The innovation of nanocellulose as reinforcement filler in composites has been a topic of interest in the development of new biomaterials. The objective of this study was to investigate the mechanical properties of a nanohybrid dental composite made of rice husk silica and loaded with different percentages of kenaf nanocellulose. Kenaf cellulose nanocrystals (CNC) were isolated and characterized using a transmission electron microscope (TEM) (Libra 120, Carl Zeiss, Germany). The experimental composite was fabricated with fiber loadings of 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 6 wt% silane-treated kenaf CNC, and subjected to a flexural and compressive strength test (n = 7) using an Instron Universal Testing Machine (Shimadzu, Kyoto, Japan), followed by a scanning electron microscopic assessment of the flexural specimen’s fracture surface using a scanning electron microscope (SEM) (FEI Quanta FEG 450, Hillsborough, OR, USA). Commercial composites Filtek Z350XT (3M ESPE, St. Paul, MN, USA), Neofil (Kerr Corporation, Orange, CA, USA) and Ever-X Posterior (GC Corporation, Tokyo, Japan) were used as a comparison. The average diameter of kenaf CNC under TEM was 6 nm. For flexural and compressive strength tests, one-way ANOVA showed a statistically significant difference (p < 0.05) between all groups. Compared to the control group (0 wt%), the incorporation of kenaf CNC (1 wt%) into rice husk silica nanohybrid dental composite showed a slight improvement in mechanical properties and modes of reinforcement, which was reflected in SEM images of the fracture surface. The optimum dental composite reinforcement made of rice husk was 1 wt% kenaf CNC. Excessive fiber loading results in a decline in mechanical properties. CNC derived from natural sources may be a viable alternative as a reinforcement co-filler at low concentrations.

Objective This study aimed to investigate the effect of relining prefabricated fiber-reinforced composite (FRC) posts using bulk-fill, flowable, discontinuous short fiber-reinforced composite (SFRC) on intracanal adaptation in weakened endodontically-treated premolar teeth. Materials and Methods Forty extracted human premolar teeth were selected and randomly allocated to five groups (n = 8) according to the canal preparation method and restorative technique after endodontic treatment: Group 1 (control): nonflared, closed apex root canals; group 2, 4: flared, open-apex root canals; group 3, 5: flared, closed apex root canals. Groups 1 to 3 were restored with standard RelyX fiber post size #1, while groups 4 and 5 were restored with customized RelyX fiber post size #1 and relined with bulk-fill flowable SFRC (everX Flow, GC, Tokyo, Japan). To evaluate intracanal adaptation, the empty root of each sample with the corresponding fiber post (standard or customized) inserted was measured twice using a micro-digital scale and the average value was calculated. The post was then removed, followed by the insertion of a light body polyvinyl siloxane (PVS) impression material into the canal, followed by reinsertion of the post and removal of excess material once the PVS was set. Finally, the sample weight was recorded, and the data were analyzed using one-way analysis of variance and the Bonferroni post hoc test (p-value = 0.05). Results A statistically significant difference (p < 0.05) in PVS material weight was identified between the groups. Group 1 (control) had the lightest weight of PVS material, followed by groups restored with customized fiber posts (groups 4 and 5) and standard fiber posts (groups 2 and 3). Conclusion Anatomically-customized fiber posts with bulk-fill flowable SFRC provided better intracanal adaptation compared with standard fiber posts in teeth with compromised root canals.

This study aimed to compare the difference in marginal dye penetration between everStick, Parapost XP, Parapost fiber white and control groups under gradual loading. Sixty-eight human maxillary permanent incisors were divided into four groups. Each specimen was endodontically treated with step-back technique and prepared for each post system according to experimental groups, subsequently cemented in the canal. Composite resin cores were built and laboratory fabricated metal crowns were cemented. All specimens except those in the control group were subjected to thermal cycling. All groups were subjected to gradual loading from 0N-50N for 100 cycles. Specimens were sectioned transversely and the depths of dye penetration along the post were measured. Data were entered in SPSS ver. 22 and analyzed using two-way ANOVA test. There was no significant difference in marginal dye penetration between each group (p-value>0.05). However, there was a significant difference in percentage of marginal dye penetration between all groups (p-value<0.05); post-hoc comparison showed significant difference between Fiber White and Control groups (p-value=0.009). All the groups showed dye penetration but the percentage was significant only between Parapost Fiber White and the control groups.

Polyamide12 (PA12) has been used to fabricate flexible dentures for patients with prominent undercuts. It has a high moulding property, enabling it to take the shape of the canal without forming any voids, hence a suitable canal space restorative material. This study aims to investigate the chemicomechanical properties of PA12 composite reinforced with crystalline nanocelluloses (CNC) from oil palm fibre (OPF) and rice husk (RH) silica compared to commercial posts. Treated silica from RH and CNC from OPF were incorporated into the PA12 matrix to obtain the samples. Six 1.5 mm × 2 mm × 2.5 mm samples were prepared for seven groups. The flexure test, Fourier-transform infrared spectroscopy, and scanning electron microscopy (SEM) were employed during sample evaluations. A statistically notable variation in flexural strength among the sample groups [χ2 (df) = 38.65 (6)] was observed. The PA12 with CNC fillers recorded increased flexure strength than its unfilled counterpart and no significant difference with the commercial post. The SEM results confirmed the presence of both fillers in the composite. Smoother surfaces with fewer voids and gaps were observed with filler weight percentage (wt%) increments, suggesting enhanced interfacial bonding. Incorporating CNC into the PA12 matrix increased the flexural strength of the composite, whereas silica reduced it. Therefore, within the limitations of this study, new PA12 composites reinforced with CNC fillers from OPF biowastes could be a promising alternative for dental posts. However, additional research is needed to fully assess their viability.