[Long-term changes of hard-tissue in borderline cases with extraction vs. non-extraction treatment].
OBJECTIVE
To investigate hard-tissue changes in borderline cases with extraction and non-extraction during treatment and follow-up stages.


METHODS
Five associate professors, who were from Peking University School and Hospital of Stomatology, were asked to make judgment on the cases with full pre-treatment records for discriminating the borderline cases from extraction and non-extraction cases. Fifty-four borderline cases with full treatment records which had been out of treatment for at least 2 years were followed. Twenty-one cases with follow-up records were collected including 8 extraction cases and 13 non-extraction cases. Cephalometric measurements were preceded in IDAS (Image and Database Analysis System) software program.


RESULTS
In extraction group, significant changes of SNB, SNPg in A-P direction and that of ArGo/ANSMe, MP/SN in vertical direction were present during the follow-up stage, while the overjet was stable. In non-extraction group, only decrease of proclination of lower incisor and increase of overjet were present without any skeletal changes during the follow-up stage. In comparison of the two groups, no skeletal and dental changes showed statistically significant difference except for MP/SN and ArGoGn in pre-treatment stage, while dental characteristics in relation to upper and lower incisor (L1/NB, L1-NB, L1-AP, U1-AP, U1/L1) showed statistically significant difference between the two groups after treatment. But in follow-up stage, the skeletal and dental pattern tended to be similar for both groups only except for the proclination of lower incisor.


CONCLUSIONS
The similarities of skeletal and dental pattern are demonstrated in extraction and non-extraction group before treatment. Dental changes are the major post-treatment changes in the two groups. In follow-up stage, counter-clockwise rotation of mandible is unique in extraction group, which is likely a helpful factor for stability of overjet, while lingual tipping of lower incisor in non-extraction group without skeletal changes may contribute to overjet relapse.
Liu
Yan
Y
Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China.
Huang
Wei
W
Xu
Tian Min
TM
D002508:Cephalometry; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D009971:Orthodontics, Corrective; D014081:Tooth Extraction