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Abstract
Fixed prosthodontics still depends to a great extent on natural abutment teeth due to the tremendous cost of osseointegerated implant. Restoration of endodontically treated teeth has been subjected to many researches and improvements.
The growing need for biocompatibility, esthetics, and strength in prosthetic dentistry has led to the development of prefabricated ceramic posts such as : Tetragonal Zirconia Polycrystals (TZP), it is composed of zirconium dioxide (ZrO2), stabilized by 3% mol. yttrium oxide (Y2 O3).
This study evaluated and compared three esthetic core materials, IPS Empress COSMO ingot, Glass-infiltrated Vita-CELAY-Alumina, and Tetric –ceram HB where all of those cores were retained by prefabricated zirconia ceramic posts regarding their fracture resistance of the restoration.
As well as, to determine the mode of failure of the restorative system, either being restorable or non- restorable type.
Thirty intact human maxillary central incisor teeth recently extracted with their crowns cut 2mm coronal to the cemento-enamel junction (CEJ) were endodontically treated.
Group A Teeth restored with CosmoPost and glass ceramic heat-pressed ceramic cores as one unit.
Group B Teeth restored with CosmoPost and copy-milled VITA CELAY Alumina luted cores.
Group C Teeth restored with CosmoPost and Tetric-Ceram HB direct composite cores
Three groups of 10 specimens each were randomly formed. All groups restored with Cosmoposts 1.7 mm diameter adhesively luted by VariolinkII, only differed in their cores build-ups which were IPS Empress Cosmo ingots, Vita-Celay Alumina blanks, and Tetric-ceram HB, respectively restored groups (A), (B), and (C) .
All tested samples were embedded into acrylic resin, with 2-3mm layer of silicone in between and then secured in a universal testing machine where a static compressive load was applied palataly at 135-degree angle to the long axis of the tooth till failure, at a cross head speed of 1 mm/min.
All data were collected and analyzed statistically by using ‘SPSS’ program software. (Statistical Package For Social Science). (SPSS Inc, Chicago, Ill.), to determine the significance of the fracture loads between groups and for the evaluation of the mode of failure, with a significance level 5%, where P< 0.05.
The mean fracture loads in (Kg) and standard deviation were 65.9 / +15.37, 50 / + 13.07, and 80.5 / + 29.17 for groups A, B, and C respectively. Teeth restored with Tetric-ceram HB (group C) exhibited significantly higher fracture resistance than group B (Celay-Alumina), but statistically similar with group A (IPS Empress Cosmo) .
There was no statistical difference between various failure modes between groups, the non-restorable, catastrophic fracture were more observed at group B than C and A respectively.
Within the limitations of this study, it was concluded that: significantly higher failure loads were recorded for teeth restored with Tetric-ceram HB (group C) and IPS Cosmo ingots (group A).
More reparable cases were observed at group (A), where teeth and Cosmoposts were restored by IPS Empress Cosmo core ingots.