9: Increased overjet

9 Increased overjet

Summary

Emma, aged 11, is teased at school about her prominent upper front teeth (Fig. 9.1). What are the possible causes and how may it be treated?

image

Fig. 9.1 Right buccal occlusion at presentation.

History

Complaint

Emma’s upper front teeth stick out. Her mother is very concerned about her daughter’s appearance and is anxious for her to be treated.

History of complaint

The upper front teeth have always been prominent, even when the primary incisors were present. Emma is teased about her teeth at school and the teasing is upsetting her. She recently fell in the school yard and hit her two upper front teeth on the ground. Fortunately there was only minimal incisal enamel damage to image.

image Medical history.

Emma has had asthma since she was 4 years old. This is managed with a salbutamol inhaler (Ventolin).

Key point

Increased overjet may predispose to teasing and upper incisor trauma.

Examination

Extraoral

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

image

Fig. 9.2 (A) Full face view.

image

Fig. 9.2 (B) Profile.

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:

1 Anteroposterior. Viewing the soft tissue facial profile in most cases allows the following classification to be made:

Class I: the mandible lies 2–3 mm behind the maxilla.
Class II: the mandible lies more than 2–3 mm behind the maxilla.
Class III: the mandible lies less than 2–3 mm behind the maxilla.

Due to variation in lip thickness, this method is not always reliable and palpation of the alveolar bases over the apices of the upper and lower incisors in the midline has been claimed to give a better estimate of skeletal pattern.

Emma has a Class II skeletal pattern.

2 Vertical.

Lower facial height. The distance from the mid eyebrow level to the base of the nose (upper facial height) should equal that from the base of the nose to the inferior aspect of the chin (lower facial height). The lower facial height is reduced when the latter measurement is reduced and the converse is true when this distance is increased.
Frankfort-mandibular planes angle (FMPA). With a finger along the lower border of the mandible and a ruler placed along the Frankfort plane, project both of these lines backwards in the imagination to estimate the FMPA. The FMPA is then classified as average (both lines intersect at the back of the skull, occiput), reduced (both lines meet beyond occiput) or increased (both lines meet anterior to occiput).

Emma has a slightly reduced lower facial height and FMPA.

3 Transverse. Stand directly behind the patient and look down across the face, checking the coincidence of the midlines of the nose, upper and lower lips and midpoint of the chin. Alternatively assess the face from the front. It is important to note that slight facial asymmetry is common. The location (upper, middle or lower facial third) and extent of any asymmetry should be recorded. Emma’s chin point is marginally to the right. As this is very mild and has not been noticed by her or her mother before now, and as a slight degree of facial asymmetry is regarded as normal, there is no cause for concern.

No mandibular deviation on closure or temporomandibular signs/symptoms were detected.
The lips are habitually competent with the lower lip tending to lie under the upper incisors at rest (Fig. 9.2B).

Intraoral

image The intraoral views are shown in Figures 9.1 and 9.3. What do these show?

There are plaque deposits on several teeth and overall mild marginal gingival erythema.
All teeth appear to be good quality.
Emma is in the permanent dentition with image present. (Note image are erupting.)
The upper and lower arches are uncrowded.
image

Fig. 9.3 (A) Anterior occlusion.

image

Fig. 9.3 (B) Left buccal occlusion.

There is a Class II division 1 incisor relationship with increased overjet (measured 7 mm clinically); the overbite is increased and complete. The buccal segment relationship is a half-unit Class II bilaterally. There is a lingual crossbite (scissors bite) affecting image.

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/>

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  5. 30: The fractured permanent incisor root
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Jan 2, 2015 | Posted by in Orthodontics | Comments Off on 9: Increased overjet

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