Occlusion./ orthodontic continuing education

OCCLUSION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

CONTENTS
 Introduction
 History
 Alignment and occlusion of the dentition
-Factors and forces that determine tooth
position
-Intra-arch tooth alignment
-Inter-arch tooth alignment
-Occlusal contacts during mandibular
movements
 Summary
 References www.indiandentalacademy.com

INTRODUCTION
According to Glossary of Prosthodontic Terms:
“Occlusion is the act or process of closure or of
being closed or shut off”
Ramfjord and Ash: Occlusion = Contacts
between teeth
“Multifactorial functional relationship between
the teeth and other components of the
masticatory system as well as with other areas
of the head and neck that directly or indirectly
relate to function, parafunction or dysfunction of
the masticatory system.”www.indiandentalacademy.com

Masticatory
system
Teeth
Periodontium Articulatory
system TMJ
Muscles Occlusionwww.indiandentalacademy.com

HISTORY
Development of concept of occlusion--
Three periods:
1. Fictional period (prior to 1900)
2. Hypothetical period (1900-1930)
3. Factual period (1930 to present)

1.Fictional period:
Fuller, Clark and Imrie-Antagonism,meeting
or gliding of teeth.
Kingsley(1880)– “Norm”
Talbot’s-(1903)Irregularities of teeth and their
treatment.
2.Hypothetical period:
Edward H. Angle(1899)- “Old Glory” and “Key
to Occlusion”.
Matthew Cryer and Calvin Case-Occlusion
referred to the closure of the teeth one upon
the other.

Bennett (1908)-Functional analysis or
dynamic approach to occlusion.
Turner(1903)-Concept of physiologic rest.
Lister and Simon(1922)-Related teeth to the
rest of the face and cranium.
Milo Hellman-Racial variations in normal
occlusions.
3.Factual period:
Difference between static and dynamic
concepts of occlusion.
Broadbent and Planer-(1930)
Occlusion=Interdigitation of teeth + Status of
controlling musculature and functional factors.www.indiandentalacademy.com

Alignment and occlusion of the dentition:
Tooth positions are determined by various
controlling factors such as:
1. Factors and forces that determine tooth
position.
2. Intra-arch tooth alignment.
3. Inter-arch tooth alignment.

1.Factors and forces that determine tooth
position.
(a)Surrounding musculature:
Labial to teeth are lips,cheeks-lingually directed
forces
Tongue-labially and bucally directed forces.

Oral habits-biting on
pipe,musical instruments.
(b)Proximal surfaces:
Proximal contact wear-
mesial drift( because of
functional response of
alveolar bone and gingival
fibres)
(c)Occlusal contacts:
prevents extrusion.
Abnormal muscular pattern-
Tongue thrust and visceral swallow.

2.Intra-arch tooth alignment:
-Relationship of the teeth to each other
within dental arch.
Plane of occlusion is not flat.www.indiandentalacademy.com

The curvature of the occlusal plane is due
to the varying degrees of inclination of
teeth in the dental arches.

THE OCCLUSAL SURFACE
The area of tooth between buccal and
lingual cusp tips is called the occlusal
table.

(a) Inner inclines
(b) Outer inclines

3.Inter-arch tooth alignment:
-Relationship of the teeth in one arch to
those in the other.
Arch length-
Maxilla – 128 mm
Mandible – 126 mm
Arch width: Distance across arch.

The buccal cusp of mandibular posterior
teeth and lingual cusp of maxillary posterior
teeth occlude with the opposing central fossa
areas – Supporting cusps.

The centric cusp are broad and rounded.
The The buccal cusp of maxillary posterior
teeth and lingual cusp of mandibular
posterior teeth– Guiding or non-centric cusps
(sharp, with definite tips)www.indiandentalacademy.com

Functional outer aspect:
Present only on outer aspect of centric cusp.
This area assists in shearing of food therefore
non-centric cusps- shearing cusps.
Non-centric cusps
provide stability to the
mandible in maximum
intercuspal position.
Guiding cusps.

BUCCOLINGUAL OCCLUSAL CONTACT
REALATIONSHIP

Proximal contact
areas located slightly
buccal to the C-F
Line-Greater lingual
embrasure area--
Major spillway. www.indiandentalacademy.com

MESIO-DISTAL OCCLUSAL CONTACT
REALATIONSHIP
These cusp typically contacts
1. Central fossa areas: The actual contact point
are called centric stops, holding contacts, as
they serve to hold the teeth in a stable
position.

2.Marginal ridge and embrasure areas:
Marginal ridge is slightly convex areas,
therefore the type of contact is cusp tip
contacting a flat surface.

COMMON OCCLUSAL RELATIONSHIPS OF
POSTERIOR TEETH
CLASS-I

COMMON OCCLUSAL RELATIONSHIPS OF
ANTERIOR TEETH
Maxillary anterior teeth-labial to mandibular
anterior teeth.
Inclined labially (12º-28º).
Normally incisal edges of lower incisors
contacts lingual surfaces of upper incisors in
the lingual fossae which is 4mm gingival to
incisal edges.

In normal occlusion, contacts on the anterior
teeth in the intercuspal position are much
lighter than on the posterior teeth.
Purpose of the anterior teeth-guide the
mandible through various movements.
Anterior guidance- It is the anterior tooth
contact that provide guidance to the mandible.
-determined by exact position and
relationship of the anterior teeth which can be
examined both horizontally and vertically.

Overjet:distance between
the labial incisal edge of
maxillary incisor and labial
surface of mandibular
incisor.
Overbite:distance
between the incisal
edges of the
opposing anterior
teeth.www.indiandentalacademy.com

OCCLUSAL CONTACTS DURING
MANDIBULAR MOVEMENTS
The TMJ’s and the associated muscles allows
the mandible to move in all three planes-
(Sagittal,Frontal and horizontal) which
ultimately influences contact patterns on the
occlusal surfaces of the posterior teeth.
Eccentric- any movement of the mandible
from the intercuspal position that results in
tooth contact.
Three types:Protrusive, Laterotrusive,
Retrusive. www.indiandentalacademy.com

PROTRUSIVE

LATEROTRUSIVE

RETRUSIVE

SUMMARY

REFERENCES
 Occlusion series in BDJ, 2001;191:6-7
 Okeson JP. Management of
Temporomandibular Disorders and
Occlusion, ed. 4th
, 1998; Mosby
 Ash MM and Ramfjord S. Occlusion, ed. 4th
,
1966; WB Saunders Company, Michigan
 Santos JD. Occlusion Principles and
Concepts, ed. 2nd
, 1999; Ishiyaku
EuroAmerica, Inc. U.S.A.
 Shillingburg HT. Fundamentals of Fixed
Prosthodontics, ed.3rd
, 1997;Quintessencewww.indiandentalacademy.com

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Occlusion./ orthodontic continuing education

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