Oxygen-inhibited Layer Research Articles

Are the properties of 3D printed dental materials affected by nitrogen-rich postpolymerization? A systematic review and meta-analysis.

The vat polymerization-based 3-dimensional (3D) printing of dental materials necessitates a postpolymerization procedure to complete the fabrication of the printed device. A nitrogen-rich postpolymerization (NRPP) environment has been claimed to prevent the formation of an oxygen-inhibited layer, potentially improving material characteristics. However, a consensus on its impact on properties relevant to dental applications is lacking. The purpose of this systematic review and meta-analysis was to synthesize evidence comparing the chemical, physical, mechanical, and biological properties of 3D printed dental materials subjected to NRPP against conventional postpolymerization. Comprehensive searches were conducted across MEDLINE (via PubMed), Web of Science, Scopus, Open Access Theses and Dissertations, and Google Scholar and using the manual method without language restrictions up to February 2024. Two reviewers screened the literature, assessed the risk of bias (RoB) using the QUality assessment tool for IN vitro studies (QUIN), and independently extracted data from eligible studies. Meta-analysis was undertaken by using a random-effects statistical model with the R-software program, and evidence certainty was rated via the grading of recommendations assessment, development, and evaluation (GRADE) approach. Of 275 articles, 14 in vitro studies with a medium RoB were included in the systematic review, with 8 eligible for meta-analysis. These studies involved 3D printed occlusal devices, implant guides, denture bases, interim crowns or fixed partial dentures, and orthodontic aligners. No statistically significant standardized mean difference (SMD) in material properties was found between with and without NRPP for water solubility, dimensional accuracy, water sorption, flexural modulus, flexural strength, hardness, or fracture toughness (P>.05). An exception was the degree of surface polymerization, with an SMD of 1.66% (95% CI, 0.56 to 2.76; I2=65%) favoring NRPP. The overall certainty of evidence was graded as low to very low. NRPP does not significantly alter the physical, chemical, or mechanical properties of 3D printed dental materials except for a higher degree of surface polymerization in unpolished occlusal devices. The overall evidence certainty was rated as low to very low.

Multiphysics Simulation of Continuous Liquid Interface Production (CLIP) 3D Printing Technology

Abstract This study explores the advancements of 3D printing through Continuous Liquid Interface Production (CLIP), which has achieved a remarkable 100-fold increase in print speed over conventional stereolithography. CLIP’s rapid printing is enabled by an oxygen inhibition layer above the resin-vat window, initiating photopolymerization above the deadzone for faster resin flow. Despite CLIP’s notable speed advantage, it struggles with artifacts arising from non-optimal print cofigurations. Our research addresses this challenge by developing a novel multiphysics simulation tool. In order to evaluate the effects of various parameters, this study introduces a 2D-CLIP multiphysics simulation tool integrating optical and chemical models. The simulation tool employs a MATLAB-PDE solver that incorporates multiphysics equations to forecast deadzone thickness and cured dimensions at various print settings. This approach allows for a comprehensive understanding of the CLIP process and its variables. The simulation tool effectively predicts key parameters, aiding in the fine-tuning of the printing process. It significantly reduces experimental costs and time while enhancing the precision of CLIP 3D printing. The tool’s predictions are instrumental in optimizing print parameters, thereby mitigating the prevalent artifacts in printed objects. This research contributes a pioneering simulation tool for CLIP 3D printing, addressing the critical gap in optimizing print configurations. Its innovative approach in integrating multiphysics models within a simulation framework offers a valuable asset in advancing the capabilities of high-speed 3D printing technologies.

Examination of adhesive force and the model’s dimension in continuous and conventional printing using the oxygen inhibition effect

In constrained surface vat photopolymerization, the adhesive force between the formed layer of the model and the bottom of the resin container restricts the printing capability. This research investigates the adhesive forces in digital light processing (DLP) and continuous digital light processing (CDLP), focusing on how the oxygen inhibition effect, resin container membrane, and model geometries affect these forces. This study tested four distinct resin vats, with particular attention given to oxygen-permeable vats, to evaluate their role in reducing adhesive forces. A permeable vat that reduced the separation force by 52% using the oxygen inhibition layer was assessed for continuous printing. The influence of model geometry on the adhesive force in DLP and CDLP was evaluated using a permeable vat. Moreover, an inverse relationship was identified between resin absorbance and both curing depth and printing speed. It was observed that as the model’s cross-sectional area increased, so did the adhesion force in continuous printing. These findings prove that continuous printing can achieve faster build times in CDLP than in DLP, with a maximum speed of 288 mm/h.

Polishing methods for composites restoration: the influence on human gingival fibroblasts behaviour

BackgroundCarious/Non-carious cervical lesions with gingival recessions may require both dental and periodontal reconstructive therapy, where flaps/grafts may be placed in contact with a dental filling material. Human Gingival Fibroblasts (HGF-1) response during the early phase of healing could vary according to the procedures employed to cure the dental composite. Moreover, oxygen diffusion into dental composite inhibits the polymerization reaction, creating an oxygen-inhibited layer (OIL) that presents residual unreacted monomers. The aim of this study was to assess the effect of different polishing techniques and OIL on HGF-1.MethodsComposite discs polished with different techniques (diamond rubber, abrasive discs and tungsten carbide burr) were used. An additional not polished smooth group obtained with and without OIL was used as control. Samples were physically characterized through the analysis of their hydrophilicity and surface topography through contact angle measurement and SEM, respectively; afterwards the biologic response of HGF-1 when cultured on the different substrates was analyzed in terms of cytotoxicity and gene expression.ResultsThe finishing systems caused alterations to the wettability, even if without a proportional relation towards the results of the proliferation essay, from which emerges a greater proliferation on surfaces polished with one-step diamond rubber and with abrasive discs as well as a direct effect of the glycerin layer, confirming that surface roughness can heavily influence the biological response of HGF-1.ConclusionsSurfaces wettability as well as cellular behavior seem to be affected by the selection of the finishing system used to lastly shape the restoration. Especially, the presence of OIL act as a negative factor in the regards of human gingival fibroblasts. The present study may provide the first clinical instruction regarding the best polishing system of composite material when the restoration is placed directly in contact with soft tissue cells. Understanding HGF-1 behavior can help identifying the polishing treatment for direct restoration of carious/non-carious cervical lesions associated with gingival recessions.

Influence of surface finishing on the outcome of a 3-point bending test in polymer-based dental composits assessed by qualitative and quantitative fractography

ObjectivesThe aim of the study was to evaluate the influence of surface finishing in three polymer-based composits (composits) on the result of a 3-point bending test using quantitative and qualitative fractography as well as microstructural characteristics. Materials and methods270 rectangular specimens (n = 30) of three composits were prepared, stored and tested according to NIST No. 4877. Prior testing, the samples were subjected to three surface treatments: 1) no treatment, to preserve the oxygen inhibition layer, 2) with FEPA P1200 (ANSI equivalent grit 600) SiC paper abraded surface, and 3) polished surface. A three-point bending testing was employed, followed by quantitative (assessment of reason for failure and fracture pattern) and qualitative (fracture mirror measurements) fractography, 3D and 2D surface imaging, surface roughness, reliability and Fe-SEM analysis. The mirror radius that runs in the direction of constant stress was used to calculate the mirror constant (A) using Orr's equation. Uni- and multifactorial ANOVA, Tukey's post hoc test, and Weibull analysis was performed for statistical analysis. ResultsSurface finishing has less influence on the fracture pattern, reliability and mechanical parameters and has no influence on the mirror constant. The amount of inorganic filler has a direct impact on flexural strength and modulus, while the ranking of materials was independent of surface treatment. Failures initiated by volume defects were the most common failure mode (77.0%) with surface defects accounting for 14.9% (edge) and 7.7% (corner). Polishing resulted in lower peak-to valley height compared to no treatment, both 3–4 times lower compared to the 600 grit treatment. The increase in roughness within the analyzed range did not lead to an increase in surface-related failures. ConclusionsThe clear dominance of volume defects in all examined materials as a cause of material fracture reduces the impact of roughness on the measured properties. This insight was only possible using qualitative and quantitative research fractography.

Effects of various beverages on characteristics of provisional restoration materials.

To investigate the effect of common beverages on four currently used provisional restoration materials: Protemp®4, Integrity®, polymethyl methacrylate(PMMA) block, and acrylic resin. Flowable resin composite is included as a control group. Each material was formed into disks of 10-mm diameter and 4-mm thickness (N = 40) by loading the material into acrylic molds. The exposed surface in the mold was covered using a glass slide to prevent an oxygen inhibition layer, and polymerization then proceeded. The solidified disks were placed in distilled water for 24 h. These samples (n = 8) were then immersed for 14 days in one of four different beverages: water, orange juice, cola, and coffee. Changes in color dimension, hardness, and roughness were observed and then analyzed using two-way repeated analysis of variance. The provisional materials had more obvious changes in all three color dimensions than the flowable resin composite. Integrity showed the biggest changes, followed by acrylic resin and PMMA block, whereas Protemp had the smallest changes. The hardness of all the materials significantly decreased after immersion in any of the beverages for 14 days. There were no changes in surface roughness when the materials were immersed in distilled water. The surface roughness of the PMMA block significantly decreased in orange juice whereas that of Integrity and acrylic resin significantly increased in cola. Different kinds of provisional materials had different degrees of staining due to their composition. Moisture had a significant influence on the hardness of materials, and the acidity of cola significantly roughened the surface of the provisional materials.

The effect of oxygen-inhibited layer and its inhibition technique on diametral tensile strength values of various nanofilled composite resin types

Abstract Aim: To investigate the impact of different inhibitory techniques on the thickness of oxygen-inhibited layer (OIL) and diametral tensile strength (DTS) value in various types of nanofilled composite resins. Materials and Methods: Thirty-six nanofilled composite resins specimens, consisting of packable, flowable, high-viscosity bulk-fill (HVBF), low-viscosity bulk-fill (LVBF), shaped as half disk (diameter: 6 mm and height 3 mm) and randomly allocated to three groups (n = 3): with Mylar strip, glycerin application, and without OIL inhibitors. OIL thickness was observed with an optical microscope. Furthermore, 60 specimens of composite resins were incrementally created in disk-shaped molds (diameter: 6 mm, height: 1.5 mm × 2 mm). DTS measurements were carried out using a universal testing machine. Data were statistically analyzed using a two-way analysis of variance (ANOVA) test and Pearson’s correlation test (P < 0.05). Results: OIL inhibitor techniques (Mylar strip and glycerin) significantly affected OIL formation across various types of nanofilled composite resins (P < 0.05). Changes were also observed in how these techniques influenced DTS values. Correlation analysis indicated a positive relationship between OIL thickness and DTS value. Conclusions: Application of Mylar strip and glycerin reduced OIL thickness and DTS values in packable, flowable, HVBF, LVBF nanofilled composite resins. Glycerin proved to be more effective than Mylar strips in reducing OIL thickness, which is reflected in the DTS values of nanofilled composite resins. Greater OIL layer thickness on the outermost layer of the nanofilled composite resin correlated with a higher DTS value.

Rapid UV-curable preparation of durable soybean oil-based superhydrophobic anti-icing surfaces with excellent photothermal deicing property

Photothermal superhydrophobic coatings are promising for anti-icing/deicing. However, preparing such coatings from environmentally friendly and sustainable strategies is challenging. Herein, a bio-based and durable photothermal superhydrophobic coating is prepared via layer-by-layer strategy. Bio-based methacrylic acid epoxidized soybean oil oligomers are synthesized as an alternative to petroleum-based binders. Meanwhile, efficient photothermal conversion of hydrophobic particles are enabled by oxidative self-polymerization of dopamine to decorate hydrophobic silica particles grafted with hydrophobic long-chain alkanes and photo-curable methacrylic acid moieties. Ultimately, the superhydrophobic coating is achieved by spraying photothermal hydrophobic particles onto an oxygen-inhibited layer of pre-cured bio-based binder followed by thorough photocuring treatment. The coating exhibits powerful water repellency (WCA of 158.2 ± 1.6°, SA of 4.6 ± 0.8°), good robustness, chemical and UV irradiation resistance. Moreover, under NIR laser irradiation (808 nm, 1 W/cm2), the coating features excellent photothermal conversion efficiency (ΔT of 41.0 °C at 30 s) and stable photothermal conversion performance. And in frigid conditions (-15 °C, ∼73 ± 5 % RH), the coating delivers rapid defrosting (few seconds) and deicing (20 μL water droplet melts in 42 s) performance under NIR irradiation of 1 W/cm2. Therefore, the as-prepared coating provides valuable insight into global anti-icing/deicing action.

Evaluating the advancements in a recently introduced universal adhesive compared to its predecessor

Background/purposeThe dental adhesive market is constantly evolving to meet the demands of dentists and patients, but new products and upgrades should be rigorously evaluated before being used in clinical practice. This study investigated the physicomechanical properties and dentin bonding efficacy of a newly upgraded universal adhesive compared to its predecessor. Materials and methodsTwenty-four molars were divided into four groups (n = 6/group) based on adhesive (new vs. predecessor) and application mode [self-etch (SE) vs. etch-and-rinse (ER)] for evaluating their dentin microtensile bond strength (μTBS), failure pattern, and bonding interface. Additional thirty-six molars’ crowns were perpendicularly sectioned to obtain flat mid-coronal dentin discs. The opposing dentin surfaces of each disc received contrasting treatments (new/predecessor adhesive applied in SE/ER mode), resulting in six interventions. The bonded discs (n = 6/intervention) were used to assess the adhesives’ survival probability employing a double-sided μTBS test. The other physicomechanical properties examined were adhesives’ oxygen inhibition layer (OIL), viscosity, hardness, elastic modulus, degree of conversion (DC), and in-situ DC. ResultsBoth adhesive versions showed similar μTBS (P > 0.05), failure pattern (P > 0.05), and survival probability (P > 0.008). ER mode promoted resin tag formation and exhibited a slender adhesive layer for both adhesives. The newer adhesive version showed a thinner adhesive layer in general with narrower OIL (P < 0.001), less viscosity (P < 0.001), higher hardness (P < 0.05), elastic modulus (P < 0.05), DC (P < 0.001), and in-situ DC (P < 0.001). ConclusionWhile the newly updated adhesive had superior physicomechanical properties with more fluidity, its dentin bonding efficacy and survival probability were comparable to its predecessor.

Mathematical-Physical Description of the Oxygen-Inhibited Layer (OIL) in Nanofilled Dental Polymers

This research evaluates the presence of the oxygen-inhibited layer (OIL) on the top surface of a photopolymerized dental composite resin protected with a glycerin layer. This evaluation was conducted using physical and mathematical methods. Polymerized discs were fabricated to evaluate Vickers microhardness (VHN), and pre-and post-polymerized samples were used for the calculation of C-O/C-H ratios through Fourier Transform Infrared Spectroscopy (FTIR) (n=10), using two types of glycerin, one for medical use (MG) and another for dental use (DG). Surface hardness decreased from MG to DG to CO, and the increase in C-O/C-H ratios decreased in the same order (p&lt;0.05). Samples protected with medical and dental glycerin layers are harder and exhibit lower C-O/C-H bond ratios than the control group.

Compressive strength of nanohybrid composite resin after the application of glycerin immersed in fermented milk

Background: The prevalence of dental caries in Indonesia in 2018 is 45.3% of the population. Tooth filling is done so that dental caries does not spread further. The restorative material that is commonly used is composite resin. The compressive strength of composite resin is affected by the polymerization process. The surface of the composite resin exposed to air causes the formation of oxygen inhibited layer (OIL). Glycerin acts as a surface coating that can inhibit contact between the composite resin and air so that polymerization can run optimally. Changes in the mechanical properties of composite resins are also influenced by salivary pH and food intake. The acid contained in fermented milk can affect the matrix and filler bonds in composite resins. Further research is needed to determine the compressive strength of nanohybrid composite resins after the application of glycerin in fermented milk immersion. Purpose: To find out whether there is a change in the compressive strength of nanohybrid composite resin after the application of glycerin immersed in fermented milk, also to find out whether the glycerin application and immersion in fermented milk play a role in causing changes of the compressive strength. Methods: Laboratory experimental research with a total sample of 28 which was divided into 4 groups. Composite resin samples were made with a thickness of 3 mm and a diameter of 5 mm, followed by measuring the compressive strength using the Universal Testing Machine. Results: Independent T-Test test showed significantly different results. The compressive strength value of the group with glycerin application was higher than without glycerin application. Meanwhile, the group immersed in fermented milk drinks had lower compressive strength compared to saline immersion. Conclusion: The compressive strength of the nanohybrid composite resin changed after the application of glycerin immersed in fermented milk.

Color changes of nanofiller composite resin after glycerin application immersed in turmeric extract

Background: Nanofiller composite resin has good mechanical strength also used for restoration that require aesthetics. However, resin composites can experience discoloration resulting in extrinsic or intrinsic factors. To produce perfect polymerization, glycerin can be used as an air-inhibition coating to prevent the formation of Oxygen-Inhibited Layer resulting in a more stable over discoloration. Purpose: To knowing the color change due to the application of glycerin on nanofiller composite resin immersed in turmeric extract solution. Method: It is a laboratory experimental study with a Pre-Test-Post-Test Control Group Design using 28 samples of 3M ESPE Filtek 350XT nanofiller composite resin divided into 4 groups, namely the group with glycerin application and without glycerin application which were soaked in turmeric extract with and saline for 4 days. The color changes were measured using a CHNSpec CS-10 colorimeter before and after immersion. Results: Nanofiller composite resin with turmeric extract immersion without glycerin application had an average discoloration of 90.97 + 23.26 while with glycerin application it had a lower average of 84.37 + 9.24. On the results of the independent sample t-test with a significant level of 5%, it has a value of p = 0.506 &gt; 0.05. Conclusion: Composite resin with glycerin application experienced less color change than composite resin without glycerin application in turmeric extract immersion, but statistically not significant.

THE EFFECT OF GLYCERIN APPLICATION ON ROUGHNESS OF NANOHYBRID COMPOSITE RESIN IMMERSED IN ISOTONIC DRINK

ABSTRACTBackground: Composite resin is the most commonly used restorative material. One type of composite resin based on the filler material is a nanohybrid composite resin which has the advantage of good strength and smooth surface to produce good improvements in terms of durability and aesthetics. The roughness of the resin can be affected by drinks with low pHs, such as isotonic drink. Glycerin can reduce the roughness of the composite resin by acting as a barrier so that an oxygen inhibition layer (OIL) is not formed. Purpose: This study is to determine the effect of glycerin application on the roughness of nanohybrid composite resin immersed in an isotonic drink. Method: A total of 32 samples of nanohybrid composite resin used in this study were made with a diameter of 5 mm and a thickness of 2 mm. The nanohybrid composite resin samples were divided into group I without glycerin application and group II with glycerin application before the light curing process. Both groups were then immersed in an isotonic drink for 18 hours in an incubator. The research continued with roughness testing using a surface roughness tester. Result: There was a significant difference in the roughness of the nanohybrid composite resin immersed in an isotonic drink with and without glycerin application. This is indicated by the p-value &lt; 0.05 in the unpaired bivariate t-test, which means that there is a significant difference in the two sample groups. Conclusion: The application of glycerin can reduce the roughness of the nanohybrid composite resin immersed in isotonic drink. Keywords: Glycerin application, Nanohybrid composite resin, Roughness.

Magnetically Actuable Complex‐Shaped Microgels for Spatio‐Temporal Flow Control

AbstractComplex‐shaped microgels are promising building blocks for soft metamaterials. Their active and remote orientational control provides significant potential in architecting them in time and space. This work describes the use of magnetically actuable microgels of complex shape for spatio‐temporal flow control and showcases the concept for microfluidic impellers. First, the fabrication of complex‐shaped magnetically actuable poly(ethylene glycol) diacrylate based microgels via stop‐flow lithography is presented. The microgels comprise a pre‐programmed magnetic moment set by pre‐aligned maghemite nanospindles during the fabrication step. This feature allows the microgels to be positioned in a static magnetic field and rotate under application of a rotating external field. The dependence of the magnetic field rotation rate and strength, maghemite content, and microgel shape on the magnetic response of the microgels is comprehensively quantified. Finally, the magnetic complex‐shaped microgels are integrated as actuable impellers in a microfluidic chip. The microgels are positioned in space by polymerizing them around fixed poly(dimethylsiloxane) (PDMS) pillars. Free rotation around the PDMS pillar is achieved due to the oxygen inhibition layer at the chip and pillar surface. The versatility of the fabrication methodology is showcased by the investigation of in‐chip mixing in a microfluidic device consisting of soft responsive impellers.

Evaluation of component release and oxygen-inhibited layer removal on cytotoxicity of syringe-type bis-acryl composites for provisional restorations

본 연구의 목적은 시린지 형태의 비스아크릴 기반 임시치관용 자가중합형 복합레진의 용출물을 분석하고, 산소중합억제층 제거방법이 세포독성에 미치는 영향을 평가하고자 하였다. 평가를 위해 시판 중인 네 가지 임시치관용 비스아크릴 복합레진을 비교분석하였다. 실험에는Protemp 4(PT), Structur 2 SC(ST), Luxatemp Automix Plus(LT)과 Hexa-Temp(HT)를 사용하였다. 원반형 레진 시편을 제작하여 메탄올에서 24시간 용출 후, 기체 크로마토그래피/질량 분석법(GC/MS)을 사용하여 용출물을 분석하였다. 동일하게 제작된 원반형 시편으로 세포독성을 평가하기 위해 한천중층시험법과 live/dead assay를 사용하였다. 산소중합억제층 제거영향을 평가하기 위해 산소중합억제층을 재현한 원반형 시편을 제작하였다. 표면 처리 방법에 따라 세 개의 하위집단인, 처리하지 않은 대조군(N), 산소중합억제층을 알코올로 문질러 제거한 군(A), 표면 연마 후 알코올로 문질러 제거한 군(PA)으로 나누었다. 세포독성은 시편을 배지에 용출하여WST-1으로 평가하였다. 통계분석을 위해 소프트웨어를 사용하였으며, 등분산과 정규성 검정 후, ANOVA와 Bonferroni 사후분석법으로 통계적 유의성을 평가하였다(α=0.05). GC/MS 분석 결과, 실험군에 따라 서로 다른 구성성분이 용출되었다. 한천중층시험법 결과, 세포독성은 HT, LT, ST에서 심한독성, PT에서는 중등도의 독성이 나타났다. 산소중합억제층 제거에 의한 세포생존은 모든 레진에서 N에 비해 PA 가 유의하게 높았으며, HT와 ST는 A에 비해 PA에서 유의하게 높았다. 시린지 형태의 임시치관용 자가중합형 복합레진은 구성성분에 따라 구강 내 세포독성에 영향을 줄 수 있는 다양한 용출물이 구강 내로 용출될 수 있으며, 임시치관 재료의 독성은 산소중합억제층 제거하는 방법에 따라 감소할 수 있다.

The Microhardness and Surface Roughness Assessment of Bulk-Fill Resin Composites Treated with and without the Application of an Oxygen-Inhibited Layer and a Polishing System: An In Vitro Study.

The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks divided into three groups: Tetric N-Ceram Bulk Fill, Opus Bulk Fill APS, and Filtek Bulk Fill. Each resin composite group was further divided into two subgroups: with and without OIL control. Subsequently, surface roughness and microhardness were measured before and after polishing. A t-test was used to compare independent and related measures. For the intergroup comparison of variation before and after polishing, the Kruskal–Wallis test with Bonferroni post hoc was used considering a significance level of p < 0.05. When comparing surface roughness, significant differences were observed between Opus Bulk Fill resin composite with and without OIL control (p = 0.003) before polishing. The same occurred when comparing Tetric N-Ceram resin composite with and without OIL control (p = 0.039) after polishing. In addition, the surface roughness of Filtek Bulk Fill, Opus Bulk Fill, and Tetric N-Ceram Bulk Fill resin composites, with and without OIL control, decreased significantly after polishing (p < 0.001), while surface microhardness significantly increased (p < 0.05), with the exception of Opus Bulk Fill resin with OIL control (p = 0.413). In conclusion, OIL control and polishing significantly improved the surface roughness and surface microhardness of Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites. However, in the case of Opus Bulk Fill resin composite, only its surface roughness was significantly improved.

Polysilazane-derived SiCN ceramics-based layerless printing

In the process of light curing printing, layer steps are formed in the stacking direction. As these steps, i.e., by-products, affect the accuracy and quality of the printed surface significantly, avoiding their formation during printing is a prominent research topic. In this study, we propose a layerless printing method.Layerless printing uses the inhibition effect of oxygen on the polymerization reaction of ceramic precursor photosensitive resins, construct the oxygen inhibition layer during the printing process. We control the oxygen inhibition layer to weaken/eliminate the steps. In layerless printing, the high viscosity ceramic precursor photosensitive resin reduces the viscosity by heating up to make the fluidity of the material meet the printing conditions.The ceramic material can be realized straight-walled layerless in the z direction with a traditional layer thickness (100 µm). Furthermore, after pyrolysis of the printed ceramic precursor structure,the ceramic structure continued to retain zero layer steps.The result is that layerless printing reduced the surface roughness of the ceramic by 86.4%, the hardness and modulus of the ceramic were increased by approximately 10%, and the ceramic lattice of layerless printing was more uniformly stressed when subjected to compression stress. • Layer steps are eliminated by layerless printing. • The use of layerless printing can obtain a ceramic structure with a more uniform force. • Layerless printing can improve the accuracy of the print structure.

Influence of surface treatment and curing mode of resin composite cements on fibroblast behavior

BackgroundHuman gingival fibroblast (HGF-1) cells in the connective tissue provide an effective barrier between the alveolar bone and the oral environment. Cement margins of restorations with intrasulcular preparation or cemented implant restorations are in contact with HGF cells. However, it is unknown to what extend the cement surface finish affects the behavior of HGF cells. The purpose of this study was to compare the behavior of HGF-1 cells in contact with two different resin composite cements with three different surface treatments after light-curing and autopolymerization, respectively.MethodsDisks of one adhesive (Multilink Automix, Ivoclar Vivadent [MLA]) and one self-adhesive (RelyX Unicem 2 Automix, 3 M [RUN]) resin composite cement were either light-cured or autopolymerized. Specimen surfaces were prepared with the oxygen inhibition layer intact, polished with P2500-grit silicon carbide paper or treated with a scaler. Cells were cultivated on the specimens for 24 h. Viability assay was performed, and cell morphology was examined with scanning electron microscopy. Additionally, roughness parameters of the specimen were analyzed with a 3D laser scanning microscope. Three-way ANOVA was applied to determine the effect of cement material, curing mode and surface treatment (a = 0.05).ResultsOverall, cement material (p = 0.031), curing mode (p = 0.001), and surface treatment (p < 0.001) significantly affected relative cell viability of HGF. The autopolymerized specimen with the oxygen inhibition layer left intact displayed the lowest relative cell viability (MLA 25.7%, RUN 46.6%). Removal of the oxygen inhibition layer with a scaler increased cell viability but also resulted in higher surface roughness values.ConclusionsHGF cell viability is affected by the surface treatment and the curing mode. The oxygen inhibition layer is an inhibitory factor for the viability of HGF cells. Autopolymerization enhances the cytotoxic potential of the oxygen inhibition layer.

Efficacy comparison of various oxygen lnhibition layer (OIL) minimizing agents on composite resin by analysis of two different physical properties

Introduction: Composite resins are the most common restorative materials that are used these days and have been radically improving over the past few years. Their polymerisation reaction can be inhibited during light-curing due to the oxygen presence in atmosphere. Aim/objective: The aim of this study is to evaluate effect of different air inhibition coating strategies on composite resin material in terms of hardness and discolouration. Material and Methodology: Composite discs of 6.5 X 2mm were prepared for samples which were cured under a) 0.5mm thick mylar strip b) thin layer of glycerine c) layer of KY jelly (commercial lubricant) d) air cure. These samples were dipped in cola, turmeric milk, coffee and distilled water for 14 days. Spectrophotometric analysis was done to assess the colour change and Vicker’s hardness test for assessment of the hardness. Statistical analysis was done and the results were concluded. Results: The results were analyzed with ANOVA one-way test followed by Student Newman-Keul test. Moreover, multiple comparisons of means were performed using the Student t-test (p&lt;0.05). Conclusion: Presence of Oxygen inhibition layer(OIL) on surface layer of composite affected the specimens adversely by reducing the microhardness and increasing instability of colour.

The Origins of Acrylates and Adhesive Technologies in Dentistry.

To examine the origins of acrylates and adhesive dentistry up to 1955. A search of MEDLINE database and a manual literature search were conducted to find relevant articles. Acrylic acid was discovered in 1843, methacrylic acid in 1865. In 1880, light polymerization of acrylate compounds using glass prisms was introduced. In 1928, polymethyl methacrylate (PMMA) was industrially produced from methyl methacrylate (MMA). In 1930, PMMA moldings that could be adapted under heat and pressure were introduced into dentistry. The process was improved in 1936 by mixing pulverized PMMA and liquid MMA. In 1940, the intraoral polymerization of dental resins using UV light or catalysts was discovered. In the same year, the combined procedure (dual-curing) and addition of inorganic fillers to improve the material properties (precursors of composites) were proposed. Effects on the oxygen inhibition layer and intraoral bonding between several resin portions were also described. In 1942, direct restorations with self-curing resins (combined with a precursory version of cavity sealing) were described. These new resins were marketed in the late 1940s. Intraoral repair of restorations and cementation of crowns and bridges with resins were also described in 1942. In 1949, a glycerophosphoric acid-based sealer was marketed. In the same year, it was discovered that etching of the enamel (with nitric acid) caused an adhesion to thin layers of acrylic-based materials. In 1955, phosphoric acid etching of enamel was shown to improve adhesion. In the first half of the 20th century, important but little or unknown discoveries took place. These discoveries can improve our understanding of how adhesive dentistry evolved.