Genetics or environment? A twin-method study of malocclusions.
OBJECTIVE
To assess malocclusions susceptible to orthodontic prophylaxis by using the twin-method of analysis.


METHODS
A comparative analysis of malocclusion was performed in monozygotic and dizygotic twins (164 twin-pairs: 90 monozygotic pairs composed of 50 male and 40 female twin-pairs, and 74 dizygotic twin-pairs, with 46 male twin-pairs and 28 female twin-pairs). The zygotic twin-status certainty was 98%, assigned using serologic and morphologic criteria together with dermatoglyphs. The Allen equation was applied for calculation of the hereditary coefficient for a given malocclusion. Significance established at P < .05 was used to analyze the data.


RESULTS
Different distribution of within-pair malocclusions depended upon the gender of the individuals; nevertheless, the differences with statistical significance occurred only in Class II males and females and males with crossbites. High frequency of within-pair malocclusion similarity (80% to 94%) characterized all groups except the dizygotic males, where the magnitude was 2 times less. The differing distribution of the dentoalveolar discrepancies was not statistically significant (P > .05). The frequency of within-pair similarity equaled 100% in monozygotic patients, while only 57% was found in dizygotic females. The hereditary coefficient had low or negative values-only in males did the examined values exceed 10%.


CONCLUSIONS
This investigation showed that environmental factors account for more malocclusions than previously believed. This result encourages early intervention to intercept, disrupt, and diminish the effects of malocclusions.
Kawala
Beata
B
Department of Maxillofacial Orthopedics and Orthodontics, Wroclaw Medical University, Wroclaw, Poland.
Antoszewska
Joanna
J
Necka
Agnieszka
A
D004200:Diseases in Twins / Q000235:genetics*; D004777:Environment; D005260:Female; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000235:genetics*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic