: Photoelastic and finite element stress analysis study of various human teeth

number: 
3100
English
Degree: 
Author: 
Noora Abdul Razak Abdul Hussain
Supervisor: 
Dr. Sadiq J. Abass
Dr. Jamal A. Hassan
year: 
2013
Abstract:

In this study, both the experimental photoelastic, as well as the numerical finite element methods, have been used to analyze the stress within various human teeth (mandibular first molar, mandibular central incisor and maxillary central incisor) under forces similar to those that usually occur during chewing. Two-dimensional models of teeth were created by the software AutoCAD using Wheeler’s dental anatomy text book. The coordinates obtained from the Wheeler’s data were fed into a computer numerical control (CNC) machine to fabricate the models from photoelastic birefringent (polycarbonate) sheet. Final models were placed in a transmission polariscope and loaded with static forces (35N, 44N and 55N) at 0° and 45° to the tooth axis. Stresses can be quantified and localized by counting the number of fringes. The principal stresses were calculated at different regions, the crown, the cervical and the root. It was found that when the tooth is subjected to the vertical loads, the higher stress on mandibular first molar concentrated at the cervical region reaching 3.4 MPa and lower stresses at crown and root reaching to 2.720 MPa and 2.04MPa sequentially. The stress on maxillary central incisor concentrated at crown region reaching 5.44MPa and lower stresses at cervical and root reaching to 2.72MPa and 2.04MPa sequentially. The stresses on mandibular central incisor concentrated at cervical region reaching to 4.08 MPa and lower stresses at crown and root reaching 3.4MPa and 2.04MPa sequentially. The change of the force angulation (45° to the long axis) increased the level of stresses drastically in all teeth models. The highest stresses on mandibular first molar located at the cervical region reaching to 13.6 MPa and lower stresses at crown and root reaching to 10.88MPa, 8.16MPa. In the maxillary central incisor the highest stresses located at cervical reaching to11.08 MPa and lower stresses at crown and root region, reaching to 10.88 MPa and 8.421MPa sequentially. In the mandibular central incisor the highest stresses located at cervical reaching to 16.232MPa and lower stresses at crown and root reaching to, 13.5MPa and 8.16MPa sequentially. The numerical FE results showed reasonable agreement with the experimental photoelastic results.