OCCLUSSION

1. OCCLUSION
BY_ARINDA MONDAL.

2. INTRODUCTION:
• When teeth erupt into the oral cavity, a new set of
factors influence tooth position.
• As the teeth come into function, genetic and
environment determine tooth position
• Dental occlusion varies among individuals according
tooth size and shape, tooth position, timing and
sequence of eruption, dental arch size and shape and
pattern of craniofacial growth.

3. Terminology used in occlusion:
• Normal Occlusion : – Normal occlusion implies
a situation commonly found in the absence of
disease. It should include not only a range of
anatomically acceptable values but also
physiological adaptability. –
--It is always a range never a point.
• Ideal Occlusion : – The concept of ideal or
optimal occlusion refers both to an aesthetic
and physiologic ideal.
--It includes functional harmony, stability of
masticatory system & Neuromuscular harmony

4. • Physiologic occlusion : – The occlusion that shows no
signs of occlusion related pathosis.
--It may not be an ideal occlusion but it is devoid of
pathological manifestations in the surrounding tissues.
• Traumatic occlusion : – An occlusion judged to be
causative factors in the formation of traumatic lesions
of disturbances in the orofacial complex.
• -abnormal occlusal stress which produce injury to
peridontium.
• Therapeutic occlusion : – It is a treated occlusion
employed to counteract structural interrelationship
related to traumatic occlusion.

5. Trauma from occlusion: it is defined periodontal injury
caused by occlusal forces through abnormal occlusal
contacts
• Occlusion – The relationship of maxillary and
mandibular teeth when they are in functional contact
during activity of the mandible
• Centric occlusion is the maximum contact and/or
intercuspation of the teeth
this is a static definition--it describes just one position
in the chewing cycle.
• Balanced occlusion:
Bilateral contacts in all functional excursions to prevent
tipping of the denture bases

6. Concept of occlusion:
• Concepts of occlusion vary with almost every specialty of
dentistry
• static occlusion --------dynamic occlusion .
• Static occlusion emphasizes the fit of particular part of
maxillary teeth to that of specified parts of mandibular teeth
• In 1907, Angle summarised his views as ‘occlusion shall be
defied as being the normal relation of the occlusal inclined
planes of the teeth when the jaws are closed’.
• Angle furnished his ‘key to occlusion’ and emphasizes the first
permanent molars especially the upper first permanent molar
and considers them to be most constant in taking normal
position
• Angle developed the concept that all teeth should be present if
normal occlusion is to be achive

7. Dynamic occlusion:
• Recognition of the role played by muscles physiology and the
TMJ has firmly entrenched the dynamic functional concept.
• The 13 muscle attachment to the mandible in addition to
articular capsule and tendon provide a high degree of stability of
position that occlusal equilibration and full mouth
reconstruction can’t change permanently
• The teeth are in occlusal contact only 2 to 6% of the time.
Therefore 94% of the time, they are apart.

8. • The largest segment of time is in postural rest
position determined by musculature.
• Postural rest position is a good place to start
an assessment of vertical status and harmony of
orofacial features Thus the idea of functional
rather than static relationship of occlusal
surface become important
• Functional disturbances of masticatory system
can be related to malocclusion , occlusal
dysfunction and disturbances of motor behavior
including bruxism.

9. Different factors affecting
the occlusion:
1) Development of dentition:
• a) The pre-dentition period.
• -This is from birth to six months.
• -At this stage, there are no teeth.
• -Both jaws undergo rapid growth; Forward growth for the mandible is
greater.
• -The maxillary and mandibular alveolar processes are not well developed at
birth.
• -occasionally, there is a neonatal tooth present at birth. It is a supernumerary
and is often lost soon after birth.

18. B. Deciduous dentition period.
• -The deciduous teeth start to erupt at the age of six
months 6 mon.—2 ½ years
• -The jaws continue to increase in size at all points until
about age one year.
• -After this, growth of the arches is lengthening of the
arches at their posterior (distal) ends.
Also, there is slightly more forward growth of the
mandible than the maxilla.
• The canines and molars are supposed to keep their
positive contact relation during all jaw growth.

19. Chronology and mean age of eruption of primary teeth:
• The timing of eruption or emergence of tooth is large part
to hereditary and somewhat environmental factor
• The timing of eruption or emergence of tooth of I ry dention
are independent of the development and maturation of child
• Maxillary emergence of tooth mandibulaar
i1 10(8-12) 8(6-10)---i1
I 2 11(9-13 13(10-16 i2
C 19(16-22 20(17-23 C
m1 16(13-1`9 16 (14-18 m1
m2 29(25-33 27( 23-31 m2

20. The eruption pattern for the deciduous dentition as a whole is:
• (1) central incisor
• (2) lateral incisor
• (3) deciduous first molar
• (4) then the canine
• (5) the second molar
• If deciduous teeth are retained too long, consider ankylosed
teeth or missing or impacted teeth.
• Primary arch form and width has been established for both I ry
and IInd ry dention by the age 9 month.

24. These physiological spaces
called Primate spaces as
they are commonly seen in
primates

28. • Flush terminal plane :
• Deviation of this terminal plane may be caries or any disturbance
may lead to disturbed occlusion.
• The effect of this decideous molar relationship have on the
permanent molars relationship
• It is lso influence by other factors , by the presence or absence of
several factors as mandibular growth, and sufficient leeway space to
accommodate mesial shift of permanent molars .

38. • Between ages 6 and 7 years of age there are:
• 20 deciduous teeth
• 4 first permanent molars
• 28 permanent tooth buds in various states of development
• 1. Errors in development.
• These are usually genetic.
• a. Variability of the individual teeth.
• b. Partial or total anodontia.. Heredity is significant.
-Illustration of supernumerary incisor
• c. Supernumerary teeth.
• d. Microdontia

39. • The growth of jaw provide space for the teeth to erupt
• Forward rotation of maxillomandibular complex,
influence the magnitude of tooth eruption as well as
anterioposterior position of incisors
• this change in anterioposterior position of incisors
which reflect major influence on change in arch length .
• The important portion of dental arch in development
of occlusion of permanent dentition is is premolar
segment.
• this dynamic change in arch dimension (mandibular
arch) is important in development of occlusion and
malocclusion.

41. • The relationship of dental arches to difference between the size
of teeth
• aggregate M-D dimension in posterior permanent teeth is less
than deciduous posterior M-D width
this difference is Leeway space
• Average M-D width size of primary dentition in that area is 47
mm
• Average size of permanent dentition in that area is 42.2 mm
• So average difference distance is 4.8mm
• This space provides the mesial movement of permanent molars
• This mandibular molar movement correct the end to end molar
relationship into normal molar relationship

48. • By the age of 12 yrs second permanent molar
erupt oriented in mesial and lingual direction
• eruption of permanent canine .
• Arch length is reduced by mesial eruptive forces
, thereby crowding if present is accentuated .

52. O

53. • These are most favorable sequence for the prevention of
malocclusion.
• Time of premolar eruption in mandibular arch is ahead of maxillary
arch.
• This is result of the difference in eruption timing of the canine in
two arches.
• Important portion of dental arch in development of occlusion is the
premolar segment as premolars
are smaller than deciduous molars

54. 2) Dental Arch Form:
• Teeth are positioned in arch form when viewed
from occlusal plane.
• Palatal arch is elliptoid ,paraboloid, u-shaped
,horse shoe shaped
• Arch form determined by the shape of
underlying bone.
• Malpositioning of individual teeth do not affect
arch form but if multiple teeth are misplaced
then asymmetries may develop.
-a tapered arch form e.g. thumb sucking habit
• Changes in arch form ,within anatomic limits
do not have Significant effect on occlusion
• Discrepancies in arch form between maxillary
and mandibular arches result in poor occlusal
relationship.

55. • Arch form of the maxilla tends to be larger
than that of mandible results in the
maxillary teeth overhanging the
mandibular teeth
• Thus some degree of
overhanging(overbite) is normal feature
of dentition.
• Overjet: lateral or anterioposterior ofthis
overhang is called overjet
• Overbite: vertical overlap of maxillary teeth
teeth on mandibular teeth

56. • Open bite:
Malocclusion in vertical plane ,with lack of contact between
segments of teeth
e.g tongue thrusting habit.
• Deep Bite/ Impinging bite
-the amount and percentage of overlap of lower incisors by the
upper incisors .
gingivitis and periodontitis may cause due to deep bite

57. • Cross Bite :
This may be seen in anterior or posterior teeth
• one or more front tooth that are “stuck back,” then they have an
anterior crossbite and in posterior teeth then posterior crossbite
• It may seen in single or multiple teeth

58. 3) Curvatures in Occlusal plane/compensatary curvatures
• Occlusal surface of the dental arches do not conform to flat plane
• Curve of Spee
• Curve of Wilson
• Sphere of Monson
Curve of von spee:
It is an anatomic curvature of the occlusal alignment of the teeth,
beginning at the tip of the lower canine, following the buccal cusps
of the premolars and molars
Helps in tooth guidance And incisal guidance, orthodontic and
restorative dentistry

59. • Curve of Wilson : The curve, viewed from the front, that contacts
thebuccal and lingual cusps of the molars, being lower in the middle
due to the lingual inclination of the long axesof
the mandibular molars. Named after Dr. George H. Wilson, who first
described the curve in 1911.

60. • Curve / Sphere of Monson
• It is a combination of Spee and Wilson curves.
• This curve is within sagittal and coronal
planes.
• This curve is convex for the occlusal surfaces
the upper dental arch and concave for the
lower dental arch
• When the upper & lower dental arches
are occluded in centric occlusion the curves of
the
upper & lower arches become identical and
form a
segment of a sphere of four inches radius
center of sphere is at the glabella

61. • Bonwill triangle
• The mandibular dental arch adapts itself to an equilateral triangle of
4 inches length.
• The apex of the triangle is located at the mesial contact area of the
lower central incisors. The angles of the base are found at the center
of each condyle

62. 4) Inclination & angulation of the roots of
the teeth:
Axial inclination of tooth and roots vary
Each tooth is positioned in the dental arch at an
angle that best withstands the forces of
mastication
The axial angulation of the incisors is about 60
degrees to the horizontal plane.
The axis of the maxillary incisor forms acute
angle with the axis of the mandibular incisor .
The angle between less acute in the canines
and the first premolars.
The maxillary and the mandibular second
premolar and the first molar have their axes
parallel to each other.
The second and third molars have their axes at
an angle more acute to the horizontal plane
than the first molar.

64. • The angulation of the root …..?
-aid in visualizing how x-ray beam directed to obtain normal
projection of roots of teeth
-relate the direction of occlusal forces in restorations along long axis of
teeth
- relate the control of orthodontic forces
-place dental implants with the right angulation

65. 5)The functional form of the crown at incisal and
occlusal third,
• is manifested by elevations and depressions.
• Elevations of the crown in one dental arch occlude with
crown depression on the opposing dental arch during
centric occlusion
Ridge to fossa : incisal ridge of lower 1&2 rest in the
lingual fosse of upper 1&2.
Cusp to fossa: MLC of upper molars rest in central fossae
of lower molars & DBC of lower molars rest in
central fossae of upper molars.
Cusp to ridge: BC of lower 4&5 hits MMR of upper 4& 5 in
centric occlusion.
Cusp to sulcus: the triangular ridge of the MBC of upper
molar are accommodated to the BG of the lower molars.
Cusp to embrasure: the DBC of the maxillary molars lie in
the B. embrasure between lower molars.
Escapement spaces : the rounded surfaces of teeth make
escapement of food

66. 6) Facial and Lingual Relation of each Tooth in one Arch to its
antogonist in the opposing arch in centric occlusion:
Centric occlusion: it is the contact relation of upper and lower teeth
when they are in maximum inter cuspation and condyles are in
retruded unstrained position in glenoid fossa
• Each tooth contacts 2 teeth in the opposing arch except lower1 and
upper 8

67. • Each tooth have 2 antagonist, the loss of one still leaves one
antagonist remaining –keeps occlusal contact with opposing arch
and in arch relation by preventing displacement and elongation
• Permanency of the arch form depends on the mutual support of
teeth in contact with each other.
• When tooth is lost, adjoining teeth in same arch may, depending on
occlusal forces migrate in an effort to fill the void
• This migration disturbs the contact relationship in that vicinity and in
meantime tooth movement changes occlusal relation with antagonist
which result in hyper eruption (supraeruption) of tooth opposing the
space left by lost tooth.

68. 7)Occlusal contacts and intercuspal relations
between arches:
supporting cusp makes contact with a centric stop on the opposing
tooth .
e.g lingual cusp of maxillary posterior teeth and buccal cusp of
mandibular posterior teeth referred as supporting cusp
Centric stop: areas of occlusal contact that a supporting cusp make
with the opposing teeth in centric occlusion are centric stops.
therefore centric stops are areas of tooth that make
contact with opposing tooth in intercuspal position and contribute to
occlusal stability.

69. Cusp fossa and marginal ridge relation ;
• MLC of maxillary first molar occludes central fossa of mandibular
1stmolar
• DBC of 36 and 46 occludes in central fossa of maxillary 1st molar.
Hellman included 138 points in occlusal contacts to be considered as
ideal for occlusal contacts of ideal occlusion
ideal occlusion is used in orthodontics and restorative dentistry ,and
concept of 138 points has not been show necessary for occlusal
stability or function
Cusp fossa relationship is applicable in clinical dentistry

70. 8)Occlusal contacts and intercuspal relations of
the teeth:
Serves the relationship of supporting Cusp of
maxillary and mandibular 1s molar in lateral
protrusive movement.
Movement away from centric and eccentric
movement.
• lateral ,lateral protrusive, protrusive and
retrusive movements
• lateral ,lateral protrusive may be either to the
right or to the left
Lateral movements:
working and non working side (balancing
side in complete denture)

71. Tooth guidance :
• contact relation in lateral movement. There are
of relation ,group function, cuspid disocclusion only
or combination of canine , premolar and molar
• Group function refer to multiple contacts in lateral
and eccentric mandibular movements
• Canine guidance :in lateral movement, the canine in
upper and lower arch is in contact ,however
teeth on working and non working side are in
disocclusion.
• Incisal Guidance: contact of teeth in protrusive
movement
• Condylar and neuromuscular guidance

72. • Neurobehavioral aspect of occlusion :
• Relate to function(chewing, sucking
,swallowing, speech, respiration ) and
parafunction ( bruxism,clenching , grinding) of
the stomatognathic system.
• The co-ordination of occlusal contacts, jaw
motion and tongue movements during
mastication requires control from teeth and
Supporting structures ,TMJ, masticatory
muscles higher centers in CNS

73. •THANK YOU