Tag Archives: Fillings

Enamel-like gel could spell the end of dental fillings

Credit: Zhejiang University.

For thousands of years, humans have been battling tooth decay — and the longer we live, the worse it gets. The problem is that once our teeth lose their enamel — the hard mineralized surface of teeth — it never grows back. This is why dentists will remove the damaged enamel and fill it with a hard material that barely resembles the real thing. But not for long.

Chinese scientists at Zhejiang University and Xiamen University recently reported in the journal Science Advances that they’ve developed a special gel that can help tooth enamel repair itself.

The researchers started from clusters made of nanoparticles of calcium phosphate, the main ingredient of natural enamel. Each tiny cluster was doped with a chemical compound called triethylamine in order to prevent the clusters from clumping together.

The nanoparticles were then mixed with a gel that was applied to a sample of crystalline hydroxyapatite, a material that very closely resembles human enamel. Scanning electron microscopy revealed that the clusters created a layer that covered the sample.

The same experiment was carried out on real human teeth that had their enamel removed with acid. Within two days of application, the gel had formed a crystalline layer of approximately 2.7 micrometers. This layer had a fish-scale-like structure that closely resembles that of natural enamel. Tests also showed that the enamel substitute also had similar strength and wear resistance properties as the natural material.

Scanning electron microscope images of human tooth enamel after repairing for 6 hours, 12 hours and 48 hours. The blue area is the native enamel, and the green area is the repaired enamel. The black scale bars are 1 μm. Credit: Zhejiang University

This is not the first attempt at creating an enamel substitute but previous efforts could not fuse tightly with the real tooth. The new material can fuse in a single layer rather than multiple crystalline areas that can be very vulnerable to mechanical damage.

In the future, the researchers plan to carry out more tests in mice to make sure the gel has no undesirable side effects. These results are so far extremely promising, suggesting that in the future dental fillings could become obsolete.

Teeth.

Our immune systems may actually help create cavities, a new study finds

Researchers in the University of Toronto’s Faculty of Dentistry have found evidence that our own bodies could be the major driver of tooth decay and filling failure.

Teeth.

Image via Pixabay.

The study shows how the decay of dentin (the hard substance beneath our teeth’s enamel) and fillings isn’t the work of bacteria alone. Rather, they report, it’s the product of an unintentional ‘collaboration’ between bacteria and immune cells known as neutrophils. As these two do battle, our teeth suffer the collateral damage.

Carpet bombing

“No one would believe that our immune system would play a part in creating cavities,” says Associate Professor Yoav Finer, the lead author of the study and the George Zarb/Nobel Biocare chair in prosthodontics at the Faculty of Dentistry. “Now we have evidence.”

Neutrophils are a type of short-lived immune system cells that play an important role in combating inflammation throughout the body. These cells make their way into the oral cavity via the gums around our teeth, where they fight off any bacterial invaders. But as they track and engage these bacteria, neutrophils also inflict damage on the surrounding environment.

“It’s like when you take a sledgehammer to hit a fly on the wall,” Finer says. “That’s what happens when neutrophils fight invaders.”

Byproducts of these engagements are the problem, the team explains. On their own, neutrophils can’t cause meaningful damage to teeth; these cells can’t produce any acid to attack the mineral-rich compounds. However, as they engage in an attack, oral bacteria do employ acids in a bid to defend themselves — and these demineralize teeth.

It’s here that the problem starts. The now-weakened teeth become susceptible to enzymes released both by bacteria and neutrophils, and these enzymes start boring through the demineralized area of teeth and tooth-colored fillings. Dentin and tooth-colored fillings sustain damage “within hours” of a bacteria-neutrophil showdown, the team reports. The research helps better explain why so many patients who had cavities filled with tooth-colored fillings face high rates of recurrence of the cavities. Most tooth-coloured fillings fail within five to seven years, costing Canadians an estimated $3 billion a year, the paper explains.

“It’s a collaboration of destruction – with different motives,” says study author Michael Glogauer, professor of the Faculty of Dentistry and acting chief dentist at the Princess Margaret Cancer Centre.

“Ours is the first basic study to show that neutrophils can break down resin composites (tooth-coloured fillings) and demineralize tooth dentin,” says master’s student and first author of the paper, Russel Gitalis. “This suggests that neutrophils could contribute to tooth decay and recurrent caries.”

While the findings may seem bleak, they actually point the way towards new potential treatment strategies. The findings may also help us develop new filling materials and test their resilience in the lab, potentially leading to much more durable fillings.

The paper “Human neutrophils degrade methacrylate resin composites and tooth dentin” has been published in the journal Acta Biomaterialia.

Oldest cavities.

World’s oldest fillings come from the stone age and they’re basically asphalt

People have been going to the dentist for a much longer time than you’d believe. Archaeologists working in northern Italy have found the oldest known dental fillings. They were made from a mix of bitumen, hairs, and plants some 13,000 years ago.

Oldest cavities.

Image credits Stefano Benazzi.

There’s no such thing as a good toothache. That’s why we have dentists, and that seems to have been the case in the stone age, too — although I hear conditions weren’t as good back in the day. Faced with a lack of materials, tools, or you know, any sort of body of literature to guide their steps, ancient dentists had to be creative (they invented a lot of stuff back then). A pair of 13,000-year-old front teeth found in Italy stands testament to what they could achieve with a bunch of stones and bitumen.

Asphalt teeth

The teeth were discovered in the Riparo Fredian site near Lucca, northern Italy. Each one has a large cavity going from the surface all the way through to the pulp. They were probably hollowed out and enlarged with stone tools, judging by microscopic etches and markings on their walls. While poking though these holes, a research team lead by Gregorio Oxilia from the University of Bologna has found residues of bitumen with plant fibers and hairs mixed in. Although very different from what you’d see in today’s fillings, their purpose was probably the same — keep stuff away from the pulp and keep pain to a minimum.

“It is quite unusual, not something you see in normal teeth,” Stephano Benazzi, an archaeologist at the University of Bologna and corresponding author of the paper told New Scientist.

Benazzi noted that the etchings found in these teeth are similar to another set him and the team found in Italy in previous research. That set of teeth was dated as 14,000 years old, the oldest known evidence of dentistry we’ve ever seen. But this is the (new) first time we know of fillings being used.

Fredian upper central incisors.

Image credits Gregorio Oxilia.

It’s probable that the Paleolithic dentist drilled out the cavities and then filled them in — just like his modern counterparts would do. However, he only had tiny stone tools to drill with, probably no anesthetics, and bitumen to use for the fill. The team is unsure as to why the hairs and plant fibers were added to the mix (they did rule out the possibility of them being remains of food since they were added to the area after drilling). One theory is that the plants were chosen for their antiseptic properties, helping to keep the cavity healthy and clean of bacteria. Or the dentists thought fibers would help fix the filling. We don’t yet know.

What’s really striking is the time-frame of the fillings. They’re evidence of relatively advanced knowledge being put to use in fixing an ailment thousands of years before we though they’d become a significant affliction — the change in diet agriculture brought on is thought to have lead to a dramatic increase in cavities. Still, at this time Europe was seeing a lot of people migrating in from the near East, Benazzi adds. The foods they introduced to the continent may have led to more cavities, and then to dentistry.

The full paper “The dawn of dentistry in the late upper Paleolithic: An early case of pathological intervention at Riparo Fredian” was published in the American Journal of Physical Anthropology.