Structure-function relations of primate lower incisors: a study of the deformation of Macaca mulatta dentition using electronic speckle pattern interferometry (ESPI)

Abstract

Teeth adopt a variety of different morphologies, each of which is presumably optimized for performing specific functions during feeding. It is generally agreed that the enamel cap is a crucial element in controlling the mechanical behavior of mammalian teeth under load. Incisors are particularly interesting in terms of structure-function relations, as their role in feeding is that of the 'first bite'. However, little is known how incisor cap morphology is related to tooth deformation. In the present paper we examine the mechanical behavior of mandibular central incisors in the cercopithecine primate Macaca mulatta under loads similar to those encountered during ingestion. We map three-dimensional displacements on the labial surface of the crown as it is compressed, using electronic speckle pattern interferometry (ESPI), an optical metrology method. In addition, micro-computed tomography is used to obtain data regarding the morphology of the enamel cap, which in the M. mulatta lower incisors exhibits missing or very little enamel on the lingual face. The results showed that although compressed along a longitudinal axis, deformation in the incisors mostly occurred in the lingual direction and orthogonal to the direction of the applied load. Both isolated, embedded teeth and teeth in the mandible showed considerable lingual deformation. Incisor deformation in the mandible was generally greater, reflecting the additional freedom of movement enabled by the supporting structures. We show that the association with adjacent teeth in the arch is significant for the behavior of the tooth under load. Finally, loading two teeth simultaneously in the mandible showed that they work as one functional unit. We suggest that these results demonstrate the importance of enamel cap morphology in directing deformation behavior; an ability stemming from the stiffness of the enamel cap overlying the more pliable dentin.

Tooth movements are guided by specific contact areas between the tooth root and the jaw bone: A dynamic 3D microCT study of the rat molar

“…The studies by Chattah et al on macaque incisor (Chattah et al, 2011) and the M1 tooth of the mini-pig (Chattah et al, 2009) are of particular relevance to this study as these include observations of the movements of the crowns of these teeth under load while still in the mandible. The responses of these two teeth are very different from each other.…”

“…Previous studies conducted on extracted human premolar teeth (Zaslansky et al, 2006b), primate incisors (Chattah et al, 2011) and minipig molars (Chattah et al, 2009) showed that each tooth type has its own unique response to load. The studies by Chattah et al on macaque incisor (Chattah et al, 2011) and the M1 tooth of the mini-pig (Chattah et al, 2009) are of particular relevance to this study as these include observations of the movements of the crowns of these teeth under load while still in the mandible.…”

“…1 for orientation) (Chattah et al, 2009). The structures responsible for these complex movements reside mainly in the interactions between the tooth roots, the PDL and the alveolar bone and, to a limited extent, the internal structure of the tooth (Chattah et al, 2009(Chattah et al, , 2011. To date, no study has directly visualized the movement of the entire toothroots system in relation to the PDL and alveolar bone.…”

“…These studies showed that the movement of the incisors of a macaque monkey resembles a loaded cantilever (Chattah et al, 2011), whereas the movement of a mini-pig molar resembles a ''seesaw'' that also tilts slightly towards the oral cavity (lingual direction, refer to Fig. 1 for orientation) (Chattah et al, 2009).…”

Full-field optical deformation measurement in biomechanics: Digital speckle pattern interferometry and 3D digital image correlation applied to bird beaks

“…Recently, DSPI has been introduced in biomechanics. Some examples are found in literature, including the displacement of the tympanic membrane (Del Socorro Herná ndez-Montes et al, 2009), the strains on human and macaque tooth (Zaslansky et al, 2005(Zaslansky et al, , 2006Barak et al, 2009aBarak et al, , 2009bChattah et al, 2011) on human bones (Barak et al, 2009a(Barak et al, , 2009b, the mouse femur (Yang et al, 2007), the ovine callus (Bottlang et al, 2008), the human mandible (Grö ning et al, 2009) and zygomatic arch of the pig (Bright and Grö ning, 2012).…”