Long-term prognosis after decoronation of avulsed teeth with replacement resorption: a report of three cases.

The complications of replacement resorption following tooth injury in growing children include infrapositioning of the tooth, tilting of the adjacent teeth, and alveolar ridge deformity. Decoronation is a conservative treatment method that facilitates bone preservation. The current case report focuses on the long-term preservation of alveolar ridge dimension following decoronation in three patients. Decoronation was performed prior to occurrence of the pubertal growth spurt, and the patients' ridge width and vertical apposition were monitored for at least 4 years. Timely intervention and regular monitoring are essential for maximization of the benefits of decoronation, a simple procedure that preserves esthetics and minimizes the need for further treatments. The importance of space management for prosthetic treatment has also been highlighted. The findings of this study show that infrapositioned teeth in growing children can be treated successfully using decoronation.

Optimal post height and diameter in preformed zirconia crown restoration on 3D-printed primary incisors.

In this in vitro study, fracture resistance was evaluated according to the post-diameter and -length in zirconia crown restorations on three-dimensional printed primary incisors undergone pulpectomy. One hundred-and-sixty primary incisor abutments were used which were artificially fabricated through 3D-printing. Each group was divided into two subgroups based on the zirconia post-diameter (1.5 mm and 2.0 mm) employed for post setting after pulpectomy. Furthermore, each group was divided into four subgroups based on the zirconia post-height (3.0, 4.0, 5.0 and 6.0 mm). Zirconia post setting was made by applying flowable resin after filling the pulp cavity with calcium hydroxide up to 3.0 mm below cemento-enamel junction (CEJ). Finally, a preformed zirconia crown of size #1 was cemented to the abutment through resin cement. A compressive load was applied to the middle palatal surface of incisors restored with zirconia crowns by using a universal testing machine at 145° angle which is the normal interincisal angle of children. The root fracture specimens were excluded and the samples fractured within crown and core parts were included in the final fracture resistance analysis. The group with 1.5-mm post-diameter and 5.0-mm post-height had the highest fracture resistance strength (130.63 ± 55.75 N) under masticatory pressure condition. Fracture resistance was statistically greater in 5.0-mm than in 4.0-mm and 3.0-mm post-height groups for 1.5-mm post-diameter subgroup. Moreover, 5.0-mm post-height subgroup had a statistically greater fracture resistance than that of 3.0-mm post-height subgroup for 2.0-mm post-diameter group. The 2.0-mm post-diameter subgroup had a statistically greater fracture resistance than that of 1.5-mm post-diameter subgroup for 3.0-mm and 4.0-mm post-heights. If zirconia post incorporation is required for deciduous incisor restoration, a post-length equal to facial CEJ level is recommended for gaining additional retention against masticatory pressure.

Effect of ethyl cellulose coating as an evaluation agent against contamination on the bond strength of zirconia restorations: An in vitro study.

STATEMENT OF PROBLEM: During the trial placement of zirconia restorations, contamination of the bonding surface is inevitable. Although cleaning methods for contaminated surfaces have been described, a method of preventing saliva contamination of the bonding surface of zirconia restorations is lacking. PURPOSE: The purpose of this in vitro study was to investigate an ethyl cellulose coating as an evaluation agent to mitigate the effects of saliva contamination on the bond strength of zirconia restorations. MATERIAL AND METHODS: Experimental groups representing different cleaning methods of tetragonal yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) surfaces were investigated for shear bond strength with a resin luting agent, and the failure mode was analyzed. The 9.0×7.0×5.0-mm zirconia blocks (n=72) were assigned as follows: Group N: uncontaminated control; Group CU: contaminated with saliva, followed by ultrasonic cleaning with ethanol; Group CI: contaminated with saliva, followed by application of a zirconia cleaner; Group PCW: preapplication of a zirconia primer, contaminated with saliva, followed by cleaning with water spray; Group ECU: precoating with the ethyl cellulose agent, contaminated with saliva, followed by removal of the agent in an ultrasonic bath with ethanol. Each group was divided into 3 subgroups (immediate, short-term aging, and long-term aging), and the shear bond strength was measured (n=24). To analyze the bonding surface characteristics, the contact angle was measured (n=5). The surfaces of the zirconia specimens in each experimental group were evaluated by using a field emission scanning electron microscope (n=5). Time-of-flight secondary ion mass spectroscopy was used for the chemical analysis of the conditioned surfaces (n=3). A 2-way analysis of variance (ANOVA) with main effect model for shear bond strength results and a 1-way ANOVA for contact angle data were performed as statistical analysis, followed by the Bonferroni post hoc test (α=.05). RESULTS: The shear bond strength was significantly higher in the ECU group than in the groups with the other cleaning methods (P<.05). After the removal of ethyl cellulose with ethanol, the contact angle and surface topography were found to be similar to those of the control group, and no saliva contaminants were identified in the spectroscopy analysis. CONCLUSIONS: Coating with ethyl cellulose may protect the bonding surface of zirconia restorations from salivary contamination better than cleaning a contaminated surface.

Verapamil-containing silicone gel reduces scar hypertrophy.

A hypertrophic scar is a common dermal fibroproliferative lesion usually treated with topical silicone. Verapamil, a type of calcium channel blocker, is considered a candidate drug for the treatment of hypertrophic scars. Here, we report that the addition of verapamil to topical silicone gel enhances treatment outcomes of hypertrophic scars. Upon creation of hypertrophic scars with the rabbit ear model, varying concentrations of verapamil-added silicone gel (0.1, 1, and 10 mg/g) were applied daily for 28 days. After the animals were euthanised, microscopic measurement was performed for (a) scar elevation index (SEI), (b) fibroblast count, and (c) capillary count. On gross analysis, features of hypertrophic scars were significantly alleviated in the verapamil-added groups. On histologic examination, verapamil-added groups showed (a) reduced SEI (1.93 (1.79-2.67) for control vs 1.34 (1.21-1.51) for silicone only and 1.13 (1.01-1.65) for verapamil-added silicone), (b) fibroblast count 700.5 (599.5-838.5) for control, 613.25 (461-762.5) for silicone only, and 347.33 (182.5-527) for verapamil-added silicone), and (c) capillary formation (52 (35.5-96.5) for control, 46 (28-64.5) for silicone only, and 39.83(24-70) for verapamil-added silicone) (Kruskal-Wallis test, P < .05). On western blot, expression levels of collagen I protein was lower in the 1 mg/g and 10 mg/g verapamil-added silicone compared with control. Therefore, we suggest a therapeutic concentration of verapamil-added silicone gel of at least over 1 mg/g. Further study regarding maximally effective concentration and deeper insight into the mechanism of action should follow.

Effect of conversion to implant-assisted removable partial denture in patients with mandibular Kennedy classification â : A systematic review and meta-analysis.

OBJECTIVE: This review evaluated the change in treatment outcomes after conversion from conventional removable partial denture (RPD) to implant-assisted removable partial denture (IARPD). The patient-reported outcome measures (PROMs), objective parameters for evaluation of functional performance, and biological and mechanical complication were evaluated. MATERIALS AND METHODS: This systematic review was based on the Cochrane review methodology and followed the criteria of the preferred reporting items for systematic reviews and meta-analyses (PRISMA). We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, Web of Science, and Scopus up to April 3, 2019. After the initial search, additional electronic and hand searches were performed to identify further studies, ongoing studies, and gray literature, without restrictions on language, year of publication, or publication type. RESULTS: In total, 6,544 non-duplicate articles were identified, and 31 were eligible for full-text search. Finally, 19 publications based on 13 independent studies were selected. In the meta-analysis, general patient satisfaction was significantly increased (p < .05), and the improved mastication was remarkable oral function. In oral health-related quality of life, the oral health impact profile score was significantly improved, and improvements of physical pain and psychological disability were prominent (p < .05). Masticatory performance was improved in terms of maximum bite force, active occlusal contact area, and mandibular jaw movement (p < .05). The weighted mean survival rate of implants was 96.60%. CONCLUSIONS: After conversion from conventional RPD to IARPD, the PROMs and masticatory performance significantly improved in partially edentulous patients under mandibular Kennedy classification I.

Delayed Spontaneous Eruption of Severely Infraoccluded Primary Second Molar: Two Case Reports.

Infraocclusion occurs at an early age and becomes worse with age, causing increased damage in young children. Extraction of affected teeth is the preferred treatment modality for prevention of possible complications. It is rare for a primary molar to temporarily exhibit secondary failure of eruption, followed by regeneration of full eruptive capacity. This report was written to describe two patients who experienced spontaneous eruption of an infraoccluded primary molar at approximately 7 years of age. While watchful waiting is not always a suitable treatment option, we propose that extraction be deferred until the first permanent molar erupts, unless significant problems occur.

Cotransport and Deposition of Iron Oxides with Different-Sized Plastic Particles in Saturated Quartz Sand.

The present study was designed to investigate the cotransport and deposition of different-sized plastic particle from nano- (0.02 µm) to micrometer-scale (0.2 and 2 µm) with goethite and hematite (two types of representative iron oxides abundant in natural environment) in porous media at both low (5 mM) and high ionic strength (25 mM) in NaCl solutions. We found that through different mechanisms (i.e., modification of surface properties of iron oxides, steric repulsion, or alteration in deposition sites on quartz sand), different-sized plastic particles induced different effects on the transport and deposition behaviors of iron oxides in quartz sand. Likewise, via different mechanisms such as change of surface properties or alteration in deposition sites on quartz sand, different transport behaviors for different sized plastic particles induced by the copresence of iron oxides were also observed. The results of this study suggested that cotransport of iron oxides and plastic particles in porous media is far more complex than those of individual colloid transport. Since both plastic particles and iron oxides are ubiquitous presence in natural environment, it is expected that they would interact with each other and thus alter the surface properties, leading to the change of transport behaviors in porous media.

Global Pattern of Microplastics (MPs) in Commercial Food-Grade Salts: Sea Salt as an Indicator of Seawater MP Pollution.

Previous studies have identified microplastics (MPs) in commercial table salts but could not exactly address the origin of the MPs because of several limitations. The present study is based on the hypothesis that commercial sea salts can act as an indicator of MP pollution in the surrounding environment unless the MPs are filtered out during the manufacturing process. A total of 39 different salt brands produced at geospatially different sites, including 28 sea salt brands from 16 countries/regions on six continents, were investigated. A wide range of MP content (in number of MPs per kg of salt; n/kg) was found: 0-1674 n/kg (excluding one outlier of 13 629 n/kg) in sea salts, 0-148 n/kg in rock salt, and 28-462 n/kg in lake salt. Relatively high MP content was identified in sea salts produced in Asian countries/regions. The abundance of MPs in unrefined sea salts ( n = 25) exhibited significant linear correlations with plastic emissions from worldwide rivers ( r2= 0.33; p = 0.003) and with the MP pollution levels in surrounding seawater ( r2= 0.46; p = 0.021) in the published literature. The results indicate that not only is Asia a hot spot of global plastic pollution, as previous studies have suggested, but also that sea salt can be a good indicator of the magnitude of MP pollution in the surrounding marine environment.

Influence of Nano- and Microplastic Particles on the Transport and Deposition Behaviors of Bacteria in Quartz Sand.

Plastic particles are widely present in the natural environment and are highly likely to interact with bacteria (the ubiquitous microbes in the natural environment), which might affect the transport and deposition of bacteria in porous media. In this study, the significance of plastic particles from nanoscale to micrometer-scale (0.02-2 µm) on the transport and deposition behaviors of bacteria ( Escherichia coli) in quartz sand was examined under environmentally relevant conditions in both NaCl and CaCl2 solutions at pH 6. The results showed that the presence of different-sized plastic particles did not affect bacterial transport behaviors at low ionic strength (10 mM NaCl and 1 mM CaCl2), whereas, at high ionic strength conditions (50 mM NaCl and 5 mM in CaCl2), plastic particles increased bacterial transport in quartz sand. At low ionic strength conditions, the mobility of both plastic particles and bacteria was high, which might drive the negligible effects of plastic particles on bacterial transport behaviors. The mechanisms driving the enhanced cell transport at high ionic strength were different for different-sized plastic particles. Specifically, for 0.02 µm nanoplastic particles, the adsorption of plastic particles onto cell surfaces and the repel effect induced by suspended plastic particles contributed to the increased cell transport. As for 0.2 µm microplastics (MPs), the suspended plastic particles induced  repel effect contributed to the increased cell transport, whereas, for 2 µm MPs, the competition deposition sites by the plastic particles were the contributor to the increased cell transport.

Polyurethane meniscal scaffolds lead to better clinical outcomes but worse articular cartilage status and greater absolute meniscal extrusion.

PURPOSE: Implantation of polyurethane (PU) meniscal scaffolds has become a popular procedure to provide a scaffold for vessel ingrowth and meniscal tissue regeneration in patients with partial meniscal defects. However, it is unclear whether PU meniscal scaffolds lead to better clinical and magnetic resonance imaging (MRI) outcomes post-operatively. This meta-analysis compared the clinical and MRI outcomes in patients with partial meniscal defects treated with PU meniscal scaffolds. METHODS: This meta-analysis reviewed all studies that assessed Lysholm score, International Knee Documentation Committee (IKDC) score, visual analogue scale (VAS) for pain, Tegner score, Knee Injury and Osteoarthritis Outcomes Score (KOOS), articular cartilage (AC), absolute meniscal extrusion (AME), morphology and size (MS), signal intensity (SI) of meniscal implant, and interface of the implant-residual meniscus complex (IIRMC) in patients with partial meniscal defects treated with PU meniscal scaffolds. RESULTS: Eighteen studies were included in the meta-analysis. The proportion of patients who evaluated MS (OR 0.71, 95% CI 0.38-1.33; n.s.), SI (OR 1.07, 95% CI 0.53-2.18; n.s.), and IIRMC (OR 1.00, 95% CI 0.33-3.06; n.s.) did not differ significantly between baseline and final follow-up. However, AC (OR 0.31, 95% CI 0.11-0.84; P = 0.02) and AME (OR 0.05, 95% CI 0.01-0.18; P < 0.00001) worsened between baseline and final follow-up. Conversely, Lysholm score (95% CI -1.87 to -1.07; P < 0.00001), IKDC score (95% CI -2.19 to -1.08; P < 0.00001), VAS for pain (95% CI -2.29 to -1.07; P < 0.00001), Tegner score (95% CI -0.76 to -0.15; P = 0.003), and overall KOOS (95% CI -29.48 to -23.17; P < 0.00001) were significantly greater at final follow-up when compared to baseline. CONCLUSION: This meta-analysis found no significant differences in the tested MRI parameters, including MS, SI, and IIRMC. However, AC and AME worsened between baseline and final follow-up. Conversely, patients treated with PU meniscal scaffolds showed significant functional improvement and pain relief when compared with baseline scores. Thus, PU meniscal scaffolds appear to be a viable alternative for patients with partial meniscal defects, although further studies are needed to determine whether worsened AC and AME are clinically relevant. In particular, precise measurement of PU meniscal scaffolds in combination with thorough investigation of the baseline articular cartilage status and meniscal defect size may be effective for pain relief or functional improvement in patients with PU meniscal scaffold implantation. LEVEL OF EVIDENCE: III.

Numerical study on the three-dimensional temperature distribution according to laser conditions in photothermal therapy of peri-implantitis.

PURPOSE: Dental implants have been successfully implemented as a treatment for tooth loss. However, peri-implantitis, an inflammatory reaction owing to microbial deposition around the implant, can lead to implant failure. So, it is necessary to treat peri-implantitis. Therefore, this numerical study is aimed at investigating conditions for treating peri-implantitis. METHODS: Photothermal therapy, a laser treatment method, utilizes photothermal effect, in which light is converted to heat. This technique has advantage of selectively curing inflamed tissues by increasing their temperature. Accordingly, herein, photothermal effect on peri-implantitis is studied through numerical analysis with using Arrhenius damage integral and Arrhenius thermal damage ratio. RESULTS: Through numerical analysis on peri-implantitis treatment, we explored temperature changes under varied laser settings (laser power, radius, irradiation time). We obtained the temperature distribution on interface of artificial tooth root and inflammation and determined whether temperature exceeds or does not exceed 47℃ to know which laser power affects alveolar bone indirectly. We defined the Arrhenius thermal damage ratio as a variable and determined that the maximum laser power that does not exceed 47℃ at the AA' line is 1.0 W. Additionally, we found that the value of the Arrhenius thermal damage ratio is 0.26 for a laser irradiation time of 100 s and 0.50 for 500 s. CONCLUSION: The result of this numerical study indicates that the Arrhenius thermal damage ratio can be used as a standard for determining the treatment conditions to help assisted laser treatment for peri-implantitis in each numerical analysis scenario.

Desensitizing efficacy of a universal dentin adhesive containing mesoporous bioactive glass on dentin hypersensitivity: a randomized clinical trial with a split-mouth model.

This split-mouth blinded randomized controlled study compared the efficacy of a desensitizing agent with oxalate/resin polymer and a universal adhesive containing mesoporous bioactive glass (MBG) for dentin hypersensitivity (DH) relief, using Schiff sensitivity score (SSS) and visual analog scale (VAS). Split quadrants containing teeth with DH were treated with either MS Coat ONE or Hi-Bond Universal with MBG as the functional additive. Assessments at baseline, immediately post-application, and at 1- and 2-week follow-ups used standardized stimulus protocols (air, cold, and acid). The SSS difference was the primary outcome, while the VAS difference was the secondary outcome. A mixed linear effect model performed statistical analysis. Immediate DH reduction occurred in response to air stimuli, with a significant decrease in Group HB than in Group MS (p = 0.0178). Cold stimulus reduction exhibited a gradual cumulative effect, with consistently greater reductions in Group HB than in Group MS (p ≤ 0.0377). Both groups effectively managed acidic stimuli, with no significant differences (p > 0.05). The VAS scores decreased gradually over the follow-up period (p < 0.0001). This study highlights the differential efficacy of treatments for various DH triggers and recommends specific approaches based on different stimulus types. The universal adhesive containing MBG demonstrated DH relief potential, promising efficacy identical to or superior to that of a dedicated desensitizing agent. Further research exploring the long-term efficacy and underlying mechanisms is warranted. The universal adhesive containing MBG can be adopted as an in-office desensitizing agent for DH relief. The desensitizing efficacy of universal adhesive matches or surpasses dedicated agents for air and cold stimuli.

Garre's osteomyelitis of the mandible managed by nonsurgical re-endodontic treatment.

Chronic osteomyelitis with proliferative periostitis, known as Garre's osteomyelitis, is a type of osteomyelitis characterized by a distinctive gross thickening of the periosteum of bones. Peripheral reactive bone formation can be caused by mild irritation or infection. Garre's osteomyelitis is usually diagnosed in children and young adults, and the mandible is more affected than the maxilla. The following is a case report of a 12-year-old female patient with Garre's osteomyelitis of the mandible due to an infection of a root canal-treated tooth. Without surgical intervention, the patient's symptoms were relieved through nonsurgical root canal re-treatment with long-term calcium hydroxide placement. A cone-beam computed tomography image obtained 6 months after treatment completion displayed complete healing of the periapical lesion and resolution of the peripheral reactive buccal bone. Due to the clinical features of Garre's osteomyelitis, which is characterized by thickening of the periosteum, it can be mistaken for other diseases such as fibrous dysplasia. It is important to correctly diagnose Garre's osteomyelitis based on its distinctive clinical features to avoid unnecessary surgical intervention, and it can lead to minimally invasive treatment options.

Initial screening for dental abnormalities identified by labial and buccal photographs in dogs and cats.

OBJECTIVE: To evaluate the dental abnormalities by visually assessing the labial and buccal photographs in dogs and cats and analyze their prevalence based on age and breed. ANIMALS: 1,096 client-owned dogs and 775 client-owned cats. METHODS: Data were collected from patients who visited 26 private veterinary clinics from January to December 2022. Each animal was evaluated through dental photographs taken from the labial and buccal sides. Correlations between the prevalence of the identified dental abnormalities and age, craniofacial type, and breed, were analyzed. RESULTS: Calculus, discoloration, epulis, fractured teeth, gingival recession, gingivitis, malocclusion, missing teeth, and persistent deciduous teeth could be identified by analyzing the dental photographs in both dogs and cats. Enamel defects in dogs and tooth resorption in cats could be identified. Brachycephalic dogs had a significantly higher prevalence of malocclusion (OR, 1.93; 95% CI, 1.36 to 2.75) and missing teeth (OR, 3.63; 95% CI, 2.71 to 4.91) compared to nonbrachycephalic dogs. Brachycephalic cats had a significantly higher prevalence of fractured teeth (OR, 1.95; 95% CI, 1.24 to 3.04) and a lower prevalence of gingival recession (OR, 0.30; 95% CI, 0.15 to 0.55) compared to nonbrachycephalic cats. Calculus, persistent deciduous teeth, and possibly gingivitis could be identified in dogs and cats by analyzing labial and buccal photographs. The assessment of some dental abnormalities such as fractured teeth, missing teeth, and tooth resorption can be limited without a complete dental examination under anesthesia. CLINICAL RELEVANCE: Although the assessment of dental conditions may be underestimated, the data on the prevalence of the dental abnormalities evaluated through the photographs could be utilized for screening dental diseases.

Benefits of fungal-to-bacterial quorum quenching as anti-biofouling strategy in membrane bioreactors for wastewater treatment and water reuse.

This study addresses membrane biofouling in membrane bioreactors (MBRs) by exploring fungal-to-bacterial quorum quenching (QQ) strategies. While most research has been focused on bacterial-to-bacterial QQ tactics, this study identified fungal strain Vanrija sp. MS1, which is capable of degrading N-acyl-homoserine lactones (signaling molecules of Gram-negative bacteria). To determine the benefits of fungal over bacterial strains, after immobilization on fluidizing spherical beads in an MBR, MS1 significantly reduced the fouling rate by 1.8-fold compared to control MBR, decreased extracellular polymeric substance levels in the biofilm during MBR operation, and favorably changed microbial community and bacterial network, resulting in biofouling mitigation. It is noteworthy that, unlike Rhodococcus sp. BH4, MS1 enhanced QQ activity when switching from neutral to acidic conditions. These results suggest that MS1 has the potential for the effective treatment of acidic industrial wastewater sources such as semiconductor and secondary battery wastewater using MBRs.

Congenital macroglossia treated by 2-stage partial glossectomy.

Persistent macroglossia affects speech, swallowing, and the dentofacial skeleton. A range of tongue reduction methods have been proposed to preserve the mobility and sensation of the tongue. However, recent reports have shown that speech or esthetic problems still exists, even after a comprehensive glossectomy in early childhood. Because a large volume reduction of the anterior tongue in young growing children might result in a short tongue tip with functional difficulties, it is important to select the appropriate tongue reduction method considering the growth of the tongue.In the current report, a staged tongue reduction was planned to minimize the functional and esthetic problems after surgery. A 3-year-old girl visited our clinic because of congenital macroglossia, phonation problems, and prognathic appearance of the mandible. The tongue was first reduced by a central glossectomy. The speech intelligibility, tongue movement, and skeletal growth pattern were improved after the first surgery. The secondary peripheral tongue reduction was performed 6 years later to achieve an esthetically pleasing tongue appearance.This 2-stage partial glossectomy, central tongue reduction first followed later by a peripheral tongue reduction, ensures functional integrity of the tongue and can provide an esthetically pleasing result in growing children. The results demonstrated that this strategic combination of a staged tongue reduction can be a successful treatment option for macroglossia.

A randomized clinical trial for comparing the efficacy of desensitizing toothpastes on the relief of dentin hypersensitivity.

The 4-week double-blind clinical trial to manage dentin hypersensitivity (DH) using different desensitizing toothpastes was conducted. 53 participants with DH were enrolled in this trial. The participants were randomized into 3 groups: Group N; no active ingredient-containing toothpaste (Pleasia fluoride-free), Group SC; a toothpaste containing strontium chloride (Sensodyne Original), and Group TP; a toothpaste containing tricalcium phosphate (Vussen S). They were instructed to brush their teeth manually for 3 min, 3 times per day for 4 weeks with the allocated toothpastes, and were assessed at baseline (0), 2, and 4 weeks, respectively. Schiff sensitivity score was recorded to 3 different stimuli (air-blast, cold, and acid) at each assessment. Overall DH was also assessed using a visual analog scale (VAS). The longer participants used the toothpastes, the greater reduction in DH in all groups to the three stimuli. Group TP demonstrated significant reduction of DH compared to group N for air-blast and cold stimuli. Group TP showed significantly lower VAS than group N and SC. Tricalcium phosphate containing toothpaste used in this trial was most useful to reduce DH. It can be one of the treatment options that alleviate DH.

Limited effects of different real groundwaters from three coastal cities in China on the transport of low-concentration nanoplastics in quartz sand.

Nanoplastics (NPs) have been widely detected in soil-groundwater systems. However, to date, the effect of real groundwater on the fate and transport of NPs has been poorly understood. In this study, the transport and retention behaviors of both polystyrene and poly(lactic-co-glycolic acid) NPs (PS NPs and PLGA NPs) in different real groundwaters from three coastal cities in China were explored using column experiments. PS (0.51 and 1.1 µm) and PLGA (1 µm) NPs with a low concentration of 2 mg L-1 were employed. Close observation showed that the transport of PS NPs was much higher than PLGA NPs in different groundwaters, with an average breakthrough curve plateau (C/Co) of ∼0.81 for PS NPs and ∼0.19 for PLGA NPs, respectively. As observed for PLGA, the plastic shape- and size-induced straining may be the reason for the minimal transport. Interestingly, we found that although the physicochemical characteristics of different real groundwaters varied significantly, the transport of certain NPs in real groundwater was similar with negligible differences. Closer inspection indicated that similar pHs of different groundwaters may be the reason contributing to these findings. Further investigation revealed that the transport behaviors of PS and PLGA NPs in real groundwater did not follow the classical DLVO theory. These findings suggest that the fate and transport of NPs in real soil-groundwater systems are much more comprehensive than the prediction based on DLVO theory and need intensive investigation.

Combined effects of microplastics and benz[a]anthracene on cardiotoxicity in zebrafish (Danio rerio) larvae: Size matters.

The size of microplastics (MPs) plays an important role in combined toxic effects including synergistic or antagonistic effects. However, the influence of the size of MPs on the combined toxicity of contaminants remains unclear. In this study, we employed a zebrafish model to investigate the effects of MP size on the combined toxicity of benz[a]anthracene (BaA), a representative polyaromatic hydrocarbon, using three different sizes of polystyrene MPs (PSMPs) (0.2, 1.0, and 10 µm). Treatment of all groups did not result in any mortality of the zebrafish larvae. However, small-sized PSMPs (0.2 µm) enhanced the toxic effect of BaA in larvae such as cardiac defect and disruption of vessel formation. Medium-sized PSMPs (1.0 µm) were boundary in terms of the combined toxic effect; however, large-sized PSMPs (10 µm) alleviated the cardiotoxicity of BaA, including cardiac defect, ROS levels, and cell death. The combined effects showed a correlation with the body burden of MPs and BaA in larvae according to particle size (in the order of 0.2 µm > 1.0 µm > 10 µm). The synergistic effects occurred likely because the small PSMPs facilitated the body burden of BaA, induced excessive ROS by Ahr-mediated activity, and caused cell death in the heart, resulting in increased heart defects in the larvae. In contrast, large PSMPs abated the combined toxic effect through decreased body burden, whereas medium PSMPs form a boundary in combined effects. Therefore, the combined toxic effects of MPs are dependent on their size, which plays an important role in the transport and accumulation of environmental pollutants.

Selective attachment of prokaryotes and emergence of potentially pathogenic prokaryotes on four plastic surfaces: Adhesion study in a natural marine environment.

This study employed 16S rRNA metabarcoding to establish the diversity of prokaryotic communities and specific characteristics of potentially pathogenic prokaryotic primary colonizers of four plastic materials (EPS, expanded polystyrene; PE, polyethylene; PP, polypropylene; and PET, polyethylene terephthalate). Bacteria inhabiting plastic and seawater differ; thus, distinct changes in the attached prokaryotic community were observed over an exposure time of 21 days, specifically on Days 3, 6, 9, and 12-21. Frist colonizers were Gammaproteobacteria and Alphaproteobacteria; Bacilli and Clostridia represented secondary colonizers. On Day 3, Pseudoalteromonas had a relative abundance >80 %; whereas, the prevalence of Vibrio spp. (potentially pathogenic prokaryotes) increased rapidly on Days 6 and 9. However, after Day 12, the prevalence of other potential pathogens, namely, Clostridium spp., steadily increased. Despite the diversity of the plastic surfaces, attached prokaryotes changed over time instead of showing similar adherent diversity in all plastic materials.