Effect of dentin bonding and ferrule preparation on the fracture strength of crowned teeth restored with dowels and amalgam cores

Comparative Evaluation of the Effect of Core Type and Antirotational Post on Stress Distribution in an Endodontically Treated Maxillary First Molar: FEA

Background

This study aims to analyze and compare the stress distribution in an endodontically treated maxillary first molar restored with various post and core systems and assess the benefit of the presence of an antirotational post and the effect of its length using finite element analysis.

Materials and Methods

Five 3D models of maxillary first molar restored with variable designs of post and core were constructed using CT scanning and information obtained from textbook and FEM software. Variables were types of core, presence or absence of an antirotational post, and length of the antirotational post. A load of 480 (N) vertically and a load of 240 (N) with 45° to the occlusal plane were applied. Results were analyzed using 3D von Mises criteria.

Results

The results showed that the most homogeneous stress distribution pattern along with dentin and the post-core system was observed in the model with one main post in the palatal canal and in the model with a two-piece core and one main post in the palatal canal and shorter antirotational post in the distal-buccal canal. However, models with one-piece core and antirotational post (either the same length or shorter than the main post) in the distal-buccal canal had the most stress concentration sites.

Conclusion

In this study, it was found that the presence of an antirotational post, its length, and type of core affected the distribution of stress along the dentin and post-core system. This study indicated that if the antirotational post is considered in the post-core design, it is better to use a two-piece core type due to more homogeneous stress distribution along the dentin and post-core system.

Stress Distribution on Root Dentin Analogous to Natural Teeth with Various Retentive Channels Design on the Face of the Root with Minimal or No Coronal Tooth Structure: A Finite Element Analysis

Aim:

The aim of this study was to evaluate post-core design on Stress distribution in maxillary central incisor with various designs retentive channels placed on the face of the root with no remaining coronal tooth structure.

Materials and Methods:

3 dimensional finite element model of a maxillary central incisor was developed and seven other study modes were developed. Tooth was scanned using CBCT unit, with reverse engineering software. 3D wire mesh, with ten node tetrahedral element, developed was transferred to ANASYS software. Composite was used for post-core-crown as post endodontic restoration. Mechanical properties were assigned to each component for FEA. All the materials were assumed to be isotropic, linearly elastic, homogenous and tightly bonded. A load of 100N were applied from vertical, horizontal and lateral oblique from incisal and palatal surface respectively.

Results:

Analysis revealed that stresses were concentrated at the point of load application on crown(vertical(V) 14.35MPa, horizontal(H) 27.04 MPa and lateral oblique(L)13.75MPa) and depending on the post core design the stresses were homogenous evenly distributed over the root dentin, core and least over the post. There was variation in stress distribution under vertical horizontal and lateral oblique load.

Conclusion:

Teeth with no remaining coronal structure and by placing retentive channels on the face of the root will enable homogenous stress distribution, promote mechanical retention and stability to the post core crown post endodontic restoration.

FE analysis of conceptual hybrid composite endodontic post designs in anterior teeth

OBJECTIVES

To assess conceptual designs of dental posts consisting of polyetherimide (PEI) reinforced with carbon (C) and glass (G) glass fibers in endodontically treated anterior teeth.

METHODS

3D tessellated CAD and geometric models of endodontically treated anterior teeth were generated from Micro-CT scan images. Model C-G/PEI composite posts with different Young's moduli were analyzed by Finite Element (FE) methods post A (57.7GPa), post B (31.6GPa), post C (from 57.7 to 9.0GPa in the coronal-apical direction). A load of 50N was applied at 45° to the longitudinal axis of the tooth, acting on the palatal surface of the crown. The maximum principal stress distribution was determined along the post and at the interface between the post and the surrounding structure.

RESULTS

Post C, with Young's modulus decreasing from 57.7 to 9.0GPa in the coronal-apical direction, reduced the maximum principal stress distribution in the restored tooth. Post C gave reduced stress and the most uniform stress distribution with no stress concentration, compared to the other C-G/PEI composite posts.

SIGNIFICANCE

The FE analysis confirmed the ability of the functionally graded post to dissipate stress from the coronal to the apical end. Hence actual (physical) C-G/PEI posts could permit optimization of stress distributions in endodontically treated anterior teeth.

Effect of ferrule on the fracture resistance of mandibular premolars with prefabricated posts and cores

PURPOSE

This study evaluated fracture resistance with regard to ferrule lengths and post reinforcement on endodontically treated mandibular premolars incorporating a prefabricated post and resin core.

MATERIALS AND METHODS

One hundred extracted mandibular premolars were randomly divided into 5 groups (n=20): intact teeth (NR); endodontically treated teeth (ETT) without post (NP); ETT restored with a prefabricated post with ferrule lengths of either 0 mm (F0), 1 mm (F1), or 2 mm (F2). Prepared teeth were restored with metal crowns. A thermal cycling test was performed for 1,000 cycles. Loading was applied at an angle of 135 degrees to the axis of the tooth using a universal testing machine with a crosshead speed of 2.54 mm/min. Fracture loads were analyzed by one-way ANOVA and Tukey HSD test using a statistical program (α=.05).

RESULTS

There were statistical differences in fracture loads among groups (P<.001). The fracture load of F2 (237.7 ± 83.4) was significantly higher than those of NP (155.6 ± 74.3 N), F0 (98.8 ± 43.3 N), and F1 (152.8 ± 78.5 N) (P=.011, P<.001, and P=.008, respectively).

CONCLUSION

Fracture resistance of ETT depends on the length of the ferrule, as shown by the significantly increased fracture resistance in the 2 mm ferrule group (F2) compared to the groups with shorter ferrule lengths (F0, F1) and without post (NP).

Titanium posts and bonded amalgam core longevity: A 22-year clinical survival retrospective study

BACKGROUND

The authors conducted a retrospective study to evaluate the long-term (18-22 years) clinic results of titanium post and bonded amalgam core restorations with metal-ceramic crowns placed in patients.

METHODS

From 1992 through 1996, the authors placed 88 restorations in 66 patients. They measured the ferrule effect in the minor dentin collar area. In 2014, the authors analyzed the following variables: ferrule length, length and thickness of the post, and tooth position.

RESULTS

The overall survival of the restorations decreased over time with survival rates of 89.6% after 5 years of follow-up appointments and 64.2% after 18 years of follow-up appointments. There were 42 failures, and the maxillary premolars had the most failures. The teeth with 2 or more millimeters ferrule length had a higher survival rate than those with a 0 to less than 2 mm ferrule length; these results were not statistically significant.

CONCLUSIONS

Statistically significant differences were detected according to the location of the tooth. The cores in the anterior teeth were 3.26 times more likely to fail than those in the molars, which presented higher survival rates; maxillary premolars had the most failures (28.5%). Both the metallic post length and its diameter did not influence restoration survival. The ferrule length was not statistically significant.

PRACTICAL IMPLICATIONS

The clinical technique to restore endodontically treated teeth that includes a titanium post and bonded amalgam restorations results in greater coronal destruction but shows good long-term results, ease of fabrication, and modest cost in comparison with other techniques.

A finite element study of teeth restored with post and core: Effect of design, material, and ferrule

Background:

Different postdesigns and materials are available; however, no consensus exists regarding superiority for stress distribution. The aim of this study was to evaluate the effect of design and material of post with or without ferrule on stress distribution using finite element analysis.

Materials and Methods:

A total of 12 three-dimensional (3D) axisymmetric models of postretained central incisors were made: Six with ferrule design and six without it. Three of these six models had tapered posts, and three had parallel posts. The materials tested were titanium post with a composite resin core, nickel chromium cast post and core, and fiber reinforced composite (FRC) post with a composite resin core. The stress analysis was done using ANSYS software. The load of 100 N at an angle of 45΀ was applied 2 mm cervical to incisal edge on the palatal surface and results were analyzed using 3D von Mises criteria.

Results:

The highest amount of stress was in the cervical region. Overall, the stress in the tapered postsystem was more than the parallel one. FRC post and composite resin core recorded minimal stresses within the post but the stresses transmitted to cervical dentin were more as compared to other systems. Minimal stresses in cervical dentine were observed where the remaining coronal dentin was strengthen by ferrule.

Conclusion:

A rigid material with high modulus of elasticity for post and core system creates most uniform stress distribution pattern. Ferrule provides uniform distribution of stresses and decreases the cervical stresses.

Ferrule Effect

The aim of this study was to systematically review the literature for laboratory and clinical studies to evaluate the effect of ferrule in restored endodontically treated teeth. The search was conducted in 2 databases (PubMed, Scopus) with no publication year/language limits. From 1,872 potentially eligible studies, 124 studies were selected for full-text analysis, and 37 were included for review, with 32 of those considered in the meta-analysis and 5 considered in the survival analysis. Two reviewers independently selected the studies, extracted the data, and assessed the risk of bias. For laboratory studies, a meta-analysis was performed for the comparison of the fracture resistance of teeth with and without ferrule, and 3 subgroup analyses were conducted for ferrule height, post type, and type of tooth. For clinical studies, the Kaplan-Meier method was used to determine the survival of restorations, with log-rank test used to identify differences between groups ( α = 5%). Teeth without ferrule had a lower fracture resistance ( P < 0.00001), and the higher the height of ferrule, the greater the fracture resistance was, irrespective of the type of post ( P < .000001). Teeth with ferrule had higher clinical longevity ( P = 0.002); however, the presence of a ferrule was related to higher survival only for premolars ( P = 0.05). In conclusion, the presence of a ferrule is responsible for an improvement in the fracture resistance of the restoration in laboratory studies. Yet, other clinical factors besides the ferrule may be associated with survival in molars and anterior teeth and need to be further investigated.

Knowledge Transfer Statement: The results of this study can be used by clinicians when deciding which approach to use when planning the restoration of endodontically treated teeth with and without ferrule. Ferrule may lead to higher tooth/restoration survival, while tooth location may influence therapeutic decisions.

Effect of ferrule height and glass fibre post length on fracture resistance and failure mode of endodontically treated teeth

The purpose of this study was to evaluate the combined effect of ferrule height and post length on fracture resistance and failure mode of endodontically treated teeth restored with glass fibre posts, composite resin cores and crowns. Ninety human maxillary central incisors were endodontically treated and divided into three groups (n = 30) according to the ferrule heights: 4, 2 and 0 mm, respectively. Post spaces in each group were prepared at 2/3, 1/2 and 1/3 of the root length (n = 10). The specimens were received fibre posts, composite resin core build up and cast metal crowns. After thermocycling, compressive static load was applied at an angle of 135° to the crowns. Two-way analysis of variance showed significant differences in the failure load in the ferrule height groups, no significant differences in post length groups and no significant interaction between ferrule heights and post lengths. More restorable failure modes were observed.

Fracture load of tooth restored with fiber post and experimental short fiber composite

Purpose:

This study evaluated the load bearing capacity of anatomically designed canines restored with FRC posts and experimental short fiber composite resin (FC). The effect of using three different types of tooth preparation and woven net on the fracture load was also investigated. Further aim was to evaluate the failure mode of each restoration.

Material and methods:

80 maxillary frasaco-canines were divided into 10 groups (n=8). The anatomic crowns were cut perpendicular at CEJ of the tooth. Group 1 was composed of teeth with flattened surface. Groups 2, 3 & 4 were prepared of teeth with 2 mm ferrule. In the third group, everStick Net was applied above the ferrule. Group 5 was composed of teeth with large box type preparation. The root canals were enlarged, sandblasted and then surface treated with Stick resin for 5 min. Two types of FRC root canal posts were used. The crowns were prepared either with composite resin or with FC. A static load until failure was applied to the crowns at a 45 degrees angle. Failure modes were visually examined.

Results:

ANOVA revealed that use of FRC-post and tooth preparation (p<0.001) had significant effect on fracture load of FRC-crown. The crowns made from only FC gave comparable fracture load to groups with FRC-post. No significant difference was found in load-bearing capacity between restorations reinforced with FRC net-substructure and those without (p>0.001). Chi-square test revealed that both, crown design and existence of FRC-post effected significantly fracture types (p<0.001).

Conclusion:

FC demonstrated similar load bearing capacity with restorations reinforced with FRC post. The presence of ferrule around the tooth increased the load bearing capacity significantly.

Abbreviations:

EET – endodontically treated teeth; FRC – fiber-reinforced composite; semi-IPN – semi-interpenetrating network; CEJ – cementoenamel junction; FC – experimental short fiber composite; SiC – silicon carbide abrasive paper; N – newton; FEM – finite element method.

Influence of ferrule preparation with or without glass fiber post on fracture resistance of endodontically treated teeth

Objective

This study evaluated the effect of ferrule preparation (Fp) on the fracture resistance of endodontically treated teeth, restored with composite resin cores with or without glass fiber posts.

Material and Methods

Forty-four bovine teeth were sectioned 19 or 17 mm (2 mm ferrule) from the apex, endodontically treated and assigned to four groups (n = 11): Group 1: Fp and post; Group 2: Fp and without post; Group 3: without Fp and with post; Group 4: without Fp and without post. All specimens were restored with composite resin core and metal crown. Specimens were subjected to fracture resistance testing in a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed by two-way ANOVA and Tukey’s tests (α=0.05).

Results

The mean fracture resistance values were as follows: Group 1: 573.3 N; Group 2: 552.5 N; Group 3: 275.3 N; Group 4: 258.6 N. Significantly higher fracture resistance was found for the groups with Fp (p<0.001).

Conclusion

There was no statistically significant interaction between the "Fp" and "post" factors (p = 0.954). The ferrule preparation increased the fracture resistance of endodontically treated teeth. However, the use of glass fiber post showed no significant influence on the fracture resistance.

Effect of reinforcement with resin composite on fracture strength of structurally compromised roots

This study was aimed at evaluating the fracture resistance of structurally compromised roots restored with four different post and core systems. Thirty-two bovine roots were uniformly shaped to simulate human mandibular premolar roots. The roots were divided into four groups based on the type of restoration: cemented cast post and core (Group MC), resin composite build-up (Group CR), resin composite and prefabricated glass fiber post build-up (Group FRC), and thick-layer dual-cured resin composite-reinforced small-diameter tapered cast post and core (Group CRM). After a static loading test, the failure mode and fracture resistance were recorded. Group CRM (719.38+/-196.73 N) exhibited a significantly high fracture resistance compared with the other groups (Group MC: 429.56+/-82.43 N; Group CR: 349.56+/-66.21 N; Group FRC: 398.94+/-112.71 N; p<0.05). In conclusion, Group CRM exhibited better mechanical properties for structurally compromised roots with no ferrules, although all types of restorations showed non-restorable fracture modes.