Fracture Resistance of Fiber-Reinforced Composite Restorations: A Systematic Review and Meta-Analysis

Effect of Glass Fiber Reinforcement on Marginal Microleakage in Class II Composite Restorations: An In Vitro Pilot Study

Background: Polymerization shrinkage of composite resins affects the marginal closure of direct dental restorations. It is responsible for developing secondary caries and indirectly affects the survival rate of restorations. This study aims to investigate the null hypothesis, which states that there are no significant differences in the marginal microleakage of Class II restorations when examined in vitro using different dental adhesives, whether the restoration material used is a composite with glass fiber reinforcement or not. Methods: Class II cavities were prepared on both proximal surfaces of thirty-six extracted human molars. A single-component (Universal VivaPen) and a two-component (Futurabond DC) self-etch adhesive system were used for the restorations in the control group (Charisma Classic) and the experimental group (Charisma Classic with Interlig glass fiber strip). An oblique layering technique and a 40-s soft-start light-curing polymerization were used. After selective pre-isolation, the specimens were placed in a 0.2% methylene blue solution and incubated at 37 °C for 24 h. The teeth were sectioned in the mesiodistal direction, and two examiners examined and graded the extent of dye penetration. Statistical analysis was conducted using the Mann-Whitney U and chi-square tests (p < 0.05). Results: All the composite restorations reinforced with glass fiber showed significantly reduced dye infiltration compared to the control group (p < 0.05). A significant difference (p < 0.05) was also observed between the two adhesives. Conclusions: The null hypothesis was rejected. Glass fiber strips significantly reduced composite restoration microleakage regardless of the adhesive. The marginal fit of the restoration was also influenced by the adhesive system used.

Comparative evaluation of marginal adaptation and fatigue resistance of endodontically treated premolars restored with direct and indirect coronal restorations: an in vitro study

BACKGROUND

An optimum restoration for reconstructing endodontically treated teeth should provide excellent marginal adaptation, high fracture resistance as well as maximum tooth structure conservation. The purpose of this study was to evaluate the marginal adaptation and fatigue resistance of different coronal restorations in endodontically treated premolars.

METHODS

Thirty sound maxillary first premolars were endodontically treated and received MOD cavities. Teeth were randomly allocated into three groups (n = 10) according to the type of coronal restoration: Group R: polyethylene fibers (ribbond), fibers-reinforced composite (everX posterior) and final layer of nano-hybrid composite. Group O: indirect lithium disilicate overlay and Group C: fiber-post, resin composite restoration, and lithium disilicate crown. Marginal gap assessment was performed before and after thermocycling (5000 cycles) using stereomicroscope. Samples were subjected to stepwise-stress loading starting at 200 N, and increased by 100 N in each step until failure occurred. Statistical analysis was done by One-way ANOVA followed Tukey`s Post Hoc test for multiple comparison. Paired t test was used to compare the marginal adaptation before and after thermocycling. Survival probability was evaluated by Life table survival analysis. Failure mode analysis was performed with Chi-square test.

RESULTS

Marginal gap was significantly the lowest in group R (37.49 ± 5.05) and (42.68 ± 2.38), while being the highest in group C (59.78 ± 5.67) and (71.52 ± 5.18) in before and after thermocycling respectively (P < 0.0001). Fatigue resistance was the highest for group O (1310.8 ± 196.7), and the lowest for group R (905.4 ± 170.51) with a significant difference between groups (P < 0.0001). Crown group had the highest percentage (80%) of catastrophic failure, while, overlay group exhibited the lowest (20%).

CONCLUSIONS

Direct restoration without cuspal coverage using ribbon fibers with short FRC provided better marginal adaptation than indirect overlays and crowns, but fatigue resistance wasn't significantly improved. Adhesive ceramic overlays showed the best fatigue performance and the least catastrophic failure rate compared to both direct fiber-reinforced composite and indirect ceramic full coverage restorations.

CLINICAL SIGNIFICANCE

Indirect adhesive overlays are a suitable, more conservative restorative option for endodontically treated teeth than full coverage restorations, especially when tooth structure is severely compromised.

Szabó V, Szabó B, Vincze-Bandi E, Braunitzer G, Lassila L, Vallittu P, Garoushi S, Fráter M. Mechanical Performance of Extensive Restorations Made with Short Fiber-Reinforced Composites without Coverage: A Systematic Review of In Vitro Studies

In recent years, composite resin materials have been the most frequently used materials for direct restorations of posterior teeth. These materials have some clinically relevant limitations due to their lack of fracture toughness, especially when used in larger cavities with high volume factors or when utilized as direct or indirect overlays or crown restorations. Recently, short-fiber-reinforced composite materials have been used in bi-structure restorations as a dentine substituting material due to their superior mechanical properties; however, there is no scientific consensus as to whether they can be used as full restorations. The aim of our review was to examine the available literature and gather scientific evidence on this matter. Two independent authors performed a thorough literature search using PubMed and ScienceDirect up until December 2023. This study followed the PRISMA guidelines, and the risk of bias was assessed using the QUIN tool. The authors selected in vitro studies that used short-fiber-reinforced composite materials as complete restorations, with a conventional composite material as a comparison group. Out of 2079 potentially relevant articles, 16 met our inclusion criteria. All of the included studies reported that the usage of short-fiber-reinforced composites improved the restoration's load-bearing capacity. Fifteen of the included publications examined the fracture pattern, and thirteen of them reported a more favorable fracture outcome for the short-fiber-reinforced group. Only one article reported a more favorable fracture pattern for the control group; however, the difference between groups was not significant. Within the limitations of this review, the evidence suggests that short-fiber-reinforced composites can be used effectively as complete restorations to reinforce structurally compromised teeth.