Numerical simulation of hydro-mechanical coupling of periodontal ligament.

Orthodontic tooth movement in the alveolar bone is due to the mechanical response of periodontal ligament to applied forces. Definition of a proper constitutive model of the periodontal ligament to investigate its response to orthodontic loading is required. For this purpose, a three-dimensional finite element model of incisor tooth, periodontal ligament, and bone was built utilizing the hydro-mechanical coupling theory. Tooth displacement in response to orthodontic loading was then investigated, and the effect of different mechanical behaviors assigned to the solid phase of the periodontal ligament was compared. Results showed that where the periodontal ligament was placed in tension, pore volume was filled with fluid intake from the bone, but fluid flow direction was from the periodontal ligament toward the bone where the periodontal ligament was placed in compression. Because of the existence of interaction between solid and fluid phases of the periodontal ligament, considering biphasic material formulation was capable to address its microscopic behavior as well as time-dependent and large deformation behaviors. This article provides beneficial biomechanical data for future dental studies in determination of optimal orthodontic force.

Thermal Analysis of Dental Implants in Mandibular Premolar Region: 3D FEM Study.

PURPOSE: The distribution of temperature in a dental implant following hot food and beverage consumption is essential for evaluating the hazard this process may have on bone health. The purpose of this study was to predict the temperature distribution in the dental implant with/without a crown and the bone crest in contact with it using the finite element method. MATERIALS AND METHODS: A 3D model of the implant and the mandible was prepared by using computer-aided design software. Implants were investigated in three cases: without crown (BHI), with ceramic crown (MHIc), and with zirconia crown (MHIz). Subsequently, temperature distribution was numerically determined along the implant system for two heat loadings. RESULTS: In loading type I, the maximum temperature of the surrounding bone at the cervical implant/bone interface was obtained in the BHI model (39.1°C), and the lowest was obtained in the MHIc model (37.6°C). The maximum temperature rise in loading type II also took place in the BHI model (41.7°C). Moreover, the BHI model showed a rapid rise to the maximum temperature followed by a fast recovery compared to its two counterparts (MHIc, MHIz). In both loading types, the maximum temperature at the first point of contact between the implant and bone, and apical implant/bone interface was slightly higher in the MHIz than that in the MHIc. The maximum temperature in all the models was higher when subjected to cyclic loading. The maximum temperatures reached in all the models were lower than threshold temperatures, so thermal loading alone does not harm the jawbone. Moreover, the BHI was more vulnerable than the MHIc and the MHIz. CONCLUSIONS: The results of this study suggest that dental implants should be covered with crowns as soon as possible, and patients with dental implants should avoid consumption of hot food and beverages without allowing time for the heat to dissipate.