If you’ve started reading about tongue tie, you’ve probably already run into a wall of terminology — Class 3, Type IV, Grade 2, anterior, posterior, Kotlow, Coryllos, Hazelbaker. Different clinicians use different words, sometimes interchangeably, and it can be hard to tell whether you’re being told something important or just a different way of saying the same thing.
For general education only, not medical or dental advice. Please read the full disclaimer at the end of this article.
Why classification matters (and why it isn’t the whole story)
Classification systems describe what a tongue tie looks like anatomically — how the frenulum (the small band of tissue under the tongue or behind the upper lip) is shaped and where it attaches. They were developed so that clinicians could communicate consistently with each other. They’re useful, but they don’t tell the whole story.
The reason: anatomical appearance and functional impact are two different things. A tongue tie that looks dramatic on a scoresheet can be functionally compensated, and a finding described as “mild” can produce real feeding or speech difficulty. A classification grade can inform the clinical conversation. It doesn’t make the decision.
At Inspire Dental Wellness, Dr. Erica considers classification alongside what your child can and can’t do with their tongue and lips — because function is what affects feeding, sleep, and speech.
The Coryllos Classification (Types I–IV)
The Coryllos system, developed by Dr. Elizabeth Coryllos, is the most common system used to describe tongue tie specifically. It categorizes tongue ties by where the lingual frenulum attaches to the underside of the tongue, working from the front of the tongue back toward the floor of the mouth.
- Type I — the frenulum attaches at or very near the tip of the tongue. The tip is often visibly notched or heart-shaped when the tongue lifts.
- Type II — the attachment is slightly behind the tip, generally 2 to 4 millimeters back. The tip may still look notched, though less obviously than Type I.
- Type III — the attachment is mid-tongue, generally around 4 to 8 millimeters back from the tip. The tongue may lift unevenly or rope in the middle.
- Type IV — the attachment is at the base of the tongue, often called a posterior tongue tie. It may be hidden under the mucosa (the surface tissue covering the floor of the mouth), and it’s the type most often missed on quick visual exams because there’s no obvious notch at the tip.
A common misconception is that lower numbers are “worse.” That isn’t reliably true. Type IV (posterior) ties can produce significant functional restriction even when they don’t look dramatic on visual inspection. Type I ties can sometimes be asymptomatic in a child whose feeding patterns are otherwise normal. The number describes anatomy — it doesn’t predict how a particular child or adult is going to experience it.
Clinicians who evaluate tongue tie frequently — IBCLCs, pediatric dentists with airway and frenectomy training, pediatric ENT specialists — often report that Type IV is the most commonly under-diagnosed presentation, because casual visual screening can miss it. That’s one reason functional assessment matters alongside the anatomical grade.
The Kotlow Classification (Class 1–4)
The Kotlow system, developed by Dr. Lawrence Kotlow, is most often applied to lip ties (the band connecting the upper lip to the gum tissue), though it’s sometimes referenced for tongue ties as well. It measures how far the frenulum extends down the gum line — toward, into, or past the alveolar ridge, the bony ridge that holds the upper front teeth. How these grades apply to infants specifically is covered in our guide to baby lip tie.
- Class 1 — the frenulum attaches above the gum line, with minimal effect on the mobility of the lip. Often asymptomatic.
- Class 2 — the frenulum attaches into the gum tissue (the attached gingiva) but doesn’t reach the alveolar ridge. May or may not affect feeding or oral hygiene depending on the child’s other anatomy.
- Class 3 — the frenulum extends to the front of the alveolar ridge, where the upper front teeth will emerge. May contribute to a gap between the front teeth or difficulty cleaning along the gum line.
- Class 4 — the frenulum extends past the alveolar ridge into the hard palate. The most anatomically pronounced presentation.
As with Coryllos, the number describes anatomy — not whether treatment is appropriate. A Class 4 lip tie that looks striking on a scoresheet may be functionally compensated in some children; a Class 2 can produce real feeding restriction in others. The clinical conversation considers the grade alongside how the child is using their lips: latch, seal, lift, feeding fatigue, and so on.
Kotlow’s framework is also sometimes referenced for tongue ties using equivalent numeric descriptors. When you see “Class 3 tongue tie” online, it’s usually shorthand for a Kotlow-style severity grade rather than a strictly Kotlow classification — clinicians sometimes use the terms loosely.
The Hazelbaker Assessment Tool (HATLFF)
The Hazelbaker Assessment Tool for Lingual Frenulum Function — usually shortened to HATLFF — is different from Coryllos and Kotlow in an important way: it measures function as well as appearance. It was developed by Alison Hazelbaker, an IBCLC, specifically for assessing infants whose feeding may be affected by tongue restriction.
The tool scores two categories:
- Appearance items — tongue tip shape when lifted, the attachment point of the frenulum, frenulum elasticity, length of the lingual frenulum.
- Function items — tongue lift, lateralization (side-to-side movement), extension (forward reach), spread (widening across the bottom of the mouth), cupping (forming a U-shape during sucking), peristalsis (the wave-like motion that moves milk back during a swallow), and snap-back (whether the tongue returns to a relaxed position or stays restricted).
Each item is scored individually, and the function score is weighted heavily — because function is what actually affects feeding.
This is why many lactation consultants and pediatric dentists who work with infants reach for HATLFF or a similar functional tool. An infant with a lower-grade anatomical tie but poor function scores may still benefit from clinical attention, while an infant with a higher-grade anatomical tie and good function scores may not need intervention right now.
Grades, types, classes, levels, stages — terminology decoded
Online, the same word can mean different things depending on who’s writing. Here’s how the terms tend to map up:
| Term you might see | What it usually refers to |
|---|---|
| Tongue tie type | Coryllos system (Type I–IV) |
| Tongue tie class | Kotlow system (Class 1–4) |
| Tongue tie grade | Either a Kotlow class or a general severity descriptor |
| Tongue tie level | Loose term — often used interchangeably with grade |
| Tongue tie stage | Not a formal clinical system; informal severity descriptor |
| Tongue tie severity | Combined anatomical and functional impression |
| Degrees of tongue tie | Synonym for grades; informal |
Three things to keep in mind:
- The terms are not standardized across writers. A blog or forum post may use “Class 3” and “Type 3” interchangeably even though they’re technically different systems.
- Posterior tongue tie sits in Coryllos as Type IV, but is also sometimes called a submucosal tongue tie when the restriction lies beneath the surface tissue.
- Anterior tongue tie is a catch-all for Coryllos Types I and II — restrictions visible toward the front of the tongue.
If a clinician hands you a number, it’s reasonable to ask which system they’re using.
What classification means for treatment (and what it doesn’t)
Classification systems exist to help clinicians describe anatomy consistently. They don’t, on their own, tell you whether your child needs a frenectomy.
What does matter when deciding about treatment:
- Function. Is the child feeding adequately? Is the tongue able to lift, lateralize, and seal against the palate? For older children, is speech development on track?
- Symptoms. Is there a pattern of difficulty — recurrent feeding pain, weight gain concerns, persistent gas or reflux in infants, chronic mouth breathing or disrupted sleep in older kids — that has resisted other approaches?
- Compensation. Some children with anatomical restriction compensate effectively and don’t develop symptoms. Others don’t.
- The wider picture. Airway, jaw position, palatal width, and oral muscle tone all interact. Tongue tie is one piece of a system, not a stand-alone diagnosis.
For kids over a year and adults, Dr. Erica works with a preparation-first protocol: myofunctional therapy and bodywork before release, so the tissues are prepared and the post-release rehabilitation has the best chance of producing functional change. You can read more about that on the kids frenectomy and adult frenectomy pages. For infants, the evaluation is more time-sensitive because feeding can’t wait — the infant frenectomy protocol is different, and the page walks through what to expect.
A Type IV tongue tie does not automatically mean a frenectomy is the answer. A Class 1 lip tie does not automatically mean it isn’t. The grade is a clue; the consultation is the decision. If you’ve been told by another clinician that your child has a particular grade or class of tongue tie and you’re trying to decide what to do next, a second evaluation that includes both anatomical and functional assessment can be helpful.
When classification alone can mislead
Three patterns Dr. Erica sometimes sees in consultations:
- A Type IV (posterior) tongue tie that was missed during routine newborn screening because the tip of the tongue looked normal. The restriction sits behind the visible tip and only shows up on a careful functional assessment or when the tongue is lifted with consistent pressure.
- A Class 4 lip tie that looks striking on a scoresheet but is functionally compensated. The child is feeding and growing well, the gap between the front teeth is closing on its own as the permanent dentition emerges, and the family has decided to monitor rather than treat.
- A Type I or Class 1 anatomical finding that’s described as “mild” but is producing real symptoms — a four-year-old struggling with specific speech sounds, an infant fatigue-feeding rather than transferring milk efficiently, or an adult with persistent jaw tension that tracks back to a long-standing restriction.
These aren’t unusual cases. They’re a reminder that the anatomical grade is one piece of information, and on its own, it can mislead.
Frequently asked questions
What is a Grade 4 tongue tie?
“Grade 4 tongue tie” is informal terminology that typically corresponds to either a Coryllos Type IV (posterior tongue tie, where the frenulum attaches at the base of the tongue) or a Kotlow-style severity grade indicating an anatomically pronounced restriction. The specific meaning depends on which system the clinician is referencing — it’s worth asking.
What’s the difference between a Class 3 and Class 4 tongue tie?
In the Kotlow framework, Class 3 generally describes a frenulum that attaches to the front of the alveolar ridge (the bony ridge holding the teeth), while Class 4 describes a frenulum that extends past the ridge into the hard palate. Class 4 is anatomically more pronounced, though anatomy alone does not determine whether treatment is appropriate.
Is a Type 4 tongue tie worse than Type 1?
Not necessarily. The Coryllos types describe where the frenulum attaches to the tongue (Type I at the tip, Type IV at the base), not severity of functional impact. A Type IV (posterior) tongue tie can produce significant feeding or speech restriction; a Type I can sometimes be asymptomatic. Functional assessment, not anatomy alone, helps determine whether treatment may be helpful.
Does a higher tongue tie grade mean my baby needs a frenectomy?
Not by itself. The decision to recommend a frenectomy considers symptoms, function, family priorities, and the wider clinical picture — not the anatomical grade in isolation. A consultation that combines anatomical and functional assessment is the way to know.
How is tongue tie severity measured in infants?
A combination of approaches is typical: visual inspection of the frenulum (often using Coryllos or Kotlow descriptors), and functional assessment using tools like the Hazelbaker (HATLFF), which scores how the tongue actually moves and behaves during feeding. Many lactation consultants and pediatric clinicians use functional tools because feeding is what’s affected.
Who classifies a tongue tie — pediatrician, dentist, or lactation consultant?
Any of them, depending on training and the clinical context. Pediatric dentists with airway and frenectomy training, IBCLCs (International Board Certified Lactation Consultants), pediatric ENT specialists, and some pediatricians evaluate and classify tongue tie. Clinicians who do these evaluations frequently tend to catch posterior ties that less-frequent evaluators may miss.
Schedule a consultation with Dr. Erica
If you’ve been working through this terminology because you’re trying to make a decision about your child — or you’ve been told they have a particular grade of tongue tie and you’d like a second opinion — a consultation with Dr. Erica is the next step. She’ll combine anatomical and functional assessment and walk you through what the findings mean for your specific situation. Call (708) 460-6699 or use the contact form to schedule.