Dangerous microplastics released from facemasks : Research Finds

 

The Hidden Environmental Cost of Face Masks: How Disposable Masks Contribute to Microplastic Pollution

In the wake of the COVID-19 pandemic, disposable face masks became our everyday armor against an invisible enemy. Billions were produced, worn, and discarded, saving countless lives but leaving a lingering question: What happens to all that waste? A recent study published in Environmental Pollution (2024) by researchers Anna A. Bogush and Ivan Kourtchev from Coventry University sheds light on a troubling side effect—disposable masks as a sneaky source of microplastics and harmful chemicals leaching into our environment. If you're concerned about plastic pollution, ocean health, or the long-term legacy of the pandemic, this is a must-read. Let's dive into the findings and explore what it means for our planet.

The Pandemic's Plastic Boom: A Quick Recap

Remember 2020? As the world grappled with COVID-19, face masks went from niche medical gear to global essentials. The World Health Organization estimated healthcare alone needed 89 million masks monthly, while global usage hit a staggering 129 billion per month. These disposable face masks (DFMs)—think surgical masks and respirators—were hailed as lifesavers, blocking droplets and reducing virus transmission.

But here's the catch: Most DFMs are made from polypropylene (PP), a durable plastic, layered with other materials like polyethylene (PE) or nylon. They're not biodegradable, and improper disposal turned streets, beaches, and rivers into dumping grounds. Studies show littered masks spiked exponentially during the pandemic, with estimates of 3.4 billion discarded daily. That's not just trash—it's a ticking time bomb for microplastic pollution.

Microplastics (MPs) are tiny plastic particles under 5mm, infamous for infiltrating food chains, water supplies, and even human bodies. The Coventry study compares how different mask types release MPs and chemicals into water, mimicking environmental exposure. Spoiler: It's worse than you might think.

Unmasking the Study: What the Researchers Did

Bogush and Kourtchev tested five common DFM types:

• Surgical/medical masks: Type I (MMI), Type II (MMII), and Type IIR (MMIIR, fluid-repellent).
• Filtering face pieces (respirators): FFP2 (like N95) and FFP3.

They soaked whole new masks in ultra-pure water for 24 hours without shaking—no simulated waves or weathering, just static conditions to check for "built-in" contamination from manufacturing. Water samples were filtered and analyzed using advanced tools like Fourier-Transform Infrared Spectroscopy (FTIR) for MPs and Liquid Chromatography/High-Resolution Mass Spectrometry (LC-HRMS) for chemicals.

This setup highlights a key insight: Even brand-new masks release pollutants, likely from production flaws like fiber breakage or impurities. The results? Eye-opening numbers that underscore why we need better mask design and disposal strategies.

Key Findings: Microplastics Pouring Out

1. Quantity of Microplastics Released

All masks leaked MPs, but respirators were the worst offenders. FFP2 masks released about 1,067 MPs per mask, and FFP3 around 877—three to four times more than surgical masks (239-277 MPs each). Per gram of mask weight, FFP2 stood out at 185 MPs/g, suggesting denser materials or poorer quality control.

Globally, with billions discarded daily, this could mean trillions of MPs entering ecosystems yearly. The study notes no mechanical stress was applied, implying these particles are "pre-loaded" from manufacturing—debris from spinning fibers or contamination during packaging.

2. Size and Shape: Small and Sneaky

Most MPs were tiny—75-90% under 100 microns (about the width of a human hair). The smallest detected were around 10 microns, but even tinier nanoplastics (under 1 micron) are likely present, as other studies confirm. Release order by size: MMIIR > MMII > FFP3 > FFP2 > MMI.

Shapes? Fragments dominated (55-88%), often as broken PP fibers, over straight fibers. This matters because fragments are harder to filter out and more easily ingested by wildlife. Imagine fish mistaking these for food—it's a direct path up the food chain to our plates.

3. Types of Plastics Involved

Polypropylene ruled at 93-97% in surgical masks and 82-83% in respirators, matching their main material. But surprises included traces of PE, polycarbonate (PC), polyester/PET, nylon (PA), polyvinylchloride (PVC), and ethylene-propylene copolymer. Respirators released more variety (17-18% non-PP), possibly from ear loops or nose clips.

This diversity hints at cross-contamination in production or use of recycled plastics, amplifying pollution risks.

Chemical Additives: The Silent Leakers

Masks aren't just plastic—they contain additives for flexibility, color, or performance. The study screened for bisphenols (endocrine disruptors linked to hormone issues) and found bisphenol B (BPB) in MMII (0.25 μg/L) and MMIIR (0.42 μg/L). BPB, a BPA substitute, isn't typically in PP but could come from impurities or other components. Daily global release? Up to 214 kg—enough to contaminate vast water bodies.

Even more alarming: High levels of 1,4-bis(2-ethylhexyl) sulfosuccinate (DOSS, 115-164 μg/L in MMII and MMIIR). Used as an emulsifier in cosmetics and food, DOSS was a key ingredient in oil spill dispersants like those in the Deepwater Horizon disaster. While considered "safe" in small doses, it may disrupt thyroid hormones and harm aquatic life.

No bisphenols or DOSS in respirators, but other studies flag heavy metals and phthalates in masks, adding to the toxic cocktail.

Environmental and Health Impacts: Why It Matters

These findings aren't abstract—they spell real trouble.

Environmental Toll

• Wildlife Harm: MPs from masks entangle animals or get ingested, blocking guts or leaching toxins. Studies show diatoms adsorb them, copepods reproduce less, and zebrafish accumulate them in tissues.
• Ecosystem Ripple: As "carriers," MPs transport pollutants like heavy metals or PAHs, amplifying contamination in rivers, oceans, and soils.
• Pandemic Legacy: With 0.15-0.39 million tons of mask waste potentially reaching oceans yearly, this adds to the 14 million tons of plastic entering seas annually.

Human Health Risks

• Inhalation and Ingestion: MPs in masks could enter lungs during wear, or we consume them via seafood. One study found MPs in nasal mucus from mask users.
• Toxicity: Accumulation may cause inflammation, immune issues, or hypersensitivity. Chemicals like BPB disrupt hormones, potentially affecting fertility or development.
• Pathogen Hitchhikers: Masks can harbor bacteria or viruses on MP surfaces, increasing infection risks if inhaled.

The study emphasizes smaller MPs (<100 μm) are most concerning—they evade filters and bioaccumulate easily.

What Can We Do? Solutions and Hope

This isn't doom and gloom—it's a call to action. The researchers urge science-based policies:

• Improve Production: Mandate MP-free manufacturing with better quality control and recycled materials screening.
• Promote Alternatives: Shift to reusable, washable masks or biodegradable options.
• Better Waste Management: Use the "5R" strategy (Reduce, Reuse, Recycle, Redesign, Restructure). Add labeled bins in public spaces and guidelines for safe disposal.
• Tech Innovations: Develop MP removal methods like biochar adsorption or froth flotation for water treatment.
• Policy Push: Governments should regulate PPE waste like other plastics, with global collaboration to track and mitigate.

As individuals, opt for reusable masks, dispose properly (not litter!), and support eco-friendly brands. Small changes add up—remember, the pandemic taught us collective action works.

Wrapping Up: A Masked Threat We Can't Ignore

The Coventry study reveals disposable face masks as an overlooked microplastic hotspot, releasing hundreds to thousands of particles per mask, plus chemicals like BPB and DOSS. Post-COVID, with usage still high in healthcare and travel, this pollution persists. It's a reminder that solutions to one crisis (health) can spark another (environmental).

By understanding these risks, we can push for sustainable PPE. Share this if it resonates—let's unmask the problem and protect our planet.

REFERENC: https://www.sciencedirect.com/science/article/pii/S0269749124005062

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MCQs in Orthodontics - Brackets in Orthodontics

# An orthodontist is using a bracket with a 0.022-inch slot. Which of the following is the most significant disadvantage of using a wire that is not fully seated in this slot?
A. Inability to express the full programmed torque and angulation.
B. Increased friction between the wire and the bracket.
C. Higher risk of bracket debonding.
D. Reduced anchorage control.

# A patient presents with a history of nickel allergy. What type of orthodontic bracket would be the most appropriate choice to avoid an allergic reaction?
A. Stainless steel brackets.
B. Ceramic brackets.
C. Nickel-titanium brackets.
D. Gold-plated brackets.

# What is the primary advantage of a self-ligating bracket system compared to a conventional bracket system with elastomeric ligatures?
A. Increased control over individual tooth rotation.
B. Improved oral hygiene due to less plaque accumulation.
C. Reduced treatment time due to increased friction.
D. The ability to use smaller archwires.

# A patient reports a sharp edge on their ceramic bracket that is causing soft tissue irritation. What is the most effective clinical intervention to resolve this issue?
A. Applying orthodontic wax.
B. Complete debonding of the bracket.
C. Changing to a smaller archwire.
D. Smoothing the sharp edge with a finishing bur.

# What is the clinical significance of the bracket's slot size in relation to a specific archwire?
A. It is critical for the expression of the bracket's programmed prescription.
B. It controls the level of friction during sliding mechanics.
C. It determines the amount of force applied to the tooth.
D. It dictates the type of adhesive to be used.

# Which of the following is the most common cause of early bracket debonding in the clinical setting?
A. Incorrect bracket placement.
B. Excessive orthodontic forces.
C. Using the wrong type of adhesive.
D. Insufficient enamel etching.

# What is the primary function of the tie wings on a conventional orthodontic bracket?
A. To attach to the archwire using ligatures.
B. To provide a greater surface area for bonding.
C. To act as a handle for bracket placement.
D. To increase the stability of the bracket on the tooth.

# A patient with ceramic brackets has a significant interproximal contact. What is the main risk when debonding these brackets without proper technique?
A. Fracture of the ceramic bracket.
B. Damage to the archwire.
C. Loss of the interproximal contact point.
D. Enamel fracture or crazing.

# Which of the following describes the key difference in force application between a conventional bracket and a passive self-ligating bracket?
A. Passive self-ligating brackets apply more continuous force.
B. Passive self-ligating brackets require a larger archwire.
C. Conventional brackets have less friction.
D. Conventional brackets use a sliding door mechanism.

# What is the primary purpose of the 'in-out' dimension of a bracket?
A. To control the bucco-lingual position of the tooth.
B. To control the torque of the tooth.
C. To control the vertical position of the tooth.
D. To control the mesio-distal position of the tooth.

# During debonding of a bracket, a dental instrument should be used to apply force. Where should this force be applied to minimize the risk of enamel damage?
A. In the center of the bracket base.
B. At the bracket-adhesive interface.
C. On the occlusal tie wings.
D. At the mesial and distal edges of the bracket base.

# What is the clinical significance of a bracket's 'twin' design?
A. It is less visible than single brackets.
B. It allows for the use of two separate archwires.
C. It reduces the amount of friction during sliding mechanics.
D. It provides greater control over rotational movements.

# What is the primary disadvantage of using lingual brackets?
A. The treatment takes significantly longer.
B. The patient's speech can be significantly affected.
C. They require a wider archwire.
D. They are more prone to debonding.

# Which of the following represents the correct order of clinical steps for a direct bracket bonding procedure?
A. Rinse, prime, etch, bond, cure.
B. Rinse, etch, prime, bond, cure.
C. Clean, etch, rinse, dry, apply primer, apply adhesive, cure.
D. Etch, rinse, prime, bond, cure.

# What is the primary function of the 'torque in the base' feature of a bracket?
A. To reduce friction during sliding mechanics.
B. To pre-program a specific bucco-lingual root inclination.
C. To control the mesio-distal angulation of the tooth.
D. To increase the bond strength to the enamel.

# What is the main challenge associated with using ceramic brackets on mandibular incisors?
A. Lower bond strength compared to metal brackets.
B. The risk of enamel wear on opposing maxillary teeth.
C. Aesthetic shortcomings.
D. Higher friction during sliding mechanics.

# Which of the following is a primary biomechanical advantage of using a Damon self-ligating bracket system?
A. Reduced archwire friction.
B. The ability to use smaller archwires.
C. Elimination of the need for elastics.
D. Increased rotational control.

# What is the clinical rationale for using a bracket with a 0.022-inch slot instead of a 0.018-inch slot?
A. The 0.022-inch slot system has lower friction.
B. It allows for the use of larger, more rigid archwires.
C. The 0.022-inch slot system provides more precise finishing.
D. It is more aesthetic than the 0.018-inch slot.

# Which of the following describes the purpose of a bracket-base pad with a 'mesh' design?
A. To increase the bracket's flexibility.
B. To reduce the amount of adhesive required.
C. To create a strong mechanical interlock with the adhesive.
D. To allow for passive ligation.

# What is the primary role of a primer in the orthodontic bonding procedure?
A. To clean the tooth surface.
B. To etch the enamel surface.
C. To improve the wettability and adhesion of the bonding material to the etched enamel.
D. To act as a light-curing adhesive.

# A patient undergoing orthodontic treatment experiences recurrent soft tissue irritation from the bracket hooks. What is the most effective long-term solution?
A. Removing the bracket and rebonding it.
B. Applying orthodontic wax.
C. Trimming or smoothing the hooks with a bur.
D. Prescribing an analgesic.

# In a pre-adjusted edgewise appliance, what does the term 'in-out' correspond to?
A. The angulation of the bracket slot.
B. The rotational torque.
C. The thickness of the bracket base.
D. The vertical height of the bracket on the tooth.

# What is the primary advantage of a single-wing bracket over a twin-wing bracket?
A. Increased rotational control.
B. Higher friction for enhanced sliding.
C. Reduced visibility for aesthetics.
D. Greater bond strength.

# A patient has ceramic brackets on their anterior teeth. During the finishing stage, the orthodontist notices a discrepancy in torque. What is the most likely cause of this issue?
A. The patient's diet.
B. The bracket's 'in-out' dimension.
C. A manufacturing defect in the brackets.
D. The use of an excessively flexible wire.

# What is the primary function of a bracket's 'angulation' feature?
A. To reduce friction.
B. To ensure correct vertical positioning of the tooth.
C. To correct bucco-lingual inclination.
D. To control the mesio-distal tip of the tooth.

# Which of the following is a significant drawback of using plastic brackets?
A. High bond strength.
B. Inability to accommodate an archwire.
C. Poor dimensional stability and susceptibility to staining.
D. Excellent aesthetics.

# An orthodontist is using a self-ligating bracket with an active clip. What is the primary characteristic of this type of bracket?
A. It is made exclusively of metal.
B. It requires the use of elastomeric ligatures.
C. The clip has a 'passive' role and does not contact the wire.
D. The clip applies a light force on the wire.

# What is the main function of the 'hooks' on an orthodontic bracket?
A. To anchor elastics, springs, or other auxiliaries.
B. To provide a reference point for bracket placement.
C. To aid in the debonding procedure.
D. To provide a point for direct archwire ligation.

# Which of the following describes the key characteristic of a 'low-friction' bracket system?
A. It requires frequent archwire changes.
B. It is designed for use with heavy orthodontic forces.
C. It utilizes a ligation method that minimizes contact with the archwire.
D. It is only available in ceramic materials.

# What is the primary clinical benefit of a direct-bond bracket base that has a concave contour?
A. Better fit and seal to the tooth surface.
B. Improved aesthetic appearance.
C. Reduced risk of enamel crazing.
D. Enhanced rotational control.

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THESIS TOPICS OF MDS ORTHODONTICS IN BPKIHS DONE BY MDS POST GRADUATE RESIDENTS

 This is a compilation of all the thesis topics done at B.P. Koirala Institute of Health Sciences, Dharan, Nepal, by postgraduate residents in the Department of Orthodontics and Dentofacial Orthopedics.

1. ORIENTATION AND POSITION OF HYOID BONE IN ORTHODONTIC PATIENTS WITH DIFFERENT DENTOFACIAL GROWTH PATTERNS REPORTING TO CODS, BPKIHS: Dr. Bhushan Bhattarai, July 2014

2. THE SHAPE, SIZE, AND BRIDGING OF THE SELLA TURCICA IN SKELETAL CLASS I, II & III ADULT ORTHODONTIC PATIENTS, REPORTING TO CODS, BPKIHS: Dr. Gunjan Kumar Shrestha, July 2014

3. PHARYNGEAL WIDTHS COMPARISON IN DIFFERENT SKELETAL MALOCCLUSIONS AND GROWTH PATTERNS OF PATIENTS VISITING DEPARTMENT OF ORTHODONTICS, BPKIHS: Dr. Nabin Kumar Chaudhary, December 2020

4. CORRELATION BETWEEN DENTAL ARCH WIDTH AND VERTICAL FACIAL MORPHOLOGY IN PATIENTS SEEKING ORTHODONTIC TREATMENT IN BPKIHS, DHARAN, NEPAL: Dr. Subash Shrestha, May 2023

5. NEPALESE TRANSLATION AND VALIDATION OF THE ORAL AESTHETIC SUBJECTIVE IMPACT SCORE (OASIS) QUESTIONNAIRE: Dr. Sushant Pandey, June 2024

6. CORRELATION OF CRANIOFACIAL MEASUREMENTS ON A STANDARDIZED LATERAL PHOTOGRAPH WITH ANALOGOUS MEASUREMENTS ON A LATERAL CEPHALOGRAM: Dr. Raman Dhungel, August 2025

More topics will be updated soon.

MDS Orthodontics - Thesis Topics

 These are some very useful thesis topics that are practically useful and doable by postgraduate students.

## 1. Cephalometric and Radiographic Studies cephalometric analysis in orthodontic treatment planning

These studies utilize 2D radiographs (Lateral Cephalograms and OPGs) which are widely available.

1. Cephalometric Norms for a Specific Nepalese Ethnic Group: Establish Steiner's or Tweed's cephalometric norms for a specific population (e.g., Newar, Rai, Gurung) to create a local database.

   • Practical Application: Provides more accurate diagnostic standards for local populations instead of relying solely on Caucasian norms.

2. Soft Tissue Profile Changes after First Premolar Extractions: A retrospective study evaluating changes in the lips and chin position in Class I bimaxillary protrusion cases.

   • Practical Application: Helps in predicting esthetic outcomes and managing patient expectations regarding facial changes.

Navigating Advanced Dental Education: Fellowships, Clerkships, and Specializing in Cleft Lip and Palate Orthodontics

I. Introduction to Advanced Dental Training

This report provides a comprehensive overview of advanced educational pathways within the medical and dental fields, specifically distinguishing between fellowships and clerkships. The primary aim is to offer detailed guidance for orthodontists holding a Master of Dental Surgery (MDS) degree who seek to pursue further specialization in cleft lip and palate orthodontics. The information presented herein is designed to equip dental professionals with the knowledge necessary to make informed decisions regarding their advanced training and career trajectory.

Your specific interest in cleft lip and palate orthodontics underscores a desire for highly specialized, multidisciplinary training that extends beyond a general orthodontic residency. This report will address the unique requirements, opportunities, and challenges inherent in this niche field, providing a structured pathway for aspiring specialists.

II. Understanding Fellowships in Medical and Dental Fields

A. What is a Fellowship?

A fellowship represents a period of highly specialized medical or dental training undertaken after the successful completion of a core specialty training program, such as a residency. In the United States and Canada, during this advanced training period, the individual is formally known as a "fellow" or "fellow physician". For dentists, a fellowship typically constitutes a post-residency experience with a concentrated focus on a very specific area of practice, such as oral and maxillofacial surgery or, pertinently for this report, craniofacial orthodontics.

It is important to distinguish this clinical training fellowship from honorary fellowships, such as a "Fellowship in the Academy of Dentistry International".While the latter is a distinctive honor bestowed upon individuals for outstanding accomplishments and contributions to the dental profession (e.g., in clinical practice, research, education, or public service), it does not represent a period of structured clinical or research training in a subspecialty. The focus of this report is exclusively on the clinical and research-oriented training fellowships that lead to advanced specialization.

B. Purpose and Benefits of Fellowships

The fundamental purpose of a medical or dental fellowship is to cultivate expert practitioners within highly specialized subspecialties.2 Fellowships serve as a crucial transitional phase, enabling a resident to evolve into a fully independent specialist.2 This period is invaluable for forming professional connections and accessing advanced job opportunities within the chosen subfield.

Fellowship programs are characterized by their provision of significant, practical work experience, often granting fellows a substantial degree of responsibility early in their training. During this time, fellows collaborate closely with seasoned specialists, allowing them to profoundly deepen their clinical experience and knowledge within their specific subspecialty. Upon the successful completion of a fellowship program, the physician or dentist earns the esteemed title of "fellowship-trained." This designation signifies the highest level of dedication to their chosen field and qualifies them to practice medicine or dentistry independently within their subspecialty without direct supervision. Beyond direct patient care, achieving fellowship-trained status can enhance patient trust and open avenues for future leadership roles, including the opportunity to train subsequent generations of fellows.

C. Typical Duration and Structure of Fellowships

The typical duration of a medical or dental fellowship varies, generally ranging from one to three years, depending on the specific subspecialization. For instance, many craniofacial orthodontics fellowships are structured as 12-month programs. These programs are designed to provide advanced training within a highly focused subspecialty, with the explicit aim of refining and deepening a practitioner's expertise and skills beyond the scope of their initial residency training. The structure of fellowships consistently integrates several key components: intensive clinical training, comprehensive didactic instruction, and dedicated research activities. Fellows engage in hands-on patient care, participate in specialized conferences and seminars, and often undertake a significant research project to contribute to the scientific body of knowledge in their subspecialty.

III. Understanding Clerkships in Medical and Dental Fields

MCQs in Orthodontics - Orthodontic Growth and Development Assessment

# Which of the following terms describes an increase in the number of cells?
A. Hypertrophy
B. Maturation
C. Accretion
D. Hyperplasia

# The concept that growth occurs along an axis from head to tail is known as which growth pattern?
A. Anteroposterior
B. Proximodistal
C. Somatic
D. Cephalocaudal

# According to Scammons' curves, which tissue system exhibits the most rapid growth during the first few years of life, followed by a plateau?
A. Genital system
B. General body growth
C. Lymphoid system
D. Neural system

# Which theory of craniofacial growth posits that growth occurs primarily due to adaptive responses of the skeletal tissues to functional demands of surrounding soft tissues and spaces?
A. Sutural theory
B. Servosystem theory
C. Cartilage theory
D. Functional Matrix Theory

# The primary mechanism for the increase in size of the cranial vault after birth is:
A. Surface remodeling on the external surface of the vault
B. Endochondral ossification at the cranial base
C. Appositional growth at the condylar cartilage
D. Intramembranous bone formation at the sutures

# Which cranial base synchondrosis typically fuses last, continuing to contribute to anteroposterior cranial base growth into late adolescence?
A. Pterygomaxillary synchondrosis
B. Spheno-ethmoidal synchondrosis
C. Intersphenoid synchondrosis
D. Spheno-occipital synchondrosis

# Forward and downward growth of the maxilla primarily occurs through:
A. Appositional growth at the alveolar processes
B. Endochondral ossification within the maxilla itself
C. Direct bone formation at the midpalatal suture
D. Bone deposition at the maxillary sutures and surface remodeling

# Which of the following is the primary mechanism for the growth of the mandible during childhood?
A. Intramembranous ossification of the corpus
B. Endochondral ossification at the condylar cartilage
C. Growth at the symphysis
D. Sutural growth at the posterior border of the ramus

# According to Lavergne and Gasson's classification, which type of mandibular rotation refers to the rotation of the basal bone relative to the cranial base?
A. Intramatrix rotation
B. Matrix rotation
C. Total rotation
D. Alveolar rotation

# A patient with a high Frankfort-Mandibular Plane Angle (FMA) and a tendency towards an anterior open bite often exhibits which of Tweed's growth patterns?
A. Type A (Average/Mesofacial)
B. Type B (Horizontal/Brachyfacial)
C. Type C (Vertical/Dolichofacial)
D. Type D (Unclassified)

# Which pharyngeal arch gives rise to the muscles of mastication and the maxilla/mandible?
A. First pharyngeal arch
B. Second pharyngeal arch
C. Third pharyngeal arch
D. Fourth pharyngeal arch

# The primary palate develops from the fusion of which embryonic structures?
A. Two lateral palatine processes
B. Nasal septum and palatal shelves
C. Frontonasal prominence and mandibular prominences
D. Two medial nasal prominences and two maxillary prominences

# At what approximate gestational age does the fusion of the secondary palate typically begin?
A. Week 4
B. Week 6
C. Week 7-8
D. Week 10

# The primary driving force for the elevation of the palatal shelves during secondary palate formation is widely attributed to:
A. Rapid bone growth within the shelves
B. Tongue growth pushing the shelves upward
C. Intrinsic mesenchymal turgor pressure due to hyaluronic acid accumulation
D. Muscle contractions within the shelves

# Programmed cell death (apoptosis) plays a crucial role in the fusion of the palatal shelves by eliminating which specific tissue?
A. Nasal septal cartilage
B. Medial edge epithelium (MEE)
C. Mesenchymal cells of the shelves
D. Oral epithelial cells on the superior surface

# Which of the following maternal conditions during pregnancy is a known environmental factor that increases the risk of cleft palate?
A. Maternal anemia
B. Use of certain anticonvulsant medications (e.g., phenytoin)
C. Maternal hypothyroidism
D. Excessive intake of Vitamin C

# The neonatal line in enamel and dentin is formed as a result of:
A. Physiological stress associated with birth
B. Genetic predisposition for enamel hypoplasia
C. Trauma during eruption of primary teeth
D. Pre-natal systemic illness

# Which of the following conditions would typically lead to a thinner or less distinct neonatal line?
A. Diabetic mother
B. Low birth weight
C. Elective Caesarean section delivery
D. Asphyxia in the newborn