Purpose:The aim of the study was to assess the effect of different endocrowns extensions inside the pulp chamber on the fracture resistance and failure mode of maxillary premolar.
Materials and methods:Twenty four single rooted upper premolars were root canal treated, arbitrarily divided into three main groups (n=8) according to extension of endocrowns inside the pulp chamber (GI= 2mm, GII= 3mm and GIII= 4 mm). Endocrowns were made-up from Brillient Crios (BC) CAD/CAM blocks and cemented with adhesive resin cement. Teeth were subjected to thermo-cycling and then to 45º oblique compressive load until fracture. The fracture resistance and failure modes were determined. Data were analyzed with One Way ANOVA followed by Tukey`s post hoc test for multiple comparisons.
Results:The fracture resistances were significantly different between all groups; GII scored the highest mean fracture resistance value (647±72.37 N) followed by GI (475.6±69.92 N), and the lowest was scored by GIII (353.9±61.02 N). Regarding fracture analysis of different preparation depths; Gr I showed highest repairability percentage followed be Gr II and Gr III; there was significant difference between Gr (I) and Gr (II) and between Gr (I) and Gr (III) as P-value < 0.05. While, there was insignificant difference between Gr (II) and Gr (III) as P-value > 0.05 as revealed by Chi Square test.
Conclusion:Different extensions of endocrowns inside the pulp chamber affect the fracture resistance and failure mode of upper premolar.
Purpose: The aim of this study was to evaluate the marginal adaptation of four monolithic CAD/CAM all-ceramic crowns cemented on implant abutments after fatigue loading.
Materials and methods:A lower right first molar was designed in CAD/CAM software and twenty crowns were machine milled using four different monolithic ceramic blocks (n=5): Group I: Vita Enamic (V.enamic), GroupII: IPS E-max CAD(e.max), GroupIII: Celtra Duo(CD), GroupIV: Functional explore (f.explore). The crowns were fabricated using CAD/CAM system. All crowns were cemented on implant abutments using self adhesive resin cement. Vertical margin gap distance of all crowns was measured using a digital microscope. All the samples were subjected to fatigue cyclic loading for 75.000 cycles. The vertical marginal gap distance for all samples were subsequently remeasured after the fatigue loading testing. Data were collected, tabulated and statistically analyzed.
Results:The highest marginal gap mean value was for CD group followed by f Explore group then V. Enamic group while the lowest marginal gap mean value was recorded with e.max group and this was statistically significant between the groups (P=0.0013< 0.05). The total marginal gap mean values with all types of ceramics were higher after aging than before with significant difference (P=<0.0001< 0.05).Conclusions: all-ceramic crown materials that are used for chair-side CAD/CAM systems demonstrated clinically acceptable marginal adaptations. V. Enamic and LD provided better marginal fit than CD and f.explore zirconia. Fatigue loading had a detrimental influence in the vertical marginal gap distance for all ceramic types except f.explore zirconia.
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