<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
It is well known that modern Aves Iack dentition,unlike their toothed ancestors ofthe Jurassic and cretaceous periods.However,in the chick oral cavity a rudiment forms thatresembles the lamina stage of the mammalian m...It is well known that modern Aves Iack dentition,unlike their toothed ancestors ofthe Jurassic and cretaceous periods.However,in the chick oral cavity a rudiment forms thatresembles the lamina stage of the mammalian molar tooth germ.We have previously addressedthe molecular basis for this secondary loss of tooth formation in Aves by analyzing in chíckembryos the status of molecular pathways known to regulate mouse tooth development.In thisstudy,we further examined the moiecular pathways involved in positioning the site of toothrudinent.Similar te the mouse tooth germ,Pax9 serves as a marker for the presumptive dentalmesenchyme in the chick prior to any morphological manifestation of odontogenesis.Therestricted Pax9 expression in the chick mandibular mesenchyme is positioned by the two signalsfrom overlying oral epitheltum.FGF8 induces Pax9 expression while BMP4 prevents thisinduction.Thus it appears that,similar to that in tnice,the positíon of tooth rudiment in chickembryo is determined by two different types of signaling molecules with antagonistic sctiyity.These results further demonstrate that the early signaling pathways involved in odontogenesisremain inducible in Aves.展开更多
The basic principle of equal base circle bevel gear (EBCBG) is illustrated simply Thetooth surface equation of EBCBG manufactured by end milling cutter with involute profile is de-rived. The tooth form error is analy...The basic principle of equal base circle bevel gear (EBCBG) is illustrated simply Thetooth surface equation of EBCBG manufactured by end milling cutter with involute profile is de-rived. The tooth form error is analyzed on the basis of spherical involute展开更多
Form milling cutter is built-for-purpose cutter which process the form surface, for example, usually process male and female circular arc face and form trench and so on. From the traditional concept, form milling cutt...Form milling cutter is built-for-purpose cutter which process the form surface, for example, usually process male and female circular arc face and form trench and so on. From the traditional concept, form milling cutter is divided into pointed tooth and relieving follow its structure. Relieving shaped cutter is more convenient than pointed tooth milling cutter, because only its rake face is needed to grind after it turn into blunting, so the current books which are used in college almost select relieving shaped cutter in order to introduce how to design the form milling cutter.The curve of the back of tooth of relieving cutter is the transversal which is formed by the rear face of tooth in the end cut plane of the milling cutter. In the past, because of the limit of the manufacturing technology, the curve of the back of tooth is often selected Archimedes’ curve, in order that the shovel-nose tool acquire the uniform motion when the cutter shovel the back, in other word, the rear face of the milling cutter rotate its axis by the new cutting lip, in the same time, it move uniformly to the axis in order to form the surface. Although this curve of the back of tooth meet the fixedness of the form of blade around grinding the cutter, the rear angle of the dot of the cutting lip don’t keep fixedness. With the development of the modern manufacturing technology, the unmanageable problem of many complex curves is already easily solved. So it is need to study the optimum profile of the curve of the back of tooth in theory, and study the design theory of the relieving shaped cutter under the condition of new manufacture, in order to ensure that the rear angle of the dot of the cutting lip keep fixedness after the relieving shaped cutter is grinded. The paper derive the curve profile of tooth of the form cutter and the modifier calculation formula of the profile of the cutter edge from the definition of the rear angle of the cutter, which establish the foundation for the precision design and manufacture of other form cutter.展开更多
A successive tooth forming process for producing large modulus spur gears(m>2.5 mm)is firstly proposed in this paper to break the restrictions of large forming load and large equipment structure of traditional plas...A successive tooth forming process for producing large modulus spur gears(m>2.5 mm)is firstly proposed in this paper to break the restrictions of large forming load and large equipment structure of traditional plastic forming.It contains the preforming stage and the finishing stage.In the first stage,the die with a single-tooth preforms gear teeth one by one through several passes.In the second stage,the other die with multi-teeth refines the preformed teeth into required shape.The influence of total pressing depth and feed distribution in preforming stage on final forming quality is analyzed by numerical simulation,and the reasonable process parameters are presented.Successive tooth forming experiments are carried out on the self-designed gear forming device to verify the optimal simulation results.Gears without fold defects are well formed both in simulations and experiments,proving the feasibility of this method.Compared with the whole die forging process,the new technology has advantages of smaller load and simpler tooling,which shows a good potential for manufacturing large modulus and large size spur gears.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supported by National Natural Seienee Foundation of China,grant No.39970375wasmitiated in Dr YiPing Chen's lab Im the Department of Cell and Molecular Biology,Tulane Universuty,NewOrleans.Louisiana.U$A.
文摘It is well known that modern Aves Iack dentition,unlike their toothed ancestors ofthe Jurassic and cretaceous periods.However,in the chick oral cavity a rudiment forms thatresembles the lamina stage of the mammalian molar tooth germ.We have previously addressedthe molecular basis for this secondary loss of tooth formation in Aves by analyzing in chíckembryos the status of molecular pathways known to regulate mouse tooth development.In thisstudy,we further examined the moiecular pathways involved in positioning the site of toothrudinent.Similar te the mouse tooth germ,Pax9 serves as a marker for the presumptive dentalmesenchyme in the chick prior to any morphological manifestation of odontogenesis.Therestricted Pax9 expression in the chick mandibular mesenchyme is positioned by the two signalsfrom overlying oral epitheltum.FGF8 induces Pax9 expression while BMP4 prevents thisinduction.Thus it appears that,similar to that in tnice,the positíon of tooth rudiment in chickembryo is determined by two different types of signaling molecules with antagonistic sctiyity.These results further demonstrate that the early signaling pathways involved in odontogenesisremain inducible in Aves.
文摘The basic principle of equal base circle bevel gear (EBCBG) is illustrated simply Thetooth surface equation of EBCBG manufactured by end milling cutter with involute profile is de-rived. The tooth form error is analyzed on the basis of spherical involute
文摘Form milling cutter is built-for-purpose cutter which process the form surface, for example, usually process male and female circular arc face and form trench and so on. From the traditional concept, form milling cutter is divided into pointed tooth and relieving follow its structure. Relieving shaped cutter is more convenient than pointed tooth milling cutter, because only its rake face is needed to grind after it turn into blunting, so the current books which are used in college almost select relieving shaped cutter in order to introduce how to design the form milling cutter.The curve of the back of tooth of relieving cutter is the transversal which is formed by the rear face of tooth in the end cut plane of the milling cutter. In the past, because of the limit of the manufacturing technology, the curve of the back of tooth is often selected Archimedes’ curve, in order that the shovel-nose tool acquire the uniform motion when the cutter shovel the back, in other word, the rear face of the milling cutter rotate its axis by the new cutting lip, in the same time, it move uniformly to the axis in order to form the surface. Although this curve of the back of tooth meet the fixedness of the form of blade around grinding the cutter, the rear angle of the dot of the cutting lip don’t keep fixedness. With the development of the modern manufacturing technology, the unmanageable problem of many complex curves is already easily solved. So it is need to study the optimum profile of the curve of the back of tooth in theory, and study the design theory of the relieving shaped cutter under the condition of new manufacture, in order to ensure that the rear angle of the dot of the cutting lip keep fixedness after the relieving shaped cutter is grinded. The paper derive the curve profile of tooth of the form cutter and the modifier calculation formula of the profile of the cutter edge from the definition of the rear angle of the cutter, which establish the foundation for the precision design and manufacture of other form cutter.
基金Supported by National Natural Science Foundation of China(Grant No.51475271).
文摘A successive tooth forming process for producing large modulus spur gears(m>2.5 mm)is firstly proposed in this paper to break the restrictions of large forming load and large equipment structure of traditional plastic forming.It contains the preforming stage and the finishing stage.In the first stage,the die with a single-tooth preforms gear teeth one by one through several passes.In the second stage,the other die with multi-teeth refines the preformed teeth into required shape.The influence of total pressing depth and feed distribution in preforming stage on final forming quality is analyzed by numerical simulation,and the reasonable process parameters are presented.Successive tooth forming experiments are carried out on the self-designed gear forming device to verify the optimal simulation results.Gears without fold defects are well formed both in simulations and experiments,proving the feasibility of this method.Compared with the whole die forging process,the new technology has advantages of smaller load and simpler tooling,which shows a good potential for manufacturing large modulus and large size spur gears.
