The influence of customization of glass fiber posts on fracture strength and failure pattern: A systematic review and meta-analysis of preclinical ex-vivo studies

Effects of a relined fiberglass post with conventional and self-adhesive resin cement

Objectives

This study was conducted to evaluate the mechanical properties of relined and non-relined fiberglass posts when cemented to root canal dentin using a conventional dual-cure resin cement or a self-adhesive resin cement.

Materials and Methods

Two types of resin cements were utilized: conventional and self-adhesive. Additionally, 2 cementation protocols were employed, involving relined and non-relined fiberglass posts. In total, 72 bovine incisors were cemented and subjected to push-out bond strength testing (n = 10) followed by failure mode analysis. The cross-sectional microhardness (n = 5) was assessed along the root canal, and interface analyses (n = 3) were conducted using scanning electron microscopy (SEM). Data from the push-out bond strength and cross-sectional microhardness tests were analyzed via 3-way analysis of variance and the Bonferroni post-hoc test (α = 0.05).

Results

For non-relined fiberglass posts, conventional resin cement exhibited higher push-out bond strength than self-adhesive cement. Relined fiberglass posts yielded comparable results between the resin cements. Type II failure was the most common failure mode for both resin cements, regardless of cementation protocol. The use of relined fiberglass posts improved the cross-sectional microhardness values for both cements. SEM images revealed voids and bubbles in the incisors with non-relined fiberglass posts.

Conclusions

Mechanical properties were impacted by the cementation protocol. Relined fiberglass posts presented the highest push-out bond strength and cross-sectional microhardness values, regardless of the resin cement used (conventional dual-cure or self-adhesive). Conversely, for non-relined fiberglass posts, the conventional dual-cure resin cement yielded superior results to the self-adhesive resin cement.

Evaluation of bond strength in customizing fiber post using translucent resins photoactivated by different light-emitting diodes

Aims

The objective of the study was to evaluate two translucent resin composite systems for customizing light-polymerized fiber posts with light-emitting diode (LED) curing units regarding adhesion using conventional cement at 24 h and 6 months.

Settings and Design

This was an experimental in vitro study.

Methods

Forty roots were prepared and divided into four groups (n = 10): ZV-Z350 resin and LED Valo; ZR-Z350 resin and LED Radii-Cal; OV-Opallis resin and LED Valo; and OR-Opallis resin and LED Radii-Cal. The fiber post was customized and cemented with conventional resin cement and was photoactivated by two different sources.

Statistical Analysis Used

The data were subjected to two-way ANOVA and Tukey's post hoc tests (P = 0.05). The data regarding the pattern of adhesive failures were described in terms of the frequency of occurrence in each third of the postspace.

Results

Both at 24 h and 6 months, bond strength among groups was similar, regardless of the analyzed postspace 3rd (P > 0.05). Adhesive failure Type 4 was the most frequent in all thirds.

Conclusions

Customizing the fiber post with Z350 and Opallis has the same effect on bond strength and adhesive failure pattern, regardless of the LED curing units used for photopolymerization.

Comparative analysis of stress distribution in residual roots with different canal morphologies: evaluating CAD/CAM glass fiber and other post-core materials

BACKGROUND

The selection of post-core material holds significant importance in endodontically treated teeth, influencing stress distribution in the dental structure after restoration. The use of computer-aided design/computer-aided manufacturing (CAD/CAM) glass fiber post-core possesses a better adaptation for different root canal morphologies, but whether this results in a more favorable stress distribution has not been clearly established.

MATERIALS AND METHODS

This study employed finite element analysis to establish three models of post-core crown restoration with normal, oversized, and dumbbell-shaped root canals. The three models were restored using three different materials: CAD/CAM glass fiber post-core (CGF), prefabricated glass fiber post and resin core (PGF), and cobalt-chromium integrated metal post-core (Co-Cr), followed by zirconia crown restoration. A static load was applied and the maximum equivalent von Mises stress, maximum principal stress, stress distribution plots, and the peak of maximum displacement were calculated for dentin, post-core, crown, and the cement acting as the interface between the post-core and the dentin.

RESULTS

In dentin of three different root canal morphology, it was observed that PGF exhibited the lowest von Mises stresses, while Co-Cr exhibited the highest ones under a static load. CGF showed similar stress distribution to that of Co-Cr, but the stresses were more homogeneous and concentrated apically. In oversized and dumbbell-shaped root canal remnants, the equivalent von Mises stress in the cement layer using CGF was significantly lower than that of PGF.

CONCLUSIONS

In oversized root canals and dumbbell-shaped root canals, CGF has shown good performance for restoration of endodontically treated teeth.

CLINICAL RELEVANCE

This study provides a theoretical basis for clinicians to select post-core materials for residual roots with different root canal morphologies and should help to reduce the occurrence of complications such as root fracture and post-core debonding.

Influence of using different translucent composite resins for customizing fiber post on the bond strength of self-adhesive cement to root dentin

This study evaluated the influence of different translucent resins (Z350 and Opallis) for customizing fiber posts and light-curing the cementation system using different LED equipment (V, Valo or R, Radii-Cal) on the bond strength and adhesive failure pattern at 24 h and 6 months. Eighty roots were prepared and divided into 4 groups (n=20): ZV (Z350 resin and LED Valo), ZR (Z350 resin and LED Radii-Cal), OV (Opallis resin and LED Valo), OR (Opallis resin and LED Radii-Cal). After post space preparation, the fiber post was customized and cemented with self-adhesive cement and light-curing using V or R LED equipment. Bond strength values were submitted to 2-way ANOVA test. ZV and ZR showed higher bond strength values than the other groups at 6 months of evaluation (p<0.05). The Z350 resin has a favorable influence on the bond strength of self-adhesive cement to root dentin, regardless of the LED polymerization equipment used.

Internal adaptation and mechanical properties of CAD/CAM glass fiber post-cores in molars: An in vitro study

OBJECTIVE

The purpose of this in vitro study was to evaluate the internal adaptation, fracture resistance, and fracture pattern of the residual roots and crowns of molars restored with computer-aided design/computer-aided manufacturing (CAD/CAM) glass fiber post-cores, and compare them with three other post-core restorations.

MATERIALS AND METHODS

We selected 32 extracted maxillary first molars and divided them into four groups according to the post-core system: traditional casting titanium (Ti) post-cores (TC group); Ti post-cores fabricated with selective laser melting (SLM group); CAD/CAM glass fiber post-cores of the split type (CCS group); and prefabricated glass fiber posts and composite resin cores (PF group). The internal adaptation was analyzed with microcomputed tomography. Teeth were restored with monolithic zirconia crowns and subjected to thermocycling and cyclic loading. A load was applied consistently along the long axis of the tooth until fracture to record the fracture resistance and pattern. For the statistical analysis, one- and two-way analyses of variance, Tukey's post hoc and chi-square tests were performed to compare the differences among the groups.

RESULTS

The CCS, TC, and SLM groups exhibited similar internal adaptations across all sections (P < 0.05). The FP group showed good fit with the root canals in the apical and middle sections but a poor fit with those in the cervical section. The fracture resistance was higher in the CCS, TC, and SLM groups compared to the PF group (P < 0.05). The proportions of restorable fractures in the CCS and PF groups were 62.5% and 50%, respectively. Unrestorable fractures were more frequent in the TC and SLM groups at frequencies of 100% and 87.5%, respectively.

CONCLUSION

The internal adaptation and fracture resistance of the CCS group were similar to those of the TC and SLM groups, and the fracture pattern was mostly restorable, thus meeting the clinical requirements for molar post-core restorations.

CLINICAL SIGNIFICANCE

CCS can be used to restore residual roots and crowns of molars and exhibit high efficacy in terms of adaptability and mechanical properties. More studies are required to evaluate the effectiveness of CCS.

Present status and future directions: The restoration of root filled teeth

This narrative review will focus on a number of contemporary considerations relating to the restoration of root filled teeth and future directions for research. Clinicians are now more than ever, aware of the interdependence of the endodontic and restorative aspects of managing root filled teeth, and how these aspects of treatment are fundamental to obtaining the best long-term survival. To obtain the optimal outcomes for patients, clinicians carrying out endodontic treatment should have a vested interest in the restorative phase of the treatment process, as well as an appreciation for the structural and biomechanical effects of endodontic-restorative procedures on restoration and tooth longevity. Furthermore, the currently available research, largely lacks appreciation of occlusal factors in the longevity of root filled teeth, despite surrogate outcomes demonstrating the considerable influence this variable has. Controversies regarding the clinical relevance of minimally invasive endodontic and restorative concepts are largely unanswered with respect to clinical data, and it is therefore, all too easy to dismiss these ideas due to the lack of scientific evidence. However, conceptually, minimally invasive endodontic-restorative philosophies appear to be valid, and therefore, in the pursuit of improved clinical outcomes, it is important that the efficacies of these treatment protocols are determined. Alongside an increased awareness of the preservation of tooth structure, developments in adhesive bonding, ceramic materials and the inevitable integration of digital dentistry, there is also a need to evaluate the efficacy of new treatment philosophies and techniques with well-designed prospective clinical studies.

CAD-CAM glass fiber compared with conventional prefabricated glass fiber posts: A systematic review

STATEMENT OF PROBLEM

A prefabricated glass fiber post provides esthetic and biomechanical benefits for severely damaged endodontically treated teeth; however, failures in post retention remain a challenge.

PURPOSE

The purpose of this systematic review was to compare the fracture resistance and bond strength of prefabricated glass fiber posts to those made with computer-aided design and computer-aided manufacturing (CAD-CAM).

MATERIAL AND METHODS

This review was entered into PROSPERO (CRD42020213668) and was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic systematic searches of PubMed/MEDLINE, Embase, and the Cochrane Library were conducted for published articles until October 2020. Studies that compared prefabricated glass fiber posts with CAD-CAM-fabricated glass fiber posts were selected, and studies that had not been published in English or in the previous 10 years were excluded. The fracture resistance (N) and bond strength (MPa) were the primary outcomes.

RESULTS

After reviewing the title, abstract, and the entire text of 227 articles, 8 studies were selected. Four studies were omitted. Four of the 8 studies were retained for qualitative analyses, with 1 having a high risk of bias and 3 having a medium risk of bias. Only 1 study found significantly higher fracture resistance in the CAD-CAM group than in the prefabricated group. The bond strength study reported a significant difference, with the CAD-CAM group having greater bond strength than the prefabricated group.

CONCLUSIONS

Despite the high heterogeneity and the few included articles, a tendency was found for the CAD-CAM-fabricated glass fiber post to improve fracture resistance and bond strength. However, the available literature is insufficient to draw definitive conclusions.

Finite element and in vitro study on biomechanical behavior of endodontically treated premolars restored with direct or indirect composite restorations

Objectives of the study were to investigate biomechanical properties of severely compromised premolars restored with composite restorations using finite element analysis (FEA), and in vitro fracture resistance test. A 3-D model of an endodontically treated premolar was created in Solidworks. Different composite restorations were modelled (direct restoration-DR; endo-crown-EC; post, core, and crown-C) with two different supporting tissues: periodontal ligament/alveolar bone (B), and polymethyl methacrylate (PMMA). Models were two-point axially loaded occlusally (850 N). Von Mises stresses and strains were calculated. The same groups were further tested for static fracture resistance in vitro (n = 5, 6.0 mm-diameter ball indenter, vertical load). Fracture resistance data were statistically analyzed (p < 0.050). The highest stresses and strains in all FEA models were observed on occlusal and vestibular cervical surfaces, corresponding to fracture propagation demonstrated in vitro. C showed the lowest stress in dentin, while EC showed lower stresses and strains in crown cement. B models demonstrated larger high stress areas in the root than PMMA models. No significant differences in fracture resistance (N) were observed between groups (DR: 747.7 ± 164.0, EC: 867.3 ± 108.1, C: 866.9 ± 126.3; p = 0.307). More conservative restorations seem a feasible alternative for endodontically treated premolars to conventional post-core-crown.

A Review on Synthetic Fibers for Polymer Matrix Composites: Performance, Failure Modes and Applications

In the last decade, synthetic fiber, as a reinforcing specialist, has been mainly used in polymer matrix composites (PMC’s) to provide lightweight materials with improved stiffness, modulus, and strength. The significant feature of PMC’s is their reinforcement. The main role of the reinforcement is to withstand the load applied to the composite. However, in order to fulfill its purpose, the reinforcements must meet some basic criteria such as: being compatible with the matrix, making chemical or adhesion bonds with the matrix, having properties superior to the matrix, presenting the optimal orientation in composite and, also, having a suitable shape. The current review reveals a detailed study of the current progress of synthetic fibers in a variety of reinforced composites. The main properties, failure modes, and applications of composites based on synthetic fibers are detailed both according to the mentioned criteria and according to their types (organic or inorganic fibers). In addition, the choice of classifications, applications, and properties of synthetic fibers is largely based on their physical and mechanical characteristics, as well as on the synthesis process. Finally, some future research directions and challenges are highlighted.