The Occurrence of Fifth and Additional Molars

Abstract

The purpose of the study was to summarize the current knowledge available of fifth and additional molars, including their epidemiology, demographics of subjects and management strategies. Additionally, directions for further research are formulated. Materials and methods. The Medline database (through PubMed) and Web of Science Core Collection were searched using the following keywords: “Supernumerary molar*”, “Additional molar*”, “Fifth molar”, “Five molar*”, “Sixth molar*”, “Six molar*”, “Seventh molar” and “Seven molar*”. Additionally, the search engine Google was used using the same keywords. Moreover, the references of the literature identified using the previous methods were searched for other eligible publications. Publications were included if they described at least one fifth or additional molar in a human subject; reported on anatomical, epidemiological, demographic or clinical aspects or the full text could be sourced. Results and discussion. Fifth and additional molars have been sporadically described in literature, which is summarized in the current review. The age at detection of supernumerary molars ranged from 12 to 33 years (average: 21.8 years). When molars are present beyond a fourth, it usually only concerns fifth molars. Only one case of sixth and seventh molars was identified. Like fourth molars, they occur usually in the maxilla and unilaterally. Most of the reports did not mention any specific symptoms regarding these supernumerary molars. They were usually managed by removal or not at all. Six case reports reporting on fifth and additional supernumerary molars were included. An additional case series was identified that included three cases of a patient with fifth molars. Only two of the identified publications were published after 2010, while two were published before 1980. No prospective studies studying the entities were identified. It is clear that the body of evidence about supernumerary molars beyond a fourth is very limited in size. Additionally, the available literature is lacking both in internal and external validity. Conclusion. The body of evidence about fifth and additional molars is very sparce, with only a few case reports having been published. It is however clear that these entities are very rare and share several characteristics with fourth molars. Importantly, it seems that they are often asymptomatic and do not always require dedicated treatment. Further research is needed to better understand the epidemiology of these entities