Normal Occlusion and Andrew's Six Keys

The upper incisors are tilted inwards (lingually), creating a space behind the upper right canine. This arrangement results in a misaligned Class I canine relationship.

The outer surfaces of the teeth are tilted inwards (lingually), creating a more pronounced buccal (cheek) side at the gum line compared to the biting surface.

This key focuses on the alignment of the teeth in the mouth. Rotated teeth can disrupt proper spacing and function, leading to a variety of issues.

Rotated molars and premolars take up more space than normal while rotated incisors may take up less space.

Rotated canines can negatively affect the appearance of the smile and interfere with biting.

Teeth should touch properly with no gaps in a normal bite. This ensures even pressure distribution and prevents tooth movement.

Space between the upper teeth and a Class I canine relationship indicate a discrepancy in tooth size between the upper and lower jaws.

A Bolton discrepancy refers to a mismatch in the size of the upper and lower teeth.

This is an angle measured at the center of the labiolingual crown, between a line perpendicular to the occlusal plane and a line tangent to the labiolingual crown. A positive value means the crown is tilted towards the lingual side. A negative value means the crown is tilted towards the labial side.

The angle formed between the long axis of an incisor and the line tangent to the crown's labial-lingual axis. A positive value means the crown is tilted towards the lingual side. A negative value means the crown is tilted towards the labial side.

Incisors that are too upright in their positioning are tilted labially. The upper incisors should have a slight lingual tilt. If they are tilted too far labially (negative value), the occlusion can be unstable. With this tilt angle, the canines may not guide properly, and the back teeth might shift to the mesial direction.

When the back teeth are in a good position but the upper incisors are too far lingual (positive labiolingual inclination), there can be gaps between the front teeth. This is a common misconception that the front teeth are too big when it's actually the position of the incisors that creates the spacing.

A proper bite where the upper incisors have a slight lingual tilt (positive labiolingual inclination), providing stability to the occlusion and proper guidance for the canines.

The angle formed between the upper and lower incisors' crown tangents. This angle is important for proper chewing and jaw function.

The angle formed between the axes of the upper and lower incisors. This angle is slightly different than the interincisal angle, as it measures the angle between the vertical axes of the teeth.

The proper alignment of the maxillary and mandibular incisors, where the upper incisors overlap the lower incisors by a slight amount.

The natural curve of the occlusal plane from the back molars to the front incisors. It's a slight downward curve when looking from the side.

The occlusal plane is relatively flat, with minimal or no curve.

The occlusal plane curves upwards from the back molars to the front incisors creating too much space for the upper teeth, causing crowding.

The occlusal plane curves downwards too much, making the upper teeth crowded and potentially affecting the bite.

The upper jaw has too much space, making the bite unstable and affecting development.

The upper jaw has too little space, pushing upper teeth forward and increasing overbite.

The upper teeth are slightly forward, and the edges of the upper front teeth are about the thickness of the upper front teeth away from the lower teeth.

The upper front teeth cover about one-third of the lower front teeth.

Deviation from the normal arrangement of teeth within the same arch or between opposing arches.

Systems used to categorize and describe different types of malocclusion based on tooth relationships and skeletal patterns.

A classification system that focuses on the relationship between the upper and lower first molars.

Modifications that address limitations of the original Angle's classification, such as incorporating incisor relationships and skeletal patterns.

A classification system focusing on six key elements: incisor position, molar relationship, overjet, cant of the occlusal plane, arch form, and arch width.

Classification based on the underlying skeletal structure, including the relationship between the maxilla and mandible.

A classification system that describes the relationship between the upper and lower incisors, using terms like Class I, Class II, and Class III.

A classification system that describes the position of the canine teeth, considering both their alignment and relationship to other teeth.

A condition where only one side of the mouth exhibits a Class III molar relationship, while the other side displays a normal relationship.

A common system for classifying malocclusion based on the relationship of the first molars. Offers a simple and practical approach.

An adaptation of Angle's classification by Lischer, where Class I, II, and III are renamed as Neutrocclusion, Distocclusion, and Mesiocclusion respectively.

An expansion of Angle's Class I and III into specific types, addressing various dental issues like crowding, rotations, and crossbites.

Andrew's classification system that focuses on achieving ideal occlusion, encompassing factors like molar relationship, crown angulation, incisor alignment, rotation, spacing, and occlusal plane.

A system that assesses the skeletal relationship between the maxilla and mandible in the front-to-back direction. It identifies whether the maxilla is positioned forward or backward relative to the mandible.

A skeletal classification category where both the maxilla and mandible are in alignment.

A skeletal classification category characterized by the maxilla being protruded relative to the mandible.

A classification system for malocclusion that incorporates Angle’s classification and five additional characteristics, presented within a Venn diagram.

Refers to the curved line that follows the facial edges of the maxillary anterior and posterior teeth, highlighting the aesthetic appearance of the teeth in the smile.

Rotation of the jaw or teeth around a vertical axis, resulting in a midline discrepancy. This can lead to a noticeable shift in the position of the teeth, creating a misaligned appearance.

Rotational movement around the transverse axis, resulting in a vertical shift of the teeth. This can cause differences in the height of the teeth on the right vs. left side.

Describes rotations around the anteroposterior axis, resulting in variations in the vertical position of the teeth relative to the lips and cheeks.

These additional characteristics, along with Angle's classification, provide a comprehensive method for analyzing malocclusion, enabling a more thorough understanding of the complexities of misaligned teeth.

Ackerman & Proffit's classification system is valuable for its comprehensive analysis of malocclusion, but it has limitations. It lacks etiological considerations, focuses solely on static occlusion, and does not account for all three-dimensional problems.