الفهرس 
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Abstract
The present study was conducted to evaluate two contemporary CAD/CAM overlays compared to direct fiber post reinforced composite restorations both laboratory and clinically.
Fifty maxillary premolars used in this study ,forty of them received endodontic treatment and cavity prepared for overlay were used and randomly distributed into 4groups of 10 each and restored as following: Zirconia overlay (Katana Zirconia HT), Resin Nano Ceramic overlay (Lava Ultimate) , Glass fiber post and composite (Filtek Z250). While unrestored specimens served as a negative control. Ten sound teeth served as a positive control .Vertical marginal gap was examined under the stereomicroscope. Fracture resistance test was carried out using a universal testing machine, and presence of micro-cracks was detected using a stereomicroscope. The fracture mode of the specimen was identified using scanning electron microscopy.Statistical analysis of marginal gaps revealed significant statistical differences as CAD/CAM overlays had higher vertical marginal gap, Katana zirconia and Lava ultimate, compared to FPR composite. There was a statistically significant difference between fracture resistance of Katana zirconia overlays and all comparing groups. Katana zirconia overlays did not showed any fracture.
Ten patients (2 male& 8 female) their age ranged from (30-45) were selected. Each patients must have 3 premolars complying with the inclusion criteria were randomly assigned.
group 1: Ten teeth were restored with a Zirconia ceramic (KATANA Zirconia HT).
group 2: Ten teeth were restored with a Resin Nano Ceramic blocks (Lava Ultimate).
group 3: Ten teeth were restored with direct glass fiber post reinforced composite restoration ((Filtek Z250).
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All restorations were clinically evaluated on recalls periods during 18 months. The variables studied were: marginal integrity, wear of restoration and antagonist, recurrent dental caries, fracture, gingivitis, cavosurface margin discoloration and anatomic form following the description of Modified USPHS criteria. Marginal integrity, wear of restoration and antagonist, recurrent dental caries and gingivitis all restorations received Alfa rating at all recall periods. Among the 30 restorations evaluated in this clinical study, restorable fracture occurred in only 3 during the analyzed period2 composite and 1 lava ultimate. 4 Katana zirconia overlays and 2 lava ultimate overlays showed cavosurface margin discoloration.
In conclusion, CAD/CAM overlays and FPR composite are conservative treatment option that could be used to restore damaged endodontic treated teeth.