Three-dimensional evaluation of mandibular midline distraction: A systematic review

Accepted Manuscript Three-dimensional evaluation of mandibular midline distraction: a systematic review Atilla Gül, MD, Jan P. de Gijt, MD, DMD, Stephen T.H. Tjoa, DDS, MSc, MS, Eppo B. Wolvius, DMD, MD, PhD, Maarten J. Koudstaal, MD, DMD, PhD PII:

S1010-5182(18)30711-X

DOI:

10.1016/j.jcms.2018.08.014

Reference:

YJCMS 3086

To appear in:

Journal of Cranio-Maxillo-Facial Surgery

Received Date: 25 March 2018 Revised Date:

24 July 2018

Accepted Date: 22 August 2018

Please cite this article as: Gül A, de Gijt JP, Tjoa STH, Wolvius EB, Koudstaal MJ, Three-dimensional evaluation of mandibular midline distraction: a systematic review, Journal of Cranio-Maxillofacial Surgery (2018), doi: 10.1016/j.jcms.2018.08.014. 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.

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Atilla Gül, MD1, Jan P. de Gijt, MD, DMD1, Stephen T.H. Tjoa, DDS, MSc, MS1, Eppo B. Wolvius, DMD, MD, PhD1, Maarten J. Koudstaal, MD, DMD, PhD1 1

Corresponding author: Atilla Gül, MD Department of Oral and Maxillofacial Surgery Erasmus MC — University Medical Center Rotterdam Dr. Molewaterplein 40, 3015 GD Rotterdam The Netherlands +31 10 7040640 [email protected] Sources of support in the form of grants: None

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Department of Oral and Maxillofacial Surgery, Erasmus MC — University Medical Center Rotterdam, Rotterdam, the Netherlands (Head: Eppo B. Wolvius, DMD, MD, PhD)

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Three-dimensional evaluation of mandibular midline distraction: a systematic review

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ABSTRACT

43 Objective: To provide a literature overview on mandibular midline distraction (MMD) using

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three-dimensional (3D) imaging analysis techniques. Regarding different distractor types, the

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focus was on changes in position and/or morphology of the mandibular condyle and

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temporomandibular joint (TMJ), skeletal effects, dental effects, soft tissue effects, and

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biomechanical and masticatory effects, specifically on the mandible and TMJ.

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Methods: Studies up to March 27 2017 were included, in accordance with the Preferred

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Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines,

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using Embase, Medline OvidSP, Web-of-science, Scopus, Cochrane, and Google Scholar.

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Results: Thirty-one full-text papers were assessed for eligibility and 15 met the inclusion

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criteria: prospective (2), retrospective (2), case-report (1) and computational analysis (10). All

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included studies were graded low (level 4–5) for quality of evidence, using the Oxford Centre

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for Evidence-Based Medicine criteria.

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Conclusion: There is a limited number of studies available, with low levels of evidence and

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small sample sizes. Bone-borne distraction seems preferable when taking skeletal effects into

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account. Tooth-borne distraction leads to significant dental tipping. Hybrid distractors

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combined with parasymphyseal step osteotomy seem to be the most stable under functional

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masticatory loads. The effects of chewing appeared to be marginal during the latency period.

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No permanent TMJ symptoms were reported, and little is known about soft tissue effects.

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Systematic review registration: International Prospective Register of Systematic Reviews,

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PROSPERO CRD42014010010.

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Keywords: mandibular midline distraction osteogenesis, mandibular symphyseal distraction

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osteogenesis, distraction osteogenesis, three-dimensional, three-dimensional imaging,

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systematic review

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INTRODUCTION

77 Transverse mandibular and maxillary discrepancies manifest in anterior and posterior

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crowding, and can be prominent in patients with developmental disorders and congenital

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deformities (e.g. Treacher-Collins, Apert, Crouzon, Nager). Traditionally, transverse

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discrepancies were treated with orthodontic appliances and/or tooth extractions. However, in

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the early 1990s, distraction was introduced for the facial skeleton and new treatment options

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became available (McCarthy et al., 1992; Guerrero et al., 1997; Koudstaal et al., 2005). With

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this technique, both osteogenesis and histogenesis are induced.

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Mandibular midline distraction (MMD) is used as a surgical technique to widen the

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mandible. An osteotomy is performed in the midline of the mandible and a distractor is

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attached on both sides of the osteotomy. Distractors can be attached to the bone (bone-borne),

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the teeth (tooth-borne), or a combination of both (hybrid). Following surgery, a latency period

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of 5–7 days is respected to allow initial soft callus formation. The distractor is activated at a

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specific rhythm and rate, depending on the distraction site and preferences of the surgeon or

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orthodontist.

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Indications for MMD are mandibular anterior or posterior crowding (Guerrero et al.,

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1997), uni- and bilateral crossbite (King et al., 2004), V-shape of the mandible, severe

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(maxillary-) mandibular transverse deficiency, and impacted anterior teeth with inadequate

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space and tipped teeth (Proffit et al., 2003). In certain cases both the maxilla and the mandible

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need widening, and bimaxillary expansion (BiMEx) is indicated. BiMEx is a combination of

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surgically assisted rapid maxillary expansion (SARME) and MMD (Weil et al., 1997; Del

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Santo et al., 2000; De Gijt et al., 2012).

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The mandible is a curved bone, which on both sides terminates at the

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temporomandibular joint (TMJ). The TMJ is surrounded by a soft tissue envelope and allows

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the mandible to perform rotational, translational, and horizontal movements. The attachment

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and activation of the distractor creates different vectors in three-dimensional (3D) planes. The

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biomechanical properties of the distractors themselves are important as they may influence

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the outcome of distraction in the long-term, and have their respective influence on the TMJ

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(Mommaerts, 2001; Conley and Legan, 2003; Mommaerts et al., 2005; Gunbay et al., 2009).

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Until now, research on MMD has focused largely on conventional methods, including dental

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cast models and posterior–anterior cephalograms (De Gijt et al., 2012). However, imaging

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techniques and software have become more sophisticated. This makes it possible to analyse

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radiographs, it is possible to perform 3D measurements of bony and soft tissue structures on

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3D reconstruction models, using cone beam computed tomography (CBCT). This technique

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results in less radiation exposure than the multi-slice computed tomography (MSCT),

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generating highly realistic facial and skeletal information compared with 2D radiographs.

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Finite element method (FEM) studies can analyse stress distribution during MMD in the

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mandible and the TMJ.

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The main objective of this study was to provide a literature overview on MMD using

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3D imaging analysis techniques. Regarding different distractor types, the focus was on the

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changes in position and/or morphology of the mandibular condyle and TMJ, skeletal effects,

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dental effects, soft tissue effects, and biomechanical and masticatory effects, specifically on

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the mandible and the TMJ.

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METHODS

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Protocol and registration

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The methods for the analysis were described and registered as a protocol in the International

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Prospective Register of Systematic Reviews (PROSPERO) under the registration number

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CRD42014010010. The Medical Ethics Committee of Erasmus MC — University Medical

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Center Rotterdam, Rotterdam, The Netherlands approved the research protocol (approval

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number: MEC-2014-343).

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Search strategy

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The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)

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statement was used as a guideline for this systematic review (Moher et al., 2009). An

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electronic search up to March 27 2017 was performed, using the following electronic

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databases:

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Embase

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Medline OvidSP

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Web-of-science

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Scopus

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Cochrane

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Google Scholar

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The search strategy used a defined combination of keywords for each of the above databases

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(Appendix I). References for the included studies were manually scanned for other relevant

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studies in order to complete the search.

146 Inclusion criteria

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Randomized controlled trials (RCT), controlled clinical trials (CCT), case series, and finite

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element method (FEM) studies were included in this review. Adolescent- or adult-aged

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subjects who underwent an MMD, all types of distractors (bone-, tooth-borne or bone-and-

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tooth-borne hybrid distractors), and all types of 3D imaging analysis techniques were

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included. The search strategy was restricted to English-language publications, and animal

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studies were excluded. There was no restriction on sample size or follow-up period in the case

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series.

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Data extraction and analysis

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After performing the search strategy, all duplicates were removed. Two authors (AG and

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JPG) independently made a selection, based on title and abstract when available. Papers were

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excluded if the study groups included congenital (craniofacial) deformities, mental

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retardation, or history of radiation therapy in the area of interest. If the paper appeared to

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match the inclusion criteria, or when the abstract was lacking information or missing, the full-

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text paper was obtained. Each selected full-text paper was then completely reviewed

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independently by both authors in accordance with all the inclusion criteria, and then included

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or rejected. Included studies were graded on quality of evidence using the Oxford Centre for

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Evidence-Based Medicine (OCEBM) criteria (OCEBM, 2011). The included studies were

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scored on the origin of the study, study design, sample size, age range, gender, length of

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follow-up, 3D imaging analysis technique, 3D imaging software, type of osteotomy, type of

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distractor, latency period, distraction rate/gap, consolidation period, and treatment outcome

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(Table 1).

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The included studies were divided into two main groups — a ‘clinical’

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(morphological) group and an ‘FEM’ (biomechanical) group. The objective for the ‘clinical’

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group was to evaluate whether MMD provokes changes in position and/or morphology of the

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mandibular condyle and TMJ, skeletal effects, dental effects, or soft tissue effects, using 3D

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imaging analysis techniques. The objective of the ‘FEM’ group was to evaluate the

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distraction, masticatory effects and latency period, stress distribution, and displacement of

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mandibular segments following MMD, using FEM.

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RESULTS

179 The electronic database search results yielded 757 citations (Embase 148, Medline OvidSP

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144, Web-of-science 130, Scopus 197, Cochrane 3, and Google Scholar 135). After

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correctiing for duplicates, 330 citations remained. Four papers were identified through a

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manual search of reference lists.

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All of the 334 papers were screened by title and abstract. 303 papers were excluded for

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different reasons, including papers with topics other than MMD, MMD but not analysed by

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3D imaging analysis techniques, and animal studies. The remaining 31 papers were screened

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using the full-text papers. Of this selection another 16 papers were excluded for different

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reasons, including papers with topics other than MMD, not analysed by 3D imaging analysis

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techniques, animal studies, non-English-language papers, and presentations of meetings.

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Fifteen studies were therefore included (Figure 1; Table 1). Of this selection, only five studies

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(Landes et al., 2008; Gökalp, 2008; Gunbay et al., 2009; Seeberger et al., 2011; Bianchi et al.,

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2017) met the OCEBM criteria for level-4 evidence as case series. The remaining 10 studies

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(Basciftci et al., 2004; Boccaccio et al., 2006; Boccaccio et al., 2007; Boccaccio 2008a,

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2008b, 2008c; Boccaccio et al., 2011; Kim et al., 2012; Savoldelli et al., 2012; Singh et al.,

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2016) met the OCEBM criteria for level-5 evidence as mechanism-based reasoning (Table 1).

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Clinical group

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This group consisted of five studies (Landes et al., 2008; Gökalp, 2008; Gunbay et al., 2009;

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Seeberger et al., 2011; Bianchi et al., 2017). In this group the ages of all the patients (n = 55)

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ranged from 14.3 to 43 years (32 female, 23 male), with a mean age of 21.9 years. The

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follow-up period depended on the objective of the study and ranged from 3 months (Landes et

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al., 2008; Seeberger et al., 2011) postoperatively to 48 months (Gunbay et al., 2009; Bianchi

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et al., 2017) postconsolidaton (Table 2).

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Surgical intervention and distraction

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In four studies (Landes et al., 2008; Gökalp, 2008; Gunbay et al., 2009; Seeberger et al.,

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2011) a midsymphyseal osteotomy was performed between the mandibular central incisors. A

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step osteotomy between the canine and lateral incisor was performed in one study (Bianchi et

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al., 2017). Bone-borne, tooth-borne, and hybrid distractors were used. SARME was

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performed simultaneously in four studies (Landes et al., 2008; Gökalp, 2008; Seeberger et al.,

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2011; Bianchi et al., 2017). See Table 3 for additional baseline information on the studies.

212 3D imaging analysis

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The following 3D imaging techniques were reported: 3D computed tomography (3DCT)

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(Landes et al., 2008), computed tomography (CT) (Gunbay et al., 2009; Seeberger et al.,

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2011; Bianchi et al., 2017), MSCT (Gökalp, 2008), magnetic resonance imaging (MRI)

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(Gökalp, 2008), and facial scan (Bianchi et al., 2017). These scans were performed

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preoperatively in all studies (Landes et al., 2008; Gökalp, 2008; Gunbay et al., 2009;

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Seeberger et al., 2011; Bianchi et al., 2017), at end of distraction (Gunbay et al., 2009), after

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completion of postoperative orthodontic treatment (Bianchi et al., 2017), and postoperatively

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at 3 months (Landes et al., 2008; Seeberger et al., 2011), 6 months (Gökalp, 2008), and 36

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months (Gunbay et al., 2009).

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There were various analysis methods applied for evaluating the mandibular condyle

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position. Most studies evaluated the mandibular condyle position by measuring the

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intercondylar distance (Landes et al., 2008; Gökalp, 2008; Bianchi et al., 2017), condylar axis

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(Landes et al., 2008; Gökalp, 2008; Gunbay et al., 2009), and mandibular axis (Seeberger et

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al., 2011). Two studies analysed the TMJ region (Landes et al., 2008; Gökalp, 2008). Landes

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et al. measured lateral and inner distances from the condylar surface to the mandibular fossa

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on the coronal plane of the (3D)CT scan (Landes et al., 2008). Landes et al., Seeberger et al.

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and Bianchi et al. measured the distance between the condyles (Landes et al., 2008; Seeberger

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et al., 2011; Bianchi et al., 2017). Gökalp evaluated the disc positions of the condyle and the

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glenoid fossa on bilateral sagittal MRI scans for both closed and open positions of the mouth

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(Gökalp, 2008).

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For evaluating skeletal effects, Seeberger et al. measured the inter mental foramen

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distance and mandibular tilting (Seeberger et al., 2011). Bianchi et al. measured the distance

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from the genial tubercle to the hyoid bone, length of the hyoid bone to basal skull plane,

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mandibular body length, bigonial width, ramal angle, and ramus length (Bianchi et al., 2017).

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For evaluating the dental effects, inter first molar crown (Seeberger et al., 2011;

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Bianchi et al., 2017), inter first molar root (Seeberger et al., 2011; Bianchi et al., 2017), inter

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first premolar crown (Seeberger et al., 2011; Bianchi et al., 2017), and inter first premolar root

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distances were measured (Seeberger et al., 2011; Bianchi et al., 2017). These were measured

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using the buccal cusps and the lingual root apices. Bianchi et al. added measurements of inter-

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occlusal distances for the second molar, first molar, second premolar, first premolar, and

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canine (Bianchi et al., 2017). Landes et al. measured the inter-canine distance by using the

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dental cavum midpoint of the left and right inferior canine on the axial plane of the (3D)CT

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scan (Landes et al., 2008). Only Seeberger et al. performed measurements of first molar and

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first premolar angulation (Seeberger et al., 2011). With regards to the soft tissue effects, Bianchi et al. examined morphological changes

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as shell-to-shell deviation (clearance vector map) and represented regional changes as a false-

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colour map on the facial scan. Linear/angular measurements were performed using 17

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landmarks taken from classical anthropometry, and axial/sagittal cross-sections were also

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obtained (Bianchi et al., 2017) (Table 4).

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Treatment outcome

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In all cases the distraction was successful, and the desired expansion was achieved.

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Regarding mandibular condylar position, a distolateral movement was found in two

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studies (Landes et al., 2008; Gunbay et al., 2009). This was between 2.5° and 3° in the study

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by Gunbay et al., whereas Landes et al. observed a distolateral movement of 0.028° (Landes

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et al., 2008; Gunbay et al., 2009). In the same Landes et al. study the vertical lateral, cranial,

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and median distances to the fossa remained unchanged, with no angulation of the condyles in

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the coronal plane (Landes et al., 2008). Gökalp reported a bilateral posterolateral rotation of

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−1° (right) and −9° (left) of the medial pole of the condyles, with an unchanged disc position

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of the TMJ (Gökalp, 2008). Lateral condylar displacement was analysed in three studies

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(Landes et al., 2008; Seeberger et al., 2011; Bianchi et al., 2017). In the study by Seeberger et

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al. the intercondylar distance changed insignificantly by 0.67 ± 1.67 mm, while Landes et al.

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observed a significant mean decrease of −1.0 ± 0.1 mm (Landes et al., 2008; Seeberger et al.,

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2011). Bianchi et al. also reported a decrease for the intercondylar distance of −1.83 ± 0.11

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mm; however, this was not significant (Bianchi et al., 2017). There were only three cases of

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transient TMJ symptoms reported for all the patients in the ‘clinical’ group (Gunbay et al.,

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2009). No permanent TMJ symptoms were described.

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With regards to the skeletal effects, Seeberger et al. observed a significant increase in

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the inter mental foramen distance and a significant tilting of the mandibular corpus, with V-

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shaped rotation (Seeberger et al., 2011). Bianchi et al. reported a significant decrease of

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21.43% for the genial tubercle of the mandible-to-hyoid bone distance. The ramal angle

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decreased insignificantly and there was evidence of a slight increase in mandibular body

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length (Bianchi et al., 2017).

ACCEPTED MANUSCRIPT Concerning dental effects, Seeberger et al. observed a significant increase in the inter

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first molar and inter first premolar crown and root distances, and a significant lateral

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angulation of the tooth-borne distractor fixation level for all first molars and premolars

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(Seeberger et al., 2011). Landes et al. observed a significant increase in intercanine distance of

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3.8 ± 0.18 mm (Landes et al., 2008). Bianchi et al. reported a significant increase in

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intercanine distance of 4.89 ± 1.96 mm, inter first premolar distance of 5.48 ± 1.89 mm, and

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inter second premolar distance of 4.69 ± 3.78 mm. There was no significant increase for the

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intermolar distances. The mean expansion at the level of the root apices of the first premolars

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was 3.01 ± 0.83 mm and of the first molars was 3.35 ± 1.11 mm, which were both significant

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(Bianchi et al., 2017).

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When evaluating the soft tissue effects for MMD, Bianchi et al. observed major

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postoperative changes in the lower lip and chin. MMD did not cause any vertical or horizontal

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asymmetry. There were significant differences demonstrated for the sagittal projection of the

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cheilion, labialis inferior, pogonion points, and enlargement of the mouth and chin. The axial

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sections through the pogonion showed a forward displacement of the chin, with enlargement

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after MMD (Table 5).

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293 FEM group

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This group consisted of ten studies (Basciftci et al., 2004; Boccaccio et al., 2006; Boccaccio

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et al., 2007; Boccaccio 2008a, 2008b, 2008c; Boccaccio et al., 2011; Kim et al., 2012;

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Savoldelli et al., 2012; Singh et al., 2016).

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Only three studies (Basciftci et al., 2004; Kim et al., 2012; Savoldelli et al., 2012) reported the

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origin of the geometric data for the FEM model, which were obtained from healthy

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volunteers. The age of these volunteers (n = 3, all male) ranged from 22 to 30 years, with a

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mean age of 26.3 years (Table 6).

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Distraction

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Various analysing methods were applied for evaluating the distraction. In nine FEM

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simulations a vertical midsymphyseal osteotomy was performed (Basciftci et al., 2004;

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Boccaccio et al., 2006; Boccaccio et al., 2007; Boccaccio 2008a, 2008b, 2008c; Boccaccio et

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al., 2011; Kim et al., 2012; Savoldelli et al., 2012). Only one FEM simulation performed three

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types of osteotomy — midsymphyseal, angulated midsymphyseal, and parasymphyseal step

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(Singh et al., 2016). Various types of distractor were analysed in these simulations — bone-

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borne (Basciftci et al., 2004; Boccaccio 2008c; Boccaccio et al., 2011; Kim et al., 2012;

ACCEPTED MANUSCRIPT Savoldelli et al., 2012; Singh et al., 2016), tooth-borne (Boccaccio et al., 2006; Boccaccio et

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al., 2007; Boccaccio 2008a, 2008b, 2008c; Boccaccio et al., 2011; Kim et al., 2012; Singh et

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al., 2016) and hybrid (Basciftci et al., 2004; Boccaccio 2008c; Boccaccio et al., 2011; Kim et

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al., 2012; Singh et al., 2016). The simulated distraction gaps were 2 mm (Boccaccio 2008a,

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2008b, 2008c), 6 mm (Boccaccio et al., 2006; Boccaccio et al., 2007), 7 mm (Boccaccio et al.,

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2011), 8 mm (Kim et al., 2012), and 10 mm (Basciftci et al., 2004; Savoldelli et al., 2012).

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Singh et al. used a 6-day distraction period with a frequency of one distraction per day,

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however, the size of the distraction gap was not described (Singh et al., 2016) (Table 7).

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319 Masticatory effects and latency period

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Boccaccio et al. showed that parasitic rotations of the mandible arms may counteract arch

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expansion due to mastication forces. There was a significant effect of mastication forces on

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mechanical response using the tooth-borne distractor (Boccaccio et al., 2006). The same

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author observed that the hybrid distractor provided the most stable situation at the distraction

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gap. The tooth-borne distractor showed similar displacement, but had less stability under

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mastication forces (Boccaccio et al., 2011). These findings are in line with Singh et al., who

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showed that a hybrid distractor combined with a parasymphyseal step osteotomy permits

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reduction in the parasitic rotations produced by mastication forces (Singh et al., 2016). In

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another study Boccaccio et al. showed that the mandibular arch displacements were less than

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10% different from the distraction gap for tooth-borne and hybrid distractors. The hybrid

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distractor was the most stable under mastication forces (Boccaccio 2008c). The same author

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simulated the effects of aging on the latency period before starting the distraction with a

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tooth-borne distractor. The results showed an optimal latency period of 5–6 days for young

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patients (up to 20 years old), 7–8 days for adult patients (around 55 years old), and 9–10 days

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for the older patients (more than 70 years old). Mastication forces appeared to have a rather

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marginal influence on this (Boccaccio 2008a). Related to this outcome, the same author

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simulated two different mastication loads in another study. There was a full mastication load

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and a mastication load reduced by 70%. The results showed that both intramembranous and

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endochondral ossification are predicted to occur for the full mastication loading in the

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osteotomized region, while for the reduced mastication loading mainly intramembranous

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ossification is predicted. The results showed bony bridges between both sides of the bone

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callus after a latency period of 7–8 days (Boccaccio 2008b). Concerning this outcome, the

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same author had reported previously that a lower distraction rate of 0.6 mm/day leads to

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greater amounts of bony bridging. Subsequently, it was reported that distraction rates higher

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than 1.2 mm/day could lead to low-quality bone callus (Boccaccio et al., 2007).

346 Stress distribution and displacement of mandibular segments

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In all FEM simulations the distraction was successful and the desired expansion was

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achieved. Each mandibular segment showed a different pattern of stress distribution and

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displacement dependent on the type of distractor.

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Area contiguous to the distractor

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Only two studies (Basciftci et al., 2004; Kim et al., 2012) reported on stress distribution in the

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area contiguous to the distractor. Basciftci et al. observed a low-stress distribution using the

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bone-borne or hybrid distractor in the area contiguous to the distractor (Basciftci et al., 2004).

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Kim et al., however, observed a high-stress distribution using a bone-borne distractor in the

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same area (Kim et al., 2012).

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Dental arch and alveolar process

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In the study by Kim et al. the tooth-borne distractor showed most expansion at the dental arch,

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followed by the hybrid distractor and the bone-borne distractor. In comparison with the hybrid

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distractor and bone-borne distractor, the tooth-borne distractor showed high levels of stress

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distribution, and displaced the alveolar process and basal bone area from incisor region to

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premolar region in a parallel fashion. However, the bone-borne distractor showed a decrease

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in lateral displacement from the anterior to posterior part (Kim et al., 2012). This outcome is

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in concordance with Basciftci et al., who observed a nonparallel separation of the

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dentoalveolar complex from anterior to posterior using the bone-borne distractor (Basciftci et

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al., 2004).

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Boccaccio et al. reported that expansion of the dental arch appeared to be more significant for

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the tooth-borne and hybrid distractors than for the bone-borne distractor (Boccaccio et al.,

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2011). This outcome is in line with Singh et al., who demonstrated a maximum stress

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distribution on the root using the tooth-borne distractor with a parasymphyseal step

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osteotomy. The same author showed that the amount of bone displacement in a

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parasymphyseal step osteotomy using the hybrid distractor was maximum and consistent,

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including a significant increase in intercanine, interpremolar, and intermolar distance (Singh

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et al., 2016).

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ACCEPTED MANUSCRIPT Corpus, gonion, and ramus

379

Basciftci et al. observed minimal displacement of the ramal and gonion regions using the

380

bone-borne or hybrid distractor. There was a high stress distribution observed in the ramal

381

region (Basciftci et al., 2004). In contrast to this outcome, Kim et al. observed a low stress

382

distribution with the bone-borne distractor and a more even stress distribution with the hybrid

383

distractor in the mandibular body and ramal region, while the tooth-borne distractor showed a

384

higher stress distribution (Kim et al., 2012).

385

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Condyle and articular disc

387

Basciftci et al. observed the highest stress distribution below the condylar area using the

388

bone-borne or hybrid distractor, while there was minimal condylar displacement (Basciftci et

389

al., 2004). This is in concordance with Kim et al., who observed a high level of stress

390

distribution with the bone-borne, tooth-borne, and hybrid distractor in the condylar neck area,

391

with minimal condylar displacement. In the articular disc, the tooth-borne distractor showed

392

the highest stress distribution, followed by the hybrid and bone-borne distractor (Kim et al.,

393

2012). In contrast to these outcomes, Savoldelli et al. observed a similar stress distribution on

394

the condylar surfaces and in articular discs before and after MMD with the bone-borne

395

distractor (Savoldelli et al., 2012).

397 398

DISCUSSION

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This systematic review represents an overview of the literature on studies of MMD using 3D

400

imaging analysis techniques. Unfortunately, no RCTs or CCTs were found. Using the

401

inclusion criteria, 15 potentially relevant papers were found of which five were clinical

402

studies (Landes et al., 2008; Gökalp, 2008; Gunbay et al., 2009; Seeberger et al., 2011;

403

Bianchi et al., 2017) and 10 were FEM studies (Basciftci et al., 2004; Boccaccio et al., 2006;

404

Boccaccio et al., 2007; Boccaccio 2008a, 2008b, 2008c; Boccaccio et al., 2011; Kim et al.,

405

2012; Savoldelli et al., 2012; Singh et al., 2016). The wide variety of outcome variables

406

limited the opportunity to review the literature using the systematic method, and a meta-

407

analysis of the data was not possible. The majority of the reported studies were FEM models,

408

leading to a low level of evidence (OCEBM, 2011). FEM models of the human masticatory

409

system are useful in identifying and predicting stress distributions in anatomical structures.

410

However, the human mandible is not symmetric, and there are many individual differences.

411

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ACCEPTED MANUSCRIPT 412

Changes in position and/or morphology of mandibular condyle and TMJ

413

The effect of MMD on the condyles and TMJ is closely related to the rigidity of the distractor.

414

Each type of distractor has different fixation points and therefore causes a different amount of

415

force with a different vector on the mandible, and thus on the condyle and the TMJ. With regards to condylar rotation, a distolateral rotation was found in two studies

417

(Landes et al., 2008; Gunbay et al., 2009). An explanation for this finding might be that the

418

intercondylar distance decreased in the Landes et al. study, and a distolateral rotation

419

occurred. However, both authors used different distractors. Landes et al. used an axially high

420

rigid distractor (The Modus, Medartis, Basel, Switzerland), while Gunbay et al. used an

421

axially low rigid distractor (TMD, Surgi-Tec NV, Bruges, Belgium), which may have

422

influenced the outcome. Furthermore, Landes et al. analysed the rotational movement after 3

423

months of consolidation, while Gunbay et al. analysed directly after distraction, not taking the

424

adaptation of the condyles into account. Both analyses were performed using CT scans. An

425

inconspicuous bilateral posterolateral rotation was reported for the medial pole of the

426

condyles on the axial CT plane, with an unchanged disc position of the TMJ on the sagittal

427

MRI plane (Gökalp, 2008). This rotation was asymmetric and without clinical symptoms for

428

the patient, indicating adaptability of the condyle. This outcome should be adopted cautiously,

429

considering that this was a case-report with a short follow-up of 6 months.

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416

Regarding intercondylar distance, both an increase and a decrease were found.

431

Seeberger et al. observed an insignificant increase using a tooth-borne distractor, while

432

Landes et al. observed a significant decrease and Bianchi et al. an insignificant decrease using

433

a bone-borne distractor (Landes et al., 2008; Seeberger et al., 2011; Bianchi et al., 2017).

434

Theoretically, tooth-borne distractors exert their force mainly on a dentoalveolar level, and

435

lead to a combination of increased vertical angle and more posterolateral widening when

436

compared with bone-borne distractors, which exert their force anteriorly on a basal bone level

437

and would create anterolateral expansion. Based on this, tooth-borne distractors could lead to

438

a greater lateral displacement of the posterior part of the mandible and increased intercondylar

439

distance, with an increase in stress distribution in the TMJ. However, in an FEM study, Kim

440

et al. observed minimal condylar displacement using a tooth-borne distractor, with an

441

increased stress distribution in the articular disc (Kim et al., 2012). The observed decrease in

442

intercondylar distance may be due to the combination of the bone-borne distractor fixation

443

points and the soft tissue envelope surrounding the posterior part of the mandible, especially

444

the TMJ. This soft tissue envelope could form sufficient resistance in the posterior part of the

445

mandible, because bone-borne distractors apply their force anteriorly of the mandible. This is

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ACCEPTED MANUSCRIPT also supported by the high levels of stress distribution in the condylar area, with minimal

447

condylar displacement, observed by Basciftci et al. and Kim et al. with the bone-borne

448

distractor in an FEM study (Basciftci et al., 2004; Kim et al., 2012). However, Basciftci et al.

449

did not consider the mastication forces and soft tissues in the TMJ. Kim et al. did consider the

450

mastication forces, and the analysis was only based on the left side of the mandible, without

451

taking into account the soft tissues in the TMJ. Since humans are not symmetrical, the

452

conclusions must be interpreted with some care. In contrast, Savoldelli et al. generated an

453

FEM model with a complete masticatory system before and after MMD, during jaw closing,

454

using a bone-borne distractor, and including the soft tissues in the TMJ. There was a similar

455

stress distribution observed on the condylar surfaces and in the articular discs before and after

456

MMD. Their study suggests that anatomical changes in the TMJ should not predispose to

457

long-term tissue fatigue. There was an absence of permanent clinical TMJ symptoms after

458

MMD (Savoldelli et al., 2012). This is supported by Gunbay et al., who reported three

459

transient cases of TMJ symptoms, which were all only mild TMJ pain, and resolved after the

460

distraction period (Gunbay et al., 2009). Overall, no permanent clinical TMJ symptoms were

461

found in this systematic review. It can be assumed that MMD does not lead to permanent

462

clinical TMJ symptoms. However, this assumption is mostly based on FEM studies, with only

463

a small number of clinical studies with relatively short follow-up periods and small sample

464

sizes.

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446

465 Skeletal effects

467

With regards to skeletal effects, there was a significant increase in inter mental foramen

468

distance and a significant tilting of the mandibular corpus with V-shaped rotation observed

469

following MMD using a tooth-borne distractor (Seeberger et al., 2011). This outcome is in

470

disagreement with the results of Kim et al., who observed a displacement of the alveolar

471

process and basal bone area in a parallel way, from incisor region to premolar region, with a

472

notable displacement on the ramus (Kim et al., 2012). However, this outcome was based on

473

an FEM model, with the described limitations. Bianchi et al. reported an insignificant

474

decrease in the ramal angle and a significant decrease of 21.43% for the genial tubercle of the

475

mandible-to-hyoid bone distance (Bianchi et al., 2017). These findings were obtained using a

476

bone-borne distractor.

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477

Overall, bone-borne distractors cause a more proportionate expansion in the vertical

478

direction compared with the hybrid and tooth-borne distractors (Gunbay et al., 2009;

479

Seeberger et al., 2011). Bone-borne distractors apply their force mostly at the mandibular

ACCEPTED MANUSCRIPT 480

basal level compared with tooth-borne distractors. This is in line with Kim et al. and

481

Boccaccio et al., who observed more expansion in the alveolar process area and dental arch

482

with the tooth-borne distractor than with the hybrid and bone-borne distractors (Boccaccio et

483

al., 2011; Kim et al., 2012). These findings suggest that, in terms of skeletal effects, the bone-borne distractor is

485

preferable. However, it should be noted that a second surgical procedure is needed to remove

486

this distractor, which is not the case for a tooth-borne distractor.

487

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Dental effects

489

Three studies (Landes et al., 2008; Seeberger et al., 2011; Bianchi et al., 2017) reported the

490

interdental distances following MMD. Landes et al. and Bianchi et al. showed a significant

491

change in intercanine distance. However, both authors used a different type of distractor

492

(Landes et al., 2008; Bianchi et al., 2017). Seeberger et al. and Bianchi et al. measured the

493

inter first molar crown, inter first molar root, inter first premolar crown, and inter first

494

premolar root distances (Seeberger et al., 2011; Bianchi et al., 2017). Except for the inter first

495

molar crown distance in the Bianchi et al. study, all of these distances changed significantly in

496

both studies (Seeberger et al., 2011; Bianchi et al., 2017). Both studies used a different type of

497

distractor and Seeberger et al. reported a relatively short follow-up period of 3 months, which

498

makes it difficult to compare (Seeberger et al., 2011; Bianchi et al., 2017). Longer follow-up

499

periods are needed to analyse the dental stability, taking relapse and remodelling into account.

500

Concerning dental angulation, data are sparse due to different influencing factors, such as

501

type of distractor, widening of the hemimandible, orthodontic treatment, and availability of

502

3D imaging analysis techniques. Only one study reported on dental angulation following

503

MMD, which was a significant lateral angulation on the tooth-borne distractor fixation level

504

for all first molars and premolars (2.63° and 3.32° respectively) (Seeberger et al., 2011). It

505

can be concluded that the tooth-borne distractor leads to significant dental tipping, which

506

could affect dental stability negatively in the long-term.

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SC

488

508

Soft tissue effects

509

Only one study (Bianchi et al., 2017) reported soft tissue effects following MMD. Major

510

postoperative changes in the lower lip and chin were observed. MMD did not cause any

511

vertical or horizontal asymmetry. There was statistical significance demonstrated in the

512

sagittal projection of the cheilion, labialis inferior, pogonion points, and enlargement of the

513

mouth and chin. The axial sections through the pogonion showed a forward displacement of

ACCEPTED MANUSCRIPT the chin with enlargement after MMD. It should be considered that dental movements due to

515

orthodontic treatment may have an influence on these findings, especially for the lower lip

516

projection. There was an insignificant increase in mandibular body length, which could be an

517

explanation for the chin projection. However, in this study simultaneous SARME was

518

performed, which complicates the interpretation of the soft tissue effects isolated for MMD.

519

It can be assumed that MMD leads to soft tissue changes specifically for the lower lip and

520

chin projection, but it should be noted that this assumption is based on only one study.

RI PT

514

521

Biomechanical and masticatory effects, specifically on the mandible and the TMJ

523

Biomechanical and masticatory effects together constitute an important role in MMD. The

524

hybrid distractor seems to be the most stable under functional masticatory loads (Boccaccio et

525

al., 2011), specifically combined with a parasymphyseal step osteotomy (Singh et al., 2016).

526

The magnitude of these masticatory loads seems to have a marginal influence on the optimal

527

latency period with the use of a tooth-borne distractor (Boccaccio 2008a). However, these

528

masticatory loads can influence bone callus formation in the distraction gap (Boccaccio

529

2008b), where high distraction rates could lead to low-quality bone callus (Boccaccio et al.,

530

2007). These outcomes could support healthcare professionals in their choice of distractor

531

type and lead to safer control of distraction. The effect of chewing on the latency period

532

appears to be marginal. However, this assumption is based on FEM models using various

533

distraction gaps. Moreover, not all FEM models take into account the complete in vivo

534

situation, including the masticatory loads and TMJ. This complicates the comparison of these

535

outcomes. Mastication loads could be influenced by the possible strengthening of the

536

masticatory muscles, while dental contact between the maxilla and the mandible could

537

influence the mastication loads. Also, MMD is often combined with SARME, and there are

538

no FEM models available simulating this situation.

540 541

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539

SC

522

CONCLUSION

542

There has been a limited number of studies performed on MMD using 3D imaging analysis

543

techniques. Most of these papers are FEM studies and characterized by a low level of

544

evidence. Clinical studies on the (long-term) 3D biomechanical effects of MMD are sparse,

545

and with relatively small sample sizes. There is inconsistency between the effects and the

546

clinical relevance of the different distractor types. The bone-borne distractor seems preferable

547

when taking skeletal effects into account. Tooth-borne distraction leads to significant dental

ACCEPTED MANUSCRIPT tipping, theoretically increasing the risk of relapse. The hybrid distractor, combined with a

549

parasymphyseal step osteotomy, seems to be the most stable under functional masticatory

550

loads. The effect of chewing appears to be marginal during the latency period. From these

551

studies, it can be concluded that MMD does not result in permanent clinical TMJ symptoms.

552

However, possible long-term effects on the TMJ are not clarified yet because long-term

553

follow-up studies are lacking. In addition, little is known about the soft tissue effects of

554

MMD. More clinical studies with large case series, using 3D imaging analysis techniques, are

555

needed to clarify long-term morphological 3D aspects of MMD.

556 FUNDING

SC

557 558

None

560 561

COMPETING INTERESTS

562 563

None declared

564 565

ETHICAL APPROVAL

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The Medical Ethics Committee of Erasmus MC — University Medical Center Rotterdam,

568

Rotterdam, The Netherlands approved the research protocol (approval number MEC-2014-

569

343).

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572 573 574 575

PATIENT CONSENT

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571

Not required

ACKNOWLEDGMENTS

576 577

The authors acknowledge W. Bramer, biomedical information specialist of Erasmus MC —

578

University Medical Center Rotterdam, Rotterdam, The Netherlands, for his support in the

579

development of the literature search.

580 581

ACCEPTED MANUSCRIPT 582 583

REFERENCES

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Alkan A, Ozer M, Bas B, Bayram M, Celebi N, Inal S, Ozden B: Mandibular symphyseal distraction osteogenesis: review of three techniques. Int J Oral Maxillofac Surg 36:111–117, 2007. Basciftci FA, Korkmaz HH, Iseri H, Malkoc S: Biomechanical evaluation of mandibular midline distraction osteogenesis by using the finite element method. Am J Orthod Dentofacial Orthop 125:706–715, 2004. Bianchi FA, Gerbino G, Corsico M, Schellino E, Barla N, Verze L, Ramieri G: Soft, hard-tissues and pharyngeal airway volume changes following maxillomandibular transverse osteodistraction: computed tomography and three-dimensional laser scanner evaluation. J Craniomaxillofac Surg 45:47–55, 2017. Boccaccio A, Cozzani M, Pappalettere C: Analysis of the performance of different orthodontic devices for mandibular symphyseal distraction osteogenesis. Eur J Orthod 33:113– 120, 2011. Boccaccio A, Lamberti L, Pappalettere C: Effects of aging on the latency period in mandibular distraction osteogenesis: a computational mechanobiological analysis. J Mech Med Biol 8:203–225, 2008a. Boccaccio A, Lamberti L, Pappalettere C, Carano A, Cozzani M: Mechanical behavior of an osteotomized mandible with distraction orthodontic devices. J Biomech 39:2907– 2918, 2006. Boccaccio A, Lamberti L, Pappalettere C, Cozzani M, Siciliani G: Comparison of different orthodontic devices for mandibular symphyseal distraction osteogenesis: a finite element study. Am J Orthod Dentofacial Orthop 134:260–269, 2008b. Boccaccio A, Pappalettere C, Kelly DJ: The influence of expansion rates on mandibular distraction osteogenesis: a computational analysis. Ann Biomed Eng 35:1940–1960, 2007. Boccaccio A, Prendergast PJ, Pappalettere C, Kelly DJ: Tissue differentiation and bone regeneration in an osteotomized mandible: a computational analysis of the latency period. Med Biol Eng Comput 46:283–298, 2008c. Centre for Evidence-Based Medicine (University of Oxford). CEBM levels of evidence system. Available at: http://www.cebm.net. Conley R, Legan H: Mandibular symphyseal distraction osteogenesis: diagnosis and treatment planning considerations. Angle Orthod 73:3–11, 2003. de Gijt JP, Vervoorn K, Wolvius EB, Van der Wal KG, Koudstaal MJ: Mandibular midline distraction: a systematic review. J Craniomaxillofac Surg 40:248–260, 2012. Del Santo M, Jr., Guerrero CA, Buschang PH, English JD, Samchukov ML, Bell WH: Long-term skeletal and dental effects of mandibular symphyseal distraction osteogenesis. Am J Orthod Dentofacial Orthop 118:485–493, 2000. Gökalp H: Effects of symphyseal distraction osteogenesis on the temporomandibular joint seen with magnetic resonance imaging and computerized tomography. Am J Orthod Dentofacial Orthop 134:689–699, 2008. Guerrero CA, Bell WH, Contasti GI, Rodriguez AM: Mandibular widening by intraoral distraction osteogenesis. Br J Oral Maxillofac Surg 35:383–392, 1997.

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Gunbay T, Akay MC, Aras A, Gomel M: Effects of transmandibular symphyseal distraction on teeth, bone, and temporomandibular joint. J Oral Maxillofac Surg 67:2254–2265, 2009. Kewitt GF, Van Sickels JE: Long-term effect of mandibular midline distraction osteogenesis on the status of the temporomandibular joint, teeth, periodontal structures, and neurosensory function. J Oral Maxillofac Surg 57:1419–1425; discussion 1426, 1999. Kim KN, Cha BK, Choi DS, Jang I, Yi YJ, Jost-Brinkmann PG: A finite element study on the effects of midsymphyseal distraction osteogenesis on the mandible and articular disc. Angle Orthod 82:464–471, 2012. King JW, Wallace JC: Unilateral Brodie bite treated with distraction osteogenesis. Am J Orthod Dentofacial Orthop 125:500–509, 2004. Koudstaal MJ, Poort LJ, van der Wal KG, Wolvius EB, Prahl-Andersen B, Schulten AJ: Surgically assisted rapid maxillary expansion (SARME): a review of the literature. Int J Oral Maxillofac Surg 34:709–714, 2005. Landes CA, Laudemann K, Sader R, Mack M: Prospective changes to condylar position in symphyseal distraction osteogenesis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 106:163–172, 2008. Little RM, Riedel RA, Stein A: Mandibular arch length increase during the mixed dentition: postretention evaluation of stability and relapse. Am J Orthod Dentofacial Orthop 97:393–404, 1990. Mah J, Bumann A: Technology to create the three-dimensional patient record. Seminars in orthodontics. 251–257. Mah JK, Huang JC, Choo H: Practical applications of cone-beam computed tomography in orthodontics. J Am Dent Assoc 141 Suppl 3:7S–13S, 2010. Malkoc S, Iseri H, Karaman AI, Mutlu N, Kucukkolbasi H: Effects of mandibular symphyseal distraction osteogenesis on mandibular structures. Am J Orthod Dentofacial Orthop 130:603–611, 2006. McCarthy JG, Schreiber J, Karp N, Thorne CH, Grayson BH: Lengthening the human mandible by gradual distraction. Plast Reconstr Surg 89:1–8; discussion 9–10, 1992. Merrett SJ, Drage NA, Durning P: Cone beam computed tomography: a useful tool in orthodontic diagnosis and treatment planning. J Orthod 36:202–210, 2009. Moher D, Liberati A, Tetzlaff J, Altman DG, Group P: Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. J Clin Epidemiol 62:1006–1012, 2009. Mommaerts MY: Bone anchored intraoral device for transmandibular distraction. Br J Oral Maxillofac Surg 39:8–12, 2001. Mommaerts MY, Polsbroek R, Santler G, Correia PE, Abeloos JV, Ali N: Anterior transmandibular osteodistraction: clinical and model observations. J Craniomaxillofac Surg 33:318–325, 2005. Moussa R, O'Reilly MT, Close JM: Long-term stability of rapid palatal expander treatment and edgewise mechanotherapy. Am J Orthod Dentofacial Orthop 108:478–488, 1995. Proffit WR, White RP, Sarver DM: Contemporary treatment of dentofacial deformity. St Louis, MO; London; Mosby, 2003. Raoul G, Wojcik T, Ferri J: Outcome of mandibular symphyseal distraction osteogenesis with bone-borne devices. J Craniofac Surg 20:488–493, 2009. Savoldelli C, Bouchard PO, Maniere-Ezvan A, Bettega G, Tillier Y: Comparison of stress distribution in the temporomandibular joint during jaw closing before and after

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symphyseal distraction: a finite element study. Int J Oral Maxillofac Surg 41:1474– 1482, 2012. Seeberger R, Kater W, Davids R, Thiele OC, Edelmann B, Hofele C, Freier K: Changes in the mandibular and dento-alveolar structures by the use of tooth borne mandibular symphyseal distraction devices. J Craniomaxillofac Surg 39:177–181, 2011. Singh P, Wang C, Ajmera DH, Xiao SS, Song J, Lin Z: Biomechanical effects of novel osteotomy approaches on mandibular expansion: a three-dimensional finite element analysis. J Oral Maxillofac Surg 74:1658 e1651–1658 e1615, 2016. Sperber GH: Craniofacial development. Hamilton: BC Decker Inc, 2001. Weil TS, Van Sickels JE, Payne CJ: Distraction osteogenesis for correction of transverse mandibular deficiency: a preliminary report. J Oral Maxillofac Surg 55:953–960, 1997.

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Appendix I. Search strategies

RI PT

Embase ('distraction osteogenesis'/de OR (distract* NEAR/3 (osteogenes* OR midline)):ab,ti) AND (mandible/de OR 'mandible osteotomy'/de OR 'mandible condyle'/de OR chin/de OR (mandib* OR 'lower jaw' OR condyle* OR chin):ab,ti) AND ('three dimensional imaging'/de OR ('three dimensional' OR 3d OR 3-d):ab,ti) NOT ([animals]/lim NOT [humans]/lim)

M AN U

SC

Medline OvidSP ("Osteogenesis, Distraction"/ OR (distract* ADJ3 (osteogenes* OR midline)).ab,ti.) AND (exp mandible/ OR (mandib* OR "lower jaw" OR condyle* OR chin).ab,ti.) AND (exp "Imaging, Three-Dimensional"/ OR ("three dimensional" OR 3d OR 3-d).ab,ti.) NOT (exp animals/ NOT humans/) Cochrane ((distract* NEAR/3 (osteogenes* OR midline)):ab,ti) AND ((mandib* OR 'lower jaw' OR condyle* OR chin):ab,ti) AND (('three dimensional' OR 3d OR 3-d):ab,ti)

TE D

Web-of-science TS=(((distract* NEAR/3 (osteogenes* OR midline))) AND ((mandib* OR "lower jaw" OR condyle* OR chin)) AND (("three dimensional" OR 3d OR 3-d)) NOT ((animal? OR monkey? OR goat? OR dog? OR minipig? OR pig? OR swine? OR rat? OR sheep?) NOT (human? OR patient?)))

AC C

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Scopus TITLE-ABS-KEY(((distract* W/3 (osteogenes* OR midline))) AND ((mandib* OR "lower jaw" OR condyle* OR chin)) AND (("three dimensional" OR 3d OR 3-d)) AND NOT ((animal? OR monkey? OR goat? OR dog? OR minipig? OR pig? OR swine? OR rat? OR sheep?) AND NOT (human? OR patient?))) Google Scholar "distraction osteogenesis"|"midline distraction" mandible|mandibular 3d|"3|three dimensional|d"

ACCEPTED MANUSCRIPT

Bianchi et al.

Title

OCEBM level Study design of evidence

3D imaging analysis technique

2017 Soft, hard-tissues and pharyngeal airway volume changes following maxillomandibular transverse osteodistraction: computed tomography and threedimensional laser scanner evaluation

Italy

4

CT, facial scan

Singh et al.

2016 Biomechanical effects of novel osteotomy approaches on mandibular expansion: a three-dimensional finite element analysis

China

Savoldelli et al.

2012 Comparison of stress distribution in the temporomandibular joint during jaw closing before and after symphyseal distraction: a finite element study

France

5

Computational study FEM

Kim et al.

2012 A finite element study on the effects of midsymphyseal distraction osteogenesis on the mandible and articular disc

South Korea 5

Computational study FEM

Boccaccio et al.

2011 Analysis of the performance of different orthodontic devices for mandibular symphyseal distraction osteogenesis

Italy

5

Computational study FEM

Seeberger et al.

2011 Changes in the mandibular and dentoalveolar structures by the use of tooth borne mandibular symphyseal distraction devices

Germany

4

Retrospective CS

EP

AC C

5

M AN U

Year

TE D

Author

RI PT

Origin

SC

Table 1. Included studies

Prospective CS

Computational study FEM

CT

ACCEPTED MANUSCRIPT

Table 1. (continued) Origin

OCEBM level Study design of evidence

3D imaging analysis technique

2009 Effects of transmandibular symphyseal distraction on teeth, bone, and temporomandibular joint

Turkey

4

Retrospective CS

CT

Landes et al.

2008 Prospective changes to condylar position in symphyseal distraction osteogenesis

Germany

4

Prospective CS

(3D)CT

Boccaccio et al. a

2008 Effects of aging on the latency period in Italy mandibular distraction osteogenesis: a computational mechanobiological analysis

5

Computational study FEM

Boccaccio et al. b

2008 Tissue differentiation and bone Italy regeneration in an osteotomized mandible: a computational analysis of the latency period

5

Computational study FEM

Gökalp

2008 Effects of symphyseal distraction osteogenesis on the temporomandibular joint seen with magnetic resonance imaging and computerized tomography

Turkey

4

Case report

Boccaccio et al. c

2008 Comparison of different orthodontic devices for mandibular symphyseal distraction osteogenesis: a finite element study

Italy

5

Computational study FEM

Boccaccio et al.

2007 The influence of expansion rates on mandibular distraction osteogenesis: a computational analysis

Italy

5

Computational study FEM

RI PT

Gunbay et al.

Title

SC

Year

AC C

EP

TE D

M AN U

Author

MSCT, MRI

ACCEPTED MANUSCRIPT

Table 1. (continued. Origin

OCEBM level Study design of evidence

Basciftci et al.

3D imaging analysis technique

2006 Mechanical behavior of an osteotomized mandible with distraction orthodontic devices

Italy

5

Computational study FEM

2004 Biomechanical evaluation of mandibular midline distraction osteogenesis by using the finite element method

Turkey

5

Computational study FEM

RI PT

Boccaccio et al.

Title

SC

Year

M AN U

Author

Abbreviations: 3D, three-dimensional; CS, case series; CT, computed tomography; FEM, finite element method; MRI, magnetic resonance imaging; MSCT, multislice computed tomography; OCEBM, Oxford Centre for Evidence-Based Medicine

Table 2. Patient characteristics of included studies in the ‘clinical group’

Bianchi et al.

2017 Prospective CS

Seeberger et al.

3D imaging analysis technique

Sample size (n)

Age range, mean (years)

Gender (F/M)

Follow-up period (months)

CT, facial scan

19

18–36, 26.3

11/8

24–48

2011 Retrospective CS

CT

19

15–43, 27.1

12/7

3

Gunbay et al.

2009 Retrospective CS

CT

7

14.3–22.5, 16.2

3/4

36–48

Landes et al.

2008 Prospective CS

9

15–43, 24.7

5/4

3–24

Gökalp

2008 Case report

1

15, 15

1/–

6

TE D

Study design

EP

Year

(3D)CT

AC C

Author

MSCT, MRI

Abbreviations: 3D, three-dimensional; CS, case series; CT, computed tomography; MRI, magnetic resonance imaging; MSCT, multislice computed tomography

ACCEPTED MANUSCRIPT

Table 3. Surgical intervention and distraction in the ‘clinical group’ Distractor type

Latency period (days)

2017 Step MSO, GA

Bone-borne

7

Seeberger et al.

2011 Vertical MSO, ND

Tooth-borne

7

Gunbay et al.

2009 Vertical MSO, LA

Bone-borne

7

Landes et al.

2008 Step MSO, GA

Bone-borne

5

Gökalp

2008 Vertical MSO, GA

Tooth-borne

5

Distraction rate (mm/day)

Consolidation period (months)

Additional surgery

1

2

SARME

0.4

3

SARME

1

1

–

0.6

3

SARME

1

6

SARME

RI PT

Bianchi et al.

Osteotomy, anaesthesia

SC

Year

M AN U

Author

AC C

EP

TE D

Abbreviations: GA, general anaesthesia; LA, local anaesthesia; MSO, midsymphyseal osteotomy; ND, not described; SARME, surgically assisted rapid maxillary expansion

ACCEPTED MANUSCRIPT

Year

Bianchi et al.

3D imaging analysis technique

Reported analysis objects and methods

2017 CT, facial scan

ND, pre-OP ND, post-OP OT

Measurement of LMH, LHYO, GOGNR, GOGNL, ID, GOGO, RA°, ARGOR, ARGOL, IOSMD, IOFMD, IOSPMD, IOFPMD, IOCD, IFMCD, IFPMCD, IFMRD, IFPMRD on CT scan. Linear and angular measurements using 17 facial landmarks taken from classical anthropometry on facial scan.

Seeberger et al.

2011 CT

1 week, pre-OP 3 months, post-OP

Measurement of ID, IFMCD, IFPMCD, IFMRD, IFPMRD, FMA°, FPMA°, IMFD, MT° on 3D reconstruction of CT scan.

Gunbay et al.

2009 CT

ND, pre-OP ND, end of distraction 36 months, post-OP

Measurement of DLRC° on CT scans.

Landes et al.

2008 (3D)CT

Same day, pre-OP 3 months, post-OP

Measurement of ID, DLRC°, ICD on axial plane of (3D)CT scan. Measurement of CSTFCD, CSTFLD, CSTFMD on coronal plane of (3D)CT scan.

Gökalp

2008 MSCT, MRI

Measurement of PRMPC° on axial plane of MSCT scan. Disc positions of condyle and glenoid fossa in closed and open position of the mouth evaluated on bilateral sagittal MRI scans of TMJ.

TE D

M AN U

SC

Author

RI PT

Period, phase

EP

Table 4. 3D imaging analysis method in the ‘clinical group’

AC C

ND, pre-OP 6 months, post-OP

Abbreviations: 3D, three-dimensional; ARGOL, ramus length left; ARGOR, ramus length right; CSTFCD, condyle surface to fossa cranial distance; CSTFLD, condyle surface to fossa lateral distance; CSTFMD, condyle surface to fossa median distance; CT, computed tomography; DLRC°, distolateral rotation of condyle; FMA°, first molar angle; FPMA°, first premolar angle; GOGNL, mandibular body length left; GOGNR, mandibular body length right; GOGO, bigonial width; ICD, intercanine distance; ID, intercondylar distance; IFMCD, inter first molar crown distance; IFMRD, inter first molar root distance; IFPMCD, inter first premolar crown distance; IFPMRD, inter first premolar root distance; IMFD, inter mental foramen distance; IOCD, inter occlusal canine distance; IOFMD, inter occlusal first molar distance; IOFPMD, inter occlusal first premolar distance; IOSMD, inter occlusal second molar distance; IOSPMD, inter occlusal second premolar distance; LHYO, hyoid bone to basal skull plane length; LMH, genial tubercle to hyoid bone distance; MRI, magnetic resonance imaging; MSCT, multislice computed tomography; MT°, mandibular tilt; OP, operative; OT, orthodontic treatment; PRMPC°, posterolateral rotation of the medial pole of condyle; RA°, ramal angle; TMJ, temporomandibular joint

ACCEPTED MANUSCRIPT

Table 5. Treatment outcome in the ‘clinical group’

24–48

Sample size (n)

Reported outcome changes (distance, mm; angle/rotation, °)

19

LMH: −2.08 ± 0.07* LHYO: 0.13 ± 0.28 GOGNR: 1.61 ± 0.63 GOGNL: 1.81 ± 0.36 ID: −1.83 ± 0.11 GOGO: 0.12 ± 0.23 RA°: −2.31 ± 0.61 ARGOR: 0.21 ± 0.15 ARGOL: 0.06 ± 0.25 IOSMD: 2.15 ± 0.88 IOFMD: 4.01 ± 1.33 IOSPMD: 4.69 ± 3.78* IOFPMD: 5.48 ± 1.89* IOCD: 4.89 ± 1.96* IFMCD: 4.59 ± 1.94 IFPMCD: 5.44 ± 1.61* IFMRD: 3.35 ± 1.11* IFPMRD: 3.01 ± 0.83* Major postoperative changes in the lower lip and chin. No vertical or horizontal asymmetry. Statistical significance in the sagittal projection of cheilion, labialis inferior, pogonion points and enlargement of mouth and chin. Forward displacement of the chin with enlargement on axial sections through pogonion.

SC

Bone-borne

M AN U

2017 CT, facial scan

TE D

Bianchi et al.

Follow-up period (months)

RI PT

3D imaging Distractor type analysis technique

EP

Year

AC C

Author

ACCEPTED MANUSCRIPT

Table 5. (continued) Year

3D imaging Distractor type analysis technique

Follow-up period (months)

Sample size (n)

Reported outcome changes (distance, mm; angle/rotation, °)

19

ID: IFMCD: IFPMCD: IFMRD: IFPMRD: FMA°: FPMA°: IMFD: MT°:

0.67 ± 1.67 4.9 ± 1.30* 4.83 ± 1.63* 2.60 ± 2.05* 2.93 ± 1.84* 2.63 ± 1.75* 3.32 ± 1.57* 2.67 ± 1.18* 2.30 ± 1.97*

RI PT

Author

Tooth-borne

3

Gunbay et al.

2009 CT

Bone-borne

36–48

7

DLRC°: TMJS:

2.5–3 3 (transient)

Landes et al.

2008 (3D)CT

Bone-borne

3

9

ID: DLRC°: ICD: CSTFLD: CSTFCD: CSTFMD:

−1.0 ± 1.1* 0.028 ± 4.34 3.8 ± 0.18* 0.4 ± 0.5 0.4 ± 0.5 0.4 ± 0.3

Gökalp

2008 MSCT, MRI

Tooth-borne

6

1

PRMPC°:

−1° (right) −9° (left)

AC C

EP

TE D

M AN U

SC

Seeberger et al. 2011 CT

Abbreviations: *, significant p < 0.05; 3D, three-dimensional; ARGOL, ramus length left; ARGOR, ramus length right; CSTFCD, condyle surface to fossa cranial distance; CSTFLD, condyle surface to fossa lateral distance; CSTFMD, condyle surface to fossa median distance; CT, computed tomography; DLRC°, distolateral rotation of condyle; FMA°, first molar angle; FPMA°, first premolar angle; GOGNL, mandibular body length left; GOGNR, mandibular body length right; GOGO, bigonial width; ICD, intercanine distance; ID, intercondylar distance; IFMCD, inter first molar crown distance; IFMRD, inter first molar root distance; IFPMCD, inter first premolar crown distance; IFPMRD, inter first premolar root distance; IMFD, inter mental foramen distance; IOCD, inter occlusal canine distance; IOFMD, inter occlusal first molar distance; IOFPMD, inter occlusal first premolar distance; IOSMD, inter occlusal second molar distance; IOSPMD, inter occlusal second premolar distance; LHYO, hyoid bone to basal skull plane length; LMH, genial tubercle to hyoid bone distance; MRI, magnetic resonance imaging; MSCT, multislice computed tomography; MT°, mandibular tilt; OP, operative; OT, orthodontic treatment; PRMPC°, posterolateral rotation of the medial pole of condyle; RA°, ramal angle; TMJS, temporomandibular joint symptoms

ACCEPTED MANUSCRIPT

Table 6. Patient characteristics of included studies in the ‘FEM group’ Sample size (n)

Age (years)

Gender (F/M)

Singh et al.

2016 Computational study

FEM

1

ND

ND

Savoldelli et al.

2012 Computational study

FEM

1

30

M

Kim et al.

2012 Computational study

FEM

1

27

M

Boccaccio et al.

2011 Computational study

FEM

1

ND

ND

Boccaccio et al. a

2008 Computational study

FEM

1

ND

ND

Boccaccio et al. b

2008 Computational study

FEM

1

ND

ND

Boccaccio et al. c

2008 Computational study

FEM

1

ND

ND

Boccaccio et al.

2007 Computational study

FEM

1

ND

ND

Boccaccio et al.

2006 Computational study

FEM

1

ND

ND

Basciftci et al.

2004 Computational study

FEM

1

22

M

AC C

EP

Abbreviations: 3D, three-dimensional; FEM, finite element method; ND, not described

RI PT

3D imaging analysis technique

SC

Study design

M AN U

Year

TE D

Author

ACCEPTED MANUSCRIPT

Table 7. Distraction in the ‘FEM group’ Masticatory loads in model

2016 Vertical MSO ND Angulated MSO Parasymphyseal SO

Bone-borne Tooth-borne Hybrid

Yes Yes Yes

Savoldelli et al.

2012 Vertical MSO

10

Bone-borne

Yes

Kim et al.

2012 Vertical MSO

8

Bone-borne Tooth-borne Hybrid

Yes Yes Yes

Boccaccio et al.

2011 Vertical MSO

7

Bone-borne Tooth-borne Hybrid

Yes Yes Yes

Boccaccio et al. a

2008 Vertical MSO

2

Tooth-borne

Yes

Boccaccio et al. b

2008 Vertical MSO

2

Tooth-borne

Yes

Boccaccio et al. c

2008 Vertical MSO

2

Bone-borne Tooth-borne Hybrid

Yes Yes Yes

Boccaccio et al.

2007 Vertical MSO

6

Tooth-borne

Yes

Boccaccio et al.

2006 Vertical MSO

6

Tooth-borne

Yes

Basciftci et al.

2004 Vertical MSO

10

Bone-borne Hybrid

No No

RI PT

Distractor type

M AN U

SC

Distraction gap (mm)

TE D

Singh et al.

Osteotomy

EP

Year

AC C

Author

Abbreviations: MSO, midsymphyseal osteotomy; ND, not described; SO, step osteotomy

ACCEPTED MANUSCRIPT

Records identified through database searching (n = 757)

SC

(n = 148) (n = 144) (n = 130) (n = 197) (n = 3) (n = 135)

M AN U

Systematic search: • Embase • Medline OvidSP • Web-of-science • Scopus • Cochrane • Google Scholar

RI PT

Figure 1. Data extraction flowchart, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Additional records identified through reference list search (n = 4)

TE D

Records after duplicates removed (n = 334)

Records screened (n = 334)

AC C

EP

Records excluded (n = 303)

Full-text papers excluded, with reasons (n = 16)

Full-text papers assessed for eligibility (n = 31)

Total number of studies included (n = 15)

Duplicates per database: • Embase • Medline OvidSP • Web-of-science • Scopus • Cochrane • Google Scholar

(n = 1) (n = 111) (n = 70) (n = 177) (n = 3) (n = 65)