Dental Assistant Requirements in Missouri: Registration, X-Ray Rules & Allowed Duties

The rule defines three related terms: a certified dental assistant, who currently holds certification from the Dental Assisting National Board; a dental assistant, who is simply an employee of a duly registered and currently licensed Missouri dentist and is neither a hygienist nor a certified dental assistant; and a dental auxiliary, an umbrella term covering either of the first two.

None of the three carries its own Missouri state registration or license.

A basic dental assistant needs no state application, exam, or fee — the rule requires only that the person be employed by a duly registered, currently licensed dentist.

Only a dental assistant, certified dental assistant, or Missouri-licensed dental hygienist who wants to perform expanded functions duties must obtain a board-issued Expanded Functions Permit, applying with a completed form, the fee set in 20 CSR 2110-2.170, and proof of meeting one of several competence paths.

The permit is issued by category: restorative I, restorative II, removable prosthodontics, fixed prosthodontics, and orthodontics.

The rule governing dental assistants sets its own five-part direct supervision standard for delegating to them: the dentist must be in the dental office, have personally diagnosed the condition, have personally authorized the procedure, remain in the office while it is performed, and evaluate the assistant's performance before the patient is dismissed.

The chapter's separate definitions rule also defines direct, indirect, and general supervision in more general terms, but the extracted text applies those broader terms to hygienists rather than to dental assistants.

Beyond routine chairside work the rule doesn't itemize, a dental assistant who holds a board-issued Expanded Functions Permit may perform the tasks listed under whichever of five categories the permit covers: Restorative I, Restorative II, Orthodontics, Prosthodontics-Fixed, and Prosthodontics-Removable.

Restorative I and II both cover sizing and cementing prefabricated crowns, placing and finishing amalgam and composite restorations, and minor palliative care, with Restorative II reaching more restoration classes.

Orthodontics and Prosthodontics-Fixed cover impressions, cementations, and adjustments for their respective appliances.

The source file's copy of the rule cuts off mid-list for Prosthodontics-Removable, and its history line shows a further amendment filed February 4, 2026 taking effect September 30, 2026 — after this page's publish date — so confirm the currently effective category list with the board.

The source file's copy of this rule picks up mid-list, at item 6 of a numbered list of functions that may never be delegated to a dental assistant.

The two items the file preserves are the scaling of teeth, and administering nitrous oxide-oxygen analgesia — except that a dental assistant or certified dental assistant may assist in the administration of and monitor nitrous oxide-oxygen analgesia with the specific training described elsewhere in the rule.

Items 1 through 5 of that list are not present in the extracted text, so this page cannot say what else it prohibits.

A dental assistant or certified dental assistant may assist in administering and monitor nitrous oxide analgesia under direct supervision, but only after completing formal certified training in a board-approved course and passing a competency test, or after being certified to do so in another state under equivalent training and testing.

The board-approved training course itself must cover a detailed list of topics, from basic pharmacology and anatomy through emergency response, documentation, and infection control — one listed topic, for example, is exposure prevention and occupational safety.

Administering nitrous oxide outside of this assist-and-monitor role remains one of the acts the rule bars a dental assistant from performing.

Every Expanded Functions Permit must be renewed every five years with a renewal application, the fee set in 20 CSR 2110-2.170, and sixteen hours of continuing education from board-approved sponsors completed in the five years before the expiration date, directly related to patient treatment, health, and safety.

A permit holder owes sixteen hours total regardless of how many permits they're renewing, and only four hours if the permit was issued twelve months or less before its expiration.

Renewal also requires current BLS certification, and an expired permit can still be renewed within one year before it becomes void.