11 Reverse overjet
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?
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.
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 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.
Alistair has a mild Class III skeletal pattern with average FMPA (Fig. 11.2) and no facial asymmetry.
A 3 mm anterior mandibular displacement on 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.
|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|