Stress distribution in zirconia-reinforced glass ionomer restorations in molar incisor hypomineralization: A finite element analysis

Abstract

Objective

Investigating stress distribution in zirconia-reinforced glass ionomer cement (GIC), used to restore hypomineralized permanent first molars (HPFMs), under dynamic occlusal loading, using Finite Element Analysis (FEA).

Methods

CBCT and intra-oral scans of HPFM of an 8-year-old child were obtained. Three models were constructed using 3D-CAD software ‘MIMICS 21.0’. Model I represented a sound PFM, Model II: HPFM, and Model III: HPFM restored with zirconia-reinforced GIC (Zirconomer®). An idealized dynamic occlusal loading cycle (duration 0.25 s) was simulated consisting of Phases I and II, separated by point of Maximum Intercuspation (PoMI). The maximum and mean loads were 321 and 168 N, respectively. Abaqus-FEA software was used to record Von Mises (vM), and Maximum Principal (Pmax) stresses in the assembly (A), and in the models’ components: normal enamel (E), hypomineralized enamel (HE), restorative area (RA), and dentine (D).

Results

Maximum vM and P_max stresses were obtained at 0.18 s. Enamel was the stress-bearing component in all models. Model II revealed high stress concentration between E and HE. The highest stresses in the RA were obtained in Model II, and the lowest in Model III.

Conclusions

Favorable stress distributions were obtained in HPFM restored with zirconia-reinforced GIC. The high stress concentrations found at the junction between normal and hypomineralized enamel, and the poor physical properties of HE, may lead to post-eruptive enamel breakdown (PEB) common in HPFMs.

Clinical significance

Glass ionomer cements placed as interim restorations in molar incisor hypomineralization require strong physical properties and distribution of occlusal forces. This study shows that zirconia-reinforced GIC is an acceptable restoration in HPFMs.