The Journal
The presence of strong masticatory muscle pattern in Class II division 2 cases could have been explained by the genetically determined
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muscular and neuromuscular system . A clin ¬ ical and cephalometric study intra and inter pair comparisons of 114 Class II division 2 malocclu ¬ sions , 48 twin pairs and six sets of triplets were made . The concordancedisconcordance rates for monozygotic and dizygotic twins were determined . 100 per cent of the monozygotic twin pairs were concordant and almost 90 per cent of the dizygotic twin
20 pairs showed disconcordance . Class III Malocclusion
The influence of genetics on facial features was obvious in some families especially in Class III mal ¬ occlusions . This phenotype has been known for its appearance in certain European
21 noble families such as Hapsburg royal family .
A Study done by Litton et al where a group of pro-bands , siblings and parents with Class III mal ¬ occlusion were analyzed and in 1 / 3 of the parents of the subjects , severe mandibular
22 prognathism was observed .
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Study results of Schulze and Weise ( 1965 ) also reported that concordance of mandibular prognatism on monozygotic twins was six times higher than di ¬ zygotic twins .
Many cephalometric studies showed distinct skeleto-facial pattern in monozygotic twins
24,25 having class III malocclusion .
MALOCCLUSIONS ASSOCIATED WITH VERTICAL PLANE
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Savoye et al reported that the vertical proportions are highly under genetic control .
A study done by Hunter , using linear measure ¬ ments on lateral cephalograms , demonstrated that there is a stronger genetic component of vari ¬ ability for measurements in vertical dimension , rather than for
27 measurements in the sagittal di-mension .
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Manfredi et al , in his study on monozygotic twins , dizygotic twins and same-sex siblings , suggested that the vertical parameters were more genetically controlled than the anteropos ¬ terior parameters . The high ¬ er prevalence of anterior openbite in black popu ¬ lation compared to the white population and the higher prevalence of deepbite in whites may re ¬ flect a different inherent facial
5 morphology rather than environmental factors .
MALOCCLUSION ASSOCIATED WITH TRANSVERSE PLANE
One of the most challenging problems to an orthodontist is per ¬ haps caused by cleft lip and / or palate ( CL / P ). CL / P is a congenital malformation inherited as a dis ¬ continued
29
multifactorial trait which is characterized by deficient maxillary growth leading to maxillary deficiency . Transverse growth of maxilla is affected due to discontinuity of palatal halves leading to buccal crossbite and functional shift . Although , many environmental and develop ¬ mental factors are known to play role in CL / P etiol ¬ ogy , the genetic factors have also been defined as the causes of clefting
30
conditions . The cleft studies carried on twins showed that the monozygotic and dizygotic twin concordance rates were 35 per cent and 5 per cent , respectively and these results re ¬ flect the
31 heritability of the condition .
MALOCCLUSIONS ASSOCIATED WITH GENETIC SYNDROMES Syndrome is a group of symptoms which consistently occur together , or a condition characterized by a set of associated symptoms .
34 Vol . 13 No . 3 Sep-Dec 2017