Chemical degradation of ceromers ans its effect on their color stability and hardness

The chemical degradation of two ceromers [Targis, Vita Zeta LC] and its effect on their color stability and hardness had been studied. A total of 40 samples were constructed and divided into 2 groups [20 samples each]. Each group represented one of the tested materials and was subdivided into 2 subgroups [10 samples each] according to the color shade used [A3. B4]. Each subgroup was further subdivided into 2 divisions composed of 5 samples each. The first division was used as a control group and was subjected to hardness test. While the second division was subjected to a color measurement test, then to a chemical degradation test and re-subjected to a color measurement test and finally subjected to hardness test. The results showed that there was a statistical significant difference in weight loss due to chemical degradation between the two tested materials. While there was no difference between the 2 shades used for the two ceromers. The results also showed a statistical significant difference in hardness between the control group of the two ceromers and the group subjected to chemical degradation lest. Also, there was a significant statistical difference in hardness between the two tested ceromers. The difference in deltaE recorded between samples before and after the chemical degradation lest was in the range of clinical acceptance

Effect of surface corrosion of ceramo-metallic porcelain finished by different methods on their surface roughness and bacterial accumulation

The effect of surface corrosion of ceramo-metallic dental porcelain finished by autoglazing, overgIazing and polishing on their surface roughness and bacterial accumulation was studied. Thirty samples were constructed from one type of commercial available ceramo-metallic porcelain [VMK 95, Vita, Germany]. These samples were divided into 3 groups [10 samples each]. Each group represented one type of finishing method. Then each group was subdivided into 2 subgroups 5 samples each]; the first subgroup [control], this subgroup was not subjected to corrosion test, while the second subgroup was subjected to corrosion test. The two subgroups were then subjected to surface roughness test, followed by a bacterial accumulation test. The results showed that there wasn't a statistical significant difference between the surface roughness of the tested ceramic for the autoglazed and the overglazed groups before and after corrosion. While there was a statistical difference between these two groups and the polished group before and after corrosion test. At the same time there was a significant difference between the two subgroups of the polished group. Overglazed recorded the least surface roughness, while the polished ceramic recorded the highest surface roughness. Polished ceramic showed bacterial accumulation and it had increased due to corrosion test. While Overglazed and autoglazed ceramic didn't record any bacterial accumulation. The microscopic examination of the accumulated bacteria revealed two species of bacteria gram positive bacilli anthrocoid and gram positive diplococci pneumococci

Corrosion behavior and hardness of veneering materials

The corrosion behavior and hardness of different types of veneering materials were studied. Five veneering materials were used in this study. Three types of dental ceramic materials, representing two categories of ceramic veneering material: VMK 95, Vita [a metal ceramic veneering material], Omega 900, Vita [a metal ceramic veneering material], Vitadur Alpha, Vita [a ceramic used to veneer In-Ceram]. Two types of ceromers namely; Vita Zeta LC, Vita and Targis, Ivoclar. Fifty samples were prepared. The samples were divided into 5 groups, 10 samples each. Each group was further subdivided into 2 subgroups according to the type of test carried out. The first subgroup was subjected to hardness test while the second subgroup was subjected to electrochemical corrosion test [Potentiodynamic], then subjected to hardness test. The results showed that VMK 95 showed the worst corrosion behavior, while the Omega 900 and Vita Zeta LC showed the best corrosion behavior. The results showed that there is no relation between corrosion behavior and hardness of the tested veneering materials. The results also showed no statistical significant difference in hardness between the non-corroded and the corroded samples of all the tested veneering materials