Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Home tooth bleaching slightly reduces enamel strength

16.04.2009
New research shows that human teeth lost some enamel hardness after the application of several different products used in the home to whiten teeth. The study suggests that future generations of such products might be reformulated in an effort to reduce these side effects.

The researchers noted that teeth typically can restore their previous hardness after losing small amounts of enamel calcification. But this is the first study to show at a nanometer scale – measuring in billionths of a meter – how human teeth are affected by the popular home whiteners.

“There is some significant reduction in nano-hardness of enamel, but we are talking on a very minute scale. So even though it may not be visible to the human eye, it’s important for research because that’s how we improve products,” said Shereen Azer, assistant professor of restorative and prosthetic dentistry at Ohio State University and lead author of the study.

Azer and colleagues applied the recommended treatments of five name-brand home whiteners to samples of human teeth and compared the effects to tooth samples that received no treatment. In all cases, the products reduced the hardness of the enamel as well as what is called the elastic modulus or stiffness, a measure of the ability of the tooth surface to bounce back in response to applied force.

Many studies have sought to determine how tooth whitening affects tooth enamel hardness, but results have been inconclusive. Azer said that previous studies measured the loss of enamel hardness in microns, or millionths of a meter, rather than on the nanometer scale used in his study.

“So this just gives us a better understanding of precisely how these products affect human teeth,” he said.

The research is published in a recent issue of the Journal of Dentistry.

Tooth bleaching products contain solutions of various strengths of either hydrogen peroxide or carbamide peroxide, which provide the whitening effect. They bleach teeth by producing unstable free radicals that attack pigment molecules in the organic parts of enamel. The reduction in pigment means the molecules no longer reflect light, so the teeth appear whiter.

Enamel, which is almost entirely inorganic and translucent, appears yellow in most teeth because it reflects the color of the dentin underneath, which is naturally yellow.

“Especially nowadays, people tend to see beauty in white teeth,” Azer said. “And bleaching does have a beautiful effect, but not without side effects.”

The study did not test for two other common side effects of tooth whitening, gum irritation and tooth sensitivity. Azer said these side effects have been addressed by other products, such as toothpastes and treatment gels designed to lessen sensitivity and irritation.

He and colleagues used extracted molars to assemble 65 human tooth samples measuring 4 millimeters square and 2 millimeters deep for the study. Ten samples were used in a pilot study that determined they could achieve accurate results for the research under dry conditions rather than wet conditions simulating the presence of saliva.

Of the remaining samples, five were left untreated, and 50 were divided into five groups of 10 each to undergo treatment.

The researchers used whitening strips on two groups of samples and trays filled with whitening gel on three groups. The treatment times included up to 60 minutes once per day or 60 minutes twice per day according to manufacturer recommendations. All treatments lasted for three weeks except for one tray method, which lasted 10 days.

The treatments included both over-the-counter and professionally provided products to be used in the home.

The scientists used a specialized tool to apply force to test the enamel hardness and stiffness (the surface ability to bounce back), and an atomic force microscope to observe the tiny nanometer-scale effects on the teeth.

The average loss of enamel ranged from 1.2 to 2 nanometers on the treated teeth. The control teeth, on average, actually gained 0.4 nanometers of hardness in comparison over the treatment time frame. The surface ability to bounce back from applied force was reduced by an average of between 6 percent and 18.8 percent among the treated teeth, depending on the type of treatment.

Among the different products, most of the reductions in hardness and elastic modulus were similar. However, there was a significant difference between one strip treatment method and one tray method, with the tray method reducing enamel hardness more dramatically than the strip treatment.

Enamel is the hardest structure in the human body. It protects teeth and maintains the integrity of the bite. But enamel is subject to abrasion by certain products and even too-vigorous brushing, which is why it is important to figure out ways to reduce damage to this part of the tooth, Azer said.

“In the case of these products, manufacturers might be able to alter the concentrations of the materials and the vehicles used to apply the bleach,” he said.

The study did not address how to restore hardness to bleached teeth, but Azer noted that extensive research has indicated that fluoride treatments, including the use of fluoride toothpaste, can promote enamel remineralization.

The products used in the study were Crest Whitestrips Premium Plus, Crest Whitestrips Supreme, Nite White ACP, Oral B Rembrandt and Treswhite Opalescence. The final three are tray treatments.

Azer conducted the research with Camilo Machado and Robert Rashid of the Division of Restorative and Prosthetic Dentistry and Eliana Sanchez of the Division of Primary Care, all in Ohio State’s College of Dentistry.

Contact: Shereen Azer, (614) 292-7467; Azer.1@osu.edu
Written by Emily Caldwell, (614) 292-8310; Caldwell.151@osu.edu

Shereen Azer | EurekAlert!
Further information:
http://www.osu.edu

More articles from Health and Medicine:

nachricht Biofilm discovery suggests new way to prevent dangerous infections
23.05.2017 | University of Texas at Austin

nachricht Another reason to exercise: Burning bone fat -- a key to better bone health
19.05.2017 | University of North Carolina Health Care

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>