D2 ORTHO TRIBUNE Dental Tribune Middle East & Africa Edition | 3/2021 Inspired by the Maya—skull and tooth reconstruction with 3D printing By Yassine Harichane, France From time immemorial, people have attempted to transcribe their knowledge. Whether on stone, paper or wood—the various civilisations of our world have employed differ- ent media to share their culture. The Mayan civilisation was no exception. A Mayan codex is an encyclopaedia that includes the knowledge and capabilities of this ancient culture, including even dentistry. The fol- lowing scientifi c article presents the reproduction of Mayan teeth using 3D printing and various composites. A Mayan codex in the form of a con- certina folding book presents and contains glyphs and representations that together tell a story. This glob- ally unique story deals with their beliefs, practices and rites, but also their sciences. As a matter of fact, Mayan civilisation had a command of architecture, medicine, pharma- cology and even dentistry. Unfortu- nately, this knowledge went up in fl ames with the conquistadors. The Mayan codices were held to be sacri- legious, for which the only means of purifi cation was fi re. Consequently, the priests burnt the Mayan records. Today, only three Mayan codices survive; however, two of them are in such poor condition that they cannot be handled. The third Mayan codex, which is regarded as the most beautiful and best preserved, is in safekeeping at the Technische Uni- versität Dresden in Germany. Chichén Itzá is a Mayan city, famous today for its archaeological sites, including the Temple of Kukulcán. What many tourists do not know is that the Dresden Codex is also from this Mayan city. This codex, however, only contains information relating to the Mayan calendar. It makes no mention of sciences such as den- tistry. However, we possess artefacts that document that the Mayans per- formed dental treatment not only for therapeutic but also for aesthetic purposes. There is currently no way of bringing back from the ashes a Mayan codex burnt 500 years ago, but we do have the technology to reconstruct 1,500-year-old artefacts. In this article, we will show how we managed to reproduce Mayan teeth using digital tools. Mayan skulls Surprisingly, the Maya already prac- tised craniofacial orthopaedics in their day. When we look at the skel- etons today, we can determine that these people had a particular profi le. The skull was elongated and lengthy, the forehead receding and the bridge of the nose even with the forehead until it reached the crown of the head. These craniofacial criteria were the result of a ritual practice: women applied rigid plates to the heads of their children that were bound to- gether in order to steer craniofacial growth (Fig. 1). The Maya employed fontanelles, tissue areas between the skull bones, to shape the heads of their young children. The result was a fl attened skull in the forehead and occipital bone, as well as an overall egg-like shape. This arbitrary deformation was not performed for therapeutic reasons, but rather for aesthetic purposes. It was a cultural practice that permitted the ethnic and social group of the individual to be identifi ed. 3D-printed Mayan skull We attempted to synthesise a Ma- yan skull with the latest technology. To do so, we took three main steps: data acquisition, design and print- ing. The acquisition step consisted of using data acquired by cone beam Temple of Kukulcán computed tomography (i-CAT, KaVo Kerr). We worked on a scan from our database, for which the patient gave his consent. The result was a DICOM fi le that included all the informa- tion on tissue density (Fig. 2). Conse- quently, it was possible to practically remove all the soft tissue, just leav- ing mineralised tissue, such as bones and teeth (Fig. 3). We isolated the skull of the patient and exported it to an STL fi le. The design step included importing the STL fi le into 3D-modelling software in order to distort the skull virtu- ally. The frontal bone was fl attened, ensuring that the nose tip was in contact with the crown of the head. The occipital bone was less curved, in order to simulate the effect of a rigid plate behind the head. Finally, the skull was modifi ed to give it an over- all egg shape. This resulted in a skull that met the canons of Mayan beau- ty (Fig. 4). The digital fi le was sent to a 3D printer (SolFlex 650, VOCO; Fig.5) loaded with transparent resin (V- Print splint, VOCO; Fig. 6), to refl ect the internal bone structures better. This produced a transparent skull with fi ne details and a global shape (Fig. 7), which resembles the Mayan skulls on display in museums. Mayan smiles Mayan skeletons have been closely examined by multidisciplinary teams of anthropologists as well as by dentists. The teeth do in fact re- veal special modifi cations: they are fi led, striated or studded with pre- cious stones (Fig. 8). The changes in shape may include the incisal edges, the vestibular surface, and the me- sial and distal angles of the teeth. The inlays are composed of various stones: jade, obsidian, serpentinite, haematite, etc. However, one should bear in mind that these changes were confi ned to the smile, that is, chiefl y the anterior teeth and normally the Fig. 1: A Mayan child with growth plates. Fig. 2: Facial reconstruction. Fig. 3: Reconstruction of the skull. Fig. 4: Virtual Mayan skull. Fig. 6: V-Print splint (VOCO). buccal surfaces of the teeth. These operations were performed for aes- thetic purposes. The teeth were both a symbol of social identity as well as an adornment. The most surpris- ing thing is that these interventions were performed with such mastery that, for example, 1,500 years later, the teeth and even inlays still exist. Consequently, these artefacts are the ultimate proof that a dental in- tervention can be both cosmetic and permanent. Mayan wax-up We were able to reproduce three ar- tefacts of the Mayan smile with the technological tools currently at our disposal. The previous steps, acqui- sition, design and 3D printing, were used in order to digitally produce a wax-up and two mock-ups. The fi rst step required the use of an intra-oral scanner (CEREC Omnicam, Dentsply Sirona; Fig. 9). The maxillary arch of a patient was scanned down to the tiniest detail in order to produce the most realistic artefacts possible. The scan was exported as an STL fi le to facilitate easy processing by the soft- ware. In a second step, a plannable basis was created for the 3D printing of a dental model, using modelling software (Fig. 10). This was printed directly in 3D (SolFlex 170 and V- Print model, VOCO; Fig. 11) in order to preserve the patient’s dental arch (Fig. 12). To optimise the light poly- merisation, the model was placed in an ultraviolet fl ash- light device (OtoFlash, VOCO; Fig. 13). The wax- up was inspired by Mayan smiles. The shape of the anterior teeth was modifi ed to meet Mayan aesthetic criteria. The incisal edges were fi led, and a step applied to the central in- cisors. The teeth were coated with fl owable composite (Admira Fusion Flow, VOCO) in Shade A3.5 for the molars, Shade A3 for the premolars, Shade A2 for the canines and Shade A1 for the incisors. Effect compos- ite (Final-Touch, VOCO) was used to achieve a realistic reproduction. The brown composite was introduced into the grooves, and the orange into the embrasures. Inlay work was per- formed with green and blue compos- ite (Twinky Star, VOCO) on the buccal surfaces of the teeth in order to sim- ulate precious stones, and fi nally, the gingivae were simulated using pink composite (Amaris Gingiva, VOCO). The fi nal result was a realistic Mayan dental arch, produced 50% digitally and 50% manually (Fig. 14). Mayan mock-up Reproducing a wax-up in the mouth is possible using a mock-up. To do so, we implemented two different work- fl ows. The fi rst workfl ow involved acquiring the dental arch using an intra-oral scanner (TRIOS MOVE, 3Shape; Fig. 15). The STL fi le was sent to a dental technician, who devel- oped a digital wax-up. This wax-up was produced according to the cri- teria of Mayan aesthetics: a mesial cut on the central incisors, an incisal reduction on the lateral incisors and dental jewellery from canine to ca- nine (Fig. 16). The digital wax-up was converted to an STL fi le, which was printed in 3D using a special printer (SolFlex 170 and V-Print model; Fig. 17). A silicone key was produced from the 3D-printed model (V-Posil Putty Fast and V-Posil X-Light Fast, VOCO; Fig. 18). Fig. 5: SolFlex 650 (VOCO). Fig. 7: Mayan skull printed in 3D. ÿPage D3