DANB study guide for the CDA, one section at a time

A patient with epilepsy has taken phenytoin for years. Which oral finding is most likely?

Pick the option you would mark on test day. The choice stays fixed, and every option then explains itself.

1. Black hairy tongue

   Hairy tongue is linked to antibiotics, smoking and poor tongue hygiene, not to long-term anticonvulsant therapy.
2. Gingival overgrowth

   Phenytoin is a classic cause of drug-induced gingival enlargement, which grows worse when plaque control is poor.
3. Tooth mobility

   Tooth mobility follows bone loss or trauma; phenytoin enlarges gum tissue rather than loosening teeth.
4. Enamel erosion

   Erosion comes from acid such as reflux, vomiting or acidic drinks, not from phenytoin.

A white patch on the floor of the mouth does not wipe off with gauze. It should be charted as a possible:

1. Thrush

   Thrush (pseudomembranous candidiasis) forms curd-like plaques that can be wiped away, leaving a red surface underneath.
2. Leukoplakia

   Leukoplakia is the clinical term for a white patch that does not rub off and cannot be identified as another condition; on the floor of the mouth it needs follow-up and often a biopsy.
3. Linea alba

   Linea alba is a thin white ridge along the bite line of the cheek, not a patch on the floor of the mouth.
4. Fordyce spot

   A Fordyce spot is a tiny yellow sebaceous gland, usually on the buccal mucosa or lips, not a single white patch.

Which sugar substitute in chewing gum has been shown to reduce Streptococcus mutans levels?

1. Aspartame

   Aspartame sweetens without feeding bacteria, but it has no shown effect on reducing Streptococcus mutans counts.
2. Xylitol

   Streptococcus mutans cannot ferment xylitol, and regular use in gum lowers the numbers of these bacteria in plaque and saliva.
3. Sorbitol

   Sorbitol is less cariogenic than sugar, but mutans streptococci can slowly ferment it, so it does not bring their levels down.
4. Sucralose

   Sucralose is not fermented, yet it only avoids feeding bacteria rather than shrinking the S. mutans population.

The pressure gauge on a nitrous oxide cylinder cannot be used to judge how much gas is left because:

1. The gauge measures only oxygen

   Each cylinder has its own gauge, and the nitrous gauge does read nitrous pressure; it simply stays steady while liquid remains.
2. N2O is stored at low pressure

   Nitrous oxide is held at roughly 750 psi, which is far from low; the reason the gauge misleads is the liquid state, not the pressure level.
3. The gauge reads flow rate

   Flow rate is read on the flowmeter of the delivery unit; the cylinder gauge reports pressure inside the tank.
4. N2O is stored as a liquid

   Nitrous oxide sits in the cylinder as a liquid under its own vapor pressure, so the gauge reads about the same until the liquid is nearly gone; weighing the cylinder shows what is left.

At the start of canal preparation on #30, which instrument does the assistant pass so the dentist can locate the canal orifices on the pulp chamber floor?

1. Barbed broach

   A barbed broach pulls pulp tissue out of a canal once it has been found; it does not locate the orifice.
2. Gutta-percha plugger

   A plugger condenses gutta-percha vertically during obturation, at the end of treatment rather than at the start.
3. Endodontic explorer

   The long, straight double-ended endodontic explorer (DG-16) is the instrument for finding canal orifices on the floor of the pulp chamber.
4. Endodontic spreader

   A spreader compacts gutta-percha laterally when the canal is filled; it is not used to locate canals.

A patient closes his lips tightly around the saliva ejector. The main concern is:

1. Swallowing the ejector tip

   The tip stays attached to the tubing, so closing the lips around it does not create a swallowing hazard.
2. Overheating the pump

   A brief seal at the tip does not overheat the vacuum pump; the concern is contaminated fluid returning to the patient.
3. Backflow into the mouth

   When the lips seal around the tip, pressure in the suction line can drop so that fluid already in the tubing flows back into the patient's mouth.
4. Clogging the separator

   Lip closure does not send extra debris to the amalgam separator; the risk is reverse flow, not a blockage.

When punching a dental dam, the largest hole is used for the:

1. Smallest premolars

   Premolars are punched with medium holes; the smallest openings are kept for mandibular incisors.
2. Central incisors

   Central incisors take one of the small holes; the larger openings are for molars and the clamped tooth.
3. Tooth being restored

   The tooth under treatment gets a hole sized to its own crown; hole size follows the tooth and the clamp, not the treatment.
4. Clamped anchor tooth

   The anchor tooth carries the clamp jaws and is usually the largest tooth isolated, so it receives the largest hole.

During condensation of a zinc-containing amalgam on #30, the alloy is contaminated with saliva. Which problem is most likely to follow?

1. Delayed expansion

   Moisture reacts with the zinc in the alloy and releases hydrogen gas, which makes the restoration expand days later and can cause pain or a raised filling.
2. Gamma-2 corrosion

   Gamma-2 corrosion is a weakness of low-copper alloys and is not what saliva contamination of a zinc alloy produces.
3. Rapid, early setting

   Contamination does not cause rapid, early setting; the damage shows up later as expansion.
4. Marginal shrinkage

   The change is the opposite of shrinkage: the alloy grows as hydrogen gas forms inside it.

The dentist needs extra working time to seat a full-arch alginate tray. Which water temperature should the assistant use for the mix?

1. Room-temperature water

   Room-temperature water gives the manufacturer's standard working time; it adds nothing extra.
2. Water near body temperature

   Water near 98 °F makes alginate set quickly, cutting the time available to seat the tray.
3. Warmer water than usual

   Warmer water speeds the set and shortens working time, the opposite of what the dentist needs.
4. Cooler water than usual

   Cooler water slows the setting reaction of alginate and lengthens working time.

When spatter is likely, OSHA's bloodborne pathogens standard requires protective eyeglasses to have:

1. Magnifying lenses

   Magnification helps the operator see detail but adds no protection unless the frames also carry solid side shields.
2. Solid side shields

   Spatter can reach the eyes from the side, so eyeglasses used as eye protection need solid side shields; goggles or a chin-length face shield are the alternatives.
3. Tinted lenses

   Tint reduces glare, not splash exposure; tinted lenses without shields still leave the sides open.
4. Vented sides

   Vented, open sides let droplets and spatter in around the lenses, defeating the purpose of eye protection.

Why is a scrub uniform not considered personal protective equipment during patient care?

1. It is not designed to block body fluids

   OSHA counts clothing as PPE only when it is intended to keep blood or other potentially infectious materials from reaching skin and clothes; ordinary scrubs are work clothes.
2. It is laundered by the employee at home

   Home laundering is allowed because scrubs are not PPE; it follows from their status rather than causing it.
3. It is not a disposable item

   Reusable gowns can count as PPE, so being washable is not what excludes a scrub uniform.
4. It is worn outside the patient-care area

   Where scrubs are worn is a separate hygiene question; they are not PPE because they offer no fluid barrier.

What is the primary purpose of flushing dental unit waterlines and handpieces at the start of the day and between patients?

1. To remove mineral scale from the lines

   Mineral scale is not cleared by a short run of water; it needs descaling products and is not the infection-control reason for the step.
2. To prevent corrosion of metal parts

   Corrosion is managed through water quality and maintenance products, not by running the lines.
3. To clear out microbes and oral debris

   Running water through the lines temporarily lowers the microbes that build up in standing water and expels patient material drawn back during treatment; it does not remove the biofilm itself.
4. To cool the water for patient comfort

   The step is not about temperature; it targets contamination in the water that reaches the patient.

Which surface in the treatment room is classified as a housekeeping surface?

1. The operatory floor

   Floors, walls and sinks are housekeeping surfaces: they are not touched by patients or gloved hands during care and are cleaned on a routine schedule.
2. The chair adjustment switch

   A chair switch touched during treatment is a clinical contact surface, not a housekeeping surface.
3. The bracket tray

   The bracket tray is handled with contaminated gloves during treatment, which makes it a clinical contact surface.
4. The dental light handle

   The light handle is adjusted with gloved hands throughout care, so it is a clinical contact surface that needs a barrier or disinfection between patients.

How should instruments be placed in an ultrasonic cleaner?

1. Stacked tightly to fit one cycle

   Stacking instruments tightly makes them shield each other, leaving debris in hinges and serrations.
2. In a basket, handles above the liquid

   Handles left out of the solution are not cleaned and carry debris back to the processing area.
3. In a basket, fully submerged, not crowded

   A basket keeps hands out of the tank, full immersion lets cavitation reach every surface, and spacing keeps instruments from shielding one another.
4. Directly on the tank floor

   Instruments resting on the tank floor dampen the energy and can be damaged; a basket or rack is used.

An aluminum foil test is used in the sterilization area to check:

1. How well the ultrasonic works

   A sheet of foil held in the running ultrasonic should come out evenly pitted; a weak or patchy pattern means the unit is not working well enough to clean.
2. Steam penetration inside packs

   Steam penetration is shown by chemical indicators inside each pack.
3. The sterilizer's door gasket

   A worn door gasket is found by inspection and by failed cycles or indicators, not by a foil test.
4. Biofilm levels in waterlines

   Waterline quality is checked with water tests such as in-office kits or laboratory plate counts, not with foil.

An unvaccinated assistant has a needlestick from an HBsAg-positive patient. The recommended prophylaxis is:

1. HBIG plus HBV vaccine series

   For an unvaccinated worker exposed to an HBsAg-positive source, PHS guidance is HBIG for immediate protection plus starting the hepatitis B vaccine series.
2. A 28-day antiretroviral course

   A 28-day antiretroviral regimen is prophylaxis against HIV; it gives no protection against hepatitis B.
3. The HBV vaccine series alone

   The vaccine series by itself builds immunity too slowly after a known positive exposure; HBIG supplies antibodies right away.
4. HBIG alone, repeated in 1 month

   Two doses of HBIG without vaccine is the plan for a known vaccine nonresponder, not for someone who was never vaccinated.

According to CDC's 2016 Summary, every dental setting should have:

1. A full-time sterilization technician

   Instrument processing can be handled by trained assistants; a full-time sterilization technician is not required.
2. A licensed microbiologist to review cases

   No microbiologist is called for; the coordinator role is filled by trained office staff.
3. A yearly OSHA inspection of the practice

   OSHA inspects in response to complaints or targeted programs, and an annual inspection is not part of CDC's recommendations.
4. A trained infection prevention coordinator

   CDC's 2016 Summary calls for at least one person trained in infection prevention to coordinate the program in every dental setting.

Before a surgical extraction, the assistant plans to use dental unit water that meets the 500 CFU/mL standard as the coolant and irrigant. What is wrong with this plan?

1. The lines need a 5-minute flush first

   No amount of line preparation turns unit water into sterile water, so a 5-minute flush does not make it suitable for surgery.
2. Sterile solution must be used instead

   For surgical procedures CDC calls for sterile saline or sterile water delivered through a sterile device; unit water is not sterile even when it meets the nonsurgical standard.
3. Nothing, as it meets the standard

   Meeting the 500 CFU/mL standard is enough only for routine nonsurgical care; surgery that exposes bone needs a sterile irrigant.
4. The water must be tested just before use

   Unit water is monitored periodically, not before each case, and a passing result would still not make it sterile.