Abstract
The aim of this work was to compare the changes on cephalometric radiographs before and after treatment using Invisalign clear appliances in patients with a clinically proven frontally open bite. Also, the amount of the planned movement was compared with the amount measured on the radiographs.
This retrospective study included 30 patients with a frontally open bite (HS < 0) treated by Invisalign clear appliances in both jaws. There were 11 women and 19 men and the average age was 20. Patients were given non-extraction treatment lasting 20 months on average. Twenty-one parameters (eight linear, 12 angular and one ratio) were evaluated on the cephalometric radiographs made before starting treatment (T1) and after its completion (T2). The differences between the planned movements and the changes resulting from the treatment were likewise compared.
There was a statistically significant intrusion of molars in the maxilla (0.66-0.83 mm) during the treatment. A statistically significant deepening of the bite was measured (2.7 mm on average), but the autorotation of the mandible was not statistically significant. Significant extrusions were recorded in the incisors (0.95-1.06 mm in upper and 0.38 mm in lower incisors). Significant changes were also recorded in the interincisal angle (an average increase of 10.84°) thanks to the significant oral inclination of both upper (4.73° on average) and lower (5.53° on average) incisors. No significant changes to the occlusal plane were recorded during treatment. The difference between the planned movement and the amount measured was not significant for most movements.
Clear appliances can be used to treat less severe instances of open bite. The clinical effect of the deepening of the bite is achieved by a combination of the intrusion of the lateral segments and the extrusion and oral inclination of the frontal segments. In particular, the resulting oral inclination was greater than planned. However, significant changes to sagittal relations due to the autorotation of the mandible probably cannot be expected, and hence a significant improvement of the facial aesthetics is likewise unlikely.