Glossary: Medical Billing Terms for Dental Practices

A quick reference for the terminology that comes up constantly once a dental practice starts billing medical insurance. Most of this vocabulary doesn't have a dental-side equivalent, so it's worth having in one place rather than re-explaining it each time it comes up. Where a term has a full article, it's linked.

Codes & forms

Term	Plain-English meaning
CDT	Dental procedure codes (ADA). What dental insurance uses — commonly called "D-codes."
CPT	Medical procedure codes (AMA). What medical insurance uses (e.g., 64612 for a Botox injection, 99213 for an office visit).
HCPCS Level II	Medical supply and durable medical equipment (DME) codes. Examples: E0486 for a sleep appliance, J0585 for the Botox drug itself.
ICD-10-CM	Medical diagnosis codes. Required on every medical claim — this is what carries the "why" of a medical claim. Medical diagnosis goes first.
CMS-1500	The standard medical claim form. 837P is its electronic equivalent.
NDC	National Drug Code — identifies a specific drug product, dose, and package size. Required on injectable-drug lines like Botox (J0585); prefix with N4 on the claim.
POS	Place of Service — a two-digit code for where treatment occurred (e.g., 11 = office, 12 = home, used for sleep appliances).
E/M	Evaluation & Management — the CPT codes (99202–99215) used to bill office visits and exams. Level is set by total time or medical decision-making complexity.
Modifier	A two-character add-on to a CPT code that adds circumstance (which side, separate same-day service, bilateral, etc.) and often changes how the code is paid. See the Modifier Reference for the full list.
Global period	A 0-, 10-, or 90-day window following a procedure during which follow-up care is bundled into the original fee rather than billed separately.

Documentation & authorization

Term	Plain-English meaning
LMN	Letter of Medical Necessity — the cover letter that justifies why a treatment was medically necessary, often submitted alongside a claim or prior auth request.
Prior authorization (PA)	Payer approval obtained before treatment for certain services. Without it, even a medically valid claim can be denied outright. See Prior Authorization Basics.
Pre-determination	A written advance estimate of what a plan will cover for planned care, requested before treatment.
op note	Operative Note — the doctor's written record of what was done during a procedure. Must be original, signed, and specific — not templated or copy-pasted.
PWK	"Paperwork" — the general term for claim attachments like an operative note, imaging, or a sleep study.
Medical necessity	The documented clinical justification that a service was needed to treat a medical condition. The foundational concept every medical claim depends on — see Dental vs. Medical.

Payments & coverage

Term	Plain-English meaning
EOB	Explanation of Benefits — the payer's summary of what it decided on a claim and why.
ERA (835)	Electronic Remittance Advice — the electronic version of an EOB, used to post payments automatically.
Deductible	The amount a patient must pay out of pocket before their insurance starts contributing, in a given plan year. See Deductibles & Coinsurance.
Coinsurance	The percentage split between what insurance pays and what the patient pays, after the deductible is met.
Out-of-pocket maximum	The total a patient can be required to pay in a plan year before insurance covers 100% of further costs.
COB	Coordination of Benefits — the order in which multiple payers pay when more than one applies. See Coordination of Benefits.
AOB	Assignment of Benefits — an authorization allowing an insurance payment to go to the provider rather than the patient. Not always honored for out-of-network providers, even when signed.
OON	Out of Network — the provider is not contracted with the patient's plan. May require a gap exception for coverage.
Gap exception	A payer's agreement to treat an out-of-network claim as if it were in-network, usually because no comparable in-network provider is reasonably available. See Gap Exceptions.
TMJ exclusion	A plan provision that explicitly excludes coverage for TMJ-related treatment. If present, nothing on a TMJ claim will pay — including the exam. Always check for this before treating.
PIP	Personal Injury Protection — auto coverage that pays medical/dental expenses after a car accident, regardless of fault. Primary payer in auto-related trauma.
WC	Workers' Compensation — covers work-related injuries. Primary payer in work-related trauma; get the claim number before treating.

Identifiers & dates

Term	Plain-English meaning
NPI	National Provider Identifier — the number that identifies an individual provider.
TIN	Tax Identification Number — identifies the practice/billing entity.
DOS	Date of Service.

Clinical (sleep & TMJ)

These come up throughout the Procedure Playbooks.

Term	Plain-English meaning
AHI	Apnea-Hypopnea Index — a measure of sleep apnea severity (breathing interruptions per hour). Payers use it to determine coverage eligibility.
OSA	Obstructive Sleep Apnea — the condition treated when billing an oral appliance (E0486). Primary diagnosis code: G47.33.
PSG	Polysomnography — a full overnight sleep study in a lab. The gold standard for diagnosing OSA.
HST	Home Sleep Test — an at-home sleep study. Accepted by most payers for OSA diagnosis if it measures AHI and oximetry (type II/III/IV-A).
CPAP	Continuous Positive Airway Pressure — the most common OSA treatment. Patients who can't tolerate CPAP may qualify for an oral appliance.
ROM	Range of Motion — how far a joint can move. For TMJ, measured in millimeters (max opening, left/right excursion) and documented with numbers, not just "limited."
IAN	Inferior Alveolar Nerve — the main nerve through the lower jaw. Must be assessed and documented before surgical extractions near the nerve.
MRONJ	Medication-Related Osteonecrosis of the Jaw — a serious bone condition tied to certain medications (e.g., bisphosphonates). May require medical pre-clearance before extractions.