14 Posterior crossbite
Kirsten is 7. She presents with a crossbite of the right buccal segments (Fig. 14.1). What will be your assessment and management options for this problem?
Kirsten’s mother is concerned about the way her daughter’s teeth bite together. She has noticed that Kirsten’s jaw moves to one side as she closes her mouth. This makes her face appear crooked, a further cause of anxiety for her mother.
Kirsten used to suck her thumb until 5 months ago when started to erupt. Her mother has become more aware of her daughter’s ‘deviated bite’ in the past year and wondered if the thumb-sucking habit could have contributed to the problem.
Kirsten has a mild Class III skeletal pattern with slightly increased FMPA; the chin point is displaced slightly to the right. The lips are incompetent but habitually held together. There is a tongue to lower lip swallowing pattern. There is no masticatory muscle tenderness, temporomandibular joint tenderness or crepitus, and mouth opening is not restricted.
It is important to check if there is mandibular displacement on closure as this would indicate that the facial asymmetry is more an apparent than a true skeletal asymmetry. For the former, orthodontic correction of an associated crossbite should be straightforward but for the latter further investigations would be required to determine if the asymmetry is progressive and more complex treatment would be required to address the facial and occlusal problems.
Early correction of a crossbite with a mandibular displacement is indicated to allow the occlusion to develop in an undisplaced position. It is likely also to reduce the possibility of development of temporomandibular joint dysfunction syndrome, which may occur in susceptible individuals in whom this occlusal discrepancy exists.
The upper and lower centrelines should be coincident with each other and with the midline of the face. Both of these aspects should be assessed, the latter by first looking at the patient anteriorly and then down on the face from above. With study models alone, it is not possible to determine the relation of the dental midlines to the facial midline.