<strong>Aim: </strong>To compare the type of stress distribution pattern occurring with anatomic and non-anatomic tooth forms beneath a complete denture in both maxillary and mandibular arch. <strong>...<strong>Aim: </strong>To compare the type of stress distribution pattern occurring with anatomic and non-anatomic tooth forms beneath a complete denture in both maxillary and mandibular arch. <strong>Methodology: </strong>A photoelastic model of the edentulous maxillary and mandibular ridge was prepared meticulously to simulate the human mandible and maxilla. Two sets of acrylic teeth with anatomic and non-anatomic occlusal forms were used to fabricate upper and lower dentures. A vertical static load of 100 N was applied through the mandibular model to the maxillary model. After load application on the dentures the photoelastic model as well as the upper and lower complete dentures were sectioned in the midline. The sectioned photoelastic model was viewed through a polariscope to observe the fringe pattern indicating varying amounts of stress distribution. In this study, a two-dimensional photoelastic stress analysis technique was utilized. <strong>Results:</strong> Force per unit area was observed more in anatomic teeth than the non-anatomic counterpart. Hence anatomic tooth forms may increase the possibility of bone resorption rate over a period of time. However, in non-anatomic lower teeth, a decrease in value was observed from posterior to anterior region. <strong>Conclusion: </strong>Stress of greater magnitude was observed with cuspal teeth whereas non-anatomic (0<span style="white-space:nowrap;">°</span>) showed slightly less magnitude of stress. Depending upon the clinical situation the clinician needs to choose the type of occlusal tooth forms for edentulous patients.展开更多
The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur inv...The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur involute pinion were introduced, and their relative errors are below 10%, except edge contact, which turns out that these two methods can compute contact stress of face-gear drive correctly and effectively. An agreement of the localized bearing contact stress is gotten for these two methods, making sure that the calculation results of FEM are reliable. The loaded meshing simulations of multi-tooth FEM model were developed, and the determination of the transmission error and the maximal load distribution factor of face-gear drive under torques were given. A formula for the maximal load distribution factor was proposed. By introducing the maximal load distribution factor in multi-tooth contact zone, a method for calculating the maximal contact stress in multi-tooth contact can be given. Compared to FEM, the results of these formulae are proved to be reliable, and the relative errors are below 10%.展开更多
This study highlights the joint effect of early polymerization shrinkage and long-term moisture diffusion on the behavior of the restoration-tooth structure. The interphase debonding between particle and polymer resin...This study highlights the joint effect of early polymerization shrinkage and long-term moisture diffusion on the behavior of the restoration-tooth structure. The interphase debonding between particle and polymer resin in dental composite is taken into account by introducing the damage variable. The idealized model is designed and constructed for representing the restorationtooth structure, which consists of enamel, dentin, composite and interphase, each considered as homogenous material. The simulation is carried out using the general-purpose finite element software package, ABAQUS incorporated with a user subroutine for definition of damaged material behavior. The influence of Young's moduli of composite and interphase on stress and displacement is discussed. The compensating effect of water sorption on the polymerization shrinkage is examined with and without involving damage evolution. A comparison is made between the influence of hyper-, equi- and hypo-water sorption. Interfacial failure in the specific regions as well as cuspal movement has been predicated. The damage evolving in dental composite reduces the rigidity of composite, thus in turn reducing consequent stress and increasing consequent displacement. The development of stresses at the restoration-tooth interface can have a detrimental effect on the longevity of a restoration.展开更多
文摘<strong>Aim: </strong>To compare the type of stress distribution pattern occurring with anatomic and non-anatomic tooth forms beneath a complete denture in both maxillary and mandibular arch. <strong>Methodology: </strong>A photoelastic model of the edentulous maxillary and mandibular ridge was prepared meticulously to simulate the human mandible and maxilla. Two sets of acrylic teeth with anatomic and non-anatomic occlusal forms were used to fabricate upper and lower dentures. A vertical static load of 100 N was applied through the mandibular model to the maxillary model. After load application on the dentures the photoelastic model as well as the upper and lower complete dentures were sectioned in the midline. The sectioned photoelastic model was viewed through a polariscope to observe the fringe pattern indicating varying amounts of stress distribution. In this study, a two-dimensional photoelastic stress analysis technique was utilized. <strong>Results:</strong> Force per unit area was observed more in anatomic teeth than the non-anatomic counterpart. Hence anatomic tooth forms may increase the possibility of bone resorption rate over a period of time. However, in non-anatomic lower teeth, a decrease in value was observed from posterior to anterior region. <strong>Conclusion: </strong>Stress of greater magnitude was observed with cuspal teeth whereas non-anatomic (0<span style="white-space:nowrap;">°</span>) showed slightly less magnitude of stress. Depending upon the clinical situation the clinician needs to choose the type of occlusal tooth forms for edentulous patients.
基金Project(50875263) supported by the National Natural Science Foundation of ChinaProject(2011CB706800) supported by the National Basic Research Program of ChinaProject(2010ssxt172) supported by the Natural Science Foundation of Hunan Province,China
文摘The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur involute pinion were introduced, and their relative errors are below 10%, except edge contact, which turns out that these two methods can compute contact stress of face-gear drive correctly and effectively. An agreement of the localized bearing contact stress is gotten for these two methods, making sure that the calculation results of FEM are reliable. The loaded meshing simulations of multi-tooth FEM model were developed, and the determination of the transmission error and the maximal load distribution factor of face-gear drive under torques were given. A formula for the maximal load distribution factor was proposed. By introducing the maximal load distribution factor in multi-tooth contact zone, a method for calculating the maximal contact stress in multi-tooth contact can be given. Compared to FEM, the results of these formulae are proved to be reliable, and the relative errors are below 10%.
基金Project supported by the Research Grant Council of Hong Kong (No.PolyU5176/00E).
文摘This study highlights the joint effect of early polymerization shrinkage and long-term moisture diffusion on the behavior of the restoration-tooth structure. The interphase debonding between particle and polymer resin in dental composite is taken into account by introducing the damage variable. The idealized model is designed and constructed for representing the restorationtooth structure, which consists of enamel, dentin, composite and interphase, each considered as homogenous material. The simulation is carried out using the general-purpose finite element software package, ABAQUS incorporated with a user subroutine for definition of damaged material behavior. The influence of Young's moduli of composite and interphase on stress and displacement is discussed. The compensating effect of water sorption on the polymerization shrinkage is examined with and without involving damage evolution. A comparison is made between the influence of hyper-, equi- and hypo-water sorption. Interfacial failure in the specific regions as well as cuspal movement has been predicated. The damage evolving in dental composite reduces the rigidity of composite, thus in turn reducing consequent stress and increasing consequent displacement. The development of stresses at the restoration-tooth interface can have a detrimental effect on the longevity of a restoration.
