Non-Thermal Atmospheric Plasma:Can it Be Taken as a Common Solution for the Surface Treatment of Dental Materials?

This study aimed to evaluate the surface roughness and wetting properties of various dental prosthetic materials after different durations of non-thermal atmospheric plasma（NTAP）treatment.One hundred and sixty discs of titanium（Ti）（n：40）,cobalt chromium（Co-Cr）（n：40）,yttrium stabilized tetragonal zirconia polycrystals（Y-TZP）（n：40）and polymethylmethacrylate（PMMA）（n：40）materials were machined and smoothed with silicon carbide papers.The surface roughness was evaluated in a control group and in groups with different plasma exposure times [1-3-5 s].The average surface roughness（Ra）and contact angle（CA）measurements were recorded via an atomic force microscope（AFM）and tensiometer,respectively.Surface changes were examined with a scanning electron microscope（SEM）.Data were analyzed with two-way analysis of variance（ANOVA）and the Tukey HSD test α=0.05）.According to the results,the NTAP surface treatment significantly affected the roughness and wettability properties（P 〈 0.05）.SEM images reveal that more grooves were present in the NTAP groups.With an increase in the NTAP application time,an apparent increment was observed for Ra,except in the PMMA group,and a remarkable reduction in CA was observed in all groups.It is concluded that the NTAP technology could enhance the roughening and wetting performance of various dental materials.

Smart dental materials for antimicrobial applications

Smart biomaterials can sense and react to physiological or external environmental stimuli(e.g.,mechanical,chemical,electrical,or magnetic signals).The last decades have seen exponential growth in the use and development of smart dental biomaterials for antimicrobial applications in dentistry.These biomaterial systems offer improved efficacy and controllable bio-functionalities to prevent infections and extend the longevity of dental devices.This review article presents the current state-of-the-art of design,evaluation,advantages,and limitations of bioactive and stimuli-responsive and autonomous dental materials for antimicrobial applications.First,the importance and classification of smart biomaterials are discussed.Second,the categories of bioresponsive antibacterial dental materials are systematically itemized based on different stimuli,including pH,enzymes,light,magnetic field,and vibrations.For each category,their antimicrobial mechanism,applications,and examples are discussed.Finally,we examined the limitations and obstacles required to develop clinically relevant applications of these appealing technologies.

Novel Unilateral Dental Expander Appliance(UDEX):A Compound Innovative Materials

True unilateral posterior crossbite in adults is a challenging malocclusion to treat,especially when we need to correct cross-arch segments with unwanted effects on non-cross segments.Conventional expansion methods are expected to have some shortcomings;the Unilateral dental expander appliance used to restore unilateral cross bite dental arch is an uncommon appliance;for this,a designed new device is needed.This paper aimed to invite a new unilateral dental expander appliance(UDEX)to treat unilateral dental posterior crossbite in adults using available dental material,easy to use and handle,well tolerated by the patient,and biocompatible with oral structure.It could find that in all dental markets and dental clinics—an eighteen-year-old female with bilateral crossbite and upper and lower dental arch crowding.During active orthodontic treatment,a quad-helix expander had broken from one side at soldering between band and wire attachment.The patient did not show up to the clinic for a while due to COVID 19 pandemic lockdown,leading to a true unilateral crossbite at the dental arch’s upper left side,especially at the molar premolars area.This unilateral cross bite was treated using a new specially designed expanded appliance as a unilateral posterior cross bite dental maxillary expander.As a result of this study,orthodontic treatment was finished within(15)months,much less than expected.We obtained Class I molar and canine relationships with uncrossed dental arches in both upper arch sides,proper overbite and overjet with well-leveled and aligned teeth as it confirmed by clinical examination and radiographic images(OPG Orthopantomogram)and cephalometric radiograph(WebCeph analysis digitalized computer program).Conclude from that,the newly designed unilateral dental expander(UDEX)is proven to be useful for treating real unilateral posterior crossbites as single molar or premolar tooth and multiple joint unilateral crossed posterior teeth.Also,it could easily modify it for future unilateral crossed purposes.This appliance was fabricated using readily available dental material,well tolerated by patients,and reduced the need for excessive patient compliance.An orthodontist could fabricate devices,or cautious laboratory work is required;it can rapidly achieve favorable results.

Fracture and Tribological Evaluation of Dental Composite Resins Containing Pre-polymerized Particle Fillers

The fracture and tribological evaluation of dental composite resin containing pre-polymerized particle fillers were investigated. Composite resins, e.g. metafil, silux plus, heliomolar and palfique estelite were selected as specimens in order to evaluate the effects of pre-polymerized particle filler on the fracture and wear characteristics of composite resins. In the wear tests, a ball-on-flat wear test method was used. The friction coefficient of metafil was quite high. The wear resistance of silux plus and palfique estelite was better than that of metafil and heliomolar under the same experimental condition. The main wear mechanism of composite resins containing pre-polymerized particle fillers was an abrasive wear by brittle fracture of pre-polymerized particles and by debonding of fillers and matrix.

SWELLING AND WETTABILITY OF LIGHT-CURED METHACRYLATE-BASED DENTAL RESINS PREPARED FROM CHOLIC ACID

2＇-methacryloxy-3α, 7α, I2α- trimethacryloyl cholic acid ethyl ester （CAGE4MA） has been prepared from cholic acid. Photo-polymeric resins were prepared from CAGE4MA. 2,2-bis[4-（2-hydroxy-3-methacrylyloxypropoxy）phenyllpropane （bis-GMA） was used for comparison, triethyleneglycol dimethacrylate （TEGDMA） was used as diluent. The polymerization was initiated by camphoroquinone （CQ）/N, N-dimethylaminoethyl methacrylate （DMAEMA） system. The conversion of CAGE4MA was 39% when the reaction time is 60s, which is lower than bis-GMA and TEGDMA. The swelling value of CAGE4MA resin was 0.41% in distilled water, which is much lower than those of bis-GMA resin （2.04%） and TEGDMA resin （4.77%） under the same conditions. Copolymers from CAGE4MA and TEGDMA have been prepared. With the increase of TEGDMA in mixture, the degree of conversion of CA GE4MA and swelling value increased. The swelling values of photocured resins in 0.1mol/L HCl were also measured.

Toward dental caries: Exploring nanoparticle-based platforms and calcium phosphate compounds for dental restorative materials

Millions of people worldwide suffer from a toothache due to tooth cavity,and often permanent tooth loss.Dental caries,also known as tooth decay,is a biofilm-dependent infectious disease that damages teeth by minerals loss and presents a high incidence of clinical restorative polymeric fillings(tooth colored fillings).Until now,restorative polymeric fillings present no bioactivity.The complexity of oral biofilms contributes to the difficulty in developing effective novel dental materials.Nanotechnology has been explored in the development of bioactive dental materials to reduce or modulate the activities of caries-related bacteria.Nano-structured platforms based on calcium phosphate and metallic particles have advanced to impart an anti-caries potential to restorative materials.The bioactivity of these platforms induces prevention of mineral loss of the hard tooth structure and antibacterial activities against caries-related pathogens.It has been suggested that this bioactivity could minimize the incidence of caries around restorations(CARS)and increase the longevity of such filling materials.The last few years witnessed growing numbers of studies on the preparation evaluations of these novel materials.Herein,the caries disease process and the role of pathogenic caries-related biofilm,the increasing incidence of CARS,and the recent efforts employed for incorporation of bioactive nanoparticles in restorative polymer materials as useful strategies for prevention and management of caries-related-bacteria are discussed.We highlight the status of the most advanced and widely explored interaction of nanoparticle-based platforms and calcium phosphate compounds with an eye toward translating the potential of these approaches to the dental clinical reality.

Comparative Mechanical Properties of Bulk-Fill Resins

Aim: The aim of this study was to compare the flexural and compressive strengths of a new sonicactivated bulk-fill system (Sonicfill) with other bulk-fill resins and a universal posterior composite resin. Materials and Methods: A low-stress flowable base resin material (SDR), a bulk-fill composite resin (Tetric Evo Ceram), a universal posterior composite (GC G-aenial), and the Sonicfill system were compared. The specimens were prepared for each group following ISO Standard 4049 (flexural strength) and ADA 27 specifications (compressive strength). One-way variance analysis and Kruskal-Wallis tests were used to determine the statistical differences among groups (p 0.05). Results: The Sonicfill system presented significantly higher compressive strength than other groups (p < 0.001). For flexural strength results, although the Sonicfill system showed the highest values, no statistically significant differences were determined among all groups (p > 0.001). Conclusion: Due to the ability to place restorations with single increment and ease of use, the Sonicfill system can be an alternative for posterior restorations.

A dual-axis chewing simulator for in vitro wear test of dental restoration materials

The wear rate of dental restoration materials on fixed, removable, and implant prostheses is important in the maintenance of cuspate form, masticatory efficiency and occlusal stability. Many permanent restoration materials such as composite, amalgam, gold, or porcelain show enough resistance to wear, but the wear rates of newly developed materials are generally unknown. To evaluate the wear rate of these dental materials, in vivo (clinic) and in vitro methods can be used. Since in vivo investigations are expensive, time consuming, and difficult to standardize, various in vitro methods have been developed. The use of a chewing machine is considered the best method, because a variety of wear mechanisms, temperature changes, and chemical effects of food and drink can be simulated simultaneously. This paper describes a dual axis chewing simulator for in vitro wear test of dental restoration materials. It consists of 8 test chambers, two stepper motors and related mechanism, a hot and cool water circle system, and a control unit. In the chambers, samples and antagonists make chewing movements vertically and Albert Ludwigs University, School of dentistry, Freiburg, Germany (Lü XY, Kern M and Strub JR) horizontally driven by the stepper motors so that the gnashing and slippage of two teeth against each other is simulated. A weighted test object is programmed to collide with a sample under precise operator control. The antagonists strike against the samples at various speeds from a slow nudge to snapping. Sample holders are designed for installation of varying samples, from single teeth to complete dentures. Two baths, six valves, and a group of pipes are used for the thermocycling. The machine can simulate various chewing modes in the mouth, including fully programmable thermal water cycling between 5℃ and 60℃ The control unit consists of a computer system with a built in specific program. Important operations such as “Start”, “Zero point”, and “Stop” are carried out by pressing the function keys on the front board of the unit. During the programming process and the simulation, several test modes and relevant test parameters are shown on the monitor. The control unit is connected via a series of interfaces to different controlled parts of the machine, such as the stepper motors and the pumps of cool and warm water.

Influence of dental restorative material properties on bond interface reliability： a finite element analysis

Background Varieties of restorative materials are widely used in dentistry. The aim of this study is to explore the influence of different dental restorative materials on bond interface reliability. Methods A two-dimensional finite element analysis method was adopted to simulate the shear-bond efficacy test. The influence of elastic modulus and Poisson＇s ratio were investigated separately. Several dental restorative materials including resins, metals, and ceramics were analyzed in this study. Results The deformation and peak equivalent stress level of the dentin-adhesive interface rose sharply following a decrease in the elasticity of restorative materials, especially those with a low elastic modulus range. The influence of the Poisson＇s coefficient was not significant. Ceramics and gold alloy were preferred to resin composite in restorations bearing extensive shear load during service. Conclusions Restorative materials with an elastic modulus similar to that of teeth are not always the best clinical choice. This research provides a helpful guide for the application of different restorative materials in clinical practice.

Guanidine derivative inhibits C. albicans biofilm growth on denture liner without promote loss of materials’ resistance

To reduce the burden of denture stomatitis and oral candidiasis,an aqueous solution containing polyhexamethylene guanidine hydrochloride(PHMGH)was investigated as an antifungal disinfectant against the leading cause of these oral conditions,Candida albicans.The solutions formulated with concentrations ranging from 0.125 to 0.50 wt%enabled increasing disinfection at the initial 5min-contact with 72h-mature candida biofilms formed on denture liner specimens.After 10 min-contact,the solution at lower concentration has reached total fungal elimination.The results also indicated that the denture liners preserved their mechanical property after the maximum contact time with the solution at the highest tested concentration.The PHMGH aqueous solutions at 0.125 wt%could be applied to promote interim denture liner disinfection without promoting the loss of materials’mechanical property.

Improved corrosion resistance of dental Ti50Zr alloy with(TiZr)N coating in fluoridated acidic artificial saliva

The electrochemical corrosion behavior of the dental Ti50 Zr alloy with and without nanocrystalline(TiZr)N coating was comparatively investigated in artificial saliva solutions with different pH values and fluoride ion concentrations. The chemical stability of the passive films on the coated and non-coated Ti50 Zr alloy was evaluated by calculating passive film thickness. The chemical compositions and valence structures of the passive films were analyzed by X-ray photoelectron spectroscopy(XPS). The results show that the(TiZr)N-coated alloy displays distinctly decreased corrosion rate and increased impedance compared with Ti50 Zr alloy in nonfluoridated and fluoridated acidic solutions. Particularly, in the solution of pH = 3.9 and 0.15% NaF-containing, the corrosion protection efficiency of(TiZr)N coating reaches90%. The excellent corrosion resistance of the coated alloy is attributed to that the nanocrystallines in(TiZr)N coating decreases micropores and crack defects, which strongly impedes the corrosive ions diffusion and electrode process at Ti substrate/coating interface. Meanwhile,(TiZr)N coating shows good passivation behavior in acidic solution and active–passive transition behavior in fluoridated acidic solution. The coated Ti50 Zr alloy with high chemical stability has potential application prospect for dental implants.

3D printing preview for stereo-lithography based on photopolymerization kinetic models

The diversity of biomedical applications makes stereolithographic(SL)three-dimensional(3D)printing process complex.A strategy was developed to simulate the layer-by-layer fabrication of 3D printed products combining polymerization kinetic with reaction conditions to realize print preview.As a representative example,the typical UV-curable dental materials based on epoxy acrylate and photoinitiator with different molar ratios was exposed under varying intensity of UV light to verify the simulation results.A theoretical kinetics model containing oxygen inhibition was established.In-situ FTIR was employed to measure propagation and termination constants while coupled UV/vis was performed to examine the law of light attenuation during cure reaction,even with various colours and additives.Simulation results showed that the correlation coefficient square between the experiments and simulations of epoxy acrylate with 1%,2%and 3%initiator upon 20 mW/cm2 UV light are 0.8959,0.9324 and 0.9337,respectively.Consequently,our simulation of photopolymerization for SL 3D printing successfully realized visualization of printing quality before practically printing the targeted biomedical objects with complex topology structures.