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CDA practice questions

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Question 1General Chairside Assisting (GC)

What is the minimum recommended duration for routine handwashing with soap and water in the dental office?

  1. 45 seconds
  2. 2 minutes
  3. 20 seconds Correct answer.
  4. 10 seconds

Explanation

Routine handwashing should last at least 20 seconds so that all surfaces of the hands and wrists are covered and microorganisms are mechanically removed. Shorter times are inadequate, and longer times offer no additional benefit for routine care.

Question 2General Chairside Assisting (GC)

Which item protects the eyes during a procedure that may produce spatter?

  1. Protective eyewear with side shields Correct answer.
  2. A surgical mask
  3. Examination gloves
  4. A reusable cloth gown

Explanation

Eyewear with side shields blocks spatter and aerosols from reaching the eyes, which are a mucosal portal of entry. Masks, gloves, and gowns protect other areas and do not seal around the eyes.

Question 3General Chairside Assisting (GC)

What is the primary function of the high-volume evacuator during a dental procedure?

  1. Retract the patient's tongue
  2. Deliver water to the operative site
  3. Polish the surface of a restoration
  4. Remove fluids and debris from the mouth Correct answer.

Explanation

The high-volume evacuator removes saliva, blood, water, and debris from the mouth, keeping the field clear and reducing aerosol. The saliva ejector handles only small amounts of fluid, and retraction and polishing are performed with other instruments.

Question 4General Chairside Assisting (GC)

In the universal numbering system, which tooth number identifies the maxillary right third molar?

  1. 1 Correct answer.
  2. 32
  3. 17
  4. 16

Explanation

Universal numbering begins with the maxillary right third molar as tooth 1 and proceeds around the arch to the maxillary left third molar as 16, then continues through the mandibular arch to 32. Tooth 17 is the mandibular left third molar, and 32 is the mandibular right third molar.

Question 5General Chairside Assisting (GC)

When the operator's stool height is properly adjusted, the operator's thighs should be positioned:

  1. Parallel to the floor Correct answer.
  2. Angled downward about 30 degrees
  3. Raised above hip level
  4. Resting against the armrest

Explanation

Correct stool height allows the thighs to be roughly parallel to the floor with the feet flat, which supports neutral posture and reduces fatigue. Angling the thighs or raising them above hip level increases strain on the back and legs.

Question 6General Chairside Assisting (GC)

Alginate impression material sets as a result of:

  1. Cooling of the mixed material
  2. Evaporation of water from the mix as it sets
  3. A chemical reaction between powder and water Correct answer.
  4. Exposure to the curing light

Explanation

Alginate is an irreversible hydrocolloid that sets by a chemical gelation reaction between the alginate salts and calcium ions when powder is mixed with water. It does not set by drying, cooling, or light activation.

Question 7General Chairside Assisting (GC)

What is the normal resting heart rate range for a healthy adult?

  1. 60 to 100 beats per minute Correct answer.
  2. 40 to 60 beats per minute
  3. 30 to 50 beats per minute
  4. 100 to 140 beats per minute

Explanation

A normal adult resting heart rate is approximately 60 to 100 beats per minute. Rates below 60 indicate bradycardia and rates above 100 indicate tachycardia, both of which warrant attention before treatment.

Question 8General Chairside Assisting (GC)

Between patients, the surfaces of the dental unit are best cleaned and disinfected with:

  1. An alcohol-free mouthrinse
  2. Sterile saline
  3. Soap and water only
  4. An EPA-registered hospital disinfectant Correct answer.

Explanation

Clinical contact surfaces are cleaned and then treated with an EPA-registered hospital disinfectant that carries the appropriate tuberculocidal or emerging-pathogen claim. Saline, mouthrinse, and plain soap do not meet the requirement for surface disinfection.

Question 9General Chairside Assisting (GC)

Biologic monitoring of each steam sterilizer should be performed at least:

  1. Quarterly
  2. Monthly
  3. Weekly Correct answer.
  4. Annually

Explanation

Spore testing verifies that the sterilizer is actually killing resistant microorganisms, and it is recommended at least weekly for each sterilizer. Less frequent monitoring allows a malfunction to go undetected across many cycles.

Question 10General Chairside Assisting (GC)

An item that contacts intact mucous membranes but does not penetrate tissue is classified as:

  1. Sterile
  2. Semicritical Correct answer.
  3. Critical
  4. Noncritical

Explanation

Semicritical items contact mucous membranes or nonintact skin and require at least high-level disinfection. Critical items penetrate tissue or bone, and noncritical items contact only intact skin.

Question 11General Chairside Assisting (GC)

During a pen-grasp instrument transfer, the assistant holds the instrument by the:

  1. Working end, leaving the handle free Correct answer.
  2. Handle, at the end farthest from the working tip
  3. Middle of the shank between the handle and tip
  4. Hinge, with the tips pointing toward the assistant

Explanation

The assistant grasps the instrument near the working end so the operator can take the handle directly without repositioning the hand. This keeps the transfer smooth and reduces the risk of a dropped or misdirected instrument.

Question 12General Chairside Assisting (GC)

The main purpose of the dental dam during endodontic treatment is to:

  1. Improve the flow of irrigant out of the canal
  2. Reduce the need for suction
  3. Isolate the tooth and protect the airway Correct answer.
  4. Allow the patient to breathe through the mouth

Explanation

The dental dam isolates the operating field from oral fluids and shields the patient from swallowed or aspirated instruments and irrigating solutions. It also maintains a clean, dry field, but airway protection is the key safety benefit.

Question 13General Chairside Assisting (GC)

A composite restoration is light-cured with the tip held about 6 mm from the tooth surface. The most likely result is:

  1. Faster setting with greater hardness
  2. Incomplete polymerization of the resin Correct answer.
  3. No change in the restoration's properties
  4. An increase in the depth of cure

Explanation

Curing effectiveness drops sharply as the distance between the light tip and the restoration increases, because light intensity decreases. Holding the tip several millimeters away can leave the resin undercured and weaken the restoration.

Question 14General Chairside Assisting (GC)

After an injection, the safest way to handle the used needle is to:

  1. Recap using a one-handed scoop technique Correct answer.
  2. Place it uncovered in the regular trash
  3. Recap it with two hands
  4. Bend the needle before placing it in the sharps container

Explanation

Needles should never be recapped with two hands; if recapping is necessary, a one-handed scoop technique or a recapping device is used to keep fingers away from the tip. The needle is then discarded into a puncture-resistant sharps container without bending or breaking.

Question 15General Chairside Assisting (GC)

Which dental cement bonds chemically to tooth structure and releases fluoride over time?

  1. Zinc phosphate
  2. Self-curing acrylic resin
  3. Zinc oxide eugenol
  4. Glass ionomer Correct answer.

Explanation

Glass ionomer cement forms a chemical bond to enamel and dentin and releases fluoride, which makes it useful for luting and as a base or liner. Zinc phosphate and zinc oxide eugenol do not bond chemically in the same way, and acrylic resin does not release fluoride.

Question 16General Chairside Assisting (GC)

A patient becomes pale and diaphoretic and reports feeling faint during a procedure. The assistant should first:

  1. Administer oxygen and call 911
  2. Lay the patient back with the legs raised Correct answer.
  3. Place the patient in a semi-upright position
  4. Give the patient a sugar-containing drink

Explanation

These signs suggest vasovagal syncope, which is managed by placing the patient supine with the legs elevated to restore cerebral blood flow. Emergency services are called if the patient does not recover promptly or has no pulse.

Question 17General Chairside Assisting (GC)

In the bisecting angle technique, the central ray is directed:

  1. At a 45-degree angle to the occlusal plane
  2. Parallel to the long axis of the tooth being radiographed
  3. Perpendicular to the bisector of the tooth-film angle Correct answer.
  4. Perpendicular to the film surface

Explanation

The bisecting technique imagines a plane bisecting the angle formed by the tooth's long axis and the film; the central ray is aimed perpendicular to that bisector. This projects the tooth at its true length on the image.

Question 18General Chairside Assisting (GC)

The periodontal probe is used primarily to measure:

  1. The width of the attached gingiva only
  2. The thickness of enamel
  3. The depth of the gingival sulcus or pocket Correct answer.
  4. The mobility of the tooth

Explanation

The periodontal probe is marked in millimeters and is placed gently into the sulcus to measure the distance from the gingival margin to the base of the pocket. Mobility is graded by moving the tooth with instrument handles, and enamel thickness is not assessed with a probe.

Question 19General Chairside Assisting (GC)

When polishing teeth with a rubber cup and prophy paste, the assistant should use:

  1. Heavy pressure at high speed
  2. A single application held in one spot
  3. Light pressure with the cup kept moving Correct answer.
  4. Dry paste with firm strokes

Explanation

Light, intermittent pressure with the cup kept in motion prevents frictional heat and removal of excessive tooth structure. Heavy pressure or holding the cup in one place can gouge enamel or cementum and generate heat.

Question 20General Chairside Assisting (GC)

After application of fluoride varnish, the patient should be instructed to:

  1. Rinse the mouth with water right away
  2. Brush the teeth within 30 minutes
  3. Eat crunchy foods to remove the varnish
  4. Delay brushing and hard foods for 4 to 6 hours Correct answer.

Explanation

Varnish is left undisturbed on the teeth so that fluoride uptake can continue, so brushing and hard or hot foods are postponed for at least 4 to 6 hours. Rinsing or brushing immediately would remove the coating before it has had its effect.

Question 21General Chairside Assisting (GC)

Which sterilization method is appropriate for a heat-sensitive item such as a flexible endoscope?

  1. Ethylene oxide gas Correct answer.
  2. Steam autoclave at 121 degrees C
  3. Dry heat oven at 160 degrees C
  4. Glass bead sterilizer

Explanation

Ethylene oxide sterilizes at low temperature and is compatible with heat-sensitive instruments and devices. Steam, dry heat, and glass bead methods rely on high heat that would damage such items.

Question 22General Chairside Assisting (GC)

A steam sterilizer's biologic spore test comes back positive. The correct immediate action is:

  1. Continue use and repeat the test the next day
  2. Take the sterilizer out of service and reprocess loads Correct answer.
  3. Discard the test and run a chemical indicator instead
  4. Increase the cycle time and continue using the sterilizer

Explanation

A positive spore test means the cycle did not achieve sterilization, so the unit is removed from service until the cause is corrected and repeat testing is negative. Loads processed since the last valid test must be recalled and reprocessed.

Question 23General Chairside Assisting (GC)

Sterilized instruments stored in closed cabinets are considered sterile:

  1. For exactly 30 days
  2. Until the package is opened
  3. As long as the package stays intact and dry Correct answer.
  4. For one year from the date of processing

Explanation

Sterility is event-related rather than time-related, so packaged instruments remain sterile indefinitely provided the packaging remains dry and intact. A torn, wet, or compromised package must be reprocessed regardless of the date.

Question 24General Chairside Assisting (GC)

A biologic indicator containing Geobacillus stearothermophilus spores is used to monitor:

  1. Glutaraldehyde solutions
  2. Steam and chemical vapor sterilizers Correct answer.
  3. Ethylene oxide sterilizers
  4. Dry heat sterilizers

Explanation

Geobacillus stearothermophilus is a heat-resistant spore used for steam and chemical vapor sterilizers, which operate with moist heat. Dry heat and ethylene oxide are monitored with Bacillus atrophaeus spores.

Question 25General Chairside Assisting (GC)

After an accidental needlestick from a contaminated needle, the assistant's first action should be to:

  1. Squeeze the wound firmly and apply bleach
  2. Wait for the patient's HIV test results before reporting
  3. Wash with soap and water and report immediately Correct answer.
  4. Continue the procedure and report at the end of the day

Explanation

The exposed site is washed promptly with soap and water and the exposure is reported right away so that source evaluation and post-exposure prophylaxis can be started within the recommended window. Bleach and squeezing the wound are not recommended, and reporting must never be delayed.

Question 26General Chairside Assisting (GC)

In the universal tooth numbering system, which tooth is designated as number 8?

  1. Maxillary left central incisor
  2. Maxillary right central incisor Correct answer.
  3. Mandibular right central incisor
  4. Maxillary right lateral incisor

Explanation

Universal numbering starts with the maxillary right third molar as number 1 and continues across the maxillary arch to the left third molar as number 16. Number 8 is therefore the maxillary right central incisor.

Question 27General Chairside Assisting (GC)

The primary function of the high-volume evacuator during a restorative procedure is to:

  1. Remove fluids and debris from the oral cavity Correct answer.
  2. Illuminate the operating field
  3. Dry the enamel surface before bonding
  4. Retract the tongue and cheek away from the field

Explanation

The high-volume evacuator removes large volumes of saliva, water, blood, and debris during treatment. It helps keep the field clear and reduces the patient's risk of aspirating or swallowing material.

Question 28General Chairside Assisting (GC)

Why is a water spray used with a high-speed handpiece during tooth preparation?

  1. To soften the enamel for easier cutting
  2. To improve visibility by washing away enamel dust
  3. To disinfect the bur during cutting
  4. To cool the tooth and prevent pulpal damage Correct answer.

Explanation

Friction from a high-speed bur generates heat that can injure the dental pulp. The water spray cools the tooth and bur and helps clear debris from the preparation.

Question 29General Chairside Assisting (GC)

A dental dam punch is used to:

  1. Clamp the dental dam to the anchor tooth
  2. Cut the dental dam after treatment
  3. Stretch the dental dam over the frame
  4. Create holes in the dental dam for the teeth Correct answer.

Explanation

The dental dam punch creates precisely sized holes in the rubber dam so it can be placed over the teeth. The clamp, frame, and scissors serve the other functions.

Question 30General Chairside Assisting (GC)

For most maxillary restorative procedures, the patient's chair is positioned so that the patient is:

  1. Upright with the chin tucked toward the chest
  2. Reclined so the maxillary arch is nearly perpendicular to the floor Correct answer.
  3. Flat with the head lower than the heart
  4. Turned sharply toward the operator

Explanation

Maxillary treatment is usually easier when the patient is reclined enough that the maxillary arch is nearly vertical to the floor. This gives the operator direct access and good visibility.

Question 31General Chairside Assisting (GC)

A blood pressure cuff is placed around the patient's arm so that the center of the bladder lies over the:

  1. Radial artery
  2. Brachial artery Correct answer.
  3. Carotid artery
  4. Ulnar artery

Explanation

The cuff bladder must be centered over the brachial artery on the inner upper arm. This position allows accurate detection of arterial sounds or oscillations.

Question 32General Chairside Assisting (GC)

According to standard precautions, which item of personal protective equipment should be removed first after patient care?

  1. Mask
  2. Face shield
  3. Gloves Correct answer.
  4. Gown

Explanation

Gloves are removed first because they are the most contaminated item and would contaminate other PPE if touched later. Hand hygiene follows glove removal, and the mask is removed last.

Question 33General Chairside Assisting (GC)

After a tooth extraction, the patient should be instructed to bite firmly on the gauze sponge for approximately:

  1. 1 to 2 hours
  2. 30 to 45 minutes Correct answer.
  3. 5 minutes
  4. 10 minutes

Explanation

Firm pressure on the gauze for about 30 to 45 minutes allows a stable blood clot to form. Prolonged biting beyond that is unnecessary and may disturb the clot.

Question 34General Chairside Assisting (GC)

A wedge is placed during placement of a Class II matrix band primarily to:

  1. Protect the pulp from the restorative material
  2. Mark the contact point for later adjustment
  3. Adapt the band at the gingival margin and slightly separate the teeth Correct answer.
  4. Hold the matrix band securely to the adjacent tooth

Explanation

The wedge presses the matrix band against the gingival margin of the preparation and slightly separates the teeth. This helps create a tight contact and prevents restorative material from extruding into the gingival sulcus.

Question 35General Chairside Assisting (GC)

When enamel is etched with phosphoric acid gel before bonding, the enamel surface becomes:

  1. Harder and more resistant to resin
  2. Microporous and frosty in appearance Correct answer.
  3. Impermeable to bonding resin
  4. Smooth and glossy

Explanation

Acid etching removes a small amount of enamel and creates microscopic porosities. The frosty appearance confirms that the enamel is ready for bonding resin.

Question 36General Chairside Assisting (GC)

After acid etching a tooth for sealant placement, the assistant should:

  1. Apply fluoride varnish and light-cure it
  2. Rinse and thoroughly dry the tooth Correct answer.
  3. Wipe the tooth with alcohol
  4. Apply the sealant immediately without rinsing

Explanation

The etchant must be rinsed away completely and the enamel dried until it appears frosty. Sealant is then applied to the etched, isolated surface.

Question 37General Chairside Assisting (GC)

Before an injection, topical anesthetic is most effective when it is:

  1. Injected into the tissue with a separate syringe
  2. Applied to wet mucosa just as the needle is inserted
  3. Placed on the tongue for systemic absorption
  4. Applied to dried mucosa and left in place for 1 to 2 minutes Correct answer.

Explanation

Topical anesthetic should be placed on dried mucosa and allowed time to penetrate the surface. One to two minutes is typically needed for adequate numbness before injection.

Question 38General Chairside Assisting (GC)

When positioning a digital intraoral sensor for a periapical radiograph, the assistant should:

  1. Ask the patient to bite directly on the sensor cable
  2. Place the sensor at a 45-degree angle to the tooth
  3. Hold the sensor steady with a fingertip inside the mouth
  4. Use a sensor holder or bite block to stabilize and align it Correct answer.

Explanation

A sensor holder or bite block stabilizes the sensor and helps align it with the tooth and beam. This reduces retakes and protects the sensor.

Question 39General Chairside Assisting (GC)

Increasing the water-to-powder ratio when mixing dental plaster will:

  1. Have no effect on strength or setting time
  2. Increase strength and increase setting time
  3. Decrease strength and increase setting time Correct answer.
  4. Increase strength and decrease setting time

Explanation

Adding more water than recommended dilutes the gypsum mixture, which lowers the final strength and lengthens the setting time. Manufacturers' water-to-powder ratios should be followed for predictable results.

Question 40General Chairside Assisting (GC)

Before a high-speed handpiece is sterilized, it should be:

  1. Wrapped while still wet with water
  2. Soaked in glutaraldehyde for 10 hours
  3. Placed in the ultrasonic cleaner for 30 minutes
  4. Cleaned, lubricated, and run briefly Correct answer.

Explanation

Handpieces require cleaning and lubrication according to the manufacturer's instructions before sterilization. Running the handpiece briefly helps distribute lubricant and flush debris.

Question 41General Chairside Assisting (GC)

The ultrasonic cleaning solution should be:

  1. Changed daily or when visibly contaminated Correct answer.
  2. Changed once a month
  3. Changed once a week
  4. Changed only when it becomes cloudy

Explanation

Ultrasonic cleaning solution becomes contaminated with debris and microorganisms during use. It should be changed at least daily and sooner if visibly soiled.

Question 42General Chairside Assisting (GC)

Pouches placed in a steam sterilizer should be:

  1. Sealed with extra tape to stay closed
  2. Arranged loosely without overcrowding Correct answer.
  3. Tightly packed to maximize the load
  4. Stacked in one dense pile

Explanation

Steam must circulate freely around each pouch for effective sterilization. Overcrowding or dense stacking prevents penetration and impairs drying.

Question 43General Chairside Assisting (GC)

Gingival retraction cord is placed before an impression to:

  1. Polish the prepared tooth margin
  2. Temporarily displace gingival tissue away from the margin Correct answer.
  3. Permanently widen the gingival sulcus
  4. Stop bleeding permanently

Explanation

Retraction cord temporarily moves the gingival tissues away from the preparation margin. This allows impression material to capture the margin accurately.

Question 44General Chairside Assisting (GC)

Nonabsorbable sutures in the oral cavity are typically removed after approximately:

  1. 3 days
  2. 14 days
  3. 24 hours
  4. 7 days Correct answer.

Explanation

Nonabsorbable oral sutures are generally removed in about 5 to 7 days, when initial healing has occurred. Removal earlier may cause wound separation, while removal much later can lead to tissue irritation.

Question 45General Chairside Assisting (GC)

During administration of a local anesthetic, the dentist aspirates to:

  1. Test the depth of anesthesia
  2. Increase the speed of the injection
  3. Detect intravascular placement of the needle Correct answer.
  4. Confirm that the cartridge is full

Explanation

Aspiration checks whether the needle tip has entered a blood vessel. A positive aspiration indicates that the solution should not be deposited at that site.

Question 46General Chairside Assisting (GC)

The initial caries lesion in enamel is caused primarily by:

  1. Direct acid from foods dissolving enamel
  2. Abrasion from toothbrushing
  3. Excess fluoride uptake in enamel
  4. Acids produced by cariogenic bacteria Correct answer.

Explanation

Cariogenic bacteria ferment carbohydrates and produce acids that demineralize enamel. The resulting subsurface porosity is the beginning of the caries lesion.

Question 47General Chairside Assisting (GC)

When applying an AED to an adult in cardiac arrest, the second pad is placed:

  1. On the lower right abdomen
  2. On the upper left chest below the clavicle
  3. In the center of the sternum
  4. On the lower left chest lateral to the nipple Correct answer.

Explanation

The standard adult AED placement is one pad on the upper right chest and the other on the lower left chest lateral to the nipple. This orientation directs current across the heart.

Question 48General Chairside Assisting (GC)

Which characteristic of dentin makes bonding more difficult than bonding to enamel?

  1. Dentin lacks dentinal tubules
  2. Dentin contains more water and organic material Correct answer.
  3. Dentin has a higher mineral content than enamel
  4. Dentin is dry and impermeable

Explanation

Dentin is wet and contains more organic material and water than enamel. This moisture and the presence of dentinal tubules complicate adhesive bonding and require specialized bonding systems.

Question 49General Chairside Assisting (GC)

Epinephrine is included in many local anesthetic cartridges to:

  1. Cause vasoconstriction, prolong anesthesia, and reduce bleeding Correct answer.
  2. Buffer the pH of the anesthetic solution
  3. Increase heart rate to speed the onset of anesthesia
  4. Prevent allergic reactions to the anesthetic

Explanation

Epinephrine constricts blood vessels, which slows absorption of the anesthetic and prolongs its effect. This vasoconstriction also helps control bleeding at the treatment site.

Question 50General Chairside Assisting (GC)

A Class II malocclusion is present when the mandibular first molar is positioned:

  1. Distal to the maxillary first molar Correct answer.
  2. Mesial to the maxillary first molar
  3. Directly aligned with the maxillary first molar
  4. Lingual to the maxillary first molar

Explanation

In Angle's Class II malocclusion, the mandibular first molar is distal to its normal relationship with the maxillary first molar. This creates a retruded mandibular position relative to the maxilla.