# RDA exam practice questions: Sterilization and disinfection Five original RDA exam practice questions on sterilization and disinfection, each answered on this page with a rationale and a source. Last updated: 2026-07-25. ## Question 1 A pouch comes out of the autoclave with a fully color-changed external indicator. What does that prove? - A. That the instruments inside that pouch are sterile and usable. - B. That the cycle killed the resistant bacterial spores present. - C. That the weekly biological indicator may be skipped for that load. - D. That the package was exposed to the process conditions. **Answer D:** That the package was exposed to the process conditions. A chemical indicator shows that the package was exposed to the process conditions; only a biological indicator demonstrates that highly resistant spores were killed. **Common trap:** a passing chemical indicator never clears a positive spore test and never substitutes for the weekly biological verification. Source: [16 CCR §1005 — Minimum Standards for Infection Control: standard precautions for all patients; written protocol and conspicuously posted regulation;…](https://govt.westlaw.com/calregs/) ## Question 2 Two pouches are found in the storage drawer: one is dry and intact but sterilized last month, and one is from yesterday but slightly damp. What is correct? - A. Both are unusable, because both are past their safe storage window. - B. The dry, intact pouch may be used; the damp one must be reprocessed. - C. Both may be used, because neither pouch is torn or opened. - D. The damp pouch may be used and the older dry one reprocessed, since sterility is time-related. **Answer B:** The dry, intact pouch may be used; the damp one must be reprocessed. Sterility is event-related, not time-related: a dry, intact, sealed package remains sterile, while a wet, torn, or dropped package is contaminated and must be cleaned, repackaged, and re-sterilized. **Common trap:** treating a date as an expiration — and treating a recent date as protection against moisture — inverts the rule in both directions. Source: [16 CCR §1005 — Minimum Standards for Infection Control: standard precautions for all patients; written protocol and conspicuously posted regulation;…](https://govt.westlaw.com/calregs/) ## Question 3 An RDA finishes a restorative appointment. She removes the light-handle barrier while still gloved, discards it, sprays the countertop once with a Cal-EPA registered hospital-grade disinfectant, wipes it dry immediately, places a fresh barrier, and seats the next patient. Which step failed to meet 16 CCR §1005? - A. Removing the barrier while still gloved — barriers must be removed only after gloves are off and hands are washed. - B. Wiping the disinfectant dry immediately — the surface must be cleaned first, then left wet for the label's full contact time. - C. Placing a new barrier on the countertop — a countertop is a housekeeping surface and may only be cleaned, never covered. - D. Using a Cal-EPA registered hospital-grade disinfectant — a clinical contact surface requires a high-level disinfectant. **Answer B:** Wiping the disinfectant dry immediately — the surface must be cleaned first, then left wet for the label's full contact time. The regulation defines cleaning as removing visible soil and debris with water plus a detergent or enzymatic product, and states that "Cleaning must precede any disinfection or sterilization process." That is the entire basis of the spray-wipe-spray (or wipe-discard-wipe) routine: the first pass cleans, the second pass leaves disinfectant sitting on a clean surface for the label's contact time, because "All germicides must be used in accordance with intended use and label instructions." Removing the barrier with gloved hands was correct, and a Cal-EPA registered hospital-grade low- to intermediate-level product is the correct strength for a routine clinical contact surface. **Common trap:** Option A inverts the correct order — barriers come off while still gloved, then gloves come off, then hand hygiene. Option C confuses categories: a countertop inside the treatment zone is a clinical contact surface, and floors, walls, and sinks are the housekeeping surfaces. Option D over-escalates; high-level disinfection is for heat-sensitive semi-critical and critical items, never a routine surface requirement. Source: [16 CCR §1005 — Minimum Standards for Infection Control (Dental Board of California): cleaning before disinfection or sterilization, surface…](https://govt.westlaw.com/calregs/) ## Question 4 An office is setting up an operatory before the first patient. The chair switches and the air/water syringe tubing are seamed and cannot be properly cleaned and disinfected. What does 16 CCR §1005 require for these items? - A. Clean and disinfect them with an intermediate-level disinfectant at the end of each workday. - B. Protect them with disposable impervious barriers, changed between patients and when visibly soiled. - C. Cover them with plain paper towels, which are replaced whenever they look soiled and again at day's end. - D. Leave them uncovered; items built so that they cannot be cleaned are exempt from barriers between patients. **Answer B:** Protect them with disposable impervious barriers, changed between patients and when visibly soiled. The regulation makes barriers the required answer for one specific category: non-critical items or surfaces that are likely to be contaminated and are built in a way that prevents proper cleaning and disinfection "shall be protected with disposable impervious barriers." The change rule is absolute — "Disposable barriers shall be changed when visibly soiled or damaged and between patients." Impervious means fluid cannot soak through, so plastic sleeves, plastic-backed paper, and plastic wrap qualify. **Common trap:** Option C is the quiet failure — plain paper is not impervious, so fluid reaches the surface underneath. Option A downgrades a between-patient requirement to an end-of-day one. Option D invents an exemption that does not exist: every clinical contact surface has exactly two lawful states between patients, covered or cleaned-and-disinfected. Source: [16 CCR §1005 — Minimum Standards for Infection Control (Dental Board of California): cleaning before disinfection or sterilization, surface…](https://govt.westlaw.com/calregs/) ## Question 5 A candidate studying from an older prep booklet tells you the rule is "flush the lines twenty seconds when you open in the morning, then two minutes between patients." A supervising dentist asks you to state the actual California requirement. What is correct? - A. Purge or flush for at least 2 minutes at the start of each workday before devices are attached; flush 20 seconds between patients. - B. Flush for 20 seconds at the start of each workday after attaching handpieces, scalers, and tips; flush a full 2 minutes between patients. - C. Flush for a full 2 minutes at the start of each workday after attaching handpieces, scalers, and tips; flush for 2 minutes between patients. - D. Flush for 30 seconds at the start of each workday before attaching handpieces, scalers, and tips; flush 30 seconds again between patients. **Answer A:** Purge or flush for at least 2 minutes at the start of each workday before devices are attached; flush 20 seconds between patients. 16 CCR §1005 requires that at the beginning of each workday the lines and devices be "purged with air, or flushed with water for at least two (2) minutes prior to attaching handpieces, scalers, air water syringe tips, and other devices," and that "The dental unit lines and devices shall be flushed between each patient for a minimum of twenty (20) seconds." The sequence is written into the sentence: the purge or flush happens before devices are attached, not after. The same section separately requires that dental unit waterlines be anti-retractive so fluid is not pulled back up the line. **Common trap:** This is a classic stale-prep item — reversing the two numbers is the single most common error on this topic, and option B does exactly that. Option C keeps the right morning number but attaches devices first, which defeats the purpose of purging the line. Option D substitutes a plausible-sounding round number that appears nowhere in the regulation. Source: [16 CCR §1005 — Minimum Standards for Infection Control (Dental Board of California): cleaning before disinfection or sterilization, surface…](https://govt.westlaw.com/calregs/) ## Next step [Take the free 15-question practice test](https://dentovio.com/rda/free-practice-test) Official reference: [Dental Board of California RDA Combined Written and Law and Ethics Examination Outline](https://www.dbc.ca.gov/formspubs/rda_exam_outline.pdf). Original exam-style questions written for study, never recalled exam content. Independent educational preparation, not legal or clinical advice, and not affiliated with or endorsed by the Dental Board of California or PSI. Confirm current requirements with the Dental Board of California.