The Evolution of Third Molars in Orthodontics: what about Anterior Dental Crowding? Systematic Review

Abstract

Background: Third molar influence on anterior crowding is controversial. However, it is assumed that they play a significant role in compromising dental arch space. Aim: To review the literature to clarify the role of third molars in anterior crowding and relapse after orthodontic treatment using a systematic review Material and methods: A systematic search was conducted based on an electronic search of several databases (Pub Med, Science Direct, Cochrane Library) covering publications from 2010 to January 2022. The search was performed using the acronym PICOS, limited to the following keywords in English and French: «wisdom tooth» OR« third molar »AND «anterior teeth crowding.» Results: Based on the keywords, 549 bibliographical references were initially identified. After the elimination of duplicate references and studies, the number of articles was reduced to 315. A review of titles and abstracts resulted in the selection of 23 articles. After reading the complete text, six articles were included in this systematic review Conclusion: No relationship between the incisors crowding and the presence of third molars was identified. Therefore, the indication for prophylactic removal of third molars to avoid incisor crowding is not justified.

Headnote

ABSTRACT

Background: Third molar influence on anterior crowding is controversial. However, it is assumed that they play a significant role in compromising dental arch space.

Aim: To review the literature to clarify the role of third molars in anterior crowding and relapse after orthodontic treatment using a systematic review

Material and methods: A systematic search was conducted based on an electronic search of several databases (Pub Med, Science Direct, Cochrane Library) covering publications from 2010 to January 2022. The search was performed using the acronym PICOS, limited to the following keywords in English and French: «wisdom tooth» OR« third molar »AND «anterior teeth crowding.»

Results: Based on the keywords, 549 bibliographical references were initially identified. After the elimination of duplicate references and studies, the number of articles was reduced to 315. A review of titles and abstracts resulted in the selection of 23 articles. After reading the complete text, six articles were included in this systematic review

Conclusion: No relationship between the incisors crowding and the presence of third molars was identified. Therefore, the indication for prophylactic removal of third molars to avoid incisor crowding is not justified.

KEYWORDS: Third molar , Wisdom tooth , Anterior teeth crowding, Relapse

INTRODUCTION

The third molars are the last permanent teeth on the dental arch. Their eruption takes place late, at the end of growth. These teeth are helpful in the anatomical, functional, and dynamic balance of the dental arches, particularly in masticatory function and maintenance of the vertical dimension.

In orthodontics, the most controversial role of the third molars is whether they can contribute to the development of malocclusion or relapse after orthodontic treatment, particularly in the anterior segment of the dental arch. Several studies have reported conflicting results.[1]

This work aims to review the articles published on the topic to clarify the role of third molars on anterior teeth crowding and relapse after orthodontic treatment, and this through a systematic review.

MATERIALS AND METHODS

Research strategy: A systematic search was conducted based on an electronic search of several databases (Pub Med, Science Direct, Cochrane Library) covering publications from 2010 to January 2022. The search was performed using the acronym PICOS and limited to the following keywords in English and French: «wisdom tooth» OR« third molar »AND «teeth crowding.»

Selection criteria:

Inclusion criteria:

- Articles published from 2010 to January 2022

- Full text accessible

- Articles published in English or French

- Original article, prospective, retrospective, longitudinal or cross-sectional studies, cohort study, case-control study, randomized control trials

- studies with human subjects only

- Studies evaluating the impact of the third molar on dental arch alignment

- Studies evaluating the relapse of anterior dental crowding after an orthodontic treatment without third molar removal

Exclusion criteria:

- A Case report

- Literature revues

- Studies including the only patient who has been removed third molars

Studies with unclear outcomes of interest

-Quality assessment:

- The selected articles were scored based on the proposed criteria "National Institutes of Health, Department of Health and Human Services, USA [2]. The risk of bias in studies was assessed independently by the authors. Any disagreement was resolved by discussion with the examiner. Among the criteria used by these authors, we find sample randomization, comparison between the effects of the intervention, validation of measures, inclusion and exclusion criteria, and statistical analysis. Regarding the risk of bias for each study analyzed, the documents containing all the above-mentioned points (9-13) were rated as "low risk," those for which the number of points in between (6-8) were rated as "medium risk," a "high risk "is assigned to studies that meet or less than five criteria. (table 2 ). The six studies included in our review present a low risk of bias .

RESULTS

Based on the keywords, 549 bibliographical references were initially identified. After the elimination of duplicate references and studies, the number of articles was reduced to 315. A review of titles and abstracts resulted in the selection of 23 articles. After reading the complete text, six articles were included in this systematic review. (table 3)

DISCUSSION

Relapse of anterior crowding is a phenomenon that frightens orthodontists following orthodontic treatment and inevitably occurs in most treated cases.

The claim that the 3rd molars are the main cause of this relapse is still widespread among patients and practitioners, sometimes leading to their prophylactic removal.

Several authors have been interested in the causes of relapse following orthodontic treatment, especially due to the wisdom tooth, which remains a subject of controversy. [9]

In most studies, dental crowding was determined using Little's (1975) irregularity index. This index represents the linear displacement of each incisor's anatomical contact points (as distinguished from the clinical contact points) of the adjacent tooth's anatomical contact point. The sum of these five displacements represents the relative degree of anterior irregularity. An index score of 0-0.9 mm is ideal, between 1-3.9 mm is considered minimal, between 4-6.9 mm is moderate, from 7-9.9 mm is severe and a score of more than 10 mm is extreme [10]. Notably, Cortin et al. in 2019[3], Stanaityte et al. in 2014 [5] and Hasgow et al. in 2013 [6] all opted for the Little irregularity index for the measurement of dental crowding. All reported that there is no statistically significant difference in incisor crowding relapse in the two groups of patients (with and without wisdom tooth extractions), thus corroborating the results found by Bruschang et al. in 2003[10], Lidauer et al. in 2007 [11]and recently,Genest-Beucher in 2018[12]. They concluded through their literature review that 83% of articles did not find any significant relationship between the presence of third molars and anterior teeth crowding. Likewise. the study by Esan T et al. in 2017 [4] reported no statistically significant difference in Little irregularity index comparison when third molars have completely erupted in the evaluated stages and periods. In other words. the amount of relapse after the retention period was similar between the groups with and without third molars. These results show that relapse occurs regardless of third molars presence or absence. This result agrees with the study done by Okazaki et al. in 2010[13], who investigated interproximal force change in the anterior teeth of the lower jaw and the effect of the erupting third molars in 40 treated patients. He followed them for 18 months during the retention phase. His finding also revealed that the erupting third molar did not affect the total interproximal. However. Esan T et al. in 2017 [4] also mentioned in their study that there is a statistically significant correlation between the inclusion of wisdom teeth and dental crowding. and Karasawa et al. in 2013 [7] evaluated three hundred subjects with a mean age of 20.4 years on the presence or absence of wisdom teeth and incisor crowding. They also found no statistically significant association between the presence of upper and/or lower third molars and anterior teeth crowding. Their conclusions stated that evidence on the role of third molars as an etiologic factor in the late lower arch crowding is lacking. Still. these results do not agree with those mentioned by Hasagowa. et al. in 2013[6] reported no significant correlation between the inclusion of wisdom teeth and anterior crowding.

This discrepancy in results can be explained by the differing work methodology, sample size, and the orientation and degree of inclusion of the wisdom teeth. Therefore, we can say that third molars do not cause tooth crowding, as there is always more than one factor influencing it. Wisdom teeth are only one of many factors that may cause crowding.

In orthodontics, the extraction of wisdom teeth is indicated in cases of posterior crowding and distalization of the arch or when their unfavourable orientation compromises the stability of the arch. Therefore, it is not justified or recommended to have wisdom teeth extracted, whether impacted or not, for the sole purpose of preventing the occurrence of dental overlap [14].

CONCLUSION

The results of our work elucidated that there is no relationship between incisor crowding and the presence of third molars. Thus, we can suggest that prophylactic removal indication of the third molars to avoid incisors crowding is not justified.

ACKNOWLEDGMENTS

None.

AUTHORS' CONTRIBUTIONS

The participation of each author corresponds to the criteria of authorship and contributorship emphasized in the Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly work in Medical Journals of the International Committee of Medical Journal Editors. Indeed, all the authors have actively participated in the redaction, the revision of the manuscript, and provided approval for this final revised version.

COMPETING INTERESTS

The authors declare no competing interests with this case.

FUNDING SOURCES

None.

Sidebar

Copyright © 2022 Assali A et al. This is an open access article distributed under the Creative Commons Attribution 4.0 International, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

References

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