11: Reverse overjet

11 Reverse overjet

Summary

Alistair, 8.5 years old, presents with a reverse overjet on all of his upper incisors (Fig. 11.1). What is the cause and how may it be treated?

image

Fig. 11.1 Right buccal occlusion at presentation.

History

Complaint

Alistair is not bothered about the way his teeth bite together and is not concerned about any aspect of his facial appearance. His father, however, feels that Alistair’s chin is somewhat prominent and gives the boy an aggressive-looking appearance. Sometimes Alistair is teased about his chin at school.

History of complaint

Alistair’s permanent upper front teeth erupted behind his lower teeth. His mother’s recollection is that the bite of his ‘milk’ teeth was similar. Alistair is not bothered by the occasional teasing he gets about his chin.

Alistair’s parents are keen for treatment, if possible, at this stage to correct his bite and reduce the prominence of his chin, which would remove the source of teasing at school.

Medical history

Alistair is fit and well.

Family history

Alistair’s father reports that his own teeth meet in a manner similar to the boy’s and he also has a slightly prominent chin but is unconcerned by it. His father had orthodontic treatment with extraction of two lower teeth and fixed appliances when he was a teenager to correct the bite of his front teeth. His bite changed a lot after he stopped wearing the retainers.

Examination

Extraoral

Alistair has a mild Class III skeletal pattern with average FMPA (Fig. 11.2) and no facial asymmetry.

image

Fig. 11.2 Profile.

image What other features would you check for?

• The presence/absence of a mandibular displacement on closure.
• Temporomandibular joint signs/symptoms.

Alistair could just achieve an edge-to-edge incisor relationship.

A 3 mm anterior mandibular displacement on image was detected from RCP to ICP. No temporomandibular joint signs were noted and Alistair reported no temporomandibular joint symptoms. There was no masticatory muscle tenderness.

Intraoral

image What are your observations from the intraoral views (Figs 11.1 and 11.3)?

The soft tissues appear healthy with the exception of mild marginal gingival erythema related to the incisor teeth. Oral hygiene is fair. The dentition appears caries free. 6 e d c 2 1 are present in each quadrant.
Upper and lower incisors are very mildly crowded and in crossbite. The overbite is average to slightly increased and complete. Upper and lower centrelines are displaced. The buccal segment relationship is Class III bilaterally.
image

Fig. 11.3 Left buccal occlusion.

image What are the possible causes of the reverse overjet?

These are listed in Table 11.1.

Table 11.1 Causes of reverse overjet

Cause Aetiology
Skeletal Usually Class III due to any of the following: long mandible, forward placement of glenoid fossa positioning the mandible more anteriorly; short and/or retrognathic maxilla; short anterior cranial base
Anterior mandibular displacement on closure A premature contact may displace the mandible forward on closure into maximum interdigitation
Retained primary upper incisors These may deflect the eruption path of their successors palatally into crossbite
Pattern/excessive mandibular growth Forward pattern of mandibular growth will exacerbate a Class III skeletal pattern
Excessive mandibular growth may be due to excess growth hormone resulting from a pituitary adenoma
Restraint of maxillary growth Found in repaired cleft lip and palate and attributed to the effect of post-surgical scar tissue

image What radiographic investigations would you request and why?

A dental panoramic tomogram would be required to account for the presence and position of all the remaining permanent teeth.
A lateral cephalometric radiograph is indicated to assess more accurately the magnitude of the Class III skeletal pattern and the incisor angulations, which will facilitate treatment planning. It will also form a baseline from which treatment progress/growth changes can be evaluated by comparison with future cephalometric films.
The panoramic radiograph showed all permanent teeth to be developing.

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Jan 2, 2015 | Posted by in Orthodontics | Comments Off on 11: Reverse overjet

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