Tooth Size and Morphology of Affected Molars in Individuals with Congenitally Missing First Molar

Yamada Hiroyuki

doi:10.1537/asj.118.83

The present study aims to assess the validity of the idea that the first molars can be congenitally missing despite the posterior molars are preserved in the permanent dentition. In addition, size and morphology of the affected molars were investigated in detail. Eleven possible cases of such a type of first molar agenesis have been observed in modern Japanese patients (five males and six females). Data were collected from plaster casts, panoramic radiographs, and a questionnaire to the patients. In general, the first molars in the dentition erupt into the oral cavity at an age around six years old. However, in the above-mentioned cases, the eruptions of the molars just behind the premolars were delayed up to around eight to ten years old. In addition, they show more reduced cusp patterns than those of ordinary first molars, being more similar to those of ordinary second molars. None of the patients had three molars on the affected side of the jaw. Moreover, the affected teeth were larger in size than ordinary second molars, probably due to compensatory interaction. Following the conventional interpretation, since any molar in the first position is regarded as first molar, the affected molars would be regarded as first molars whose eruption is delayed by two to four years due to tooth reduction. However, detailed investigation of the dental agenesis cases in the present study suggests that it is more appropriate to interpret that these affected teeth should be second molars, whose eruption was accelerated by a few years, probably due to the congenital absence of first molars.<br>

Tooth Size and Morphology of Affected Molars in Individuals with Congenitally Missing First Molar

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