J Dent Rehabil Appl Sci.  2018 Dec;34(4):297-305. 10.14368/jdras.2018.34.4.297.

Stress distribution of molars restored with minimal invasive and conventional technique: a 3-D finite element analysis

• Yang S
• Kim SM
• Choi N
• Kim JH
• Yang SP
• Yang H

• KMID: 2432366
• DOI: http://doi.org/10.14368/jdras.2018.34.4.297

Abstract

PURPOSE
This study aimed to analyze stress distribution and maximum von Mises stress generated in intracoronal restorations and in tooth structures of mandibular molars with various types of cavity designs and materials.
MATERIALS AND METHODS
Threedimensional solid models of mandible molar such as O inlay cavity with composite and gold (OR-C, OG-C), MO inlay cavity with composite and gold (MR-C, MG-C), and minimal invasive cavity on occlusal and proximal surfaces (OR-M, MR-M) were designed. To simulate masticatory force, static axial load with total force of 200 N was applied on the tooth at 10 occlusal contact points. A finite element analysis was performed to predict stress distribution generated by occlusal loading.
RESULTS
Restorations with minimal cavity design generated significantly lower values of von Mises stress (OR-M model: 26.8 MPa; MR-M model: 72.7 MPa) compared to those with conventional cavity design (341.9 MPa to 397.2 MPa). In tooth structure, magnitudes of maximum von Mises stresses were similar among models with conventional design (372.8 - 412.9 MPa) and models with minimal cavity design (361.1 - 384.4 MPa).
CONCLUSION
Minimal invasive models generated smaller maximum von Mises stresses within restorations. Within the enamel, similar maximum von Mises stresses were observed for models with minimal cavity design and those with conventional design.

Keyword

finite element analysis; inlay; minimal cavity design; stress; composite

MeSH Terms

Bite Force
Dental Enamel
Finite Element Analysis*
Inlays
Mandible
Molar*
Tooth

Figure

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  Fig. 1 (A) Stereolithography (STL) scan image of mandibular first molar. (B) 3D CAD model of pulp, dentin, and enamel were generated and assembled.

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  Fig. 2 Two conventional inlay models of O cavity (CGC), MO cavity (MG-C), and two minimal invasive designs for occlusal caries (OR-M) and proximal caries (MR-M) models were made.

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  Fig. 3 A total amount of 200 N axial load was applied at 10 occlusal points: 5 points in buccal cusp area and 5 points in marginal ridges and central fossa area (model OG-C). Solid model with restoration, enamel, dentin, and pulp chamber of the mandibular molar was meshed with tetrahedral elements. Bottom of the model was fixed in all directions as a boundary condition.

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  Fig. 4 Minimal invasive cavity designs (OR-M, MR-M) produced very small maximum von Mises stress magnitude compared to conventional inlay designs in the restoration. There were no significant differences in maximum stress magnitudes within the abutment tooth among models.

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  Fig. 5 Von Mises stress distribution generated by occlusal loading in the restoration of each experimental model. Models with composite (OR-C, MR-C) showed stress concentration at the loading area. Models with gold alloy (OG-C, MG-C) showed widely distributed stresses within the restorations.

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  Fig. 6 Von Mises stress distribution by occlusal loading in the restoration and the abutment tooth with M-D cross-sectional view. Models of OG-C and MG-M produced well distributed stress inside the gold restoration.

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  Fig. 7 Cavosurface margin between resin restorations (OR-C, MR-M) and tooth structures showed significant difference in stress gradient and distribution. Peak stress was observed at the occlusal loading area and cemento-enamel junction in all models.

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  Fig. 8 Von Mises stress distribution by occlusal loading in the abutment tooth with M-D cross-sectional view. Note stress concentration was observed around the occlusal contact area, pulp horns, and cemento-enamel junction.

Reference

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