# Which radiographic landmark extends inferiorly from the medial pterygoid plate?
A. Nasolabial fold
B. Hamular process
C. Zygomatic process
D. Maxillary tuberosity
The correct answer is B. Hamular process.
The radiographic landmark that extends inferiorly from the medial pterygoid plate is the hamulus (or hamular process) of the sphenoid bone.
The hamular process is a small, hook-like projection that extends downward from the medial pterygoid plate. It is visible on certain radiographic views, such as panoramic or lateral cephalometric radiographs, and serves as an attachment point for structures like the pterygomandibular raphe and the tensor veli palatini muscle.
# A 12 year old patient presents with premature loss of primary teeth. On radiographic examination, a sharply marginated lucency is seen in the area of tooth loss. A biopsy specimen shows a round cell infiltrate with numerous eosinophils. Which of the following diagnosis is suggested?
A. Cherubism
B. Gardener’s syndrome
C. Fibrous dysplasia
D. Langerhans’ cell disease
The correct answer is D. Langerhans’ cell disease.
Explanation:
The clinical presentation of a 12-year-old patient with premature loss of primary teeth, a sharply marginated radiolucency on radiographic examination, and a biopsy showing a round cell infiltrate with numerous eosinophils strongly suggests Langerhans’ cell disease (also known as Langerhans cell histiocytosis, LCH). LCH is a rare disorder characterized by the proliferation of Langerhans cells, often affecting children. In the oral cavity, it commonly presents with premature tooth loss, "floating teeth" due to bone destruction, and sharply defined radiolucent lesions. The biopsy finding of a round cell infiltrate with eosinophils is characteristic, as LCH lesions often contain Langerhans cells (which appear as round cells) and a prominent eosinophilic infiltrate.
Explanation of other options:
A. Cherubism: This is a genetic condition causing bilateral jaw swelling due to fibrous tissue replacement of bone, typically presenting with multilocular radiolucencies and a "cherubic" facial appearance. It is not typically associated with premature tooth loss or eosinophilic infiltrates.
B. Gardner’s syndrome: This is a variant of familial adenomatous polyposis, associated with osteomas, supernumerary teeth, and colorectal polyps. It does not typically cause premature tooth loss or sharply marginated radiolucencies with eosinophilic infiltrates.
C. Fibrous dysplasia: This condition involves the replacement of normal bone with fibrous tissue, leading to expansile, ground-glass radiopaque lesions rather than sharply marginated radiolucencies. It is not associated with eosinophilic infiltrates or premature tooth loss.
Thus, Langerhans’ cell disease best fits the described clinical, radiographic, and histologic findings.
# Dental fluorosis, a tooth defect, is categorized as one of the following:
A. Hypoplasia
B. Aplasia
C. Hyperplasia
D. Heteroplasia
The correct answer is A. Hypoplasia.
Dental fluorosis is a developmental defect of tooth enamel caused by excessive fluoride intake during tooth formation, leading to hypomineralization and hypoplasia of the enamel. It results in incomplete or defective enamel formation, often presenting as white spots, mottling, or pitting.
Explanation of other options:
B. Aplasia: This refers to the absence or complete failure of development of a tissue or organ, which does not apply to dental fluorosis, as the enamel is present but defective.
C. Hyperplasia: This indicates an excessive growth or overdevelopment of tissue, which is not characteristic of fluorosis, where the issue is underdevelopment or defective enamel.
D. Heteroplasia: This term is not commonly used in dental contexts and generally refers to the formation of abnormal tissue in an inappropriate location, which does not describe dental fluorosis.
# Which of the following cells are responsible for acute suppurative inflammation?
A. Plasma cells
B. Macrophages
C. Neutrophils
D. Lymphocytes
The correct answer is C. Neutrophils.
Neutrophils are the primary cells responsible for acute suppurative inflammation, which is characterized by the rapid accumulation of pus (consisting of neutrophils, dead cells, and tissue debris) in response to infection or tissue injury. They are the first responders in acute inflammatory processes, particularly in bacterial infections, and are key in forming abscesses and other suppurative (pus-forming) conditions.
Explanation of other options:
A. Plasma cells: These are involved in humoral immunity, producing antibodies, and are more associated with chronic inflammation or immune responses, not acute suppurative inflammation.
B. Macrophages: These play a role in both acute and chronic inflammation but are more prominent in chronic inflammation and tissue repair, not specifically in suppurative (pus-forming) processes.
D. Lymphocytes: These are primarily involved in adaptive immunity and chronic inflammation, not acute suppurative inflammation.
1. In orthodontic biomechanics, a low moment-to-force ratio typically results in which type of tooth movement?
A. Bodily movement
B. Controlled tipping
C. Uncontrolled tipping
D. Intrusion
E. Extrusion
2. The center of resistance of a single-rooted tooth is located approximately at what distance from the alveolar crest?
A. One-third of the root length
B. One-half of the root length
C. Two-thirds of the root length
D. At the apex
E. At the cervical margin
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.
# 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.
