International Journal of Pharmaceutical Science and Health Care Issue 7, Vol. 2 (March- April 2017) Available online on http://www.rspublication.com/ijphc/index.html ISSN 2249 – 5738

Class III malocclusion is thought to be a result of interaction of genes and environment, studies on family pedigree chart have pointed on its probability of its monogenic dominant inheritance. Vascular endothelial growth factor, insulin like growth factor 1 and HOX -3 are few of those genes .The influence of genetic factors can be understood only when studied in quantitative terms. This review is about the role of genetics and how it influences facial morphology. INTRODUCTION: Class III malocclusion has been the subject of study of interest because of the challenge in treating class III malocclusion. Class III malocclusion is defined in cases in which the mandibular 1st molar is placed mesially to the maxillary 1st molar.[1] It can be skeletal or dento-alveolar. Its etiology is generally believed to be genetic and familial occurrence. A wide range of environmental factors contribute to class III malocclusion .They are enlarged tonsil, difficulty in nasal breathing[2]congenital anatomic defects, disease of pituitary gland[2]hormonal disturbances and premature loss of primary molars[3] and loss of deciduous incisors [4] A wide range of hormones such as IHH (Indian hedgehog homolog) [5], PTHLH (Parathyroid like hormone), VEGF (vascular endothelial growth factor), etc.., are seen to play a major role in development of class III occlusion. Recent studies have shown that erythrocyte membrane proteint band (EPB4) also has influence in bringing about mandibular prognathism. MODE OF INHERITANCE IN CLASS III MALOCCLUSION: The inheritance of phenotypic features in mandibular prognathism was first reported by Strohmayer [6] and then by Wolff et al[7]their analysis of pedigree chart of Hapsburg family. Suzuki [8] reported a frequency of 31 percent was affected if the father was affected, 18 percent if the mother was affected and 40 percent if both parents were affected on studying 243 Japanese families. Nikolova [9] Studied 251 Bulgarian families and showed great parental influence for head height and nose height. International Journal of Pharmaceutical Science and Health Care Issue 7, Vol. 2 (MarchApril 2017) Available online on http://www.rspublication.com/ijphc/index.html ISSN 2249 – 5738 R S. Publication, [email protected] Page 68 Heritability of craniofacial morphology Has also been investigated in siblings, from parents to twins or from parents to off springs in longitudinal studies. Horowitz et al [10] demonstrated a significant hereditary component for anterior cranial base, mandibular body length, lower facial height and total facial height. Hunter et al [11] reported a strong genetic correlation between fathers and children especially in mandibular dimension. Fernex et al [12] found that the sizes of skeletal facial structures were transmitted with more frequency from mothers to sons than to mothers to daughters. ROLE OF GENES IN EXPRESSION OF CLASS III MALOCCLUSION : Although mandibular prognathism has been said to be a polygenic [13] or multi factorial trait, in majority of the cases, there are families in which the trait appears to have autosomal dominant inheritance. PEDIGREE CHART -AUTOSOMAL DOMINANT INHERITANCE -CLASS III