Does an Association Exist Between the Presence of Lower Third Molar and Mandibular Angle Fractures?: A Meta-Analysis

Accepted Manuscript Is there association between the presence of lower third molar and mandibular angle fractures: a meta-analysis? Wagner de Sousa Ruela, Vinícius Lima de Almeida, Luciana Monti Lima-Rivera, Pâmela Letícia dos Santos, André Luís Porporatti, Paulo Henrique Luiz de Freitas, Luiz Renato Paranhos PII:

S0278-2391(17)30624-9

DOI:

10.1016/j.joms.2017.06.008

Reference:

YJOMS 57844

To appear in:

Journal of Oral and Maxillofacial Surgery

Received Date: 30 January 2017 Revised Date:

5 June 2017

Accepted Date: 5 June 2017

Please cite this article as: de Sousa Ruela W, de Almeida VL, Lima-Rivera LM, dos Santos PL, Porporatti AL, de Freitas PHL, Paranhos LR, Is there association between the presence of lower third molar and mandibular angle fractures: a meta-analysis?, Journal of Oral and Maxillofacial Surgery (2017), doi: 10.1016/j.joms.2017.06.008. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Is there association between the presence of lower third molar and mandibular angle fractures: a meta-analysis? Wagner de Sousa Ruela1, Vinícius Lima de Almeida2, Luciana Monti Lima-Rivera3, Pâmela Letícia dos Santos4, André Luís Porporatti5, Paulo Henrique Luiz de Freitas6, Luiz Renato

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Paranhos6

PhD in Oral Biology - Sagrado Coração University (USC), Bauru, SP, Brazil.

2

Dental student, Federal University of Sergipe at Lagarto, SE, Brazil.

3

DDS, MSc, and PhD in Pediatric Dentistry. Professor at the Sagrado Coração

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1

University (USC), Bauru, SP, Brazil.

DDS, MSc, and PhD in Oral and Maxillofacial Surgery and Traumatology. Professor

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4

at the Sagrado Coração University (USC), Bauru, SP, Brazil. 5

DDS, MSc, PhD. Professor, Department of Dentistry - Federal University of Santa Catarina, Florianópolis/SC, Brazil.

6

DDS, MSc, PhD. Professor, Department of Dentistry, Federal University of Sergipe at Lagarto, SE, Brazil.

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CORRESPONDING AUTHOR: Pâmela Leticia dos Santos

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Post-Graduate Department - Sagrado Coração University - Irmã Arminda, 10-50. Jardim Brasil – Bauru – São Paulo - Brazil - 17011-160

Phone: +55-16-981541577

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14-21077000 E-mail: [email protected] Declaration of interest

Conflicts of interest: none

Fax: +55-

ACCEPTED MANUSCRIPT ABSTRACT Purpose: The current literature suggests that the presence of lower third molars predisposes to a higher risk of mandibular angle fracture. Thus, this review aims to answer the following question: “Is there an association between the presence of lower third molar and mandibular

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angle fractures in adults?”, as well as to assess the influence of third molar position according to Pell and Gregory. Material and methods: the present study is a systematic review and meta-analysis on analytical observational studies. The study population was composed of all

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publication on the relationship between mandibular angle fracture and the lower third molar. There was no restriction of year, language, and publication status. The review protocol was

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registered at the PROSPERO database (CRD42016047057). Electronic searches unrestricted for publication period and language were performed in the PubMed, Scopus, SciELO, LILACS databases. Google Scholar and Open Grey databases were used to search the “grey literature”, avoiding selection and publication biases. The entire search was performed by two

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eligibility reviewers. Association and proportion meta-analyses were planned for the studies with sufficient data. The primary predictor variable was the relationship between the presence of lower third molar and the development of mandibular angle fractures. The secondary

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outcome variables were the vertical and horizontal positions of the lower third molar,

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according to the classification by Pell and Gregory and their relation to the susceptibility to developing mandibular angle fracture. Results: the search strategies resulted in a set of 411 studies, from which 16 were selected for qualitative and quantitative review. Association meta-analysis included all the selected studies and showed that patients with lower third molars are 3.16 times more likely to develop mandibular angle fractures. Proportion metaanalysis included five studies and showed that the overall rate of mandibular angle fractures was 51.58% and that positions III and C are more likely to cause fracture, with rate of 59.84 and 63.67%, respectively. Conclusions: this study showed that the presence of impacted third

ACCEPTED MANUSCRIPT molars increases by 3.16 times the risk of mandibular angle fractures in adults, with the highest risk present when third molars are classified as IIIC according to Pell and Gregory. The available evidence is not sufficiently robust to determine third molar presence or level of

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Keywords: Fractures; Mandible; Third Molar.

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impaction as the main causative factors for mandibular angle fractures.

ACCEPTED MANUSCRIPT INTRODUCTION While being one of most resilient bones of the facial skeleton, mandible fractures occur quite often. In fact, mandibular fractures represent 45 to 60% of all facial fractures,1-3 and the mandibular angle is involved in 25 to 33% of those fractures.4 Thus, evidence-guided

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management of these injuries, as well as evidence-based information on the causative and risk factors are essential for providing the best possible care to our patients – especially when elective surgery is considered.

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The mandibular angle forms the transition between the mandibular body and the ascending ramus, where unerupted or partially erupted third molars are usually nested.4 By

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occupying an area that should be filled with bone, these teeth affect the local distribution of traumatic forces, which may render the region more susceptible to fractures.5 Indeed, it has been reported that the presence of a lower third molar, either unerupted or partially erupted, makes the mandibular angle two to three times more likely to fracture.1 Not surprisingly,

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some authors have advocated the prophylactic removal of lower third molars as means to prevent mandibular angle fractures.6

There is still concern about the quality of the available evidence, since studies with

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different designs can produce contradicting results. Indeed, some authors have reported on the higher frequency of condylar fractures in patients without lower third molars7-8, while Lee

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and Dodson9 suggested that deeply impacted lower third molars actually reduce the risk of mandibular angle fractures. This study aimed to answer the following focused question: “Does the risk of

mandibular angle fractures increase (outcome of interest) depending on the presence and position of third molars (intervention of interest) of young adults (patient sample) when compared to young adults without third molars (control group or treatment)?” The researchers accept the hypothesis that the presence of the lower third molar increases the risk

ACCEPTED MANUSCRIPT of fractures in the mandibular angle region. The specific aims of the present study were: 1) to correlate, through association meta-analysis, the presence or absence of lower third molar with episodes of mandibular angle fractures; and 2) to analyze, through proportion metaanalysis, the relationship between vertical and horizontal positions of the lower third molar

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and the risk of mandibular angle fractures.

METHODS

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Study design

To address the research objectives, the researchers designed and implemented a

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systematic review and meta-analysis according to the Cochrane Collaboration guidelines10 for systematic reviews and the PRISMA Statement11 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The review protocol was registered at the PROSPERO database (CRD42016047057). The systematic review was structured according to the

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recommendations by Dodson12.

The study population was composed of all publication on the relationship between mandibular angle fracture and the lower third molar until July 31, 2016. There was no

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restriction of year, language, and initial date of publication.

Study Sample

For inclusion in the study sample, the publications had to present the following

inclusion criteria: 1) the study was a retrospective cohort that included an analysis of the relationship between mandibular angle fractures and the presence of the lower third molar; and 2) there was quantitative data available on lower third molar presence and/or its position in the mandibular arch according to the classification proposed by Pell and Gregory13.

ACCEPTED MANUSCRIPT The publications were excluded from the analysis if they presented some of the following exclusion criteria: 1) studies in children and adolescents; 2) studies with insufficient data regarding the association of lower third molar presence with mandibular angle fractures; 3) studies that excluded patients without lower third molar and analyzed the

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incidence of mandibular angle fracture without such a control group; and 4) case reports, letters to the editor and/or editorials, literature reviews, indexes, and abstracts.

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Study Variables

The primary predictor variable was the relationship between the presence of lower

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third molar and the development of mandibular angle fractures. The secondary outcome variables were the vertical and horizontal positions of the lower third molar according to the classification by Pell and Gregory13 and their relation to the susceptibility to developing mandibular angle fracture.

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For the sake of clarity, the definition of mandibular angle fracture proposed by Kelly and Harridan4 was used, which is that of a fracture posterior to the second molar extending from any point formed by the junction between body and ramus of the retromolar area up to

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any point of the curve established between the lower margin and posterior portion of the mandibular ramus.

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The classification by Pell and Gregory13 ranks teeth based on the relation with to the

ascending mandibular ramus (horizontal analysis) and the depth of inclusion in the mandibular bone (vertical analysis). Horizontally, lower third molars are classified as (Figure 1)14: •

Class I - adequate space in front of the ascending mandibular ramus to accommodate the crown of the dental element;

•

Class II - the tooth is partially within the ascending mandibular ramus; and

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Class III - most of the tooth is within the ascending mandibular ramus.

Vertically, lower third molars are classified as (Figure 1)14: •

Class A - the crown of the third molar is at the same level of occlusion of the lower second molar; Class B - the crown of the lower third molar is between the occlusal surface

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•

and the cemento-enamel junction of the lower second molar; and

Class C - the crown of the lower third molar is below the cemento-enamel junction of the lower second molar.

Data Collection and Management

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•

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A computerized systematic search was conducted in PubMed (including MedLine), Scopus, SciELO, and Latin American and Caribbean Health Sciences (LILACS). Google Scholar and Open Grey were used to search the "grey literature". For Google Scholar the search was restricted to the first 100 most relevant results, excluding patents and citations.

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The “grey literature” is usually searched to retrieve articles potentially published in nonindexed journals, dissertations, and theses, in order to avoid selection and publication biases. Furthermore, the reference lists of the selected articles were hand-searched for any additional

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references that might have been missed in the electronic searches.

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The MeSH (Medical Subject Headings) keywords "third molar", "impacted", "mandibular angle", and "fracture" were the terms selected for the electronic searches. All searches were performed from the earliest records of each database up to July 2016. The results obtained were exported to the Mendeley™ Desktop 1.13.3 software (Mendeley™ Ltd, London, England), where duplicates were removed. Appendix 1 presents keyword details and word truncation for each database. Study selection was performed in two phases. In phase I, two reviewers (VLA and WSR) independently screened titles and abstracts of the studies identified in all electronic

ACCEPTED MANUSCRIPT databases. Reviewers were blind to author and journal names. When titles fulfilled the eligibility criteria but no abstracts were available, the full text was obtained and analyzed. In phase two, the full texts of preliminarily eligible studies were evaluated to verify whether they fulfilled the eligibility criteria. In specific cases, when the study with eligibility

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potential presented incomplete data, the authors could be contacted by e-mail in search of more information. Disagreements between reviewers were solved through discussion until consensus; a third reviewer (PHLF) was involved when consensus was not reached.

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One reviewer (VLA) collected the required information from the selected articles and a second reviewer (WSR) cross-checked the information to confirm the quality of data

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extracted. Any disagreement was solved after discussion with a third reviewer (PHLF). A fourth reviewer (LRP) was involved when further assistance was required for the final decision.

Extracted data included authorship, year of publication, study location, sample size,

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number of patients with or without lower third molars, impaction level according to Pell and Gregory,13 and rate of mandibular angle fractures. Methodological quality and risk of bias of the studies included were assessed by two

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independent reviewers according to the PRISMA guidelines.11 This assessment prioritized the

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clear description of information and it was performed blindly, hiding the names of authors and journals, and avoiding any potential bias and conflict of interests. The critical appraisal tool for studies from the Meta-Analysis of Statistics Assessment and Review Instrument (MAStARI) was chosen to guide the assessment15, based on nine criteria expressed as the following questions (Q): Q1 - Was the study based on a random or pseudorandom sample?; Q2 - Were inclusion criteria for the sample clearly defined?; Q3 - Were confounding factors identified and strategies to manage them stated?; Q4 - Were outcomes assessed with objective criteria?; Q5 - Was there sufficient description of the groups for conducting

ACCEPTED MANUSCRIPT comparisons?; Q6 - Was the follow-up carried out over a sufficient time period?; Q7 - Were the outcomes of people who withdrew from the study described and included in the analysis?; Q8 - Were the outcomes measured in a reliable way?; Q9 - Was an appropriate statistical analysis used?.

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Risk of bias was classified as high when the study reached up to 49% of “yes” answers, moderate when the study reached 50 to 69% of “yes” answers, and low when the study reached over 70% of “yes” answers.

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Data Analyses

The relationship between lower third molar presence or absence and the occurrence of

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mandibular angle fractures were the main outcomes assessed. The summary measure considered odds ratios (ORs) in dichotomous variables at 95% confidence intervals (CIs). The secondary outcome was fracture rate based on Pell and Gregory’s classification13. Two types of meta-analyses (association and proportion) were performed after the

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selection of studies with sufficient data. Fixed and random effects analyses were performed following the appropriate Cochrane guidelines.16 Heterogeneity was calculated by means of the inconsistency index (I2). A value higher than 50% was considered an indicator of

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substantial heterogeneity between studies, which suggests the need for random effects model

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analysis. Significance level was set at 5%.16 An association meta-analysis between lower third molar and fracture occurrence was

planned. If no summary measures were reported, they were calculated for each study to describe the observed effect. The estimation of summary effect was calculated as a pooled mean of odds ratio (OR) effects. Forest plots were generated with the Review Manager 5.3 software (RevMan 5.3, Copenhagen, Denmark) provided by the Cochrane Collaboration.17 In addition, a proportion analysis was planned on the percentage of fractures based on the horizontal (I, II, and III) and vertical (A, B, and C) impaction levels according to Pell and

ACCEPTED MANUSCRIPT Gregory.13 This meta-analysis was performed with the MedCalc Statistical Software version 14.8.1 (MedCalc Software, Ostend, Belgium). The risk of bias across studies was regarded to an overall risk the study results may present, on which could influence meta-analysis data. Clinical heterogeneity was assessed by

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comparing the variability among the participants’ characteristics and the outcomes studied. Methodological heterogeneity was calculated by comparing the variability in study design and risk of bias. Statistical heterogeneity was determined by comparing the variability of

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intervention effects among the studies included.

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RESULTS

The search strategies resulted in a set of 411 studies. After initial screening, 204 duplicate results were eliminated and 207 studies remained for the reading of titles and

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abstracts. From these, 116 articles were outside the objective of the study, 36 were literature reviews, 28 were case reports, and 2 were letters to the editor. The full text of the 25 remaining studies were analyzed, with three articles being excluded for not counting patients

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without lower third molar and for analyzing the development of mandibular angle fracture without such control group. Six articles were excluded for providing just the number of teeth

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involved in the fractures or the number of mandibular angles fractured, and three articles were excluded for not using a control group (Appendix 2). Therefore, only 16 studies were selected for the present qualitative and quantitative review. Figure 2 shows a flowchart of the process.

All the included studies were published in English. Four were performed in India, 1820,21

three in the USA,1,3,9 two in Japan,7,22 one in Jordan,23 one in Nigeria,24 one in

Germany,25 one in Turkey,26 one in China,27 one in Canada,28 and one in Korea.29 All studies

ACCEPTED MANUSCRIPT were conducted between 1995 and 2015. Table 1 summarizes the descriptive statistics of the included studies. When relevant data were available, the level of third molar impaction was classified according to Pell and Gregory.13 Table 2 details the relationship and frequency of mandibular

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angle fractures according to horizontal and vertical impaction levels. Only five out of the 16 studies included provided sufficient data for this analysis. Only two studies3,9 detailed the combinations of vertical and horizontal positions of the lower third molar according to the

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classification by Pell and Gregory (Table 3).

All studies included were classified as observational and analytical, and all of them

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assessed the presence or absence of the lower third molar and the occurrence of mandibular angle fracture by means of panoramic radiographs. All studies, except for one by Ugboko et al.24, showed that patients with lower third molar were more likely to have mandibular angle

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fractures.

Risk of bias within studies

The individual risk of bias assessment among studies showed that all studies assessed

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presented low risk of bias. Eleven studies18,20-29 did not present data on the level of impaction

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of lower third molars according to the classification by Pell and Gregory.13 This type of data is more objective and favors the establishment of associations between presence and position of lower third molars and mandibular angle fracture. Consequently, the results of the aforementioned studies exposed in the present review could not be included in the analysis. Thus, considering that the lower third molar may take on several positions in the dental arch and that these positions may have different influences on the development of mandibular angle fractures, it may be said that only the studies displayed in Table 2 showed accurate results. Table 4 presents the results of risk of bias assessment.

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Synthesis of results The association meta-analysis was performed with 16 of the selected studies. Heterogeneity among the studies was 86%; therefore, a random effects model was chosen.

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Results showed that the OR of mandibular angle fractures is 3.16 in patients with lower third molars (95%CI=2.20-4.54) (Figure 3).

The proportion meta-analysis was performed with five of the selected studies.

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Heterogeneity among the studies ranged from 92.06 to 99.02%, and a random effects model was used. Among the studies analyzed, the results showed that the overall rate of fractures

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was 51.58% (95%CI 37.32 to 65.71; total sample: 5145). Horizontal impaction classes I, II, and III showed rates of 50.83, 58.68, and 59.84%, respectively. Vertical impaction classes A, B, and C showed rates of 47.92, 54.9, and 63,67%, respectively (Figure 4).

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DISCUSSION

The main objective of this study was to verify, through the comparison meta-analysis, the association between the presence of the lower third molar and the risk of developing

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mandibular angle fractures in adults. The hypothesis was that the presence of the lower third

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molar would predispose to higher risk of mandibular angle fractures. The secondary outcome evaluated in this research was the relationship of mandibular fractures with the position of the third molar included by means of proportion meta-analysis. The results of this research showed that patients with lower third molars are 3.16

times more likely to experience mandibular angle fractures, thus accepting the study hypothesis. Additionally, the III and C positions are more likely to cause fracture, with rate of 59.84 and 63.67%, respectively.

ACCEPTED MANUSCRIPT The presentation of one mandibular fracture may vary as a function of the point, angle of incidence, or direction of the traumatic force, and it is also influenced by the distribution and proportion of cortical and marrow bone, volume of facial soft tissues, and presence or absence of lower third molars.3,5 According to Yadav et al.,30 factors such as the distance

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between lower third molars and mandibular lower cortical bone, as well as the amount of bone tissue at the angle region are related to mandibular fracture risk. Thus, as proposed by Baykul et al.,31 we agree that cortical bone disruption may weaken the mandibular angle, thus

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increasing the potential for fracture when traumatic forces are present. On the other hand, Lee and Dodson9 disagreed, because the results of their study did not show statistically significant

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differences in the incidence of mandibular fractures with either unerupted or erupted lower third molars.

Several studies support the results of our meta-analysis in the sense that patients with third molars were shown to be 1.73 to 4.1 times more likely to experience mandibular angle

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fractures when compared to patients without third molars.1,3,18,20,25-26 Alternatively, Ugboko et al.24 suggested that third molar presence alone may not be the most important risk factor for mandibular angle fractures; according to their results, the position of the tooth in relation to

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the mandibular bone is more of an influencing factor, given that angle fractures were more

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prevalent in patients with unerupted lower third molars than in those with erupted ones. In contrast, other authors reported on a higher relative risk of mandibular angle fractures when the third molar was partially within the mandibular ramus20-21,27,29-30 and positioned between the occlusal surface and the cemento-enamel junction of the second molar3,20-21,25,29-30, that is, Pell and Gregory’s class IIB. According to Fuselier et al.,3 these findings could be explained by the diminished bone quantity in the upper mandibular cortex when the third molar is partially erupted. Although there have been reports suggesting that mandibular angle fractures occur more frequently when lower third molars are in class IIIC,19,23 the relationship

ACCEPTED MANUSCRIPT between level of impaction (horizontal and vertical) and angle fracture remains controversial. Our opinion is that that the quality and quantity of mandibular angle bone also affect how forces are distributed in that area. Strikingly, Iida et al.7,25 showed that neither the presence nor the position of the third

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molar alone influence the incidence of mandibular fracture. Their work showed that the stage of root formation and tooth angulation affect load distribution in the mandibular angle and ramus. According to Caputo and Standle,32 the forces concentrate in regions of acute angle

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and areas with distinct elastic coefficients. Indeed, Takada et al.,33 suggested that the apical region of unerupted third molars combine these two conditions and may affect stress

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distribution along the mandibular base and angle. On the other hand, third molar absence promotes better stress distribution and dissipation across the mandibular bone. One must bear in mind, however, that other relevant factors play a causative or modifying role in the occurrence of mandibular angle fractures. As suggested by Fuselier et

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al.,3 mandibular fractures occur when bone resistance is overthrown by traumatic forces. Muscle contractiveness, proportion of cortical vs. trabecular bones, and presence of lower third molar are all factors that, when combined, can be determinants of mandibular fracture

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pattern and location.

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This systematic review and association meta-analysis may infer that there was an increase in the risk of mandibular fracture angle in patients with lower third molars. This is a relevant factor for oral surgeons for the opportunity to suggest, as other authors1-2, that prophylactic extraction of third molars is an indication for reducing the risk of mandibular fractures, especially for practitioners of contact sports and for young adults. On the other hand, it was noted the shortage of cohort retrospective studies assessing the influence of position of the lower third molar on this type of fracture. The inclusion of imaging

ACCEPTED MANUSCRIPT examinations for properly diagnosing the position of lower third molars in further studies could allow more solid conclusions.

CONCLUSION

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This study showed that the presence of impacted third molars increases by 3.16 times the risk of mandibular angle fracture in adults, with the highest risk present when third molars are classified as IIIC according to Pell and Gregory. Still, these conclusions were drawn from

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observational studies with relatively small samples. Considering that other relevant factors play a causative or modifying role in the occurrence of mandibular angle fractures, we

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conclude that the available evidence is not sufficiently robust to determine third molar presence or level of impaction as the main causative factors for mandibular angle fractures.

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ACCEPTED MANUSCRIPT FIGURE LEGENDS Figure 1 – Classification of the position of third molars according to Pell and Gregory13 (adapted from Marzola & Pagliosa, 2010)14 Figure 2 - Specific process of methods with the numbers of included and excluded articles.

molar and the development of mandibular angle fracture.

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Figure 3 - Forest plot evidencing the relationship between the presence of the lower third

Figure 4 – Proportion meta-analysis showing horizontal and vertical positioning (Pell &

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Gregory, 1933)13 of the lower third molar and their relation to the development of mandibular

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angle fracture.

ACCEPTED MANUSCRIPT TABLES Table 1 - Association between the presence or absence of lower third molar and mandibular angle fracture. Patient sample

Presence of lower third molar*

Mandibular angle fracture*

Absence of lower third molar*

Tevepaugh and Dodson, 1995

101

73

30

28

90

80

45

367

249

615

426

490

1210

Yamada et al., 1998

Lee and Dodson, 2000

127

189

25

+

408

65

82

11

-

837

269

373

57

+

189

100

157

23

+

218

161

67

57

11

+

41

26

14

15

2

+

700

370

152

330

45

+

154

136

49

18

3

+

TE D

346

AC C

Iida et al, 2004

+

+

EP

United States

0

20

Nigeria Fuselier et al., 2002

+

118

Jordan Ugboko et al., 2000

3

79

United States Ma’aita and Alwrikat, 2000

10

M AN U

Japan

SC

United States

Mandibular Outcome angle fracture*

RI PT

Authorship, year, and country of the study

Japan

Iida et al., 2005 Germany

Metin et al., 2007 Turkey Duan and Zhang, 2008 China Rajkumar et al., 2009

ACCEPTED MANUSCRIPT India Subbasbraj, 2009

2033

1466

394

567

138

+

460

260

150

200

50

+

385

221

135

164

31

+

446

233

163

213

84

+

64

57

23

3

+

India Thangavelu et al., 2010

Choi et al., 2011 Korea Naghipur et al., 2014

Kumar et al., 2015

7

M AN U

India

SC

Canada

RI PT

India

* number of patients; +, patients with lower third molar were more prone to mandibular angle fractures; -, the presence of the lower third molar is not necessarily related to mandibular angle

AC C

EP

TE D

fractures.

ACCEPTED MANUSCRIPT Table 2 - Relationship between lower third molar presence (according to the classification by Pell and Gregory13) and mandibular angle fracture. Presence of lower

of publication

third molar*

Position*

of Fractures*

Position*

I - 50

I - 17

A - 58

II - 22

II - 13

B - 13

III - 1

III - 0

C-2

I - 153

I - 47

A - 173

II - 50

II - 18

B - 37

B - 18

III - 41

III - 12

C - 34

C-5

73

249 I - 525

Fuselier et al., 2002

B-5 C-1

A - 53

A - 153

II - 88

B - 147

B - 62

III - 24

C - 152

C - 48

I - 12

A - 40

A - 13

II - 25

B - 98

B - 31

III - 40

III - 12

C - 21

C-5

I - 967

I - 150

A - 654

A - 66

II - 351

II - 132

B - 511

B - 72

III - 148

III - 112

C - 301

C - 256

II - 232 823 III - 66

II - 96 161

1466

A - 24

A - 524

TE D

Subbasbraj et al., 2009

of Fractures*

I - 156

I - 23 Iida et al., 2005

Number

Vertical

SC

Lee and Dodson, 2000

Number

M AN U

Tevepaugh and Dodson, 1995

Horizontal

RI PT

Authorship and year

EP

* number of patients. Class I - adequate space to accommodate the M3 crown; Class II -

AC C

adequate space unavailable; and Class III - the majority of the M3 is located within the vertical ramus. Class A - same occlusal level; Class B - between the occlusal surface and the cemento-enamel junction; and Class C - below the cemento-enamel junction.13

ACCEPTED MANUSCRIPT Table 3 – Combination of vertical and horizontal positions of the lower third molar according to the classification by Pell and Gregory13. Presence of lower third molar*

IA

IIA

IIIA

IB

IIB

IIIB

Lee and Dodson, 2000**

249

148

24

1

5

23

9

0

3

31

Fuselier et al., 2002

823

475

48

1

42

95

10

8

89

55

of publication

Combination of vertical and horizontal positions of the lower third molar along the mandibular bone IC

IIC

IIIC

RI PT

Authorship and year

SC

* number of patients. ** data provided for only 244 patients. Class I - adequate space to accommodate the M3 crown; Class II - adequate space unavailable; and Class III - the majority of the M3 is located

M AN U

within the vertical ramus. Class A - same occlusal level; Class B - between the occlusal surface and

AC C

EP

TE D

the cemento-enamel junction; and Class C - below the cemento-enamel junction.13

ACCEPTED MANUSCRIPT Table 4 – Risk of bias assessed by the Meta-Analysis of Statistics Assessment and Review Instrument (MAStARI).

Q1 Q2

Q3

Q4

Q5

Q6

Q7

Tevepaugh and Dodson, 1995

√

√

√

√

√

NA

NA

Yamada et al., 1998

√

√

√

√

√

NA

NA

Lee and Dodson, 2000

√

√

√

√

√

NA

NA

Ma’aita and Alwrikat, 2000

√

√

√

√

√

NA

Ugboko et al., 2000

√

√

√

--

√

NA

Fuselier et al., 2002

√

√

√

√

√

NA

Iida et al., 2004

√

√

√

√

√

Iida et al., 2005

√

√

√

√

Metin et al., 2007

√

√

√

√

Rajkumar et al., 2009

%

Risk of

Yes/Risk

Bias

Q9

√

√

100%

+

--

√

85.7%

+

√

√

100%

+

--

√

85.7%

+

NA

--

√

71.4%

+

NA

√

√

100%

+

NA

NA

--

√

85.7%

+

√

NA

NA

√

√

100%

+

√

NA

NA

--

√

85.7%

+

M AN U

SC NA

√

√

√

√

√

NA

NA

√

√

100%

+

√

√

√

√

√

NA

NA

--

√

85.7%

+

√

√

√

√

√

NA

NA

√

√

100%

+

EP

Subbasbraj et al., 2009

TE D

Duan and Zhang, 2008

Q8

RI PT

Authors

√

√

√

√

√

NA

NA

--

√

85.7%

+

Choi et al., 2011

√

√

√

√

√

NA

NA

--

√

85.7%

+

Naghipur et al., 2014

√

√

√

√

√

NA

NA

--

√

85.7%

+

Kumar et al., 2015

√

√

√

√

√

NA

NA

--

√

85.7%

+

AC C

Thangavelu et al., 2010

Q1 - Was the study based on a random or pseudorandom sample?; Q2 – Were inclusion criteria for the sample clearly defined?; Q3 - Were confounding factors identified and strategies to manage them stated?; Q4 - Were outcomes assessed with objective criteria?; Q5 - Was there sufficient description of the groups for conducting comparisons?; Q6 - Was the follow-up carried out over a sufficient time period?; Q7 - Were the outcomes of people

ACCEPTED MANUSCRIPT who withdrew from the study described and included in the analysis?; Q8 - Were the outcomes measured in a reliable way?; Q9 - Was an appropriate statistical analysis used?; √: Yes; --: No; U: Unclear; NA: Not Applicable; +++: High; ++: Moderate; +: Low. Items 6 and 7 were considered Not Applicable (NA) because the eligible studies did not require

APPENDIX

Appendix 1 – Search strategies per database. Search Strategy (June, 2016)

M AN U

Database

SC

RI PT

follow-up for a certain time period.

(Third[All Fields] AND ("tooth, impacted"[MeSH Terms] OR ("tooth"[All Fields] AND "impacted"[All Fields]) OR "impacted tooth"[All Fields] OR "impacted"[All Fields]) AND ("molar"[MeSH Terms] OR "molar"[All Fields])) AND ("mandibular fractures"[MeSH Terms] OR ("mandibular"[All Fields] AND "fractures"[All Fields]) OR "mandibular fractures"[All Fields] OR ("mandibular"[All Fields] AND "fracture"[All Fields]) OR "mandibular fracture"[All Fields])

Scopus

TE D

EP

PubMed

(Third[All Fields] AND ("tooth, impacted"[MeSH Terms] OR ("tooth"[All Fields] AND "impacted"[All Fields]) OR "impacted tooth"[All Fields] OR "impacted"[All Fields]) AND ("molar"[MeSH Terms] OR "molar"[All Fields]) AND ("mandible"[MeSH Terms] OR "mandible"[All Fields] OR "mandibular"[All Fields]) AND angle[All Fields] AND ("fractures, bone"[MeSH Terms] OR ("fractures"[All Fields] AND "bone"[All Fields]) OR "bone fractures"[All Fields] OR "fracture"[All Fields])

"Impacted third molar" AND "mandibular fracture"

AC C

"Impacted third molar" AND "mandibular angle fracture"

Google Scholar

LILACS

"Impacted third molar" AND "mandibular angle fracture" tw:(“impacted third molar” AND “mandibular (instance:"regional") AND (db:("LILACS"))

fracture”)

AND

tw:(“impacted third molar” AND “mandibular angle fracture”) AND (instance:"regional") AND (db:("LILACS"))

SciELO

"Impacted third molar" AND "mandibular fracture" "Impacted third molar" AND "mandibular angle fracture"

OpenGrey

"Impacted third molar" AND "mandibular fracture" "Impacted third molar" AND "mandibular angle fracture"

ACCEPTED MANUSCRIPT Appendix 2 – Excluded articles and reasons for exclusion (n=9).

Reference

Reasons for

Author

Exclusion*

Wolujewic (1980)1

1

2.

Safdar and Meechan (1995)2

1

3.

Meisami et al.(2002)3

4.

Halmos et al., (2004)4

5.

Inaoka et al., (2009)5

6.

Patil (2012)6

7.

Yadav et al., (2013)7

8.

Gaddipati et al., (2014)8

1

9.

Kumar et al., (2015)9

2

RI PT

1.

1 1

M AN U

SC

2 1 2

1) Studies providing only the number of teeth involved in the fractures or the number

TE D

of mandibular angles fractured instead of providing the number of patients with or without lower third molars and relating them to fracture occurrence; 2) Studies without

EP

a control group.

EXCLUDED ARTICLES

AC C

1. Wolujewic MA. Fractures of the mandible involving the impacted third molar tooth: an analysis of 47 cases. British Journal of Oral Surgery. 1980;18:125-131. 2. Safdar N, Meechan JG. Relationship between fractures of the mandibular angle and the presence and state of eruption of the lower third molar. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1995;79:680-4. 3. Meisami T, Sojat A, Sàndor GK, Lawrence HP, Clokie CM. Impacted third molars and risk of angle fracture. Int J Oral Maxillofac Surg. 2002;31:140-4.

ACCEPTED MANUSCRIPT 4. Halmos DR, Ellis E, Dodson TB. Mandibular third molars and angle fractures. J Oral Maxillofac Surg. 2004;62:1076-81. 5. Inaoka SD, Carneiro SCAS, Vasconcelos BCE, Leal J, Porto GG. Relationship between

2009;14(7):E349-54.

RI PT

mandibular fracture and impacted lower third molar. Med Oral Patol Oral Cir Bucal.

6. Patil PM. Unerupted lower third molars and their influence on fractures of the mandibular angle and condyle. Br J Oral Maxillofac Surg. 2012;50:443-6.

SC

7. Yadav S, Tyagi S, Puri N, Kumar P, Kumar P. Qualitative and quantitative assessment of relationship between mandibular third molar and angle fracture on North Indian population:

M AN U

A clinico-radiographic study. Eur J Dent. 2013;7(2):212-7.

8. Gaddipati R, Ramisetty S, Vura N, Kanduri RR, Gunda VK. Impacted mandibular third molars and their influence on mandibular angle and condyle fractures: A retrospective study. J Craniomaxillofac Surg. 2014;42:1102-5.

TE D

9. Kumar PS, Dhupar V, Akkara F, Kumar GBA. Eruption Status of Third Molar and Its Possible Influence on the Location of Mandibular Angle Fracture: A Retrospective Analysis.

AC C

EP

J. Maxillofac. Oral Surg. 2015;14:243–6.

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT