Simulated Oral Environment Research Articles

Microfluidic and impedance analysis of rosemary essential oil: implications for dental health

BackgroundOral health is closely linked to systemic conditions, particularly non-communicable diseases (NCDs), which can exacerbate oral issues. Essential oils (EOs) have emerged as potential alternatives for oral health due to their antibacterial, anti-inflammatory, and antioxidant properties. Among these, rosemary essential oil (REO) shows promise due to its various biological activities. This study investigates the potential of REO in dental applications using microfluidic devices and electrochemical impedance spectroscopy (EIS) to analyze the electrical properties of REO in artificial saliva (AS) mixtures.ResultsThe study demonstrated significant variations in impedance across different REO concentrations and their mixtures with AS. Higher impedance was observed in REO mixtures, particularly at lower frequencies, indicating distinct electrical properties compared to pure AS. The impedance of REO was influenced by its concentration, with a 1% REO solution showing higher impedance than a 4% solution, possibly due to micelle formation and changes in dielectric properties. Additionally, microfluidic devices enabled precise control over fluid interactions and real-time monitoring, offering valuable insights into REO's behavior in a simulated oral environment. The impedance data demonstrated significant differences in REO–AS mixtures, highlighting potential interactions critical for oral care applications.ConclusionsRosemary essential oil exhibits unique electrical properties, making it a promising candidate for dental applications, particularly in preventing and treating oral diseases. Microfluidic devices enhance the accuracy and reliability of studying REO's interactions with AS, providing a robust platform for future dental research. The findings suggest that REO could be effectively incorporated into oral care products, offering a natural alternative for combating oral pathogens, reducing inflammation, and protecting against oxidative stress. Future research should focus on clinical trials to validate these findings and explore the synergistic effects of REO with other essential oils.

Effects of Various Solutions on Color Stability and Surface Hardness of Nanohybrid Dental Composite Under Simulated Oral Conditions.

This study evaluated effects of various solutions on color stability and surface hardness of a nanohybrid dental composite in simulated oral environments. Sixty-four composite disks were fabricated and randomly allocated into eight groups (n = 8 per group): Artificial saliva (AS), Biotene (B), passion fruit juice (PFJ), orange juice (OJ), Sprite (S), Coca-Cola (CO), apple cider vinegar (ACV), and cranberry juice (CJ). Specimens were immersed in respective solutions at 37°C for 28 days. Surface microhardness was assessed using Vickers microhardness test, and color alterations were quantified using SpectroShade Micro spectrophotometer. Measurements were taken 24 hours after initial polymerization and after 28-day immersion period. Statistical analysis was performed using mixed model ANOVA. After 28 days, specimens exhibited significant changes in microhardness and color. Polished surfaces showed microhardness decreases of 21.9-35.5%, with ACV and CJ causing largest reductions. Non-polished surfaces unexpectedly showed increased microhardness (11.2-17.4%). Color changes were more pronounced on polished surfaces, with CO and CJ causing maximum alterations. Statistical analysis revealed significant interactions between surface treatment, staining media, and immersion time (p < 0.05). All experimental groups demonstrated significant changes, highlighting composite materials' susceptibility to environmental factors. Even well-polymerized and polished surfaces underwent alterations, emphasizing necessity for periodic follow-up and maintenance polishing in esthetic restorations. The present research emphasizes significance of oral environmental factors on composite restoration longevity and esthetics, advocating for patient education on dietary impacts and tailored maintenance strategies to preserve restoration quality. How to cite this article: Shetty P, Jayakumar HDN, Pulickal TJ, et al. Effects of Various Solutions on Color Stability and Surface Hardness of Nanohybrid Dental Composite Under Simulated Oral Conditions. J Contemp Dent Pract 2024;25(7):669-676.

Microstructure and corrosion behavior of Ti-Mo-Zr alloy fabricated by selective laser melting in simulated oral environment

The microstructure of Ti-Mo-Zr alloy fabricated by selective laser melting (SLM) was studied and its corrosion behavior was investigated by a series of electrochemical methods. The results showed that α+β phases of different proportions were formed after heat treatment, the grain size of the alloy treated at 950℃ slightly increased, because of the existence of the original α grain, the orientation of the α grain was not significantly changed by heat treatment below the β transition temperature. However, heat treatment above β transition temperature significantly changed the orientation of α grains. Electrochemical measurements were conducted in artificial saliva solution and artificial saliva solution containing hydrogen peroxide. The results showed that the corrosion resistance of the original Ti-Mo-Zr alloy was better than that of the Ti-Mo-Zr alloy treated at 950°C and worse than that of the Ti-Mo-Zr alloy treated at 1050°C. The differences in corrosion behavior can be attributed to grain size and orientation and phase distribution.

Analyzing the Bioactivity of a Novel Bone Cement: An In Vitro Study.

To analyze the effect of bioactivebone cement (BBC) placed in a phosphate buffer saline solution in comparison to mineral trioxide aggregate (MTA). Ten samples each of BBC (group 1) and MTA (group 2) were prepared and stored in a phosphate buffer saline solution. After three days of storage, white precipitates were formed on the surface of the samples. The solution with precipitates from each sample was analyzed for the presence of calcium and phosphate ions with coupled plasma atomic spectroscopy. BBC showed a significant amount of calcium and phosphate release after a seven-day storage period in phosphate buffer saline solution. Calcium release was significantly higher in group 1 (MTA) (p < 0.001) compared to that in group 2 (BBC), while group 2 (BBC) (p < 0.001) exhibited greater phosphate release compared to group 1 (MTA). BBC (group 2) retains its bioactivity when it comes into contact with a stimulated oral environment (STF). This demonstrates that BBC is bioactive in a simulated oral environment. Moreover, it retainedgood handling properties and could be easily manipulated into a dough form. Clinically, in cases of apical surgery, internal resorption or perforation repair where material placement poses difficulty, BBC will prove to be beneficial.

Polydimethylsiloxane enabled triple-action water-resistant coating with desirable relaxation rate in clear aligner

Clear aligners undergo rapid stress relaxation in warm, moist oral environments, compromising therapeutic effectiveness and longevity of treatment. To develop an innovative multilayer composite material with improved stability and reduced stress release, we have engineered an innovative coating characterized by the surface aggregation of polydimethylsiloxane (PDMS), which imparts a pronounced hydrophobic effect. In addition, the chemically and physically cross-linked structure of the coating reduces the free volume created by molecular chain rearrangement owing to the presence of water molecules, thereby minimizing water penetration into the coating. Concurrently, the coating’s internal structure is enriched with numerous polar functional groups to capture water molecules that penetrate into the inside of the coating. Through combination of these mechanisms, water molecules are effectively sequestered, thereby impeding their penetration into the polyethylene terephthalate glycol (PETG) substrate. The impact of the polydimethylsiloxane content on the triple-action water-resistance mechanisms was thoroughly examined using attenuated total reflection (ATR)-Fourier transform infrared (FTIR), water absorption rate, water swelling rate, and X-ray photoelectron spectroscopy. The low surface energy cross-linked polyurethane coating is applied to the polyethylene terephthalate glycol (PETG) substrate to create a novel composite material with specific mechanical properties and reduced stress relaxation. The composite material remains stable in simulated oral environment with linear swelling rate of 0.58 % upon water absorption. Additionally, the stress release rate of the composite material within 336 h is notably lower (23.64 %) than that of PETG (62.29 %).

Microstructure, Hardness and EIS Evaluation of Ti-15Zr-5Nb Dental Alloy

Ti alloys have been widely used in biomedical applications due to their special properties. They have specific properties such as biocompatibility, biofunctionality and high corrosion resistance, which enable them to function inside the human body. Among them, Ti-6Al-4V is probably one of the most widely used alloys for implants. However, aluminum and vanadium ions have been reported to cause problems and adverse reactions in the human body over long periods. Thus, in the present study, Ti–15Zr–10Nb alloy synthesized by high vacuum melting was manufactured and characterized by different techniques. The phase composition was determined by XRD. This showed the presence of α and β phases in the alloy, consistent with the microstructural study. From a microstructural point of view, the alloy shows lamellar and acicular structures with α-grain boundaries. Vickers microhardness measurements showed an increased hardness compared to Ti-CP. Furthermore, the electrochemical behavior was evaluated using HCl as an electrolyte. The obtained results were compared to Ti-CP tested in the same electrochemical condition. The studies indicated that Ti-CP presents a nobler electrochemical behavior than Ti-15Zr-5Nb. Thus, despite the very good corrosion properties of Ti-15Zr-5Nb in a simulated oral environment and Ringer’s solutions, the present study reveals that the Ti-15Zr-5Nb alloy has lower corrosion resistance in aggressive media when compared to Ti-CP.

Surface Topography of Thermoplastic Appliance Materials Related to Sorption and Solubility in Artificial Saliva.

(1) Background: PETG (polyethylene terephthalate glycol) is a transparent, inexpensive, and versatile thermoplastic biomaterial, and it is increasingly being used for a variety of medical applications in dentistry, orthopedics, tissue engineering, and surgery. It is known to have remarkable properties such as tensile strength, high ductility, and resistance to chemical insults and heat, but it can be affected by various environmental conditions. The aim of the present study was to evaluate the topographical characteristics of four thermoplastic dental appliance materials in relation to water sorption in simulated oral environments (artificial saliva samples with different pH values). (2) Methods: The following four types of PETG clear thermoplastic materials were selected for the present study: Leone (L), Crystal (C), Erkodur (E), and Duran (D). In relation to the desiccation and water-uptake stages, their water sorption (Wsp) and solubility (Wsl) were calculated, and the surface topographies were analyzed on two length scales. The surface roughness was determined using a contact profilometer, and nanoroughness measurements were generated by three-dimensional profiles using an atomic force microscope (AFM). Statistical analyses (one-way ANOVA and unpaired and paired Student t-tests) were performed. (3) Results: After saliva immersion, the weights of all samples increased, and the highest sorption was recorded in a basic environment. Among the materials, the water uptake for the L samples was the highest, and for E, it was the lowest. In relation to water solubility, significant values were registered for both the L and C samples' materials. After immersion and desiccation, a decreasing trend in microroughness was observed. The AFM high-resolution images reflected more irregular surfaces related to saliva immersion. (4) Conclusions: The sorption rates recorded in water-based artificial saliva were higher for basic pH levels, with significant differences between the samples. There were also significant differences related to the behaviors of the materials included in the study. In relation to roughness, on a microscale, the surfaces tended to be smoother after the saliva immersions, and on a nanoscale, they became more irregular.

Evaluation of the Tribocorrosion Behavior of Ti-6Al-4V Biomedical Alloy in Simulated Oral Environments

Evaluation of the Tribocorrosion Behavior of Ti-6Al-4V Biomedical Alloy in Simulated Oral Environments

Synthesis and Characterization of Sol-Gelled Barium Zirconate as Novel MTA Radiopacifiers.

Barium zirconate (BaZrO3, BZO), which exhibits superior mechanical, thermal, and chemical stability, has been widely used in many applications. In dentistry, BZO is used as a radiopacifier in mineral trioxide aggregates (MTAs) for endodontic filling applications. In the present study, BZO was prepared using the sol-gel process, followed by calcination at 700-1000 °C. The calcined BZO powders were investigated using X-ray diffraction and scanning electron microscopy. Thereafter, MTA-like cements with the addition of calcined BZO powder were evaluated to determine the optimal composition based on radiopacity, diametral tensile strength (DTS), and setting times. The experimental results showed that calcined BZO exhibited a majority BZO phase with minor zirconia crystals. The crystallinity, the percentage, and the average crystalline size of BZO increased with the increasing calcination temperature. The optimal MTA-like cement was obtained by adding 20% of the 700 °C-calcined BZO powder. The initial and final setting times were 25 and 32 min, respectively. They were significantly shorter than those (70 and 56 min, respectively) prepared with commercial BZO powder. It exhibited a radiopacity of 3.60 ± 0.22 mmAl and a DTS of 3.02 ± 0.18 MPa. After 28 days of simulated oral environment storage, the radiopacity and DTS decreased to 3.36 ± 0.53 mmAl and 2.84 ± 0.27 MPa, respectively. This suggests that 700 °C-calcined BZO powder has potential as a novel radiopacifier for MTAs.

Critical cutting thickness model considering subsurface damage of zirconia grinding and friction–wear performance evaluation applied in simulated oral environment

Ductile mode removal is always a popular topic in zirconia ceramic cutting and grinding. The completely undamaged ductile mode grinding is extremely inefficient and difficult to control, which limits the clinical application of dental zirconia ceramics. Hence, considering the effect of subsurface damage, this paper redefines the ductile mode grinding removal of ceramic materials and establishes a critical cutting thickness model for zirconia ceramic grinding. Results show that the better the lubrication condition, the smaller the subsurface damage degree and the larger the removal range of ductile zone. To verify the model, grinding experiments of zirconia ceramic under different lubrication conditions are conducted. The results show that grinding under nanofluid minimum quantity lubrication obtains the lowest friction coefficient, which is reduced by 58.54 % and 18 % compared with dry grinding and minimum quantity lubrication (MQL), respectively. Under nanofluid minimum quantity lubrication (NMQL) condition, the critical cutting thickness is 2.27 µm, which is 160.92 % larger than that under dry grinding. The error between the theoretical model and the experimental results is 10.67 %, which verifies the correctness of the theoretical model. Furthermore, using the workpiece material obtained from grinding experiments, friction–wear experiments are conducted on dental zirconia ceramics under different loads in a simulated oral environment. The results show that zirconia ceramics obtained by NMQL grinding achieve better anti-friction and anti-wear performance than that of MQL. When the maximum cutting thickness of zirconia ceramics processed by NMQL grinding is 2.27 µm, the wear rate of the workpiece is 3.06 × 10−5 mm3/N·m, and at 2.6418 µm, the wear rate of the workpiece is 2.01 × 10−3 mm3/N·m. This paper aims to provide theoretical guidance and technical support for the ductile mode removal of hard, brittle materials.

Analysis of the Effects of Different Orthodontic Appliances on Salivary pH Levels: An In vitro Approach.

Orthodontic appliances can influence the oral environment, including salivary pH levels, which play a crucial role in maintaining oral health. Understanding how different orthodontic appliances affect salivary pH levels can help in improving treatment outcomes and minimizing potential side effects. In this in vitro study, we evaluated the effects of various orthodontic appliances on salivary pH levels using a simulated oral environment. Four different types of orthodontic appliances were tested: traditional metal braces, ceramic braces, lingual braces, and clear aligners. Saliva samples were collected and subjected to pH measurements using a standardized method. The pH measurements were recorded at three different time intervals: immediately after appliance placement, after 24 hours, and after 48 hours. The initial pH values varied among the different orthodontic appliances: metal braces (pH 7.2), ceramic braces (pH 7.4), lingual braces (pH 7.1), and clear aligners (pH 7.5). After 24 hours, there was a decrease in pH levels for all groups: metal braces (pH 6.8), ceramic braces (pH 7.0), lingual braces (pH 6.7), and clear aligners (pH 7.2). After 48 hours, the pH levels continued to decrease: metal braces (pH 6.5), ceramic braces (pH 6.8), lingual braces (pH 6.4), and clear aligners (pH 6.9). Our findings suggest that different orthodontic appliances have varying effects on salivary pH levels. Metal braces and lingual braces tend to cause a more pronounced decrease in salivary pH compared to ceramic braces and clear aligners. Monitoring salivary pH levels during orthodontic treatment may be beneficial in identifying potential risks to oral health and implementing appropriate interventions.

Comparative evaluation of microleakage of self-cure, dual-cure, and light cure glass ionomer cement in a simulated oral environment - an invitro study

Background. Pediatric dentistry utilizes various restorative materials wherein the durability and longevity of these restorations hinge on the maintenance of an intact marginal seal to prevent microleakage and its associated complications. Consequently, this study aims to assess the microleakage of self-cure, dual-cure, and light-cure glass ionomer-based cements utilizing a stereo microscope. Materials and Methods: Sixty therapeutically extracted deciduous molars were taken for the study. The restorative materials used for the studies were self-cure Glass Ionomer cement (Chemfil Rock and GC Fuji IX GP Fast GIC), dual cure Glass Ionomer cement (EquiaForte and Ionolux GIC), and light cure Glass Ionomer cement (GC Fuji II and Ketac N 100 GIC). All samples were stored in commercially available artificial saliva for 20 days to simulate the oral environment. The samples were immersed in Rhodamine B dye for 24 hours, and microleakage was evaluated using a Stereo microscope. Data were tabulated and statistical analysis was done. p &lt; 0.05 is considered significant Results: In the individual assessment of glass ionomer-based cement, Ketac N100 GIC exhibited the lowest microleakage, whereas Ionolux displayed higher levels of microleakage. Conclusion: In terms of the curing method, light-cure glass ionomer cement demonstrated the least microleakage compared to both dual-cure and self-cure glass ionomer cement.

Study on the evaluation method of cigarette astringency in the simulated oral environment.

Cigarettes with pronounced astringency can diminish consumers' enjoyment. However, due to the complex composition of cigarettes, quantifying astringency intensity accurately has been challenging. To address this, research was conducted to develop a method for assessing astringency intensity in a simulated oral environment. The astringency intensity of four cigarette brands was determined using the standard sensory evaluation method. The mainstream smoke absorbing solution (MS) was prepared by simulating the cigarette smoking process, and its physicochemical properties (such as total phenol content and pH levels) were analyzed. The lubrication properties of the five solutions were tested using the MFT-5000 wear tester, and factors influencing cigarette astringency were examined. The findings showed that total phenol content and pH of MS were positively and negatively correlated with astringency intensity, respectively. Particularly, the lubrication properties of MS were significantly correlated with astringency intensity, and the correlation coefficient was affected by load and speed during testing. The study concluded that coefficient of friction was a more reliable measure for assessing the extent of astringency in cigarettes than the total phenol content and pH of MS, offering new insights into astringency evaluation and development of high-grade cigarettes.

Strontium-zinc-based phosphate coatings fabricated in situ on the zinc-pretreated magnesium alloy for degradation control and cytocompatibility enhancement

Owing to the good mechanical support, degradability, and biocompatibility, magnesium (Mg) alloys have large potential in medical applications such as guided bone regeneration membranes. However, the rapid degradation of Mg alloys under physiological conditions hinders many clinical applications. Herein, strontium-zinc-based phosphate (SZP) coatings are fabricated in situ on the zinc (Zn)-electrodeposited WE43 Mg alloy for corrosion protection, degradation control, and cytocompatibility enhancement. The Zn coating acts as a protective cathode for the Mg alloy substrate and provides a stable environment to foster the growth of the SZP coating in comparison with direct deposition onto the Mg alloy surface. The virtues are verified by the smaller corrosion current density, corrosion of the Zn coating instead of the Mg alloy substrate after soaking in artificial saliva, as well as good adhesion provided by the Zn-incorporated transition layer of SrZn2(PO4)2 between the Zn coating and SZP coating. The dense and inert SZP coating mitigates degradation as shown by a decrease in the corrosion current density of 44 times to 0.21 uA cm−2 in the simulated oral environment with artificial saliva. Furthermore, the coating resistance and charge transfer resistance increase by more than one order of magnitude compared to the Zn-treated Mg alloy, and there is no obvious degradation after immersion for 7 days. The Zn coating shows adverse effects on the attachment, spreading, and proliferation of MC3T33-E1 pre-osteoblasts, but the SZP coating providing a higher level larger than 100% of the cell viability after incubation with its extract for 3 days is more compatible with cells because of the retarded dissolution and bio-friendly chemical compositions of SrHPO4 and SrZn2(PO4)2. The hybrid coating has excellent prospects in biomedical products such as biodegradable Mg-based guided bone regeneration membranes.

Digestive characteristics of extracellular polysaccharide from Lactiplantibacillus plantarum T1 and its regulation of intestinal microbiota

This study assessed the potential prebiotic characteristics of the previously reported Lactiplantibacillus plantarum extracellular polysaccharide (EPS-T1) with immunological activity. EPS-T1 was a novel heteropolysaccharide composed of glucose and galactose (1.00:1.21), with a molecular weight of 1.41 × 106 Da. The monosaccharide composition, molecular weight, fourier transform infrared, and 1H NMR analysis showed that EPS-T1 was well tolerated in the simulated oral cavity, gastric fluid, and small intestinal fluid environments, and was not easily degraded. Meanwhile, EPS-T1 could effectively be used as a carbon source to promote the growth of beneficial Lactobacillus species (Lactobacillus delbrueckii ssp. Bulgaricus, Streptococcus thermophilus, Lacticaseibacillus rhamnose GG, Lactiplantibacillus plantarum, Lacticaseibacillus paracasei and Lactobacillus reuteri). After 24 h of fecal fermentation, EPS-T1(5 mg/mL) effectively reduced the relative abundance of harmful bacteria such as the Escherichia-Shigella, Citrobacter, Fusobacterium, Parasutterella, and Lachnoclostridium. While, the level content of beneficial flora (Bacteroides, Blautia, Phascolarctobacterium, Bifidobacterium, Parabacteroides, and Subdoligranulum) were significantly increased. In addition, EPS-T1 was able to significantly promote the enrichment of short-chain fatty acids such as acetic acid, propionic acid and butyric acid. These results provide some basis for the functional application of EPS-T1 as a potential prebiotic.

Oral fast-dissolving risperidone loaded electrospun nanofiber drug delivery systems for antipsychotic therapy

Risperidone is an antipsychotic drug classified as BCS Class II with low solubility at physiological pH and orally used in the treatment of schizophrenia. Electrospinning is one of the newest fabrication methods used for the development of fast soluble drug delivery systems. In this study, an orally disintegrating film (ODF) formulation of risperidone was developed with green electrospinning technique. Different molecular weight polyethylene oxide (PEO) as a polymer and xylitol or Kollidon VA64 as a disintegration agent were used for the preparation of formulations. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) analyses were conducted as part of pre-formulation studies to identify possible incompatibilities in formulation components. We characterized ODFs based on their mechanical properties, shape and diameter of nanofibers, disintegration behavior, and in vitro dissolution profiles. A few wrinkles appeared on the surface of fibers prepared with xylitol, but a smooth surface was evident on Kollidon VA64 fibers. Disintegration studies performed in the simulated oral environment showed that ODFs disintegrate in as little as 1 s. The dissolution behavior of developed ODFs and commercial products was compared with a dissolution study in distilled water. The chosen formulations had acceptable mechanical properties with much faster dissolution compared to the commercially available product. In this study, risperidone ODF formulation was successfully produced and characterized. The study showed that risperidone-loaded nanofibers could provide a promising alternative to conventional oral dosage forms like tablets and capsules.

Comparative Evaluation of Compressive Strength of Self-cure, Dual-cure, and Light-cure Glass Ionomer Cements in a Simulated Oral Environment: An In Vitro Study.

In primary dentition, glass ionomer cements (GICs) have unique benefits as a restorative material. Various types of GICs are available in the market. In pediatric dentistry, the choice of GI materials is generally focused on handling convenience with adequate consideration for mechanical qualities, including compressive strength to withstand occlusal stresses in the oral environment. To evaluate the compressive strength of self-cure, dual-cure, and light-cure GI-based cements using a universal testing machine. The study population comprised 30 cylindrical restorative blocks for compressive strength assessment. The restorative materials used for the studies were self-cure GIC (ChemFil Rock and GC Fuji IX GP Fast GIC), dual-cure GIC (Equia Forte and Ionolux GIC), and light-cure GIC (GC Fuji II LC and Ketac N 100 GIC). The cylindrical blocks were prepared using prefabricated Teflon mold measuring 4 mm diameter and 6 mm height from respective restorative materials and divided into three major groups and were subdivided into six groups comprising two materials in each group. Using an Instron universal testing machine, compressive strength was assessed. Data obtained were tabulated, and statistical analysis was done using Statistical Package for the Social Sciences (SPSS v22.0) software. On individual comparison of GI-based types of cement, Ketac N100 GIC showed the highest compressive strength, and Fuji IX GP Fast GIC showed the least compressive strength. Light-cure GIC exhibited the highest compressive strength in comparison to dual-cure and self-cure GICs with regard to the nature of curing. Chandru TP, Chandran S, Peedikayil FC, et al. Comparative Evaluation of Compressive Strength of Self-cure, Dual-cure, and Light-cure Glass Ionomer Cements in a Simulated Oral Environment: An In Vitro Study. Int J Clin Pediatr Dent 2023;16(5):707-710.

Phenolic composition and antioxidant capacity of betel inflorescence extract in a simulated oral environment

The addition of betel inflorescence (BI) and slaked lime (calcium hydroxide) to betel quid (BQ) formulation may be detrimental to human health. Here, we assessed BI extracts prepared using artificial saliva or aqueous solution with or without adding slaked lime to mimic the release of phytochemicals from BI in the oral cavity. The extracts were also profiled by HPLC-DAD-ESI-QTOF-MS/MS to understand the quality and quantity of phytochemicals released. The results indicate that slaked lime facilitates the extraction of phenolics, likely due to a high pH. In a simulated oral environment with artificial saliva, the addition of slaked lime promotes the release of safrole, a well-known carcinogen. Dominant phytochemicals detected also include eugenol, acetyl eugenol and methyl eugenol, and only a fraction of these compounds is released in the simulated oral environment. This study reveals that environmental conditions can considerably affect the extraction of phytochemicals and triggers further investigation on how chewing practices may influence the release and activity of carcinogens.

An in vitro evaluation of aligner force decay in artificial saliva

Background/purposeThe present study aimed to compare the force decay of invisible aligners for maxillary anterior teeth with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement within a simulated oral environment over 7 days. Materials and methodsThe prepared invisible aligners were immersed in saliva (S) and subjected to applied force (F) for 7 days. The aligners were set and placed on the maxillary right central incisor with 0.1 mm (D1), 0.2 mm (D2), and 0.3 mm (D3) labial movement. Thin-film pressure sensors were used to measure the aligner force changes. The data were collected and analyzed by statistical methods. ResultsSignificant differences were observed in the initial and first-day force between the D2 and D3 groups under simulated oral environment force (SF) (P < 0.05). There was a significant difference in force decay between Day 1 and Day 7 for all groups (P < 0.05). The SFD1 group showed a significant decrease in force on Day 5 (P < 0.05), while the SFD2 and SFD3 groups showed significant force decay on Day 4 (P < 0.05). The force decay ratio on Day 7 was higher in the SFD3 group than in the SFD1 and SFD2 groups, but no significant difference was observed. ConclusionLarger labial movement of the aligners resulted in higher force decay under artificial saliva environments, and the force decay of invisible aligners was increased by immersion time in artificial saliva.

Comparison of mechanical properties of 3-dimensional printed and thermoformed orthodontic aligners

Orthodontic treatment using clear aligners has experienced exponential growth since its introduction in the late 1990s. Three-dimensional (3D) printing has also grown in popularity among orthodontists, and companies have begun to produce resins to directly print clear aligners. This study aimed to examine the mechanical properties of commercially available thermoformed aligners and direct 3D-printed aligners under laboratory conditions and a simulated oral environment. Samples were prepared (approximately 2.5 × 20 mm) from 2 thermoformed materials, EX30 and LD30 (Align Technology Inc, San Jose, Calif), as well as 2 direct 3D-printing resins, Material X (Envisiontec, Inc; Dearborn, Mich) and OD-Clear TF (3DResyns, Barcelona, Spain). Wet samples were subjected to phosphate-buffered saline at 37°C for 7 days, whereas dry samples were stored at 25°C. Tensile and stress relaxation tests were carried out on an RSA3 Dynamic Mechanical Analyzer (Texas Instruments, Dallas, Tex) and Instron Universal Testing System (Instron, Norwood, Mass) to calculate elastic modulus, ultimate tensile strength, and stress relaxation. The elastic modulus of dry and wet samples was 103.2 ± 17.3 MPa and 114.4 ± 17.9 MPa (EX30), 61.3 ± 9.18 MPa and 103.5 ± 11.4 MPa (LD30), 431.2 ± 16.0 MPa and 139.9 ± 34.6 MPa (Material X), and 38.4 ± 14.7 MPa and 38.3 ± 8.4 MPa (OD-Clear TF), respectively. The ultimate tensile strength of dry and wet samples was 64.41 ± 7.25 MPa and 61.43 ± 7.41MPa (EX30), 40.04 ± 5.00 MPa and 30.09 ± 1.50 MPa (LD30), 28.11 ± 3.75 MPa and 27.57 ± 4.09 MPa (Material X), and 9.34 ± 1.96 MPa and 8.27 ± 0.93 MPa (OD-Clear TF), respectively. Residual stress of wet samples at 2% strain for 2 hours was 59.99 ± 3.02% (EX30), 52.57 ± 12.28% (LD30), 6.98 ± 2.64% (Material X), and 4.39 ± 0.84% (OD-Clear TF). There was a significant difference in elastic modulus, ultimate tensile strength, and stress relaxation among the samples tested. Moisture, specifically a simulated oral environment, appears to have a greater effect on the mechanical properties of direct 3D-printed aligners when compared with thermoformed aligners. This is likely to impact the ability of 3D-printed aligners to generate and maintain adequate force levels for tooth movement.