Abstract
Purpose: To compare the #fracture resistance and mode of failure of CAD-CAM #monolithic hybrid composite-nanoceramic crowns with
different occlusal thickness.
Materials and Methods: Thirty CAD-CAM monolithic hybrid #composite-nanoceramiccrowns with different occlusal thickness were
randomly distributed into 3 groups: 0.5 mm, 1.0 mm and 1.5 mm. The
restorations were cemented onto human molars with a self-adhesive
resin cement. The specimens were loaded until fracture; the fracture
resistance and mode of failure were recorded.
Results: The strength of the specimens progressively increased
with occlusal thickness; the highest resistance to fracture was
reported in
1.5 mm-thick crowns but no statistically significant differences were
noticed among the experimental groups (p>0.05). The ultrathin crowns
(0.5 mm) were mainly interested by unrestorable fractures.
Conclusion: The #occlusalthickness of CAD-CAM monolithic
crowns did not influence the fracture resistance of restorations but it
significantly affected their mode of failure; the occlusal thickness of
such restorations can be reduced up to a lower bound of 1.0 mm in order
to
keep sufficient strength to with stand occlusal loads; CAD-CAM
monolithic hybrid composite-nanoceramic crowns showed sufficient
fracture
resistance to be used in molar regions but not in an ultrathin
configuration (0.5 mm).
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