Class II Malocclusion

Etiology and Diagnosis

Class II malocclusion
Introduction

Normal occlusion
Angle’s view (Dental cosmos 1899)

Each dental arch describes a graceful curve, and that the teeth in these arches are so
arranged as to be in the greatest harmony with their fellows in the same arch, as well as with
those in the opposite

Division 1

a. Narrow upper arch, with lengthened and prominent upper incisors; lack of nasal and lip
function, Mouth breathers

b. Same as a, but with only one lateral half of the arch involved, the other being normal, Mouth-
breathers

Division 2

a. Slight narrowing of the upper arch; bunching of the upper incisors, with
overlapping and lingual inclination; normal lip and nasal function

b. Same as (a), but with only one lateral half of the arch involved, the other being
normal; normal lip and mouth function

In spite of Angle's important contribution, it became clear during the early part of the twentieth
century that this classification system was inadequate to characterize the variety of
manifestations of malocclusion presented by skeletal and dental discrepancies in all three planes
of space
Differential diagnosis of Class II malocclusions - Robert E. Moyers et al

With the help of 697 subjects Use of computer statistics Combined analysis of skeletal and
dental features Six subgroups based on horizontal variables

Type A

A normal skeletal profile

The occlusal plane is normal, as placed normally on its base

Maxillary dentition is protracted

Result – a class II molar relationship and a greater-than-normal incisal overjet and overbite

Type B

A class II skeletal profile due to midface prominence associated with a mandible of normal size

The mandible is in a normal relationship antero-posteriorly

The anterior cranial fossa tends to be flat

Type C

Generally smaller facial dimensions than other class II types

There is a markedly class II profile, even though both the maxilla and the mandible are farther
back beneath the anterior cranial base than the normal

Lower incisors - tipped labially

Upper incisors - either upright or tipped off the base labially according to the vertical category

It is a severe skeletal class ii with a short mandible, a short maxilla, a squarish gonial angle, and
a flat anterior cranial base

Type D

A retrognathic skeletal profile -- small mandible combined with a normal or slightly diminished
midface

The mandibular incisors – either upright or lingually inclined

Maxillary incisors – extremely labially inclined

Type E

A severe “class II” profile – prominent midface and normal or even prominent mandible

Bimaxillary protrusion class ii malocclusions are more likely to be horizontal type e than any
other
Both dentitions, in Type E, have a tendency to be forward on their bases and the incisors are
often in strong labioversion

Type F

Large heterogeneous subgroup with the mildest class II tendencies

Not well-defined, rigid syndromal class II type but, rather, a loose collection of cases displaying
some skeletal class II characteristics

The skeletal profile tends to be less severe than syndromal Types B, C, D, and E

The mandible is small, and the midface may be small

The tooth positions reflect the vertical subsets associated with Type F

HORIZONTAL TYPES

Type A

Type B

Type C

Type D

Type E

Type F

Vertical types

Type 1 a mandibular plane steeper than normal, steeper functional occlusal plane, palate which
is tipped somewhat downward The anterior cranial base tends to be upward
The result -- an anterior face height - significantly greater than the posterior face height

Type 1 -- a “steep mandibular plane” or a “high angle” case

Type 2

Essentially a square face

The mandibular plane, functional occlusal plane, and palatal plane are all flatter than normal and
are nearly parallel

The gonial angle approaches orthogonality & anterior cranial base more horizontal than normal

Under these conditions, the incisors tend to be vertical and in deep-bite

Type 3

Palatal plane which is tipped upward anteriorly

During growth, the upper face height does not keep pace with the total face height, resulting in a
strong tendency to open-bite
When the mandibular plane is steeper than normal in vertical type 3, a skeletal anterior open-bite
is inevitable

Type 4

Mandibular plane, the functional occlusal plane, and the palatal plane are all tipped markedly
downward, leaving the lip line unusually high on the alveolar process in the maxilla

The gonial angle is obtuse

The lower incisors are tipped lingually

Vertical type 4 is among the most rare, severe, and anomalous of the vertical types

Type 5

Closely related to type 2 “the square face syndrome, ” and is found only in horizontal subgroups
B and E

The mandibular and functional occlusal planes are normal

The palatal plane is tipped downward

gonial angle is the most squarish of all the types, resulting in a skeletal deep-bite

The lower incisors are found in extreme labioversion, whereas the upper incisors are nearly
vertical

Vertical Type I --- Types C, D, and F

Vertical Type 2 -- found in all horizontal types, although it is the dominant feature of horizontal
Types B and E

Vertical Type 4, as noted earlier, is a severe rare group limited to horizontal Type B

Vertical Type 5 is found predominantly in horizontal Types B and E

Etiology

Considered to be ‘multifactorial’

Lundstrom reported that in monozygotic twins 68% of concordance of having class II

malocclusion than dizygotic (24%)
But when we see the same in case of open bite we find 100% concordance rate in monozygotic
& 10% for dizygotic

So even with an identical genotype class II malocclusion does not always develop

According to Graber, the Aleuts – no Class II

South African blacks – 2.7%

Several investigators suggested additional etiological factors that particularly pertain to cl II div
2

a. Genetic predisposition :- Leech published a case report on identical twin, one having Div 1 &
other Div 2

b. Genetically determined abnormal axial inclination of the maxillary central incisors :-

Milne and Cleall indicated that if the tooth bud develops with a
more vertical axial inclination, the tooth would assume a more vertical position after eruption

c. Variation in morphology of max central incisors

Nicol - difference in crown root angulation in div 2 cases

Robertson & Hilton - crowns of U1 thinner labiolingually in Div 2

d. Forward tipping of maxillary posterior segment :-

Swann showed a definite pattern involving the timing of development of max

tuberocity & max tooth eruption resulting in mesial tipping of max posterior teeth

Environmental factors

Important role

Early loss of max 2nd deciduous molar

Flush terminal plane – common in deciduous dentition

Persistent finger habit displacing max dentition forward, tip the occlusal balance more towards
cl II

May lead to lower lip trap, hyper active mentalis – intern tips U1 more labially

Persistent finger, tongue or lip habits can either result in a cl II malocclusion or accentuate an
existing one

So preventing measures if any will be limited to environmental factors only

Diagnosis
Prevalence of malocclusion

The prevalence of malocclusion in north India (Delhi children) age 10-13 years is 45% (44.97%)

class I malocclusion is 26% (25.87%),

class II 15% (15.2%)

class III 3.5%

The prevalence of malocclusion in rural children in Haryana (age group 12-16) is (55%)

Class I malocclusion is (44%)

class II (10%)

class III (0.6%)

bimaxillary protrusion (0.5%)

bilateral mutilations (0.8%)

Definite ethnic trend in prevalence of type of malocclusion from north to south India

For class II

Bangalore & Tiruvanantapuram :- close to 5%

In Delhi & Haryana :-10 – 15 %

Characteristic of Class II malocclusion

1. Maxillary Dental Protrusion

Confused with antero-posterior maxillary excess or midface protrusion

Both conditions are characterized by facial convexity

How to differentiate clinically

Excessive overjet is a reliable feature of this dental malocclusion

Generalized maxillary spacing associated with the protruded maxillary incisors may be noticed

The mandible and mandibular dentition are in a normal anteroposterior position

Cephalometric Presentation

Normal anteroposterior

ANB, SNA, and SNB angle

AO-BO difference

True horizontal anteroposterior position of A and B relative to nasion perpendicular

Normal linear measures of the maxilla and mandible

The mandibular incisors -- normal anteroposterior position relative to the NB line, mandibular
plane, and frankfort horizontal

Abnormal values -

for maxillary incisors,

A protrusive position relative to lines NA, SN, and frankfort horizontal

2 . Mesial Drift of the Maxillary First Permanent Molars

This dental class II relationship may be unilateral or bilateral

If no incisor protrusion results in crowding of the maxillary arch caused by the loss of space in
the arch perimeter

Maxillary tooth size deficiency lead to spacing –lead to mesial migration of u6

Partial anodontia/ microdontia u2, u4

Because of loss of arch lengh due to mesial migratio of u6 – lead to crowding, impacted u3/ u4

The class II division 2

Have excessive lingual inclination of the maxillary central incisors overlapped on the labial by
the maxillary lateral incisors

In some cases, both the central and the lateral incisors are lingually inclined and the canines
overlap the lateral incisors on the labial

a The central incisors are tipped lingually, the laterals are in labio-version or normally inclined

b All four incisors are tipped lingually and the canines are in mesiolabioversion

c Linguoversion of all six anterior teeth

d Mixed type of frontal malposition, with lingually inclined incisors on one side
Deep overbite and minimal overjet

In cases with extreme overbite, the incisal edges of the lower incisors may contact the soft
tissues of the palate

In a few class ii division 2 cases, the mandibular labial gingival tissues may be also traumatized

two distinct occlusal levels,

supra occlusion for the anterior teeth

relative infra occlusion for the posterior segments

An exaggerated curve of Spee may be present in the mandibular arch with extrusion of the
mandibular incisors (Strang 1958)

Shape and relationships of the dental arches in Class II cases

Frolich evaluated the dental arch form during the transitional dentition of children with Class II
malocclusions who did not undergo orthodontic treatment

divided into four subgroups:

Class II Division 2

Class II borderline between Division1 & 2

Class II Division 1 with a "V' shaped maxillary arch

Class II Division 1 with flaring and spacing of the maxillary incisors

No appreciable differences were present between normal and Class II individuals in absolute
arch length and width

Anterior arch length was found to increase markedly during the transition period for all Class II
types, except the Division 2 group

Overbite and overjet increased in the untreated Class II Division 1 cases and only excessive
overbite increased in the Division 2 cases

Frolich found the shape of the mandibular dental arch to be very similar in all four categories of
Class II malocclusion, but the maxillary dental arch was wider in the Division 2 cases

Clinical significance

As a result, it is very difficult to distinguish and predict the ultimate shape of the dental arch
before the eruption of the permanent incisors
It has also been established that the anteroposterior relationship of the dental arches in untreated
Class II cases, whether in the deciduous, mixed, or permanent dentitions, did not improve with
age (Bishara 1988)

Transverse dental arch relationship in Class II Division 1 patients

Bishara and coworkers (1996) evaluated the changes in the dental arch width and length from the
deciduous to the mixed and permanent dentitions

The differences between the measurements of maxillary and mandibular intermolar arch widths
were greater in the normal subjects than in subjects with Class II Division 1 malocclusions.

The presence of this relative constriction of the maxillary arch, when related to the mandibular
arch in Class II malocclusions, is expressed from the earlier stages of dental arch development

Clinical significance

These trends continue in the mixed and early permanent dentitions and do not self-correct
without treatment

Therefore, if there is a discrepancy in the transverse relationship, it should be corrected together

with the anteroposterior discrepancy

Skeletal Characteristics of Class II Malocclusions

In general, Class II cases with anteroposterior skeletal discrepancies are characterized by a large
ANB angle and Wits Appraisal, reflecting the malrelationship between the maxilla and mandible

The anteroposterior skeletal discrepancies may also be accompanied by a vertical discrepancy,

for example, a relatively long or short anterior face

Skeletal discrepancies associated with Class II malocclusions have been termed skeletal Class II
relationships

This term indicates that the Class II malocclusion is one resulting from an anteroposterior
disproportion in size or discrepancy in position of the jaws rather than malposition of the teeth
relative to the jaws

Skeletal class II relationships often are associated with class II dental malocclusions

Natural dental compensation can be observed in the presence of the skeletal discrepancy – dental
discrepancy less severe than the skeletal discrepancy

Most often as protrusive mandibular incisors

Less frequently as retrusive maxillary incisors

Maxillary dental arch that is more narrow or constricted than normal because it is in occlusion
with a narrower part of the mandibular dental arch

This transverse dental compensation is characterized further by mesio-lingual rotation of the

maxillary first molars

Mandibular Deficiency

A skeletal class II relationship resulting from a mandible that is small or retruded relative to the
maxilla is termed a mandibular deficiency

Characterized by

normal nasolabial angle,

Relative protrusion of the maxillary anterior teeth and

Relative deficiency of the chin caused by the small size or retruded position of the mandible

A pronounced labiomental fold

Lower lip trap

Resulting in lip incompetence

The consequence - further protrusion of the maxillary incisors

Inadequate vertical support for the maxillary Incisors - overeruption of these incisors

Cephalometric analysis – downward and backward rotation of the mandible caused by the small
size of the ramus and body of the mandible

Decreased posterior facial height

A steeper mandibular plane angle

An increased ANB angle

Normal SNA , decreased SNB angle

Normal position of point A but a posterior position of point B relative to nasion perpendicular

Retrusion of a normal-sized mandible

The cranial base angle, defined by points nasion, sella,and basion, often is more obtuse ---
glenoid fossa in a relatively posterior position

The distinguishing characteristics –

Normal size of the mandibular ramus and body

Normal lower face height in spite of the anteroposterior discrepancy between the maxilla and
mandible

Maxillary Excess

Maxillary excess may present as overdevelopment in the vertical or anteroposterior dimension or

both

vertical maxillary excess:-more localized to the posterior area, associated with the maxillary
posterior teeth being in an inferior position with a normal vertical position of the incisors

Presentation usually as :- anterior open bite with a normal vertical display of the maxillary
incisors relative to the upper lip both in repose and upon smiling

Vertical maxillary excess - overall excess

No anterior open bite, but an excessive vertical display of the maxillary incisors relative to the
upper lip in repose as well as a gummy smile

In either of these two presentations, the mandible is rotated downward and posteriorly (clockwise
rotation), resulting in the class ii skeletal relationship

Maxillary excess in the anteroposterior dimension or midface protrusion

Can be easily confused with maxillary dental protrusion

Both conditions exhibit facial skeletal convexity with a normal anteroposterior position of the
mandible

But maxillary anteroposterior excess characterized by a protrusion of the entire midface,

including the nose and infraorbital area as well as the upper lip

Cephalometric features of anteroposterior maxillary excess

Increased ANB angle and A-B difference

Increased facial convexity

SNA angle increased, SNB angle is normal

A point is anterior, and B point is normal

Anteroposterior maxillary length increased

Anteroposterior mandibular length normal

Anteroposterior dental compensation in the form of

Mandibular incisor protrusion and transverse dental compensation in the form of

maxillary constriction

Combination of Mandibular Deficiency and Maxillary Excess

It is likely that most patients with skeletal class II problems have a combination of mandibular
deficiency and maxillary excess.

Maj and coworkers concluded that the skeletal differences were not due to an abnormal
development in the size of any specific part, but rather were the result of an abnormal
relationship between the parts, that is, the result of variations in the position of the skeletal
structures, in the direction of the discrepancy

Cephalometric characteristics of the Class II Division 2 malocclusion

Wallis compared Class II Division 2 , Class I and Class II Division 1 individuals and found that
the posterior cranial base was larger in Division 2 cases

He also noted that the mandibular found in a "typical" Division 2 case has relatively more acute
gonial and mandibular plane angles, shorter lower anterior face height, and excessive overbite

Hedges concluded that the only consistent cephalometric finding was the lingual axial inclination
of the maxillary central incisors

Perioral Functional Characteristics of Class II Malocclusions

Abnormal muscular patterns may be associated with either type of Class II malocclusions

As in Class II Division I, the increased overjet may allow the lower lip to rest between the
maxillary and mandibular incisors maintaining or accentuating the overjet.

During swallowing

An abnormal mentalis muscle activity and aberrant buccinator activity,

together with compensatory tongue function and position, could cause changes in dentofacial
structures

Such as constriction of the maxillary posterior segments, protrusion and

spacing of the maxillary incisors, and abnormal inclination of the mandibular incisors

In Class II Division 2 individuals, the orbicularis oris and mentalis muscles are often well
developed and active
The lingual inclination of the maxillary incisors may accentuate the appearance of the lower "lip
curl" associated wit the vertical over closure

In addition, the combined effects of the hyperactive mentalis muscle and the reduced vertical
height accentuates the chin prominence

Clinical significance

In summary, describing the skeletal discrepancies accompanying Class II Division l or 2

malocclusions as being a "skeletal Class II malrelationship“ is a diagnostic oversimplification
and of limited value in treatment planning

This is because the mandible can either be in a normal or retruded relationship to the maxilla,
and in turn the maxilla may be either normal or in a protruded relationship to the mandible

As a result, the clinician should evaluate and diagnose, in each individual patient, the occlusal
relationships, the anteroposterior and vertical skeletal discrepancies, the soft tissue facial
relationships, as well as the presence of any abnormal function for appropriate treatment
planning

CONCLUSION

• Class II malocclusions can be treated by several means, according to the characteristics

associate with the problem, such as anteroposterior discrepancy, age, and patient
compliance. Methods include extraoral appliances functional appliances, and fixed
appliances associated with Class II inter maxillary elastics, extraction and surgery..

• The clinician should evaluate and diagnose, in each individual patient, the occlusal
relationships, the anteroposterior and vertical skeletal discrepancies, the soft tissue facial
relationships, as well as the presence of any abnormal function for appropriate
management of class II malocclusion
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