Self-adhesive cements as core build-ups for one-stage post-endodontic restorations?

Dental Fiber-Post Systems: An In-Depth Review of Their Evolution, Current Practice and Future Directions

The field of dental medicine is constantly evolving and advancing toward minimally invasive techniques. Several studies have demonstrated that bonding to the tooth structure, particularly enamel, yields the most predictable results. In some instances, however, significant tooth loss, pulpal necrosis, or irreversible pulpitis may limit the options available to the restorative dentist. In these cases, placement of a post and core followed by a crown is the preferred treatment option, provided all requirements are met. This literature review provides an overview of the historical development of dental FRC post systems as well as a comprehensive examination of the currently available posts and their bonding requirements. In addition, it offers valuable insights for dental professionals seeking to understand the current state of the field and the prospects of dental FRC post systems.

Immediate and long-term microshear bond strength of resin-based cements to core build-up materials

Background

To evaluate the microshear bond strength (μ-SBS) between resin-based cements and core build-up materials after water storage.

Material and Methods

Cylinders (1x1 mm) of conventional dual-cure resin cement (RelyX ARC, 3M ESPE), universal dual-cure resin cement (RelyX Ultimate, 3M ESPE) or self-adhesive resin cement (RelyX U200, 3M ESPE) were adhered to disks (6x2 mm) made with commercial core build-up materials (Bis-Core, Bisco or LuxaCore Z, DMG) or conventional nanocomposite resin (Filtek Z350 XT, 3M ESPE). The specimens (n=10) were submitted to μ-SBS test using a universal testing machine and fracture pattern analysis at 48 hours or after 9 months of water storage. The data were evaluated by three-way ANOVA for repeated measures and Tukey’s test (α=0.05).

Results

After 48 hours, regardless of the resin-based cement used, the μ-SBS to the conventional resin composite (Filtek Z350 XT) was greater compared to other materials. However, after 9 months, there was a statistically significant decrease in μ-SBS values between the conventional resin composite and evaluated luting agents. The μ-SBS values of core build-up commercial materials (Bis-Core and LuxaCore Z) did not change over time. Regardless of the composite used and storage time, there was no statistically significant difference between the resin-based cements. After 48 h, the most prevalent failure was mixed for all groups. However, after 9 months, the core build-up materials showed a predominantly mixed fracture pattern whereas the resin composite presented an adhesive pattern.

Conclusions

Commercial core build-up materials achieved stable bonding performance with resin-based cements over time.

Key words:Composite resins, resin cement, dental restoration failure.

Effect of Composite Core Materials on Fracture Resistance of Endodontically Treated Teeth: A Systematic Review and Meta-Analysis of In Vitro Studies

Various material properties are involved in the success of endodontically treated restorations. At present, restorative composites are commonly employed as core build-up materials. This study aimed to systematically review the literature to assess the effect of using composite core materials on the in vitro fracture of endodontically treated teeth. Two different reviewers screened the literature, up to June 2021, in five distinct electronic databases: PubMed (MedLine), Scopus, Scielo, ISI Web of Science, and EMBASE. Only in vitro studies reporting the effect of the use of composite core materials on the fracture resistance of endodontically treated teeth were included. A meta-analysis was carried out using a software program (Review Manager v5.4.1; The Cochrane Collaboration, Copenhagen, Denmark). The risk of bias in each study was assessed following the parameters of another systematic review. A total of 5016 relevant papers were retrieved from all databases. After assessing the title and abstract, five publications remained for qualitative analysis. From these, only three studies remained for meta-analysis. The fracture strength of endodontically treated teeth where a core build-up composite was used was statistically significantly higher than the control (p = 0.04). Most of the analyses showed a high heterogenicity. The in vitro evidence suggests that the composite core build-up with higher filler content tended to improve the fracture resistance of the endodontically treated teeth, in comparison with conventional composite resins. This research received no external funding. Considering that this systematic review was only carried out on in vitro papers, registration was not performed. Furthermore, there were no identified clinical studies assessing core build-up materials; therefore, more well-designed research on these materials is needed.

Interface analysis after fatigue loading of adhesively luted bundled fiber posts to human root canal dentin

OBJECTIVES

The aim of this study was to assess the fatigue loading behavior and fracture resistance of endodontically treated teeth restored with adhesively luted bundled fiber posts in comparison to solid fiber posts. Image analysis (2D and 3D) was applied to evaluate modes of failure and to characterize susceptible parts of the post-and-core interface.

METHOD

Crowns of 72 human similar-sized central upper incisors were removed and roots received a conventional root canal filling prior to establishing 4 groups of core build-up: No Post group (nP) received a 4 mm deep filling made of composite inside the canal with no dental post, fiber post group (FP) received a conventional solid post, and two experimental groups received bundles of 6 (FB6) or 12 (FB12) 0.3 mm thin fiber posts, respectively. Posts were placed adhesively inside the root canal using a dual-curing build-up composite in combination with a self-etch adhesive, the latter was also used for nP group. Upon completion of core build-ups, all teeth received full-ceramic crowns that recreated the original tooth form. Samples were subjected in a 135° angle to thermo-mechanical loading (TML) for 1.2 Mill. chewing cycles followed by static load tests (fracture resistance). Fracture modes as well as intracanal failure modes with respect to failed interfaces were analyzed using optical and electron microscopy (SEM). Microcomputer tomography (μCT) was used to exemplary compare pre and post TML geometries.

RESULTS

Static load test was significantly different between groups (p < 0.0005; Kruskal-Wallistest). Pairwise comparison showed that the nP group (221 ± 103N) failed at significantly lower forces compared to the FP (454 ± 184N), FB6 (477 ± 250N) and FB12 (478 ± 260N) groups (p ≤ 0,001; Mann-Whitney-U-test). Fracture modes were significantly affected by the presence or absence of a post (p ≤ 0,016; Chi-square test) revealing increased incidence of restorable fractures at the cervical region for nP group. Microscopic analysis revealed more intracanal failures at interfaces between post surfaces and composite for solid posts, whereas fiber bundled posts mostly failed at the interfaces between composite and dentin. Micro-CT analysis showed no alterations of the root-post-and-core structure after TML except slight deformations of occasionally entrapped voids.

CONCLUSION

Fracture resistance and fracture modes were significantly affected by the presence or absence of a post, whereas the investigated post groups did not differ from each other. However intracanal failure revealed differences in adhesive failures between solid fiber posts and bundled fiber posts. Deformations of entrapped voids, revealed by micro-Ct analyses after TML, lead to the assumption that applied forces result in alterations in the regions of voids.

Flexural Strength of Resin Core Build-Up Materials: Correlation to Root Dentin Shear Bond Strength and Pull-Out Force

The aims of this study were to investigate the effects of root dentin shear bond strength and pull-out force of resin core build-up materials on flexural strength immediately after setting, after one-day water storage, and after 20,000 thermocycles. Eight core build-up and three luting materials were investigated, using 10 specimens (n = 10) per subgroup. At three time periods-immediately after setting, after one-day water storage, and after 20,000 thermocycles, shear bond strengths to root dentin and pull-out forces were measured. Flexural strengths were measured using a 3-point bending test. For all core build-up and luting materials, the mean data of flexural strength, shear bond strength and pull-out force were the lowest immediately after setting. After one-day storage, almost all the materials yielded their highest results. A weak, but statistically significant, correlation was found between flexural strength and shear bond strength (r = 0.508, p = 0.0026, n = 33). As the pull-out force increased, the flexural strength of core build-up materials also increased (r = 0.398, p = 0.0218, n = 33). Multiple linear regression analyses were conducted using these three independent factors of flexural strength, pull-out force and root dentin shear bond strength, which showed this relationship: Flexural strength = 3.264 × Shear bond strength + 1.533 × Pull out force + 10.870, p = 0.002). For all the 11 core build-up and luting materials investigated immediately after setting, after one-day storage and after 20,000 thermocycles, their shear bond strengths to root dentin and pull-out forces were correlated to the flexural strength in core build-up materials. It was concluded that the flexural strength results of the core build-up material be used in research and quality control for the predictor of the shear bond strength to the root dentin and the retentive force of the post.

Physical and mechanical properties of dual functional cements-an in vitro study

OBJECTIVES

The aim of this study was to evaluate the physical and mechanical properties of different dual functional cements.

MATERIALS AND METHODS

Three dual functional cements (Allcem Core (FGM), Rebilda DC (VOCO), and LuxaCore Z (DMG)), a luting resin cement (Rely X ARC (3 M ESPE)), and a Core Buildup composite resin GrandioSo (VOCO) were used. Flexural strength (n = 10) and film thickness (n = 6) were evaluated according to ISO 4049:2009. Flow (n = 6) was evaluated according to ISO 6876:2001. Degree of conversion (DC) was assessed immediately and 24 h after polymerization (n = 5). For resistance to dislodgment (RD) analysis, bovine teeth were prepared to receive fiber glass posts, and a push-out test (n = 12) was used.

RESULTS

Luxacore Z presented lower flexural strength when compared to GrandioSo (p < 0.001). No statistical difference was found between cements for film thickness (p = 0.66). Reduced flow values were found for Allcem Core (p = 0.006). No statistical difference was found for immediate DC for different cements (p > 0.05). After 24 h, DC increased for all groups, except for Luxacore Z (p = 0.054). The RD did not differ from the control Rely X ARC, regardless of the root third (p > 0.05). Luxacore Z showed lower mean values in the apical third compared to the coronal third (p = 0.046).

CONCLUSIONS

The dual functional cements (Allcem Core and Rebilda DC) possessed similar physical and mechanical properties of luting resin cement (RelyX ARC) and Core Buildup composite resin (GrandioSo). Hence, they could be used for one-stage post and core buildup restorations.

CLINICAL RELEVANCE

The dual functional cements could be used for one-stage post and core buildup restorations since they possess similar physical and mechanical properties of luting resin cements and Core Buildup composite resin.

Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts

Objective

This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC), MultiCore Flow (MCF), and LuxaCore Z-Dual (LCZ)), and a nanohybrid composite, (Tetric N-Ceram (TNC)).

Material and Methods

Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post) cemented with resin cement (Panavia F2.0). Samples were randomly divided into four groups (n=10). Each group was built-up with one of the four core materials following its manufacturers’ instructions. The teeth were embedded in acrylic resin blocks. Nickel-Chromium crowns were fixed on the specimens with resin cement. The fracture resistance was determined using a universal testing machine with a crosshead speed of 1 mm/min at 135⁰ to the tooth axis until failure occurred. All core materials used in the study were subjected to test for the flexural modulus according to ISO 4049:2009.

Results

One-way ANOVA and Bonferroni multiple comparisons test indicated that the fracture resistance was higher in the groups with CPC and MCF, which presented no statistically significant difference (p>0.05), but was significantly higher than in those with LCZ and TNC (p<0.05). In terms of the flexural modulus, the ranking from the highest values of the materials was aligned with the same tendency of fracture loads.

Conclusion

Among the cores used in this study, the composite core with high filler content tended to enhance fracture thresholds of teeth restored with fiber posts more than others.

Microtensile strength of resin cement bond to indirect composite treated by different output powers of Er:YAG laser

The study aimed to evaluate the effect of different output powers of Er:YAG laser on microtensile bonding strength of indirect composite to resin cements.36 indirect composite blocks (GC Gradia DA2, Japan) size 15 × 10 × 10 mm(3) were constructed, and divided into 12 groups, as follows:G1: control group (no treatment); Groups G2 to G6: treated with Er:YAG laser (2,940 nm) in noncontact mode, frequency 20 Hz, pulse duration 470 µs, with output power ranging from 2W to 6W; Groups G7 sandblasting, Groups 8 to G12: as Groups G2 to G 6 with preparatory sandblasting. One specimen from each group was analyzed by SEM; each specimen was fixed to a specialized metal jig using cyanoacrylate (Mitreapel, Beta Kimya San. Ve TIC, Iran) and debonded under tension with a universal testing machine (Zwick, Germany) at a crosshead speed of 0.5 mm min(-1). Sandblasting and laser can improve bond strength above an energy level of 150 mJ. SEM evaluation of laser-treated specimens showed irregularities and deep undercuts. T test analysis showed no significant difference between sandblasted and non-sandblasted group, with laser output power of 0, 100, or 150 mJ (P = 0.666, P = 0.875, and P =  .069); in the specimens irradiated with energy output of 200, 250, or 300 mJ, sandblasted specimens showed higher bond strength than non-sandblasted ones. The results demonstrate that, in composite resin irradiated with laser at energy output of 200-300 mJ, sandblasting might be a suitable procedure to enhance bond strength of resin cement.

A resin composite material containing an eugenol derivative for intracanal post cementation and core build-up restoration

OBJECTIVES

To formulate and evaluate new dual cured resin composite based on the inclusion of eugenyl methacrylate monomer (EgMA) with Bis-GMA/TEGDMA resin systems for intracanal post cementation and core build-up restoration of endodontically treated teeth.

METHODS

EgMA was synthesized and incorporated at 5% (BTEg5) or 10% (BTEg10) into dual-cure formulations. Curing properties, viscosity, Tg, radiopacity, static and dynamic mechanical properties of the composites were determined and compared with Clearfil™DC Core-Plus, a commercial dual-cure, two-component composite. Statistical analysis of the data was performed with ANOVA and the Tukey's post-hoc test.

RESULTS

The experimental composites were successfully prepared, which exhibited excellent curing depths of 4.9, 4.7 and 4.2 mm for BTEg0, BTEg5 and BTEg10 respectively, which were significantly higher than Clearfil™DC. However, the inclusion of EgMA initially led to a lower degree of cure, which increased when measured at 24 h with values comparable to formulations without EgMA, indicating post-curing. The inclusion of EgMA also lowered the polymerization exotherm thereby reducing the potential of thermal damage to host tissue. Both thermal and viscoelastic analyses confirmed the ability of the monomer to reduce the stiffness of the composites by forming a branched network. The compressive strength of BTEg5 was significantly higher than the control whilst flexural strength increased significantly from 95.9 to 114.8 MPa (BTEg5) and 121.9 MPa (BTEg10). Radiopacity of the composites was equivalent to ∼3 mm Al allowing efficient diagnosis.

SIGNIFICANCE

The incorporation of EgMA within polymerizable formulations provides a novel approach to prepare reinforced resin composite material for intracanal post cementation and core build-up and the potential to impart antibacterial properties of eugenol to endodontic restorations.

Are self-adhesive resin cements suitable as core build-up materials? Analyses of maximum load capability, margin integrity, and physical properties

OBJECTIVES

The aim of the present study was to test a self-adhesive resin cement used as core build-up material in comparison to two commercially available core build-up materials.

MATERIALS AND METHODS

Forty human anterior teeth were endodontically treated and fiber post insertion (RelyX Fiber posts) and core build-ups were performed using two core build-up materials applied with an etch-and-rinse adhesive approach (Luxacore Dual-LC and Clearfil Core-CC) and an experimental self-adhesive resin cement (SAR) in two application modes (SAR Handmix and SAR Automix). Samples were subjected to thermo-mechanical loading. Margin integrity was determined using scanning electron microscopy (SEM), and maximum load capability (Fmax) was evaluated. Physical properties of the tested materials were also examined.

RESULTS

Fmax was significantly affected by the core build-up material (p < 0.0005; one-way ANOVA). CC [481 (158) N] revealed significantly higher Fmax compared to LC [226 (80) N], SAR Hand [205 (115), and SAR Automix [197 (134) N] (p < 0.05; Tukey-B). The percentage of margin quality "continuous margin" in enamel after thermo-mechanical loading (TML) differed significantly among groups (p < 0.0005; Kruskal-Wallis); CC demonstrated a significantly higher percentage of margin quality "continuous margin" compared to the other groups. Physical properties were significantly affected by the different core materials (p < 0.0005; ANOVA); CC and LC demonstrated significantly higher flexural strength compared to both SAR groups as well as significantly higher water sorption of both SAR groups compared to CC and LC.

CONCLUSION

Within the limitations of the present in vitro study, we conclude that the investigated experimental self-adhesive resin cement is not suitable as a core build-up material due to the lower maximum load capability, low margin quality, and the data of the mechanical properties.

CLINICAL RELEVANCE

The investigated experimental self-adhesive resin cement cannot be recommended as a core build-up material.

Effect of adhesive system on retention in posts comprising fiber post and core resin

The purpose of this study was to compare the retention of fiber-reinforced composite (FRC) posts luted with either conventional or self-adhesive resin cement. The FRC posts and core resin were built up in bovine teeth. The posts were luted with standard etch-andrinse cement, self-etch cement, or one of two self-adhesive cements. The samples were stored in water for 1 or 14 days or subjected to thermal cycling (TC). Retention value was measured with the pull-out test using a universal testing machine. Conventional adhesive resin cement yielded significantly greater retention than self-adhesive resin cement at 1 day. No significant difference was observed in retention among the adhesive systems tested at 14 days or after TC. During the early luting stage, self-adhesive resin cement yielded lower retention value than conventional resin cement. After 14 days storage or TC, retention was comparable to that with conventional resin cement.

Damage of lithium-disilicate all-ceramic restorations by an experimental self-adhesive resin cement used as core build-ups

OBJECTIVES

This in vitro study aimed to predict the potential of fracture initiation after long-term incubation (LTI) of lithium-disilicate restorations due to a hygroscopic expansion of self-adhesive resin cement (SARC) used as core build-up material.

METHODS

Human maxillary central incisors were divided into four groups (n = 10). Teeth were endodontically treated and decoronated. Specimens were restored in a one-stage post-and-core procedure using experimental dual-curing SARC. Three application protocols to build up the core were compared as follows: I, auto-polymerisation; II, dual curing including 40 s light-initiated polymerisation; and III, an open matrix technique in a dual-curing mode. In group IV, a chemical-curing composite core build-up material served as control. For all specimens, a 2-mm ferrule design was ensured. Full anatomic lithium-disilicate crowns were adhesively luted. One-year LTI in 0.5 % chloramine solution at 37 °C was performed. Restorations were examined after 3, 6, 9 and 12 month of storage. Survival rates were calculated using log-rank statistics (p = 0.05).

RESULTS

Fifty per cent of lithium-disilicate crowns of groups I and II showed visible crack propagation after 9 months of incubation, while one crown failed in group III. No failure was observed in group IV. The survival rates differed significantly (p = 0.017).

CONCLUSION

SARC used to build up the core of severely damaged endodontically treated teeth does have the potential to cause fracture of lithium-disilicate crown restorations.

CLINICAL RELEVANCE

Hygroscopic expansion of self-adhesive resin cements used as a core build-up material might have an adverse impact on longevity of glass-ceramic crowns.

Four-year Survival of Endodontically Treated Premolars Restored with Fiber Posts

The objective of this prospective clinical trial was to investigate the influence of the residual coronal structure of endodontically treated teeth and the type of cement used for luting fiber posts on four-year clinical survival. Two groups (n = 60) were defined, depending on the amount of residual coronal dentin after abutment build-up and final preparation: (1) more than 50% of coronal residual structure; and (2) equal to or less than 50% of coronal residual structure. Within each group, teeth were randomly divided into 2 subgroups (n = 30) according to the material used for luting fiber posts: (A) resin core build-up material, Gradia Core; or (B) self-adhesive universal cement GCem Automix. The rate of success was assessed based on clinical and intra-oral radiographic examinations at the follow-up after 6, 12, 24, 36, and 48 months. The highest 48-month success and survival rates were recorded in group 1A (90% and 100%, respectively), whereas teeth in group 2B exhibited the lowest performance (63.3% success rate, 86.6% survival rate). Cox regression analysis revealed that neither the amount of coronal residual structure nor the luting material significantly influenced the failure risk (p > .05) (ClinicalTrials.gov, NCT01532947).

Fracture Strength and Fracture Patterns of Root-filled Teeth Restored With Direct Resin Composite Restorations Under Static and Fatigue Loading

Aim

To assess fracture strength and fracture patterns of root-filled teeth with direct resin composite restorations under static and fatigue loading.

Methodology

MOD cavities plus endodontic access were prepared in 48 premolars. Teeth were root filled and divided into three restorative groups, as follows 1) resin composite; 2) glass ionomer cement (GIC) core and resin composite; and 3) open laminate technique with GIC and resin composite. Teeth were loaded in a servohydraulic material test system. Eight samples in each group were subjected to stepped fatigue loading: a preconditioning load of 100 N (5000 cycles) followed by 30,000 cycles each at 200 N and higher loads in 50-N increments until fracture. Noncycled teeth were subjected to a ramped load. Fracture load, number of cycles, and fracture patterns were recorded. Data were analyzed using two-way analysis of variance and Bonferroni tests.

Results

Fatigue cycling reduced fracture strength significantly (p&lt;0.001). Teeth restored with a GIC core and a laminate technique were significantly weaker than the composite group (379±56 N, 352±67 N vs 490±78 N, p=0.001). Initial debonding occurred before the tooth underwent fracture. All failures were predominantly adhesive, with subcrestal fracture of the buccal cusp.

Conclusions

Resin composite restorations had significantly higher fracture strength than did other restorations. Fatigue cycled teeth failed at lower load than did noncycled teeth.

Fiber post placement with core build-up materials or resin cements-an evaluation of different adhesive approaches

OBJECTIVE

To compare push-out bond strength of fiber-posts luted with different adhesive approaches to root canal dentin.

MATERIALS AND METHODS

Forty maxillary first incisors were decoronated and endodontically treated. Specimens were randomly distributed into five groups (n = 8) and fiber-posts (DentinPost coated, Komet) were inserted using five different luting materials: etch-and-rinse adhesive systems and corresponding core-and-post material in groups 1 (DentinBond/DentinBuild, Komet) and 2 (XP Bond + SCA/Core-X flow, Densply), self-adhesive resin cements in groups 3 (RelyX Unicem, 3M Espe) and 4 (SmartCem 2, Dentsply) and a self-etch adhesive/resin cement in group 5 (ED-Primer II/Panavia F 2.0, Kuraray). The roots were sectioned into eight 1 mm thick serial slices and within 48 h push-out bond strength was investigated. Statistical analyses were performed using non-parametrical Kruskal-Wallis H-test and Mann-Whitney U-test for differences between experimental groups at p < 0.05. The failure modes were analyzed using Chi square test.

RESULTS

The bond strength [MPa] (mean/min-max) for groups 3 (12.35/3.60-32.44), 4 (13.52/4.48-30.69) and 2 (11.15/5.23-35.58) were significantly higher (p < 0.001) compared to groups 1 (6.66/2.34-24.89) and 5 (7.41/0.28-34.18). Adhesive failure between dentin and luting agent was the most frequent failure mode.

CONCLUSIONS

Bond strength of fiber-posts adhesively luted to root canal dentin was significantly higher when self-adhesive resin cements were used. One (group 2) of the tested core-and-post materials/etch-and-rinse adhesive achieved comparable bond strength values.

Are endodontically treated incisors reliable abutments for zirconia-based fixed partial dentures in the esthetic zone?

INTRODUCTION

This ex vivo pilot study tested the influence of defect extension and quartz-fiber post placement (QFP) on the ex vivo survival rate and fracture resistance of root-treated upper central incisors served as abutments for zirconia 2-unit cantilever fixed partial dentures (2U-FPDs) exposed to 10 years of simulated clinical function.

METHODS

Human maxillary central incisors were endodontically treated and divided into the following 5 groups (n = 8): (1) access cavity filled with core build-up composite, (2) biproximal class III cavities filled as in group 1, (3) specimens restored as in group 2 with QFP placed, (4) specimens decoronated and core buildup as in group 1, and (5) specimens restored as in group 4 but with QFP as in group 3. On all specimens, 2U-FPDs were placed with dual-curing resin cement. In order to simulate 10 years of clinical function, specimens were exposed to thermal cycling and mechanical loading with subsequent loading to failure. Kaplan-Meier curves were constructed, and log-rank tests were performed. Fracture force and patterns were compared by means of Kruskal-Wallis, Mann-Whitney U (post hoc), and Fisher exact tests, respectively (P = .05).

RESULTS

For specimens only with an access cavity, it was observed that 25% had catastrophic tooth fractures and the lowest load-to-fracture values. In all other groups, chipping combined with or without debonding occurred. Groups did not differ significantly regarding the survival rate (P = .603) and fracture patterns (P = .633), but they did for fracture load including technical failures (P = .017).

CONCLUSIONS

After 10 years of simulated clinical function, both defect extension and placement of QFP had no significant influence on survival of root-treated upper central incisors as abutments restored with zirconia-based 2U-FPDs.