Fossil Teeth

By analysing the chewing surfaces of the teeth, palaeontologists are able to capture and interpret their respective functional changes. In doing so, it is possible to explain adaptations to the different kinds of available foodstuffs and indirectly to derive clues with regard to the climate conditions of past times. Thanks to the knowledge about the abrasion process of teeth, a functional teeth profile comparison can help draw conclusions about our ancestors’ way of life. The information gathered gives insight for instance into the proportion of fruit, types of grass and leaves and meat in the diet of human beings and other living creatures, allowing the reconstruction of the circumstances and conditions of how our ancestors used to live. The fossil remains, dating back over almost 200 million years of mammal evolution, provide enlightening documentation of the continuous evolutionary changes of the teeth of different types of organisms and beings. The chewing process and specific properties of the nutrition intake, together with characteristic behavioural patterns, leave behind clear and distinct traces on the surfaces of the teeth. Applying this kind of knowledge, recent studies of surface abrasions of the so-called contact facets of teeth crowns have shown evidence that Neanderthals had a much more varied diet than previously assumed, whereby the food supply was to a significant degree characterised by the respective living environment.

In the 3D laboratory of the Senckenberg Institute, the chewing surface, i.e. the contact surfaces of upper and lower jaw, are thoroughly examined. Using a special software (Occlusal Fingerprint Analyser), newly developed with the help of research funding kindly sponsored by the German Research Foundation (DFG-FOR771), the action of the masticatory movements can be simulated through triangulated surface models and quantitatively evaluated.

Technology

Different approaches for the three-dimensional scanning of the tooth surfaces are possible: Mechanic measurements, for example, capture objects on a point by point basis with the aid of tactile probes; a very time consuming procedure as the objects firstly have to be prepared with measuring time markers. Due to the point-based acquisition approach, in some cases the measuring times can take several hours, or even days. Besides, tactile measuring methods are only to a certain degree appropriate for delicate fossil objects which could be damaged during the probing process. For studies in the fields of palaeanthropology and palaeontology, it hence is the optical topometric measuring approach with the aid of the smartSCAN ^3D system which is the best suited scanning method; it not only operates contact-free, it also digitises the surface area within just a matter of seconds, captures large data volumes at a very high level of accuracy and thanks to its flexible design is easily adjusted to any object size.

Workflow

In order to capture very reflecting surfaces, as it is the case with tooth surfaces coated by transparent dental enamel, at the required accuracy to detail, there are - subject to the condition of the original - two options to prepare the research object: In most cases, it is sufficient to spray the surfaces to be measured (or the entire object) with an anti-reflection substance prior to the digitisation (the spray can be easily removed with water without leaving any residue).

In case of very sensitive objects, the Senckenberg Research Institute steams the surfaces with ammonium chloride, a powder heated in a flask and thereafter evenly sprayed onto the object with the aid of a small pump operated nozzle. Alternatively, on occasion the scans are also carried out on highly precise dental casts which have been reproduced as negative moulds with the help of high-definition dental materials and then cast, for instance, in dental stone (Everest® Rock, KaVo). These castings made of special non-reflective plaster are perfect replicas which are ideally suited for the white-light smartSCAN ^3D scanning system.

The system calibration is followed by the three-dimensional measurement of the tooth surface within a single measuring sequence of around one second. After calculation of the 3D data in the computer, the exact digital image of the object is available, ready to be used for in-depth studies as well as for documentation and archiving purposes.

Conclusion

Using Breuckmann‘s smartSCAN ^3D enables the Senckenberg Research Industry and National History Museum to capture even their extremely delicate palaentological findings contact-free as well as at high speed and precision. By performing research studies using digital replica, the original finding is not only preserved, the three-dimensional scan data also allows for even more detailed studies of the tooth surfaces than it would be possible using their originals. Moreover, the use of a corresponding digital data archive allows research studies and evaluations of the same finding to be conducted anywhere in the world at the same time – simply by accessing the
worldwide web!

Information material and pictures have been kindly provided by the Senckenberg Research Institute and Natural History Museum. Upon request, we are pleased to provide a bibliography of related articles.