Terminology in Orthodontics

Terminology in Orthodontics
Copyright by Department of Orthodontics
University of Dental Medicine, Yangon
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1. TERMINOLOGY

Prof. Dr.Hla Hla Yee

2. Orthodontics
Orthodontics has been defined as that
branch of dentistry concerned with
growth of the face, development of the
dentition, and prevention and correction
of occlusal anomalies.

3. Overjet
 is defined as the horizontal overlap of the incisors. ( or )
The relationship between upper and lower incisors in the
horizontal plane.
Normally the incisors are in contact with the upper incisors
ahead of the lower by only the thickness of the upper
edges ie 2-3 mm overjet is the normal relationship.
Increased overjet - more than 3 mm.
Reduced overject - less than 2 mm
Negative or reverse overjet – the lower incisors are ahead
of the upper incisors.

4. Overjet is measured from the labial surface of the lower
incisor to the labial surface of the upper incisor.
Record the distance for both central incisors.
Get used to making the measurement in the middle of
each incisal edge, keeping the ruler parallel to the
occlusal plane.

This will overcome the local effect of the incisors rotation
and reduce measurement error that may be caused by
variation in head position.
OJ is recorded to the nearest millimeter.

6. Normal
OJ, OB
Increased
OJ,OB
Crossbite
Reversed
OJ
Increased OB
Reduced OJ

7. Normal overjet , overbite

8. Increased OJ , OB

9. Reversed OJ
Crossbite

10. Overbite
is defined as vertical overlap of the incisors. ( or )
The overlap of the lower incisors by the upper incisor in
the vertical plane.
Normally the lower incisor edges contact the lingual
surface of the upper incisors at or above the cingulum.
Normal overbite – 2 - 3 mm
Increased or Deep bite – more than 3 mm
Reduced overbite – less than 2 mm.

11. Complete overbite –
 An overbite in which the lower incisors contact
either the upper incisors or the palatal mucosa.
Incomplete overbite –
 An overbite in which the lower incisors contact
neither the upper incisors nor the palatal
mucosa.

12. Increased and complete overbite

13. Incomplete overbite

14. 1 1
Retroclined
Deepbite
Reduced OJ

15. Increased
& Complete
OB
Increased &
Incomplete OB
Reduced
OB
AOB

16. Anterior openbite
The lower incisors are not overlapped in the
vertical plane by the upper incisors and do
not occlude with them. (or )
When the patient is viewed from the front and
the teeth are in occlusion, a space can be
seen between the upper and lower incisor
edges.

17. Anterior Open Bite

18. Crossbite - A deviation from the normal bucco-
lingual relationship; may be anterior / posterior / or
unilateral / bilateral .
Anterior crossbite –
 This can either be anterior in which case one or
more upper incisors are in lingual occlusion the
lower incisors.

Under bite –
the lower front teeth protrude beyond the upper
teeth .
An underbite is also known as an anterior
crossbite.

19. Crossbite at Upper Left Central
Incisor

20. Anterior crossbite or under bite

21. Posterior crossbite -A transverse
discrepancy in arch relationship .
The lower arch is wider than the upper so that
the buccal cusps of the lower teeth occlude
outside the buccal cusps of the
corresponding upper teeth.

22. A-C Frontal and lateral views of an ideal occlusion.

23. Buccal Crossbite

24. Posterior cross bite

25. 
Buccal crossbite
Buccal cusps of lower premolars or molars occlude buccally
to the buccal cusps of the upper premolars or molars.
Lingual crossbite
Buccal cusps of lower molars occlude lingual to the lingual
cusps of the upper molars.

Scissors bite
A lingual crossbite at the lower teeth.
One or more upper buccal segment teeth occlude entirely
buccal to the lower arch teeth.

26. Mandibular buccal crossbite.

27. Mandibular lingual crossbite / Scissors bite

28. Occlusion
Any contact between teeth of opposing dental
arches, usually referring to contact between the
occlusal surfaces.
Ideal occlusion
A theoretical occlusion based on the morphology
of the teeth. (or)
The ideal relationship of the teeth can be defined
in terms of static (or morphological) and functional
occlusion.

29. Ideal occlusion

30. Normal occlusion
An occlusion which satisfies the requirements of
function and aesthetics but in which there are
minor irregularities of individual teeth.

31. Malocclusion
can be defined as an appreciable deviation
from the ideal that may be considered
aesthetically or functionally unsatisfactory.
(or)
An occlusion in which there is a malrelationship
between the arches in any of the planes of space or
in which there are anomalies in tooth position beyond
the limits of normal.

32. Malocclusion

33. Malocclusion
(Posterior cross bite)

35. Centric occlusion
A position of maximal intercuspation which is a
position of centric relation.
It is the occlusion of the teeth where the mandible
is in centric relation
A position of maximum intercuspation when the
jaws are in centric relation.

36. Centric relation
It has been defined as the relationship of the mandible
to the cranium that exists when the condyles articulate
with the thinnest avascular portion of their respective
discs in their most anterior – superior position against
the slopes of the articular eminences, regardless of
tooth contact.
(or)

37. Retruded contact position (RCP) or centric
relation (CR)
is the position of the mandible in relation to the
maxilla with the condylar head in its terminal hinge
axis (uppermost and foremost within the glenoid
fossa).

38. Fig : TMJ of a completely
dentate 18 years old man .
The sketch shows the
normal topographical
situation .

39. Habit posture
A postured position of the mandible habitually
maintained either to facilitate the production of an
anterior oral seal or for aesthetic reasons.
Deviation of the mandible
a sagittal movement of the mandible during closure
from a habit posture to a position of centric occlusion.
When the mandible is habitually postured forwards
there may be an upwards and backwards path of
closure into centric occlusion, rather than simple hinge
closure.

40. Displacement of the mandible
When closing from the rest position, the mandible
displaces (either laterally or anteriorly) to avoid a
premature contact.
A sagittal or lateral displacement of the mandible as a
result of a premature contact.
Mandibular displacement are caused by premature
contacts of the teeth that enforce a shift of the mandible to
obtain a position of maximum occlusion.

41. With a lateral displacement such a is produced by a
unilateral crossbite, the position of maximal
intercuspation is not one of centric relation.
An anterior displacemet may be cause by one or more
instanding upper incisors.
When all the incisors are instanding, the displacement is
often associated with overclosure of the mandible
because the control of muscular contraction is disturbed
and the occlusion is established with an overclosd
position of the mandible.

42. Posterior mandibular displacements are quite rare
in an unmutilated dentition but can be found in
Class II division 2 cases where posterior teeth
have been lost.
Mandibular displacements are associated with
quite severe disruption of the pattern of activity of
the muscles of mastication, which will often lead to
pain and dysfunction in the long term.
Treatment to eliminate the displacement is
important

43. Premature contact
An occlusal contact which occurs during
the centric path of closure of the mandible
before maximal cuspal occlusion is
reached.
This may result in either displacement of
the mandible or movement of the tooth or
both.

44. Anterior
displacement
Premature contact

45. Lateral displacement

46. Canine guidance
 is present when contact is maintained on the working
side canine teeth during lateral excursion of the mandible.

47. Group function
 is present when contacts are maintained between
several teeth on the working side during lateral excursion
of the mandible.

48. Line of occlusion
The line of occlusion is a smooth ( catenary ) curve
passing through the central fossa of each upper molar
an across the cingulum of the upper canine and incisor
teeth.
The same line runs along the buccal cusps and incisal
edges of the lower teeth, thus specifying the occlusal as
well as interarch relationships once the molar position is
established.

50. Line of occlusion

52. Alignment
Angulation
Mesio-distal tip of tooth within the dental
arch.
Incisor angulation
An expression of the degree of tip in the
mesiodistal plane.

53. Distally angulated
3
33

54. Inclination
The labio-palatal tip of a tooth within the
dental arch.
Incisor inclination
An expression of the degree of tip in the
labiopalatal plane.

55. Frankfort horizontal plane
FHP
Orbitale Porion

59. Procline
The upper and lower incisors are proclined
labialy to a greater degree than normal.
The relationship of long axis of the upper central
incisors to FHP.
The mean value is 110
Proclined upper incisors - > 110
Retroclined upper incisors - < 110
.
.
.

60. Proclined upper incisors

61. The relationship of long axis of lower
incisors. ( line passing through the incisal
edge and the apex of the root of mandibular
central incisors ) to mandibular plane.
The mean value is 90
Proclined lower incisor - > 90
retroclined lower incisor - < 90
.
.
.

62. Retroclined
The upper and lower incisors are incline
palatally / lingually to a greater extent than
normal.
Proclination
The labial tipping of incisor teeth often
together with supporting dento-alveolus.

63. Retroclined

64. Palatally inclined
Lingually inclined

65. Bimaxillary dentoalveolar protrusion
meaning simply that in both jaws the teeth that
protude.
Bimaxillary protrusion
a simpler term but a misnomer since it is not the
jaws but the teeth that protrude.
( Physical anthropologists use bimaxillary
protrusion to describe faces in which both jaws are
prorelative to the cranium, such a face would have
an anteriorly divergent profile if jaw sizes were
proportional. )

66. Bimaxillary dentoalveolar protrusion

67. Imbrication
The overlapping of incisor teeth in the
same direction.
Rotation
Rotation of teeth around their long axis.
Mesiolabially rotated – if the mesial aspect
is out of the line of the arch .
Distopallatally rotated_if the distal aspect
was palatally positioned.

68. Imbrication

69. Rotated central incisors

70. 1 1
Rotation

73. Supernumerary teeth
Teeth in excess of the usual number – usually of
abnormal form.
Supplemental teeth
Supernumerary teeth, resembling the teeth of the
normal series.
Odontome
An abnormal mass of calcified dental tissue.

75. Mesiodens (mesiodentes)

76. Tuberculate (multicusped)
- barrel shape

77. Odontome

78. Macrodontia
Abnormally large teeth.
Microdontia
Abnormally small teeth, often the last of the
series.

79.  Macrodontia Microdontia

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80. Diastema
A space between certain teeth, often maxillary
central incisors.
Crowding
When the size of the dentition is greater than
the space available to accommodate the teeth
in good general alignment then crowding may
be said to occur.

81. Spacing

82. Median Diastema

83. Actual crowding

84. Potential crowding

85. Actual crowdig (Clinically evident crowding )
the incisor teeth remain upright and well positioned
over the basal bone of the maxilla and the mandible
but the teeth are rotated or tip labially or lingually.
Potential crowding
The crowded teeth align themselves at the expense of
lip, displacing the lip forward and interfering with the lip
closure. The incisors are proclined and off the basal
bone.

86. Tooth size – Jaw size discrepancy
Disproportion between tooth – size and arch size.
It is usually manifest as crowding but occasionally
there is generalized spacing.
Tooth size is under direct genetic control .
the size of the dental arches depends on :

skeletal base size and

the soft tissue morphology and

activity;
as such the dental arch is under the influence of
both environmental and genetic factors.

87. Dento-alveolar compensation
The position of the teeth has
compensated for the underlying skeletal
pattern, so that the occlusal relationship
between the arches is less severe.