【OBJECTIVE】
Research on the rule of dropout in the implantation of orthodontic anchor screw.
【METHODS】
Analysis using clinical and image data in the number of 270 anchor screws insertion at the median palate.
《#1》Comprehension for the environment related to screw implanting.
《#2》Comparison between the non-dropout groups and the dropout groups.
【RESULTS】
《#1》
・The palatal mucosa is slightly thicker in the front.
・There is little correlation between age and the CT value.
・The implanting torque and the CT value correlate to some extent.
・The length of the screw, the length of the screw in the bone and the thickness of the mucosa are depend on each other.
《#2》The tendency for non-dropout.
・Female.
・Higher age.
・Higher CT value.
・Long screw length.
・Thin mucosa.
・The higher implanting torque.
・In the case of short screw, such as 5mm, the anchor screw is inserted deeply at the bone.
・In the case of rapidly expanding, the success rate of the screw implantation is increased by implanting it laterally.
【CONCLUSIONS】
To understand the risk of screw dropout, it is necessary to evaluate the CT value, mucosa and bone thickness, and to consider the sex and presence or absence of expansion. In conclusion, the long anchor screw, the high implanting torque and deep insertion prevent anchor screws from dropout after implantation in the median palate.