Orthodontics Lecture Notes PDF

Contents Aims of orthodontics Classification of malocclusion Etiology of malocclusion Orthodontic tooth movements  Aims of orthodontics Functional Structural Esthetic efficiency balance harmony.  Functional efficiency Function...

Contents Aims of orthodontics Classification of malocclusion Etiology of malocclusion Orthodontic tooth movements  Aims of orthodontics Functional Structural Esthetic efficiency balance harmony.  Functional efficiency Function mastication Teeth Surrounding structure  Structural Balance Skeletal structures Teeth Soft tissue envelop  Branches of Orthodontics Preventive Interceptive Corrective orthodontics orthodontics orthodontics.  Timing of orthodontic intervention Deciduous Dentition Early Mixed Dentition Late Mixed Dentition/Early Permanent Dentition Parental education monitoring of shedding Most corrective orthodontic timetable treatments Care of deciduous dentition serial extraction growth modification Space maintenance space Surgical treatment maintenance Elimination of abnormal oral growth modification habits. corrective orthodontic procedures  Classification of malocclusion Intra-arch Inter-arch malocclusions malocclusions Intra-arch malocclusions Rotation Transposition Infra/Supra Abnormal version Position  Intra-arch malocclusions Buccal Lingual Buccal Lingual Displacement Displacement Inclination Inclination Mesial Distal Mesial Distal Displacement Displacement Inclination Inclination  Inter-arch malocclusions Transverse Sagittal Plane Vertical Plane Plane Malocclusions Malocclusions Malocclusions  INCISOR RELATIONSHIP Class I Incisor Class II Incisor Class III Incisor Relationship Relationship Relationship  CANINE RELATIONSHIP Class I Canine Class II Canine Class III Canine Relationship Relationship Relationship  MOLAR RELATIONSHIP Class I Molar Class II Molar Class III Molar Relationship Relationship Relationship  ANGLE’S CLASSIFICATION OF MALOCCLUSION Angle’s Class I Angle’s Class II Angle’s Class III Malocclusion Malocclusion Malocclusion  MALOCCLUSION Malocclusion may be defined as "A condition where there is departure from the molar relation of the teeth to other teeth in the same dental arch and /or teeth in the opposing arch". The term "malocclusion" was introduced by Guiford (1889) presenting a hazard to the individual's wellbeing. (The prefix "mal" means bad)  malocclusion of the teeth may be associated with one or more of the following conditions: 1. Malpositions of individual teeth in aches and jaws which are themselves normally related to one another. 2. Malrelations of dental arches to one another upon bony bases which may themselves be normally related. 3. Skeletal morphology unfavorable for the production of normal occlusion i.e. malrelation of dental bases.  Malpositions of individual teeth Lischer used the suffix "version" to identify the malposition of teeth in relation to the line of occlusion. In normal occlusion, the line of occlusion passes through the central fossae and along the cingulae of the maxillary teeth, and the buccal cusps and incisal edges of the mandibular teeth. Adding the suffix "version" to a word indicates the direction of the deviation from the normal position. 1. Mesioversion: Mesial to the normal position. A. Mesial inclination: The crown is titled mesially. B. Mesial displacement: The tooth is bodily displaced mesially. 2. Distoversion: Distal to the normal position. 3. Linguoversion: Lingual to the normal position. 4. Labioversion or buccoversion: Toward the lip or cheek. 5. Infraversion: Away from the line of occlusion. 6. Supraversion: Extended past the line of occlusion i.e. below in the maxilla and above in the mandible. 7. Torsioversion: Rotated on its long axis eg. Mesiolingual rotation: mesial aspect is turned towards the tongue. 8. Transversion: Wrong order in the arch, transposition. 9. Imbrication: Teeth which are irregularly placed in the arch due lack of space.  Malrelation of the dental arches These terms are used to describe variations from the normal relations of the dental arches to one another in horizontal plane (anterioposterior and lateral) and vertical plane: A) Anteroposterior B) Lateral C) Vertical  Anteroposterior 1. Postnormal occlusion Where the lower dental arch lies too far distally in relation on he upper arch when the teeth are closed in centric occlusion. 2. Prenormal occlusion This is where the lower dental arch is in advance to the upper when the teeth are closed in centric occlusion and the condyles are in their normal position within the glenoid fossae. 3. Postural prenormal occlusion This term when the lower arch is postured forwards into a prenormal relationship i.e. a bite of accommodation. 4. Overbite It is the distance between the labial aspect of the lower incisors and the palatal aspect of the upper incisors when the arches in centric occlusion.  B) Lateral 1. Cross bite: This means that the buccal cusps of the maxillary buccal teeth occlude with the central fossae of the mandibular teeth. Occasionally the maxillary teeth are completely inside or outside their mandibular opponents. It may be unilateral or bilateral. Sometimes the term is used to describe lingual occlusion of one or more maxillary incisor teeth (anteroposterior). In case of bilateral cross bite the etiology is usally skeletal i.e. one basal bone is too narrow or too wide for the other one.  In the unilateral cross bite the etiology is usually soft tissue behavior but may also be due to a slight skeletal discrepancy. Scissors bite which indicates total maxillary buccal (or mandibular lingual) crossbite, with the mandibular teeth completely contained within the maxillary teeth when the teeth completely are in centric occlusion.  C) Vertical With normal overbite the palatal surface of the upper incisors overlap the incisal third of the labial surfaces of the lower incisors. Variations in degree of overbite are referred to as: 1. Excessive overbite (deep): This abnormality may be produced by the following: A. Abnormal axial inclination of upper and/or lower incisors giving loss of normal centric stops and this will lead to an increased vertical development of the dentoalveolar structures i.e. over- eruption of the lower incisors. B. Abnormal dental base relationship (with normal or abnormal axial inclination of incisors). 2. Open bite: This term is applied when there is localized absence of occlusion while the remaining teeth are in occlusion. Open bite is seen most frequently in the anterior part of the mouth although posterior open bites are encountered also. Open bite may be due to abnormal soft tissue behavior patterns preventing the dentoalveolar structures from closing the intermaxillary space e.g. thump, finger and tongue.  Open bite may result from abnormal skeletal pattern. As vertical development of the dentoalveolar structures will reach the maximum without closing the intermaxillary space, because of high Frankfort- mandibular plane angle. These cases often have a class III dental base relationship and are associated with abnormal mandible. Open bite is quit common in cleft palate cases owing to lack of anteroposterior development of the maxilla.  Skeletal pattern Certain conditions may affect the shape and size of either or both jaws and also their relationship not only to each other in all dimensions but also to the rest of the skull. For example the mandible may be underdeveloped or a cleft may affect the structure of the maxilla. Accordingly the development of normal occlusion is highly improbable.  The term "skeletal pattern" was first used by Ballard (1948) and is commonly applied to describe the anteroposterior relationship of the apical base when the jaws are closed and the teeth are full occlusion. The skeletal pattern can be assessed clinically and also from analyzing tracings of lateral skull radiographs.  Skeletal 1:- Where there is normal anteroposterior relationship of the apical bases, this is favorable for the production of satisfactory occlusion either by normal development or by orthodontic tooth movement. Skeletal 2:- Where the mandibular apical base is postnormal to the maxillary dental base (either due to maxillary protrusion, mandibular retrusion or both). Skeletal 3:- Where the mandibular apical base is pre normal relative to the maxillary dental base (either due to maxillary protrusion, mandibular retrusion or both). ANGLE'S CLASSIFICATION  Edward Angle brought in his classification based on the hypothesis the maxillary first permanent molar invariably is in a correct position, and is the "key to occlusion". His classification was based on the relationship of the lower to the upper teeth, dental arches and jaws in the anteroposterior plane and using the first permanent molar as his "key" teeth.  In 1899, Angle published his "classification of malocclusion", and employed the Roman numerals (I, II and III) to designate the three main classes of mesiodistal molar relationship. He assumed that the upper first permanent molars have a fixed relationship to both the maxillary base and the key ridge. He classified his malocclusion according to the relationship of the lower first permanent molar to the upper first permanent molar.  At the present time Angle's classification is used as a basis of the occlusion of the dento-alveolar structures alone and not as a comprehensive picture of the whole dentofacial complex plus skeletal pattern. It shows the anteroposterior relationship of the teeth themselves but is unreliable as a method of determining the relationship of the basal bones on which they lie.  When the first permanent molar is missing from the arch then the relationship has to be assessed from the canine or premolar (or deciduous molar) relationship. Still Angle's classification serves a useful purpose in differentiating clinical types especially if used in conjunction with a skeletal classification.  Angle’s Class I Malocclusion Molar relationship Class I Canine relationship Class I Incisor relationship Class I Spacing in arch May be present Additional features  Crowding  Spacing  Rotation  Missing tooth  Bimaxillary protrusion  Midline diastema  Angle’s Class II Malocclusion Angle’s Class II Division 1 Malocclusion Molar relationship Class II on right and left side of arch Canine relationship Class II on right and left side of arch Incisor relationship Class II division 1 incisor relationship Maxillary arch ‘V’ shape Maxillary anterior Proclined Overjet Increased Overbite Increased  Angle’s Class II Malocclusion Angle’s Class II Division 2 Malocclusion Molar relationship Class II on right and left side Canine relationship Class II on right and left side Incisor relationship Class II division 2 on right and left side Maxillary anterior Crowding Overjet Decreased Overbite Increased Maxillary arch U shaped  Angle’s Class III Malocclusion Molar relationship Class III Canine relationship Class III Incisor relationship Class III Overjet Reversed Mandibular arch Prognathic Maxillary arch Retrognathic  Pseudo Class III Malocclusion Angle’s class III pseudo malocclusion is characterized by class III molar relationship, which is mainly due to habit. It is also called as habitual or postural malocclusion.