Dental abnormalities in patients with unilateral agenesis of the permanent mandibular second premolar. Literature review

Introduction
Congenital agenesis of permanent tooth germs is a common dental abnormality in humans. Depending on the number of missing teeth, this anomaly can take one of three forms: hypodontia, oligodontia or anodontia. Hypodontia predominantly affects lower second premolars. It is accompanied by disorders such as increased distal angulation of the contralateral tooth germ and delayed development of all permanent teeth germs. The management of patients diagnosed with hypodontia of that tooth depends on the patient's age and concomitant occlusion disorders.

Aim
This paper aimed to review the literature on concomitant dental abnormalities in patients with unilateral agenesis of the mandibular second premolar.

Material and methods
The authors reviewed papers published between 1970 and 2019 focusing on dental abnormalities in patients with hypodontia. The literature search was performed using PubMed to access the Medline database. The search generated a total of 150 articles. 26 publications were selected for analysis.

Results
Most papers on dental abnormalities in patients with unilateral agenesis of the permanent mandibular second premolar also report the presence of concomitant disorders such as increased distal angulation of the contralateral tooth germ and delayed development of all permanent teeth germs.

Conclusions
The agenesis of the lower second premolar is accompanied by other dental disorders such as increased distal angulation of the contralateral tooth germ and delayed development of permanent tooth germs. Understanding the mechanisms behind dental abnormalities and the tendency for concomitant presence of a number of disorders is an important prerequisite in order to plan an optimal course of treatment.