Effect of Fiber Post-Resin Matrix Composition on Bond Strength of Post-Cement Interface

The load capacity of maxillary central incisor with simulated flared root canal restored with different fiber-reinforced composite post and cementation protocols

Background

This study aimed to evaluate the load capacity of maxillary central incisors with simulated flared root canal restored with different fiber-reinforced composite (FRC) post cemented with either self-adhesive or self-etch resin cement and its mode of fracture.

Methods

Sixty-five extracted maxillary incisors were decoronated, its canal was artificially flared and randomly categorized into group tFRC (tapered FRC post) (n = 22), mFRC (multi-FRC post) (n = 21), and DIS-FRC (direct individually shaped-FRC (DIS-FRC) post) (n = 22), which were further subdivided based on cementation resin. The posts were cemented and a standardized resin core was constructed. After thermocycling, the samples were loaded statically and the maximum load was recorded.

Results

The load capacity of the maxillary central incisor was influenced by the different FRC post system and not the resin cement (p = 0.289), and no significant interaction was found between them. Group mFRC (522.9N) yielded a significantly higher load capacity compared to DIS-FRC (421.1N). Overall, a 55% favorable fracture pattern was observed, and this was not statistically significant.

Conclusion

Within the limitation of the study, it can be concluded that prefabricated FRC posts outperform DIS-FRC posts in terms of the load capacity of a maxillary central incisor with a simulated flared root canal. The cementation methods whether a self-adhesive or self-etch resin cement, was not demonstrated to influence the load capacity of a maxillary central incisor with a flared root canal. There were no significant differences between the favorable and non-favorable fracture when FRC post systems were used to restored a maxillary central incisor with a flared root canal.

Push-Out Bond Strength of Endodontic Posts Cemented to Extracted Teeth: An In-Vitro Evaluation

(1) Background: An ideal bond strength between endodontic posts and root canal dentin is essential for optimal retention and good prognosis. This study aimed to evaluate the push-out bond strength (PBS) of prefabricated fiber and metal posts, luted with resin cement to natural dentin. (2) Methods: Extracted premolars with similar root dimensions were assigned into two groups of 30 each for the metal and fiber posts. Teeth were mounted in acrylic blocks exposing 2 mm of the coronal root. Teeth were subjected to endodontic treatment and post-space preparations. Two groups were further subdivided into three sub-groups (n = 10) according to the size of the posts (# 4, 5 and 6). Posts were cemented with resin cement. Specimens were sectioned into 4 mm slices and subjected to the PBS test. (3) Results: The mean PBS was similar for the metal and fiber posts bonded with resin cement, showing a statistically significant result. An increase in post size increased the bond strength initially, but a further increase in size did not show any marked difference. A total of 71.66% of tested specimens failed with the adhesive failure mode. (4) Conclusions: Metal posts showed slightly higher retention compared to the fiber posts, although the p-value was similar for both types. An increase in the size of posts showed increased retention. The most common mode of failure was adhesive failure between cement and dentin.

Push-Out Bond Strength Assessment of Different Post Systems at Different Radicular Levels of Endodontically Treated Teeth

This study assessed the bond strength of prefabricated post systems at different root levels of endodontically treated teeth. One-rooted human premolars (N = 70; n = 10) were cut to 2 mm above the cement-enamel junction. Root canals were treated and randomly assigned to one of the seven post systems: T: Titanium (Mooser), ZrO: Zirconia (Cosmopost), G: Fiber (FRC Postec Plus), E1: Fiber (Direct) (Everstick post), E2: Fiber (Indirect) (Everstick post), PP: Fiber (PinPost), and LP: Injectable Resin/Fiber composite (EverX Posterior). All posts were luted using a resin cement (Variolink II), and the roots were sectioned at the coronal, middle, and apical root levels. Push-out tests were performed in the Universal Testing Machine (0.5 mm/min). Data (MPa) were analyzed using two-way ANOVA and Tukey’s tests (α = 0.05). The results showed that the bond strength (mean ± SD) of E2 posts were highest (5.3 ± 2.7) followed by PP (4.1 ± 2.0); G (4.0 ± 1.6); LP (2.6 ± 1.9): T (2.2 ± 1.5) and ZrO (1.9 ± 1.0) posts systems. No significant differences were found in bond strength of all post systems. The bond strength in the coronal root level was the highest with 3.6 ± 2.2 MPa. The bond strength of FRC post systems was significantly higher than those of rigid posts of titanium or ZrO₂. Bond strength results were the highest in the coronal root level for all tested post systems but did not differ significantly from the other two root levels.

Bond Strength of New Fiber Post-system (Rebilda GT)

AIM: The aim of this in vitro study is to determine the push-out bond strength of bundle glass fiber post (Rebilda GT) and tapered glass fiber post (Rebilda fiber post). MATERIALS AND METHODS: Twenty freshly extracted human single rooted premolar teeth were used, all teeth were endodontically treated, after 24 h from obturation the gutta-percha removed leaving 5 mm apically to ensure clinically acceptable apical seal. Finally, all canals were flushed with 2 ml NaOcl 5.25% and 2 ml distilled water, respectively, then the canals were dried using paper points. The roots were divided randomly into two sets with ten roots for each group according to post-type. Group A: Rebilda fiber posts were used. Group B: Rebilda GT bundle fiber posts were used. The posts were inserted into the canals according to the manufacturer instructions. All specimens were stored for 72 h in an incubator. Slices of 2 mm thickness were cut from the roots at different levels (cervical, middle, and apical thirds), bond strength was determined using universal testing machine at a speed of 0.5 mm/min. RESULTS: One-way analysis of variance and Tukey HSD tests showed that the (bundle fiber) Rebilda GT fiber post had bond strength higher than that of the Rebilda fiber post in all regions. (p < 0.05), also the cervical area showed higher bond strength in both groups than the middle and the apical areas, respectively. CONCLUSIONS: The bundle glass fiber post (Rebilda GT) showed bond strength higher than the taper glass fiber (Rebilda fiber) post in all regions (apical, middle, and cervical). The cervical region showed higher bond strength than the middle and the apical thirds.

Development of fibre-reinforced composite disk for computer-aided design-computer-aided manufacturing milled posts; Experimental composite disk using e-glass fibre in different fibre direction

Aims

To evaluate the flexural properties of computer-aided design-computer-aided manufacturing (CAD-CAM) milled posts fabricated from the experimental fibre-reinforced composite disks in different fibre direction, and to compare the flexural properties of the CAD-CAM milled posts to those of commercial prefabricated posts, RelyX and FRC PostecPlus.

Settings and Design

In vitro comparative study.

Materials and Methods

E-glass fibre was used to fabricate the CAD-CAM composite disks. The fibres were prepared in unidirectional and multidirectional arrangements into the epoxy resin, at 70% by weight. The disk was milled by the Cerec InLab CAD-CAM system to fabricate a post. Ten posts for each type of disk were prepared. Two types of commercial fibre posts, RelyX fibre post, and FRC PostecPlus were used as control. The three-point bending test was performed.

Statistical Analysis Used

The data were analysed using one-way ANOVA and Game-Howell post-hoc test.

Results

The results indicated that both commercial fibre posts had the highest flexural strength and flexural modulus. The unidirectional experimental post yielded significantly lower values in both flexural strengths (739.1 ± 24.1 MPa) and flexural modulus (21.0 ± 3.5 GPa) compared to the control posts, while the multidirectional experimental posts had extremely low flexural strength and flexural modulus.

Conclusions

The direction of the fibres significantly influenced the mechanical properties of the posts. The experimental unidirectional fibre-reinforced composite disk showed the potential to be used as a CAD-CAM disk for post and core fabrication.

Performance of crowns cemented on a fiber-reinforced composite framework 5-unit implant-supported prostheses: in silico and fatigue analyses

OBJECTIVE

To characterize the biomechanical performance of fiber-reinforced composite 5-unit implant-supported fixed dental prostheses (FDPs) receiving individually milled crowns by insilico and fatigue analyses.

METHODS

Eighteen implant-supported five-unit fiber-reinforced composite frameworks with an individually prepared abutment design were fabricated, and ninety resin-matrix ceramic crowns were milled to fit each abutment. FDPs were subjected to step-stress accelerated-life testing with load delivered at the center of the pontic and at 2nd molar and 1st premolar until failure. The reliability of the prostheses combining all loaded data and of each loaded tooth was estimated for a mission of 50,000 cycles at 300, 600 and 900 N. Weibull parameters were calculated and plotted. Fractographic and finite element analysis were performed.

RESULTS

Fatigue analysis demonstrated high probability of survival at 300 N, with no significant differences when the set load was increased to 600 and 900 N. 1st and 2nd molar dataset showed high reliability at 300 N, which remained high for the higher load missions; whereas 1st premolar dataset showed a significant decrease when the reliability at 300 N was compared to higher load missions. The characteristic-strength of the combined dataset was 1252 N, with 1st molar dataset presenting higher values relative to 2nd molar and 1st premolar, both significantly different. Failure modes comprised chiefly cohesive fracture within the crown material originated from cracks at the occlusal area, matching the maximum principal strain location.

SIGNIFICANCE

Five-unit implant-supported FDP with crowns individually cemented in a fiber-reinforced composite framework presented a high survival probability. Crown fracture comprised the main failure mode.

Effect of Interpenetrating Polymer Network (IPN) Thermoplastic Resin on Flexural Strength of Fibre-Reinforced Composite and the Penetration of Bonding Resin into Semi-IPN FRC Post

The purpose of this study was to evaluate the effects of interpenetrating polymer network (IPN) thermoplastic resin on the flexural strength of fibre-reinforced composite (FRC) with different IPN polymer compositions. The penetration of bonding resin into semi-IPN FRC posts was also evaluated. The IPN thermoplastic resin used was UDMA-MMA monomer with either PMMA (0.5%, 2%, 5%) or PMMA-copolymer (0.5%, 2%). A no added IPN polymer resin was also made. Mixed resin was impregnated to S- and E-glass fibre rovings. These resins and resin impregnated fibres were used for flexural strength (FS) test. To evaluate the penetration of bonding resin into semi-IPN post, SEM observation was done with various impregnation time and polymerization mehods (hand-light- and oven-cure). The result of FS was recorded from 111.7 MPa (no-IPN polymer/no-fibre-reinforcement) to 543.0 MPa (5% PMMA/S-glass FRC). ANOVA showed that there were significant differences between fibre-reinforcement and no-fibre-reinforcement (p < 0.01) both in S- and E-glass fibre groups, and between 0.5% PMMA and 5% PMMA in the S-glass FRC group. SEM micrographs showed that the penetration layers of bonding resin into hand-light cured semi-IPN posts were different according to impregnation time. Fibre reinforcement is effective to improve flexural strength. The depth of penetration layer of bonding resin into semi-IPN matrix resin was improved when a hand-light cure was used.

A laboratory study to assess the physical, mechanical, and 3-D structural properties of nano-apatite grafted glass fibre-based endodontic posts

AIM

To fabricate and characterize nano-hydroxyapatite (nHA) grafted and non-grafted glass fibre-based endodontic posts.

METHODOLOGY

Experimental glass fibre posts were fabricated using silanized nHA grafted (ex-HA) and non-grafted glass fibre (ex-P) reinforced resins. The structural analysis and morphological patterns were analysed with Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. EverStick^® glass fibre posts (eS) were used as a control group. The degree of conversion, flexural strength, and flexural modulus was investigated and the fractured structure was evaluated with a scanning electron microscope. Root canals were prepared in human extracted teeth restored with experimental and control posts. The push-out bond strength was evaluated with radicular dentine at days 7, 30, and 90, and the presence of voids at the interface were measured at day 1, 7, 30, and 90 with micro-computed tomography. The Shapiro-Wilk test and one-way ANOVA post-hoc Tukey's test were performed. The level of significance was set at 0.05.

RESULTS

The SEM and FTIR confirmed the presence of a silane-coupling agent on the glass fibres. The ex-HA post had a significantly lower degree of conversion compared to the ex-P post (p = .0008), but a significantly higher conversion than the eS post (p = .0014). The maximum flexural strength value was obtained with the ex-HA post with an insignificant difference (p = .366) compared to ex-P post and a significant difference (p = .029) compared to the eS post. The flexural modulus of ex-HA, ex-P, and eS posts were significantly different (p = .037). Similarly, the ex-HA post had a significantly higher push-out bond strength at days 7 and 30 (p = .037) compared to the ex-P and eS posts. The volume of voids had a nonlinear behaviour amongst the groups with no significant difference between the posts.

CONCLUSION

The fabrication of the experimental posts was successful and the ex-HA post had greater flexural strength and push-out bond strength compared to the ex-P post. The degree of conversion of the ex-HA post was lower than the ex-P and eS posts. The volume of voids of ex-HA and ex-P posts was lower than that of eS posts.

Physicochemical and mechanical characterization of a fiber-reinforced composite used as frameworks of implant-supported prostheses

OBJECTIVES

To characterize the physicochemical and mechanical properties of a milled fiber-reinforced composite (FRC) for implant-supported fixed dental prostheses (FDPs).

METHODS

For FRC characterization, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction, Fourier-transformed infrared spectrometry, simultaneous thermogravimetric analysis and differential scanning calorimetry were performed. For fatigue testing, 3-unit FRC frameworks were fabricated with conventional (9 mm² connector area) and modified designs (12 mm² connector area and 2.5 mm-height lingual extension). A hybrid resin composite was veneered onto the frameworks. FDPs were subjected to step-stress accelerated-life fatigue testing until fracture or suspension. Use level probability Weibull curves at 300 N were plotted and the reliability for 100,000 cycles at 300, 600 and 800 N was calculated. Fractographic analysis was performed by stereomicroscope and SEM.

RESULTS

The FRC consisted of an epoxy resin (∼25%) matrix reinforced with inorganic particles and glass fibers (∼75%). Multi-layer continuous regular-geometry fibers were densely arranged in a parallel and bidirectional fashion in the resin matrix. Fatigue analysis demonstrated high probability of survival (99%) for FDPs at 300 N, irrespective of framework design. Conventional FDPs showed a progressive decrease in the reliability at 600 (84%) and 800 N (19%), whereas modified FDPs reliability significantly reduced only at 800 N (75%). The chief failure modes for FRC FDPs were cohesive fracture of the veneering composite on lower loads and adhesive fracture of the veneering composite at higher loads.

SIGNIFICANCE

Milled epoxy resin matrix reinforced with glass fibers composite resulted in high probability of survival in the implant-supported prosthesis scenario.

Need for an alternative method to cement fiber-reinforced posts - A pushout bond strength analysis

Background:

The use of dissimilar materials used as posts, luting agents, and the core often makes the restorative procedure quite complicated, as each material demands its own technical process. Furthermore, it may not necessarily result in better collective physical properties.

Aim:

The aim of this study was to analyze the pushout bond strength of a zirconia-based core buildup material in cementing two fiber posts.

Methods:

Eighty single-rooted mandibular premolars were decoronated, endodontically treated, post space prepared, and randomly assigned to one of the following four groups: carbon fiber post luted with PermaCem 2.0, carbon fiber post luted with LuxaCore Z Dual, glass fiber post luted with PermaCem 2.0, and glass fiber post luted with LuxaCore Z Dual. Pushout bond strength was evaluated in a universal testing machine for each of the 2 ± 0.5 mm sections obtained from the samples (total 160 sections)

Statistical Analysis:

One-way ANOVA and post hoc tests were used for statistical analysis.

Results:

The glass fiber posts cemented with LuxaCore Z showed significantly higher pushout bond strength (P < 0.001).

Conclusion:

LuxaCore Z Dual-core build material was more effective as a luting agent for glass fiber post cementation.

Push-out Bond Strength of Two Types of Dental Post Luted with Two Types of Cement at Two Different Root Levels

OBJECTIVE

Endodontically treated teeth may require posts for retaining the core and replacing the coronal structures that have been lost. The objective of this study was to evaluate and compare the push-out bond strength between different types of post cemented with different types of luting cement at different types of root level.

MATERIALS AND METHODS

In this in-vitro study, a total of 48 single-rooted permanent human teeth were decoronated, and the roots were treated endodontically. Following post space preparation, the sample was divided into four groups (n= 12 each) based on the types of post and cement. Two different types of post [GC everStick®POST (ES) and Parapost® Fiber LuxTM (PF)], and two different types of cement [G-CEMTM (G), and RelyXTM Unicem (R)] were used according to the manufacturer's instructions. All roots were sectioned at the coronal and middle thirds with a thickness of 3±0.1mm. The Push-out bond strength (PBS) test was performed using a universal testing machine at a cross-head speed of 0.5mm/ min. The bond strength values were recorded, and the data were analyzed using the SPSS program. Apart from descriptive statistics, three-way ANOVA was used for the interaction of the independent variables (post, cement, and root level). For differences between the groups, the Mann-Whitney U test was used. A P-value of less than 0.05 was considered significant for all analyses.

RESULTS

Push-out bond strength of samples at the middle level (11.38±10.31 MPa), with PF posts (11.18±9.98 MPa), and of those luted with RelyXTM Unicem cement (13.26±8.73 MPa) was higher than that of their counterparts. The PBS means of RelyXTM Unicem cement at both root levels were much higher than PBS means of G-CEMTM cement. Three-way ANOVA test revealed a significant effect for each variable with a higher effect of cement (Sum of Squares= 1310.690; P< 0.001). No significant difference (P= 0.153) was found between the coronal and middle parts and between ES and PF posts (P= 0.058). However, a highly significant difference (P< 0.001) was found between RelyXTM Unicem and G-CEMTM cements.

CONCLUSION

The type of cement had a significant effect on push-out bond strength with RelyXTM Unicem which had higher values than G-CEMTM. However, the type of post and root level had no significant effect on PBS, although Parapost® Fiber LuxTM and middle root level had higher values than their counterparts.

State of the Art Contemporary Prefabricated Fiber-Reinforced Posts

Background:

There is an increased interest in investigating and use of prefabricated fiber-reinforced posts by scientists and clinicians in the restoration of endodontically treated teeth.

Objective:

The objective of this narrative review was to summarize the composition of contemporary prefabricated fiber-reinforced posts and elucidate its effect on the different properties of these posts.

Methods:

PubMed/Medline, Scopus, and Google Scholar were searched from January 1990 to December 2019 for English Language articles describing the composition and properties of prefabricated fiber-reinforced posts. First, the search strategy was established for Medline / PubMed using the following terms ((Fiber post[All Fields] OR (fiber reinforced post[All Fields] AND composition[All Fields] AND (“matrix”[MeSH Terms] OR (“fiber”[All Fields] AND “properties”[All Fields] AND “epoxy”[All Fields]) OR “dimethacrylate”[All Fields]) AND NOT (CAD CAM[All Fields])). The search strategy was then adapted for Scopus and Google Scholar databases to identify eligible studies.

Results:

The current state of the art of prefabricated fiber-reinforced posts revealed a myriad of products with different formulations which are reflected on the mechanical and handling characteristics of the different posts available in the market. More recent research and development efforts attempted to address issues related to the improved transmission of polymerization light through the post to the most apical end of the restoration inside the root canal. Others focused on the development of new matrix materials for fiber-reinforced posts.

Conclusion:

A review of the literature revealed that currently available prefabricated fiber-reinforced posts consist of a heterogeneous group of materials which can have a significant effect on the behavior of posts. Understanding different formulations will help clinicians in scrutinizing the vast literature available on prefabricated fiber-reinforced posts. This, in turn, will help them make an informed decision when selecting materials for the restoration of endodontically treated teeth.