Prophylactic removal of unerupted asymptomatic third molars : is it justifiable ?

Objective: to review the literature currently available on the evidence that does or does not justify the prophylactic extraction of unerupted asymptomatic third molars. Material and Methods: the electronic databases PubMed, Capes Periodicals, Web of Science and Scopus were searched from November to December 2016 by two authors, simultaneously, using as search terms: Terceiro Molar/Molar, Third AND Extração Profilática/Prophylatic Removal OR Prophylatic Extraction. We included articles from original research and clinical trials published in English and Portuguese. No limits were applied to the date of publication. Review articles and clinical case reports were removed. Results: we identified 13 studies that addressed, at some aspect, the prophylactic removal of unerupted asymptomatic third molars. The results of this literature review which alluded to the potential for the formation of pathological alterations in asymptomatic third molars are conflicting; While some justifies the prophylactic procedure based on the possible formation of associated lesions, other scientific evidence does not support such practice. Conclusion: in view of the conflicting viewpoints found in the literature, the prophylactic removal of asymptomatic third molars requires case-by-case evaluation of each patient, and the decision-making process, regarding the retention versus the prophylactic removal of these teeth should be based on scientific evidence combined with the clinical experience of the professional.


Introduction
T he extraction of third molars is one of the most common procedures in the clinical practice of dentists worldwide.It is estimated that, in the United States, approximately 10 million impacted teeth are extracted annually from approximately 5 million individuals, generating a revenue of 3 billion dollars. 1,2In England and Wales, extractions of third molars between 1995 and 1996 totaled approximately 5.2 million pounds. 3rophylactic extraction, the most common reason for extraction of third molars, 4 is widely recognized by a considerable number of dental surgeons. 2,56][17][18][19][20][21] However, other studies suggest that the lower third molars should not be removed prophylactically in some cases 2,14,[22][23] and vigilant monitoring of these teeth is more appropriate strategy. 24ebate about indications for prophylactic removal of im-pacted third molars remains heated. 11The decision-making process regarding retention versus prophylactic removal of these teeth should be based on the available scientific evidence. 25However, the literature is lacking in studies to support adequate clinical decision-making regarding prophylactic extraction of third molars. 14This study aimed to review the literature currently available on scientific evidence that does or does not justify the prophylactic extraction of unerupted asymptomatic third molars.

Material and Methods
For the purpose of this study, we followed guidelines provided by Moher et al. 26 in Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement.

Identification and Selection of Relevant Research
An exploratory bibliographic search was conducted from January to February of 2017 using the electronic databases: Public Medline (PubMed), Periódicos da Capes, Web of Science and Scopus.Two authors performed the search employing the term Third Molar in combination with Prophylactic removal OR Prophylactic Extraction (

Scopus
Studies were identified and duplicates were removed.Subsequently, titles and abstracts were screened for relevance, considering the exclusion criteria.Next, the remaining studies were obtained in full-text and were screened using the self-same criteria, the eligible the ones being included in this review.We removed review studies, clinical case reports, articles not available in fulltext, and publications that did not address the prophylactic remo-val of unerupted asymptomatic third molars.Eligible studies also had their reference lists screened following the specified criteria for the eligible ones.

Data Collection and Analyses
All the selected articles addressed the relationship between third molars and pathological changes and included the following parameters: authorship, year of publication, country of publication, type of study, sample size (and age), outcomes measured, relevant data and results, and study considerations.
Based on the findings of the studies, we determined the following themes for critical analysis of the results: characteristics of the studies, prophylactic removal of third molars and implications for practice.Yet, considering our study design and its findings, we presented the section "study limitations".

Results
For this systematic review, the initial electronic search yielded a total of 540 titles found in the databases: PubMed, Periódicos da Capes, Web of Science and Scopus.433 studies were excluded for duplication and the remaining 107 unique papers were screened for relevance to this study.55 publications were excluded after reading their titles and abstracts.Then, the 52 remaining documents were obtained in full-text and assessed for eligibility in consideration of the prophylactic removal of unerupted asymptomatic third molars.After reading the documents in full text, 13 studies were included (Figure 1 and Table 2).No studies from reference lists were added due to their either not being eligible or not having come up on the database search.About one-third of the teeth had to be removed within 5 years.Although this does not allow for a "life extrapolation", this questions the current thinking boundary on asymptomatic ITMs and certainly suggests that more (possibly long-term) studies need to be completed.
There seems to be little cost-benefit when it comes to the prophylactic removal of asymptomatic third molars, but it was not possible to project this with absolute certainty.The prevalence of distal caries of the second molar in the population was 20%.This prevalence was 47% when the third molar presented angulation of 31-708 (mostly mesioangulated third molars) and 43% in 70-908 (all third molars horizontal).The point of contact at the cementoenamel junction of the second molar and the increase in age had significant effects on the formation of caries.
The results revealed that the distal caries of the second molar justify the prophylactic removal of the third molar and the partially erupted third molars that have an angulation of 30-908 with a point of contact at the cementoenamel junction should be removed to prevent distal caries of the second molar.
According to our findings, we identified only six studies published at sporadic intervals within a ten-year

Prophylactic Removal of Unerupted Asymptomatic Third Molars
Table 2 presents the main findings of all the 13 selected articles that addressed the prophylactic removal of unerupted asymptomatic third molars and included the following parameters: authorship, year of publication, country of publication, type of study, sample size (and age), outcomes measured, relevant data and results, and study considerations.

Implications for Practice
In recent years, the shift in emphasis to nonintervention in patients with asymptomatic impacted third molars has been accompanied by a considerable debate. 37The supporters of prophylactic removal argue that the benefits outweigh the risks.Nonetheless, the scientific evidence is too inconclusive to support prophylactic removal.Unfortunately, most of the clinical research has failed, leading to contradictory interpretations that have not completely clarified the relative risks and benefits of early intervention. 38onflicting reports persists surrounding to the incidence of pathological conditions associated with impacted third molars, and the subsequent need for prophylactic removal.The data remain limited regarding the long-term effects of unerupted third molars on adjacent teeth. 32According to Hicks, 38 unreliable data would serve only to fuel this debate and the controversy over proper protocols.
It is likely that disagreements persists on which clinical recommendations should be followed when considering the prophylactic removal of asymptomatic third molars. 39Therefore, the decision to perform prophylactic removal of these teeth should be based on the probability of retained third molars causing future problems. 30hus, the prophylactic removal of asymptomatic third molars requires individual care and case-by-case evaluation of each patient and the decision-making process regarding the retention versus prophylactic removal of these teeth should be based on the available scientific evidence combined with the professional's clinical experience.

Study Limitations
This literature review has some limitations given that the literature is lacking in randomized clinical trials regarding of the prophylactic removal of unerupted asymptomatic third molars.
Other limitation found by the authors was the lacking in some full texts publications.However, available scientific evidence were included in order to better work on the subject.Sample sizes found in most studies were acceptable.

Discussion
Prophylactic removal of unerupted asymptomatic third molars is defined as a surgical procedure in which the patient does not present or has not presented any symptoms or pathologies associated with unerupted third molars. 29Currently, there is no general agreement as far as the necessity of surgical removal of asymptomatic third molars is concerned.
In order to minimize the risk of disease associated with these teeth 30 or to avoid complications at more advanced ages, due to the risk of trauma or mandibular fractures, 11,40 development of cysts and tumors, 36 patient's recovery and prognosis, 41 some authors believe that all unerupted third molars should be removed.Nevertheless, in this sense, there is still a need to compare the morbidity rates of tooth removal in people of several age groups. 37ccasionally, orthodontists propose the removal of asymptomatic third molars to complete orthodontic therapy. 30Despite the fact that the role of third molars has been the subject of research, clinical interest, and debate for years, there is still a lack of scientific evidence from high-quality clinical studies on this subject. 42However, Normando et al. 43 suggest that, in general, the best clinical conduct is not to proceed with the prophylactic extraction of third molars, except in situations where removal of a third molar is mandatory from the beginning of treatment.
Other studies do not support such clinical conduct, 17 considering that, even with the risk of occurrence of lesions 13 , which was relatively low, 30 the relationship between pathological changes and dental position was not statistically significant, and that it was not possible to come up with a significant cost-benefit relationship. 28ccording to some authors, 28,32 caries in the distal region of the second molar seem to be a factor that justifies the extraction of asymptomatic third molars, especially if the tooth is mesiongulated. 32However, given that distal caries in the second molars is not very common in cases of third molar impactions, the prophylactic removal of these impacted teeth may not be considered appropriate. 35n this sense, in the absence of any other indication, the presence of radiologically diagnosable retention is not sufficient indication for the prophylactic removal of an asymptomatic third molar. 27This is specially true given the lack of evidence from randomized clinical trials that this procedure would avoid painful or infectious pathological complications due to its retention. 25

Conclusion
There is some disagreement regarding the prophylactic extraction of unerupted asymptomatic third molars.Some authors justify the prophylactic removal based on the potential of development of pathological changes while other available scientific evidence does not support such conduct.
The routine removal of unerupted asymptomatic or disease-free third molars will require individual care and assessment.A case-by-case management protocol is needed.The close monitoring of these teeth may be an acceptable option.
The decision-making process regarding the retention versus prophylactic removal of unerupted asymptomatic third molars should be based on the available scientific evidences combined with the professional's clinical experience.

removal of unerupted asymptomatic third molars: is it justifiable?Table 1 .
). Inclusion criteria were: original research articles and clinical trials published in Portuguese and English.No limits were applied to the year of publication.Search strategy for all databases Participants were examined dentally at ages 18 and 26 years.Panoramic radiographs were taken at age 18, but not at age 26.For each tooth, the impaction at 18 years was compared with clinical status at 26 years of age.Out of the 2857 third molars evaluated at 18 years of age, 92.8% were clinically evaluated at age 26.Approximately 54.9% of teeth that were not affected by age 18 had erupted at age 26.Of the teeth that were impacted at 18, 33.7% had fully erupted at 26, 31.4% were extracted, and 13.1% were not.In addition to horizontally ITM, a substantial proportion of other types of impaction completely erupt, and apparent radiographic impaction in the late adolescence should not be sufficient reason for its prophylactic removal in the absence of other clinical indications.

Table 2 .
Results of literature review displayed in chronological order TMI= Impacted Third Molars.PRTM = Prophylactic Removal of Third Molars; CBCT = Cone Beam Computer Tomography.Prophylactic removal of unerupted asymptomatic third molars: is it justifiable?