In vitro evaluation of the effect of post system and length on the fracture resistance of endodontically treated human anterior teeth

Yousief S, Tammam R, M. Galal R, Brakat A, Mohamed El Sayed H, Kamal A, Noushad M, Nassani MZ. Biomechanics of Central Incisor Endocrowns with Different Lengths and Milled Materials after Static and Vertical Loading: A Finite Element Study

Purpose

The aim of this study was to compare and assess the stress distribution and failure possibility of endodontically treated central incisor protected with endocrowns with different heights, with various CAD-CAM blocks such as IPS e.max CAD, Katana Zirconia, and Zolid Fx Zirconia.

Materials and Methods

A root canal-treated central incisor (plastic model) restored with an endocrown was scanned with a laser scanner to prepare a control model with a CAD software and then transferred to an FEA software. Proposed crown heights were 2, 4, and 6 mm. The model that was duplicated and restored with CAD-CAM blocks, IPS e.max CAD, Katana Zirconia, and Zolid Fx Zirconia were tested as endocrown materials. Bone geometry was simplified to be two coaxial cylinders in all models. Stress distributions under 50 N axial and oblique (with 135° angle from the vertical plane) loading were analyzed. Each model was then subjected to two occlusal loading conditions-the lingual slope of the incisal edge and the junction between incisal and middle thirds. Eighteen runs and calculations were performed to determine the endocrown height and material effect.

Results

The results showed a minor or negligible effect of changing the endocrown material. Increasing endocrown height was shown to reduce stresses and deformations on most of the model components (bone, gutta-percha, periodontal ligament, and endocrown), except root and cement. Differences in deformations and stresses between the two models of 4 and 6 mm were relatively smaller (ranged between 1% and 30%) compared to those between the 2 and 4 mm models (ranged between 10% and 400%).

Conclusions

The material used to fabricate endocrowns did not show considerable effect on the underlying structures. However, the endocrown design (2, 4, and 6 mm height) was shown to affect all components of the studied systems. Increasing endocrown height is recommended for bone, periodontal ligaments, and endocrown body, as it reduces stresses and deformations. On the other hand, it dramatically increases stresses on the root and cement layer. Smaller endocrown sizes represent an acceptable treatment option when there is a healthy periodontal state, while using larger sizes will be more suitable when there is a periodontal compromise with bone loss.

A microcomputed tomography analysis of adaptation in premolars with flared root canals restored with different digitally custom fabricated post materials

STATEMENT OF PROBLEM

Preserving and strengthening the remaining tooth structure of compromised flared root canals after endodontic treatment is challenging.

PURPOSE

The purpose of this in vitro study was to compare the adaptation of milled polymer- infiltrated ceramic, fiber-reinforced composite resin, and high-performance semicrystalline thermoplastic resin posts as used to restore mandibular premolars with flared root canals.

MATERIAL AND METHODS

Forty sound mandibular premolars were randomly divided into 4 groups: custom Vita Enamic (CV), custom fiber-reinforced composite resin (CF), custom polyetherketoneketone (CP), and prefabricated fiber (RF) posts. After endodontic treatment, each tooth was sectioned 1.5 mm occlusal to the cementoenamel junction. Then, the post space was prepared and flared, except the RF group, to a depth of 9 mm. The post space in RF group was prepared with a post drill. For the CV, CF, and CP groups, the posts were milled, finished, and cemented to their corresponding teeth. Each tooth was scanned using a microcomputed tomography device, and the reconstructed images were analyzed in mesiodistal, buccolingual, and horizontal planes. The cement thickness, cement volume, and volume of voids were measured. The data were analyzed using 3-way ANOVA (cement thickness) and 2-way ANOVA (cement volume and voids volume) tests followed by the post hoc Tukey test (α=.05).

RESULTS

The 3-way ANOVA test revealed a significant interaction (P<.001) between material type, section, and surface on the cement thickness. The mean cement thickness in the RF group was significantly higher than in the CV group (P=.001) and CF group (P=.005). The least mean cement thickness was at the apical section followed by the cervical and middle sections. Regarding cement volume, the 2-way ANOVA test showed statistically significant interaction between material type and section. The mean cement volume in the RF group was significantly lower than in the CV group (P=.001), CF group (P=.001), and CP group (P=.001). The highest mean cement volume was in the cervical section followed by the middle and apical sections. The 2-way ANOVA test showed statistically significant interaction (P<.001) between material type and section on the volume of voids. Significant differences were found between the mean volume of voids at the cervical and middle sections (P=.001) and the cervical and apical sections (P=.002).

CONCLUSIONS

Compared with prefabricated fiber posts, digitally fabricated polymer-infiltrated ceramic and fiber-reinforced composite resin posts had a thinner cement layer with minimal thickness at the apical section. The digitally fabricated posts had higher cement volume, especially at the cervical section, than prefabricated fiber posts. High volumes of voids were related to the cervical section of all tested posts.

Current Insights on Fiber Posts: A Narrative Review of Laboratory and Clinical Studies

PURPOSE

The aim of this study was to review the literature related to the clinical performance and laboratory findings regarding fiber posts, as well as the cementation technique employed with their use.

MATERIALS AND METHODS

A literature search was performed using an electronic database, PubMed/Medline, between 2010 and 2023. The terms used were "intra coronal post, fiber post, post cementation, and post length". Titles and abstracts were initially screened, and a full-text assessment was conducted for those that fulfilled the inclusion criteria. The reference list of the collected papers was also screened for further relevant citations.

RESULTS

In this work, 135 potentially eligible studies were analyzed. Titles and abstracts of 90 studies followed the inclusion criteria and were selected for a full-text assessment, resulting in 50 studies selected. Moreover, additional studies from relevant citations were included, totaling 57 studies.

CONCLUSION

According to the laboratory and clinical studies revised, the survival rate between fiber and prefabricated and cast metal posts was similar, and failures were mainly related to the loss of retention. The intra-canal post length of less than two-thirds of the root length presented successful results when ferrule was present. Furthermore, the ferrule increased the longevity of teeth restored with fiber posts. Additionally, the use of a surface treatment protocol for fiber posts and the adhesive cementation technique both contributed to the clinical success and longevity of the intra-canal post.

Fracture load assessment of digitally fabricated post and prefabricated fibre post in endodontically treated teeth

BACKGROUND

Endodontically treated teeth are structurally more susceptible to root fractures. Proper tooth restorations with digitally fabricated or fibre post following endodontic therapy is essential to restore function and esthetics.

OBJECTIVE

The aim of this in vitro study is to evaluate the fracture load of digitally fabricated and prefabricated fibre posts in endodontically treated teeth.

METHODS

Sixty extracted human single rooted teeth were selected. The crowns were sectioned at the cement-enamel junction to standardize the remaining root length at 15 mm from the apices. Cleaning, shaping and obturation was done using conventional step back technique to an ISO K-file size 40. The roots were divided into two groups of 30 samples each: Group S: teeth reinforced with digitally fabricated posts; Group F: teeth reinforced with fibre posts. Each group was further divided into three subgroups (S7, S9, S12, F7, F9, F12) based on lengths 7, 9 and 12 mm at which the posts were cemented. Composite resin core was fabricated and prepared to receive a complete metal crown. Universal testing machine was used to measure the compressive load required to fracture the teeth.

RESULTS

The highest fracture resistance of 1532N was observed with fibre posts at 12 mm of post space length followed by digitally fabricated post 1398N at 12 mm, but the difference was not statistically significant.

CONCLUSION

The highest fracture resistance was observed in the teeth restored with fibre posts with 12 mm length and the lowest with digitally fabricated post with 7 mm length. As the length of post increases irrespective of type of post fracture resistance increased.

Fracture strengths of endocrown restorations fabricated with different preparation depths and CAD/CAM materials

The objectives of this study were to compare the fracture strength of endocrown restorations fabricated with different preparation depth and various CAD/CAM ceramics, and to assess the fracture types. Endodontically treated 100 extracted human permanent maxillary centrals were divided into two preparation depth groups as short (S: 3-mm-deep) and long (L: 6-mm-deep), then five ceramic subgroups, namely: feldspathic-ceramic (Vita Mark II-VM2), lithium-disilicate glass-ceramic (IPS e.max CAD-E.max), resin-ceramic (LAVA Ultimate-LU), polymer infiltrated ceramic (Vita Enamic-VE) and monoblock zirconia (inCoris TZI-TZI) (n=10/subgroup). The endocrowns were fabricated by CAD/CAM and were cemented with resin cement (RelyX U200). The teeth were thermally cycled (5,000cycles) and fracture tests were performed at 45º angle to the teeth. The data were statistically analyzed (Kruskal-Wallis, Mann Whitney U), failure modes were evaluated with stereomicroscopy. Zirconia group provided the statistically highest fracture strength, but also exhibited non-repairable failures. Preparation depth has an effect on the fracture strength only for feldspathic ceramic.

Effect of fiber post length and abutment height on fracture resistance of endodontically treated premolars prepared for zirconia crowns

The purpose of this study was to compare the fracture resistance, mode of fracture, and stress distribution of endodontically treated teeth prepared with three different fiber post lengths and two different abutment heights, using both experimental and finite element (FE) approaches. Forty-eight human maxillary premolars with two roots were selected and endodontically treated. The teeth were randomly distributed into six equally sized groups (n = 8) with different combinations of post lengths (7.5, 11, and 15 mm) and abutment heights (3 and 5 mm). All the teeth restored with glass fiber post (Rely X Fiber Post, 3M ESPE, USA) and a full zirconia crown. All the specimens were thermocycled and then loaded to failure at an oblique angle of 135°. Statistical analysis was performed for the effects of post length and abutment height on failure loads using ANOVA and Tukey's honestly significant difference test. In addition, corresponding FE models of a premolar restored with a glass fiber post were developed to examine mechanical responses. The factor of post length (P < 0.01) had a significant effect on failure load. The abutment height (P > 0.05) did not have a significant effect on failure load. The highest mean fracture resistance was recorded for the 15 mm post length and 5 mm abutment height test group, which was significantly more resistant to fracture than the 7.5 mm post and 5 mm abutment height group (P < 0.05). The FE analysis showed the peak compression and tension stress values of 7.5 mm post length were higher than that of 11 and 15 mm post length. The stress value of remaining tooth decreased as the post length was increased. Within the limitations of this experimental and FE analysis study, increasing the post length inside the root of endodontically treated premolar teeth restored with glass-fiber posts increase the fracture resistance to non-axial forces. Failure mode is more favorable with reduced abutment heights.

Strength comparison of anterior teeth restored with ceramic endocrowns vs custom-made post and cores

PURPOSE

The aim of the study was to compare strength of the anterior teeth restored with ceramic endocrowns versus custom-made post and core.

METHODS

The investigation used the finite element analysis. Three 3-D models of maxillary central incisor were created: model A-tooth restored with metal post and core with ceramic crown; model B-tooth with leucite ceramic endocrown; model C-tooth with lithium disilicate ceramic endocrown. Each model was subjected to a 100N force applied at a distance of 5mm from the incisal edge, at the angle of 130° to the long axis of the tooth. The modified von Mises failure criterion was used to evaluate the strength of the dentin, ceramic and resin cement, and Huber-Mises-Hencky failure criterion for cast alloy. Contact stresses in the cement-tissue adhesive interface were calculated.

RESULTS

The lowest stresses occurred in the anterior tooth restored with custom post and core (model A). The mvM stress of 47.5MPa concentrated in leucite ceramic endocrown (model B) and its value was close to the tensile strength of this material. The maximal mvM stresses in the lithium disilicate ceramic endocrown (model C) were 4 times lower than tensile strength of this material. In all cases contact stresses in the adhesive interface under restorations did not exceed the resin cement bond strength to dentin.

CONCLUSIONS

Leucite ceramic endocrowns in incisors may fracture during physiological loading. Endocrowns made of lithium disilicate ceramic are resistant to failure. Posts and prosthetic crowns are still recommended for anterior teeth restorations.

Effect of 1-Piece Post and Core Fabrication Techniques on Fracture Strength

Purpose

The purpose of this in vitro study was to evaluate and compare the fracture strengths of post and core systems produced with different fabrication techniques and materials.

Methods

Forty extracted human single-root premolars were used in this study. After root canal treatment, the teeth were randomly divided into 4 groups of 10 each as follows: group C: metallic 1-piece posts and cores fabricated by casting, and serving as the control; group CM: metallic posts and cores fabricated with the copy milled technique; group LS: 1-piece posts and cores fabricated with the laser sintering technique; and group ZR: 1-piece zirconia posts and cores fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM). The posts and cores were cemented to the teeth with adhesive resin cement; then, the specimens were mounted to acrylic resin blocks, attached to an Instron Universal Testing Machine, and loaded with a crosshead speed of 1 mm/min, until fracture. Data were statistically analyzed using 1-way analysis of variance (ANOVA), followed by the post hoc Tukey test (α = 0.05).

Results

The highest fracture results were found in group ZR (315.4 ± 53.4 N), which showed significant differences from all other groups (p<0.05). The lowest test values were found in group C (230.2 ± 29.8 N). Group LS (250.9 ± 29.0 N), group CM (253.0 ± 22.4 N) and group C did not show any significant differences (p>0.05).

Conclusions

Custom-made zirconia 1-piece posts and cores, fabricated using the CAD-CAM procedure, can be an alternative treatment method when compared with other techniques.

In vitro fracture resistance of endodontically treated roots filled with a bonded filling material or different types of posts

AIM

This study aimed to compare the fracture resistance of roots filled with a bonded material, fiber posts, or titanium post systems.

METHODS

Canals in the first group were filled with AH Plus and gutta-percha cones, and roots in the second group were filled with Epiphany sealer and Resilon cones. The root fillings (60 roots) were removed up to 4 mm from the canal apex to obtain 10-mm-deep post spaces, and posts were cemented. The groups were as follows: AH Plus control group, Epiphany control group, AH Plus fiber post group, AH Plus titanium post group, Epiphany fiber post group, and Epiphany titanium post group. Fracture tests were performed by using an Instron testing machine. The force was applied at a 45° axial angle with a constant speed of 1 mm/min. For each sample, the force at which fracture occurred was recorded in units of newtons. Statistical analysis was carried out by using analysis of variance test.

RESULTS

There was no statistically significant difference between all groups (P > .05).

CONCLUSIONS

Titanium posts, fiber posts, and Epiphany root canal filling systems were found to have no reinforcing effect on endodontically treated roots.

Ribbond for treatment of complicated crown fractures: report of 3 cases

Dental trauma is relatively common and can occur secondary to sporting injuries, falls, fights, or accidents. According to the International Association of Dental Traumatology, 50% of children experience dental trauma between the ages of 8 to 12. There are many options for endodontic and restorative treatments of traumatized teeth. Ribbond, which was introduced in the market in 1992, consists of bondable, reinforced ultra-high strength polyethylene fibers. Ribbond may be an option for the treatment of traumatized teeth because of its aesthetic properties; absence of additional tooth preparation; and its high resistance to traction, which allows it to easily adapt to tooth morphology. In this report, we describe endodontic and restorative treatments using Ribbond for 3 female patients with horizontal complicated crown fractures of the maxillary incisors.