Adsorption of Saliva Related Protein on Denture Materials: An X-Ray Photoelectron Spectroscopy and Quartz Crystal Microbalance Study

The aim of this study was to evaluate the difference in the adsorption behavior of different types of bovine salivary proteins on the PMMA and Ti QCM sensors are fabricated by spin-coating and sputtering onto bare QCM sensors by using QCM and X-ray photoelectron spectroscopy (XPS). SPM, XPS, and contact angle investigations were carried out to determine the chemical composition and surface wettability of the QCM surface. We discuss the quality of each sensor and evaluate the potential of the high-frequency QCM sensors by investigating the binding between the QCM sensor and the proteins albumin and mucin (a salivary-related protein). The SPM image showed a relatively homogeneous surface with nano-order roughness. The XPS survey spectra of the thin films coated on the sensors were similar to the binding energy of the characteristic spectra of PMMA and Ti. Additionally, the amount of salivary-related protein on the PMMA QCM sensor was higher than those on the Ti and Au QCM sensors. The difference of protein adsorption is proposed to be related to the wettability of each material. The PMMA and Ti QCM sensors are useful tools to study the adsorption and desorption of albumin and mucin on denture surfaces

Effect of Nanosheet Surface Structure of Titanium Alloys on Cell Differentiation

Titanium alloys are the most frequently used dental implants partly because of the protective oxide coating that spontaneously forms on their surface. We fabricated titania nanosheet (TNS) structures on titanium surfaces by NaOH treatment to improve bone differentiation on titanium alloy implants. The cellular response to TNSs on Ti6Al4V alloy was investigated, and the ability of the modified surfaces to affect osteogenic differentiation of rat bone marrow cells and increase the success rate of titanium implants was evaluated. The nanoscale network structures formed by alkali etching markedly enhanced the functions of cell adhesion and osteogenesis-related gene expression of rat bone marrow cells. Other cell behaviors, such as proliferation, alkaline phosphatase activity, osteocalcin deposition, and mineralization, were also markedly increased in TNS-modified Ti6Al4V. Our results suggest that titanium implants modified with nanostructures promote osteogenic differentiation, which may improve the biointegration of these implants into the alveolar bone

Study protocol for a multi-center, randomized controlled trial to develop Japanese denture adhesive guidelines for patients with complete dentures : the Denture Adhesive Guideline trial : study protocol for a randomized controlled trial

Background: Denture adhesives, characterized as medical products in 1935 by the American Dental Association, have been considered useful adjuncts for improving denture retention and stability. However, many dentists in Japan are hesitant to acknowledge denture adhesives in daily practice because of the stereotype that dentures should be inherently stable, without the aid of adhesives. The aim of this study is to verify the efficacy of denture adhesives to establish guidelines for Japanese users. The null hypothesis is that the application of denture adhesives, including the cream and powder types, or a control (isotonic sodium chloride solution) would not produce different outcomes nor would they differentially improve the set outcomes between baseline and day 4 post-application. Methods: This ten-center, randomized controlled trial with parallel groups is ongoing. Three hundred edentulous patients with complete dentures will be allocated to three groups (cream-type adhesive, powder-type adhesive, and control groups). The participants will wear their dentures with the denture adhesive for 4 days, including during eight meals (three breakfasts, two lunches, and three dinners). The baseline measurements and final measurements for the denture adhesives will be performed on the first day and after breakfast on the fourth day. The primary outcome is a general satisfaction rating for the denture. The secondary outcomes are denture satisfaction ratings for various denture functions, occlusal bite force, resistance to dislodgement, masticatory performance, perceived chewing ability, and oral health-related quality of life. Between-subjects comparisons among the three groups and within-subjects comparisons of the pre- and post-intervention measurements will be performed. Furthermore, a multiple regression analysis will be performed. The main analyses will be based on the intention-to-treat principle. A sample size of 100 subjects per group, including an assumed dropout rate of 10 %, will be required to achieve 80 % power with a 5 % alpha level. Discussion: This randomized clinical trial will provide information about denture adhesives to complete denture wearers, prosthodontic educators, and dentists in Japan. We believe this new evidence on denture adhesive use from Japan will aid dentists in their daily practice even in other countries

Special Issue: Advances in Dental Bio-Nanomaterials

Recent advances in dental materials involving the development of various biomaterials have been reported. Accordingly, clinicians must incorporate the new dental materials in their practice to respond to the increasing needs of patients. Nanotechnology is defined as a science that deals with nanoscale materials. The use of nanomaterials is gaining popularity in the dental industry for processing and manipulating nanoscale substances in modern dentistry. In this special issue, we invited the submission of several research papers on the development of dental materials. In this general discussion, we briefly explain the relevant research reports with an aim that developments in this field will contribute toward the development of dental care in the future

Effect of Plasma Treatment of Titanium Surface on Biocompatibility

It was recently reported that implant osseointegration is affected by surface wettability. The relationship between hydrophilicity and cell adhesion was corroborated by numerous in vivo studies. Concentrated alkali improves the biocompatibility of pure titanium. Research was conducted on the mechanism by which this treatment increases hydrophilicity. In the present study, we used atmospheric pressure plasma processing to enhance the hydrophilicity of the material surface. The aim was to assess its influences on the initial adhesion of the material to rat bone marrow and subsequent differentiation into hard tissue. Superhydrophilicity was induced on a pure titanium surface with a piezobrush, a simple, compact alternative to the conventional atmospheric pressure plasma device. No structural change was confirmed by Scanning electron microscope (SEM) or scanning probe microscopy (SPM) observation. X-ray photoelectron spectroscopy (XPS) analysis presented with hydroxide formation and a reduction in the C peak. A decrease in contact angle was also observed. The treated samples had higher values for in vitro bovine serum albumin (BSA) adsorption, rat bone marrow (RBM) cell initial adhesion, alkaline phosphatase activity (ALP) activity tests, and factors related to bone differentiation than the untreated control. The present study indicated that the induction of superhydrophilicity in titanium via atmospheric pressure plasma treatment with a piezobrush affects RBM cell adhesion and bone differentiation without altering surface properties

Structural Characterization and Osseointegrative Properties of Pulsed Laser-Deposited Fluorinated Hydroxyapatite Films on Nano-Zirconia for Implant Applications

Standard zirconia implants used in restoration still present problems related to inertness and long-term stability. Various physicochemical approaches have been used to modify the implant surfaces to improve early and late bone-to-implant integration; however, no ideal surface modification has been reported. This study used pulsed laser deposition to deposit a fluorinated hydroxyapatite (FHA) film on a zirconia implant to create a biologically active surface. The film prepared was uniform, dense, and crack-free, and exhibited granular surface droplets; it also presented excellent mechanical strength and favorable biological behavior. The FHA-coated implant was implanted on the femur of Sprague–Dawley rats, and various tests and analyses were performed. Results show that the in vitro initial cell activity on the FHA-coated samples was enhanced. In addition, higher alkaline phosphatase activity and cell mineralization were detected in cells cultured on the FHA-coated groups. Further, the newly formed bone volume of the FHA-coated group was higher than that of the bare micro-adjusted composite nano-zirconia (NANOZR) group. Therefore, the FHA film facilitated osseointegration and may improve the long-term survival rates of dental implants, and could become part of a new treatment technology for implant surfaces, promoting further optimization of NANOZR implant materials

Staphylococcus aureus colonization in contact hypersensitivity induces a shift in cutaneous cytokine milieu from a Th1- to a Th2-type profile

Background: Colonization of atopic dermatitis lesions with Staphylococcus aureus is a frequent phenomenon and may exacerbate inflammation of the skin. The aim of the present study was to determine the effect of S. aureus on T cell-mediated immune responses in contact hypersensitivity caused by a hapten or a protein with large molecule. Methods: Staphylococcus aureus or phosphate-buffered saline was inoculated on experimental contact dermatitis induced by 2,4,6-trinitro-1-chlorobenzene (TNCB) or house dust mite antigen. At various times after inoculation, the experimental lesions were examined histologically and immunohistochemically. Furthermore, the kinetics of cytokine patterns (interferon (IFN)-γ, interleukin (IL)-2, IL-4 and IL-5) in each lesion were analyzed by reverse transcription-polymerase chain reaction. Results: In TNCB-challenged lesions inoculated with S. aureus, the levels of IL-2 mRNA decreased; in contrast, mRNA levels of IL-4 and IL-5 were upregulated. In mite antigen-challenged lesions, IL-4 and IL-5 mRNA expression was detected throughout the period of the investigation, even without S. aureus inoculation. Interferon-γ mRNA expression in mite dermatitis without S. aureus inoculation was observed only in the later period and IL-2 mRNA expression in mite dermatitis with S. aureus was suppressed and observed much later than in the control group. Conclusions: Infestation of S. aureus on skin lesions in experimental contact hypersensitivity induces a shift in the immune reaction from a Th1- to a Th2-dominant response

Antimicrobial Effect of Titanium Hydroxyapatite in Denture Base Resin

In the current study, we investigated the antimicrobial effect of titanium hydroxyapatite (TiHA), a photo-oxidizing organic material, in denture base resin on single-species biofilms formed by laboratory bacteria and on multispecies biofilms formed by bacteria from the human saliva. Although TiHA reportedly restricts the growth of planktonic bacteria upon ultraviolet A (UVA) irradiation, the antimicrobial effect of TiHA on bacterial biofilms remains to be elucidated. Resin specimens were prepared by adding TiHA to polymethyl methacrylate-based, denture base resin. The specimens were incubated with biofilm-forming Streptococcus sanguinis, Actinomyces naeslundii, Staphylococcus aureus, Escherichia coli, or bacteria from the human saliva obtained from volunteers. After UVA irradiation, the colony-forming units (CFUs) from the biofilms formed on the specimens were determined. CFU numbers for S. sanguinis, A. naeslundii, and S. aureus that formed biofilms on TiHA-containing specimens were significantly lower than those formed on specimens without TiHA. TiHA did not reduce the CFUs of biofilm-forming E. coli. In all cases, CFU numbers in the biofilms formed on TiHA-containing specimens by the salivary bacteria were significantly reduced. In addition, neither a 56 h UVA irradiation nor a 28 d soaking in water diminished the antibacterial effect of TiHA. TiHA in denture base resin exerts an antimicrobial effect on single-species bacterial biofilms and biofilms formed by a wide variety of bacteria from human saliva