Oxidative stress, biofilm-formation and activity responses of P. aeruginosa to microplastic-treated sediments: Effect of temperature and sediment type.

Climate change and plastic pollution are the big environmental problems that the environment and humanity have faced in the past and will face in many decades to come. Sediments are affected by many pollutants and conditions, and the behaviors of microorganisms in environment may be influenced due to changes in sediments. Therefore, the current study aimed to explore the differential effects of various microplastics and temperature on different sediments through the metabolic and oxidative responses of gram-negative Pseudomonas aeruginosa. The sediments collected from various fields including beaches, deep-sea discharge, and marine industrial areas. Each sediment was extracted and then treated with various microplastics under different temperature (-18, +4, +20 and 35 °C) for seven days. Then microplastics were removed from the suspension and microplastic-exposed sediment samples were incubated with Pseudomonas aeruginosa to test bacterial activity, biofilm, and oxidative characteristics. The results showed that both the activity and the biofilm formation of Pseudomonas aeruginosa increased with the temperature of microplastic treatment in the experimental setups at the rates between an average of 2-39 % and 5-27 %, respectively. The highest levels of bacterial activity and biofilm formation were mainly observed in the beach area (average rate +25 %) and marine industrial (average rate +19 %) sediments with microplastic contamination, respectively. Moreover, oxidative characteristics significantly linked the bacterial activities and biofilm formation. The oxidative indicators of Pseudomonas aeruginosa showed that catalase and glutathione reductase were more influenced by microplastic contamination of various sediments than superoxide dismutase activities. For instance, catalase and glutathione reductase activities were changed between -37 and +169 % and +137 to +144 %, respectively; however, the superoxide dismutase increased at a rate between +1 and + 21 %. This study confirmed that global warming as a consequence of climate change might influence the effect of microplastic on sediments regarding bacterial biochemical responses and oxidation characteristics.

A Comparative Study on the Interaction Between Protein and PET Micro/Nanoplastics: Structural and Surface Characteristics of Particles and Impacts on Lung Carcinoma Cells (A549) and Staphylococcus aureus.

The interaction between particles and proteins is a key factor determining the toxicity responses of particles. Therefore, this study aimed to examine the interaction between the emerging pollutant polyethylene terephthalate micro/nanoplastics from water bottles with bovine serum albumin. The physicochemical characteristics of micro/nanoplastics were investigated using nuclear magnetic resonance, x-ray diffraction, Fourier transform infrared, dynamic light scattering, and x-ray energy dispersive spectroscopy after exposure to various concentrations and durations of protein. Furthermore, the impact of protein-treated micro/nanoplastics on biological activities was examined using the mitochondrial activity and membrane integrity of A549 cells and the activity and biofilm production of Staphylococcus aureus. The structural characteristics of micro/nanoplastics revealed an interaction with protein. For instance, the assignment of protein-related new proton signals (e.g., CH2, methylene protons of CH2O), changes in available protons s (e.g., CH and CH3), crystallinity, functional groups, elemental ratios, zeta potentials (-11.3 ± 1.3 to -12.4 ± 1.7 to 25.5 ± 2.3 mV), and particle size (395 ± 76 to 496 ± 60 to 866 ± 82 nm) of micro/nanoplastics were significantly observed after protein treatment. In addition, the loading (0.012-0.027 mM) and releasing (0.008-0.013 mM) of protein also showed similar responses with structural characteristics. Moreover, the cell-based responses were changed regarding the structural and surface characteristics of micro/nanoplastics and the loading efficiencies of protein. For example, insignificant mitochondrial activity (2%-10%) and significant membrane integrity (12%-28%) of A549 cells increased compared with control, and reductions in bacterial activity (5%-40%) in many cases and biofilm production specifically at low dose of all treatment stages (13%-46% reduction) were observed.

Year-long and seasonal differences of PM2.5 chemical characteristics and their role in the viability of human lung epithelial cells (A549).

Fine particulate matters-PM2.5 in the air can have considerable negative effects on human health and the environment. Various human cell-based studies examined the effect of PM2.5 on human health in different cities of the world using various chemical parameters. Unfortunately, limited information is available regarding the relationship between toxicity and chemical characteristics of PM2.5 collected in Istanbul, Türkiye, located in one of the most populated cities in the world. To investigate the chemical characteristics and cytotoxicity of PM2.5 in Istanbul, samples were collected for 12 months, then potentially toxic metals, oxidative potential, and particle indicators (e.g., functional groups and elements) were determined, and the cytotoxicity of PM2.5 on human A549 lung alveolar epithelial cells was examined. The mean PM2.5 mass concentration was 24.0 ± 17.4 µg m-3 and higher in cold months compared to other seasons. Moreover, the results of the metals, elemental, and functional groups indicated that seasonal and monthly characteristics were influenced by the regional anthropogenic sources and photochemistry input. The cytotoxicity results also showed that the viability of A549 cells was reduced with the exposure of PM2.5 (30-53%) and higher cytotoxicity was obtained in summer compared to the other seasons due to the impact of the metals, elements, and oxidative characteristics of PM2.5.

Exposure to phagolysosomal simulated fluid altered the cytotoxicity of PET micro(nano)plastics to human lung epithelial cells.

The occurrence of micro(nano)plastics into various environmental and biological settings influences their physicochemical and toxic behavior. Simulated body fluids are appropriate media for understanding the degradation, stability, and interaction with other substances of any material in the human body. When the particles enter the human body via inhalation, which is one of the avenues for micro(nano)plastics, they first come into contact with the lung lining fluid under neutral conditions and then are phagocytosed under acidic conditions to be removed. Therefore, it is important to examine the physicochemical transformation and toxicity characteristics after interaction with phagolysosomal simulant fluid (PSF). Here, we focused on exploring how the physicochemical differences (e.g. surface chemistry, elemental distribution, and surface charge) of micro(nano)plastics under pH 4.5 phagolysosome conditions impact cytotoxicity and the oxidative characteristics of lung epithelia cells. The cytotoxicity of lung epithelia cells to those treated with PSF and non-treated micro(nano)plastics was tested by various viability indicators including cell counting kit-8 (CCK-8), MTT, and LDH. Furthermore, the cytotoxicity background was examined through the oxidative processes (e.g. reactive oxygen species, antioxidant, superoxide dismutase (SOD), catalase, and reduced glutathione). The results showed that all tested surface physicochemical characteristics were significantly influenced by the phagolysosome conditions. The staged responses were observed with the treatment duration, and significant changes were calculated in carbonyl, carbon-nitrogen, and sulfonyl groups. Moreover, the negativity of the zeta potentials declined between exposure of 2-40 h and then increased at 80 h compared to control owing to the chemical functional groups and elemental distribution of the plastic particles. The tested viability indicators showed that the micro(nano)plastics treated with PSF were cytotoxic to the lung epithelia cells compared to non-treated micro(nano)plastics, and SOD was the dominant enzyme triggering cytotoxicity due to the particle degradation and instability.

Sorption of thiamin (vitamin B1) onto micro(nano)plastics: pH dependence and sorption models.

As the carrier of various inorganics and organics from various media, micro(nano)plastics have an impact on the environment and human health. Recently, many studies have examined the sorption of various organics including antibiotics. However, while vitamins have critical roles in the environment and microsystems from humans to plant life, the sorption of vitamins onto micro(nano)plastics are still uninvestigated. Therefore, the aim of this study was to examine the sorption of vitamin B1 onto various micro(nano)plastics from food packages under different pHs using batch technique; sorption kinetics and isotherms models were investigated as well. The results indicated that higher capacities were obtained between 360 min to 1440 min in polypropylene and polyethylene micro(nano)plastics, and similar kinetic behaviors observed in different pHs. However, the sorption responses (sorption capacity, equilibrium time) of polyethylene terephthalate and polystyrene were varied. The sorption kinetics between vitamin B1 and micro(nano)plastics showed that the pseudo-first-order model was better to fit for polyethylene terephthalate and polystyrene compared to the pseudo-second-order kinetics, however it was changed for polypropylene and polyethylene. Moreover, the obtained results suggest a complex nature of vitamin B1 sorption, including both chemical and physical sorption occur under various pHs and polymer types.

Characterizing the interaction between micro(nano)plastics and simulated body fluids and their impact on human lung epithelial cells.

Micro(nano)plastics are considered an emerging threat to human health because they can interact with biological systems. In fact, these materials have already been found in the human body, such as in the lungs. However, limited data are available on the behavior of these materials under biological conditions and their impact on human cells, specifically on alveolar epithelial cells. In this study, micro(nano)plastics were exposed to various simulated biological fluids (artificial lysosomal fluids and Gamble's solution) for 2-80 h. Pristine and treated plastic particles were characterized based on their surface chemistry, zeta potentials, and elemental composition. Various toxicological endpoints (mitochondrial membrane potential, lactate dehydrogenase, protein, and antioxidant levels) were examined using A549 lung carcinoma cells. The surface characteristics of the treated micro(nano)plastics and the toxicological endpoints of A549 cells were found to be influenced by the simulated biological media, specifically with high concentrations of the treated micro(nano)plastics and increasing exposure under biological conditions. Moreover, the toxicological endpoints were strongly linked to the chemistry of plastics and included multiple processes in response to the plastics; different biological pathways were obtained in artificial lysosomal fluid and Gamble's solution.

The effect of micro-osteoperforation on the rate of tooth movement during the alignment stage in patients with mandibular crowding: a randomised controlled trial.

BACKGROUND: Orthodontic treatment is a long process that requires patient cooperation. Risks of side effects such as caries formation, periodontal problems, and root resorption increases as well as problems in patient cooperation arises with longer treatments. Several different techniques were developed that may shorten the treatment time. OBJECTIVE: The aim of this study was to evaluate the effectiveness of micro-osteoperforations (MOPs) performed during the alignment stage. TRIAL DESIGN: Randomized controlled trial. METHODS: Twenty-eight subjects who had crowding in the mandibular arch were included in the study. The first group (4 boys and 10 girls, mean age = 17.21 ± 3.76 years) was treated with MOP (MOP) and the second group (8 boys and 6 girls, mean age = 15.29 ± 1.77 years) was treated without MOP (control). Cephalometric variables, periodontal parameters, Little irregularity index, alignment duration, patient satisfaction, and ease of operation were evaluated. The level of statistical significance was P ≤ 0.05. RESULTS: Alignment duration was shorter (P = 0.000) in the MOP group (105.57 ± 18.34 days) compared to control group (135.86 ± 15.12 days). Alleviating of the crowding was more in the MOP group, compared to the control group in all time points. The pain level in the MOP group in the first appointment was higher compared to control group (P = 0.002). There was no significant difference between the groups in cephalometric parameters. Higher increases were found for gingival index (P = 0.008) and bleeding index (P = 0.039) in the control group compared to MOP group at the end of treatment. LIMITATIONS: The study was a single-centre study. CONCLUSION: Alignment stage was shortened with MOP application. There was no difference between groups for patient satisfaction and pain level except for the first appointment. No difference was observed between the groups regarding cephalometric values. Clinically insignificant inflammation was observed in periodontal tissues for both groups. REGISTRATION: This study was registered at the Clinical Trials Registry (ClinicalTrials.gov NCT03652454).

Elemental, Oxidative and Functional Group Characteristics of Sediments in the Industrial Marine area in Tuzla Aydinli Bay, Istanbul, Turkey Between 2016 and 2020.

This study aimed to examine particle and surface characteristics of sediments from three sampling areas‒the industrial marine area in Aydinli Bay, the Marmara Sea, and the river tributaries of Aydinli Bay in Istanbul, Turkey‒over a period of five years (2016-2020). Since elemental composition and surface functional groups onto sediments characterize sorption of organic and inorganic substances, the study revealed that C, O, Si, and Al were common elements of sediments and Ti, S and Mg were at a relatively low level. The C = O and O-H related groups were at a higher level in the river tributaries and the Marmara Sea than Aydinli Bay. These functional groups have indicated the oxidative or weathering potential of particles. Moreover, the mineralogical nature of the Al-O, Fe-O and Si-O compounds were at a higher level in Aydinli Bay compared to the other sampling fields. Another important surface characteristic was the oxygen to carbon ratio which showed that the oxidation state was higher in the river tributaries.

Co-occurence of antibiotics and micro(nano)plastics: a systematic review between 2016-2021.

Pollution by plastics and antibiotics are emerging issues in the areas of the environment and human health. In recent years, several studies have documented the widespread occurrence of plastic particles in various environmental, as well as human, systems, and much research has focused on possible interactions of contaminants with microplastics. Thus, the co-occurrence of plastics and antibiotics has caused another global problem for the environment and human health. Therefore, we focused on the current knowledge in the field of the co-occurrence of plastics and antibiotics to summarize the available studies. In this review, categorization of the topics, contaminants details, such as polymer type, size and source, antibiotic type, and other experimental parameters were summarized and discussed. This study indicated that the sorption of antibiotics on plastics, antibiotic susceptibility in the presence of plastics, and antibiotic resistance gene onto plastics were the most frequently examined categories in this field. Moreover, the variability in the procedures and the processes, and the heterogeneity data of reporting between different studies on similar topic make it difficult to bring all results together and produce a comprehensive picture of the current knowledge. Therefore, it is suggested that further research should be done using this systematic study.

Changes in the craniofacial structures and esthetic perceptions of soft-tissue profile alterations after distalization and Herbst appliance treatment.

INTRODUCTION: The purpose of this prospective clinical trial is to evaluate the changes of soft tissues and designate the esthetic perceptions of children with Class II malocclusion after Herbst appliance therapy and maxillary molar distalization using stereophotogrammetry. METHODS: Thirty patients were allocated either to Herbst (6 boys and 9 girls; mean age = 11.60 ± 0.82 years) or distalization (4 boys and 11 girls; mean age = 11.46 ± 1.30 years) groups. Dentoskeletal and soft-tissue treatment changes were examined objectively by cephalometric analysis and stereophotogrammetry, respectively. Pre- and posttreatment profile views were evaluated subjectively by orthodontists and laypeople using the 7-point Likert scale. Intra- and intergroup comparisons for the repeated measurements were performed with 2-way variance analysis. Bonferroni test was used for multiple comparisons (P ≤0.05). RESULTS: Greater skeletal changes were observed in the Herbst group than in the distalization group. Maxillary incisor retrusion and mandibular incisor protrusion were observed in the distalization and Herbst groups, respectively. Stereophotogrammetric measurements showed that mandibular body length and lower and anterior facial height increased in both treatment groups. Convexity angle (P = 0.020) and labiomental angle (P = 0.033) were greater in the Herbst group than the distalization group. CONCLUSIONS: The skeletal contribution to correction of maxillomandibular discrepancy was greater in the Herbst group than the distalization group. Significant profile improvements were recorded for both groups with treatment. After both treatments, orthodontists were found to have higher rates of detection in the profiles than laypeople. The esthetic contribution of treatments to the facial profile was found similar in both groups.

Degradation of subµ-sized bioplastics by clinically important bacteria under sediment and seawater conditions: Impact on the bacteria responses.

In this study, we investigated the interaction of submicron-sized bioplastics with environmentally and clinically important bacteria under seawater and sediment conditions. To examine the relationship between submicron-sized bioplastics and bacteria in seawater and sediment, we focused on the bacterial activation and their biochemical key events toward the protein, carbohydrate, lipid, and antioxidant response. In addition, culture-dependent biofilm formation on submicron-sized bioplastics and their characterization was performed. The results indicated that selected bacteria increased their viability both in seawater and sediment with the submicron-sized bioplastics in that the bioplastics decreased their mass at the level of 10-23%. However, the activation level and mechanism affected the polymer type, bacteria, and environmental media, and submicron-sized bioplastics promoted biofilm formation with enhancing basophilic characteristics of biofilms.

Interaction of amino acids with nanoplastic traces and their effect on Staphylococcus aureus.

In this study, we reported the interaction between plastic traces and vital amino acids (L-homocysteine, L-valine, and L-lysine) in an aqueous system and characterized this interaction by Fourier transform infrared spectroscopy and Scanning electron microscopy with energy-dispersive X-ray spectroscopy studies. Bacterial activity and biofilm formation and their characteristics of non-treated and amino acid-treated plastic traces was tested against the Staphylococcus aureus bacterial pathogen. The surface results showed that the carbonyl groups and oxygen to carbon ratios were increased, and the attachment of nitrogen- and sulfur-related substances on the plastic surface occurred by the homocysteine over time. Plastic traces showed particle surface deformation using the main functional groups (e. g. alkyne-alkene, vinyl, secondary alcohols, alkane-methylene) with the increasing lysine treatment; however, decreased oxygen to carbon ratio showed particle anti-aging. The most common functional groups were primarily deformed with the longer exposure to valine. The bacterial activity results showed that the Staphylococcus aureus activities were not primarily changed by the amino acid treatment compared to the non-treated plastic traces. However, amino acid treated plastic traces induced the biofilm formation and its characteristic due to surface deformation of functional groups and alteration of new substances on plastic traces.

Three-dimensional evaluation of smile characteristics in subjects with increased vertical facial dimensions.

INTRODUCTION: Patients seeking orthodontic treatment often have esthetic concerns (ie, they want a better smile). Patients with increased vertical facial dimensions have different smile traits than other patients. This study aimed to compare the smile characteristics of subjects with different vertical facial dimensions and to use stereophotogrammetry to evaluate the changes in facial animation upon smiling. METHODS: One hundred twenty adolescents and young adults (aged 15-25 years) who were referred for orthodontic treatment were divided into 2 groups according to their vertical facial height: increased (n = 30) and normal (n = 30). Three-dimensional stereophotogrammetric images were obtained from the patients during rest and smile. The images were superimposed, and the displacements of specific landmarks were recorded. Linear, angular, and proportional measurements were recorded on the smile and rest images. RESULTS: When smiling, horizontal movement of commissures was less (right, P = 0.038; left, P = 0.009), upper lip elevation was higher (P = 0.014), and the upper lip was shorter (P = 0.014) in the vertical group than in the normal group. In the vertical group, the interlabial gap was increased both at rest and when smiling (P <0.001). Statistically significant differences were found in smile index (P = 0.001), nasolabial fold displacement (P = 0.018), and lip angles (both P = 0.001) between groups. CONCLUSIONS: Group and sex differences were observed when smiling. Careful consideration of these differences will help clinicians in proper diagnosis and treatment planning.

Age-related physicochemical differences in ZnO nanoparticles in the seawater and their bacterial interaction.

To assess the fate and behavior of engineered nanoparticles in the environment, it is important to examine the physicochemical and toxicological transformation of nanoparticles as they age in seawater. In this study, we investigated how aging and seawater conditions altered the physiochemical structure of nanoparticles and affected their interactions with bacteria. For this purpose, zinc oxide nanoparticles were aged under different seawater conditions by keeping them in 1%, 10%, and 100% seawater for 1 day and 20 days. The main physicochemical parameters (surface chemistry, chemical composition, particle size, and zeta potential) and toxicity of aged nanoparticles towards gram-negative Pseudomonas aeruginosa and gram-positive Staphylococcus aureus were examined. The results indicated that aged zinc oxide nanoparticles in various concentrations of seawater changed their surface chemistry, chemical composition, particle size, and zeta potentials. Growth inhibition results were observed in that the inhibition of gram-negative (Pseudomonas aeruginosa) bacteria was higher compared with the gram-positive (Staphylococcus aureus) bacteria, and Staphylococcus aureus activated with the aged zinc oxide nanoparticles. Also, the results showed that the key biochemical factors affected by the aging and seawater concentration.

An insight into the dependency on sample preparation for (eco) toxicity assessment of TiO2 nanoparticles.

Assessing the environmental hazard of nanoparticles can be a challenging task using various testing strategies. However, to our knowledge, no information is available about the impact of the sample preparation on the toxicity and toxicity mechanism of nanoparticles. For this aim, three sample preparation methods and their available toxicity procedures were conducted to examine the (eco) toxicity of TiO2 nanoparticles using bacteria model system. To detail understanding of the effect of sample preparation, the key events on the inhibition were examined by physicochemical and antioxidant responses. The findings showed that the physicochemical and toxicological behavior of the tested TiO2 NPs varied according to the sample preparation method.

Similarities and Discrepancies Between Bio-Based and Conventional Submicron-Sized Plastics: In Relation to Clinically Important Bacteria.

In recent years, many studies have reported the harmful effects of plastic debris both on the environment and on human health. Therefore, the attempt has increased for the replacement of conventional plastics with bioplastics. On the other hand, not only the studies on the effects of bioplastics and conventional plastics in the field of micro-, submicron- and nano-sized are still very limited, but also knowledge of their relationship with clinically important bacteria. In this study, the effect of two end products made from bioplastics and their equivalent end products from conventional plastics were evaluated using clinically important gram-positive and gram-negative bacteria. To evaluate the effect of the submicron-sized bioplastics and conventional plastics on the bacteria, their viability and activation and/or inhibition mechanism were performed towards the main biochemical (protein, carbohydrate, lipid and antioxidant) and physicochemical (particle size, zeta potential, chemical composition, and surface chemistry) phenomenon. This work highlights the similarities and discrepancies between bio-based and conventional submicron-sized plastics in relation to bacteria.

Biofilm Formation of Clinically Important Bacteria on Bio-Based and Conventional Micro/Submicron-Sized Plastics.

Micron/submicron-sized plastic debris in the environment is a global issue of increasing concern and may harm human health. A large number of studies have shown that plastic debris has various toxicological effects on different organisms. Thus, efforts have increased to replace conventional plastics with bioplastics. However, investigations on the relation of submicron-sized bioplastics- and conventional plastics to culture-dependent biofilm formation and their similarities and discrepancies are still very limited. For this purpose, two end products made from bioplastics and their equivalent end products from conventional plastics were used to examine the response of the biofilm formation of selected clinically important bacteria. To evaluate the similarities and differences of submicron-sized bioplastics and conventional plastics on biofilm formation, the physicochemistry (particle size, zeta potential, chemical composition, and surface chemistry) of the tested plastics was examined, as well as the characteristics of the biofilms (categorization, protein/carbohydrate).

Microplastic Occurrences in Sediments Collected from Marmara Sea-Istanbul, Turkey.

Microplastics are persistent, synthetic polymers that have managed to spread even to the most remote places on earth. Studies reporting on the abundance of microplastics have recently increased worldwide, which has raised environmental concerns among scientific communities. Nevertheless, evidence of microplastic contamination from Turkey is limited even though the location is a critical point and the population is higher than most countries in the region. Thus, we aimed to detect microplastics in sediment samples collected from the Marmara Sea in Istanbul-Turkey. In this study, fourteen sediment samples were collected and sub-sampled, then plastic debris was extracted, quantified and characterized by the morphology and polymer structure. The result revealed that all of the samples contained microplastics, and their concentrations ranged between 0.3 and 85.6 g/kg sediment, and the most abundant plastic types were acrylonitrile butadiene styrene, ethylene vinyl acetate, and polystyrene.

Effectiveness of incremental vs maximum bite advancement during Herbst appliance therapy in late adolescent and young adult patients.

INTRODUCTION: The purpose of this research was to compare the effects of Herbst appliance therapy using incremental vs maximum advancement in late adolescent and young adult patients with Class II skeletal malocclusion. METHODS: Forty-two patients with skeletal Class II malocclusion were treated with cast-splint Herbst appliances. The subjects were randomly allocated into 2 groups according to activation type: incremental advancement (IA) and maximum advancement (MA). Initial forward movement in the IA group was 4 to 5 mm and was followed by subsequent bimonthly advancements of 2 mm. Single-step advancement was achieved in the MA group until an edge-to-edge incisor relationship or an overcorrected Class I molar relationship was obtained. Total treatment times were 9.7 ± 1.1 months for the IA group and 9.5 ± 1.1 months for the MA group. Dental, skeletal, and soft tissue measurements were performed on lateral cephalograms taken just before and at the end of the Herbst appliance therapy. Statistical significance was set at P ≤ 0.05. RESULTS: All mandibular skeletal dimensions increased, and improvements of the sagittal maxillomandibular parameters were found in both groups. Protrusion and proclination of the mandibular incisors were greater in the IA group (95.90° ± 5.34°) compared with the MA group (92.04° ± 7.92°). Other dentoalveolar changes in both groups were intrusion of the maxillary first molars, and extrusion of the mandibular first molars and maxillary incisors. The mentolabial sulcus was flattened, soft tissue convexity was reduced, and forward movement of mandibular soft tissues was seen after Herbst therapy. CONCLUSIONS: Similar skeletal, dental, and soft tissue changes were obtained in both groups after Herbst therapy. Greater proclination and more protrusion of the mandibular incisors were found in the IA group.

Changes in pharyngeal airway dimensions following incremental and maximum bite advancement during Herbst-rapid palatal expander appliance therapy in late adolescent and young adult patients: a randomized non-controlled prospective clinical study.

OBJECTIVES: This was a parallel, assessor-blinded, randomized, non-controlled prospective trial with the objective to evaluate and compare the effects of maximum advancement (MA) and incremental advancement (IA) of mandible with cast-splint-type Herbst-rapid palatal expander (RPE) appliance on pharyngeal airway dimensions and hyoid bone position in skeletal Class II late adolescents and young adults. MATERIALS AND METHODS: A total of 48 patients (19 male and 29 female, mean age: 15.45 ± 1.42 years) with skeletal Class II malocclusion were treated with cast-splint Herbst-RPE appliance. Inclusion criteria were skeletal Class II malocclusion, mandibular retrognathia, bilateral Class II molar and canine relationship, increased overjet, normal or decreased vertical dimensions, minimal crowding, and no missing teeth. Enrolled subjects were randomly allocated into two groups according to mandibular advancement type: IA and MA Herbst-RPE therapy. The outcome assessor was blinded. Advancement in MA group was adjusted until tête-à-tête incisor relationship or super Class I molar relationship was obtained. Initial forward movement in IA group was 4-5 mm and followed by bimonthly 2 mm of subsequent advancements. Skeletal, pharyngeal airway, and hyoid measurements were performed using lateral cephalometric films. Statistical significance was set at P value of less than 0.05. RESULTS: Hypopharyngeal airway dimensions (P < 0.000), oropharyngeal airway dimensions (P < 0.001, P < 0.007), and PASmin values (P < 0.010, P < 0.009) were increased and soft palate angle (P < 0.018, P < 0.007) was decreased in MA and IA groups significantly. Hyoid bone measurements revealed a significant difference in H-Cv2 distance (MA: P < 0.002-P < 0.002; IA: P < 0.001-P < 0.043) and H-Cv3 distance (P < 0.005, P < 0.001) for both groups. However, all these changes did not differ among the MA and IA activation groups. ANB°, Wits, overjet, and overbite measurements decreased and SNB°, Co-Gn, Na-Me, ANS-Me, and S-Go increased with the treatment significantly in both mandibular advancement groups (P < 0.000-P < 0.040). CONCLUSIONS: Herbst-RPE appliance provided a similar improvement in the oropharyngeal and hypopharyngeal airway dimensions and similar changes in sagittal and vertical hyoid position for both maximum and IA protocols in patients with skeletal Class II malocclusion. TRIAL REGISTRATION: ISRCTN69743543.