الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 100 |  |  |
| | | from | 100 | | |
Abstract
Zirconia became popular in dentistry because of this material’s excellent mechanical properties which include high strength, fracture toughness and biocompatibility. Zirconia was mainly used as a substructure for ceramic restorations and required veneering ceramics to obtain proper esthetics because of their high opacity. Despite the excellent physical properties of zirconia, veneer chipping has been identified as a major cause of failure. To overcome veneer chipping, dental manufacturers developed monolithic zirconia prostheses. One major concern with the use of monolithic zirconia as a restorative material is the abrasive nature and wear against opposing enamel because of this material’s hardness and surface roughness
Therefor this study was carried out to clinically evaluate the wear behavior of human enamel and chipping of two ceramic materials for the posterior teeth. The examined materials were veneered zirconia “Katana super translucent layered by feldspathic” and monolithic zirconia “Katana super translucent”.
Thirty-four zirconia full coverage restorations (seventeen in each group) were fabricated for teeth requiring full coverage restorations after root canal treatment in posterior area. The patients were divided into two groups according to the type of zirconia used. group 1 (comparator group) veneered zirconia crowns and group 2 (intervention group) monolithic zirconia single crowns.
All included patients were photographed firstly the teeth were scaled and polished before any restoration. Most of teeth were restored firstly with fiber post and composite core while the other teeth restored with composite core only then preparation was done according to type of each material “veneered zirconia crown group, an axial tooth reduction of 1.5
mm, an occlusal reduction of 2 mm, and a deep chamfer finish line was done using tapered round diamond stone. While for the monolithic zirconia crown, an axial tooth reduction of 1 mm, an occlusal reduction of
1 to 1.5 mm, and a deep chamfer finish line was done using tapered round diamond stone”. Crowns fabrication was performed using Dof extra oral scanner and imes-icore CORiTEC 350i milling machine with exocad software. All crowns were lab polished according to manufacturer’s instructions for each material. The crowns were cemented either by glass ionomer or self-adhesive resin cement.
Sectional impression was taken for opposing arch using vinylpolysiloxane addition silicon in sectional stock trays immediately after crowns cementation, three, six and twelve months to measure the wear. While chipping of the crowns were measured using modified United States Public Health Services (USPHS) criteria.
Results:
Chipping was graded according to modified USPHS. All restorations were reported as alpha with no chipping.
While wear was recorded by using replica technique and optical profilometer and the results showed that there was no statistically significant difference between (group 1) and (group 2).
This indicated that both materials are clinically accepted to be used as full coverage restoration in posterior teeth.