Looking into the evolution of mankind through the findings of fossil teeth

In the department of Paleoanthropology and Messel Research of the Frankfurt based Senckenberg Research Institute and National History Museum, very fine textures of tooth surfaces are scientifically examined by aid of high-resolution virtual tooth models, with the main emphasis being on the molar teeth of human beings and other primates. 

To analyse the aspect of occlusion (contact between the teeth of the upper and lower jaw) as well as the function of mammal teeth, an interdisciplinary working group of paleontologists, paleoanthropologists, dentists and dental technicians has examined and evaluated respective findings based on their digital replica generated with the help of an AICON scanning system. The combination of different research approaches as well as the exchange of different, yet complimenting specialist knowledge helps to promote the general understanding of the natural shape and functional evolution of tooth crowns.

Objective and measuring object

Teeth as an insight into prehistoric times: Archaeological teeth findings are of particular research interest not only for the area of dental medicine, but also very much so for the field of paleontology (science of prehistoric living creatures and organisms): The only way to identify many of the extinct animal species is through the remains of their dentition. Scientists use the teeth remains for the reconstruction of former environmental conditions, the geographical extension and phylogenetic analysis of animal species as well as their chronological classification in the evolutionary history. 

Already very early paleontological examinations of the fossils have shown indications that not only the overall organism but also the teeth are being subjected to evolutionary changes with regard to their size, shape and quantity. Among other aspects, the teeth surfaces are affected by the physical properties of the ingested food particles which have a major effect on the individual tooth profile.

By analysing the chewing surfaces of the teeth, paleontologists 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 conditions of how our ancestors used to live. 

The fossil remains, dating back over almost 200 million years of mammal evolution, provide documentation of the continuous evolutionary changes of the teeth of different types of beings. The chewing process and specific properties of the nutrition intake, together with characteristic behavioral 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 significantly characterised by their 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 Analyzer), 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.

Measuring system and setup

Different approaches for the 3D 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. It is a very time consuming procedure as the objects firstly have to be prepared with reference 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 paleoanthropology and paleontology, the opticalnmeasuring approach with the AICON SmartScan is the best suited scanning method. It operates contact-free, it digitises the surface area within just a matter of seconds, captures large data volumes at a very high level of accuracy and is easily adjusted to any object size. 

Using the AICON SmartScan, fast and precise digitisation of the archaeological findings is quickly accomplished within just a few measurements. The flexible sensor configuration, one of the key characteristic features of the SmartScan series, enables the execution of scanning processes at triangulation angles of 30°, 20° und 10°, allowing for even very difficult accessible object areas to be captured with high-detail accuracy.

Workflow

To capture very reflecting surfaces like 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 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 scans are also carried out on highly precise dental casts which have been reproduced as negative molds 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 scanner AICON SmartScan.

The system calibration is followed by the 3D 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 the AICON SmartScan nables the Senckenberg Research Industry and National History Museum to capture even their extremely delicate paleontological 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 3D 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.