Malocclusion

Variations in Growth Patterns

Growth patterns are classified into 3 main types of occlusion, determined when the jaws are closed and the teeth are held together ( Fig. 335.1 ). According to the Angle classification of malocclusion, in class I occlusion (normal), the cusps of the posterior mandibular teeth interdigitate ahead of and inside of the corresponding cusps of the opposing maxillary teeth. This relationship provides a normal facial profile.

In class II malocclusion, buck teeth , the cusps of the posterior mandibular teeth are behind and inside the corresponding cusps of the maxillary teeth. This common occlusal disharmony is found in approximately 45% of the population. The facial profile can give the appearance of a receding chin (retrognathia) (mandibular deficiency) or protruding front teeth. The resultant increased space between upper and lower anterior teeth encourage finger sucking and tongue-thrust habits. In addition, children with pronounced class II malocclusions are at greater risks of damage to the incisors as a consequence of trauma. Treatment includes orthodontic retraction of the maxilla or stimulation of the mandible.

In class III malocclusion, underbite , the cusps of the posterior mandibular teeth interdigitate a tooth or more ahead of their opposing maxillary counterparts. The anterior teeth appear in crossbite with the mandibular incisors protruding beyond the maxillary incisors. The facial profile gives the appearance of a protruding chin (prognathia) with or without an appearance of maxillary deficiency. If necessary, treatment includes mandibular excess reduction osteotomy or orthodontic maxillary facial protrusion.