Aim:  Evaluate the marginal integrity and Clinical performance of PEEK endocrowns compared to lithium disilicate (E-Max) ceramic endocrowns. Methodology: Twenty six endocrowns were fabricated for posterior endodontically treated teeth. Patients were divided into two groups according to the material used for fabrication of the restorations; Group 1(control group) received E-Max endocrowns while Group 2 (intervention group) received Bio HPP PEEK endocrowns. The marginal integrity and internal fit were assessed using the silicon replica approach, in which each replica was sectioned into four segments, each with five reference points that were evaluated using a digital microscope at 35X magnification. After final cementation, the clinical performance of the restorations was evaluated according to the USPHS criteria in terms of marginal adaptation, fracture, and retention. These measurements were repeated after three, six, nine and twelve months respectively. Results: The marginal and internal gaps of both groups were within the clinical acceptable range, but E-Max group recorded statistically significant higher internal gap mean value than PEEK group. Regarding the clinical performance all restorations showed 100% alpha and there was no significant difference between both groups for all tested outcomes (Marginal adaptation, fracture, and retention) over one year.

The present study aims to evaluate the effect of different preparation designs on fracture resistance and failure mode of hybrid nanoceramic endocrown on premolars. Methodology: Fourteen endodontically treated maxillary premolars were prepared to receive a hybrid nanoceramic endocrown restorations and divided into 2 groups according to the preparation designs (butt joint and 2 mm ferrule). The endocrown restorations were cemented to the prepared teeth using dual cure adhesive resin cement. All specimens were subjected to a compressive force 5KN until fracture occurs by using universal testing machine. The maximum compressive force was recorded for all specimens, then failure mode of all samples were examined visually and photographically. All repairable samples were examined for extension of the cracks using scanning electron microscope. Results: Endocrowns with ferrule preparation recorded a highly statistically significant difference with the higher mean value of fracture resistance (1911.57 ± 341.29 N), compared to the endocrowns with butt joint which recorded the lower mean value of fracture resistance (1192.70±196.04 N). Regarding the failure mode; endocrowns with ferrule design showed a high percent of catastrophic failure while butt joint showed more repairable failure. Conclusion: Endocrowns with ferrule design showed a higher fracture resistance value but with a high percent of catastrophic failure mode compared to butt joint design that showed lower fracture resistance value with mostly repairable mode of failure.

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This study was carried out to compare between two techniques of gingival retraction (retraction cord and diode laser) regarding the amount of tissue displacement both laterally and vertically. Also, Patient satisfaction during their application. Methodology: twenty two cases requiring full coverage porcelain fused to metal fixed prosthesis in the anterior esthetic zone were taken from the outpatient clinic of the fixed prosthodontics department – Cairo University. The teeth were prepared with subgingival deep chamfer finish line and were distributed according to the technique of gingival retraction. Group I: Patients receiving retraction with the retraction cord. Group II: Patients receiving retraction with diode laser. In both groups measurement of lateral and vertical displacement done by using the stereomicroscope. also, patient satisfaction was measured by Comley and Demeyer numeric pain scale. There was significant difference between the two groups regarding lateral and vertical displacement. Laser troughing give not only more amount of vertical but also more lateral retraction whereas, P<0.05. For the patient satisfaction there was a significant difference between both groups, with laser troughing give better results.