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. 2025 Jun 2;16(6):205.
doi: 10.3390/jfb16060205.

Fracture Resistance of CAD/CAM-Fabricated Zirconia and Lithium Disilicate Crowns with Different Margin Designs: Implications for Digital Dentistry

Tareq Hajaj  1   2 , Diana Marian  3 , Cristian Zaharia  1   2 , Serban Talpos Niculescu  4 , Radu Marcel Negru  5 , Florina Titihazan  1   2 , Mihai Rominu  1   2 , Cosmin Sinescu  1   2 , Andreea Codruta Novac  1   2 , Gabriel Dobrota  6 , Ioana Veja  3
Affiliations

Fracture Resistance of CAD/CAM-Fabricated Zirconia and Lithium Disilicate Crowns with Different Margin Designs: Implications for Digital Dentistry

Tareq Hajaj et al. J Funct Biomater. .

Abstract

Objective: This in vitro study aimed to evaluate the influence of cervical margin design-tangential versus chamfer-on the fracture resistance of monolithic crowns fabricated from lithium disilicate and zirconia ceramics.

Materials and methods: Forty extracted human molars were randomly assigned to two preparation types: chamfer and tangential. Each group was restored with CAD/CAM-fabricated crowns made from either zirconia (IPS e.max® ZirCAD Prime) or lithium disilicate (IPS e.max® CAD), resulting in four subgroups (n = 10). Standardized adhesive cementation protocols were applied. After 24 h storage in distilled water, the specimens underwent static load-to-failure testing using a ZwickRoell ProLine Z005 universal testing machine.

Results: Zirconia crowns with chamfer margins exhibited the highest mean fracture resistance (2658 N), while lithium disilicate crowns with tangential margins showed the lowest (1862 N). Chamfer preparation significantly increased the fracture resistance of lithium disilicate crowns (p < 0.01), whereas margin design had no significant effect on zirconia. All restorations exceeded physiological masticatory forces, confirming their clinical viability.

Conclusions: Cervical margin design significantly affected the fracture performance of lithium disilicate crowns but not zirconia. Chamfer preparations are recommended when using lithium disilicate to optimize mechanical strength. These findings underscore the importance of preparation geometry in guiding material selection for CAD/CAM ceramic restorations.

Keywords: CAD/CAM; adhesive cementation; cervical margin; chamfer; fracture resistance; lithium disilicate; tangential; zirconia crowns.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Representative tooth preparations illustrating the two cervical margin designs evaluated in this study: chamfer design (left) and tangential design (right). These geometries influence the distribution of occlusal stress and may affect the fracture resistance of ceramic restorations.
Figure 2
Figure 2
IPS e.max® ZirCAD Prime, Ivoclar Vivadent.
Figure 3
Figure 3
CAD-CAM VHF milling system.
Figure 4
Figure 4
IPS e.max® CAD CEREC, Ivoclar Vivadent.
Figure 5
Figure 5
Conditioning of the tooth structure with 36% phosphoric acid (H3PO4) during adhesive surface pretreatment.
Figure 6
Figure 6
SpeedCEM® Plus (Ivoclar Vivadent), a dual-cure self-adhesive resin cement used for crown luting.
Figure 7
Figure 7
Light-curing of the restorations using a LED polymerization unit (Bluephase N®, Ivoclar Vivadent; 800 mW/cm2) for 20 s per surface.
Figure 8
Figure 8
ZwickRoell ProLine Z005.
Figure 9
Figure 9
Zirconia rod applying occlusal force.
Figure 10
Figure 10
Fracture resistance of monolithic crowns with different margin designs. Bar graph representation of mean fracture resistance (±SD) for each group (n = 10). Error bars represent standard deviations. Asterisks (*) indicate statistically significant differences (p < 0.01) between margin types within the same material, n.s. indicateno significant difference, as determined by Tukey’s post hoc test.
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