Dentoalveolar compensation

DENTOALVEOLAR
COMPENSATION
www.indiandentalacademy.com

CONTENTS
uction
orm & malocclusion tendencies
sional and alignment pattern combinations
nathic Surgery
ion for orthognathic surgery
pensation
mination of compensation or dysplastic development

INTRODUCTION
In our life time, we have seen the faces of thousands of people ,
and each face is recognizable to us as distinct individual.
No two faces are quite alike, even those of identical twins.
The coordination of the development of the upper and the lower
jaws are far from perfect. This imperfection can be compensated by
skeletal and dentoalveolar changes camouflaging the actual
deviation.
This mechanism first described by Bjork as
the “dentoalveolar compensatory mechanism” andwww.indiandentalacademy.com

“ Process or mechanism by which the
development of dental and alveolar arches are
controlled so as to secure occlusion of the teeth
and adaptation to the basal parts of the jaws.”

What is compensation ???
It is a constant ongoing process striving towards ultimate
homeostasis during growth .
When the growth process is complete a state of compromise
equilibrium has been achieved .
Compensation can be more aptly called as
“ Developmental adjustments for working towards balance ” .

If we have compensatory features , the built in tendencies are
offset , to a greater or lesser extent . If it is less then complete
malocclusion will be more fully expressed but less severe than
the tendencies otherwise could produce.

HEAD FORM & MALOCCLUSION
TENDENCIES

Shape of the head
There are two basic extremes in the shape of the head
Dolichocephalic
Brachycephalic
The cephalic index is the ratio between overall head length
& breadth: -
-Dolichocephalic = Upto 75.9%
-Mesocephalic = 76 to 80.9%
-Brachycephalic = Over 81%

Dolichocephalic head form
Brain is horizontally long and narrow

Cranial base is flat- flexure between the middle cranial floor &
anterior cranial floor open .
Occlusal plane is rotated downward.

mandibular retrusion,
class II molar relation
The resultant profile is retrognathic.

BRACHYCEPHALIC HEAD FORM
Brain is short, wide.

Basicranial floor is more upright and has a more closed flexure
Decreased effective antero-posterior dimension of the middle
cranial fossa
Posterior placement of the maxilla
Horizontal length of the nasomaxillary complex is short.
Retrusion of nasomaxillary complex and more forward
relative placement of mandible.

The resultant profile is prognathic
Class III molar relationship

Growth of any given facial or cranial part relates
specifically to other structural & geometric "counter
parts" in the face & cranium.
e.g maxillary arch is a counterpart of mandibular arch
If part and counter part enlarge to same extent , balanced
growth is produced.
COUNTERPART PRINCIPLE

COUNTERPART ANALYSIS
In this method various facial and cranial parts are compared with
each other.
The individual is measured against himself,rather than compared
with population standards and norms.
Size and alignment of the bones are considered.
Vertical and or horizontal size of one given part is compared with
that of its specific counter parts. If they exactly match, or nearly so ,
a dimensional balance exist between them.

1. Cranial floor ramus vertical..
2. Posterior nasomaxilla..
3. Anterior nasomaxilla..
Three vertical architectural counterparts

Downward occlusal rotation
Upward occlusal rotation
Open bite
If vertical dimensional imbalance occurs

4. Middle cranial fossa
5. Ramus
6. Maxilla
7. Mandibular corpus
Four horizontal architectural counter parts

Maxillary protrusion
Dimensional compensation-
Ramus
Dimensional compensation-
Corpus
Horizontal dimensional imbalance

Factors responsible for dentoalveolar
compensatory mechanism
1. Normal eruptive system
2. Soft tissue envelope
3. Influence on tooth exerted by neighboring teeth
during growth

Dentoalveolar compensatory mechanism and
malocclusion
Two main types of malocclusion:
• Inter arch deviation - occlusion anomalies
• Intra arch deviation - space anomalies

1. An optimally functioning dentoalveolar compensatory
mechanism
2. In cases where functioning of dentoalveolar mechanism is
incomplete
3. In cases where for some reason the compensatory
mechanism is inoperative
Three main situations where dentoalveolar compensation is
impaired .

DIMENSIONAL AND ALIGNMENT
PATTERN COMBINATIONS

Horizontal dimension of the mandibular corpus
short relative to its counter part
Mandibular retrusion,
Anterior crowding .
Need not be class II www.indiandentalacademy.com

Mandibular corpus is dimensionally longer
relative to its counter part
Mandibular protrusion
Class III molar relation depends on whether mandible is
long mesial or distal to the I molar.
Horizontally short maxillary arch has the same effectwww.indiandentalacademy.com

Horizontally long nasomaxillary complex
No effect on occlusion
Individual can appear retrognathic – protrusive nature of
upper part of face.

Horizontal dimension of the ramus is narrow relative to
its counterpart-middle cranial fossa
Mandibular retrusive effect.
This is one of basic skeletal cause that underlie a class II molar
relationship

Mandibular protrusion.
One of the reasons for class III molar relation
The effective horizontal dimension of the ramus is broad
relative to middle cranial fossa

Vertically long nasomaxillary complex
Downward and backward rotation
Mandibular retrusion

Vertically short nasomaxillary complex
Upward and forward rotation
Mandibular protrusion

The PM plane is a developmental
interface between the vertical series of
counterparts in front of, and behind it.
This key plane retains these basic
relationships throughout the growth
process.
The Posterior Maxillary Plane

Neutral Occlusal Axis (N.O.A.):-
In a well balanced face both functional occlusal plane and
N.O.A. will be coinciding.

The alignment of parts are in neutral position.
Occlusal plane is perpendicular to PM plane and parallel to neutral
orbital axis

COMPENSATORY MECHANISM
During the development and establishment of the occlusion,
ongoing and intensive adjustment occurs involving
dentoalveolar remodeling .
The effect of dentoalveolar compensatory mechanism on
dimension of the dental arches ,the inclination of the teeth
and occlusal relationships has been well documented

Compensation by ramus in dolicocephalic
pattern

Mid facial growth has exceeded the growth of ramus and middle
cranial fossa complex
Downward backward alignment of the whole mandible to
accommodate the longer nasomaxillary complex..
Nasomaxillary complex lengthened vertically

Upper teeth drift inferiorly till they contact the antagonist.
Occlusal plane is a straight line , inclined downward.

Upper teeth drift down . The upper anterior drift only to the level of
the premolar.
Anterior mandibular teeth drift superiorly till they contact the
upper.
Occlusal plane is curved.
Dentoalveolar curve (Curve of spee)

ANTERIOR
CROWDING
Teeth have very little capacity to remodel after they are formed
fully. Only a limited extent of root resorption, deposition of
cementum , crown wear are possible in this regard. This means that
adaptive adjustment for a tooth must be carried out by the
displacement process .

While extensive resorptive & depository remodeling is a
basic growth function for the housing alveolar bone, it is
not a factor for the tooth itself . Thus anterior crowding is ,
in effect, a compensatory means by which the teeth are
housed beyond the limit provideded by the alveolar bone .

Compensation for variation in the sagittal jaw
relationship.
• In cases of skeletal class II.
To compensate for the large sagittal discrepancy in jaw
relationship the upper incisor are retroclined and lower incisor are
proclined to maintain normal overjet.
• In cases of skeletal class III.
The upper incisors are proclined and the lower incisors are
retroclined to maintain normal overjet.
(Hiroyaki ishikava et.al)

Compensation for variation in vertical jaw
relationship.
• In cases of skeletal open bite,
To maintain the normal overbite, the posterior dentoalveolar
segment intrudes. The anterior dentoalveolar segment extrudes or
both can happen.
• In a case of skeletal deep bite
The posteriors can extrude or the anteriors can intrude to
maintain a normal overbite.

Compensation for variations in transverse jaw
relationship.
• A discrepancy between a narrow maxillary base and a
wide mandibular base is compensated by buccal tilting of
upper teeth and lingual tilting of lower teeth.
• Discrepancy between wide maxillary base and narrow
mandibular base is compensated by lingual tilting of upper
teeth and by buccal tilting of lower teeth.

In ideal situations, this compensation masks discrepancies in
all three planes of space. The dentoalveolar changes may however
also be unfavourable or dysplastic and contribute to an occlusal
problem more severe than that caused by actual skeletal
discrepancy .

Orthognathic Surgery:-
Every patient who goes for a surgical line of treatment
should be put on an orthodontic appliance to carry out the
presurgical decompensation.
Here upper and lower arches are separately aligned but no
attempt is made to correct the bite by orthodontic means as
bite will be corrected by surgical repositioning of the jaw to
get a near occlusal fit as possible.

INDICATION FOR PRE-SURGICAL ORTHODONTICS
( BELL AND PROFIT )
1 ) When the skeletal & dento osseous
segments cannot be placed
in a satisfactory relationship because of
gross occlusa1
interferences or gross malrelation of
teeth to their supporting bone .
2 ) When postsurgical orthodontic work would
necessitate tooth www.indiandentalacademy.com

What is decompensation?
In many cases of severe jaw imbalances and the resulting
malocclusion, the teeth are inclined in such a manner as to partially
offset the discrepancies.
Pre surgical orthodontics should be aimed at removing this natural
compensation or to decompensate.

NEED FOR PRESURGICAL DECOMPENSATION
1. To position the teeth in an ideal axial inclination with
respect to the jaws.
2. To optimize the magnitude of surgical advancement
or repositioning.
3. For better esthetics , stability and function.
4. If malpositioned anterior teeth are not corrected , they may
hinder the repositioning of jaws at the time of surgery.

Determination of compensation or
dysplastic development
IN THE MAXILLA, the "maxillary
zone" measured as the angle between the
palatal plane (ANS-PNS) and the maxillary
occlusal plane ( mean 10 +- 3 ), describes
the extent of compensatory or dysplastic
development.

IN THE MANDIBLE, the "mandibular zone"
measured between the mandibular plane (Go-Gh)
and the mandibular occlusal plane (mean 20
+- 4) similarly describes possible
compensation.
If one or both of these
measurement are increased in a patient with
increased vertical jaw relations; favourable
dentoalveolar compensation is indicated. Onwww.indiandentalacademy.com

Dentoalveolar compensation in negative over jet
cases were statistically confirmed for both incisor
inclination and occlusal plane angulation.
However the compensatory effects were weaker
than with positive overjet cases.
Hiroyaki ishikava et.al

Dentoalveolar compensation

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