The aim was to explore the fracture-behavior, survival and marginal-microgaps within the root-canal of immature anterior teeth restored with different fiber-reinforced post-core composites (FRCs). 180 bovine-incisors were randomly divided into 6 groups (n = 30). One group served as control (group 6). The rest of the teeth were prepared to an internal diameter of 1.6 mm and the apex was sectioned. After application of an MTA-plug, teeth were restored with FRC materials: Group 1: Bioblock technique with short fiber-reinforced composite (SFRC); Group 2: Bioblock technique with flowable SFRC; Group 3: Individually-made FRC post; Group 4: Conventional FRC post; Group 5: dual-cure core build-up composite. After restorations were completed, teeth (n = 5/group) were sectioned and then stained. Specimens were viewed under a stereo microscope and the percentage of microgaps within the root-canal was calculated. Fatigue-survival was measured using a cyclic-loading testing machine in the rest of the specimens. Flowable SFRC application in the root-canal (Group 2) did not differ from intact-teeth regarding fatigue-survival (p > 0.05). The rest of the groups produced significantly lower survival (p < 0.05) compared to intact-teeth. Post/core restorations made from conventional FRC post (Group 4) exhibited a high number of microgaps (38.3%) at the examined interphase in the root-canal. The restoration of immature incisors with the use of flowable SFRC as post-core material displayed promising performance in a matter of fatigue-resistance and survival.

ObjectiveThe purpose was to evaluate the crack formation associated with different direct restorative procedures of the utilized resin composites (RC) right after and 1 week later of the restoration. Materials and methods Eighty intact, crack-free third molars with standard MOD cavities were included in this in vitro study and randomly divided into four groups of 20 each. After adhesive treatment, the cavities were restored either with bulk (group 1) or layered (group 2) short-fiber-reinforced resin composites (SFRC); bulk-fill RC (group 3); and layered conventional RC (control). Right after the polymerization and a week later, crack evaluation on the outer surface of the remaining cavity walls was performed with a transillumination method utilizing the D-Light Pro (GC Europe) with the "detection mode." Between-and within-groups comparisons Kruskal-Wallis and Wilcoxon tests were used, respectively. Results Post-polymerization crack evaluation showed significantly lower crack formation in SFRC groups compared to the control (p<0.001). There was no significant difference within SFRC groups and non-SFRC groups (p=1.00 and p=0.11, respectively). Within group comparison revealed significantly higher number of cracks in all groups after 1 week (p≤0.001), however, only the control group differed significantly from all the other groups (p≤0.003). Conclusions Post-polymerization shrinkage induced further crack formation in the tooth 1 week after the restoration. SFRC was less prone to shrinkage-related crack formation during the restorative procedure; however, after 1 week, besides SFRC, bulk-fill RC also showed less prone to polymerization shrinkage-related crack formation than layered composite fillings. Clinical relevance SRFC can decrease the shrinkage stress-induced crack formation 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.

Bevezetés: Kutatásunkban arra kerestük a választ, hogy két eltérő töméstechnika esetében van-e különbség a rövidüvegszál megerősítésű kompozit (short fiber-reinforced composite, SFRC) tömőanyag zsugorodása miatt kialakult repedésekszámában.Anyag és módszer: Két csoportban, 20-20 extrahált bölcsességfogba standardizált nagyságú MOD üreget preparáltunk,majd a fogakat az alábbiak szerint restauráltuk SFRC-vel: 1. csoportnál bulk, rétegzés nélküli technikával, 2. csoportbanpedig ferde rétegzéssel 2 mm vastag rétegekben. Mindegyik minta esetén az SFRC-t 1 mm kompozittal fedtük.A tömés elkészítését követően D-Light Pro lámpával megvizsgáltuk a fogzománcot, és a keletkezett repedések számátrögzítettük. Az összrepedésszámot egy hét elteltével is rögzítettük.Eredmények: A két töméstechnika között az eltérés nem szignifikáns a repedésszám tekintetében. 1 héttel későbba bulk, rétegzés nélküli csoportban 4,95 (340%-os növekedés), a rétegzéses csoportban 4,30 (410%-os növekedés) voltaz átlagos repedésszám. Ez a korábbi adatokhoz képest szignifikáns eltérés (p = 0,000). A két töméstechnika közötta végső összrepedésszám tekintetében nem tapasztaltunk szignifikáns eltérést.Következtetések: SFRC anyag esetén a vizsgált két töméstechnikával közel azonos mértékű repedésképződés jönlétre, és mindkét esetben jelentősen megnő a repedések száma a posztpolimerizációs időszakban.