The Basics


As noted here, D3G aims to develop guidelines that are both clinically useful and research friendly – and of course terminology lies at the heart of this aim. Collaborative input is sought from the practitioner community, so please let us know what you think as the nascent ideas take shape.

The Basics


Is terminology important?

If you're wondering whether terminology is of any real importance for practitioners, we say "yes!" in a word, and "more so than ever" in four. Of course we'd all love it if D3 problems went away, and past scientific wins have given good reason for further expectations in this regard (think tetracyclines and fluoride safety). Agreeing that practitioners will benefit from more science, it's a short step to appreciate that scientists will benefit reciprocally from having key terminology understood and used carefully by practitioners. Indeed, how else
will it be known we're all on the same page and stewing over the same problems? We think getting your head around our recommended terms need not be a hassle.
Indeed, realising that scientific intricacies can be a bit
overbearing at times, we've put our translational caps
on and worked hard to distill the key elements and
present them in an understandable and memorable way.

Besides intercommunication between practitioners and scientists, we also try to think "translationally" about others who will play a key role in fixing D3 problems – affected kids and families, public health professionals, and politicians too. Will one set of terms fit all these needs? We don't think so and for this reason have developed parallel vernaculars for kids and lay people, as you will see sprinkled throughout this website – a compilation appears in the glossary below. Hopefully you'll find it fun to participate in this community-focussed level of communication too.

What's the most common mix-up?

Failure to properly distinguish between "Hypomineralisation" and "Hypoplasia" appears to be a worldwide problem, for better or worse! Historically there has been little pressure on practitioners to get these terms right, to the extent that for many "hypoplasia" remains a catch-all for anything to do with missing enamel. But that situation is no longer tenable for two good reasons – the first of which is growing need for liaison between practitioners and scientists, as noted above. Secondly, and realistically of higher priority to most practitioners, the recent surge in clinical and scientific understanding of Molar Hypomin has led to a growing number of clinical imperatives. It follows that practitioners aspiring to best-care standards must respect Hypomin and Hypoplasia as clinically-distinct entities.

Distinguishing Hypomin and Hypoplasia

  1. So what are the key differences between Hypoplasia and Hypomin?

    Having realised why you need to understand the terminological differences between Hypomin and Hypoplasia, actually learning what they are is quite straightforward. Most simply, in our case Hypoplasia means a developmental deficiency in the thickness of enamel, whereas Hypomin refers to a deficit in its mineral content. The thickness deficit in Hypoplasia traces back to an early error during secretion of the developing enamel layer – and as a result, enamel Hypoplasias are always present before a tooth first enters the mouth. In contrast, the mineral deficit in Hypomin enamel happens later in development, after the enamel layer has been secreted – so Hypomin defects involve enamel of normal thickness, in unerupted teeth at least.

  2. Why then the confusion?

    HPvsHMtable-copyright-TheD3GroupWith such obvious differences between the two, how come there is so much confusion surrounding Hypomin and Hypoplasia? That too is quite simple to understand once you look at it from the clinical perspective, which mostly involves erupted teeth of course. Lacking the hardness and durability of normal enamel, Hypomin enamel is prone to degrade rapidly once exposed to the oral environment (e.g. masticatory forces, dietary acids). In severe cases, such "breakdown" may commence as soon as the tooth emerges through the gum ("eruptive breakdown") whereas in moderate cases the degradation may become obvious only after the tooth has erupted ("post-eruptive breakdown"). Because such degradation of Hypomin enamel doesn't happen before emergence, it is fundamentally incorrect to refer to it as Hypoplasia. Put another way, breakdown of Hypomin lesions represents an acquired deficit of enamel thickness, not a developmental one. Conversely, with Hypoplasia most enamel loss occurs before eruption, with any post-eruptive loss relatively minimal. Hence a key distinguishing feature of Hypomin is its relatively fast rate of change post-eruptively.

  3. Any practical significance?

    Finally, you might wonder whether this terminological distinction holds any practical significance for dental treatment? From what we understand so far, the answer appears to be a strong yes. Simply put, Hypomin starts out as a normal amount of abnormal enamel whereas Hypoplasia is the opposite – an abnormal amount of normal enamel. These clear-cut differences are likely to influence a variety of clinical decision points (e.g. etching/bonding, margins/restoratives, pain control), as noted in the following sections. So being able to discriminate between Hypoplasia and Hypomin properly can have a huge bearing on how you plan treatment of such teeth.

Understanding other basic D3 terms

Besides Hypomin and Hypoplasia, several other terms crop up regularly in the D3 world. A compilation of those terms used frequently in this website follows. We also include a colloquial adaptation of the international dental notation system, as often used in this part of the world to refer to tooth types collectively, plus a bit of practitioner slang that might also strike a chord with affected families and others.



D3s (enamel)

Developmental Dental Defects (focussing here on enamel)

Developmental defect

The primary problem happened before eruption

"Congenital", "birth defect"

Lay terms for D3, okay if qualified to individual tooth (vs. baby)


Developmental problem attributable to genetic anomaly


Developmental problem not attributable to genetic anomaly


Cause is unknown


A patch of abnormal enamel


A lesion lacking the translucence of normal enamel


A lesion with different colour from normal enamel

Missing enamel

A helpful term when uncertain about Hypomin vs. Hypoplasia etc

Enamel Hypomin (HM)

Hypomineralisation, a deficit in mineral content of enamel

Demarcated opacity

An opacity with sharply defined edges, typical of Molar Hypomin

Diffuse opacity

An opacity without sharply defined edges, typical of fluorosis

Mottled enamel

Scattered, diffuse opacities, typical of fluorosis

Shiny surface

Lesion reflects light similarly to normal enamel

Frosted surface

Lesion reflects light poorly relative to normal enamel

Pitted surface

Lesion with early degradation visible to eye

Chalky enamel

Discoloured & soft, can be cut by hand (moderate/severe Hypomin)


Degradation of Hypomin enamel, starting at surface

Eruptive breakdown

Breakdown of Hypomin enamel during emergence (severe Hypomin)

Post-eruptive breakdown

Breakdown of Hypomin enamel after eruption (moderate Hypomin)

Intact lesion

A hypomin lesion with intact surface enamel

Broken lesion

A hypomin lesion that has undergone breakdown (but not caries)

Sharp margins

Sharp irregular border, consistent with degradative fracture

Enamel Hypoplasia (HP)

A pre-eruptive (developmental) deficit in enamel thickness

Rounded margins

Rounded edge of normal enamel at border of hypoplastic lesion

Regular outline

A geometrically smooth lesion outline (e.g. groove, circular pit)

Multi-tooth Notation

Adapted from FDI World Dental Federation Notation, ISO 3950

6s, 7s & 8s

First, second & third permanent molars

1s & 2s

First & second permanent incisors

3s, 4s & 5s

Canines, first & second permanent premolars

Ds & Es

First & second primary molars (from Palmer notation)

Practitioner Slang

Ex D3G members, and with a view to better consistency!

Dodgy 6s

"Potentially bad" Molar Hypomin but not necessarily a lost cause

Manky molars

Severe Molar Hypomin, connotes "maimed" & "poor hygiene"

Bombed 6s

Severe Molar Hypomin with carious involvement (i.e. cratered)

Totally Bombed

A lost cause, warranting "expedited tooth loss"


Advanced caries in teeth unaffected by Hypomin


Glossary for the translational vernacular used on this website

Aiming to have effective translational interactions across the sector (i.e. from scientists through to the public), we are trialling a multilevel vernacular for a variety of key D3 terms as follows.





Molar Hypomin




Chalky Molars or Molar Hypomin

Chalky Molars or Molar Hypomin

Molar Hypomin or Hypomineralisation

6s with Enamel Hypomineralisation

6-year/12-year molar

(adult molars)

6-year/12-year molar
(adult molars)
First/second permanent molar  6/7
1-year/2-year molar
(baby molars)
1-year/2-year molar
(baby molars)
First/second primary molar D/E 

Wonky Tooth

Hypomin tooth

Hypomin tooth

Enamel Hypomin (6)

Wee Bit Wonky

Minor defect


Intact surface

Fairly Wonky

Moderate defect


Frosted surface

Really Wonky

Severe defect


Broken surface


Mild patch

Intact/mild lesion

Intact lesion

Chalky or Crumbly

Chalky enamel or soft Hypomin enamel

Early breakdown

Surface pitting


Hypomin hole/crater

Advanced breakdown

Broken lesion











Carious lesion

Carious lesion

(rotten) passive use only?

Decayed (rotten)

Advanced caries

Advanced caries









Plaque Bugs


Oral bacteria


Plaque Cities

Dental plaque

Plaque, biofilm

Plaque, biofilm





Dental treatment




Shiny Hat

Metal crown

Stainless steel crown

Dental crown

Wiggle out








Dental Science




Tooth Bricks

Enamel rods

Enamel rods/prisms

Enamel prisms

Tooth Mini-Bricks

Mineral crystals

Enamel crystallites

Enamel crystallites

Missing Bricks

Soft, porous