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ADC Practical Exam practice questions

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Question 1Infection prevention and control

Which action is the single most effective routine measure for preventing transmission of healthcare-associated pathogens between patients?

  1. Wearing gloves for every patient contact
  2. Changing the bed linen daily
  3. Disinfecting the floor with chlorine solution
  4. Performing hand hygiene at the correct moments Correct answer.

Explanation

Hand hygiene at the WHO five moments removes transient organisms from the hands and interrupts the main route of cross-transmission in healthcare settings. Gloves, linen changes and floor disinfection are adjuncts and do not replace hand hygiene. Compliance with hand hygiene is therefore the cornerstone of every infection prevention programme.

Question 2Infection prevention and control

A nurse enters a patient room to empty a urinary catheter bag and adjust the infusion pump. According to the WHO five moments, when should hand hygiene be performed?

  1. Only when the hands are visibly soiled
  2. Before touching the patient and after body fluid exposure risk Correct answer.
  3. Only after leaving the room
  4. Once at the start of the shift

Explanation

The five moments specify hand hygiene before touching a patient, before a clean or aseptic procedure, after body fluid exposure risk, after touching a patient and after touching patient surroundings. Emptying a catheter bag creates body fluid exposure risk, so hand hygiene is required both before patient contact and after that exposure. Timing is tied to the moment of care rather than to the room exit.

Question 3Infection prevention and control

Which statement best describes the correct technique for alcohol-based hand rub on visibly clean hands?

  1. Apply a small amount and rub only the palms together
  2. Rub for five seconds then dry the hands with a paper towel
  3. Cover all surfaces and rub until the product has evaporated Correct answer.
  4. Apply the product and rinse with water afterwards

Explanation

Alcohol-based hand rub must cover all surfaces of the hands and wrists, including fingertips, thumbs and web spaces, and be rubbed until dry. The drying time reflects the contact time needed for the alcohol to act. Wiping the product off or rinsing it shortens the exposure and reduces efficacy.

Question 4Infection prevention and control

Under standard precautions, which personal protective equipment is required before entering the room of a patient with an uncontained respiratory secretion risk during suctioning?

  1. A surgical mask only
  2. Gloves, gown, mask and eye protection Correct answer.
  3. Shoe covers and a cap
  4. Gloves and gown only

Explanation

Standard precautions require risk assessment before each task. Suctioning generates splashes and aerosols of respiratory secretions, so gloves, gown, mask and eye protection are all indicated to protect mucous membranes and clothing. Shoe covers and caps are not part of routine standard precautions.

Question 5Infection prevention and control

Which transmission-based precaution is appropriate for a patient with suspected pulmonary tuberculosis?

  1. Droplet precautions with a surgical mask
  2. Airborne precautions with a fit-tested respirator Correct answer.
  3. Standard precautions only
  4. Contact precautions with a gown and gloves

Explanation

Tuberculosis is transmitted by airborne droplet nuclei that remain suspended and travel on air currents, so airborne precautions are required. Healthcare workers entering the room need a fit-tested particulate respirator and the room should be airborne-isolation capable. Surgical masks and gowns do not provide adequate protection against droplet nuclei.

Question 6Infection prevention and control

A patient has Clostridioides difficile diarrhoea. Which combination of measures is most appropriate?

  1. Contact precautions with soap-and-water handwashing and sporicidal environmental cleaning Correct answer.
  2. Standard precautions with no additional cleaning
  3. Airborne precautions with a respirator
  4. Droplet precautions with alcohol hand rub and routine cleaning

Explanation

C. difficile spores survive alcohol and are spread by contact, so contact precautions are required and hands should be washed with soap and water after glove removal. Environmental cleaning must use a sporicidal agent such as chlorine because routine agents do not reliably kill spores. Alcohol rub alone is inadequate during outbreaks of spore-forming organisms.

Question 7Infection prevention and control

Which statement about the use of gloves in clinical practice is correct?

  1. Gloves eliminate the need for hand hygiene before patient contact
  2. Gloves should be worn continuously for a whole shift
  3. Gloves must be changed between patients and hand hygiene performed after removal Correct answer.
  4. Gloves may be washed with alcohol and reused

Explanation

Gloves are single-use items that must be changed between patients and between dirty and clean tasks on the same patient. Hand hygiene is required before donning and after removing gloves because gloves can have micro-perforations and hands may become contaminated during removal. Washing or reusing gloves compromises their barrier function.

Question 8Infection prevention and control

What is the correct sequence for safely removing personal protective equipment after patient care?

  1. Remove mask first, then gloves, then gown
  2. Remove gloves and gown, perform hand hygiene, then remove mask and eye protection Correct answer.
  3. Remove all items while still inside the patient's room without hand hygiene
  4. Remove gloves, then mask, then gown, then eye protection

Explanation

Removal aims to avoid self-contamination by taking off the most contaminated items first. Gloves and gown are removed together, hand hygiene is performed, and then facial protection is removed from behind, followed by a final hand hygiene. Removing the mask first risks contaminating the face and hands.

Question 9Infection prevention and control

Which item is classified as a critical medical device requiring sterilisation before use?

  1. A bedpan
  2. A blood pressure cuff
  3. A stethoscope diaphragm
  4. A surgical instrument entering sterile tissue Correct answer.

Explanation

Devices are classified by the risk of infection if contaminated. Critical items enter sterile tissue or the vascular system and must be sterilised; semicritical items contact mucous membranes and require high-level disinfection; noncritical items touch intact skin and require cleaning and low-level disinfection. Surgical instruments therefore require sterilisation.

Question 10Infection prevention and control

A flexible endoscope used for a colonoscopy has been cleaned and is awaiting high-level disinfection. Which statement best reflects the required process?

  1. Alcohol wipe of the insertion tube is adequate
  2. The device should be stored wet to prevent drying out
  3. Manual cleaning must precede high-level disinfection, and the device must be dried and stored appropriately Correct answer.
  4. Rinsing with tap water is sufficient after manual cleaning

Explanation

Semicritical endoscopes require meticulous manual cleaning to remove organic material before high-level disinfection, because residual bioburden protects microorganisms. After disinfection the device must be rinsed with appropriate water, dried and stored in a way that prevents recontamination and microbial growth. Storage wet encourages biofilm formation.

Question 11Infection prevention and control

Which statement about surgical site infection prevention and antimicrobial prophylaxis is correct?

  1. Prophylaxis should be given within the appropriate window before incision and discontinued within 24 hours Correct answer.
  2. Prophylaxis is unnecessary for any clean surgery
  3. Prophylaxis should continue for seven days after surgery
  4. Antibiotics should be started only if the wound becomes infected

Explanation

Antimicrobial prophylaxis for surgery is most effective when given shortly before incision so that tissue levels peak during the operation. Prolonging prophylaxis beyond the procedure increases resistance and C. difficile risk without reducing surgical site infection. Prophylaxis is indicated for many clean procedures involving implants or when consequences of infection are severe.

Question 12Infection prevention and control

Which factor is a recognised patient-related risk factor for surgical site infection?

  1. Use of sterile drapes
  2. Adequate oxygenation in theatre
  3. Perioperative hyperglycaemia Correct answer.
  4. Correctly timed prophylaxis

Explanation

Poor glycaemic control impairs neutrophil function and wound healing, increasing the risk of surgical site infection. Other patient factors include obesity, smoking, malnutrition and immunosuppression. Sterile drapes, timely prophylaxis and adequate oxygenation are protective measures rather than risk factors.

Question 13Infection prevention and control

Which action best prevents catheter-associated urinary tract infection in a patient with an indwelling catheter?

  1. Using a closed drainage system and removing the catheter as soon as possible Correct answer.
  2. Keeping the drainage bag on the floor for stability
  3. Irrigating the catheter daily with antiseptic
  4. Changing the catheter every 48 hours routinely

Explanation

A closed drainage system prevents environmental organisms from entering the urinary tract, and minimising the duration of catheterisation is the most effective way to reduce risk. Routine catheter changes at fixed short intervals are not recommended. The drainage bag should stay below bladder level and off the floor.

Question 14Infection prevention and control

A central venous catheter is in place. Which practice reduces the risk of central line-associated bloodstream infection?

  1. Scrubbing the hub with antiseptic and using maximal sterile barrier precautions at insertion Correct answer.
  2. Replacing the dressing only when it visibly falls off
  3. Changing the line over a guidewire routinely
  4. Using the line for routine blood sampling without disinfection

Explanation

Prevention of central line-associated bloodstream infection depends on a bundle that includes hand hygiene, maximal sterile barrier precautions at insertion, chlorhexidine skin antisepsis, optimal site selection and daily review of line necessity. Disinfecting the access hub before each use prevents intraluminal contamination. Dressings should be changed on a defined schedule or when soiled or loose.

Question 15Infection prevention and control

Which statement about ventilator-associated pneumonia prevention is correct?

  1. Routine ventilator circuit changes every 24 hours are recommended
  2. Elevating the head of the bed to about 30 to 45 degrees reduces aspiration risk Correct answer.
  3. Sedation should be deep to prevent coughing
  4. Patients should be kept flat in bed at all times

Explanation

Semi-recumbent positioning reduces reflux and aspiration of gastric contents, lowering the risk of ventilator-associated pneumonia. Other measures include daily sedation interruption, oral care and avoiding unnecessary circuit changes. Deep sedation and supine positioning both increase risk.

Question 16Infection prevention and control

A needlestick injury occurs with a hollow-bore needle from a patient with unknown blood-borne virus status. What is the first priority immediately after the injury?

  1. Report to occupational health the next working day
  2. Wash the wound with soap and water and report immediately for post-exposure assessment Correct answer.
  3. Apply a tight tourniquet above the injury site
  4. Squeeze the wound firmly to express blood

Explanation

Immediate care is to wash the wound thoroughly with soap and running water and then seek prompt post-exposure assessment, because timely prophylaxis can prevent transmission of some blood-borne viruses. Squeezing, scrubbing or applying caustic agents can increase tissue damage and is discouraged. Reporting is urgent rather than deferred.

Question 17Infection prevention and control

Which practice best reduces the risk of sharps injuries in a clinical area?

  1. Recapping needles using two hands
  2. Carrying used needles to a sharps bin at the far end of the ward
  3. Using safety-engineered devices and immediate disposal in puncture-resistant containers Correct answer.
  4. Placing used needles temporarily on the trolley

Explanation

Safety-engineered devices and immediate disposal at the point of use in puncture-resistant, appropriately filled containers are the most effective measures. Recapping and leaving sharps on trolleys create avoidable injury opportunities. Containers should be sealed when three-quarters full and never overfilled.

Question 18Infection prevention and control

Which statement about environmental cleaning in a healthcare setting is correct?

  1. Surfaces should be cleaned only when visibly soiled
  2. Shared patient equipment requires no cleaning between patients
  3. Cleaning and disinfection should be targeted to high-touch surfaces and performed with adequate contact time Correct answer.
  4. Fogging with disinfectant replaces routine cleaning

Explanation

Pathogens persist on high-touch surfaces such as bed rails, call bells and door handles, so these require regular cleaning and disinfection with the correct contact time. Visible soiling is not a prerequisite for cleaning because many contaminants are invisible. Shared equipment must be decontaminated between patients.

Question 19Infection prevention and control

What is the correct approach to managing a spill of blood on a hard floor?

  1. Wipe it up with a dry cloth and place the cloth in general waste
  2. Leave it to dry and clean at the end of the shift
  3. Contain the spill, apply absorbent material, disinfect with an appropriate agent and dispose of waste as clinical waste Correct answer.
  4. Rinse it into the floor drain with water

Explanation

Blood spills carry blood-borne virus risk and must be contained and decontaminated using an appropriate disinfectant at the correct concentration and contact time. Materials used are disposed of as clinical waste. Rinsing into drains or leaving the spill spreads contamination.

Question 20Infection prevention and control

Which statement about the use of antibiotics and antimicrobial stewardship is correct?

  1. Empirical therapy should be reviewed and narrowed once culture results are available Correct answer.
  2. Antibiotic courses should always be completed for at least 14 days
  3. Prophylactic antibiotics are harmless and can be given freely
  4. Broad-spectrum antibiotics should be used for every suspected infection

Explanation

Antimicrobial stewardship requires review of empirical therapy once culture and sensitivity results are available, with de-escalation to narrower agents when possible. This reduces selection pressure for resistant organisms and limits adverse effects. Prolonged courses and indiscriminate prophylaxis both drive resistance.

Question 21Infection prevention and control

A patient with a multi-drug resistant organism is admitted to the ward. Which practice is most appropriate?

  1. Cohorting with other patients who have the same organism where possible Correct answer.
  2. Using the same blood pressure cuff for all patients without decontamination
  3. Placing the patient in an open bay next to a postoperative patient
  4. Sharing a commode with other patients without cleaning

Explanation

Cohorting patients colonised or infected with the same multi-drug resistant organism in a designated area limits cross-transmission when single rooms are unavailable. Dedicated equipment and enhanced environmental cleaning further reduce spread. Placing such patients next to vulnerable patients increases risk.

Question 22Infection prevention and control

Which statement about vaccination of healthcare workers is correct?

  1. Vaccination of healthcare workers contributes to protecting vulnerable patients through herd effects Correct answer.
  2. Healthcare workers cannot transmit vaccine-preventable diseases
  3. Vaccination protects only the individual worker
  4. Immunisation status has no relevance to infection control policy

Explanation

Immunising healthcare workers protects them and reduces the likelihood of transmitting vaccine-preventable infections to susceptible patients. Some vaccines also reduce asymptomatic carriage and onward transmission. Occupational health programmes therefore promote and record immunisation status.

Question 23Infection prevention and control

Which statement about the correct use of a surgical mask during a sterile procedure is correct?

  1. The mask may be worn around the neck between procedures
  2. The mask should cover the nose and mouth and be changed when damp or soiled Correct answer.
  3. A cloth mask is acceptable in theatre
  4. The mask should be removed to speak clearly to the patient

Explanation

A surgical mask must cover both the nose and mouth to filter droplets emitted by the wearer and protect the sterile field. Masks should be changed when damp, soiled or per policy, and removed by the ties without touching the front. Wearing a mask below the nose or around the neck defeats its purpose.

Question 24Infection prevention and control

Which statement about the reprocessing of reusable bedpans and urinals between patients is correct?

  1. They should be cleaned and disinfected with a validated process or be single-use Correct answer.
  2. They require sterilisation in an autoclave between every patient
  3. Rinsing with cold water is sufficient
  4. They can be shared if the patient has no symptoms of infection

Explanation

Bedpans and urinals are noncritical items that contact intact skin and mucous membranes indirectly, so they require cleaning and disinfection using a validated process such as a washer-disinfector, or should be single-use. Rinsing alone does not remove or kill organisms. Symptom status does not determine the need for decontamination.

Question 25Infection prevention and control

A ward is experiencing an outbreak of a respiratory virus. Which combination of measures is most appropriate?

  1. Droplet precautions, cohorting, enhanced hand hygiene and restriction of ill visitors Correct answer.
  2. Airborne precautions with negative pressure rooms for all patients
  3. Cancelling all cleaning activities to reduce staff movement
  4. Standard precautions only

Explanation

Respiratory virus outbreaks are controlled with transmission-based precautions appropriate to the route, cohorting of cases, enhanced hand hygiene, environmental cleaning and restricting visitors who are unwell. Standard precautions alone are insufficient during an outbreak. Cancelling cleaning would worsen contamination.

Question 26Infection prevention and control

According to standard precautions, how should healthcare workers treat blood and body fluids from every patient?

  1. As potentially infectious regardless of the patient's known diagnosis Correct answer.
  2. As safe when the patient has no fever or visible skin lesions
  3. As infectious only during invasive procedures
  4. As infectious only when the patient has a confirmed blood-borne virus

Explanation

Standard precautions require that all blood, body fluids, secretions, non-intact skin and mucous membranes be treated as potentially infectious for every patient, because infection status is often unknown and carriers may be asymptomatic. Precautions are therefore applied universally rather than being triggered by a known diagnosis or by visible signs of illness.

Question 27Infection prevention and control

A healthcare worker's hands are visibly soiled with blood. What is the correct first step in hand hygiene?

  1. Wash with soap and water before any alcohol-based product Correct answer.
  2. Apply alcohol-based hand rub and rub until dry
  3. Use alcohol-based hand rub twice in succession
  4. Wipe hands with a paper towel, then use alcohol-based hand rub

Explanation

When hands are visibly soiled or contaminated with blood or body fluids, they must be washed with soap and water, because alcohol-based hand rub does not remove organic material effectively. Soap and water physically remove soil and many organisms, after which hand hygiene can continue as indicated.

Question 28Infection prevention and control

A patient is admitted with suspected pulmonary tuberculosis. Which set of precautions is most appropriate in addition to standard precautions?

  1. Airborne precautions with a fit-tested respirator and a negative-pressure room Correct answer.
  2. Standard precautions alone, since tuberculosis is not transmissible in hospital
  3. Droplet precautions with a surgical mask within one metre
  4. Contact precautions with a gown and gloves for all contact

Explanation

Tuberculosis is transmitted by airborne droplet nuclei that remain suspended and travel on air currents, so airborne precautions are required. This means a negative-pressure room with the door closed and a fit-tested particulate respirator for staff entering, alongside standard precautions.

Question 29Infection prevention and control

A nurse must perform hand hygiene before touching a patient's intravenous access site. Which moment of hand hygiene does this represent?

  1. After body fluid exposure risk
  2. Before touching the patient only
  3. After touching the patient's surroundings
  4. Before clean or aseptic procedure Correct answer.

Explanation

Hand hygiene immediately before a clean or aseptic task protects the patient from organisms introduced during the procedure, including access of invasive devices. This moment is distinct from routine hand hygiene before touching the patient or after contact with surroundings.

Question 30Infection prevention and control

A patient is colonised with a carbapenem-resistant Enterobacterales and has an indwelling urinary catheter. Which single measure most directly limits environmental and cross-transmission of this organism on the ward?

  1. Increasing the frequency of bed linen changes to twice daily
  2. Switching all staff to alcohol-based hand rub only for the shift
  3. Routine daily urine cultures for all patients on the ward
  4. Cohorting the patient with dedicated equipment and consistent contact precautions Correct answer.

Explanation

For multidrug-resistant Gram-negative colonisation, the dominant spread is via contaminated hands, equipment and shared items, so placing the patient in a single room or cohort with dedicated equipment and consistent contact precautions interrupts transmission. Surveillance cultures and linen changes support general control but do not directly break the contact route.

Question 31Restorative dentistry

Which tooth surface classification describes a cavity preparation involving the occlusal surface and one proximal surface of a posterior tooth?

  1. Class V
  2. Class I
  3. Class II Correct answer.
  4. Class III

Explanation

Class II preparations involve proximal surfaces of posterior teeth, and when the occlusal surface is also involved the preparation is termed a Class II compound or complex preparation. The classification system sorts preparations by the surfaces affected.

Question 32Restorative dentistry

What is the primary function of the bevel placed on the enamel margin of a conventional Class III composite preparation?

  1. To lengthen the enamel rods for retention
  2. To increase the bulk of restorative material at the margin
  3. To reduce the need for a matrix band
  4. To expose enamel rods for improved acid-etch bonding Correct answer.

Explanation

A bevel increases the surface area of enamel available for etching and orients the exposed rod ends so that resin tags can infiltrate them, improving the marginal seal. The beveled margin also blends the restoration-tooth interface more esthetically.

Question 33Restorative dentistry

Which instrument is most appropriate for removing carious dentin from the floor of a deep preparation while preserving the pulp?

  1. A slow-speed round bur
  2. A gingival margin trimmer
  3. A diamond fissure bur in a high-speed handpiece
  4. A spoon excavator Correct answer.

Explanation

A spoon excavator allows controlled hand removal of softened, infected dentin, particularly near the pulp where tactile feedback is important. It helps avoid unnecessary removal of affected but re-mineralizable dentin.

Question 34Restorative dentistry

Which base material is contraindicated directly beneath a metallic restoration in a deep cavity because of its low compressive strength and high solubility?

  1. Zinc phosphate cement
  2. Resin-modified glass ionomer
  3. Calcium hydroxide liner Correct answer.
  4. Glass ionomer cement

Explanation

Calcium hydroxide is highly soluble and has low compressive strength, so it is used only as a thin protective liner over near-exposures rather than as a bulk base. A stronger base material must support the restoration above it.

Question 35Restorative dentistry

What is the principal purpose of the smear layer in dentin bonding?

  1. It blocks the action of all adhesive monomers
  2. It permanently seals the dentin tubules
  3. It prevents any resin infiltration into dentin
  4. It provides a substrate that etchants and primers modify to create micromechanical retention Correct answer.

Explanation

The smear layer is a thin layer of debris created by instrumentation; etch-and-rinse systems remove or modify it, while self-etch systems incorporate it, both producing a hybrid layer for retention. Its presence is central to how adhesives interact with dentin.

Question 36Restorative dentistry

During acid-etching of enamel, what is the recommended concentration of phosphoric acid and typical application time?

  1. 50% for 5 seconds
  2. 10% for 60 seconds
  3. 37% for 15 to 30 seconds Correct answer.
  4. 5% for 2 minutes

Explanation

Phosphoric acid at 37% applied for roughly 15 to 30 seconds produces the characteristic etched enamel pattern needed for resin tag formation. Over-etching or under-etching can compromise bond strength.

Question 37Restorative dentistry

A patient reports sharp pain when biting on a newly placed amalgam restoration. Which cause is most likely immediately after placement?

  1. Pulpal necrosis
  2. Fracture of the amalgam
  3. Marginal leakage from recurrent caries
  4. A high occlusal contact Correct answer.

Explanation

A restoration left in supraocclusion concentrates force on that tooth during function, producing sharp biting pain. Occlusal adjustment with articulating paper usually resolves the symptom.

Question 38Restorative dentistry

What is the main reason a matrix band is used when placing a Class II amalgam?

  1. To restore the proximal contour and confine the material Correct answer.
  2. To insulate the pulp from thermal changes
  3. To etch the enamel
  4. To sterilize the preparation

Explanation

A matrix band supports the restorative material, re-establishes proximal contour and contact, and prevents overhangs. It also helps contain the material during condensation.

Question 39Restorative dentistry

Which property of amalgam is primarily improved by increasing the copper content in high-copper alloys?

  1. Resistance to corrosion and marginal breakdown Correct answer.
  2. Marginal adaptation at placement
  3. Thermal conductivity
  4. Setting expansion

Explanation

High-copper amalgams reduce the formation of the weak gamma-2 phase, which improves resistance to corrosion and marginal deterioration. This contributes to better long-term clinical performance.

Question 40Restorative dentistry

What is the principal advantage of using a flowable composite in a small Class V lesion?

  1. It requires no light curing
  2. It eliminates the need for a bonding agent
  3. It has the highest wear resistance of all composites
  4. It adapts readily to cavity walls with low viscosity Correct answer.

Explanation

Flowable composites have lower viscosity and better wettability, which helps them adapt to irregular cavity walls and margins. Their lower filler content means they are used in low-stress areas rather than for heavy occlusal loading.

Question 41Restorative dentistry

Which factor most strongly determines the depth of cure of a light-activated composite?

  1. The brand of articulating paper
  2. The shade of the composite Correct answer.
  3. The patient's age
  4. The type of matrix band used

Explanation

Darker and more opaque shades attenuate light more strongly, reducing the depth of cure, while lighter shades transmit more light. Clinicians therefore limit increment thickness especially with darker shades.

Question 42Restorative dentistry

What is the primary rationale for placing a gingival seat in a Class II amalgam preparation?

  1. To provide a flat surface that resists displacement of the amalgam and protects the gingival margin Correct answer.
  2. To increase the retention of the enamel walls
  3. To allow the use of a smaller matrix band
  4. To improve the esthetics of the restoration

Explanation

A flat gingival seat provides a buttress of dentin that supports the amalgam and resists forces directed cervically. It also creates a defined margin that can be properly condensed against.

Question 43Restorative dentistry

Which instrument is used to condense amalgam into a preparation?

  1. A chisel
  2. A burnisher
  3. A carver
  4. A condenser Correct answer.

Explanation

A condenser is designed with a small working end to compact amalgam incrementally into the cavity, eliminating voids and ensuring adaptation. Carvers and burnishers are used later for contouring and smoothing.

Question 44Restorative dentistry

What is the purpose of the self-etching primer in a self-etch adhesive system?

  1. To simultaneously etch and prime dentin without a rinsing step Correct answer.
  2. To act as a bulk restorative material
  3. To remove the smear layer completely with a separate rinse
  4. To replace the need for light curing

Explanation

Self-etch primers contain acidic monomers that demineralize and infiltrate the smear layer and underlying dentin in one step, so no separate etch-and-rinse is needed. This simplifies the procedure and reduces technique sensitivity.

Question 45Restorative dentistry

Which of the following best describes the term 'hybrid layer' in dentin bonding?

  1. A layer of amalgam bonded to enamel
  2. A band of sclerotic dentin formed by caries
  3. A zone of resin-infiltrated demineralized dentin Correct answer.
  4. A layer of pure unfilled resin on the surface

Explanation

The hybrid layer forms when resin monomers penetrate demineralized dentin and polymerize among the collagen fibrils, creating micromechanical retention. Its quality strongly influences bond durability.

Question 46Restorative dentistry

A Class IV composite restoration on a maxillary central incisor requires replacement because of marginal staining and chipping. Which approach best addresses the failure?

  1. Polish the margin and leave the defect
  2. Convert the tooth to a full crown immediately
  3. Remove the restoration, re-prepare margins, and re-bond with a bevel Correct answer.
  4. Roughen the surface and add new composite over the stain

Explanation

Marginal staining and chipping usually indicate a compromised seal or unsupported enamel, so the restoration should be removed and the margins re-prepared with a bevel before re-bonding. Simply layering new material over a failing margin does not correct the underlying problem.

Question 47Restorative dentistry

Which type of glass ionomer cement releases fluoride and bonds chemically to tooth structure, making it useful for pediatric restorations?

  1. Polycarboxylate cement
  2. Conventional glass ionomer Correct answer.
  3. Zinc oxide eugenol
  4. Zinc phosphate

Explanation

Conventional glass ionomer cements bond chemically to enamel and dentin and release fluoride over time, which is advantageous in caries-prone patients. Their lower strength limits them to selected situations.

Question 48Restorative dentistry

What does the term 'pulpal protection' refer to in restorative dentistry?

  1. Placing liners or bases to insulate and protect the pulp from thermal, chemical, and bacterial insults Correct answer.
  2. Reducing the size of the restoration
  3. Using a matrix band during condensation
  4. Removing the smear layer only

Explanation

Pulpal protection involves placing appropriate liners or bases to shield the pulp from thermal changes, chemical irritation from restorative materials, and bacterial leakage. The choice of material depends on remaining dentin thickness.

Question 49Restorative dentistry

Which statement about the coefficient of thermal expansion is most relevant when choosing a restorative material?

  1. It only matters for anterior restorations
  2. A high value always improves marginal seal
  3. It has no effect on microleakage
  4. A material closely matching tooth structure reduces stress at the margin Correct answer.

Explanation

When the coefficient of thermal expansion of a restorative material differs greatly from that of tooth structure, temperature changes create stresses at the interface and can contribute to microleakage. Materials with values closer to enamel and dentin tend to perform better in this regard.

Question 50Restorative dentistry

Which bur is typically used to establish the initial outline form in enamel for a Class I preparation?

  1. A rubber cup
  2. A diamond wheel
  3. A round bur
  4. A fissure bur Correct answer.

Explanation

A fissure bur is designed for cutting straight walls and establishing the outline form with defined cavosurface margins. Round burs are used for extension and caries removal.