Dental twinning in the primary dentition: three new archaeological cases from Italy

Dental twinning (or "double teeth") is a rare developmental condition that implies the fusion of two or more adjacent teeth. Clinical literature reports individual cases and extensive population studies to clarify causation, distribution, heritability and differential diagnosis of the different types of dental twinning (i.e. fusion, gemination, and accretion) whereas, documentation for past populations is still scarce. Aims: the present study documents four new archaeological cases of dental twinning of deciduous teeth from four different Italian archaeological sites and positions them within the framework of the known literature. Materials and methods: the observed cases include five deciduous teeth from four subadults from Sardinia (Monte Sirai, 7th-4th cent. BCE and Santa Filitica, 7th cent. CE), Campania (Velia, 1st-2nd cent. CE) and Latium (Villamagna, 13th-15th cent. CE). The identification, descriptions and differential diagnoses of the anomalies were performed with the use of morphological analyses and, in one case, radiographic means. Results: all cases fall within the category of double teeth; each involving a different set of processes (gemination and dental fusion), teeth (deciduous central incisors, lateral incisors and canines), locations (upper and lower) and occurrence (unilateral and bilateral). Conclusion: to this day, cases reported in literature of dental twinning in archaeological samples are sparse and limited to specific geographical areas. This study adds four more cases from Italy suggesting such anomalies should be recorded in dental analyses in order to, one day, obtain a more reliable modelling of the frequencies and distributions in past populations.