الفهرس 
Restoration design considerationsOnly 14 pages are availabe for public view
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Abstract
Restoration of endodontically treated teeth is one of the extensively studied, yet one of the most controversial issues in dentistry. (1) Endodontically treated premolars have unfavorable anatomy making them more susceptible to cusp fractures under occlusal load than other posterior teeth. (4)
The present in vitro study was carried out to analyze the influence of internal axial cavity wall divergence and the depth of the central retention cavity on internal fit and fracture resistance of two adhesive endocrown restoration systems (IPS e.max® CAD and LavaTM Ultimate).
Forty-five maxillary premolars were selected for this study. Five intact maxillary premolars acted as control group. Forty maxillary premolars were endodontically treated, divided into two main groups according to pulp chamber depth (Group ―C‖ [n=20] with 5mm pulp chamber depth and Group ―R‖ [n=20] with 7mm pulp chamber depth). Decoronation was done 3mm above CEJ [n=40]. Each main group was subdivided into 2 subgroups with 2 different axial wall divergence (6 and 10 degrees per axial wall), resulting in 4 groups according to preparation design [n=10]. Optical impressions were taken using CEREC Omnicam® [n=40]. Each preparation design group [n=10] was randomly divided into 2 groups based on restorative material used (Group ―L‖ restored with LavaTM Ultimate, and Group ―E‖ restored with IPS e.max® CAD). All restorations were designed using CEREC AC and software package 4.23 and milled using the CEREC CAD/CAM system.
All restored samples (n=40) were scanned using CBCT system for internal fit assessment before and after controlled adaptation. Endocrowns of both investigated materials were cemented with the same adhesive resin cement. Fracture resistance under lateral load was evaluated using universal testing machine at a crosshead speed 1mm/min. Data was collected and statistically analyzed using SPSS version 20.0.
Results revealed that both endocrown material and axial cavity wall divergence have statistically significant effect on internal fit. While, axial cavity wall divergence has a statistically significant effect on fracture resistance under lateral load. Significant Internal fit improved was achieved after controlled adaptation of the endocrown restorations.