Orthodontics

Class II division 1

By: Cezar Edward

Introduction

‘the lower incisor edges lie posterior to the

cingulum plateau of the upper incisors, there

is an increase in overjet and the upper

central incisors are usually proclined.

Aetiology

Skeletal pattern

Soft tissues

Dental factors

Habits

Skeletal pattern

A Class II division 1 incisor relationship is usually

associated with a Class II skeletal pattern,

commonly due to a retrognathic mandible

However, proclination of the upper incisors and/or

retroclination of the lower incisors by a habit or the

soft tissues can result in an increased overjet on a

Class I, or even a Class III skeletal pattern.

Soft tissues

the patient will try to achieve an anterior oral seal in one of

the following ways:

• circumoral muscular activity to achieve a lip-to-lip seal

• the mandible is postured forwards to allow the lips to meet

at rest;

• the lower lip is drawn up behind the upper incisors

• the tongue is placed forwards between the incisors to

contact the lower lip, often contributing to the development

of an incomplete overbite;

• a combination of these.

Dental factors

A Class II division 1 incisor relationship may occur

in the presence of crowding or spacing. Where the

arches are crowded, lack of space may

result in the upper incisors being crowded out of

the arch labially and thus to exacerbation of the

overjet. Conversely, crowding of the lower

labial segment may help to compensate for an

increased overjet in the same manner.

Habits

A persistent digit-sucking habit

The severity of the effects produced will

depend upon the duration and the

intensity”Force” and Position ”# of digits”

• proclination of the upper incisors;

• retroclination of the lower labial segment;

• an incomplete overbite or a localized anterior open bite;

• narrowing of the upper arch thought to be mediated by the tongue

taking up a lower position in the mouth and the negative pressure

generated during sucking of the digit.

It will make :

Occlusal features

The overjet is increased, and the upper

incisors may be proclined

The overbite is often increased, but may be

incomplete as a result of a forward adaptive

tongue position, a habit, or increased

vertical skeletal proportions.

Assessment of and treatment planning in

Class II division 1 malocclusions

Factors influencing a definative treatment plan

The patient’s age

The difficulty of treatment

The likely stability of overjet reduction

The patient’s facial appearance

Practical treatment planning

The likely stability of overjet

reduction

The soft tissues are the major determinant

of stability following overjet reduction.

Ideally, at the end of overjet reduction the lower lip should act on the

incisal one-third of the upper incisors and be able to achieve a competent

lip seal. If this is not possible, consideration should be given as to whether

treatment is necessary (if alignment is acceptable and the overjet is not

signifi cantly increased) and, if indicated, whether prolonged retention or

even surgery is required

Following overjet reduction, this

patient’s lips will probably be

competent. Therefore the prognosis

for stability of the corrected incisor

relationship is good

Class II division 1 malocclusion with a poor prognosis for the

stability of overjet reduction owing to the markedly incompetent lips

and increased vertical proportions. Prolonged retention would be

advisable.

The patient’s facial appearance

The decision as to whether extractions are required will depend

upon the presence of crowding,

Class II division 1 malocclusions are commonly

associated with increased overbite, which must be reduced

before the overjet can be reduced. Overbite reduction requires

space.

It is fair to say that headgear is associated with compliance problems;

to try and eliminate this a number of ‘non-compliance’ appliances have

been developed which aim to produce distal movement of the molars.

These can be classified as follows:

• Intramaxillary: anchorage derived from within the arch – anterior

teeth, premolars, coverage of palatal vault.

• Intermaxillary: anchorage derived from opposing arch. In Class II

cases this is the lower arch.

• Absolute anchorage: anchorage derived from implants (TADs).

Early treatmenttreatment for Class II division 1 malocclusions is best

deferred until the late mixed/early permanent dentition

where the transition from the functional to the fixed

appliance can be made straightaway without having to wait

for teeth to erupt; space can be gained for relief of

crowding and reduction of the overjet by the extraction of

permanent teeth (if indicated), and soft tissue maturity

increases thelikelihood of lip competence.

In the interim a custom-made mouthguard can be worn for

sports. However, if the upper incisors are thought to be at

particular risk of trauma during the mixed dentition,

treatment with a functional appliance can be considered

Management of an increased overjet

associated with a moderate

to severe Class II skeletal pattern

(1) Growth modification

(2) Orthodontic camouflage

(3) Surgical correction

by attempting restraint of maxillary growth,

by encouraging mandibular growth, or by a combination of the two

( Fig. 9.14 ). Headgear can be used to try and restrain growth of the

maxilla horizontally and/or vertically, depending upon the direction

of force relative to the maxilla. Functional appliances appear

to produce limited restraint of maxillary growth whilst encouraging

mandibular growth.

(1) Growth modification

Fig. 9.14 Patient treated by growth

modification. Because correction required a

combination of restraint of vertical and forward

growth of the maxilla and encouragement of

forward growth of the mandible, a functional

appliance with high-pull headgear was used:

(a, b) pre-treatment aged 12 years; (c, d)

following a year of retention aged 15 years.

A B

CD

Recent work has suggested that predictors

of a successful outcome are

• Mandibular retrusion (Pogonion to Nasion

perpendicular > 7 mm)

• The angle between the ramus and the

lower border of the mandible

(Condylion-Gonion-Menton) is <123°

using fixed appliances to achieve bodily

retraction of the upper incisors ( Fig. 9.15 ). The severity of the case that

can be approached in this way is limited by the availability of cortical

bone palatal to the upper incisors and by the patient’s facial profile.

(2) Orthodontic camouflage

Patient with Class II division 1 malocclusion on a moderately severe Class II

skeletal pattern treated by orthodontic camouflage in which

both upper first premolars were extracted to gain space for overjet reduction and

fixed appliances were used for bodily retraction of the upper incisors:

(a–c) pre-treatment (note the upright upper incisors); (d–f) post-retention.

Unfortunately, ‘gummy’ smiles associated with increased vertical

skeletal proportions and/or a short upper lip will often worsen as the

incisors are retracted. Therefore active steps should be taken to

manage this problem. Milder cases are best managed by either the use

of highpull headgear to either a functional type of appliance or a

removable appliance, for example, a Maxillary Intrusion Splint to try

and restrain maxillary vertical development while the rest of the

face grows. In severe cases of vertical maxillary excess or where there

is an excessive amount of upper incisor show in an adult patient,

surgery to impact the maxilla is advisable.

Retention

Relapse encompasses the return following

treatment of the original features of the

malocclusion as well as long-term growth

and soft tissue changes. so retention must

be discussed with, and planned, for every

patient.

Key points

• Class II/1 malocclusions are commonly associated with an underlying

Class II skeletal pattern with a retrusive mandible

• For cases with an underlying Class II skeletal pattern the options are

growth modification, camouflage or surgery

• Research evidence would suggest that growth modification produces

limited skeletal effects over and above normal growth

• Research indicates that early (two-phase) treatment does not have any

benefits over conventional treatment

Reference