Arrested eruption of the permanent lower second molar

The incidence of retention/impaction of the permanent lower second molar (M (2)inf) lies between 0.6/1000 and 3/1000. Therefore, the purpose of the pre sent study was to investigate the craniofacial morphology, the frequency of dental anomalies and the inclination of the affected M(2)inf and the adjac ent first molar in patients with arrested eruption of M(2)inf. The overall goal was to elucidate the aetiology of arrested tooth eruption and to prese nt the characteristics of these patients in order to improve diagnosis and treatment planning. Radiographic material (profile radiographs and orthopantomograms) from 19 p atients (nine females and 10 males; 13-19 yea rs of age at the time of refe rral) were analysed. The ages of the patients when profile radiographs were taken for cephalometric analysis varied from 8 to 16 years. The study shows that this group of patients, compared with a reference grou p, had an increased sagittal jaw relationship (Class II). Specifically, the mandibular prognathism was less, the mandibular gonial angle smaller, the mandibular alveolar prognathism enlarged and the maxillary incisor inclinat ion less than in the reference group. Furthermore, this group of patients had a more frequent occurrence of morph ological tooth anomalies, such as root deflections, invaginations, and taur odontism. However, none of the patients with arrested eruption of M(2)inf h ad agenesis of the lower third molar. The study did not reveal an associati on between the degree of inclination of the M(2)inf and that of the first m olar in the same region. The results of this investigation show that conditions such as the craniofa cial morphology and deviations in the dentition are associated with arreste d eruption of M(2)inf. Therefore, it is important to evaluate these conditi ons in future diagnosis and treatment planning of patients with arrested er uption of M(2)inf.