Bad habits
For example, licking during teething can lead to anterior protrusion of the upper and lower front teeth (buck teeth); finger sucking and biting the lower lip can lead to a tendency for the upper front teeth to be labially inclined and buck. Prolonged mouth breathing can cause the lip muscles to relax and the lower jaw to recede, creating upper jaw buck teeth.
Localised disorders during the teething period
The congenital loss of the lower front teeth during teething, or the premature loss of the mandibular milk molars for various reasons, can lead to an underdevelopment of the anterior part of the mandibular arch or a reduction in the length of the lower arch and a relative protrusion of the upper front teeth or the upper arch; abnormalities in the order of eruption of the anterior maxillary teeth and permanent molars during teething can also lead to upper front teeth bucking.
Trauma
Trauma to the mandible or chin during growth and development, resulting in delayed development of the mandible or temporomandibular joint, can lead to bony mandibular recession, which can also manifest as maxillary buck teeth.
Macroglossia
Overdevelopment of the upper and lower dental arches due to an oversized tongue and strong tongue muscles, resulting in sagittal protrusion of the upper and lower teeth forward, which manifests as buck teeth.