The purpose of this study was to determine the effect of simulated ageing on the physical properties of some soft denture liners. The hardness, tensile strength and percentage elongation values were determined before and after ageing treatment. At the end of the experimental ageing process softening was observed only in Simpa and Ufigel L materials. It was established that ageing had insignificant effect on the hardness of other materials. It can be presumed that there will not be significant time-related changes in the hardness of these materials. Molloplast B preserved its highest value after the ageing process, whilst that of Simpa decreased to become comparable with Ufigel P.
The loss of one or more teeth is normally treated with conventional fixed or removable partial dentures or with implant supported fixed or removable dentures. This study investigated stresses formed around the implant and the antagonist natural tooth under occlusal force in the substitution of a missing lower first molar with a rigid or resilient IMZ (Intra Mobil Zylinder) implant, using the finite element stress analysis method. The results indicate that a bite force of 143 N resulted in high compressive stresses around the roots of a natural tooth opposing a restoration supported by an IMZ implant with rigid type abutment. It is speculated that these high compressive stresses may contribute to intrusion of the tooth.
The purpose of this study was to evaluate the microleakage characteristics of laminate veneers with different incisal edge preparation. Two groups of 20 extracted human maxillary central incisors were used for fabricating laminate veneers. The cervical margin of all veneers were placed 1 mm above the cementoenamel junction. The incisal finish line of 20 teeth was placed at the incisal edge (window type preparation). The incisal finish line of the other 20 teeth was placed linguoincisally (incisal edge overlapped type preparation). All veneers were fabricated according to the manufacturer's instructions with vacuum fired porcelain and cemented with dual-cure resin cement. The autoradiographic method was used for determination of microleakages. Microleakages at the interface of the laminate veneer and tooth were determined according to the scale described in the manuscript. Mc Nemar test was used for comparison of microleakages at cervical margins. Microleakage grades at other areas were compared in percentage. In the two preparation types the cervical microleakages were of similar degree. The incisal microleakages in the overlapped laminate veneers were greater than in the window type veneers. In conclusion, the window preparation type was more effective in terms of prevention of microleakage at the incisal margin than the overlapped type laminates.
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