Abstract:

BACKGROUND: Prediction of the width between unerupted canine and premolars in mixed-dentition period plays an important role in making plans for occlusion guidance.
OBJECTIVE: To develop prediction equations for estimating the width between unerupted canines and premolars of Han adolescents in Urumqi using data obtained from investigation. 
METHODS: Regression analyses were performed on data derived from144 Han adolescents in Urumqi (68 males and 76 females) using digital vernier caliper. Measurements were taken on plaster casts of all the teeth widths in the front of mesiocontact of the second molars and recorded to the nearest 0.01 mm. These data were analyzed to establish regression equations based on the calculating the correlation coefficients between the mesiodistal widths of the first molar in one arch and that of the canine and two premolars in the same arch.     
RESULTS AND CONCLUSION: The four predication equations had been developed to estimate the size of unerupted canine and premolars for Han adolescents in Urumqi. The following formulas (Y), correlation coefficients (r) and standard deviation of Y for fixed X (S _y.x) were showed: ①Maxillary arch: for males, Y=14. 8382+0.7816X₁ (X₁ equals the mesiodistal width of the first upper molar, r=0.4258, S _y:x1=0.9006); for females, Y =12.209 5+1.00 0X₁ (r=0.487 1, Sy.x1=0.995 0). ②Mandibular arch: for males, Y=13.500 6+0.793 3X₂ (X₂ equals the width of the first lower molar, r=0.464 3, S _y.x2=0.855 4); for females, Y=7.922 3+ 1.269 5 X₂ (r=0.540 9, S _y.x2=0.997 2). The newly developed equations are more applicable for predicting the mesiodistal sizes of unerupted canine and premolars of Han adolescents in Urumqi.