Usually called buck teeth, refers to in the front and back, the distance between the incisor edge of the front teeth and the lower front teeth lip surface is too large, from the incisor edge of the front teeth to the lower front teeth lip surface of the maximum horizontal distance is more than 3mm; The distance between the anterior teeth and the lower anterior teeth is too large, that is, the incisor of the anterior teeth exceeds 1/3 of the length of the crown of the lower anterior teeth or the occlusion of the lower anterior teeth exceeds 1/3 of the lingual side of the anterior teeth.

The upper and lower teeth of the open jaw cannot be closed after occlusion, involving the scope of anterior teeth, premolars, molars; There was no overlap between the incisors of the upper and lower anterior teeth, and the vertical gap was anterior jaw opening.

There is a gap between teeth with sparse dentition, that is, the amount of teeth (the total width of crown) is relatively small, while the amount of bone (the total length of alveolar arch) is relatively large. Sometimes, different phenomena such as near and far middle direction of teeth and lip-lingual dislocation can occur.

The teeth are disordered due to insufficient space, that is, the tooth volume (the total width of the crown) is relatively large, but the bone volume (the total length of the alveolar arch) is relatively small, and the teeth have different degrees of lip (buccal) lingual dislocation or torsion.

Anti jaw is usually called ground bao day, refers to the lower teeth occluded in the upper teeth of the outside, including the front teeth and horizontal teeth anti jaw, from the formation mechanism is divided into dental anti jaw and bone anti jaw.