The Research Of The Morphology And Biomechanics For The Bitemark In Porket Limb

Bitemark is one kind of imprint that is left on one objective by teeth and other oral parts when they act upon at the same time. Forensic odontology mainly studies bitemarks which are left on human body. Because of special and complex histology, anatomy, and biomechanics of human tissue, bitemarks on human body have many morphological characteristics.Previous study mostly concentrated on the skills of collecting proves and comparing methods to analyze. Few of them concerned the mechanism of bitemark diversity that make few elements are certained to identify bitemarks in cases. This research firstly is to analyze the parameters of front teeth and arc that are related to bitemarks. Secondly establishing the model of bitemarks on pocket limbs to study morphology and correlated mechanics of soft-tissue.In the first part of this experiment, 100 samples of teeth and arc models from healthy youth in Chengdu were collected. Using Overlay skill to scan models and computer to measure morphological parameters (including teeth and arc) of front teeth. Results showed that: As to the morphological parameters of front teeth and arc, there is no difference between male and female, but male's are bigger than female's. There is difference between mandibula's and maxilla's, and the latter is bigger than the former. Additionally, there is no difference between right and leftjaw's. Using PLS method to analyze mandibula and maxilla, establish regression model to forecast parameters accurately.In the second part primarily is to using universal load-testing machine and self-made prefabricate nob to press perpendicularly on pocket limb to establish bitemarks. In this experiment, with prefabricate nobs of incisor and canine to press by force of 100N, 200N, 300N separately, we observe the change of bitemarks on alive and dead porkets with time past. Results showed: Mostly the bitemarks of incisor present to be quadrangle and the one of canine be triangle. There is no difference between their disciplines of transformation except their shapes. With the development of pressure, the scope of damage aggrandizes. With the development of pressure, the scope of bruise aggrandizes with little change in 24h.In the third part, based on bitemark model, we analyze the stress-strain relationship of soft-tissue and change of extension and elasticity after biting. Results showed: When bitemarks form, with the development of stress, the strain of soft-tissue increases. But the speed of increasement will slow down when stress exceeds some extend. When bitemarks formed, the extension and elasticity of soft-tissue decrease with the pressure increased. When bitemarks formed, there is a distinguished linear relationship between the transformation of bitemark and elasticity of soft-tissue.The results of this experiment show that in the analysis, only more characteristics of bitemarks could let us judge it more accurately. PLS method is not only useful to analyze the models of teeth and arc but also to identify bitemarks. With time past and the mechanics of soft-tissue changed, the shape of bitemarks disappears. In that the depth and scope of bitemarks related to elasticity very closely.