الفهرس 
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Abstract
With increase in demand for esthetics, all ceramic restorations replaced old ceramo-metal restoration. The all ceramic restorations appear to mimic the natural dentition appearance. Multiple ceramic restorative materials were used as permanent dental restorations. However early all ceramic materials were so abrasive to natural teeth and by so new generation of ceramic materials were developed to be more kindness on natural teeth.
The study of dental wear is common through the biomaterials literatures, since wide range of all ceramic dental restorative materials with various chemical, mechanical and physical characteristics were developed. Several aspects during selection of restorative materials should be considered, among which are the wear behavior and abrasive nature to natural enamel.
This study was designed to evaluate the wear behaviour and surface roughness of two ceramic systems (Vita Enamic & IPS e.max Press) and their natural enamel cusp antagonist.
A freshly extracted non-carious maxillary first molar was cut-off to isolate mesio-palatal cusp. The cusp then was embedded in acrylic block and prepared to antagonize flat ceramic samples. The flat ceramic samples of CAD/CAM Vita Enamic was cut-off with microtome to the required size of (14mm x 12mm x 2mm) while the IPS e.max press was pressed to the same required size.
Sixteen of flat ceramic slices, eight samples for each ceramic system were antagonize by sixteen natural enamel cusp block in a custom made tooth brushing wear machine. The wear cycles were adjusted to be of a total (60.000 cycles) under a load of 20N.
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Statistical analysis was carried out using the weight loss and surface roughness change between the two ceramic materials and antagonist enamel cusp. The results showed that there was statistical significant difference between the Vita Enamic and IPS e.max press samples in the mean weight loss perecent. The IPS e.max press samples (group B1) revealed the higher mean weight loss perecent (0.71% ± 0.25) than Vita Enamic samples (group A1) with value of (0.24% ± 0.11).
There was statistical significant difference regarding mean weight loss precent of the natural teeth (antagonist enamel cusp) antagonize the two ceramic systems, Teeth antagonize IPS e.max press show the higher mean weight loss percent change of (0.88% ± 0.27) than teeth antagonize vita Enamic (group A2) with value of (0.16% ± 0.05).
The results also showed that there was statistical significant difference between the Vita Enamic and IPS e.max press samples in the mean surface roughness percent change. The IPS e.max press show the higher value of (82.6% ± 37.1) than the Vita Enamic samples with value of (48.7% ± 23.9).
Also there was statistical significant difference regarding mean surface roughness precent change of the natural teeth (natural enamel cusp) antagonize the two ceramic systems, Teeth antagonize IPS e.max press show the higher mean surface roughness precent change of (189% ±147) than teeth antagonize vita Enamic (group A2) with value of (78% ±108).