The most commonly used material for constructing complete dentures is polymethyl methacrylate (PMMA). However, the strength characteristics of PMMA, such as impact strength and fatigue strength, are poor, and fracturi...The most commonly used material for constructing complete dentures is polymethyl methacrylate (PMMA). However, the strength characteristics of PMMA, such as impact strength and fatigue strength, are poor, and fracturing of PMMA dentures is a common problem in prosthodontic practice. Reinforcing PMMA with various materials, such as carbon fibers, glass fibers (fiberglass), and ultrahigh modulus polyethylene fibers, has been suggested to strengthen the denture-base material. A common problem encountered when packing the resin on these specimens is fiber slippage beyond the denture edges. The present study proposes an alternative method of incorporating fiber meshes into complete dentures, whereby a thin filament of self-polymerizing resin at the perimeter of the fiber mesh is produced, giving a clear and stable shape to the mesh that fits the upper jaw cast. During placement of the shaped mesh on the cast, a positive-negative relationship is created between the mesh and cast, which immobilizes the mesh during the incorporation process.展开更多
In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completi...In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completion and testing, it was observed that the machine has the potential of generating reliable number of cyclic data. The machine’s performance was evaluated using test specimens of identical CUDs that were machined in conformity with standard procedures. The fatigue machine compressed the lower dental arch over the upper denture-specimen in centric occlusion, in the same way that the two masticatory muscles pull the lower jaw over the upper jaw during chewing. The incorporation of glass fibres into the CUD using a sandwich technique quadruples the lifespan of the denture (<em>P</em> = 0.004). The low standard deviation, along with the low coefficient of variation (CV) of the group of unreinforced dentures shows the repeatability of the results and the reliability of the machine. The high standard deviation and coefficient of variation of reinforced dentures was expected, since a high variation of results is usually recorded in fibre reinforcement cases. This research confirmed the view that the crack during denture fracture initiates in the anterior palatal area and propagates to the posterior.展开更多
The aim of this research is to clarify whether the midline axis of the complete upper denture (CUD) is the axis of its torsion during loading, apart from the known bending deflection. Furthermore the present study is ...The aim of this research is to clarify whether the midline axis of the complete upper denture (CUD) is the axis of its torsion during loading, apart from the known bending deflection. Furthermore the present study is intended to estimate the influence of the anterior notches on the torsional deformation of the CUD. Using commercial edentulous molds and standardized procedures, six identical CUDs were fabricated with an initial fraenal notch of 5 mm. Two additional notch conditions were produced by deepening the notch to a total depth of 9 mm and by creating an incisal diastema of 7 mm. Five biaxial (also known as “fish bone”) strain gauges were cemented onto the palatal section of the dentures so that their middle axis coincided with the midline axis of the outer surface of the denture. For the denture specimen used in this study, the specific point of torsion was detected 2 cm from the point of contact of the two artificial central incisors. The presence of a deep fraenal notch and the combination of the deep fraenal notch with the presence of an incisal diastema increased the torsion of the CUD to a significant level (P = 0.006 and P = 0.05, respectively). It was shown that the midline can be the CUD’s axis of torsion. Biaxial strain gauges could be a reliable method of measuring the torsional deformation of the CUD.展开更多
文摘The most commonly used material for constructing complete dentures is polymethyl methacrylate (PMMA). However, the strength characteristics of PMMA, such as impact strength and fatigue strength, are poor, and fracturing of PMMA dentures is a common problem in prosthodontic practice. Reinforcing PMMA with various materials, such as carbon fibers, glass fibers (fiberglass), and ultrahigh modulus polyethylene fibers, has been suggested to strengthen the denture-base material. A common problem encountered when packing the resin on these specimens is fiber slippage beyond the denture edges. The present study proposes an alternative method of incorporating fiber meshes into complete dentures, whereby a thin filament of self-polymerizing resin at the perimeter of the fiber mesh is produced, giving a clear and stable shape to the mesh that fits the upper jaw cast. During placement of the shaped mesh on the cast, a positive-negative relationship is created between the mesh and cast, which immobilizes the mesh during the incorporation process.
文摘In the present study, an aero pneumatic fatigue testing machine for complete dentures was designed, fabricated, and tested for the evaluation of the fatigue life of reinforced complete upper denture (CUD). On completion and testing, it was observed that the machine has the potential of generating reliable number of cyclic data. The machine’s performance was evaluated using test specimens of identical CUDs that were machined in conformity with standard procedures. The fatigue machine compressed the lower dental arch over the upper denture-specimen in centric occlusion, in the same way that the two masticatory muscles pull the lower jaw over the upper jaw during chewing. The incorporation of glass fibres into the CUD using a sandwich technique quadruples the lifespan of the denture (<em>P</em> = 0.004). The low standard deviation, along with the low coefficient of variation (CV) of the group of unreinforced dentures shows the repeatability of the results and the reliability of the machine. The high standard deviation and coefficient of variation of reinforced dentures was expected, since a high variation of results is usually recorded in fibre reinforcement cases. This research confirmed the view that the crack during denture fracture initiates in the anterior palatal area and propagates to the posterior.
文摘The aim of this research is to clarify whether the midline axis of the complete upper denture (CUD) is the axis of its torsion during loading, apart from the known bending deflection. Furthermore the present study is intended to estimate the influence of the anterior notches on the torsional deformation of the CUD. Using commercial edentulous molds and standardized procedures, six identical CUDs were fabricated with an initial fraenal notch of 5 mm. Two additional notch conditions were produced by deepening the notch to a total depth of 9 mm and by creating an incisal diastema of 7 mm. Five biaxial (also known as “fish bone”) strain gauges were cemented onto the palatal section of the dentures so that their middle axis coincided with the midline axis of the outer surface of the denture. For the denture specimen used in this study, the specific point of torsion was detected 2 cm from the point of contact of the two artificial central incisors. The presence of a deep fraenal notch and the combination of the deep fraenal notch with the presence of an incisal diastema increased the torsion of the CUD to a significant level (P = 0.006 and P = 0.05, respectively). It was shown that the midline can be the CUD’s axis of torsion. Biaxial strain gauges could be a reliable method of measuring the torsional deformation of the CUD.
