The IOTN is the Index of Orthodontic Treatment Need. It’s a very important aspect of orthodontics and proves the main method used to objectively determine whether a patient actually needs orthodontic treatment. It must be noted that the IOTN looks at the NEED for treatment, but doesn’t consider how complex the treatment will prove to be.

The IOTN is divided into two components:

  • Dental Health Component (DHC)
  • Aesthetic Component (AC)

IOTN – Dental Health Component (DHC)

The Dental Health Component is used to determine the nature and severity of a patient’s malocclusion. It is a graded system from 1-5 (5 being the most severe) and the aim is to identify the worst aspect of the patient’s malocclusion. It is also a hierarchical scale which gives priority to some problems over others. The acronym used for this is:

  • Missing
  • Overjet
  • Crossbites
  • Displacements
  • Overbite

The below image shows the different choice in each of these areas:

IOTN - Dental Health Component
IOTN – Dental Health Component

Generally, the following rules apply:

  • Grade 1 – virtually perfect
  • Grade 2 – minor irregularities including a slight overjet or open bite
  • Grade 3 – greater irregularities including a greater overjet, open bites, deep bites and bigger displacements
  • Grade 4 – severe irregularities including a large overjet, large reverse overjets affecting speech and large displacements
  • Grade 5 – extreme irregularities which need treatment including impacted teeth* (such as ectopic canines) and severe hypodontia

*The IOTN 5i is a very useful grade to know as it involves impacted teeth, excluding third molars, and is very commonly used.

It is the DHC which primarily decides if a patient needs treatment. An IOTN of 4 or 5 permits an individual to have treatment under the NHS. Usually, with a score of 4, the AC is also considered.

IOTN – Aesthetic Component (AC)

The Aesthetic Component is useful in a number of ways. It is made up of 10 colour photographs, which go from 1 (best appearance) to 10 (‘worst’ appearance). It is essentially looking at a patient’s level of ‘dental attractiveness’.

IOTN - Aesthetic Component
IOTN – Aesthetic Component

The clinician attempts to match the patient to one of the images based on their malocclusions. Obviously, this may prove to be quite subjective. However, the AC can also be used to show patients that their malocclusion may not be as bad as they believe.

When there are borderline cases based on the DHC (Grade 3), then the AC is considered. If the AC is 6 or more, then generally the patient will receive treatment.


  • The IOTN is the Index of Orthodontic Treatment Need and is used to assess a patient’s NEED for treatment
  • It is composed of a Dental Health Component (DHC) and an Aesthetic Component (AC)
  • The DHC assesses the patient’s worst feature in their malocclusion
  • The AC assesses the patient’s level of ‘dental attractiveness’
  • A DHC of 4 or 5 indicates treatment, and 3 (along with an AC of 6 or more) also indicates treatment

References and Recommended Reading


How useful was this post?

Click on a star to rate it!

Average rating 4.9 / 5. Vote count: 14

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?

📰 Subscribe Now! 📰

Sign up to the dentalnotebook newsletter to be kept up-to-date with the latest posts and valuable content!
Previous articleRemovable Partial Dentures: Kennedy Classification
Next articleReview: Dentistry ProConsult
BDS (Hons.) MFDS RCPS (Glasg.) Cert Med Ed FHEA - Currently working as a Speciality Doctor in OMFS and as an Associate Dentist



Please enter your comment!
Please enter your name here