Occlusal Fingerprint Analysis ( OFA ) reveals dental occlusal behavior in primate molars

A comprehensive understanding of the occlusal relationship between upper and lower tooth crowns in mammals is essential to interpret the evolution of dental function and adaptations. In fossil species, we can only hypothesize occlusal dynamics based on the analysis of tooth structures, the interpretation of dental macroand microwear patterns, and the reconstruction of jaw mechanics. We are not able to test and comparably render in vivo details of the chewing physiology and other dental behaviour. Dental wear patterns are the result of the biomechanical interplay between dental hard tissue, ingested food, incorporated environmental grit, and chemical processes induced by saliva and food itself (Lussi 2002). In this respect it is well known that wear patterns can inform about properties of ingested food materials, and aspects of general environmental setup, such as dust present in the air and adhered to food (Baker et al. 1959, Ungar et al. 1995, Sanson et al. 2007, Lucas et al. 2013). A detailed analysis of dental wear patterns provides evidence about masticatory and para-masticatory occlusal dynamics, based on the upper and lower antagonistic tooth relation during occlusal movements (Butler 1952, Mills 1955). This is of particular interest for the extraction of dietary and behavioural signals encoded in the macro-relief morphology of worn dental surfaces. Since the early 1970s detailed conclusions were drawn from analyses of food composition in the context of macroand microwear on surfaces of dental crowns (e. g., Crompton & Hiiemäe 1970, Crompton 1971, Butler 1973, Kay 1973, 1975, 1981, Kay & Hiiemäe 1974a,b, Janis 1979, 1984, 1990, Smith 1984). Numerous studies confirmed a distinct correspondence between dental biomechanics, occlusal movements and crown relief structures (M’Kirera & Ungar 2003, Maier 1977a,b, 1978, 1980, Maier & Schneck 1981, 1982, Strait 1993a,b, Teaford 1983, Ungar & Williamson 2000, Ungar & M’Kirera 2003, Ulhaas et al. 2004, 2007). Biologically, the dentition represents an organismic functional unit for the ingestion and disintegration of food, biomechanically adapted to various food materials (Lucas 2004). Mechanical processes during chewing and other behavioural activities on the tooth surface lead to crown abrasion and attrition (Kay & Hiiemäe 1974a). Consequently, pits and scratches (microwear) emerge on the crown surface, evidencing the loss of hard tissue (enamel/ dentin) due to mechanical stress. The morphogenetic crown relief (primary relief) in a freshly erupted occluding crown is permanently altered (secondary relief) throughout the lifetime of an individual. Physical strain combined with saliva and food-induced chemical erosion results in gradual loss of dental structures on upper and lower crowns in respect to the pattern of sequential antagonistic approaches for the duration of power stroke movements (Fig. 2.1). Tooth-totooth contacts (dental two-body contacts) and tooth-food/ tooth-grit contacts (three-body contacts) (d’Incau et al. 2012) regulate overall mechanical dental wear activities, while the morphology of the antagonistic occlusal surface permanently adapts to individual occlusal dynamics. The contacts occur as integrative effects during repeated dental antagonistic intercuspation, resulting in a recurring precise Occlusal Fingerprint Analysis (OFA) reveals dental occlusal behavior in primate molars