Elucidating interfacial failure of cervical restorations using damage mechanics: A finite element analysis

Although clinical studies have suggested a link between non-axial forces and reduced longevity of cervical restorations, the underlying mechanisms require further numerical investigation. This in-silico study employed a cohesive zone model (CZM) to investigate interfacial damage in a cervical restoration subjected to different load directions.

A plane strain model of a maxillary premolar was established, with a wedge-shaped buccal cervical restoration. To simulate debonding, the restoration-tooth interface was modeled by the CZM, which defines the strain-softening damage behavior based on interfacial stress and fracture energy. Occlusal loads were applied in three different directions: (1) obliquely on the buccal triangular ridge, (2) obliquely on the palatal triangular ridge, and (3) equal magnitude axially on both ridges. Damage initiation and progression were analyzed, and stress distribution in damaged models was compared with the corresponding perfect-bond models.

Non-axial oblique loads initiated damage at lower forces (100 N for buccal and 120 N for palatal) compared to axial loads (130 N on both ridges). After debonding, buccal oblique loading caused higher stress at the central groove (42.5 MPa at 150 N). Furthermore, buccal oblique loading resulted in more extensive debonding than that caused by the palatal oblique load (88.3% vs. 43.3% of the bonding interface at 150 N).

The study provides numerical evidence supporting the tooth flexure hypothesis, that non-axial forces are more detrimental to the bonding interface of the cervical restoration. The results highlight the necessity of damage mechanics in deriving stress distribution upon debonding.