There are always bacteria lurking in dental equipment, suggests research

Bacteria lurking in the water lines at the dentist's office are tougher than we thought, according to a new paper published in Water Research. The study reveals that the disinfectants recommended by companies that manufacture the water lines don't actually shift all the bacteria in the lines, which means they're never completely clean.

Dental equipment is particularly prone to contamination with bacteria, yeasts and other microbes because it comes into contact with people's mouths. Dentists use dental unit water lines to keep their electrical equipment cool. 

In the new study, researchers from Université de Poitiers in France analyzed three disinfectants used by some European dentists to control biofilms in dental water lines: Calbenium®, Oxygenal 6® and Sterispray®. The team tested how well the disinfectants removed biofilms from dental water lines and found that none of them were completely effective on a polymicrobial biofilm.

"During dental procedures, patients and dentists can be exposed to microorganisms present in the water circulating inside dental units," said Dr. Damien Costa, lead author of the study from Université de Poitiers. "Infections may occur if this potentially microbiologically contaminated water is inhaled or splashed. We wanted to determine the best way to keep dental lines clean and avoid infection." 

There has long been concern about how clean dental lines are, and there have been some - albeit rare - documented cases of them causing infections in people. In 2011, an 82-year-old woman was admitted to hospital with trouble breathing and was diagnosed with Legionnaire's disease, which she had contracted via a contaminated dental water line. She died two days later.

One challenge associated with keeping dental water lines clean is that bacteria can grow in communities with protective layers over themselves, called biofilms. Biofilms can be particularly difficult to prevent and remove even using disinfectants.

Dr. Costa and his colleagues grew biofilms in the laboratory in conditions similar to dental water lines. The biofilms contained several different microbes, to mimic the complex biofilms that form in real lines: the bacterium Pseudomonas aeruginosa, which can cause pneumonia and septic shock, the fungus Candida albicans, which can also cause superficial and severe infections, and free living amoebae Vermamoeba vermiformis. These amoebae can be dangerous - they're known as "Trojan horses" because they carry some bacteria that can infect humans, like Legionella pneumophila, which causes Legionnaire's disease.

All three disinfectants were especially active against the fungus, but none of them were completely effective at clearing the entire biofilm. Calbenium® was most effective at clearing biofilms and stopping new ones from forming, even at concentrations below what the manufacturers recommend. However, it did not kill the free living amoebae.

"Unfortunately, our results showed that none of the three disinfectants commonly used are completely effective," said Dr. Costa. "What is most worrying is that none of the disinfectants could kill the amoebae, which means they are still dangerous to patients and dentists even after water lines have been sterilized."

The researchers say preventing the formation of biofilms as long as possible is key to keeping the lines clean, as once they have formed, they can't be killed using disinfectant. It's difficult to stop biofilms from forming, since microbes naturally cling on to surfaces. However, the research highlighted three approaches to prevention: use good quality water that isn't contaminated with microbes, use a disinfectant for prevention, rather than to remove biofilms that have already formed, and avoid letting water stagnate.

Maintaining tooth-borne and implant-borne dental restorations

  

Patients with dental restorations such as crowns, bridges and veneers that are supported by natural teeth, as well as those with restorations supported by implants, can keep their teeth healthy with careful lifelong maintenance. Using the best level of available evidence, the American College of Prosthodontists, working with the American Dental Association, Academy of General Dentistry, and American Dental Hygienists Association, recently published the first clinical practice guidelines for patients and dental professionals as they care for tooth-borne and implant-borne restorations. 

"Patients with multiple restorations that are supported by natural teeth or implants need to know that professional and at-home maintenance is a lifelong regimen," said Dr. Avinash Bidra, lead author of the guidelines, which are published in the Journal of Prosthodontics. "We are telling professionals what guidelines to follow and what to tell patients for at-home maintenance."

No more needles at the dentist -- just a tiny electric current instead

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If you're scared of the dentist's needles you're not alone -- but new research means you might not have to put off that appointment again. A study published in Colloids and Surfaces B: Biointerfaces reveals how the dentist could give you anesthetic using a tiny electric current instead of a needle.

The researchers behind the study, from the University of São Paulo, say their new findings could help improve dental procedures and bring relief to millions of people who are scared of needles. It would also save money and avoid contamination and infection, they say.

"Needle-free administration could save costs, improve patient compliance, facilitate application and decrease the risks of intoxication and contamination," explained Professor Renata Fonseca Vianna Lopez, one of the authors of the study from the University of Sao Paulo in Brazil. "This may facilitate access to more effective and safe dental treatments for thousands of people around the world."

Dentists often have to carry out invasive and painful procedures in the mouth. To minimize patients' discomfort, dentists use anesthetics that block the pain, which are administered using needles. However, many patients are extremely afraid of these injections, resulting in them postponing and even canceling visits to the dentist.

For these patients, an additional step is needed: dentists first give them a topical painkiller to reduce the pain -- and associated fear -- caused by the needle. This can come in the form of a hydrogel, ointment or sprays; the most common are hydrogels that can contain lidocaine and prilocaine.

In the new study, the researchers investigated a way of getting these topical anesthetics into the body more effectively, to see if they could replace needles altogether. They found that applying a tiny electric current -- a process called iontophoresis -- made the anesthetics more effective.

The researchers first prepared the anesthetic hydrogels with a polymer to help it stick to the lining of the mouth. They added two anesthetic drugs, prilocaine hydrochloride (PCL) and lidocaine hydrochloride (LCL). They tested the gel on the mouth lining of a pig, applying a tiny electric current to see if it made the anesthetic more effective. 

The anesthesia was fast-acting and long-lasting. The electric current made the prilocaine hydrochloride enter the body more effectively; the permeation of the anesthetic through the mouth lining increased 12-fold.

The researchers say the technology has applications not only in dentistry anesthesia, but also in other areas such as cancer treatment.

"Over the last few years, our research group has been working on the development of novel drug delivery systems for the treatment of several skin and eye diseases," said Prof. Lopez. "The skin and eyes pose challenges for drug delivery, so we have focused on improving drug delivery in these organs using nanotechnology, iontophoresis and sonophoresis, which is permeation using sound waves."

The researchers now plan to develop an iontophoretic device to use specifically in the mouth and do some preclinical trials with the system.

Inorganic mercury is from dental fillings is very damaging to key cell processes

University of Georgia research has found that inorganic mercury, which was previously thought to be a less harmful form of the toxic metal, is very damaging to key cell processes.

This study is the first to compare the effects of inorganic and organic mercury compounds at the biochemical, physiological and proteomic levels in any model organism, according to the study's lead author Stephen LaVoie, a microbiology doctoral student. Published in December in the Journal of Biological Inorganic Chemistry, the research looked at how inorganic and organic mercury affected specific molecular processes.

Inorganic mercury from the ore cinnabar was used for centuries against infections; in modern times, humans synthesized organic mercurials as antimicrobials, such as merthiolate.

"Today, most human exposure to inorganic mercury is from dental fillings, and organic mercury exposure is from methylmercury in fish," said study co-author Anne Summers, a microbiology professor in the Franklin College of Arts and Sciences.

Organic mercury exposure is associated with neurological disease, LaVoie explained, whereas inorganic mercury is known to cause neurological, kidney and autoimmune diseases. However, the molecular basis for their distinct toxicity profiles was not understood.

Owing to concern about fish consumption, most research has emphasized organic mercury, assuming it was more toxic, LaVoie said. But comparing them on key cellular processes, he found that inorganic mercury "caused more damage at lower concentrations than organic mercury."

For his study, LaVoie used a common lab strain of E. coli bacteria as a model cellular system. He exposed growing cells to mercury compounds and measured their reactive sulfur called thiols -- essential metals and proteins that naturally bind essential metals via amino acid thiols.

"We used a fluorescent probe to detect thiols," LaVoie said. After mercury exposure the thiols decreased more with inorganic than organic mercury. Inorganic mercury was much more efficient at removing iron from iron-dependent proteins than the best organic mercury compound tested.

"As fellow oxygen-breathing creatures, it's important to know that inorganic mercury is more potent than organic mercury in disrupting protein-iron centers such as those we have in our own cells, " Summers said.

"More is being learned about the bacteria in and on our bodies," LaVoie said. "What we ingest affects them, too, and their health affects our health."

Future work will examine the mercury resistance genes that many bacteria have and how these genes help spread antibiotic resistance genes.

Dental implant complications and peri-implantitis

The International and American Associations for Dental Research (IADR/AADR) have published in the January issue of the Journal of Dental Research articles that explore new evidence on the biological complications of dental implants and the great challenges associated with predictable implant therapy.

Dental implants have become an important treatment for the replacement of teeth lost due to disease, injury or congenital tooth agenesis. Over the past 30 years, the incorporation of dental implants into everyday clinical dental practice has resulted in major improvements in oral health of patients through enhancements in function, esthetics and phonetics.

"While dental implant therapy remains an important treatment modality to replace missing teeth, these studies also underscore the importance of tooth preservation in patients susceptible to gum infections such as periodontitis. The caution is that careful assessments and treatment planning amongst dental generalists and specialists should be performed to optimize the clinical decision-making for patients receiving advanced reconstructive implant or periodontal therapy," said JDR Editor William Giannobile. "We believe the outcomes of these studies will be beneficial to patient care and oral health."

The erroneous belief of implants yielding a better long-term prognosis than teeth has now clearly been rejected in several comparative studies and systematic reviews. Teeth even compromised because of periodontal disease or endodontic problems may have a longevity that surpasses that of the average implant in many cases.

Some of the articles in the January issue that elaborate on the prevalence of peri-implantitis and risk of dental implant loss include an editorial from Dennis Tarnow on 'Increasing Prevalence of Peri-implantitis-How Will We Manage?'; and another editorial 'Are Dental Implants a Panacea or Should We Better Strive to Save Teeth?', authored by William Giannobile and Klaus Lang; 'Surgical Treatment of Peri-implantitis. A Randomized Controlled Clinical Trial' by Olivier Carcuac et al; 'Prevalence of Peri-implantitis' by Jan Derks et al among other papers in this issue.

This issue also includes a freely accessible podcast to the JDR article titled 'Prevalence of Peri-implantitis' of an interview with leading experts in implant therapy by Tord Berglundh of the Sahlgrenska Academy, Department of Periodontology at Gothenburg University, Sweden and Dennis Tarnow of Columbia University in New York, USA. Please visit the JDR website at jdr.sagepub.com/site//misc/Index/Podcasts.xhtml to access the podcast.

Tooth fillings of the future may incorporate bioactive glass

A few years from now millions of people around the world might be walking around with an unusual kind of glass in their mouth, and using it every time they eat.

Engineers at Oregon State University have made some promising findings about the ability of "bioactive" glass to help reduce the ability of bacteria to attack composite tooth fillings - and perhaps even provide some of the minerals needed to replace those lost to tooth decay.

Prolonging the life of composite tooth fillings could be an important step forward for dental treatment, the researchers say, since more than 122 million composite tooth restorations are made in the United States every year. An average person uses their teeth for more than 600,000 "chews" a year, and some studies suggest the average lifetime of a posterior dental composite is only six years.

The new research was just published in the journal Dental Materials, in work supported by the National Institutes of Health.

"Bioactive glass, which is a type of crushed glass that is able to interact with the body, has been used in some types of bone healing for decades," said Jamie Kruzic, a professor and expert in advanced structural and biomaterials in the OSU College of Engineering.

"This type of glass is only beginning to see use in dentistry, and our research shows it may be very promising for tooth fillings," he said. "The bacteria in the mouth that help cause cavities don't seem to like this type of glass and are less likely to colonize on fillings that incorporate it. This could have a significant impact on the future of dentistry."

Bioactive glass is made with compounds such as silicon oxide, calcium oxide and phosphorus oxide, and looks like powdered glass. It's called "bioactive" because the body notices it is there and can react to it, as opposed to other biomedical products that are inert. Bioactive glass is very hard and stiff, and it can replace some of the inert glass fillers that are currently mixed with polymers to make modern composite tooth fillings.

"Almost all fillings will eventually fail," Kruzic said. "New tooth decay often begins at the interface of a filling and the tooth, and is called secondary tooth decay. The tooth is literally being eroded and demineralized at that interface."

Bioactive glass may help prolong the life of fillings, researchers say, because the new study showed that the depth of bacterial penetration into the interface with bioactive glass-containing fillings was significantly smaller than for composites lacking the glass.

Fillings made with bioactive glass should slow secondary tooth decay, and also provide some minerals that could help replace those being lost, researchers say. The combination of these two forces should result in a tooth filling that works just as well, but lasts longer.

Recently extracted human molars were used in this research to produce simulated tooth restoration samples for laboratory experiments. OSU has developed a laboratory that's one of the first in the world to test simulated tooth fillings in conditions that mimic the mouth.

If this laboratory result is confirmed by clinical research, it should be very easy to incorporate bioactive glass into existing formulations for composite tooth fillings, Kruzic said.

The antimicrobial effect of bioactive glass is attributed, in part, to the release of ions such as those from calcium and phosphate that have a toxic effect on oral bacteria and tend to neutralize the local acidic environment.

"My collaborators and I have already shown in previous studies that composites containing up to 15 percent bioactive glass, by weight, can have mechanical properties comparable, or superior to commercial composites now being used," Kruzic said.

Periodontal disease associated with increased breast cancer risk in postmenopausal women

Bottom Line: Postmenopausal women with periodontal disease were more likely to develop breast cancer than women who did not have the chronic inflammatory disease. A history of smoking significantly affected the women's risk. 

Journal in Which the Study was Published: Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research

Author: Jo L. Freudenheim, PhD, distinguished professor in the Department of Epidemiology and Environmental Health in the University at Buffalo's School of Public Health and Health Professions.

Background: Periodontal disease is a common condition that has been associated with heart disease, stroke, and diabetes. Previous research has found links between periodontal disease and oral, esophageal, head and neck, pancreatic, and lung cancers, so the researchers wanted to see if there was any relationship with breast cancer.

How the Study Was Conducted: Freudenheim and colleagues monitored 73,737 postmenopausal women enrolled in the Women's Health Initiative Observational Study, none of whom had previous breast cancer. Periodontal disease was reported in 26.1 percent of the women. Because prior studies have shown that the effects of periodontal disease vary depending on whether a person smokes, researchers examined the associations stratified by smoking status. 

Results: After a mean follow-up time of 6.7 years, 2,124 women were diagnosed with breast cancer. The researchers found that among all women, the risk of breast cancer was 14 percent higher in women who had periodontal disease. 

Among women who had quit smoking within the past 20 years, those with periodontal disease had a 36 percent higher risk of breast cancer. Women who were smoking at the time of this study had a 32 percent higher risk if they had periodontal disease, but the association was not statistically significant. Those who had never smoked and had quit more than 20 years ago had a 6 percent and 8 percent increased risk, respectively, if they had periodontal disease.

Author Comment: "We know that the bacteria in the mouths of current and former smokers who quit recently are different from those in the mouths of non-smokers," Freudenheim explained. One possible explanation for the link between periodontal disease and breast cancer is that those bacteria enter the body's circulation and ultimately affect breast tissue. However, further studies are needed to establish a causal link, Freudenheim said.

Study Limitations: Women self-reported their periodontal disease status, after being asked whether a dentist had ever told them they had it. Also, since the study focused on women who were already enrolled in a long-term national health study, they were more likely than the general population to be receiving regular medical and dental care, and were likely more health-conscious than the general population.