The site of Riparo Mezzena in northern Italy is located at 250 meters a.s.l, along a Middle Eocene limestone cliff on the northern side of the Avesa Valley, next to the city of Verona. The site, named after its discoverer, Franco Mezzena, was excavated by the Natural History Museum of Verona in the summer of 1957 under the direction of F. Zorzi and A. Pasa. During these excavations a series of layers of variable thickness were exposed, ranging between 1.5 and 1.7 meters, and at least three anthropogenic layers were identified (top-bottom: layers I, II and III). All the human remains (probably two individuals) were found in layer Ib. Results from the pedological, sedimentological and palynological analyses suggest the presence of a cold, continental climate associated with layer III, followed by a wet interval corresponding to the limestone surface between layers III and II. Layers I and II were marked by a continental climate, characterized by dry and cold phases (in correspondence with loess sediments) as well as humid phases (corresponding to concretions) (Bartolomei et al., 1980). All of these elements suggest that the Mezzena site was inhabited during a Late Mousterian phase.

The lithic industry has recently been the topic of a new study aiming to understand the interaction between humans and their environment (Giunti and Longo, 2010, Longo and Giunti, 2007, Longo et al., 2011 and Thun Hohenstein et al., 2011). It has been linked to human groups that frequented the site at different times, using it as a residential site, although for relatively brief periods. The Levallois technology is documented both by recurrent centripetal and by the preferential methods. Predetermined blanks are of medium-small dimensions. Scrapers are numerous, with quite a few Charentian elements. Mousterian points are also present. Raw materials consist primarily of flint originating from the formations of Maiolica (Scaglia Variegata and Eocene Limestone), which are located 5–15 km from the site (Longo and Giunti, 2007 and Longo and Giunti, 2010).

This type of osteolytic lesion in the Neanderthal mandible of Mezzena corresponds to a benign bone tumor of dental origin (Langsjoen et al., 1998) or to an abscess. Benign cysts and tumors of the mandible are most often odontogenic, meaning that they originate from tissue related to the teeth. The osteolytic lesion developed from the second right premolar, as shown from the corresponding residual tooth apex and the direction of its intra-osseous trajectory. Moreover, the high position of the apex, probably undergoing eviction, and the bone apposition between this radicular debris and the lesion seem to illustrate a healing process. An interesting parallel may be established with a lesion found on a present-day patient, also situated in the middle of the mandibular corpus, mesio-distally between the distal face of the right second premolar and the mesial face of the second mandibular molar. It presents identical characteristics in terms of form and size: an oval shape measuring 8 × 8.5 × 9.5 mm. A 3D-model (software MIMICS 10.01^®) of this lesion allows us to evaluate its volume: 687 mm³. Its surgical removal confirmed these data (see supplementary on line material, Fig. S5). From an etiological point of view, this lesion, without clinical signs, was an accidental discovery. The anamnesis and clinical examination revealed the origin of this pathology: a chronic intra-osseous bacterial infiltration developed from a cavity and the fracture of the second right mandibular premolar, leading to this periapical lesion. The analogies observed between a lesion described on a current patient and the Neanderthal fossil of Mezzena support the hypothesis of a similar etiopathogenesis and positive diagnosis: an irritated periapical lesion with endodontic origin. In the Mezzena Neanderthal fossil, the neo-apposition of the healing bone around the lesion and the position of the radicular debris in eviction attest the fact that this pathology occurred a long time before death and was not its cause. The presence of multiple dental loss ante-mortem leads to the conclusion that, over the course of its life, the Mezzena Neanderthal suffered from several acute dental pathologies similar to the present-day patient.

The Mezzena jaw belongs to the Neanderthals that inhabited a vast geographical area during the Middle and Late Pleistocene, extending from all over Europe to the Middle East, western Asia and southern Siberia. The Mezzena mandible presents an odontogenic osteolytic lesion that led to extensive destruction and pathological bone remodeling in the vicinity of the right premolars and first molar teeth. This lesion is evidenced by the fistulian intra-osseous path and is certainly the result of an infection developed in the premolar.

Regarding the cause of this pathology, we note that the residual root fragment is situated close to the alveolar rim and is probably in the process of eviction. This observation makes it possible to exclude the hypothesis of bacterial proliferation around the dental root originating from a periodontal trauma, which would have been illustrated in the X-ray image by a “glove finger-shape” osseous loss. Thus, the bacterial invasion that induced this osteolytic lesion was probably exclusively of endodontal origin. This hypothesis is corroborated by the complete exposure of the tooth pulp to bacteria due to absence of the tooth crown.

Because a great number of teeth are absent and were missing ante-mortem on the Neanderthal Mezzena mandible (see supplementary online material Figs. 2 and 3), it may be that other teeth underwent a similar process. It is clear that this extensive tooth loss had consequences for the quality of life of the Mezzena Neanderthal. It is nonetheless difficult to determine whether this individual required conspecific care for its survival, as has been claimed for fossils with a similar pathology (Lebel et al., 2001) or not (De Gusta, 2002).

It is interesting to note that the Mezzena mandible shows an oral pathology that is frequently observed among both Neanderthals and hunter-gatherer human populations (Tropel, 2004 and Webb, 1995). Indeed, the Italian Neanderthals from Grotta Guattari lost all their maxillary teeth ante-mortem. Abscesses are also known among Neanderthal fossils such as Forbes’ Quarry (Gibraltar) (Iberian peninsula) and Arcy-sur-Cure 9, La Chapelle-aux-Saints 1 and La Ferrassie 1 (France). The Neanderthal of La Chapelle-aux-Saints (France) shows a marked pathological dental condition on its maxilla and mandible (Tappen, 1985). On the mandible only the anterior teeth were present at the time of death and this fossil displays extensive destruction and pathological remodeling of bone similar to that observed in the Mezzena example (Tappen, 1985).

At present, there is no clear etiological diagnosis for the causes of the pulp exposure in the Mezzena mandible. This exposure may have resulted from a traumatic fracture, from a cavity, or from extensive wear on the tooth. All these causes are documented in Neanderthals.

Indeed, traumatic breaks have been observed on fossil teeth and are found on at least two French Neanderthals: Arcy 9 and La Quina 5. For a long time, no cavities were recognized in Pleistocene populations and it is only during the last two decades that cavities have been observed in Neanderthals. Thus, two cavities have been described on two Neanderthal teeth from the same French site (Bau d’Aubesier) (Lebel and Trinkaus, 2000 and Trinkaus et al., 2002) and from a Spanish site of Sima de las Palomas and Banyoles (Walker et al., 2011). This may be supplemented by the cavity found in the Levantine Neanderthal from Kebara (Tillier, 1991). In human fossils the only case of polycavities that has been discovered is in the Zambian fossil of Kabwe (Carter, 1928). For this reason, we cannot exclude the possibility that the pathology of the Mezzena specimen was due to a cavity, although we recognize that multiple extensive abrasions are more frequent among Pleistocene humans and, in particular, among Neanderthals. For example, among European Neanderthals they can be found in La Ferrassie 1, Bau d’Aubesier, L’Hortus (France), Banyolas 1 and Gibraltar 1 (Iberian peninsula), as well as among Levantine and eastern Neanderthals (Amud 1 in Israel; Shanidar 1, 3, 4 and 5 in Iraq).

In view of the extensive wear found in particular on Neanderthal teeth and, more generally, on those of hunter-gatherer populations, it would be tempting to support the hypothesis that the loss of the premolar crown on the mandible of Mezzena was most probably caused by dental abrasion.

The mandible of a Neanderthal from the Middle Paleolithic site of the Riparo Mezzena presents an osteolytic odontogenetic lesion. This pathology was revealed through X-ray and computerized-tomodensitometric examinations. Similar lesions have been observed among present and sub-contemporary populations and indicate that the lesion of the Mezzena specimen may have been of infectious origin, resulting from a bacterial invasion of the root canal due to coronal pulp exposure. There is no clear etiological diagnosis concerning the causes of the pulp exposition in the Mezzena mandible. Available data known for Pleistocene fossils and, in particular, for Neanderthals, indicate that the etiology of the pulp exposure in the Mezzena Neanderthal mandible may have been due to breakage of the tooth, to a cavity, or to extensive wear.