Clinical relevance of third permanent molars in relation to crowding after orthodontic treatment.
OBJECTIVE
The purpose of this study was to determine the relationship between dental crowding and the clinical presence or absence of third permanent molar teeth.


METHODS
Ninety-nine patients were analysed before and after orthodontic treatment and at least three years after the end of retention. The sample consisted of four groups: subjects whose third permanent molar teeth had erupted into the mouth, were non-erupted, were extracted, and were congenitally absent. Arch Length Discrepancy, Irregularity Index and observer bias were examined. Multivariate analysis of variance with repeated measurements was used to analyse differences between the four groups.


RESULTS
Significant differences in Arch Length Discrepancy during time were shown between the premolar segment and the frontal area. The group with third permanent molar teeth congenitally missing showed a significant higher positive Arch Length Discrepancy in the premolar segment of the upper jaw. No significant differences in Irregularity Index were found between the third molar groups.


CONCLUSIONS
It can be concluded that there is no relation between crowding and the presence or absence of third permanent molar teeth.
van der Schoot
E A
EA
Department of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), The Netherlands.
Kuitert
R B
RB
van Ginkel
F C
FC
Prahl-Andersen
B
B
D000293:Adolescent; D000328:Adult; D000848:Anodontia / Q000503:physiopathology; D015982:Bias; D001641:Bicuspid / Q000473:pathology; D002648:Child; D003724:Dental Arch / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000209:etiology* / Q000473:pathology / Q000628:therapy; D008437:Maxilla / Q000473:pathology; D008964:Molar, Third / Q000002:abnormalities / Q000503:physiopathology* / Q000601:surgery; D015999:Multivariate Analysis; D015588:Observer Variation; D009971:Orthodontics, Corrective; D012008:Recurrence; D014078:Tooth Eruption; D014081:Tooth Extraction; D014097:Tooth, Unerupted / Q000503:physiopathology