Excessive cavity preparation and root canal treatment leads to a weakened tooth structure with a lower resistance to fracture. Fiber reinforcement is frequently used to reinforce such teeth, and multiple fiber types and possible applications exist. Various methods for utilizing long fibers to internally splint the remaining cavity walls in the case of large mesio-occluso-distal (MOD) cavities have been proposed; however, no summary of their performance has been written up to now. Our study aims to review the available literature to evaluate and compare the mechanical performance of the different materials and methods utilized for horizontal splinting in large MOD cavities. Three independent authors performed a thorough literature search using PubMed, ScienceDirect, and Google Scholar up until January 2022. The authors selected in vitro studies that used long fibers placed horizontally in posterior teeth with large MOD cavities to reinforce these teeth. From 1683 potentially relevant articles, 11 publications met our inclusion criteria. Seven out of eleven studies showed that horizontal splinting with long fibers improved the fracture resistance of the restored teeth. Three articles showed no significant difference between the fracture resistance of the restored groups. Only one article reported a lower fracture resistance to the horizontally splinted group, compared to conventional direct composite restoration. Within the limitations of this review, evidence suggests that long fiber reinforcement could be used to improve the fracture resistance of heavily restored teeth.

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.

This study aimed to evaluate the nanomechanical surface properties and water uptake of a flowable short-fiber-reinforced composite (SFRC) using various restorative techniques in order to assess its potential as a standalone restorative material. Nanoindentation and compressive creep testing were employed to characterize material performance. Three resin composites were examined: a flowable SFRC (everX Flow), a bulk-fill particulate filler composite (PFC), and a conventional PFC. Five experimental groups were established based on the restorative technique: layered PFC, layered SFRC, bulk SFRC, bulk PFC, and a bi-structure combining SFRC and PFC. Ninety standardized specimens (n = 18/group) were fabricated. Static and creep nanoindentation tests were conducted to assess surface properties, and water uptake was measured over a 30-day period. Data were analyzed using one-way ANOVA and Bonferroni post hoc tests. Nanoindentation revealed significant differences in hardness, with bulk PFC exhibiting the lowest values (p < 0.001). Creep testing indicated changes in modulus and viscosity following water storage. Notably, bulk SFRC showed the lowest water absorption (p < 0.001). Overall, bulk-applied SFRC demonstrated favorable nanomechanical properties and reduced water uptake, demonstrating its suitability as a standalone restorative material. Further clinical investigations are recommended to validate its long-term performance.

The aim of this study was to evaluate crack formation associated with different direct restorative procedures at various time points. This in vitro study included 100 intact third molars with standardized MOD cavities, divided into five groups (n = 20). After adhesive treatment, the cavities were restored as follows: bulk-fill flowable short fiber-reinforced composite (SFRC) (Group 1); conventional flowable resin composite (RC) base and bulk-fill flowable SFRC (Group 2); polyethylene fibers embedded in flowable RC and bulk-fill flowable SFRC (Group 3); flowable SFRC combined with packable SFRC (Group 4); and layered conventional packable RC (control). The presence and orientation (vertical/horizontal) of tooth cracks after restoration were evaluated using the D-light Pro (GC Europe) in "detection mode." Cracks were examined at three distinct time points: immediately, after one week, and after five weeks of water storage. The Kruskal-Wallis and Dwass-Steel-Critchlow-Fligner tests were used for between- and within-group comparisons, respectively. No statistically significant difference in overall crack formation was observed between the groups immediately after the restorative procedure. At the one-week and five-week evaluations, the control group exhibited a significantly higher number of cracks compared to Groups 1-3 (p < 0.01). All groups demonstrated a significantly higher number of cracks at the five-week evaluation compared to the immediate assessment (p < 0.05). The SFRC groups predominantly showed horizontal cracks at all time points. In the 5-week period of water storage following polymerization, the number of cracks appearing on the tooth gradually increased, but the flowable SFRC inserted using the bulk technique was able to moderate the phenomenon in MOD cavities.

Elasticity and stress absorption are present in many different materials in our daily life. Understanding how materials behave under pressure (whether that is constant or dynamic), and how and when they deform can be fundamental in terms of their success or longevity. Elastic behaviour is present in many different forms in different materials, e.g.: meats or other food. Interestingly, elasticity is also a major issue in the oral cavity, when talking about healthy dental tissues, such as dentin or even special dental restorative materials. The article focuses on the general mechanical behaviour of elastic and viscoelastic materials and measurements performed on them.

Restoring deep, extensive carious lesions and subgingival situations can be challenging due to difficulties in placing matrices and achieving isolation. This article describes a technique utilizing individually designed digital matrices for challenging cases, offering an alternative solution aiding the reconstruction of the missing dental structures. Three cases are presented with difficult subgingival cavities or severe destruction of dental hard tissues, where a custom-made matrix was used to bridge the challenges of matrix placement and isolation. Digital impressions of dental arches were taken, and custom-made metal instruments were manufactured through computer-aided design and subsequent sintering. These instruments aided the elevation of deep margins and the reconstruction of the teeth. The presented technique yielded favorable results in terms of accuracy and feasibility for these challenging cases. However, it should be noted that the procedure requires additional time and incurs costs for the necessary elements.