Evaluation of The Optical and Mechanical Properties of The Human Mandible

Statement of the problem: It is important to understand the mechanical properties of the mandible that has nonhomogeneous structure.

Objective: The aim of this study is to determine the optical density, apparent density, modulus of elasticity and strength values of mandible in vitro and to evaluate their relations.

Materials & Methods: Specimens obtained from six cadaver human mandibles. The sample figure dimensions was set as 2.8 cm length, 1.2 cm width, 0.6 cm mid-section, 0.5 cm height. Optic density (OD) is evaluated with radiographs using an optic densitometer. Apparent density (AD) is determined by mercury overflow tests. Modulus of elasticity (E) and strength(S) is determined using strain gauges and mechanical press. Data evaluated with simple regression analyzes (SRA), multiple regression analyzes (MRA), fuzzy algorithm.

Results: Values were found to be 1.115-1.586 for OD, 1.08 g/cm³-1.46 g/cm³ for ADA, 0.6-16.5 GPa for E, and 4.74 MPa-23.93 MPa for S. Simple regression analyzes revealed reverse-geometric relationship between OD-AD, reverse-linear relationship between OD-S, and reverse-logarithmic relationship between OD-E. MRA results pointed to a reverse relation between S-E. Fuzzy model was found to have a higher prediction performance.

Conclusion: Mandible has a nonhomogeneous and anisotropic structure. Modulus of elasticity is controlled by many parameters such as the material porosity, physical density, mineral quality, and texture. By using fuzzy algorithm, more reliable results can be obtained particularly in making classifications involving uncertainty.