General Chairside Assisting practice test 2, every answer explained

Answer: D. Loss of the bone supporting the teeth in that region

A photograph shows what is on and around the crowns: deposit, staining and the colour and contour of the gum margin. What it cannot show is what has happened to the supporting bone underneath, and that is what a radiograph adds — an x-ray image of the teeth and mouth can show whether bone has been lost as a result of gum disease. Pocket depth is measured with a probe, not read off any image, and the redness and the hard deposit are both already visible in the photograph itself.

Source: Periodontal (Gum) Disease, National Institute of Dental and Craniofacial Research; section “Diagnosis”. U.S. government work, public domain.

Answer: B. Hypoglycemia

Hypoglycemia is a fall in the blood sugar, and one of the ways it happens is a long stretch with no food - which is exactly what this patient describes. Anyone can be affected, not only people with diabetes, so the picture of weakness, sweating, pallor and confusion is worth recognising in any patient who has skipped meals. Hyperventilation follows anxiety rather than fasting and leaves the patient breathing hard and tingling; an allergic reaction shows in the skin, mouth and airway soon after an exposure; and a seizure produces rigidity and violent movement rather than a slow slide into confusion.

Source: Dental Technician, Volume 2 (NAVEDTRA 14275), U.S. Navy, 1999; section “HYPOGLYCEMIA”. U.S. government work, public domain.

Answer: A. Explain what a dental dam is and what its use gains her during the visit

Isolation is one of the odder-feeling things done to a dental patient, and the minute before it goes on is when that oddness is cheapest to deal with. Placement starts with telling her what the dam is and what it gains her: a clean dry field the dentist can actually see, nothing loose to swallow, and cheek and tongue held out of the way. A patient told none of that meets a sheet of rubber across her face with no idea why it is there. Explaining afterwards is too late to be reassurance, a separate form is not what the moment calls for, and the patient who might refuse is precisely the patient the explanation exists for.

Source: Dental Instrument Setups (subcourse MD0503), U.S. Army Medical Department Center and School; section “2-15. PLACING A RUBBER DAM”. U.S. government work, public domain.

Answer: B. Putting the bracket tray out of her direct vision and asking if she is comfortable

Where the tray sits is one of the few things in the operatory the assistant controls outright. Kept out of the patient's direct line of sight it stops being a running reminder of what is coming, and nothing is being concealed from her - she has already been told what the appointment involves. The same moment is the one to ask whether she is comfortable in the chair, because a patient who is asked will say so, and a patient who is not asked usually endures it. Handing her the instruments makes the thing she dreads the center of the visit, and starting before she has settled spends the goodwill that one question buys.

Source: Dental Technician, Volume 2 (NAVEDTRA 14275), U.S. Navy, 1999; section “PREPARATION FOR ORAL PROPHYLAXIS”. U.S. government work, public domain.

Answer: C. Numbing of the isolated area, so that less anesthetic is used

The dam gives a clean, dry field of operation, improves the operator's view of the site, holds fluids, tissue and the tongue out of the way, and keeps the patient from swallowing or inhaling loose debris and small fragments. What it does nothing about is sensation: pain control comes from the local anesthetic, which is given before the sheet goes on. Reading the dam as a substitute for anesthetic is the trap in this question.

Source: Dental Technician, Volume 2 (NAVEDTRA 14275), U.S. Navy, 1999; section “RUBBER DAM INSTRUMENTS”. U.S. government work, public domain.

Answer: C. Before the tooth is prepared, against the guide the porcelain maker supplies

The colour is chosen at the start, before any tooth structure is cut. Each porcelain system comes with a number of different colours and a shade guide, and the guide is what the selection is made against. Doing it first matters because the incisor about to be prepared is part of the comparison while it is still intact, and because the choice then has to travel with the case: once the shade is selected it is recorded on the laboratory work authorisation that goes to the technician with the impression. A poured cast carries no tooth colour, a provisional is not a colour standard, and by the cementation visit the crown has already been fired in whatever shade was ordered.

Source: Dental Technician, Volume 2 (NAVEDTRA 14275), U.S. Navy, 1999; section “Shade Selection”. U.S. government work, public domain.

Answer: D. Each pattern's shape suits one arch and the teeth in one part of it

Extraction forceps are not interchangeable. The overall shape, from the working end to the handle, identifies the arch a pattern is built for - broadly S, I and Z shapes for the upper arch and C and L shapes for the lower - and within an arch the working ends are contoured to the crown and root form of one group of teeth, so the tooth on the treatment plan decides which pattern the assistant sets out. Handle shape follows that design rather than driving it, no pattern is tried on a tooth to see whether it happens to fit, and a retained root tip is teased out with an elevator instead.

Source: Dental Technician, Volume 2 (NAVEDTRA 14275), U.S. Navy, 1999; section “TOOTH EXTRACTION FORCEPS”. U.S. government work, public domain.

Answer: B. Harden a light-cured resin restoration once the dentist has placed it

Composite resin is supplied both as a self-curing two-paste system and as a light-cured one. A light-cured material stays workable in the mouth until it is set on purpose: the light source is positioned near the restoration and exposed for the time the manufacturer's instructions give. The wand neither finds decay nor bleaches enamel by itself, and drying a preparation is the air-water syringe's job.

Source: Dental Technician, Volume 2 (NAVEDTRA 14275), U.S. Navy, 1999; section “COMPOSITE RESIN RESTORATIONS”. U.S. government work, public domain.

Answer: A. Stop the revolving cup from overheating the tooth it is polishing

A cup spun fast against enamel builds heat where it touches, and heat passed into the tooth hurts the patient and can injure the pulp, so the engine is set to rotate slowly and the cup is kept well filled with paste; the same slow speed protects the soft tissue the cup runs against. The motor and the paste supply have nothing to do with it. Once the reachable surfaces are done the paste is carried between the teeth on unwaxed floss or tape, because the cup cannot get through a contact.

Source: Preventive Dentistry (subcourse MD0513), U.S. Army Medical Department Center and School; section “3-14. POLISHING”. U.S. government work, public domain.

Answer: A. Clean it, disinfect it with an EPA-registered hospital disinfectant, then rinse

CDC's dental-laboratory recommendation is to clean the case, disinfect it with an EPA-registered hospital disinfectant carrying at least a tuberculocidal claim, and rinse it before it is handled in the in-office laboratory or sent off-site. That is done as soon as possible after the impression leaves the mouth, before blood and other bioburden dry onto it, and the office tells the laboratory in writing what was used so the step is neither skipped nor needlessly repeated. Rinsing alone leaves oral microorganisms that travel onto the case and the cast poured from it, sending it untreated carries them into the laboratory, and autoclave heat would distort the impression.

Source: Guidelines for Infection Control in Dental Health-Care Settings, 2003, Centers for Disease Control and Prevention (MMWR 52, RR-17); section “I. Dental Laboratory”. U.S. government work, public domain.