Class II division 1 malocclusions

Class II division 1 malocclusions

1. Introduction :

In 1899, Angle established his own classification of malocclusions, based on the mesiodistal relationships of the first molars.

Until this date, the proposed classifications only took into account interincisor relationships.

Ballard then established a class II skeletal classification and distinguished two divisions:

• Division 1 is characterized by a narrowed upper arch with vetibulate incisors, short lips, the lower one between the upper and lower incisors, the chin is set back.

• In division 2, the arch has a normal width; in addition, there is a palatovertion of the upper incisors.

 Class II division 1 are described in children during the mixed dentition period. Although they present a well-known clinical picture allowing almost immediate identification – receding profile, labial inocclusion, incisal overjet and molar distoclusia – they actually concern a set of dysmorphoses that are very different in terms of their anatomical variety and their etiopathogenesis.

2. Definition:

Class II division 1 malocclusions are anteroposterior anomalies characterized by exaggerated vestibuloversion of the upper incisors, exaggerated overjet, and Class II molar and canine relationships.

The shift of the arches can be isolated or associated with a shift of the bony bases.

They can be characterized by:

Too forward position of the upper teeth.

Too much anterior position of the maxilla.

Too posterior a position of the lower teeth.

A mandible that is too short or too posterior.

To these signs of the sagittal direction can of course be added signs of the vertical and transverse maxillary or dental direction to form a truly particular clinical picture.

3. Etiopathogenic diagnosis:
   1. Hereditary causes  :

These are the most frequent, observation of the family and collaterals of the patients will allow them to be highlighted.

2. Congenital causes:

They are often responsible for ATM malformations such as:

• ^First arc syndrome or FRANCESCHETTI ZWALLEN disease.
• Early congenital hypocondylia (infectious, tumoral or traumatic).
• Temporomandibular ankylosis.
• PIERRE ROBIN syndrome (glossoptosis).

Class II division 1 malocclusions

3. Skeletal causes:

On the lateral teleradiography, the architectural factors must be analyzed on four levels: the cranial level, the maxillary level, the

mandibular and, finally, the alveolodental level.

At each of these levels, variations in dimension, proportion, location and mutual angulation of the constituent elements can either promote the appearance of class II or constitute the anatomical form of the dysmorphosis of the patient examined.

4. Functional causes:

The shape and direction of the maxillary and mandibular sutures are largely dependent on muscle activities, both in function and at rest.

Distal relationship of the mandible to the maxilla or retromandibulia can result from several factors:

• Hypofunction of the propulsive muscles:

The antero-posterior position of the mandible results from the balance between the propulsor and retropulsor muscles, hypofunction of the propulsor muscles can be due to:

• Nature of insertions, direction of muscle fibers.
• Insufficient motor stimuli.
• Obstacle (overbite).

Thus the mandibular propulsion movements are hindered, resulting in a reduction in muscular tension, this tension is necessary for normal condylar growth and therefore that of the mandible. 

• The language 

It intervenes through its position, its volume, its mobility during functions and posture.

Any abnormality in morphology, position or lingual functioning can lead to unfavorable growth.

• Favorable lingual disorders of a class II 1 by retromandibulia:

• Microglossia: when the volume of the tongue is reduced, it will use the propulsors less, which will affect condylar growth due to lack of stimulation and consequently micromandibulia with retroposition.
• Glossoptosis: falling of the tongue backwards blocking the passage of air, a high and posterior position of the tongue promotes retromandibulia.
• Lingual disorders favorable to a class II 1 by promaxillia:

High position at rest with significant lingual thrust on the anterior alveolar processes, thus promoting superior proalveolism and mesioposition of the upper arch, sometimes leading to true promaxillia.

• Lips:

Labial morphology can contribute to the establishment of a class II 1 in particular the upper alveolus.

• If the upper lip is short in the presence of labial hypertonicity, the balance of the CHATEAU corridor is broken, it is shifted forward because the lingual propulsion is not thwarted by the pressure of the orbicularis oris.

           The alveolar processes remain constantly subjected to the vestibular force alone, which promotes the installation of superior proalveolism.

           The increased overjet will cause the interposition of the lower lip, the action of which is added to that of the tongue, aggravating the discrepancy (retromandibulia).

• Parafunctions – tics – vicious habits:

These are the tics of lingual, lower lip, thumb or other object sucking… the interposition of the thumb exerts eccentric pressures at the level of the maxilla and the antero-superior alveolar processes and concentric pressures at the level of the mandible and the antero-inferior alveolar processes.  

• Ventilation:

RICKETTS obstruction syndrome: The patient tilts or moves the head forward to clear the airway junction = posterior rotation of the mandible.

Giving a class II which with thumb sucking will give a proalveolus and we will find ourselves in front of the picture of a class II 1.

Class II division 1 malocclusions

5. Therapeutic causes  :

• Excessive or inappropriate use of a functional appliance that has produced posterior mandibular rotation.
• Class III intermaxillary elastics improperly worn.
• Molar or premolar extractions, justified or not, having caused posterior condylar movement.
• Premature loss of a baby tooth and mesio or distortion of the neighboring tooth.
• Condylar irradiation leading to condylar hypofunction.

4. Frequency and circumstances of occurrence:

¾ of the cases in an orthodontic population are made up of class II 1 malocclusions according to BASSIGNY.

This malocclusion is already detectable in the temporary dentition and worsens following deforming habits, after evolution of the permanent incisors. In the temporary dentition, signs of a class II antero-posterior shift: exaggerated overjet, class II canine relationships, distal gait (2nd ^temporary molars).

5. Class II 1 malocclusion and facial typology:
   1. Class II 1 long face  :

The type of mandibular growth is generally of a more or less marked posterior rotation tendency.

5-1-1- Etiology

Hereditary 

Functional:

The lingual muscle:

Direct action mechanism: volume and location of the tongue,

Indirect mechanism of action: obstruction of the upper or middle airways, which leads to mouth breathing, therefore lowering and protruding of the tongue, atypical swallowing, loose arches.

The facial muscles show lower than average tone, in connection with the long face type. The cephalic attitude also appears to favor an accentuated anteroposterior shift.

6-1-2- Facial signs:

Facial examination: the facial aesthetic impact can be quite severe, which leads to a consultation.

Examination of the face:

Long and narrow face: 

The upper floor appears to be increased. 

Lip inocclusion is common.

           The teeth are more or less visible depending on the length of the upper lip.

           Profile review:

• Skin convexity is important.
• The nose is rather average or below average in size.
• The mental symphysis is not very pronounced, giving the impression of a concealed chin (retrogeny)
• The goniac angle appears open.

Lip examination:

 The interlabial space at rest is more or less increased:

• Upper Procheilia
• Lower retrocheillie
• Exaggerated labio-mental furrow
• Short upper lip
• Gummy smile
• Incisors visible lips at rest.

Class II division 1 malocclusions

6-1-3- Occlusal signs:

Intra-arcade arrangements:

Maxilla:

• Arcade of more or less triangular shape
• Rather deep palatine vault (inconstant sign).
• Vestibuloversion of the 4 upper incisors more or less marked.

Mandible:

• Arch of usual shape with little or no incisal crowding.
• Sometimes vestibular version of the lower incisors which causes lower protrusion.

Inter-arcade relations

Ant-post meaning	Vertical direction	Transverse direction
Class II molar and canine reportsIncreased incisal overjet	Frequent anterior gaping bite related to deforming habits or parafunctions.	Normal reports or unilateral or bilateral reverse lateral occlusion (maxillary endoalveolism).

6-1-4- The muscular environment and functions:

Tongue: usual previous situation, volume sometimes increased, frequent dental support.

Lips: low labial tone and increased interlabial space. The chin tuft muscle contracts to ensure voluntary lip closure.

Masticatory muscles: predominance of depressor muscles.

Functions:

Insalivation: significant saliva flow.

Swallowing: it is atypical and very frequent, objectified by a strong anterior and lateral lingual thrust and a significant contraction of the lips and the chin tuft. The first stage of swallowing is done with the arches not tight, which can promote the extrusion of the lateral sectors.

Ventilation: This anomaly often involves mouth breathers which represent high (nasal cavities) or medium (adenoids and tonsils) obstructions of the upper airways.

Parafunctions:

Thumb sucking on other fingers or on a cloth is common. It determines anterior gapes. It is systematically associated with atypical swallowing 

6-1-5- Teleradiographic signs

Qualitative signs: 

• Signs of long face with increase in the lower level of the face.
• Mandibular shape showing signs of posterior rotation.
• Accentuated skin convexity.
• Converging horizontal planes
• Reduction of the maxillary posterior vertical height.

Quantitative signs:

• FMA increased
• Augmented lower facial floor
• Increased skeletal convexity
• Decreased facial angle.
• ANB increased
• The mandible is not reduced in antero-posterior dimension but appears too far back in profile based on mandibular rotation.

6.1.6. Dental signs:

• Vestibulo more or less accentuated version of the upper incisors.
• Normoposition or vestibulo version of the lower incisors relative to the dental plane.
• Incisal coverage rather reduced on average.

  6-2- Class II 1 short face:

The type of mandibular growth is generally of anterior rotation tendency.

6-2-1- facial signs

Facial examination:

The aesthetic impact is less marked than for class II 1 long face cases.

Face examination: 

• Short, rather wide, square face.
• The lower floor appears quite frequently diminished.

Profile examination: the convexity of the profile is increased but to a lesser extent than for class II 1 long face malocclusions due to the importance of the symphysis.

Lip examination:

• Lip ratio: labial inocclusion or labial contacts depending on the importance of the vestibular version of the incisors and the offset.
• Lip-to-tooth ratio: the teeth are more or less apparent in relation to the length of the lips and the degree of version of the upper incisors.
• Upper lip: upper proximal lip
• Lower lip: everted downwards depending on the position of the free edge of the upper incisors: marked labiomental groove or pronounced retrocheillia: appearance of a swallowed lip.

• The symphysis: volume greater than average.
• Goniac angle: obtuse.

Class II division 1 malocclusions

6.2.2. Occlusal signs, without DDM

Intra-arcade layout:

Maxillae:

• Vestibuloversion of the incisors with or without inter-incisor diastemas.
• Normal speed curve.

Mandible:

• No incisor crowding or crowding due to lingual version of the incisors (lower retroalveolism)
• Pronounced overbite of the incisor-canine sector with exaggerated curve of speech, in adult teeth.

Inter-arcade relations

Ant-post meaning	Vertical direction	Transverse direction
Class II molar and canine relationships, more or less exaggerated incisal overjet.	Incisor supraclusion: Average case: incisor contacts. Severe case: the free edges of the lower incisors are in contact with the palatine mucosa.	Normal

6.2.3. Teleradiographic signs:

Qualitative signs:

• Short face sign with diminished lower face level
• Increased maxillary posterior vertical height or not 
• Relatively parallel horizontal planes
• Mandibular shape showing signs of anterior rotation: the mandible has a square appearance with a rather short horizontal ramus and a closed goniac angle.

Quantitative signs:

Skeletal signs:

• ANB which represents the offset of the bases is more diminished than the convexity angle, due to the importance of the symphysis.
• FMA is decreased
• Lower facial level is decreased
• The facial angle when significantly decreased allows us to conclude that there is retromandibular prominence, if the facial angle is normal and the convexity increased, it is promaxillary. This measurement is only of value if the symphysis is of average importance.

Dental signs:

• Lower incisors forward or backward relative to A-Pog.
• Upper incisors: vestibuloversion 
• Incisor supraclusion assessed in relation to the RICKETTS occlusal plane.

6.2.4. Etiology:

• The functional etiology seems much less decisive for class II1 short face while the hereditary typology is more frequent for this anomaly.
• Increased lower lip tone
• Sometimes the lower lip acts like a sling on the upper incisors, which accentuates their vestibuloversion.
• The pressure of the tongue, if it exists, is located at the anterior level causing a biproalveolus with overbite.

3.  Class II 1 medium face 

These anomalies present an average face type with a slight anterior mandibular rotation. They are similar to class II 1 short face of lesser intensity. These are the most frequent cases.

7. Clinical forms:

BASSIGNY classification: according to associated anomalies

• Form 1: pure shift, no anterior alveolar abnormality, slight upper maxillary endoalveolism.
• Form 2: Class II molar case with upper alveolus. The incisor overbite is constant except for lingual interposition or parafunction.
• Form 3: Class II molar case with anterior open bite, Parafunctions or rarer lingual interposition.
• Form 4: Class II 1 case associated with DDM.

7- Long term consequences of class II division1

• Aesthetics  : early lip and cheek wrinkles.
• Traumatic  : if the teeth are visible, the risk of fracture is greatly increased in the event of facial trauma.
• Periodontal  : the immunological role of saliva is much less effective, for class II 1 with labial inocclusion, depending on the poor salivary irrigation and the relative dryness of the gum. In the long term, periodontal diseases, more frequent than usual on average, can appear.
• Occlusal  : DAM in predisposed subjects.

8. Conclusion :

Class II 1 can result from acquired or congenital malformations or functional disorders, hence the importance of a thorough clinical examination supplemented by radiological examinations which can guide the etiopathogenic diagnosis and the prognosis as well as the treatment which will be adopted at this assessment.

Class II division 1 malocclusions

  Untreated cavities can reach the nerve of the tooth.
Porcelain veneers restore a bright smile.
Misaligned teeth can cause headaches.
Preventative dental care avoids costly treatments.
Baby teeth serve as a guide for permanent teeth.
Fluoride mouthwash strengthens tooth enamel.
An annual checkup helps monitor oral health.
 

Class II division 1 malocclusions