Mind the gap – ESRF tracks defects triggered by composites in root fillings

Polymer composite fillings of root-canal treated teeth can fail over time. Scientists led by the Charité University in Berlin (Germany) have found that this is not because of the dentist’s lack of skills but rather because of stresses that build up and deform the biomaterial just after it is placed. The results are published in Acta Biomaterialia.

It is one of the most peculiar images that can come to mind: a dentist restoring severely destroyed teeth and placing fillings on a beamline at a synchrotron. It is, however, exactly what happened on beamline ID19 a while back, when a team from the Charité and TU Universities in Berlin and the ESRF examined how well composite fillings adapt to cavities in the tooth root canal orifice.

To treat cavities in teeth, dentists expose solid tooth tissue prior to “filling” the volume of missing structure with rigid biomaterials that sustain chewing forces. In the past, dentists used metals such as amalgam or gold, but today they mostly use composite materials, made of polymer and glass. Such materials, which are well resistant to damage and highly aesthetic, allow rapid recovery of tooth function. However, composites tend to fail in the long run, especially in root-canal filled teeth.

Read more on the ESRF website

Image: Kerstin Bitter placing a filling on a tooth on ID19’s experimental hutch.

Credit: P. Zaslansky.

Research on ancient teeth reveals complexity of human evolution

Fossil records enable a detailed reconstruction of our planet’s history and of the evolution of our species. In particular, teeth are a sort of biological archive that record in their structures (enamel, dentine and pulp chamber) the different phases of the human evolution. An international team of researchers led by Clément Zanolli from the Université Toulouse III Paul Sabatier (France) has characterized human dental remains from Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), Italy through a comparative high-resolution endostructural analysis based on microfocus X-ray microtomography (mCT) scanning and detailed morphological analyses. We examined the shape and arrangement of tooth tissues (see Fig. 1) and compared them with teeth of other human species (see Fig. 2).

With an age of around 450,000 years before present, the analysed dental remains from the sites of Fontana Ranuccio, located 50 km south-east of Rome, and Visogliano, located 18 km north-west of Trieste, are part of a very short list of fossil human remains from Middle Pleistocene Europe and are among the oldest human remains on the Italian Peninsula.
From the data obtained through X-ray μ-CT measurements performed at the TomoLab station of Elettra and at the Multidisciplinary Laboratory of the ‘Abdus Salam’ International Centre for Theoretical Physics in Trieste (Italy), we found that the teeth of both sites share similarities with Neanderthals but they are distinct from modern humans. This study adds to an emerging picture of complex human evolution in Middle Pleistocene Eurasia.  The investigated fossil teeth show that Neanderthal dental features had evolved by around 450,000 years ago.

>Read more on the Elettra Sincrotrone Trieste website

Image: Volume rendering of the Fontana Ranuccio (FR1R and FR2) and Visogliano (Vis. 1-Vis. 6) tooth specimens. The enamel is represented in blue while the dentine in yellow. All specimens were imaged by X-ray μCT at the Tomolab station of Elettra and at the Multidisciplinary Laboratory of the ICTP.     
Credit:  doi: 10.1371/journal.pone.0189773

Research shows how to improve the bond between implants and bone

Research carried out recently at the Canadian Light Source (CLS) in Saskatoon has revealed promising information about how to build a better dental implant, one that integrates more readily with bone to reduce the risk of failure.

“There are millions of dental and orthopedic implants placed every year in North America and a certain number of them always fail, even in healthy people with healthy bone,” said Kathryn Grandfield, assistant professor in the Department of Materials Science and Engineering at McMaster University in Hamilton.

A dental implant restores function after a tooth is lost or removed. It is usually a screw shaped implant that is placed in the jaw bone and acts as the tooth roots, while an artificial tooth is placed on top. The implant portion is the artificial root that holds an artificial tooth in place.

Grandfield led a study that showed altering the surface of a titanium implant improved its connection to the surrounding bone. It is a finding that may well be applicable to other kinds of metal implants, including engineered knees and hips, and even plates used to secure bone fractures.

About three million people in North America receive dental implants annually. While the failure rate is only one to two percent, “one or two percent of three million is a lot,” she said. Orthopedic implants fail up to five per cent of the time within the first 10 years; the expected life of these devices is about 20 to 25 years, she added.

“What we’re trying to discover is why they fail, and why the implants that are successful work. Our goal is to understand the bone-implant interface in order to improve the design of implants.”

>Read more on the Canadian Light Source website

The microstructure of a parrotfish tooth contributes to its toughness

During a 2012 visit to the Great Barrier Reef off the coast of Australia, ALS staff scientist Matthew Marcus became intrigued with parrotfish. “I was reminded that this is a fish that crunches up coral all day and is responsible for much of the white sand on beaches,” Marcus said. “But how can this fish eat coral and not lose its teeth?” So Marcus teamed up with Pupa Gilbert, a biophysicist at the University of Wisconsin–Madison, and an international team of researchers she assembled, to understand how parrotfish teeth work.

Because conventional microscopes can overlook the unique orientation of crystals in tooth enamel, the team used the technique called polarization-dependent imaging contrast (PIC) mapping that Gilbert invented, which uses the photoemission electron microscopy (PEEM) Beamline 11.0.1 at the ALS. The PIC maps allowed them to visualize the orientation of individual crystals of fluorapatite, the main mineral component of parrotfish teeth.

Separate experiments used tomography (Beamline 8.3.2) and microdiffraction (Beamline 12.3.2) to further analyze the crystal orientations and strains in the teeth.

>Read more on the ALS website

Image: (extract) PIC maps acquired at the tips of four different parrotfish teeth show that they consist of 100-nm-wide, microns-long crystals, bundled into “fibers” interwoven like warp and weft fibers in fabric. These fibers gradually decrease in average diameter from 5 μm at the back of a tooth to 2 μm at the tip. Intriguingly, this decrease in size is spatially correlated with an increase in hardness and stiffness. The orientation angle of the crystals is color-coded (chart at bottom).


Research on the teeth of a prehistoric fetus

It gives us information about the last months of a mother and child, who lived 27.000 years BP.

Fossil records enable a detailed reconstruction of our planet’s history and of the evolution of our species. Dental enamel is a sort of biological archive that constantly tracks periods of good and bad health, while forming. Prenatal enamel, which grows during intrauterine life, reports the mother’s history as well.

We have studied fossil records found in the “Ostuni 1” burial site, discovered in Santa Maria di Agnano in Puglia in 1991 by Donato Coppola (Università di Bari, Italy) and dated back over 27,000 years. More specifically, we were interested in the teeth of a fetus found in the pelvic area of the skeleton of a young girl. By analysing the still forming teeth of the baby, it has been possible to obtain information about the health condition of the mother during the last months of pregnancy, to establish the gestational age of the fetus, and also to identify some specificities of the embryonal development. For the first time, it has been possible to reconstruct life and death of an ancient fetus and, at the same time, to shed light on its mother’s health.

Three still-forming incisors, belonging to the fetus, have been visualized and analyzed by means of X-ray microtomography at Elettra. The preliminary analysis on a portion of the fetal mandible, realized at the TomoLab laboratory allowed us to study the still-forming incisor contained within it (see Fig. 1). Thanks to the unique properties of synchrotron radiation and using a specifically-developed methodology, a high resolution 3D analysis has been carried out on the teeth at the SYRMEP beamline. This approach, allowed us to carry out a virtual histological analysis of the precious fossil teeth, revealing the finest structures of the dental enamel in a non-destructive way.

>Read more on the Elettra website

Image:  Pseudo color rendering of the virtual histological section of the Ostuni1b’s upper left deciduous central incisor. The corresponding CT scan has been acquired at the SYRMEP beamline in phase-contras mode.

X-Rays reveal the biting truth about parrotfish teeth

Interwoven crystal structure is key to coral-crunching ability

So, you thought the fictional people-eating great white shark in the film “Jaws” had a powerful bite. But don’t overlook the mighty mouth of the parrotfish – its hardy teeth allow it to chomp on coral all day long, ultimately chewing and grinding it up through digestion into fine sand. That’s right: Its “beak” creates beaches. A single parrotfish can produce hundreds of pounds of sand each year.

Now, a study by scientists – including those at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) – has revealed a chain mail-like woven microstructure that gives parrotfish teeth their remarkable bite and resilience.

The natural structure they observed also provides a blueprint for creating ultra-durable synthetic materials that could be useful for mechanical components in electronics, and in other devices that undergo repetitive movement, abrasion, and contact stress.

Matthew Marcus, a staff scientist working at Berkeley Lab’s Advanced Light Source (ALS) – an X-ray source known as a synchrotron light source that was integral in the parrotfish study – became intrigued with parrotfish during a 2012 visit to the Great Barrier Reef off of the coast of Australia.

>Read More on the ALS website

Image: Scientists studied the microstructure of the coral-chomping teeth of the steephead parrotfish, pictured here, to learn about the fish’s powerful bite.
Credit: Alex The Reef Fish Geek/Nautilus Scuba Club, Cairns, Australia