Characterization of non‑linear mechanical behavior of the cornea

The objective of this study was to evaluate which hyperelastic model could best describe the nonlinear mechanical behavior of the cornea, in order to characterize the capability of the non-linear model parameters to discriminate structural changes in a damaged cornea. Porcine corneas were used, establishing two diferent groups: control (non-treated) and NaOH-treated (damaged) corneas (n= 8). NaOH causes a chemical burn to the corneal tissue, simulating a disease associated to structural damage of the stromal layer. Quasi-static uniaxial tensile tests were performed in nasaltemporal direction immediately after preparing corneal strips from the two groups. Three non-linear hyperelastic models (i.e. Hamilton-Zabolotskaya model, Ogden model and Mooney-Rivlin model) were ftted to the stress–strain curves obtained in the tensile tests and statistically compared. The corneas from the two groups showed a non-linear mechanical behavior that was best described by the Hamilton-Zabolotskaya model, obtaining the highest coefcient of determination (R2 > 0.95). Moreover, Hamilton-Zabolotskaya model showed the highest discriminative capability of the nonlinear model parameter (Parameter A) for the tissue structural changes between the two sample groups (p= 0.0005). The present work determines the best hyperelastic model with the highest discriminative capability in description of the non-linear mechanical behavior of the cornea.Ministry of Education DPI2017-83859-R DPI2014-51870-R EQC2018004508-P UNGR15-CE-3664Ministry of Health - Turkey DTS15/00093Junta de Andalucia PI16/00339 PI-0107-2017 PIN-0030-201

Study of the Internal Anatomy of the Mandibular Incisor Teeth

Statement of Problem: Knowledge of internal anatomy of tooth plays an important role in a successful endodontics treatment. For a proper endodontic treatment, it is not only important to know the form of normal anatomy of tooth’s interior but one must also beacquainted with the possible diverse forms.Purpose: A thorough understanding of the internal anatomy of human mandibular incisors (central and lateral).Materials and Methods : A total of 205 central and lateral mandibular incisors that had healthy roots were selected and put in 10% formalin solution. After cleaning the samples with the help of brushes and other devices, they were kept in 5% sodium hypochloritesolution. Finally the roots were cleaned and the samples were prepared for next stages.Three methods were used, coloring (fushin1%, radiography (buccolingual and proximal sides), and cross-sectioning (cervical- middle-apical).Results: The result indicated that:- 88%of the teeth had a single canal and one apical foramen;- 8% of the teeth had a single canal and two apical foramena;- 3.5% of the teeth had two canals and one apical foramen;- 0.5% of the teeth had two canals and two apical foramena;Conclusion:A thorough understanding of the pulp morphology is essential for successful treatment of root canal. Therefore, a dentist should always be on the watch for the existence of two canals or a two-branched canal while working on the mandibular incisor teeth. it is essential to have the necessary precision in finding the second canal