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CLASSIFICATION OF MALOCCLUSIONOctober 26,

2009

Our lecture today about classification of malocclusion. . .

Malocclusion:

Definition: feature of dental aligment or occlusion at variance from the ideal.

When we say malocclusion, it’s any variance from ideal in term of dental aligment or

occlusion, so the anomaly or variation could be dental variation or skeletal variation.

Dental variation: the problem is within the teeth itself.

Skeletal variation: the problem is within the jaw either upper or lower or both.

Now let's start with the dental variation.

We can classify it into: intra-arch, inter-arch.

When we say intra-arch it's mean within the same jaw, so it's either intra upper arch or intralower arch.

Intra-arch variation: these variations are:

1. Anomalies in tooth position.

2. Impaction.

3. Crowding.

4. Spacing.5. Mid line diastema.

(There are some pictures in the slide that we don’t have a soft copy, so please refer to it

while reading the lecture)

1. Anomalies in tooth position:

Look at the canine (slide # 5), it located buccally and high in the labial sulcus.

2. Impaction:

As you notice, upper left canine still impacted, still inside the bone (slides # 6 and 7).

3. Crowding:

It's the shortage of space, which means that the space available is not enough for the

teeth (slide # 8).4. Spacing:

It's the opposite of crowding. Too much space (slide # 9).

5. Mid line diastema:

It's the space between upper central incisors.

Inter-arch variation:

the problem should be in the teeth when they are in occlusion, so between the upper and

the lower arche.

We can classify into:

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1. Incisal inter-arch variations:

• Anterior-Posterior.

• Vertical.

• Transverse.

2. Posterior (buccal) inter-arch variations:

• Anterior-Posterior.

• Vertical.

• Transverse.

So we look in the teeth in three dimensional views.

Incisal inter-arch variations

1. Anterior-Posterior relationship:- BSI (1983) classify the incisal relationship into:

Class I, Class II: Division 1 and division 2 and Class III.

- Class I incisor relationship:

When the lower incisor edges occlude on or immediately below the cingulum

plateau of the upper central incisor.

Look at the picture in slide # 14:

In this picture we see class I and everything is normal regarding the incisor, but also

we see that there is crowding so we don’t say class I but we say Class I Malocclusion.

- Class II incisor relationship:

Where the lower incisor edges bite posterior to the cingulum plateau of the upper

incisors.

Division 1: the upper central incisors are proclined or of average inclination (normal)

and there is an increase overjet. But keep in your mind that the lower incisors should be

posterior to the cingulum plateau of the upper (slide # 17)

Overjet: the horizontal distance between the labial surface of the lower incisor and the

incisor edge of the upper.

Look to the picture: upper central incisor normally inclined, but the overjet increase, and

for sure lower incisor edge bite behind the cingulum.

Division 2: the upper central incisors are retroclined, the overjet is usually minimal but

maybe increase (slide # 18).

Look to the picture (slide # 19), the lower incisor edge bite behind the cingulum of the

upper central incisor, and the upper central also retroclined.

Note: the overjet maybe decreased, normal or increased.

- Class III incisor relationship:

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Where the lower incisor edges bite anterior to the cingulum plateau of upper incisors,

the overjet is reduced or reversed (negative). Slide # 20

Look to the picture (slide # 21).

2. Vertical incisor relationship:- Increased overbite: Complete, incomplete and traumatic.

- Reduced overbite.

- Anterior open bite.

Overbite: the vertical overlap between maxillary and mandibular incisors. On average

it's the incisal third of lower incisors.

- Increased overbite:

Where the vertical overlap between maxillary and mandibular incisors exceeds theincisal third of the mandibular incisor.

Look at the picture in slide # 23 carefully. There is touch between the lower incisor

edge and the tooth (the upper incisor), or touch between the lower incisor edge and the

soft tissue (the palate), so we can say complete tooth or complete soft tissue. The teeth

on the right side of the picture called Increased and Incomplete, and there is no touch

between the upper and lower teeth.

Look at the picture in slide # 24, we can see that the upper incisors cover the lower

incisors.

- Reduced overbite:

Less than one third coverage of the lower incisors. Or to be more specific, less than

the incisal third of lower incisor. Slide # 25, the middle case in the picture.

Look to the picture in slide 26, we have edge to edge vertical overlap = 0. but still

not open because there is touch between upper and lower incisors.

- Sharaf asked the doc a question I couldn’t hear, and the answer was:

We do anlysis anterior-posterior dimension, vertical and transverse, and always any

classification of malocclusion start from anterior-posterior classification, so we said

Class III malocclusion complicated by reduce overbite. Overbite is not a classification

(increased or decreased) although we can say it’s a reduced overbite case, but we have

to say Class III malocclusion.

- Open bite:

No vertical overlap (no touch).

Look to the right case in the picture in slide 27 and the picture in slide 28 (AOB:

Anterior open bite).

Again we still in incisal inter-arch variations.

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3. Transverse:

Centre line discrepancy: non coincidence of central lines of the maxillary and

mandiblar arches.

- Centre line: the line passing between the upper central incisor, passing throughthe contact point between the upper central incisor and the same goes for the lower

arch as it passes between the lower central incisors through contact point.

Look to slide 29,

- The right picture: the upper and lower central lines coincide with each other on

the same level and this is the ideal case.- The left picture: the two lines aren’t coincide with each other so we can't know

with one is wrong. So we called it shift to the right of the maxillary or mandibular

central lines, or shift to the left upper or lower mandibular central lines.But how to know which line is correct?

We look at the middle of the face, the dental line should coincide with the mid-facial

axis.

Posterior Inter-arch variation

1) Anterior-posterior relationship

- Angle's classification (1907):

- Class I molar relationship.

- Class II molar relationship.- Class III molar relationship.

- Canine relationship

- Class I molar relationship:

Where the mesiobuccal cusp of maxillary first permanent molar occludes in the buccal

groove of the mandibular first molar.

- Class II molar relationship:

Where the mesiobuccal cusp of maxillary first permanent molar occludes anterior to the

buccal groove of the mandibular first molar.

One molar = two premolars (each one called a unit, the first unit starts from the buccal

groove till the mesial side, and the second unit starts from the buccal groove to the distal

side)

We have several possibilities:

1- Full unit(refer to slide 32).2- Half unit (cusp to cusp).

3- Quarter unit (less than cusp to cusp).4- Three quarters (more than cusp to cusp).

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So the most important to know is the class II molar relationship. And how it is severe

we can say full unit, or half unit …

- Class III molar relationship:

Where the mesiobuccal cusp of maxillary first permanent molar occludes posterior tothe buccal groove of the mandibular first molar.

And it is the same as class II in that we have full unit, half unit, etc.

Anterior-posterior: canine relationships

- Class I canine relationship.- Class II canine relationship.- Class III canine relationship.

- Class I canine relationship:

When the upper canine occludes in the embrasure between lower canine and the first

premolar.

- Class II canine relationship

When the upper canine occludes anterior to the embrasure between lower canine and the

first premolar.

- Class III canine relationship

When the upper canine occludes posterior to the embrasure between lower canine and the

first premolar.

2) Vertical buccal segment relationship

- Lateral open bite (refer to slide 38): no vertical overlap between maxillary and

mandibular posterior teeth- Deep lateral bite: when the vertical overlap large, this is a rare case, which

happens when the upper jaw larger than the lower jaw.

3)Transverse buccal segment relationship

- Buccal crossbite.

- Lingual crossbite.

In normal state the buccal cusps of maxillary posterior teeth occlude buccally to the

mandibular teeth.

Buccal crossbite: where the buccal cusps of mandibular teeth occlude buccally to buccal

cusps of maxillary teeth. The term may apply to one or more teeth and can be unilateral or bilateral(refer to slide 41).

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Note: When one tooth is involved the main cause is crowding (often canine or premolar).

When more teeth are involved this indicates problem in the jaw.

Note (imp): crossbite is related to the lower teeth, therefore when we say buccal crossbite

this mean that lower posterior teeth are buccal to the upper posterior teeth, and when wesay lingual crossbite this mean that lower posterior teeth are lingual to the upper posterior

teeth.

Lingual crossbite: where the buccal cusps of mandibular teeth occlude lingually to the

palatal cusps of maxillary teeth. The term may apply to one or more teeth and can be

unilateral or bilateral (refer to slide 43).

Skeletal variation (Huston 1992)

Skeletal relationship: the relationship between maxillary jaw and mandibular jaw.

Class I skeletal relationship (ANB 2 - 4 ) ̊ ̊

Class II skeletal relationship (ANB > 4 ) ̊Class III skeletal relationship (ANB < 2 ) ̊

I can do clinical assessment for the patient and know if this class I or II ,or III skeletal

relationship but its not accurate, to be more accurate we need to take lateral cephalometric

radiograph and we look to ANB where A stands for A point, N stands for Nasion, B stands

for B point, if the angle within the normal limit 2 - 4 it is a class I, >4 class II, and <2 ̊ ̊ class III.

A: The deepest point in the contour of premaxilla.

N: Nasion.

B: The deepest point in the contour of lower symphysis.

We draw a line between A and N, and between N and B, then calculate the angle. This is

from the cephalometric radiograph.

However clinically, we can determine if the patient class I, II, or III, we put the index finger

on the A point and the middle finger on B point, for example class II mean A point anterior

to B point or B point posterior to A point.

Now refer to slide 46:

The left picture: class II skeletal -maxilla is prominent

-mandible is retruded

-or combination6

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The mid picture: class I skeletal: the maxilla and the mandible almost at the same level but

the angle is 2 - 4 due to presence of B point ̊ ̊

The right picture: class III skeletal -maxilla is retruded

-mandible is prominent-or combination

That’s all, thank you

Written by:

Khalel Abu Ismael

Designed by:

Abdullah Khazali

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