Mesioden Theory

INTRODUCTION

A supernumerary or hyperdontia tooth describes an excess in teeth number which can occur in both primary and permanent dentition. Mesiodens was a term coined by Bolk in 1917 to denote the supernumerary tooth present in the maxillary central incisors. By definition mesiodens refers to a supernumerary tooth/teeth present in the premaxilla placed palatally, labially or in between the two central incisors.[1,2,3]

The exact etiology of supernumerary teeth is unknown; however, several theories have been proposed to explain its presence. Out of all the theories only two have been widely accepted. First is the phylogenetic theory as a regression of the anthropoids whose dentition had more teeth and second is the autonomic recessive inheritance or linked to the x chromosome, an abnormal reaction to the local traumatic episode, environmental factors, dichotomy of the tooth germ and the theory of hyperactivity of the dental lamina. [4]

Mesiodens can be classified into 2 subclasses, according to

First the number of mesiodens was noted and out of 29 subjects having mesiodens 24 subjects (82.7%) had single mesiodens, 4 subjects (13.7%) had double mesiodens (Fig 1,2) and 1 subject (3.4%) had multiple mesiodens. Second according to shape it was observed that out of 39 mesiodens 27 (69.2%) were conical shaped, 10 (25.6%) were tuberculate shaped and 2 (5.1%) were molariform in shape. Third according to direction it was observed that 31 (79.4%) were in vertical direction, 2 (5.1%) were horizontally placed and 5 (12.8%) were inverted (Fig 3). Fourth according to position it was observed that 8 (20.5%) where impacted, 26 (66.6%) were partially erupted and 5 (12.8%) were completely erupted. Fifth according to complications maximum cases observed were of diasetma i.e. 17 cases (58.6%), followed by 9 cases (24.1%) of rotation, followed by 3 cases (6.8%) of delayed eruption, only 4 cases (10.3%) were