بسم الله الرحمنالرحيم

Ortho lec. 4 date of lec: 23/10/08

CLASSIFICATION OF MALOCLUSION

In our teeth we can have a normal occlusion and we discussed that previously, or an abnormal occlusion which we call it “malocclusion”. If you have a case and you realized that this person has a malocclusion, it’s not enough to say that this is a malocclusion, you must classify this type of malocclusion and be more specific. Before we start to talk about the classification of malocclusion, we must know the types of abnormalities in the relationship between the upper and lower arches, and they are : 1- Teeth malposition : Which means that the problem is in the alignment of the teeth on the line of the arch only, not on the bone itself, in this case, the relationship between the upper and the lower arches is within normal limit .

2- Arch relationship abnormalities : In this case, the alignment of the teeth is normal (not necessarily in normal occlusion) and the problem is in the bone itself. Maybe the upper arch is situated more anteriorly (class II), or the lower is more anteriorly (class III). Because we have two different bones in the mouth (alveolar bone which is attached to a basal bone) we will have two type of arch relationship abnormalities, and they are :a-Dentoalveolar relationship: which mean we

have abnormal relationship between the upper and lower teeth with normal alignment but still we have malocclusion, in this case, the tilting of the teeth is abnormal.Tilting: is the lingo/palatelabial inclination of the teeth.

b-Skeletal relationship: which mean that the problem isn’t in the alveolar bone, it’s in the basal bone of the maxilla or the mandible and their relationship relative to each other.

Note : the results of treating a case

where the malocclusion is due to dentoalveolar abnormalities are better than if we have skeletal abnormalities because only the teeth inclination is abnormal, but in skeletal the basal bone isn’t in its place like the case below.

In order to describe teeth malposition or the

irregularities within the arches we usually use the word “VERSION”, and according to the abnormal position we can have: buccoversion, Lingoversion, supraversion, infraversion, distoversion, and mesioversion. All these terms used only if the tooth is in its place, but we have some terms used if the tooth has been moved away from his place like:

1-Transposition or transversion : where the tooth has changed places with another tooth.

2-Ectopic eruption : where the tooth has been erupted in unusual place.

3-Torse version (not sure) : used when the tooth is rotated .

Note : we said that sometimes we have malocclusion due to teeth malposition but with normal relationship between arches, or abnormal arch relationship with normal teeth position, but sometime we can have both together in the same person, abnormal arch relationship with teeth malposition.

In order to reach a diagnosis about the status of the occlusion, the teeth and the arches must be examine in 3 planes:

1- Antro-posterior plane: It’s the first plane to look at and we have to look to a specific teeth to determine the relation between the upper and lower jaws, so we have divisions of this plane and they are:

a-Molar relationship – angle’s classification : which has been published in 1907, and angle believed that when the upper and lower 1st molars erupts and reach occlusion they don’t move, but this fact isn’t believed now because in a case of premature loss of the E’s, these molars can move forward. Back to our discussion, angle classify the molar relationship into 3 classes: ** Class I molar relationship: which is the normal one, and it’s when the mesiobuccal cusp of the upper 1st molar occludes in the buccal groove of the lower 1st molar.

** Class II molar relationship: the case when the mesiobuccal cusp of the upper 1st molar occludes anterior to the buccal groove of the lower 1st molar, and we have two situations :1-Half-unit : it means that the mesiobuccal cusp

has passes only half the mesiobuccal cusp of the lower molar, and this is called “cusp to cusp relationship”

2-Full-unit : when the mesiobuccal cusp of the upper molar passes all the way and the full width of the mesiobuccal cusp of the lower molar and

becomes in the embrasure

between the 5 and the 6 .

Just for knowledge, unit means the width of the cusp of the upper or lower molar.

Note: saying class II molar relationship isn’t enough, we have to specify if it half unit or full unit.

** Class III molar relationship : the case when the mesiobuccal cusp of the upper 1st molar occludes posterior to the buccal groove of the lower 1st molar, and also here we have two situations:

1-Half-unit: when the mesiobuccal cusp of the upper 1st molar passes only half the distobuccal cusp of the lower 1st molar.

2-Full-unit: when the mesiobuccal cusp of the upper 1st molar passes the whole width of the distobuccal cusp of the lower 1st molar.

Note: According to Andrew’s suggestion, if we have abnormal relationship of the molars so we must have an abnormal relationship of the arches because the teeth when erupt they don’t move according to him, but this suggestion isn’t true because in a case of premature loss of the E’s, there is mesial drift of the molars, and to correct this case we only need to move back the molars distally but it’s not easy.

Due to the fact that the molars aren’t stable and they sometimes move, they choose a tooth

that will not move anywhere after eruption and they come with:

b- Incisor relationship (British system): the incisors won’t move if we had premature loss of primary incisors. We have 3 incisor relationship :** Class I incisor relationship: where the incisal edge of the lower incisors bites in the cingulum of the upper incisors, and this is the normal

occlusion .

** Class II incisor relationship : when the incisal edge of the lower incisors is biting behind the cingulum of the upper incisors. As with class II molar relationship, we have two division of this class:1-Class II division I : when the incisal edges of

the lower incisor bite behind the cingulum of the upper incisors and the upper incisors are proclined.

2-Class II division II : when the incisal edges of the lower incisors bite behind the cingulum of the upper incisors and

the upper incisors are retroclined.

Note : in class II division II we can have only the centrals retroclined, or all the incisors (centrals and laterals) are retroclined. Both we called “classII division II” .

Q1 : in which case we will see increase overjet ??

Ofcaurse in class II division I, because the upper centrals are proclined.

Q2: In which case we will see increase overbite ??

Ofcaurse in class II division II, because the upper centrals are retroclined and more labial surface of the lower incisor is hiding behind.

** Class III incisor relationship : when the incisal edges of the lower incisors bite infront of the cingulum of the upper incisors, and we have two cases :

1-The edges are infront of the cingulum but still behind the upper incisors.

2-The edges are infront of the cingulum and also the upper incisors, so we have “reverse overjet” and that known as “anterior crossbite” .

So what we are going to use? The angle’s molar classification or the British classification (incisors relationship) ??

We use the British classification either class I, class II division I, class II division II, or class III, but it doesn’t means to forget about the angle’s molar classification, we

must be aware about it and to know how to examine the molar relationship .

2-Vertical plane :

In this plane we should look to the amount of overlaping between the lower and upper incisors. Normaly the upper incisors overlap nearly the incisal 1/3 of the labial surface of the lower incisors during intercuspation, and this is called “normal bite” .

Now what are the abnormalities we could find at this plane ?

1-Openbite: it means that there is no overlap at all between the upper and lower incisors during

maximum intercuspation of the molars, so we will have a space anteriorly .

2-Reduced overbite : in this case we will find overlaping between incisors but it’s less than 1/3 of the labial surface and without spacing, so to make it easy, it’s somewhere between normal bite and openbite .

3-Deep bite : when the overlaping is more that 1/3 and almost all the surface of the lower incisors is hiding behind the upper incisors but the incisal edge of the lower isn’t touching the palate (v. imp.) .

4-Deep impinging bite : if we have a case with deep bite but the incisal edge of the lower incisor is touching the palate we will call it “deep impinging bite” .

3-Transverse plane :

In this plane we should look at the buccal surface of the upper lateral teeth (premolars and molars) in relation the buccal surface of the lower lateral teeth. Normaly we must find that the buccal surface of the upper teeth is more outside (buccaly) than the lower teeth .

In other words, the buccal cusps of the lower teeth should occlude in the fossa of the upper teeth and the palatal cusps of the upper should occlude in the fossa of the lower teeth .

What malocclusion we can find in this plane ??

We have something called “crossbite”, which means that the upper teeth aren’t more outside than the lower teeth, the lower are more buccaly and the cusps will change places, we will see that the buccal cusps of the upper teeth are in the fossa of the lower teeth and the lingual cusps of the lower teeth are in the fossa of the upper teeth.

Note : this crossbite can be either in one side and then called unilateral, or in both sides and then it’s called bilateral .

As we said before about the dentoalveolar and skeletal problems, the same thing apply here in crossbite, it could be either due to tilting of the upper teeth more palataly and that is known as “dental lateral crossbite”, or it could be due to the fact that the maxilla is narrow or constricted and then it’s called “skeletal crossbite” .

Sometimes you will face a cases opposite to crossbite, where the upper teeth moved more buccaly than their normal position, then we will see that the lingual cusps of the upper are on the buccal surface of the lower and the teeth will act like a scissor (مقص), this case is called “scissor bite” .

We mentioned previously that the results of treating a case where class II malocclusion is due to dentoalveolar

abnormalities will be better and more esthetics than if it’s due to skeletal abnormalities, because in the last one, the basal bone isn’t in its place and after treatment it won’t come back to its normal place, and in case of class II malocclusion we will have retruted chin after treatment as we saw in the pictures in the 2nd page.

Note : the same thing apply to class III malocclusion .

At the end, when we want to reach a diagnosis, we must start with the antro-posterior plane to know the classification of this malocclusion, and as we said it depends on the incisors relationship rather than molars relationship, and we must include every abnormality in the teeth (remember the version, transposition, and ectopic eruption).

As an examples :

It’s a class II division I complicated by : 1- deep impinging bite .

2- spaced upper incisors .

It’s a class II division II complicated by : deep bite .

It’s a class III complicated by : 1- buccoversion of lower canine .

2- distoversion of upper incisors .

3- impacted upper canine .

4- unilateral crossbite (left of the pt) .

It class III complicated by : 1- anterior open bite .

2- bilateral cross bite .

3- crowdening of upper and lower incisors

.

In this case, if the lower incisors bite behind the cingulum so :

It’s class II division I complicated by : 1- buccoversion of upper canine .

2- infraversion of the lower 2nd premolar .

But if the incisors bite on the cingulum then our diagnosis will be :

It’s class I complicated by : 1- buccoversion of the upper canine .

2- infraversion of the lower 2nd premolar .

Now if we can judge the skeletal relationship clinically by looking at the pt facial profile we can add it to our diagnosis for ex. We say: class II division I malocclusion in skeletal base one or two complicated by etc… but if we couldn’t, we must take a lateral cephalogram x-ray to determine the relationship then add it to the diagnosis .

This is all about the classification of malocclusion and it’s half of the orthodontics, the other half is how to treat these malocclusions after we diagnose them and that will take about a year to explain .

Forgive me if there is any mistake …. My greeting to everyone .

Done by :

Abdalla awadi …..