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

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 Pmax 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.