The effects of maxillary quad-helix appliance expansion on cephalometric measurements in growing orthodontic patients.

This study was conducted to examine the effects of maxillary quad-helix expansion on frontal and lateral cephalometric measurements in growing orthodontic patients. Twenty subjects, nine girls and eleven boys (x age = 10 years 3 months), each exhibiting at least a unilateral posterior lingual cross-bite that had been treated with a maxillary quad-helix appliance, were selected for this study. Posteroanterior and lateral cephalometric radiographs were taken at the beginning of treatment (T1), when the appliance was removed (Tprog, x time = 9 months), and at retention (T2) and subsequently traced. The T1 and T2 dental casts were also measured as supplements to the cephalometric measurements. Significant orthodontic changes, as seen on the frontal radiographs from T1 to Tprog, included a mean increase in maxillary intermolar width of 5.88 mm, a mean increase in average frontal molar relation of 2.95 mm., and a mean increase in maxillary intercanine width of 2.74 mm. The orthopedic changes, as evidenced radiographically, included a mean increase in maxillary width of 0.92 mm. and an increase in average maxillomandibular width of 0.89 mm. From the above data, a 6:1 ratio of orthodontic movement to orthopedic movement was determined. No significant change in mandibular intermolar width was observed from the cephalometric data or from the cast measurements. The most stable cases after expansion had normal nasal widths and narrow maxillary widths. No correlation was shown between the age of the patients and the orthopedic expansion recorded or between the amount of orthodontic/orthopedic expansion and facial type. It was concluded that all expansion changes showed little relapse from Tprog to T2 and that moderate orthopedic expansion is possible with the quad-helix, but only slight orthopedic expansion was consistently demonstrated.