Oct. 9 (Tue.), 2001

7. Some of crossbites of primary teeth get corrected spontaneously.

Many reports have been published on spontaneous correction of crossbite of primary teeth. In the general population, about 60 to 70% (2/3) of the crossbites found in the primary dentition are said to get corrected spontaneously during the transition to the permanent dentition. Nagahara in the orthodontic department of Aichi Gakuin Univ. Dental School reported that 11.95% of the crossbites seen in his study subjects were corrected spontaneously between Stage IIC and Stage IIIB.
The rate of spontaneous correction during Stage IIA has shown to be 14.17%, which took an average of 5 years and 1 month.
When crossbites of primary teeth were divided into a group with spontaneous correction and a group without it, the latter group showed the following characteristics at age 2 to 3 years:
1) Extent of crossbite: BAAB/CBAABC or greater
2) Deep overbite with large negative overjet
3) Negative overjet even in the most retruded mandibular position
4) Cuspal interference of the upper and lower primary canines
5) Family history of a crossbite

The children whose crossbite of primary teeth corrected itself during Stage IIIA (eruption of permanent anterior teeth) had the following characterstics at age 4:
1) The anterior overjet became positive with the mandible in the most retruded position.
2) The crossbite was limited to the incisors.
3) There was no family history of a crossbite.
4) Degree of facial skeletal deformity: SNP + Gonial angle = 205
5) The upper and lower permanent central incisors were distally positioned within the basal bones, or the crowns were retroclined.
(Prof. Miyahara, Orthodontic Dept., Aichi Gakuin Univ. Dental School)

In addition to caries prevention and treatment recommendation, it is important to train children presenting with a crossbite of primary teeth to put the mandible in a more retruded position. Here is a clinical case undergoing the training, which is implemented to increase the chance of spontaneous correction.

The photographs show another crossbite case.
Her crossbite was corrected with home therapy (self-training), followed by 8 years of observation with regular check-ups.

During the observation period, the patient presented for orthodontic correction of a crossbite of the upper and lower right lateral incisors.

Orthodontic treatment was initiated with an edgewise system (Level Anchorage System).
The treatment was finished in 17 months, followed by retention and observation.