Effect of different onlay materials and resin core thickness on stress distribution in partial coverage restorations: a 3D finite element study.

Authors

Sensen Chen, Yao Chen, Sifan Chen, Changan Chen, Jie Lin

Published in

Clinical oral investigations. Volume 30. Issue 9. Aug 29, 2026. Epub Aug 29, 2026.

Abstract

To investigate the effects of onlay materials and resin core thickness on stress distribution in partial coverage restorations under static and thermal loading using finite element analysis (FEA).
A 3D mandibular first molar model was created from CBCT data. Four materials (zirconia, lithium disilicate [LD], polymer-infiltrated ceramic network [PICN], gold alloy [GA]) and five resin core thicknesses (1 mm to 4 mm, plus full crown control) were tested. A total of 20 models were loaded with 100 N occlusal force and thermal stresses (5-37 °C and 37-55 °C). The distribution characteristics of the maximum principal stress (MPS) were analyzed for different combinations of variables.
Under mechanical loading, thin resin cores (1-2 mm) performed best. Increasing thickness to 3 mm sharply raised enamel stress (zirconia: 77.35-80.72 MPa); at 4 mm, restoration stress peaked (zirconia: 150.12 MPa). Zirconia showed highest restoration stress (54.01-150.12 MPa) but lowest dentin stress (5.02-7.70 MPa); PICN had low and most stable restoration stress (55-91 MPa) but highest dentin stress (8-13 MPa). Under high-temperature thermal stress, enamel stress jumped sharply at ≥ 3 mm resin thickness, markedly higher than under low-temperature stress. GA with an extremely thin resin core (1R4O) caused abnormally high dentin stress (50.83 MPa) at low temperature.
A thin resin core (1-2 mm) offered better overall mechanical performance. Material type markedly influenced stress distribution. High-temperature thermal stress posed a greater threat to tooth structure than low-temperature stress. Thermal stress barely affected periapical/periodontal tissues.
For extensive MOD restorations, a 2 mm resin core is recommended as the safe threshold. Material selection should balance the protection of the restoration itself and the stress transfer to the tooth structure.

PMID:
42667412
Bibliographic data and abstract were imported from PubMed on 30 Aug 2026.

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