University of Babylon Orthodontic
College of Dentistry
4th stage Dr. Lamis Khidher Mohammed
Lec.1,2 Introduction to Orthodontics
Orthodontics:
‘Ortho’ means correction of irregularity and ‘Dontics’ means teeth, so orthodontics correction irregularities of teeth.
More generally, 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 the teeth and the function of associated organs.
Definition of Occlusion:
Occlusion is defined as a manner in which the upper and lower teeth intercuspate between each other in all mandibular positions and movements. There are three types occlusion:
Ideal occlusion: is a hypothetical concept based on anatomy of the teeth. It’s rarely if ever found in natural. However, it’s provides a standard by which other occlusion can be judged.
Normal occlusion: is an occlusion within the accepted deviation of the ideal, i.e. with minor variation in the alignment of the teeth which are not of esthetic or functional importance.
Six keys to normal occlusion in adult dentition (Andrews’s six keys)
Inorder to call the occlusion as normal occlusion , it should have the following six keys:-
1. Molar relationship: should be class I angle classification.
2. Correct crown angulations (mesiodistal tip of the crown), which is mesially.
3. Correct crown inclination (labiolingual or buccolingual torque), which is
Anterior teeth: labially
Upper Posterior teeth: lingually
Lower posterior teeth: more lingually
4. Absence of rotations.
5. Tight proximal contacts (spaces not present).
6. Flat occlusal plane or slightly curved.
Malocclusion: is an irregularity in the occlusion beyond the accepted range of normal. However, there is a wide range of variation between individual and races. The fact that an individual has a malocclusion is not itself a justification for treatment, only if it is certain that the patient will benefit, esthetically or functionally, and only if the patient is suitable and willing to undergo treatment, should orthodontic intervention be considered.
The Malocclusions may be associated with one or more of the following:-
Malposition of individual teeth
Malrelationship of the dental arches.
Malposition of individual teeth:-
A tooth may occupy a position other than normal by being:
1. Tipped :-the tooth apex is normally placed but the crown is incorrectly positioned. Teeth may be tipped laterally (termed angulation) or may be tipped labiopalatally (termed inclination).
2. Displaced :- both apex and crown are incorrectly positioned.
3. Rotated :- the tooth is rotated around its long axis.
4. Infraocclusion :- the tooth has not reached the occlusal level.
5. Supraocclusion :-the tooth has erupted past the occlusal level.
6. Transposed:- two teeth have reversed their positions; an example of this might be an upper canine and first premolar.
The aims of orthodontic treatment
1. The improvement of facial and dental esthetic.
2. The alignment of the teeth to eliminate stagnation areas.
3. The elimination of premature contact which gives rises to mandibular displacement and may cause later muscle or joint pain.
4. The elimination of traumatic irregularities of the teeth.
5. The alignment of prominent which are liable to be damaged.
6. The alignment of irregular teeth prior to bridge work, crowns or partial dentures.
Orthodontic terms
Overjet:
It’s the horizontal distance between the upper and lower incisors in occlusion, measured at the tip of incisors. It’s of four types:
1. Normal overjet: it is 2-4 mm.
2. Excessive overjet: it is increased overjet being more than 4mm.
3. Edge to edge occlusion: it is occlusion of the upper and lower incisal edges without overlap (overjet 0 or less).
4. Reverse overjet: it is decrease overjet less than 0 mm.
Overbite:
It is the vertical distance between the tips of the upper and lower incisors in occlusion(the amount of overlapping of the upper central incisor to the lower central incisor in occlusion). It of four general types:
1. Normal overbite: it is 1-3 mm.
2. Anterior open bite: it is decrease overbite with absence of overlap between opposing incisors being less than 0 mm. it is either anterior openbite or posterior openbite.
3. Edge to edge occlusion: it is occlusion of the upper and lower incisal edges with 0 mm overbite.
4. Deep bite: it is increased overbite being more than 3 mm. it may be:
a) Incomplete: when the lower incisal edge dose not touch any opposing tissue.
b) Complete: when the lower incisal edge occlude with the palatal soft tissue or the palatal aspects of the opposing upper incisors being either:
1. Traumatic:- when the upper incisors are proclined and the lower incisors cause trauma of the palatal soft tissue.
2. Bitraumatic:- when the upper incisors are retroclined and the lower incisors cause trauma of the palatal soft tissue and the upper incisors cause trauma of lower labial soft tissue.
Crossbite:
It is when the upper tooth or teeth lie lingual to their opposing lower teeth. It’s generally of two types:
1. Anterior Crossbite: involving one or more incisors or canines. It may be associated with anterior mandibular displacement.
2. Posterior Crossbite: involving one or more premolar or molar posterior crossbite may be associated with lateral mandibular displacement. It is of two types (according to mandibular teeth):
a. Buccal crossbite: in which a buccal cusp of a mandibular tooth lies buccal to the maximum height of the buccal cusp of an opposing maxillary tooth.
b. Scissors bite (lingual crossbite) in which a buccal cusp of a mandibular tooth lies lingual to the maximum height of a lingual cusp of an opposing maxillary tooth.
Buccal Posterior crossbite may be:
1. Bilateral buccal posterior crossbite :- it affecting both sides without mandibular displacement, it is usually caused the basal arch of the upper jaw being narrower than that of the lower jaw. Commonly seen in subject with class III skeletal relationship, either because of a positional discrepancy or a size discrepancy between the jaws. It’s a symmetrical condition, and the mandibular path of closure from rest to occlusion usually occurs without lateral deviation.
2. Unilateral buccal posterior crossbite :-it affecting one sides, this may be:-
a. False unilateral buccal posterior crossbite: associated with lateral mandibular displacement either to the left or right usually noticed by a midline shift.
b. True unilateral buccal posterior crossbite: usually found in adults after growth in condyles eliminates the mandibular shift.
Space discrepancy
It is define as the difference between the space needed in dental arch and the available space in that arch and is either crowding or spacing caused by an altered tooth / tissue ratio.
Space discrepancy (crowding or spacing) may be mild, moderate or severe. It may be localized to the anterior or posterior region or may affect the entire arch.
a) Crowding: is the lack of space in the dental arch associated with rotation or displacement of teeth.
b) Spacing: is the presence of extra space in the dental arch associated with spaces between the teeth, and if present in the midline called a median diastema.
Midline shift: It is the lack of coincidence between the lower and upper dental midline. A midline shift of 0.5mm may be considered as normal. It may involve lack of coincidence between the facial midline with the lower and/or upper dental midline.
Classification of malocclusion
1-Angle s classification (molar relationship):-
Angle classified occlusion according to the molar relationship and this remains the most internationally recognized classification of malocclusion. When looking at ideal occlusion, Angle found that the mesiobuccal cusp of the upper first permanent molar should occlude with the sulcus between the mesial and distal buccal cusps of the lower first permanent molar. He therefore based his classification of occlusion on this relative mesiodistal position as follow:-
1. Class I occlusion: Normal anteroposterior relationship of the maxillary and mandibular dental arches, in which the mesiobuccal cusp of the upper first permanent molar occlude with the sulcus between the mesial and distal buccal cusps of the lower first permanent molar.
2. Class II occlusion: The mandibular arch being retruded in relation to the maxillary dental arch, in which the mesiobuccal cusp of the upper first permanent molar occlude mesially (anteriorly) to the sulcus between the mesial and distal buccal cusps of the lower first permanent molar ;This was either:
a) division1: which associated with proclined maxillary central incisors and increased overjet, or
b) division2: which associated with retroclined maxillary central incisors and normal or decreased overjet.
3. Class III occlusion: The mandibular arch being protruded in relation to the maxillary dental arch, in which the mesiobuccal cusp of the upper first permanent molar occlude distally (posteriorly) to the sulcus between the mesial and distal buccal cusps of the lower first permanent molar ;This was either:
a) Postural: associated with forward mandibular displacement, or
b) True: not associated with forward mandibular displacement.
2-Canine classification(canine relationship):
1- Class I canine relationship: When the upper canine occludes in the embrasure between lower canine and the first premolar, (at the same time mesiobuccal cusp tip of upper first molar occluded in the buccal groove of lower first molar).
2-Class II canine relationship: When the upper canine occludes anterior to the embrasure between lower canine and the first premolar.
3-Class III canine relationship: When the upper canine occludes posterior to the embrasure between lower canine and the first premolar.
3-Incisor classification(incisor relationship):
The incisor classification is considered simpler. It was adopted by the British Standards Institute in 1983, and is based upon the relationship of the lower incisor edges and the cingulum plateau of the maxillary central incisors.
1-Class I incisor relationship: The mandibular incisor edges occlude with or lie immediately below the cingulum plateau of the maxillary central incisors.
2-Class 11 incisor relationship: The mandibular incisor edges lie posterior to the cingulum plateau of the maxillary central incisors, which is either
a. Division 1. The maxillary central incisors are proclined or of average inclination and there is an increased overjet.
b. Division 2. The maxillary central incisors are retroclined; the overjet is normally minimum, but may be decreased.
3-Class III incisor relationship: The mandibular incisor edges lie anterior to the cingulum plateau of the upper central incisors; the overjet is reduced or reversed.
Orthodontic tooth movement
Orthodontic tooth movement :- is defined as the biological reaction of the teeth and their associated supporting structures to applied forces produced by orthodontic appliances (wires, brackets, elastics, etc.).
Types of orthodontic tooth movement
1-Tipping Movement: is the movement of the crown of the tooth more than the root, the crown moves in the direction of the applied force and the apex in the opposite direction.
2- Translation (bodily) Movement: it is the movement of the crown and apex of the tooth equal distance in the same direction of the applied force.
3-Root Movement (up righting and torqueing): it is controlled movement of the apices of teeth. It is achieved by keeping the crown of a tooth stationary and applying a moment of force to move the root only. Mesial or distal movement of apices is referred to as up righting, while labial or palatal movement of the apices is referred to as torqueing .
4-Rotation: it is the rotation of teeth around their long axes with the applied force .
5-Extrusion: movement of the teeth along their long axes outside the socket.
6-Intrusion: movement of the teeth along their long axes inside the socket.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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