ICD-10 Codes for Orthodontics
Introduction – Kirt E. Simmons, DDS, PhD
This document is meant to provide general information on diagnostic coding, specifically coding using
the ICD-10 code set. Proper and accurate diagnostic coding is important to both provide data to third-
party payers and public entities but also to provide proper remuneration for the therapeutic procedures
(CDT or CPT codes) used to address those diagnosed conditions. The World Health Organization
(WHO) website has an online training tool (WHO website link-
http://apps.who.int/classifications/apps/icd/icd10training/) and there are multiple private vendors
offering ICD-10 coding instruction, albeit generally aimed at the larger general medical audience.
This guide is meant to provide a general overview of the ICD-10 codes and how to use them. It is NOT
an exhaustive guide and should not be considered necessarily authoritative or up to date.
How-To Guidelines - Kirt E. Simmons, DDS, PhD
• ICD-10 codes consist of a minimum of three characters and a maximum of seven, in the following
order of character: 1) Capital letter A-Z except U (not used), 2) number, 3) number, 4) number or
letter, capital or lowercase, 5) number or letter, capital or lowercase, 6) number or letter, capital or
lowercase, 7) number or letter, capital or lowercase- only used in certain specific cases.
• Please refer to the ICD-10 codes the AAO has collected (which will most commonly be used in
the provision of orthodontic services) for the following explanations of the code.
• The first character of the code is always a capital letter and denotes the general category or
conditions grouped together by the WHO. Note in the AAO list we have grouped categories
together under a larger heading (i.e. Pain, Larynx) which usually will all have the same first letter
but not necessarily (note the Pain group contains three WHO categories- G- Diseases of the
Nervous System, H- Diseases of the Eye and Adnexa and M- Diseases of the Musculoskeletal
System and Connective Tissue), since we have taken the liberty of grouping various diagnoses
together so they may be more easily located. You will notice the most commonly used diagnoses
for orthodontists will be within the categories M (Diseases of the Musculoskeletal System and
Connective Tissue) and K (Diseases of the Digestive System). There are also a large number of
Q (Congenital Malformations, Deformations, and Chromosomal Abnormalities) and S codes
(Injury, Poisoning, and Certain Other Consequences of External Causes – which actually
includes T codes too).
• To see how typical codes are displayed, see the ones under “Migraine”-- note they all begin with
“G43” which generally describes migraines, but then the next numeral, after the “.” further
describes the type of migraine- with a “0” being those without an aura. The following one or two
numerals further describe the specific type of migraine without an aura. Looking at perhaps a
more familiar set of diagnostic conditions we orthodontists are familiar with, let us take the K
codes: K00 – K14 are reserved for diseases of the oral cavity and salivary glands. So note the K00
codes all describe disorders of tooth development and eruption (except for “embedded and
