Objective: The purpose of this study was to investigate the center height of clinical crowns and the difference among individuals, together with the regularity of the Spee curve in mandible and compensating curve in maxilla for the people with normal occlusion in Chengdu area.
Methods: The data were derived from systematically collected people with normal occlusion in Chengdu area, including 36 males and 39 females (ranged from 18 to 35 years). The values of center height of clinical crowns, the depths of Spee curve and curve formed by the center of clinical crowns in mandible were obtained by measurement. Afterwards, the distribution of the center height of clinical crowns was analyzed, as well as the depth of curve formed by the center of clinical crowns in mandible and its correlation with depth of Spee.
Results: (1) The distribution of the center height of clinical crowns accord with normal distribution and the standard deviation was minor(< 0.5 mm); (2) There was no statistical difference between male and female for the center height of clinical crowns; (3) The depth of curve formed by the center of clinical crowns in mandible and the depths of Spee curve showed highly correlation (gamma = 0.986, P < 0.0001).
Conclusion: (1) The difference of the center height in clinical crowns among individuals with normal occlusion in Chengdu area was minor; (2) There was no significant difference on the center height in clinical crowns between male and female; (3) Provide a recommended bracket placement chart suitable for people of Chengdu area in clinical practice; (4) The brackets of the pre-adjusted appliance should be placed in the center of clinical crowns, despite some adjustment are needed in some special circumstances.