Indirect restorations for severe tooth wear: Fracture risk and layer thickness
Abstract
Objectives
This
in vitro study investigated static failure risk related to restoration
layer thickness for different indirect materials and compare them to
direct composites.
Methods
Two
ceramics (IPS e-max CAD, EmpressCAD (Ivoclar Vivadent)), two indirect
composites (Estenia (Kuraray), Sinfony (3M)) and two direct composites
(Clearfil AP-X (Kuraray), Tetric EvoCeram (Ivoclar Vivadent)) were
chosen. Of each material, 25 discs varying in thickness (0.5–3.0 mm)
were prepared and cemented to bovine dentine. For measuring compressive
strength, samples were placed in a universal testing device. Each sample
was uniaxially loaded until failure occurred. For each material a
regression model based on the Weibull distribution was used to estimate
the relation between restoration layer thickness and failure. Using
these models, the chance of failure, standard error and 95% confidence
interval for that chance is estimated. Groups of materials were compared
as well.
Results
Except for
Tetric Evoceram, all materials show a significant positive association
between layer-thickness and compressive strength, with an increased
strength of increased thickness. ProCAD performed significantly worse
than all other materials, especially when compared to the other ceramic
material (IPS e-max CAD) (p = 0.001).
Conclusion
For most tested materials, a thicker layer offers more strength, however, this property seems to be material/brand specific.
Clinical relevance
As
direct composites showed the best results within the limitations of
this in vitro study, dentists should consider these materials as a good
choice for restoring severe tooth wear, and may offer superior
performance compared to indirect composites and ceramics. For some
brands of materials thicker layers result in a stronger restoration.
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