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D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
Definitions
Orthodontics: “Ortho” means correction of irregularity and “dontics” means teeth, so
orthodontics means correction the irregularities of teeth.
According to American Board of Orthodontics “Orthodontics is that specific area of
dental practice that has as its responsibility the study and supervision of the growth and
the development of the dentition and its related anatomical structures from birth to dental
maturity, including all preventive and corrective procedures of dental irregularities
requiring the repositioning of teeth by functional or mechanical means to establish
normal occlusion and pleasing facial contours”.
Orthodontics: is that branch of dental science concerned with genetic variation,
development and growth of facial forms and the manner in which these factors affect the
occlusion of teeth and the function of associated organs.
Orthodontics: is that branch of dentistry concerned with prevention, interception and
correction of malocclusion and other abnormalities of the dento -facial region.
Occlusion
The relationship of the maxillary and mandibular teeth when the jaws are - Closed in
centric relation
There are three types of occlusion:
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
Ideal occlusion: is a hypothetical concept of an ideal arrangement of teeth based on
the anatomy of teeth combined with an ideal inter-arch relationship which result in
optimal esthetic, function and stability of dentition and supporting structures. It is rarely
if ever found in nature. However, it provides a standard by which other occlusion can be
judged.
Normal occlusion: is an occlusion which includes variation in tooth position and
relationship that diverge in minor way from the ideal. In general, these variations are not
of esthetic or functional importance.
Malocclusion: is an irregularity in the occlusion beyond the accepted range of normal.
Class I
Class III
Class II
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
The fact that an individual has a malocclusion is not itself a justification for
treatment, the orthodontic treatment should be considered only:
If the patient will benefit esthetically or functionally.
If the patient is suitable and willing to undergo the treatment.
The scope of orthodontic treatment:
•
•
•
Alteration in tooth position.
Alteration in skeletal pattern.
Alteration in soft tissue pattern.
The objectives (aims) of orthodontic treatment:
 The improvement of facial & dental esthetics which lead to improvement the
quality of life and Individual’s self –esteem( how positively the person feels about
himself), It reflects the patient’s desire to improve their social acceptability and
eliminate discrimination based on appearance, which can affect their quality of life
greatly
 Alignment of teeth in order to reduce the stagnation area, the presence of
stagnation areas makes the effective cleansing and brushing is difficult which
increase the risk for the development of dental caries.
 Alignment of teeth in order to reduce periodontal diseases, the malocclusion may
force one or more teeth to be squeezed buccally or lingually out of their investing
bone reducing periodontal support and traumatic occlusion may lead to increase
the loss of periodontal support.
 Alignment of anterior proclined teeth in order to reduce the possibility of fracture
or damage to the anterior teeth due to traumatic injury or accident.
 Alignment of teeth in order to improve masticatory function, patients with open
bites, markedly increased over jet (Class II) or reversed over jet (Class III) often
complain difficulties with eating particularly incising food.
 The elimination of premature contacts which give rise to mandibular displacement
and may cause later muscle or joint pain.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
 Orthodontic treatment of certain malocclusion which is related to speech problems
will result in speech improvement. (Not all cases of speech problem are caused by
malocclusion, sometimes there is a normal speech associated with sever anatomic
distortion).
 The alignment of irregular teeth prior to bridge work, crown or partial denture.
The six keys of normal occlusion
Six significant occlusal characteristics identified & first reported in 1972 by Lawrence
F. Andrews, These six keys were found to be consistently present in a collection of
120 models of teeth with natural excellent occlusion.
The criteria of the models included in this study:
 Teeth of selected models never had orthodontic treatment
 Teeth of selected models were straight and pleasing in appearance
 Had a bite which looked generally correct
1.
Class I Molar relationship (inter-arch relationship)
 The mesiobuccal cusp of the upper first molar should occlude in the groove
between the mesial and middle buccal cusp of the lower first molar.
 The distal surface of the distobuccal cusp of the upper first permanent
molar made contact and occluded with the mesial surface of the mesiobuccal
cusp of the lower second molar.
 The mesiopalatal cusp of the upper first molar should occlude in the central
fossa of the lower first molar.
 The premolars enjoy a cusp-embrasure relationship buccally, and a cusp
fossa relationship lingually. Maxillary canine has a cusp-embrasure
relationship with mandibular canine & 1st premolar.
D.U.C
Faculity of Dentistry
4th Grade
2.
Orthodontic
Dr. Ghufran Dhari
Lec.1
Crown angulation (Mesio-distal crown angulation)
 Crown angulation refers to angulation (or tip) of the facial long axis of the
crown.
 The degree of crown tip is the angle formed by the facial long axis of the
crown and a line perpendicular to the occlusal plane.
 A “+ reading" when the gingival portion of the facial long axis of the crown
is distal to the incisal portion.
 A “- reading" when the gingival portion of the facial long axis of the crown
is mesial to the incisal portion.
 For normal occlusion, the crown angulation is mesially, the gingival part
of the facial long axis of the crown must be distal to the incisal (occlusal)
part of the axis, It varied with each tooth type.
D.U.C
Faculity of Dentistry
4th Grade
3.
Orthodontic
Dr. Ghufran Dhari
Lec.1
Crown inclination (Labio-lingual or Bucco-lingual
inclination)
 Crown inclination refers to the labiolingual or buccolingual inclination of the
facial long axis of the crown.
 Crown inclination is determined by angle formed by a line perpendicular to the
occlusal plane and the facial long axis of the crown (as viewed from the mesial
or distal).
 In upper incisors, the crown inclination is labially, the gingival portion of the
crown’s labial surface is lingual to the incisal portion (positive inclination)
 In all other crowns, including lower incisors, the crown inclination is
lingually, the gingival portion of the labial or buccal surface is labial or buccal
to the incisal or occlusal portion. (negative inclination) with progressively
greater negative inclination exist in lower(canines, premolar and molars) when
compared with upper (canines, premolar and molars).
4. Rotations. There were no rotations.
D.U.C
Faculity of Dentistry
4th Grade
4.
Orthodontic
Dr. Ghufran Dhari
Lec.1
Spaces. There were no spaces; contact points were tight.
6. Occlusal plane. The plane of occlusion is measured from the most prominent
cusp of the lower second molar to the lower central incisor. The occlusal plane varied
from flat to a slight curve of Spee. The mandibular curve of spee should not be deeper
than 1.5mm.
Recently, the authors believe that the correct crown diameter (correct tooth size)
represents the 7th key to normal occlusion. This key had to be present in Andrew’s non
orthodontic study models.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
Overjet & Overbite
Overjet: is the horizontal distance between the upper and lower incisors in
occlusion, measured at the tip of upper incisor. Normally the upper incisors are in
front of the lower incisors in occlusion (2-4 mm).
It is dependent upon the inclination of incisors and the antero-posterior
relationship of the dental arches.
In most people, there is a positive overjet (2-4mm) in which the upper incisors are
in front of the lower incisors in occlusion. Sometimes the overjet may be zero in case of
edge-to-edge relationship, the overjet may be reversed (negative) in cases of class III.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
Edge to edge
Overbite: is the vertical distance between the tips of the upper and
lower incisors in occlusion. Normally, the tip of lower incisors contacts the middle third
of the palatal surface of the upper incisors in occlusion (2-4mm).
It is dependent upon the degree of vertical development of the anterior dento-alveolar
segment.
There may be excessive overbite (deep bite) more than 4 mm, or there may be no incisal
contact and the lower incisor edge is above the level of the upper incisal edge in
occlusion which is called incomplete overbite, or there may be no incisal contact and the
lower incisor edge is below the level of the upper incisal edge in occlusion which is
called anterior open bite.
D.U.C
Faculity of Dentistry
4th Grade
Open bite
Orthodontic
Normal
Dr. Ghufran Dhari
Lec.1
Deep bite
Note: Basal arches (skeletal bases) mean maxillary and mandibular bones,
while dental arches mean the teeth and their investing alveolar bone.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
Skeletal bases
Dental arches
Malocclusion
Malocclusion is an irregularity in the occlusion beyond the accepted range of normal. It
could be considered in the following groups:
A.Teeth: Malpositioning of individual tooh or groups of teeth in normally related
dental arches and jaws.
B.Dental arches: Malrelation of the dental arches to one another upon bony bases
which are themeselves normally related. The malrelation of the dental arches can take
place in all dimensions, antero-posteriorly, laterally and vertically.
Class II
Open bite
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
C.Dental bases (skeletal bases): The shape and the relation of the mandible to the
maxilla are unfavorable to the production of a normal occlusion.
Skeletal class II
Malocclusion
 Intra-arch problems: malpositions of individual tooth or group of teeth in the
same arch.
 Inter-arch problems: malrelation between the upper & lower dental arches.
Intra-arch problems
 Labioversion (buccoversion): A tooth that has assumed a position labial or
buccal to the normal position.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
 Lingoversion (palatoversion): A tooth that has assumed a position lingual or
palatal to the normal position.
 Mesioversion: A tooth that has assumed a position mesial to the normal
position.
 Distoversion: A tooth that has assumed a position distal to the normal position.
 Supraversion: Over-erupted above the level of occlusion.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
 Infraversion: Depressed below the level of occlusion, for example, primary
tooth that is submerged or ankylosed.
 Torsiversion: Turned or rotated tooth around its long axis, it could be:
 Mild: which is less than 90°
 Severe: which is more than 90°
 Transposition: interchange in the position of two adjacent teeth.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
 Impaction: occur when the eruption is completely blocked by other teeth due to
crowding. It tend to affect the last tooth erupt in each segment.
 Crowding: the irregularities of teeth due to inadequate space in the dental arch
for normal alignment.
 Spacing: Condition where there are gaps or spaces present between the teeth. It
could be either localized or generalized.
D.U.C
Faculity of Dentistry
4th Grade
Orthodontic
Dr. Ghufran Dhari
Lec.1
 Proclination: is term used to describe labial inclination (tilting) of anterior teeth
toward the lips.
 Retroclination: is term used to describe lingual inclination (tilting) of anterior
teeth.