A dental hygienist's letters come in three kinds: the state license (RDH — or LDH, which Indiana law also recognizes), academic degrees (AS, BS, BSDH, MSDH), and state designations and add-on permits (California's RDHAP and RDHEF, public health hygienist statuses, local anesthesia certificates).
The license behind the letters is issued state by state — every state requires dental hygienists to be licensed, and the designations and permits beyond it change which jobs and settings you're eligible for.
Licensed vs. registered vs. certified: what each word actually means
The one credential every U.S. hygienist must hold is a state license: every state requires dental hygienists to be licensed, and in most states that means a degree from an accredited program, passing written and clinical exams, and continuing education to keep it.
"Registered" isn't a tier above "licensed" — both words describe the same legal authority to practice, and which letters you may use is set by your state's law.
The letters really do vary.
Michigan's rules let a registered dental hygienist who holds a degree or certificate from a CODA-approved program and has met all licensure requirements use "R.D.H." after their name.
Indiana law names "Licensed Dental Hygienist," "Dental Hygienist," and the letters L.D.H., R.D.H. and D.H. as hygiene titles — it recognizes LDH as well as RDH, so an Indiana hygienist can sign as either.
For the acronym itself, see what RDH means; the dental hygienist career guide covers the profession as a whole.
"Certified" is the loosest word of the three.
Certifications come from certifying bodies, not state boards — BLS's hygiene profile, for example, notes that many hygienist jobs also require CPR certification.
State-created statuses can borrow the word, though: New Hampshire's certified public health dental hygienist is a designation a hygienist qualifies for on top of the license.
When someone says "certified dental hygienist," in practice they mean the licensed one.
Degree letters: what AS, BS, BSDH and MSDH tell an employer
Degree abbreviations describe education, not permission.
BLS lists an associate degree as the typical entry-level education for dental hygienists, so the associate letters (AS, or AAS) mark the entry program; BS and BSDH mark a bachelor's, and MSDH a master's.
The license is what lets you work; the degree is what you earned on the way in.
The higher letters open specific doors.
BLS says a bachelor's or master's degree is usually required for research, teaching, or clinical practice in public or school health programs, and master's programs in dental hygiene are relatively uncommon.
Two state credentials also read your degree: one route to New Hampshire's certified public health dental hygienist status requires a bachelor's degree in dental hygiene with at least 6 semester hours in community dental health, and California's RDHAP requires a bachelor's degree or the equivalent.
Whether the bachelor's is worth the extra time and tuition depends on where you want to work — see associate vs bachelor's in dental hygiene for the full comparison of cost, length and outcomes.
State designations: RDHAP, RDHEF, LDH and the public health titles
Above the base license, states create their own designations, and the alphabet changes at the border.
California's practice act recognizes three hygiene license categories — RDH, RDHAP and RDHEF (registered dental hygienist in extended functions) — and says only those hygienists or a licensed dentist may practice dental hygiene on patients, with narrow listed exceptions.
RDHAP is the one people ask about.
It's California's alternative-practice credential, and qualifying takes all of the following: a passing score on a California law and ethics exam and, on the main route, a current California RDH license plus at least 2,000 hours of hygiene practice in the preceding 36 months and a bachelor's degree or equivalent with at least 150 hours of additional board-prescribed education — every item, not any one of them.
RDH vs. RDHAP compares the two credentials in full.
Other states name their expansions differently.
Maine law defines hygiene-based titles of its own — "independent practice dental hygienist" and "dental therapist" (plus a provisional therapist title) — each a person who holds a Maine dental hygienist license with additional authorization.
Massachusetts recognizes a public health dental hygienist who, with at least 3 years of full-time clinical experience in a public health setting, may provide services without a dentist's supervision in settings such as hospitals, schools and community clinics under a written collaborative agreement (M.G.L. c.112, §51, per ADHA's chart).
New Hampshire certifies a public health dental hygienist through its own routes (RSA 317-A:21-e, per ADHA's chart).
Same word, different meanings: LDH in Indiana is simply a license title, while Massachusetts' public health designation expands where a hygienist can work and New Hampshire's is a separate certified status on top of the license.
Never assume a designation travels.
Designations stop at the state line
Add-on permits: local anesthesia, nitrous oxide and other authorizations
Permits are the add-ons that most often change what a workday includes.
ADHA's local anesthesia chart, revised December 2025, lists an implementation year for local anesthesia administration by dental hygienists in all 50 states and DC — though Delaware's 2025 course and exam requirements were still pending board regulations when the chart was revised.
The permit's terms are where states split: the chart lists direct supervision plus a 16-hour didactic and 3-hour clinical course in California, and general supervision with a WREB exam in Washington.
New York writes a stricter rule.
A New York dental hygienist may not administer or monitor nitrous oxide analgesia or give local infiltration anesthesia without a separate dental hygiene restricted local infiltration anesthesia/nitrous oxide analgesia certificate — and then only under a dentist's personal supervision.
Without that certificate, those procedures are outside a New York hygienist's scope, whatever their resume says.
Notice the pattern in every example above — California's course, Washington's exam, New York's certificate: each is a state requirement, on top of the license, not a national certification.
See the local anesthesia permit guide for how the courses, exams and supervision rules work in practice.
Which credentials raise pay or open jobs?
Be skeptical of any chart that puts a dollar figure on a credential.
Our research found no published source that breaks dental hygienist pay down by permit or degree — BLS reports occupation-wide pay figures (see the dental hygienist salary guide), and nothing here prices an RDHAP or an anesthesia certificate.
What credentials verifiably change is eligibility: which procedures you can perform, which settings you can work in, and which postings you can honestly answer.
The eligibility effects are concrete.
In New York, the restricted certificate is the line between being able to administer infiltration anesthesia and nitrous oxide and not being able to.
Massachusetts' public health hygienist status opens practice without a dentist's supervision in hospitals, schools and community clinics — but only for hygienists with at least 3 years of full-time public health clinical experience under a written collaborative agreement.
A bachelor's opens doors an associate doesn't: research, teaching, and public or school health programs usually require one, and California's RDHAP, on its main route, requires a bachelor's degree or equivalent.
So the highest-leverage credential is the one your target job needs.
Read postings in your state, note which permit or degree keeps appearing next to the roles you want, and treat that as your next step — not because it guarantees a raise, but because it takes you out of the pool of applicants who can't do the procedure.
How to list credentials after your name
Since the letters themselves are set state by state, the safe order is: license first, degree second, add-ons third — spelled out wherever the abbreviation is ambiguous.
A Michigan hygienist who has met all licensure requirements may use R.D.H.; an Indiana hygienist can use LDH or RDH, since the state recognizes both.
Degrees follow the license (BSDH, for example), and permits are clearest written out — "local anesthesia permitted" tells a hiring manager more than a state-specific abbreviation.
List only what you actually hold, and expect it to be checked.
California's DCA License Search covers the Registered Dental Hygienist license and its alternative-practice and extended-function variants, alongside assistant and sedation credentials — the categories an employer or patient can look up.
Where a permit is separate from the license, as with New York's certificate, list it separately — without it, those procedures are outside your scope.
For placement, keywords and the rest of the document, the dental hygienist resume guide covers the whole page.
This page is general career information, not legal or licensing advice. Title, designation and permit rules are state law and change over time — verify with your state dental board or hygiene board before relying on them.