'negative reward' for users as they brush their teeth to avoid developing caries," the team explains. Many people find the task boring. "Subsequently, users do not consider the impact of omitting the action until suffering from caries or other dental diseases," the team adds. Their results show that it is possible to motivate users by interactively manipulating the frequency of brushing sounds, so that the task becomes more satisfying. Importantly, the system can tell, through a built-in force sensor, whether a person is brushing too hard, which can damage the gum line, and so give them aural feedback to encourage them to clean their teeth more gently.

The prototype system requires the teeth cleaner to wear headphones, which is impractical in real life. However, there are bone conduction speaker systems that might be incorporated into the smart toothbrush so that the amplified feedback loop is created in one's mouth. The team will next recruit volunteers to test the system in their comfort of their own bathrooms.

'No-drill' dentistry stops tooth decay

 

The white patches are signs of early decay that can be stopped and reversed before they become cavities (brown patch on tooth on the right).

Credit: University of Sydney

 

A University of Sydney study has revealed that tooth decay (dental caries) can be stopped, reversed, and prevented without the need for the traditional 'fill and drill' approach that has dominated dental care for decades.

The results of the seven year study, published today in Community Dentistry and Oral Epidemiology, found that the need for fillings was reduced by 30 to 50 per cent through preventative oral care.

"It's unnecessary for patients to have fillings because they're not required in many cases of dental decay," said the study's lead author, Associate Professor Wendell Evans of the University of Sydney.
"This research signals the need for a major shift in the way tooth decay is managed by dentists -- dental practice in Australia needs to change. Our study shows that a preventative approach has major benefits compared to current practice.

"For a long time it was believed that tooth decay was a rapidly progressive phenomenon and the best way to manage it was to identify early decay and remove it immediately in order to prevent a tooth surface from breaking up into cavities. After removing the decay, the affected tooth is then restored with a filling material -- this process is sometimes referred to as 'drilling and filling'.

"However, 50 years of research studies have shown that decay is not always progressive and develops more slowly than was previously believed. For example, it takes an average of four to eight years for decay to progress from the tooth's outer layer (enamel) to the inner layer (dentine).

"That is plenty of time for the decay to be detected and treated before it becomes a cavity and requires a filling."

Professor Wendell Evans and his team developed the Caries Management System (CMS) -- a set of protocols which cover the assessment of decay risk, the interpretation of dental X-rays, and specific treatment of early decay (decay that is not yet a cavity).

The CMS treatment 'no-drill' involves four aspects:
1. Application of high concentration fluoride varnish by dentists to the sites of early decay
2. Attention to home tooth brushing skills
3. Restriction of between-meal snacks and beverages containing added sugar
4. Risk-specific monitoring.M/ul>
"The CMS was first tested on high risk patients at Westmead Hospital with great success," said Professor Evans.
"It showed that early decay could be stopped and reversed and that the need for drilling and filling was reduced dramatically.
"A tooth should be only be drilled and filled where an actual hole-in-the-tooth (cavity) is already evident," he said.
The CMS treatment was then tested in general dental practices in New South Wales and Australian Capital Territory. The Monitor Practice Program (MPP), funded by the National Health and Medical Research Council of Australia (NHMRC), confirmed that after seven years, decay risk was substantially reduced among the CMS patients and their need for fillings was reduced by 30 to 50 per cent compared to the control group.
"The reduced decay risk and reduced need for fillings was understandably welcomed by patients," Professor Evans said. "However, patients play an important role in their treatment. This treatment will need a partnership between dentists and patients to be most successful."

Graphene oxide could make stronger dental fillings

Graphene oxide could be used to make super strong dental fillings that don't corrode, according to a new study published in Colloids and Surfaces B: Biointerfaces.

Research suggests we chew around 800 times in an average meal; that's almost a million times a year. We put our teeth under huge strain, and often require fillings to repair them. Fillings are typically made of a mixture of metals, such as copper, mercury, silver and tin, or composites of powdered glass and ceramic.

Typical metal fillings can corrode and composite fillings are not very strong; Graphene on the other hand is 200 times stronger than steel and doesn't corrode, making it a prime new candidate for dental fillings.

In the study, researchers from Iuliu Hatieganu University of Medicine and Pharmacy, the National Institute for Research and Development of Isotopic and Molecular Technologies, and the University of Agricultural Sciences and Veterinary Medicine in Romania, and Ross University School of Veterinary Medicine Basseterre in the West Indies investigated whether different forms of graphene are toxic to teeth.

"The idea of the project was to add graphene into dental materials, in order to increase their resistance to corrosion as well as to improve their mechanical properties," explained Dr. Stela Pruneanu, one of the authors of the study from the National Institute for Research and Development of Isotopic and Molecular Technologies in Romania. "There is contradictory information regarding the cytotoxicity of graphene, so we first wanted to determine how toxic it is for teeth."

Graphene comes in different forms, including graphene oxide, nitrogen-doped graphene and thermally reduced graphene oxide. The researchers tested how toxic these different types of graphene are in vitro for stem cells found in teeth.

Thermally reduced graphene oxide was highly toxic, making it inappropriate as a dental filling material. Nitrogen-doped graphene caused membrane damage at high doses (20 and 40 micrograms per milliliter). However, it was shown to have antioxidant properties, so it could be useful if covered in a protective layer. Graphene oxide was least toxic to cells, making it an ideal candidate.

"The results were very interesting and proved that graphene is appropriate for use in dental materials," said Dr. Gabriela Adriana Filip, one of the authors of the study and Associate Professor at Iuliu Hatieganu University of Medicine and Pharmacy Cluj-Napoca in Romania. "We believe that this research will bring new knowledge about the cytotoxic properties of graphene-based materials and their potential applications in dental materials."


The next step for this research is for the team to make dental materials with graphene oxide and test how compatible they are with teeth, and how toxic they are to cells. The results are due to be published soon.

Cognitive behavior therapy can help overcome fear of the dentist

Cognitive behavioural therapy could help many people with a dental phobia overcome their fear of visiting the dentist and enable them to receive dental treatment without the need to be sedated, according to a new study by King's College London.

Anxiety about visiting the dentist is common and becomes a phobia when it has a marked impact on someone's well-being; people with dental phobias typically avoid going to the dentist and end up experiencing more dental pain, poorer oral health and a detrimental effect on their quality of life. Estimates from the most recent Adult Dental Health Survey in the UK suggest around one in ten people suffers from dental phobia.

Cognitive behavioural therapy (CBT) is a short-term therapy, typically lasting 6-10 sessions. CBT has been shown to help with a range of psychological problems, most notably for depression and anxiety-related disorders. Both cognitive and behavioural interventions have been shown to be successful in reducing dental anxiety and increasing dental attendance.

The latest study, published in the British Dental Journal, looked at the characteristics of 130 patients (99 women and 31 men) attending a psychologist-led CBT service and the outcomes of their treatment. Patients attending a clinic run by the King's College London Dental Institute Health Psychology Service at Guy's and St Thomas' NHS Foundation Trust were surveyed for their levels of dental anxiety, general anxiety, depression, suicidal thoughts, alcohol use and oral health-related quality of life.

Three-quarters of those assessed scored 19 or higher on the Modified Dental Anxiety Scale (MDAS), indicating dental phobia. The remainder all scored high on one or more items of the MDAS, suggesting a specific fear of some aspect of dentistry. Fear of dental injections and the dental drill were the most common high scoring items on the MDAS. Nearly all patients (94%) reported a knock-on effect from problems with their teeth, mouth or gums on their daily living and quality of life.

A proportion of the patients surveyed were found to have other psychological conditions - 37% had high levels of general anxiety and 12% had clinically significant levels of depression. Suicidal thoughts were reported by 12% of patients and four (3%) reported a recent intent to commit suicide. Individuals were referred to support services via the care of their GP and for suicide risk, immediate action was taken based on local service guidelines.

Of all patients referred, four-fifths (79%) went on to have dental treatment without the need for sedation and 6% had their dental treatment under sedation. The average number of CBT appointments required before a patient received dental treatment without sedation was five.

Professor Tim Newton from the Dental Institute at King's College London and lead author of the study said: "People with dental phobia are most commonly given sedation to allow them to become relaxed enough for a short period of time to have their dental treatment performed. However this does not help them to overcome their fear in the long term. The primary goal of our CBT service is to enable patients to receive dental treatment without the need for sedation, by working with each individual patient to set goals according to their priorities. Our study shows that after on average five CBT sessions, most people can go on to be treated by the dentist without the need to be sedated."

"However, there is a need for people with dental phobia to be carefully assessed by trained CBT practitioners working with dental health professionals. Some of the patients referred to us were found to be experiencing additional psychological difficulties, and needed further referral and management. CBT provides a way of reducing the need for sedation in people with a phobia, but there will still be those who need sedation because they require urgent dental treatment or they are having particularly invasive treatments. Our service should be viewed as complementing sedation services rather than as an alternative, the two together providing a comprehensive care pathway for the ultimate benefit of patients."

A recent study published in the same journal, co-authored by Professor Tim Newton, showed that more women than men reported dental phobia in the 2009 Adult Dental Health Survey. Those with dental phobia were more likely to come from a lower income background, have more caries in their teeth and suffer from poorer oral health overall

Details from the inner life of a tooth

Both in materials science and in biomedical research it is important to be able to view minute nanostructures, for example in carbon-fiber materials and bones. A team from the Technical University of Munich (TUM), the University of Lund, Charite hospital in Berlin and the Paul Scherrer Institute (PSI) have now developed a new computed tomography method based on the scattering, rather than on the absorption, of X-rays. The technique makes it possible for the first time to visualize nanostructures in objects measuring just a few millimeters, allowing the researchers to view the precise three-dimensional structure of collagen fibers in a piece of human tooth.

In principle, X-ray computed tomography (CT) has been around since the 1960s: X-ray images are taken of an object from various directions, and a computer then uses the individual images to generate a three-dimensional image of the object. Contrast is produced by the differential absorption of X-rays in dissimilar materials. However, the new method, which was developed by Franz Pfeiffer, professor for Biomedical Physics at TUM and his team utilizes the scattering of X-rays rather than their absorption. The results have now been published in the journal Nature.
Scattering provides detailed images of nanostructures
Theoretically, X-rays act like light with a very short wavelength. This principle lies at the heart of the new method: When a light is shone on a structured object, for example a CD, the reflected light produces a characteristic rainbow pattern. Although the fine grooves in the CD cannot be seen directly, the diffraction of the light rays -- known as scattering -- indirectly reveals the structure of the object.
The same effect can be observed with X-rays, and it is this phenomenon that the researchers take advantage of in their new technique. The advantage of X-rays over visible light is that they are able to penetrate into materials, thus providing detailed information about the internal structure of objects. The researchers have now combined this three-dimensional information from scattered X-rays with computed tomography (CT).
Conventional CT methods calculate exactly one value, known as a voxel, for each three-dimensional image point within an object. The new technique assigns multiple values to each voxel, as the scattered light arrives from various directions. "Thanks to this additional information, we're able to learn a great deal more about the nanostructure of an object than with conventional CT methods. By indirectly measuring scattered X-rays, we can now visualize minute structures that are too small for direct spatial resolution," Franz Pfeiffer explains.
Internal view of a tooth
For demonstration purposes the scientists examined a piece of human tooth measuring around three millimeters. A large part of a human tooth is made from the substance dentin. It consists largely of mineralized collagen fibers whose structure is largely responsible for the mechanical properties of the tooth. The scientists have now visualized these tiny fiber networks.
A total of 1.4 million scatter images were taken, with the scattered light arriving from various directions. The individual images were then processed using a specially devised algorithm that builds up a complete reconstruction of the three-dimensional distribution of the scattered rays step by step. "Our algorithm calculates the precise direction of the scatter information for each image and then forms groups having the same scatter direction. This allows internal structures to be precisely reconstructed," says Martin Bech, former postdoc at the TUM and now assistant professor at the University of Lund.
Using this method, it was possible to clearly view the three-dimensional orientation of the collagen fibers within a sample of this size for the first time. The results are in agreement with knowledge previously obtained about the structures from thin sections. "A sophisticated CT method is still more suitable for examining large objects. However, our new method makes it possible to visualize structures in the nanometer range in millimeter-sized objects at this level of precision for the first time," says Florian Schaff, lead author of the paper.

Journal Reference:

1. Florian Schaff, Martin Bech, Paul Zaslansky, Christoph Jud, Marianne Liebi, Manuel Guizar-Sicairos, Franz Pfeiffer. Six-dimensional real and reciprocal space small-angle X-ray scattering tomography. Nature, 2015; 527 (7578): 353 DOI: 10.1038/nature16060

How to eliminate pain tied to tooth decay

This is a scanning electron microscope image of newly grown enamel using amelogenin-chitosan hydrogel.

CREDIT

Herman Ostrow School of Dentistry of USC

Dual discoveries at USC propose a promising method to regrow nonliving hard tissue, lessening or even eliminating pain associated with tooth decay, which the National Institutes of Health calls the most prevalent chronic disease.

Janet Moradian-Oldak, a professor at the Herman Ostrow School of Dentistry of USC, has investigated methods to regrow tooth enamel for the past two decades. The process is especially tricky because unlike bone, mature enamel cannot rejuvenate. Tooth enamel is a nonliving tissue.

The a-ha moment came Oct. 22 when, in collaboration with lead author Sauma Prajapati of USC and other colleagues, she published a study in the Biomaterials journal saying matrix metalloproteinase-20, an enzyme found only in teeth, chops up amelogenin proteins, which facilitate organized enamel crystal formation. MMP-20 clears the way for hard material to usurp vacated space.

Her team is the first to define the function of an enzyme for preventing protein occlusion inside a crystal, she said.

"MMP-20 is released at a very early stage of enamel formation," said Moradian-Oldak, the study's senior author. "MMP-20 chops up proteins during the crystallization of enamel. Together with other enzymes, it gets rid of 'sludge' so the enamel making cells in the body can add more mineral and make enamel, the hardest bioceramic in the human body."

Dental restoration

Moradian-Oldak will couple the MMP-20 discovery with another study published Nov. 2 in the Journal of Biomedical Engineering and Informatics, which concluded an amelogenin-chitosan hydrogel could repair early tooth decay by growing an enamel-like layer that reduces lesions by up to 70 percent.

"Recognizing MMP-20's function in biomineralization is one of the first steps to learning how dental enamel forms in nature," said Qichao Ruan, lead author of the hydrogel study and a postdoctoral research associate in the Center for Craniofacial Molecular Biology at USC. "The findings regarding MMP-20 not only help us to further understand the mechanisms of enamel formation but [they] also can be applied in the design of novel biomaterials for future clinical applications in dental restoration or repair."

The Food and Drug Administration has not yet approved any type of enamel regrowing gel. USC is in pre-clinical trials. Moradian-Oldak said one day people may be able to use an overnight mouth guard or teeth strips saturated with hydrogel to regrow enamel-like substances and reduce teeth sensitivity.

Finding the right fix

Products such as toothpaste and mouthwash containing fluoride and casein phosphopeptide-amorphous calcium phosphate promote remineralization of initial enamel lesions; however, they need to be used regularly and are more of a tire patch than a real solution, Moradian-Oldak said. It plugs up the problem so people don't feel pain. The gel, however, fills the cracks and holes with an enamel-like substance.

In the United States, 92 percent of adults aged 20 to 64 have had dental decay in their permanent teeth, Moradian-Oldak said. Grinding teeth at night, gum recession and the disappearance of enamel over a lifetime due to demineralizing acidic food and drink are all common problems people everywhere face.

When tested in an environment that mimics an oral cavity's biochemical processes, the gel created a robust attachment, eliminating the threat of secondary cavities in the same spot, Ruan said. The gel could be more effective than traditional crowns, whose adhesion weakens over time, he added.

"Besides biocompatibility and biodegradability, the gel has unique antimicrobial and adhesion properties that are important for dental applications," Ruan said.

Watching cement dry could help dental fillings last longer

 

This shows typical dental glass cement, a UK innovation. It is made from glass powder, liquid polymer and water, and is the preferred non-toxic choice to mercury amalgam, which has been used for filling teeth for almost 200 years.

CREDIT

Semmelweis University Dental School

Scientists led by Queen Mary University of London (QMUL) and Aberystwyth University have revealed 'sweet points' for dental fillings, where cement used to fill cracks regain elasticity before hardening indefinitely. This could have implications for creating more durable and longer-lasting fillings in the future. 

Typical dental glass cement, a UK innovation, is made from glass powder, liquid polymer and water, and is the preferred non-toxic choice* to mercury amalgam, which has been used for filling teeth for almost 200 years. 

Publishing in the journal Nature Communications, the team used nano-level dentistry to measure how cement sets in real-time. 

They looked at the surface between the hard glass particles and surrounding polymer as the strength of the cement develops.

Guided by computer models, they used intense beams of neutrons from the Science and Technology Facilities Council's (STFC) neutron and muon source, to find that dental cement sets in fits and starts rather than hardening continuously. The findings identify 'sweet points' in time: when the cement starts to approach the toughness of the tissue that our teeth are made of and occur in first 12 hours of setting. 

Co-author Dr Gregory Chass from QMUL's School of Biological and Chemical Sciences explains: 

"Most of us have fillings in our teeth and know that a crack means a trip to the dentist for a replacement. 

"Our works opens up the possibility of tailoring the strength of non-mercury cements by homing in on the special setting points, which we call 'sweet points', to make environmentally-friendly dental fillings that not only last longer but could prevent further tooth decay."

Understanding 'sweet points' of dental cement could lead to better applications of fillings and easier treatment options for patients.

Co-author Professor Neville Greaves from the Department of Physics at Aberystwyth University said: 

"Dental fillings are really complex materials. Using neutrons we have discovered how mechanical toughness develops, element by element. This is fundamental physics in action for the general good."

The findings could have implications for other industries that use cement, such as construction, and to test toughness in other materials.

Andrew Taylor, Executive Director of STFC's National Laboratories, said: 

"It is always gratifying to see outcomes such as this coming from science at STFC's facilities and in this case, our neutron and muon source. Neutrons have such a broad range of applications and are used by scientists looking at everything from stresses and strains in plane wings to progressing methods to producing more effective antibiotics. 

"We can see here how a fundamental technique is applied to an everyday issue that we can all identify with."