Hemisection of the Lower Second Deciduous Molars in Case of Agenesis of the Second Premolars - History, Application and Clinical Procedure

Dealing with agenesis of permanent teeth is a challenging task in everyday practice. Excluding the third molars, the worldwide prevalence varies greatly with an inconsistent range between 0.15% and 16.18% 1 2 . Of these, the mandibular second premolars are the most frequently missing teeth 3 4 5 6 7 8 . The prevalence of the agenesis of the mandibular second premolars is between 1.02% and 3.5%, depending on the study and population examined 9 10 11 . Female patients are generally affected more frequently than male patients 9 11 12 . If orthodontic space closure is indicated and possible, excessive atrophy of the alveolar process caused by extraction of the teeth 75 and 85 should be prevented, as it slows down tooth movement and the rate of space closure 13 . Just six months after tooth extraction, the alveolar process can be reduced by up to 1.87 mm in width and 1.24-2.03 mm in height 14 15 . The hemisection of lower deciduous molars in the absence of lower second premolars prevents bone atrophy and also represents an effective alternative to orthodontic anchorage with few side effects. The aim of this article is to discuss the history of hemisection in orthodontics, to show areas of application and to explain indications.