Angle’s class III
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Introduction
Class III malocclusion represents a pre normalcy where the mandible is in a mesial relation to upper arch
In sagittal plane this occlusion is called Pre normal occlusion
According to Lischer’s modification of Angle’s classification this malocclusion is known as Mesio occlusion www.indiandentalacademy.com
According to Angle a Class III molar relationship refers to a condition where the mesio buccal cusp of permanent maxillary first molar occluding in the interdental space between the mandibular first and second molars.
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Etiology Heredity Age linked Functional factor and soft tissue - Tongue posture - Enlarged tonsils and naso respiratory difficulties - Excessive epi pharyngeal lymphoid tissue
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Occlusal forces created by abnormal eruption Pre mature loss of deciduous molars Lack of eruption of maxillary buccal segments Cleft lip and palate Compulsive habits of protruding the mandible Trauma to the mid face during growth phase
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Frequency ď °
1-3%
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Depends on ethnic geographic factors and age
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Initial symptoms of Class III ď °
1. Eruption of the maxillary central incisors in a lingual relationship and mandibular incisors in a forward position with no over jet
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2. Development of an incisal cross bite during the eruption of lateral incisor into a normal relation ship
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3. Full incisor cross bite some weeks later
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4. Flattening of the tongue as it drops away from the palatal contact and posture forwards pressing against the lower incisors.
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5. Habitual protraction of the mandible by the child into the protruded functional and morphological relationship. www.indiandentalacademy.com
In complete deciduous dentition
Mandibular anteriors are ventral to maxillary one.Limited overbite is present.
Mandibular arch is too far ventral to maxillary one.Good transverse Mandibular deciduous molars occlude relation too far mesially to maxillary.Terminal Anterior crossbite www.indiandentalacademy.com plane –large mesial step
In intertransitional period
Mandibular and maxillary incisors erupted. Incisal edges of maxillary incisors contact the lingual surface of mandibular
Ventral position of mandibular dental arch in relation to maxillary. Reverse overjet in incisor- canine region. The individual position of the teeth is Mandibular first permanent molar occludes too in accordance with the deviation in far mesially to the maxillary one. contacts and crossing over the www.indiandentalacademy.com Contact surface between them is small. occlusion in canine region.
In permanent dentition
Mandibular permanent canine are position labially to the maxillary lateral incisors.
Ventral position of the mandibular dental arch in relation to maxillary. All posterior teeth occlude too Reversed over jet in anterior region much mesially by one premolar The position of individual teeth is www.indiandentalacademy.com adapted to crown width. the deviations in occlusal relations.
Evaluation of Class III ď °
Deciduous dentition -Scissors bite with the facets of wear on specific teeth -Spaces between the teeth -Tooth bud in the mandible -Under development of the maxilla
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Mixed dentition - Cross bite of individual teeth - Minimal over jet - Lingually inclined lower incisors to achieve a normal over jet ď °
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Classification Angle’s classification 1. True Class III- Skeletal
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2. Pseudo or Postural or Habitual class III -forward movement of the mandible during jaw closure
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3. Class III subdivision – Class III molar relation on one side and Class I relation on other side
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Cephalometric Classification ď °
1. Class III malocclusion caused by dento alveolar mal relationship
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2. Class III malocclusion with long mandibular base
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3. Class III malocclusion with an under developed maxilla
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4. Class III malocclusion with a combination of under developed maxilla and prominent mandible; horizontal and vertical growth pattern.
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5.Class III skeletal malocclusion with tooth guided or pseudo force bite
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Clinical Features
Extra oral features
-Straight to concave profile
Anterior facial divergence www.indiandentalacademy.com
-Long face (increased lower facial height) Prominent chin Steep mandibular plane Mandible appears to be well developed (obtuse gonial angle) Lower lip full and pendulous Maxillary vertical height deficient
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Intra oral features ď ° Class III molar and canine relationship
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Edge to edge incisors relationship or anterior cross bite
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Upper arch is frequently narrow and short and lower arch is broad Upper teeth crowded and mandibular arch is often spaced Vertical growers – anterior open bite Presence of occlusal pre maturities resulting in habitual forward positioning of the mandible
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Diagnostic consideration Clinical examination Functional analysis Radiographic examination Cephalometric analysis Study model analysis Soft tissue examination
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www.indiandentalacademy.com Leader in continuing dental education
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