Influence of Crown Ferrule Heights and Dowel Material Selection on the Mechanical Behavior of Root‐Filled Teeth: A Finite Element Analysis

Abstract

Purpose: This study used the 3D finite element (FE) method to evaluate the mechanical behavior of a maxillary central incisor with three types of dowels with variable heights of the remaining crown structure, namely 0, 1, and 2 mm. Materials and Methods: Based on computed microtomography, nine models of a maxillary central incisor restored with complete ceramic crowns were obtained, with three ferrule heights (0, 1, and 2 mm) and three types of dowels (glass fiber = GFD; nickel‐chromium = NiCr; gold alloy = Au), as follows: GFD0 – restored with GFD with absence (0 mm) of ferrule; GFD1 – similar, with 1 mm ferrule; GFD2 – glass fiber with 2 mm ferrule; NiCr0 – restored with NiCr alloy dowel with absence (0 mm) of ferrule; NiCr1 – similar, with 1 mm ferrule; NiCr2 – similar, with 2 mm ferrule; Au0 – restored with Au alloy dowel with absence (0 mm) of ferrule; Au1 – similar, with 1 mm ferrule; Au2 – similar, with 2 mm ferrule. A 180 N distributed load was applied to the lingual aspect of the tooth, at 45° to the tooth long axis. The surface of the periodontal ligament was fixed in the three axes (x = y = z = 0). The maximum principal stress (σmax), minimum principal stress (σmin), equivalent von Mises (σvM) stress, and shear stress (σshear) were calculated for the remaining crown dentin, root dentin, and dowels using the FE software. Results: The σmax (MPa) in the crown dentin were: GFD0 = 117; NiCr0 = 30; Au0 = 64; GFD1 = 113; NiCr1 = 102; Au1 = 84; GFD2 = 102; NiCr2 = 260; Au2 = 266. The σmax (MPa) in the root dentin were: GFD0 = 159; NiCr0 = 151; Au0 = 158; GFD1 = 92; NiCr1 = 60; Au1 = 67; GFD2 = 97; NiCr2 = 87; Au2 = 109. Conclusion: The maximum stress was found for the NiCr dowel, followed by the Au dowel and GFD; teeth without ferrule are more susceptible to the occurrence of fractures in the apical root third.

Three-dimensional finite element analysis of endodontically treated teeth with weakened radicular walls restored with different protocols

“…38 The finite element mesh of each model was imported with a finite element software (Abaqus 6.10-EF1; Dassault Systèmes Simulus Co) to simulate a static occlusal loading of 180 N on the lingual surface of the incisal third of the tooth at 45 degrees in all models. 29 For the boundary condition, the nodes of the periodontal ligament were fixed in the 3 axes in the Cartesian plane (x, y, and z) assuming values of x=y=z=0 (Fig. 3).…”

“…1). Regardless of the reconstructive technique of the internal radicular wall, a 50 mm thick cementation layer 29 was simulated in all models, with the exception of the GW model, in which the total thickness of the weakened area was simulated.…”

“…29 A metal ceramic crown was also designed and included a metallic coping 0.5 mm thick and a feldspathic veneering 0.5 mm thick on the buccal and lingual surfaces and 1.5 mm on the incisal surface. 29 …”

Stress distribution on dentin-cement-post interface varying root canal and glass fiber post diameters. A three-dimensional finite element analysis based on micro-CT data

“…According to some authors, a high number of vertical fractures are observed in roots with metallic posts with a high elastic modulus that distribute and concentrate stress in the apical third of the root 11,20,28 . Thus, the use of intra-radicular posts with an elastic modulus similar to dentin, such as glass fiber posts, promotes better stress distribution in the remaining dental structure and along the cementation interface 7,28 .…”

Influence of elastic modulus of intraradicular posts on the fracture load of roots restored with full crowns

“…The presence of a cervical ferrule positively affects the stress distribution pattern by reducing stress concentration on the root and risk of tooth fracture. Finite element analysis shows that the ferrule effect attenuates stress intensity on the root when either metal or fiber posts are used [12][13][14][15] . Previous studies also did not find a difference in fracture resistance between teeth restored with crowns and cast and post cores or fiber posts when a ferrule was present 13,16,17 .…”