Ortho 5.PDF - Malocclusion Terminology & Classification

# Terminology and Classification of Malocclusion ## Angle's Classification (1899) - **Class 1:** Normal occlusion - **Class II Division 1:** Upper incisors are proclined. Excessive overjet and deep bite. - **Class II Division 2:** Upper incisors are retroclined and may be overlapped by the latera...

# Terminology and Classification of Malocclusion ## Angle's Classification (1899) - **Class 1:** Normal occlusion - **Class II Division 1:** Upper incisors are proclined. Excessive overjet and deep bite. - **Class II Division 2:** Upper incisors are retroclined and may be overlapped by the lateral incisors. Deep bite. - **Class III:** The mesio-buccal cusp of the upper first permanent molar occludes in the embrasure between lower first and second permanent molars. The lower dental arch is in mesial relation to the upper arch by one unit or less. ## Types of Malocclusion ### Intra-arch Malocclusion - **Tipping:** The crown moves in one direction and the root moves in the opposite direction. - Labial tipping: Crown tilts towards the lips. - Lingual tipping: Crown tilts towards the tongue. - Medial tipping: Crown tilts towards the midline. - Distal tipping: Crown tilts away from the midline. - **Displacement:** The crown and the root move in the same direction with the long axis parallel to the original one. - Labial displacement: Crown and root move towards the lips. - Lingual displacement: Crown and root move towards the tongue. - Medial displacement: Crown and root move towards the midline. - Distal displacement: Crown and root move away from the midline. - **Rotation:** A tooth rotates around its long axis. - Mesiolingual/palatal rotation: The mesial aspect is turned towards the tongue. - Distolingual/palatal rotation: The distal aspect is turned towards the tongue. - **Supraocclusion:** The tooth passes the line of occlusion (overerupted). - **Infraocclusion:** The tooth does not reach the line of occlusion (not sufficiently erupted). - **Crowding (imbrication):** Teeth are not arranged within the dental arch due to lack of space. - **Transposition:** Abnormal order of teeth. - **Perversion:** A tooth that is totally misplaced or impacted, for example, a maxillary canine erupting in the nasal fossa. ### Inter-arch Malocclusion - **Sagittal Plane Malocclusions** - **Pre-normal Occlusion:** The mandibular arch is anteriorly placed in centric occlusion. - **Post-normal Occlusion:** The mandibular arch is posteriorly placed in centric occlusion. - **Overjet:** The horizontal overlap of the incisors. It is the distance between the labial aspects of the lower incisors and the lingual aspects of the upper incisors when the arches are in centric occlusion. - **Normal Overjet:** 2-3 mm. - **Increased Overjet:** More than 3 mm. - **Reduced Overjet:** Less than 2 mm. - **Negative or Reverse Overjet:** The lower incisors are ahead of the upper incisors causing anterior cross bite. - **Vertical Plane Malocclusions** - **Deep Bite:** Excessive vertical overlap between the maxillary and mandibular anteriors. Normal overbite: The upper anterior teeth should cover 1/3 of the labial surface of the lower anterior teeth when the teeth are brought into centric occlusion. - **Open Bite:** Lack of vertical overlap when the teeth are in occlusion. It could be in the anterior region or posterior region. - **Transverse Plane Malocclusions** - **Posterior Cross Bite:** - **Normal Buccolingual Relation:** The cusp tips of the lower posterior teeth interdigitate with the central fossae of the upper posterior teeth. - **Maxillary Lingual (or palatal) Crossbite:** The upper molars are lingual to their normal position. - **Maxillary Buccal Crossbite:** The upper molars are buccal to their normal position. - **Transverse Occlusal Deviation:** Can be either unilateral or bilateral. - **Scissors Bite (Brodie syndrome):** Total maxillary buccal or mandibular lingual cross bite, with the mandibular teeth completely contained within the maxillary teeth when the teeth are in centric occlusion. ### Skeletal Malocclusion - Includes defects in the underlying skeletal structure due to abnormalities in size, position or relationship between the jaws. - Sagittal Abnormalities: Prognathism, retrognathism, or combinations. - Transverse Abnormalities: Narrowing or widening of jaws causes crossbites. - Vertical Abnormalities: Variation affects lower facial height. ## Classification of Malocclusion **Objectives of Classification:** - Grouping of orthodontic problems. - Documentation of problems. - Location of problems to be treated. - Diagnosis & treatment plan. - Develop a strategy to manage similar cases. - Comparison of different types of malocclusions. - Facilitate communication. - Used for epidemiological studies. - Assessment of treatment effects of orthodontic appliances. ## Systems of Classification of Malocclusion - Angle's Classification - Lischer's modification of Angle's classification - Dewey's modification of Angle's classification - Skeletal Classification - Incisor Classification - Canine Classification - Simon's Classification - Bennett's Classification - Classification by body-build ## Angle's Classification - Introduced by Edward Angle in 1899. - Based on the anteroposterior relationship of the teeth with each other. - The maxillary first permanent molar is considered to be the key of occlusion and Angle stated that the position of the maxillary first permanent molar is relatively constant. - Angle considered the maxilla to be a fixed structure due to its attachment to the base of the skull and any defect would be due to the movable mandible. - Angle used the maxillary first permanent molar as the reference to his classification as its mesiobuccal root lies beneath the key ridge (the inferior portion of the zygomatic process of the maxilla) which is considered to be a fixed point in the maxilla that could not be in faulty position. - He classified malocclusion into three classes giving them the Roman numbers I, II, and III. Arabic numbers (1 and 2) were given to divisions. Unilateral deviations were termed subdivisions. ### Class I Malocclusion - The mesio-buccal cusp of the upper first permanent molar occludes into the buccal developmental groove of the lower first permanent molar. The anteroposterior relation is normal. - Abnormalities: - Local abnormalities: Rotation, labial or lingual inclination. - Vertical or transverse abnormality: Deep bite, open bite, posterior cross bite. - Disproportion in size between apical base and teeth: Crowding, spacing. - No divisions or subdivisions ### Class II Malocclusion - The mesio-buccal cusp of the upper first permanent molar occludes in the embrasure between lower first permanent molar and lower second premolar. - The lower dental arch is in distal relation to the upper arch by one unit or less (the unit is equal to the width of the premolar or half the width of the molar). - Class II has 2 divisions: - Class II division 1: Class II on one side and Class I on the other side. - Class II division 2: Class II on both sides #### Class II Division 1 - Upper incisors are proclined. - Excessive overjet and deep bite. #### Class II Division 2 - Upper incisors are retroclined and may be overlapped by the lateral incisors. - Deep bite. ### Class III Malocclusion - The mesio-buccal cusp of the upper first permanent molar occludes in the embrasure between lower first and second permanent molars. - The lower dental arch is in mesial relation to the upper arch by one unit or less. - Class III subdivision: Class III on one side and Class I on the opposite side. - The lower incisors may show edge to edge relation, anterior cross bite or may be crowded and bite lingually to the maxillary incisors. Sometimes, the lower incisors are spaced and found labial to the maxillary incisors when the tongue plays a role in mandibular prognathism. - Posterior crossbite could be involved, and deep bite or open bite could be seen. - Class III may be true or pseudo. #### True Class III - **Lateral Cephalometric X-ray:** The condyle is inside the glenoid fossa. - The mandible cannot be retracted by manual pressure. - Due to maxillary retrusion, mandibular protrusion or both. #### Pseudo Class III - **Lateral Cephalometric X-ray:** The condyle is anterior to the glenoid fossa. - The mandible can be retracted by manual pressure. - Due to early loss of upper deciduous molars or cuspal interference to reach a position of comfort. ## Incisor Relation **Class II Division 1** - Edge to edge - Normally placed lower incisors behind the upper incisors but the lower incisors are crowded and in linguo-version. **Class II Division 2** - Anterior cross bite **Class III** - Anterior cross bite