The Effect of Ferrule/Crown Ratio and Post Length on the Applied Stress and Strain Distribution to the Endodontically Treated Maxillary Central Teeth: A Finite Element Analysis

Abstract

Objectives: One of the most common methods used for the reconstruction of endodontically treated teeth is post and core and crown. Various factors such as the remaining tissue above the cutting margin (ferrule) affect the fracture resistance of teeth restored with post and core and crown. This study aimed to investigate the effect of ferrule/crown ratio (FCR) on the strength of maxillary anterior central teeth using finite element analysis.
 Materials and Methods: A 3D scan of a central incisor was obtained, and the data were transferred to Mimics software. Then, a 3D model of the tooth was designed. Next, 300N load was applied at a 135° angle to the tooth model. Force was applied to the model both horizontally and vertically. Ferrule height was considered to be 5%, 10%, 15%, 20%, and 25% in the palatal surface and 50% in the buccal surface. The length of post in the model was 11, 13, and 15mm.
 Results: By increasing the FCR, stress and strain distribution increased in the dental model and decreased in the post itself. As the horizontal angle of load application increased, the level of stress and strain created in the dental model increased as well. The closer the force application site to the incisal area, the higher the stress and strain would be.
 Conclusion: Maximum stress was inversely correlated with FCR and post length. In ratios of 20% and higher, insignificant changes occurred in stress and strain patterns in the dental model.

Factors Influencing Vertical Radicular Fractures in Teeth Supported by Metallic Dental Core: A Scoping Review

“…In a three-year clinical follow-up study, only 6.67% of incisors restored with 2 mm ferrule posts were damaged, while the rate for teeth without ferrule reached 26.20%. 19 However, in the study by Samran A. and al. conducted on mandibular premolars, the specific location of the ferrule had no significant effect on fracture resistance under the study’s conditions.…”

“… 18- Mosharaf R. and al. (2023) 19 (Finite Element Analysis Studies) A 3D scan of a central incisor To study the effect of the ferrule height-to-crown ratio on the strength of maxillary anterior central teeth using finite element analysis. 3D scan of a maxillary central incisor.…”

“… 11 These findings are consistent with the study by Misharaf R. and al., which indicates that a reduced post length reduces stress in the cervical region of the tooth and increases stress at the post’s end. 19 An interplay exists between the height of the ferrule and the post length, and in the presence of high residual coronal height, a shorter post length might be feasible.…”

Effect of Ferrule Location on Fracture Resistance of Maxillary Premolars: An In Vitro Study

“…According to finite element studies, presence of ferrule yields favorable stress distribution in roots. In addition, higher ferrule would result in lower stress and consequently decrease in clinical failure [ 12 , 13 , 15 , 34 ]. It is highly favorable to provide a complete CF with a minimum height of 2 mm which improves the prognosis of ETT [ 29 ].…”

Effect of Ferrule Design on Stress Distribution of Maxillary Incisor Rehabilitated with Ceramic Crown and PEEK Post–Core Material: A 3D Finite Element Analysis

“…Although studies have concluded that the design of the ferrule does not exert an influence on the biomechanical performance of endodontictreated incisor teeth [10,12], there is consensus that the presence of an incomplete ferrule is considered a better option than the complete lack of it [9,13,14]. Many studies have assessed the impact of different ferrule heights [14][15][16] and the influence of the post material [1,17,18] in the development of non-reparable (below the cement-enamel junction-CEJ-leading to tooth extraction) or reparable (above CEJ) tooth fractures [8,19]. However, there are a lack of studies testing incomplete ferrule designs and their interaction with one-piece post-core made of PEEK related to the stress distribution of human maxillary incisors rehabilitated with monolithic zirconia crowns; thus, these are the parameters tested in this study.…”