Class II malocclusion
Class II malocclusions are divided into 2 categories:
- class II division 1: see description and definition further down this page
- class II division 2: see description and definition by clicking on the tab of the subpage.
Class II division 1
A class II intermaxillary dental relationship represents a posterior discrepancy of the lower teeth with regard to the upper teeth. The embrasure between the lower canine and the lower first premolar is shifted backward with regard to the upper canine (blue arrows). The center of the lower first molar (mesiobuccal groove) is posterior to the first corner (mesiobuccal cusp) of the upper first molar (red arrows). The overjet reflects the anteroposterior discrepancy observed where the canines and the molars are (yellow arrow). The overbite is increased and, in the case shown above, the lower teeth are hidden completely by the upper teeth and touch the gingiva at the back of the upper teeth (green arrow). We call this type of deep dental overbite “supraocclusion”.
Seen from above, the maxillary arch is narrower, because it needs to adapt to a more anterior portion of the mandibular arch which is positioned posteriorly with regard to the upper teeth. Interdental spaces can be seen on the maxillary arch. Note that some dental arches of patients in class II show more severe irregularities, because all categories of dental irregularities are possible. The blue arrows indicate where the lower incisors bite into the palate.
Cephalometric profile view
This cephalometric X-ray shows the posterior discrepancy of the lower jaw. The upper teeth are more advanced compared to the lower teeth (a 11-mm overjet) and we can easily see that the lower incisors touch the palate at the back of the upper teeth on the palatal gingiva (10-mm overbite). The length of the face is shorter (distance between the tip of the nose and the bottom of the chin). The discrepancy between the upper and lower teeth makes the lower lip hem under the upper incisors.
The lower jaw is too short with regard to the upper jaw, making the lower teeth farther back with regard to the upper teeth.
This profile shows a dental class II relationship and a skeletal class II relationship. We call such relation “mandibular retrognathia”.
If we sum up the list of problems in the 3 planes in space, we find:
- A length problem: the lower jaw is too short,
- A height problem: the lower third of the face is shorter than normal,
- A width problem: the upper jaw is too narrow
This young patient’s dentition, for which we describe the above malocclusion, shows no particular problems. The third molars can be seen and are in development and we can predict that they will have no room to erupt normally in the mouth. They will presumably have to be extracted. The space between both upper incisors is visible and a little black radiolucent line testifies the absence of fusion of both hemimaxillae at this location. This separation is presumably caused by collagenous fibers composing the lingual frenulum (see the intraoral front view picture) which inserts into the intermaxillary suture.
Editor’s note: The human body has 2 maxillary bones. Both of these bones constitute what we call the upper maxilla. A hemimaxilla refers to either one of these bones that constitutes the upper maxilla.