Relations Between Shape, Materials Properties, and Function in Biological Materials Using Laser Speckle Interferometry: In situ Tooth Deformation

Abstract

The manner in which stiff biological objects, such as whole bones and teeth, deform under load can provide direct insight into their in vivo functions, while highlighting the relations between their structure and materials properties. A new approach for studying the mechanical functions of such objects, using as an example the crowns of human teeth, is developed. Tooth‐crown deformation under a compressive load is determined in water using laser speckle interferometry. The deformation patterns are analyzed using a novel procedure that reveals the relative magnitudes of 3D displacements of the outer surface. Nanometer‐scale deformations of natural teeth were compared to deformations of identical acrylic replicas, in order to differentiate between contributions of the structure–material properties from contributions of morphology. It is shown that human premolars deform in a manner that is largely controlled by shape; in natural teeth, the enamel cap appears to displace mainly as a rigid body, undergoing moderate deformation. These observations contribute to the understanding of whole‐tooth performance under load. The approach for analyzing the deformation of loaded whole objects is directly applicable to the study of many stiff biological specimens, including comparisons between normal and altered (repaired or genetically modified) bones.

Design Strategy of Minipig Molars Using Electronic Speckle Pattern Interferometry: Comparison of Deformation under Load between the Tooth‐Mandible Complex and the Isolated Tooth

“…Another interesting finding of this study was that the enamel cap of minipigs is capable of deforming and rotating at loads as low as 16 N. This finding is very different from that of Zaslansky et al, [27] who showed that the enamel cap of an isolated human premolar did not deform or rotate at loads lower than 80 N. This is most likely related to differences in the structure, mineral content and morphology of the respective enamels. Previous studies comparing human and pig molar crowns have shown that despite overall similarities in morphology, development and function, human teeth have a different enamel microstructure as well as a stiffer, thicker and less complex enamel cap compared to the pig.…”

“…More recently electronic speckle pattern interferometry (ESPI) has been adapted to the study of whole-tooth mechanical behavior under load, while the tooth is submerged in water. [27] ESPI is a noncontact, nondestructive method that is capable of mapping three-dimensional, nanometer-scale whole surface displacements on an irregular object. The ESPI method is able to detect deformation and rotation but is insensitive to whole body translation.…”

“…The ESPI method is able to detect deformation and rotation but is insensitive to whole body translation. [27][28][29] Zaslansky et al [27] used ESPI to map displacement patterns of human premolar crowns when loaded on the buccal cusp. The results showed that the enamel cap basically behaves as a stiff body that is capable of deforming and rotating only under relatively high loads.…”

“…The use of these opposing strategies to achieve the same ends has been attributed to phylogenetic differences in masticatory function. [16,36] Finally, in their study Zaslansky et al [27] emphasized the importance of gross enamel cap morphology on the behavior of premolars under load by comparing human premolars to replicas made of a homogeneous material. They observed similarities in the ways in which the tooth and the replicas deformed, highlighting the fact that crown morphology is as important as structure.…”

Analysis of the compressive strain below the removable and fixed prosthesis in the posterior mandible using a digital image correlation method

“…Although the maximal willing force in humans measured in the posterior region is 500-700 N, it was considered that the force intensity decreases with the teeth loos and depends of muscular strength (Muller et al 2001). The force was applied to the buccal and lingual cusps of loading teeth in both models, across the horizontal extention of the gnatodynamometer (Qian et al 2009;Zaslansky et al 2006). Gnatodynamometer was used for the purpose of precise and controlled force (load) measuring.…”