Document Type

Article

Publication Date

8-16-2025

Abstract

The objective of this study was to assess the effect of different designs and depths of cusp reduction on fracture resistance of

maxillary permanent premolars restored with CAD/CAM composite restorations. A total of 42 sound maxillary premolars

were used. Standardized MOD cavities were prepared in all specimens. Teeth were randomly divided according to form of

cusp reduction into three main groups (n

=

14); G1:MOD cavities restored with inlays with no cusp reduction, G2:MOD

cavities restored with overlays with buccal and palatal anatomical cusps reduction, G3; MOD cavities restored with overlays

with buccal and palatal flat cusps reduction. Groups 2 and 3 were further sub-divided into two sub-groups (n

=

7) according

to amount of cusp reduction either 1.5 mm or 2.5 mm. All groups were restored by CAD/CAM resin composite indirect

restorations and cemented by adhesive resin cement. Thermocycling was done for all specimens. Fracture resistance was

tested by universal testing machine and failure modes were examined by stereomicroscope. Statistically analysis was done

for all data. Fracture resistance showed significant differences among the experimental groups (p < 0.001) with the highest

fracture resistance for overlays with 2.5 mm of anatomical reduction. Regarding the modes of failure, there were no signifi-

cant differences between experimental groups (p

=

0.489). The fracture resistance of the composite CAD/CAM fabricated

restorations is highly influenced by the restoration/prep design. The overlay design with anatomical cusps reduction of 2.5 mm

can reinforce maxillary premolars teeth with MOD cavities.

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