Abstract
The process of acquiring masticatory functional stability in the intercuspal position in the treatment course of occlusal guidance for a child patient with posterior crossbite in the left side of the jaw was investigated using the Dental Prescal System. The patient was a male infant in the IIC stage of Hellman's dental age. The crossbite was corrected by means of a framework rapid maxillary expansion appliance. We evaluated, by Dental Prescale, the occlusal contact area, the bite force, the occlusal load center and the asymmetry index, before and after expansion, besides during fixed and natural retention.
1 . Occlusal contact area and Bite force
The occlusal contact areas and the bite force of the left deciduous canine, the left second deciduous molar and the bilateral first molars, were magnified by degrees. The occlusal contact area and the bite force of the total dentition were reduced temporarily after the expansion, but when a lingual arch appliance was used for retention, they increased again.
2. Occlusal load center
After the expansion, the occlusal load center was located forward in the anteroposterior dimension, but during fixed retention it moved backward. Laterally it shifted to the left side, afterwards to the median line.
3. Asymmetry index
The asymmetry index was the least after two months of using the lingual arch appliance as retainer.It increased later on, but it reduced again after the natural retention.
Therefore even if the occlusion had been stable morphologically, the lateral and anteroposterior balances of the bite force distribution were disharmonious; the functional stability of the occlusion was acquired gradually during the natural retention phase.
