9: Increased overjet

9 Increased overjet

Examination

Extraoral

Emma’s full facial and profile views are shown in Figure 9.2.

image How would you assess Emma’s skeletal pattern?

The skeletal pattern is the relationship of the mandibular to the maxillary dental base in all three planes of space – anteroposterior, vertical and lateral. With the patient seated upright with the Frankfort plane (superior aspect of the external auditory meatus to the inferior aspect of the orbital margin) horizontal, the lips in repose and the teeth in maximum interdigitation, assessment should be as follows:

Intraoral

image What are the causes of an increased overjet?

These are given in Table 9.1.

Table 9.1 Causes of an increased overjet

Cause Aetiology
Skeletal pattern May be Class I, II or III
If Class II, mandibular deficiency is almost entirely the primary cause but may be excessive horizontal maxillary growth or a combination of the two factors
Soft tissues* Lower lip lying under the upper incisors to create an anterior oral seal will procline the upper incisors and retrocline the lower incisors (likely if there is a Class II skeletal pattern, reduced lower facial height and lip incompetence)
Hyperactive lower lip will retrocline the lower incisors
Primary atypical swallowing pattern (endogenous tongue thrust) will tend to procline upper (but also lower) incisors
Digit sucking habit If present for more than 6 hours out of 24, it will procline upper incisors, retrocline lower incisors, create an anterior open bite and a tendency to buccal segment crossbite
Overjet increase is often asymmetrical due to digit positioning
Crowding Labial displacement of upper incisors and/or lingual displacement of lower incisors
Any combination of above  

* Effects determined principally by the skeletal/>

Jan 2, 2015 | Posted by in Orthodontics | Comments Off on 9: Increased overjet
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