Dental materials journal最新文献

The objective of this study was to investigate the effects of repetitive removal/insertion and a load equivalent to the occlusal force on the retentive force of rest plate-I bar (RPI) clasps fabricated by selective laser melting (SLM) on powder bed fusion. RPI clasp fabricated by SLM and casting were evaluated to the retentive force by repetitive removal/insertion (SLM-RI and Cast-RI), and the retentive force of RPI clasp by SLM was also evaluated by repetitive removal/insertion under load (SLM-L). SLM-RI group was kept superior retentive force during repetitive removal/insertion than Cast-RI group. SLM-L group showed the decrease of retentive force, and all specimens fractured during less than 7,000 repetitive removal/insertion. In SLM-L, the fracture of RPI clasp occurred at minor connector due to stress concentration. In conclusion, the RPI clasp by SLM demonstrated the superior retentive force and fitting for repetitive removal/insertion, yet improvements were necessary to withstand a load equivalent to occlusal force.

This study aimed to evaluate the shape reproducibility of retentive devices made of cast titanium. Retention beads were placed on wax patterns for frameworks of composite resin-veneered restoration using four bead adhesives. The wax patterns were invested in the magnesia-based material and titanium was cast using two different casting machines. The percentage of reproduced retentive devices were evaluated using imaging software. Cast specimens were sliced and concavity was evaluated. The contact angle between the wax surface and adhesives was determined with a contact angle meter. The reproducibility of retentive devices was not influenced by the type of adhesive for both machines. Reproducibility, however, was better for castings fabricated by a one-chamber machine with the use of two adhesives. Although the contact angle to wax material of adhesives varied considerably, reproducibility and concavity of retentive devices of titanium castings were guaranteed with the combination of two machines and four bead adhesives.

This study evaluated the effects of two polishing systems, OptraGloss (G; one-step) and OptiDisc (D; multi-step), on surface roughness (SR), contact angle (CA), surface free energy (SFE), and bacterial adhesion on three single-shade composite resins: Omnichroma (O), ZenChroma (Z), and Charisma Diamond One (C). Data for SR, CA, SFE, and adhesion of Streptococcus mutans (S. mutans) and Streptococcus mitis (S. mitis) were analyzed using one-way ANOVA, Tukey post-hoc tests, and Pearson correlation (α=0.05). Multi-step polishing groups (OD, ZD, and CD) exhibited significantly lower SR (0.18, 0.18, and 0.29 µm, respectively) compared to OG (0.46 µm), ZG (0.30 µm), and CG (0.44 µm) (p<0.05). The highest CA was observed in ZG (91.6º). S. mitis adhesion was greater than S. mutans in all groups except OG. A significant correlation was observed between SR and the adhesion of S. mutans (r=0.693, p<0.001). Polishing systems applied to single-shade composite resins did not impact the SFE but affected SR, and bacterial adhesion.

This study investigated the effect of rosmarinic acid (RA) on the immediate microtensile bond strength (µTBS) of 1-step self-etch adhesive to artificial caries-affected dentine (CAD), with or without NaOCl treatment. Dentine surfaces of 60 premolars were subjected to pH-cycling for artificial caries induction. Samples were randomly categorized into: NaOClRA group treated with 6% NaOCl and RA, RA group treated with RA solution, NaOCl group treated with 6% NaOCl, and untreated control group. Surface morphology was evaluated using SEM. Following bonding and composite placement, the specimens were sectioned into 1 mm² beams after 24 h of water storage, then µTBS test was done. Failure modes were assessed under stereomicroscope. There was significant increase in the µTBS of NaOClRA compared to NaOCl group (p=0.001). RA group showed significant increase in µTBS compared to NaOCl and control groups, (p<0.001, p=0.009 respectively). In conclusion, RA improved the µTBS to CAD with or without NaOCl treatment.

This study investigated the impact of combining human umbilical cord mesenchymal stem cells (hUC-MSCs) with concentrated growth factor (CGF) on regenerating necrotic pulp. Ten-month-old male Bama miniature pigs were divided into control and caries groups. The experimental teeth were randomly divided into three groups: caries untreated, Ca(OH)₂, and engineering dental pulp-like tissue (EDPT). hUC-MSCs and CGF scaffold were combined to construct EDPT, and the histological structure was observed. Odontoblasts and dental pulp cells were counted in each group. The results showed that hUC-MSCs adhered firmly to the porous mesh CGF scaffold, grew vigorously, and stretched sufficiently. In the EDPT group, odontoblasts in the root canal were arranged neatly, and predentin was formed. The odontoblast and dental pulp cell counts in the EDPT group were statistically significant compared to the caries untreated and Ca(OH)₂ groups. The hUC-MSCs-CGF could successfully repair necrotic pulp in animals with dental caries.

This study investigated the adhesion of 4META-MMA-TBB resin to CAD/CAM composite resin blocks. CAD/CAM composite resin blocks were subjected to alumina blasting, ceramic primer treatment, or both, and then bonded with 4META-MMA-TBB resin. The tensile bond strength of 4META-MMA-TBB resin to blocks without surface treatment was approximately 20 MPa, but with surface treatment, it significantly improved to approximately 40 MPa. Cohesive failure was observed in some blocks with surface treatment with both alumina blasting and ceramic primer. As a result of Soxhlet extraction of the adhesive interface with acetone solvent and FT-IR spectrum analysis, it was found that PMMA remained on the block surface when surface treatment with both alumina blasting and ceramic primer were performed. These results demonstrated that the bond strength of 4META-MMA-TBB resin is significantly improved when both alumina blasting and ceramic primer are applied as surface pretreatment to the CAD/CAM composite resin block.

The aim of this study was to investigate the rheological properties and handling characteristics of four brands of injectable calcium hydroxide pastes (Calcipex II, CleaniCal, DiaPaste, Well-Paste). Shear viscosity was measured with a rotational rheometer. A universal mechanics analyzer assembled in the laboratory was used to quantify the force for extrusion and extruded weight of the materials. The apical pressure during injection into an artificial root canal was measured using a pressure sensor. All materials exhibited pseudoplastic behavior. The force for extrusion was highest for DiaPaste, and lowest for CleaniCal, while the extruded weight was lowest for DiaPaste and highest for CleaniCal (p<0.05), indicating a need for caution when using CleaniCal. However, the pressure generated at the apex may vary depending on the shape, and taper of the needle tip, as well as the viscosity of the materials.

This study investigates how the cavity depth of restorations influences the color adjustment potential of universal shade bulk-fill resin composites. Standard cavities, with diameters of 4 mm and depths of either 2 or 4 mm, were created at the center of artificial teeth occlusal surfaces. A structural-colored bulk-fill resin composite and two pigment-incorporated universal shade bulk-fill resin composites were used. Each resin composite was placed into the cavity to assess its color adjustment potential in relation to the artificial tooth color. Following application, the resin composites' surfaces were polished using diamond-impregnated silicone polishers. Color difference analysis revealed ΔE*ab values of 3.3-4.6 and 2.2-9.6 for structural-colored resin composites and pigment-incorporated universal shade resin composites, respectively, as well as ΔE₀₀ values of 2.7-3.4 and 1.7-5.8 for these resin composites, respectively. These findings suggest that the tested bulk-fill resin composites' color adjustment potential was influenced by restoration depth.

This study investigated the mechanical properties of three denture base resin materials produced by three-dimensional (3D) printing (Group P), computer-aided design/computer-aided manufacturing milling (Group M), and conventional (Group C) methods. Three-point flexural tests were performed before and after thermocycling treatment to evaluate the mechanical properties. Additionally, nanoindentation and dynamic mechanical analysis (DMA) were used to analyze the behavior of the materials. After flexural strength tests, scanning electron microscopy (SEM) was performed to evaluate the fracture cross-section. The results consistently showed that Group P exhibited significantly higher flexural strength and modulus regardless of thermocycling than Groups C and M (p<0.05), along with a higher storage modulus in DMA and greater resistance and resilience to nanoindentation deformation. SEM analysis showed that Group C had a relatively smooth cross-section, whereas Groups M and P had torn cross-sections. This study suggests that the 3D-printed material has suitable mechanical properties for hard dental prosthesis applications.

The study assessed the depth of cure (DOC) of different resin composites light-cured through different types of CAD/CAM materials of variable thickness. Three CAD/CAM materials (multilayer zirconia, lithium disilicate glass ceramic, composite) of three thicknesses (2-, 3-, and 4-mm) were prepared and their translucency parameter (TP) were measured. A light-curable and a dual-curable resin cement (Variolink Esthetic LC and DC) and a bulk-fill resin composite with a higher Ivocerin concentration (Tetric PowerFill) were used to mimic luting agents. DOC was assessed via Vickers microhardness testing. Increased thickness of CAD/CAM specimen was associated with decreased DOC. The chemical composition of the resin composites affected their curing performance depending on the light curing mode. Tetric PowerFill presented the greater DOC among the other resin composites. Receiver operating characteristic models of curing status appeared to provide better insight in predicting the DOC of luting agent according to TP than linear regression.