One technique for placing of resin-based composite for large posterior cavities is the use of short fiber-reinforced resin-based composite (SFRC) to replace dentin in a biomimetic approach. As endurance under mastication cycles is a significant consideration in the clinical success of resin-based composite posterior restorations, the use of SFRC as a base material may prevent restorative fracture due to the fibers’ effectiveness in stopping cracks. This review article specifies the characteristics of SFRC and describes the major underlying mechanisms of short fiber reinforcement for resin-based composite. Insights are further taken from laboratory studies used to define the short fiber-related properties of resin-based composite and the performance of currently available materials, focusing on aspects that are relevant to the reinforcement of resin-based composite. Finally, future standpoints on the development of SFRCs with nano fibers and different resin monomers, and their role in digital dentistry, are discussed.
The fixation of titanium implants in bone tissue is affected by the presence of a passive titanium oxide (TiO2) layer. Specifically, oxidation products in the amorphous TiO2 matrix enhance the mechanical properties of mineralized tissues. In addition, in vitro mineralization mediated by primary osteoblasts on amorphous TiO2 generates stiff tissues in a process that resembles pathological mechanisms connected with tumors and proceeds through hydrogen peroxide-inducible clone-5 (Hic-5) expression. However, the relationship between surface-based peroxidation and stiff mineralized tissue formation remains unclear. In this study, titanium samples were processed using wire electrical discharge machining to generate oxidation products in amorphous TiO2. The gene expression profiles of primary osteoblasts cultured on these specimens were characterized. Increased expression of Hic-5 was correlated with the presence of peroxidation products. The crystallization of amorphous TiO2 in these samples reduced the expression of both Hic-5 and lysyl oxidase, an enzyme that promotes matrix cross-linking.
The study evaluated the effect of sodium hypochlorite (NaOCl) treatment on fluorotic enamel bonding of four adhesive systems. They were Single Bond 2 (SB2), Prime&Bond NT (PBN), Clearfil SE Bond (CSB), and Single Bond Universal (SBU). One hundred eighteen extracted moderate fluorotic molars were divided into eight groups according to NaOCl pretreatment and four adhesive systems. The microshear bond strength (μSBS), etching pattern, and penetration depth (PD) were observed. The statistical method was two-way ANOVA and least significant difference (LSD) test (α=0.05). The application of NaOCl significantly increased the μSBS of PBN and SBU (p<0.05). The enamel-etching pattern of CSB and SBU was deeper under SEM. A noticeable increase of PD was in SB2 and SBU after the application of NaOCl (p<0.05). Pretreatment of 5.25% NaOCl for the 60 s can increase μSBS of PBN and SBU, PD of SB2 and SBU, and improve enamel-etching pattern of CSB and SBU to fluorotic enamel.
The aim of this study was to develop a polishing paste containing ceria to polish lithium disilicate. The samples were prepared, polished with sandpaper using a polishing-machine, the surface roughness (Ra) was measured using a profilometer and randomly divided into 7 groups (n=10). The control group was polished with diamond paste (D). The 6 remaining groups were polished with alumina-ceria paste with different ratios of deionized water:alumina:ceria by weight: 1:0.5:0.5 (AC0.5), 1:0.5:1 (AC1), 1:0.5:1.5 (AC1.5), 1:0.5:2 (AC2), 1:0.5:2.5 (AC2.5) and 1:0.5:3 (AC3). The specimens were polished for 30 s and their Ra values were determined. The surface roughness measurement was repeated after an additional 30 s of polishing until 120 s of polishing had been performed. The Ra values decreased as the ratio of ceria increased. The surface morphology of the samples analyzed using scanning electron microscopy corresponded with their Ra values.
The aim of this study was to evaluate the maximum amount of chlorhexidine (CHX) that could be incorporated to self-adhesive resin cements to add antibacterial effect without affecting the physical properties. The CHX was incorporated into a commercial self-adhesive resin cement at mass fractions of 0.5–15 wt%, and the CHX-release profile, antibacterial effect, flexural and bond strengths of experimental cements were evaluated. Increasing the CHX content from 5 to 15 wt% resulted in a higher released concentration of CHX. In agar diffusion tests, experimental cements containing 5, 10, and 15 wt% CHX produced inhibition zones against oral bacteria. In flexural strength and shear bond strength to dentin, no significant reduction was observed with the incorporation of 5 wt% CHX. This in vitro study suggests that the addition of 5 wt% CHX yielded an antibacterial self-adhesive cement and had no adverse effect on the flexural and shear bond strengths.
This study aims to compare the static friction of untreated and fine particle shot peening (FPSP) treated stainless steel and ceramic bracket slots. A total of 60 pieces of stainless steel and 60 pieces of ceramic brackets (Roth prescription, 0.022×0.028 in2) were divided into 3 groups: control (n=20), silica glass bead particle surface treatment (n=20) and stainless steel (SUS316L) particle surface treatment (n=20). Ten brackets of each group were combined with 0.019×0.025 in2 orthodontic stainless steel arch wires and were analyzed for static friction. The remaining 10 brackets of each group were tested for slot surface roughness and hardness. The result shows that stainless steel brackets treated with FPSP exhibited lower static friction, with smoother and harder surfaces than the control group (p<0.05). In contrast, treated ceramic brackets showed no difference from the control group in terms of static friction, roughness, and hardness (p>0.05).
Orthodontic aligners undergo deformation during installation, producing an unexpected component of elastic restoring force that causes unintended changes in the dentition. The aim of this study was to investigate the relationship between strain and elastic recovery of the aligner. We distinguished the contributions to aligner deformation due to molding and installation by measuring the thickness distribution of an aligner after molding using micro-CT and tracking changes in grid patterns drawn on the sheet used to fabricate the aligner. The aligner was installed on a device that simulated canine movement. Although canine strain was quite strong around the cusp, and in premolar, it was observed mainly in their centers. Furthermore, after molding, thickness distribution of the aligner was found. But, it is no clear relationship between the thickness distribution and the strain distribution. Our method of analysis can help improve aligner design and establish molding method to deliver optimal orthodontic treatment.
Silver-modified atraumatic restorative technique (SMART) is an emerging restorative technique; however, the effect of silver diamine fluoride (SDF) application on the bond strength of glass ionomer cement (GIC) is unknown. This study aimed to determine if SDF application to sound and artificial caries-affected dentin (ACAD) immediately prior to GIC restoration affected microtensile bond strength (µTBS). Caries was induced on extracted molars using a pH-cycling protocol that was validated against natural caries (similar µTBS). Dentin surfaces were treated with 38% SDF, control groups with de-ionized water and immediately restored. Beam-shaped specimens were sectioned and subjected to tensile forces for µTBS determination. Two hundred and eighty-seven specimens from 40 teeth were tested. SDF application significantly (p<0.001) reduced µTBS in sound dentin (19.00±8.20 MPa vs. 14.60±6.68 MPa), while no difference was found in ACAD. No difference was found in failure mode among groups. For SMART, SDF application on sound dentin before immediate GIC restoration may decrease bond strength.
This study uses fracture tests and fractographical analysis to compare computer-aided design and computer-aided manufacturing (CAD/CAM) lithium disilicate molar crowns with the previous occlusal thickness recommendation of 1.5-mm, the new recommendation of 1.0-mm, and a less invasive thickness of 0.8-mm. After fatigue application, fracture tests and fractographic analysis were conducted. The fracture resistance of CAD/CAM lithium disilicate molar crowns was different depending on the occlusal thickness of the restoration, and decreased with lower the thickness. However, the fracture resistance of crowns of all three thicknesses exceeded the reported maximum bite force in the first molar region after the fatigue process, and can be considered acceptable for use in the clinic.
Buccal mucosae are considered as a site for vaccine delivery since they are relatively abundant with antigen-presenting dendritic cells, mainly Langerhans cells. In this study, we formulated carbonated hydroxy apatite (CHA) with ovalbumin (OVA) (denoted as CHA-OVA), incorporated it into bilayer buccal membrane to form hydrogel films containing CHA-OVA complex for vaccination via buccal mucosae. Ethylcellulose blend with polyethylene glycol 400 were used as impermeable backing layer. Physical properties of all tested buccal membranes were found suitable for mucosal application. In vitro and ex vivo release study showed there was no burst release of OVA found from all tested formula. From the in vivo examination, rabbit buccal mucosae vaccinated by mucoadhesive membranes containing CHA-OVA complex demonstrated mucosal specific antibody induction, represented the potential of CHA as a candidate of needle-free vaccine adjuvant. Future research is awaiting to investigate proper CHA crystallinity in complex with protein against targeted diseases.
This study investigated how the double application of adhesives and dentin moisture level influence the microtensile bond strength (µTBS) of universal adhesives containing different hydrophilic monomers to bur-cut dentin. Four universal adhesives (Scotchbond Universal, Clearfil Universal Bond Quick, Prime&Bond Universal, BeautiBond Universal) were applied to wet and dry bur-cut dentin either in one or two layers. The µTBS test was performed after 25,000 thermal cycles, and scanning electron microscopy was used for the analysis of failure mode and interfacial ultrastructure. Double application significantly improved µTBS on wet dentin (p<0.001), but the effect was not significant on dry dentin (p>0.050). Double application also enhanced the formation of resin tags and limited voids within the adhesive layer of BeautiBond Universal. Dentin moisture had a significant effect on µTBS only if the adhesives were applied in a single layer (p=0.007). Except for Prime&Bond Universal, the tested universal adhesives performed better on dry dentin.
The relative dentin abrasivity-profilometry equivalent values were compared using non-contact profilometry with three subtypes of regular toothpaste and two subtypes of whitening toothpaste containing sodium bicarbonate and 35% hydrogen peroxide. Bovine dentin specimens were assigned to six groups: regular toothpaste (R): R1 (BAMBOO SALT GUM OINTMENT); R2 (MEDIAN TARTAR ORIGINAL); R3 (PERIOE Alpha), Reference slurry: RS (calcium pyrophosphate), whitening toothpaste (W): W1 (NET. WT); W2 (Vussen 28 WHITENING). Relative dentin abrasion–profilometry equivalent (RDA-PE) was determined by brushing 10,000 times (n=8). The pH of the toothpaste was measured (n=5) and the abrasive constituents of the toothpaste was analyzed by FE-SEM and EDS. The RDA-PE values ranged from 26 to 166, and the pH level ranges were 4.928–9.153. The RDA-PE value of the whitening toothpaste containing hydrogen peroxide was not high compared with that of the regular toothpaste. The RDA-PE values of whitening toothpaste could vary depending on the mechanism and ingredients of the whitening agents.
The need for denture adhesives is increasing worldwide, but few denture-care products target denture adhesive users. Foam denture cleaners have been recently marketed to assist brush denture cleaning, but there is a lack of objective evaluation. In this study, we compared the detergency of denture adhesives using six commercial foam-denture cleaners. For removing the adhesives, most of the tested cleaners were effective in immersion experiments, and three cleaners were more effective in the denture cleaning experiment compared to control water. However, only one could effectively remove the slime that is derived from the adhesive and detergency of artificial dirt. The surface roughnesses of the denture base and the relining material revealed that prolonged immersion in some cleaners could be affected. The results suggest that different commercial foam denture cleaners have different detergency levels, and that some cleaners may affect the properties of denture materials upon long-term use.
This study aimed to evaluate the shear bond strength (SBS) of four bonding agents used to bond metal brackets to zirconia under different storage conditions. Four bonding agents were used [FLC: (Fuji ORTHO LC), XT: (TransbondTM XT), RUC-SBU: (Rely XTM Ultimate Clicker Adhesive Resin Cement+Single Bond Universal), and RUC-GBU: (Rely XTM Ultimate Clicker Adhesive Resin Cement+Gluma Bond Universal)] to bond two types of metal brackets (PT/3M) to zirconia surfaces, and they were stored in water at 37ºC for 24 h or thermocycling for 3,000 cycles. The SBS data of RUC-SBU and RUC-GBU using PT brackets were significantly higher than those of 3M brackets before and after thermocycling. It could be concluded that RUC-SBU and RUC-GBU could offer sufficient bond strength between metal brackets and zirconia for the short term compared with FLC and XT. The design of brackets can significantly affect the bond strength to zirconia.
The important factors contributing to the effectiveness of fluoride varnish are the amount of fluoride ion release and the retention time of the varnish on the tooth surface. Commercial fluoride varnishes are susceptible to mechanical removal; therefore, patients are informed to avoid eating or performing oral hygiene for at least 12–24 h, which results in patient inconvenience. However, cyanoacrylate-based fluoride varnish would not have these disadvantages. This study compared the daily fluoride ion release, abrasion resistance to brushing, and toxicity to human gingival fibroblasts (hGFs) between a newly-developed cyanoacrylate-based fluoride varnish and conventional fluoride varnish (Duraphat varnish). The results demonstrated that the cyanoacrylate varnish had a significantly higher fluoride release for 9 days after application, higher abrasion resistance to brushing, and slightly less toxicity to hGFs compared with Duraphat varnish. This novel cyanoacrylate varnish could be an alternative fluoride varnish for preventing dental caries.
The microbial leakage at the implant–abutment interface (IAI) is one cause of peri-implant infection that puts long-term implant stability at risk. The present study compared two types of Morse taper implants in terms of sealing performance at the implanthealing abutment interface. Three implant systems, one of which exhibited a partial face-contact design (TSO) and the other two a line-contact design (TSM and BLT), were analyzed in vitro using two quantitative implant leakage measuring techniques: air-injection pressure measurement test and microbial examination. An in-house-developed device was used to determine implant leakage by recording the initial drop in pressure while injecting air through the implant. The microbial examination measured the absorbances of culture mediums in which the inoculated implants were contained. Significant difference was found between the partial face- and line-contact groups (p<0.001). Both tests revealed that partial face-contact implants are more prone to leakage than line-contact implants.
This study aimed to investigate the effect of N-2-methyl-pyrrolidone (NMP) on the removal of Enterococcus faecalis biofilm. Colony-forming unit (CFU) counting, crystal violet staining, and extracellular DNA (eDNA) measurements were performed to analyze removal of the biofilms formed in a bovine root canal. A confocal laser scanning microscope (CLSM) assay was used to measure the volume of the biofilms. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to investigate the biofilm-associated genes. The morphologic feature of the biofilms was observed under a scanning electron microscope (SEM). NMP decreased CFU numbers, eDNA levels, and biofilm biomass significantly compared to control. qRT-PCR showed that NMP increased the expression of some virulence-associated genes, but downregulated genes related to colonization and persistency. SEM showed that the numerous dentinal tubules were exposed as a result of removal of the biofilm. Collectively, NMP has the potential to be used as a vehicle for endodontic intracanal medicaments.
This study aimed to investigate in vitro biologic properties of mineral trioxide aggregate (MTA) mixed with 3% PVA (MTA-3% PVA) and in vivo dental pulp responses to direct capping in comparison with MTA mixed with distilled water (MTA-DW). Cell proliferation and osteogenic differentiation in culture of human dental pulp cells (hDPCs), and pH changes were evaluated. Pulps in 24 mandibular premolars of four 9-month-old beagle dogs were mechanically exposed and direct pulp capping was performed. Histological specimens were scored according to the degree of mineralization. MTA-3% PVA showed similar cell proliferation and similar or superior osteogenic differentiation of hDPCs compared with MTA-DW. All specimens were associated with calcified bridge formation and there were no significant differences in mineralization scores between the groups (p>0.05). The results suggested that MTA-3% PVA exhibited favorable biocompatibility and osteogenic differentiation in vitro compared with MTA-DW. Furthermore, both groups demonstrated similar results when used as pulp-capping agents in vivo.