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Author's personal copy Journal of Cranio-Maxillo-Facial Surgery (2010) 38, 166e174 Ó 2009 European Association for Cranio-Maxillo-Facial Surgery doi:10.1016/j.jcms.2009.06.006, available online at http://www.sciencedirect.com A systematic review of the effects of bone-borne surgical assisted rapid maxillary expansion* Jeroen VERSTRAATEN, DDS1, Anne M. KUIJPERS-JAGTMAN, DDS, PhD, FDSRCS (Eng)1, Maurice Y. MOMMAERTS, MD, DDS, PhD2, Stefaan J. BERGÉ, MD, DDS, PhD3, Rania M. NADA, DDS1, Jan G. J. H. SCHOLS, DDS, PhD1, In collaboration with the Eurocran Distraction Osteogenesis Group 1 Department of Orthodontics and Oral Biology (Head of the department: Prof. A.M. Kuijpers-Jagtman, DDS, PhD, FDSRCS (Eng)), Radboud University Nijmegen Medical Centre, The Netherlands; 2 Division of Maxillo-Facial Surgery, Department of Surgery, General Hospital St. Jan, Bruges, Belgium; 3 Department of Oral and Maxillofacial Surgery, Radboud University Nijmegen Medical Centre, The Netherlands SUMMARY. Introduction: A systematic literature review was conducted to find out if bone-borne maxillary expansion with corticotomies is an effective and secure orthodontic/orthopaedic treatment modality, eliminating orthodontic and periodontal side effects of tooth-borne maxillary expansion with corticotomies. Material and methods: Randomized controlled trials (RCT), controlled clinical trials (CCT) and case series with a sample size ‡ 5 were electronically searched in PubMED, MEDLINE, EMBASE Excerpta Medica, CINAHL, Biological Abstracts and CENTRAL till June 2008. Data were extracted by 2 observers. Results: Ten studies fulfilled the inclusion criteria, of which 9 were prospective and 1 was a retrospective case series. Conclusion: No RCT’s or CCT’s were published on bone-borne surgically assisted rapid maxillary expansion (SARME). For expected advantages compared to tooth-borne SARME, only weak evidence was found for less buccal tipping of the teeth used as anchor teeth in tooth-borne expansion. The heterogeneity of the retrieved publications and the wide variety of outcome variables posed serious restrictions on the review of the literature in a quantitative systematic manner. There is a need for well designed clinical trials research on the effects of tooth-borne and bone-borne SARME. Ó 2009 European Association for Cranio-Maxillo-Facial Surgery Keywords: review, systematic, palatal expansion technique, osteogenesis, distraction, maxilla, bone-borne, assessment, outcomes (SARME) with tooth-borne banded or bonded orthodontic appliances and corticotomies of the areas of skeletal resistance (piriform aperture, zygomatic buttress, pterygoid junction and midpalatal suture), is nowadays an accepted treatment option for transverse maxillary hypoplasia. Although the results of SARME are largely positive, side effects as well as relapse are not eliminated (Phillips et al., 1992; Pogrel et al., 1992; Northway and Meade, 1997; Chung and Goldman, 2003; Byloff and Mossaz, 2004). The negative effects are presumably due to the tooth-borne anchorage of conventional appliances. Tooth-borne appliances deliver stresses to the roots and periodontal ligament as well as the alveolar bone during expansion. Also the bony movement is not retained during the consolidation period. This led to the introduction of the first bone-borne appliance (distractor) in 1999, which delivers the expansion force directly to the maxillary bone and would avoid the negative orthodontic and periodontal effects (Mommaerts, 1999). The objective of this systematic review is to investigate whether bone-borne SARME INTRODUCTION Transverse maxillary hypoplasia is frequently seen in non-syndromic adolescents and adults (Proffit et al., 1998). Non-surgical treatment options to correct transverse maxillary hypoplasia in children and young adolescents are slow maxillary expansion (SME) for mild discrepancies or rapid maxillary expansion (RME) for more severe cases. Although RME with a bonded or banded orthodontic appliance is an accepted treatment modality, the long-term dental and skeletal stability of the expansion remain uncertain (Lagravère et al., 2005a,b). Due to the increased skeletal resistance, RME in adults is associated with alveolar bending, periodontal ligament compression, buccal root resorption of the anchor teeth, fenestration of the buccal cortical plate, and tipping and extrusion of the anchor teeth (Barber and Sims, 1981; Carmen et al., 2000). Therefore in adults the alternative of surgically assisted rapid maxillary expansion * This study is part of Eurocran (European Collaboration on Craniofacial Anomalies) and was funded by the EU-Framework-V Program, grant number QLG1-CT-2000-01019. (1) Is an effective orthodontic and orthopaedic treatment modality. 166 Author's personal copy Effects of bone-borne surgical assisted rapid maxillary expansion 167 (2) Is effective in eliminating orthodontic (buccal tilting, extrusion) and periodontal (root resorption, tooth mobility) side effects. (3) Is a safe and secure treatment modality. METHODS not present enough relevant information were obtained in full. Secondly, full-text articles were reviewed according to all the inclusion criteria. In the event of a discrepancy between the observers, a consensus decision was taken. The results were compared and the data were analyzed using the index of inter-rater reliability (Cohen’s Kappa). Types of studies, participants and intervention RESULTS Randomized controlled trials (RCT), controlled clinical trials (CCT) and case series with a sample size of N $ 5 were included in this review. We included adolescents and adults who had undergone a SARME with a bone-borne palatal distractor. There was no restriction on the persisting malocclusion and/or the origin of malocclusion. Search results Search strategy We performed an electronic search in the following databases: PubMED (from 1966 to week 4 of June 2008). MEDLINE (from 1966 to week 4 of June 2008). EMBASE Excerpta Medica (from 1980 to week 4 of June 2008). CINAHL (from 1982 to week 4 of June 2008). Biological Abstracts (from 1991 to 2001). CENTRAL (to the first quarter of 2008). The search strategy was developed and databases were selected with the help of a senior librarian who specialized in health sciences. The search strategy focused on two aspects: (1) terms to search for the surgical procedure of interest (i.e., osteotomies with expansion of the maxilla and palate); (2) terms to search for the appliance (i.e., bone-borne). Free text words and MeSH terms were used. The heading sequence (‘‘rapid palatal expansion’’ OR ‘‘rapid maxill* expan*’’ OR ‘‘palatal expansion technique [MeSH]’’) AND (‘‘bone-borne’’ OR ‘‘bone-anchored’’ OR ‘‘transpalatal distractor’’ OR ‘‘palatal distractor’’ OR ‘‘transpalatal’’ OR ‘‘skeletally-anchored’’ OR ‘‘distraction’’) was selected. No exclusion of articles based on language was performed. To complete the search, references of each selected publication about bone-borne SARME were hand-searched. Where there were multiple publications from the same research group, one of the authors was contacted to obtain additional information. When a study was published both in English and another language, the former was selected. The search results and the number of abstracts selected are depicted in Table 1. The search revealed 96 publications in PubMed, 91 publications in MEDLINE, 10 publications in EMBASE, 4 publications in CINAHL, 2 publications in Biological Abstracts and 1 in CENTRAL. PubMed had the greatest number (45) of abstracts selected among the databases that were used. One of the selected abstracts was not retrieved from PubMed and was also found in Biological Abstracts. The QUORUM-flow diagram gives an overview of the selection process (Fig. 1). Of the 46 selected abstracts (inter-rater K ¼ 0.979), 23 reported a SARME technique with a bone-borne distractor. From the hand search of the references of these 23 studies, we selected 27 further titles for abstract retrieval and further selection. After application of the inclusion criteria by both observers all publications from the hand search were excluded. Thirteen publications fulfilled all inclusion criteria (Matteini and Mommaerts, 2001; Pinto et al., 2001; Neyt et al., 2002; Gerlach and Zahl, 2003; Ramieri et al., 2005; Koudstaal et al., 2006a,b; Hansen et al., 2007; Scolozzi et al., 2007; Seitz et al., 2007, 2008; Tausche et al., 2007, 2008). After contact with the authors 3 publications were excluded (Hansen et al., 2007; Seitz et al., 2007; Tausche et al., 2008) because the studies were published in another, more extensive or English written, publication (Tausche et al., 2007; Seitz et al., 2008). Table 2 shows the characteristics of the ten studies finally included. We included three studies from the research group from Bruges, Belgium (Matteini and Mommaerts, 2001; Pinto et al., 2001; Neyt et al., 2002). After contact with the authors it appeared that potentially the same subjects were used in their study on morbidity associated with bone-borne SARME (Neyt et al., 2002) and in their studies measuring post-expansion changes on dental casts (Matteini and Mommaerts, Table 1 e Search results from databases Database Data extraction Data were extracted and methodological quality assessed independently by two observers (JV, AK). Data were recorded on special extraction forms. First, the abstracts were reviewed without considering the number of patients reported. Articles that apparently fulfilled the inclusion criteria and articles of which the title or abstract did Abstracts Abstracts Abstracts not found found selected in pubmed PubMed 96 MEDLINE 91 EMBASE excerpta medica 10 CINAHL 4 Biological Abstracts 2 CENTRAL 1 Abbreviations: NA, not applicable. 45 42 7 0 1 0 NA 0 0 0 1 0 Author's personal copy 168 Journal of Cranio-Maxillo-Facial Surgery Electronic search identified abstracts and screened for retrieval N = 97 Manual search identified relevant abstracts in references N = 27 Excluded abstracts N = 51 Reason: not topic related Excluded abstracts N = 13 Reason: not topic related Articles retrieved for more information N = 46 Bone-borne SARME (N = 23) Abstracts not enough information (N = 23) Articles retrieved for more information N = 14 Excluded articles N = 33 Reason: did not meet the inclusion criteria Excluded articles N = 14 Reason: did not meet the inclusion criteria Potentially appropriate to be included N = 13 Potentially appropriate to be included N=0 13 articles Excluded 3 articles (multiple publications of same study) Final selection 10 articles Fig. 1 e QUORUM-flow diagram. 2001; Pinto et al., 2001). This overlap was not considered a problem because the topic of research was different. For counting the total number of patients included in the review, it was decided to use the study with the biggest sample (Neyt et al., 2002). There was complete agreement between the two observers for inclusion of the studies. Types of included studies All studies were case series from Europe, 9 prospective and 1 retrospective. No RCT’s or CCT’s were found. Outcomes of included studies The following outcomes were reported: Assessment of expansion in terms of changes in dental and skeletal structures (Matteini and Mommaerts, 2001; Pinto et al., 2001; Gerlach and Zahl, 2003; Ramieri et al., 2005; Tausche et al., 2007). Assessment of orthodontic side effects in terms of tipping of teeth (Pinto et al., 2001; Tausche et al., 2007). Report of treatment related difficulties i.e., appliance failure, surgical complications (Neyt et al., 2002; Gerlach and Zahl, 2003; Ramieri et al., 2005; Koudstaal et al., 2006a,b; Scolozzi et al., 2007; Seitz et al., 2008). Dental and periodontal side effects (Ramieri et al., 2005). Assessment of pain (Gerlach and Zahl, 2003). Methodological quality of the included studies All studies had a minimal follow-up until the removal of the distractor. No studies were found that aimed to follow the study subjects until the completion of the orthodontic-surgical intervention. The planned anterioreposterior location of the distractor was not reported in 2 studies (Koudstaal et al., 2006a,b). In one study two different surgical approaches were used but the number of patients in each group was not reported (Gerlach and Zahl, 2003). The procedure for retaining the achieved expansion after removal of the distractor was not reported in nine Author's personal copy studies (Matteini and Mommaerts, 2001; Pinto et al., 2001; Neyt et al., 2002; Gerlach and Zahl, 2003; Ramieri et al., 2005; Koudstaal et al., 2006a,b; Scolozzi et al., 2007; Seitz et al., 2008). Positional changes measured on dental cast Belgium Patients in the included studies Abbreviations: MWD, maxillary widening device; DD, Dresden Distractor; TPD, transpalatal distractor; RPD, Rotterdam Palatal Distractor; ?, unknown. TPD 0 Prospective case series Belgium Belgium Neyt et al. (2002) Matteini and Mommaerts (2001) Pinto et al. (2001) 20 14e30 (21.5) 20 0 0 TPD TPD 0 0 Retrospective case series Prospective case series Germany Gerlach and Zahl (2003) 57 20 11e43 (18) 12e42 (20) 57 20 0 0 0 0 Magdeburg Netherlands Italy Koudstaal et al. (2006b) Ramieri et al. (2005) Prospective case series Germany Switzerland Germany Netherlands Tausche et al. (2007) Scolozzi et al. (2007) Hansen et al. (2007) Koudstaal et al. (2006a) 10 12e37 (25.8) 0 0 0 10 Complication Positional changes measured on dental cast, radiographic and clinical evaluation of dental and periodontal condition Positional changes measured on dental cast Pain perception on VAS scale Problems, obstacles, complications Positional changes measured on dental cast TPD TPD 0 0 10 29 13e20 (16.5) ? (26.4) 0 27 4 2 6 0 0 Positional changes measured on CT data Clinical experience 3D cephalometrics Clinical experience DD TPD DD RPD 10 8 12 13 18e6 (25.3) 13e15 (13.9) 17e36 (23,3) ? 10 0 12 5 0 8 0 2 0 0 0 6 0 0 Clinical experience MWD 0 Germany Seitz et al. (2008) Technical note, prospective case series Prospective case series Prospective case series Prospective case series Technical note, prospective case series Retrospective case series Prospective case series 22 14e34 (19.5) 22 0 0 Distractor Study design Origin Author, year of publication Table 2 e Overview of the included studies N Age range (median) years N, developmental deformity N, cleft lip palate N, other congenital deformity N, unknown diagnosis Main outcome variable Effects of bone-borne surgical assisted rapid maxillary expansion 169 The total number of patients included in the systematic review was 159. From the studies of the research group of Bruges, Belgium, only the study with the biggest patient sample (Neyt et al., 2002) was included for the total number of patients because there were overlapping patient samples. Sample size ranged from 8 to 57 patients. The age ranged from 11 to 43 years. Maxillary constriction was a developmental deformity in 121 (76.1%) patients, associated with cleft lip and palate in 16 (10.1%) patients, and 12 (7.5%) patients had other congenital malformations. In 10 (6.3%) patients from one study, the origin of the maxillary constriction was not reported (Gerlach and Zahl, 2003). Surgical intervention and distraction A description of the surgical interventions is summarized in Table 3. Five different distractors were used in the included studies. The Trans Palatal Distractor (TPD; SurgiTec NV, Bruges, Belgium e Pinto et al., 2001; Matteini and Mommaerts, 2001; Neyt et al., 2002; Ramieri et al., 2005; Koudstaal et al., 2006b; Scolozzi et al. 2007), the Rotterdam Palatal Distractor (RPD e Koudstaal et al., 2006a), the Magdeburg distractor (Martin Medizin-Technik, Tuttlingen, Germany e Gerlach and Zahl, 2003), the Dresden Distractor (DD e Tausche et al., 2007) and the Maxillary Widening Device (MWD e Seitz et al., 2008). An average latency period of 5.6 days (range 1e7) before the start of activation was found. The average rate of distraction was 0.66 mm/day (range 0.33e1 mm/day). No study opted to perform the minimally invasive open sky surgery as described by Glassman et al. (1984). Modifications of the Glassman approach were vertical corticotomy of the piriform aperture (Gerlach and Zahl, 2003; Tausche et al., 2007), midpalatal dysjunction (Pinto et al., 2001; Ramieri et al., 2005; Koudstaal et al., 2006a,b; Seitz et al. 2008), pterygoid and midpalatal dysjunction (Matteini and Mommaerts, 2001; Gerlach and Zahl, 2003), or a unilateral approach in cleft lip and palate patients (Ramieri et al., 2005; Koudstaal et al., 2006b; Scolozzi et al., 2007). In the anterioreposterior direction the distractors were either placed at the level of the maxillary second premolar (Pinto et al., 2001; Gerlach and Zahl, 2003; Ramieri et al., 2005; Scolozzi et al., 2007; Tausche et al., 2007; Seitz et al., 2008) or at the level of the fist molar (Matteini and Mommaerts, 2001; Gerlach and Zahl, 2003; Ramieri et al., 2005). Treatment related difficulties Seven studies were considered for evaluation of treatment related difficulties. A detailed overview is provided in Table 4. Difficulties related to bone-borne SARME Author's personal copy 170 Journal of Cranio-Maxillo-Facial Surgery Table 3 e Characteristics of the surgical intervention Author, year of publication Distractor Location of Osteotomies distractor Latency before Distraction Mean consolidation Fixed orthodontic start activation rate (mm/day) period (months) appliances during (days) consolidation Seitz et al. (2008) MWD P2 5 0.6 3 Yes Tausche et al. (2007) DD P2 2 0.96 3e6 Yes Scolozzi et al. (2007) TPD P2 1 0.66 2 ? 7 1 3 Yes 7 1 3 ? 7 Days 1 and 2: 0.33 Other days: 0.66 5 Yes 7 0.4 3 Yes 7 0.33 6 No 7 0.33 4 Yes Koudstaal et al. RPD (2006a) ? Koudstaal et al. TPD (2006b) ? Ramieri et al. (2005) P2 TPD M1 M1 Gerlach and Zahl (2003) Magdeburg P2-M1 Matteini and Mommaerts (2001) TPD M1 Pinto et al. (2001) TPD P2 Bilateral buccal corticotomies and midpalatal suture dysjunction Bilateral buccal corticotomies and a vertical corticotomy between 11 and 21 Unilateral buccal corticotomy with midpalatal suture dysjunction Bilateral buccal corticotomies and midpalatal suture dysjunction Uni/Bilateral buccal corticotomies and midpalatal suture dysjunction A) Bilateral buccal corticotomies and midpalatal suture dysjunction without pterygoid dysjunction B) Bilateral buccal corticotomies and midpalatal suture disjunction with pterygoid dysjunction C) Unilateral buccal corticotomies and midpalatal suture dysjunction with pterygoid dysjunction A) Bilateral buccal corticotomies and a vertical corticotomy between 11 and 21 B) Bilateral buccal corticotomies with bilateral osteotomy of midpalatal suture and pterygoid dysjunction Bilateral buccal corticotomies, midpalatal suture dysjunction pterygoid dysjunction Bilateral buccal corticotomies and midpalatal suture dysjunction Abbreviations: MWD, maxillary widening device; DD, Dresden Distractor; TPD, tranpalatal distractor; RPD, Rotterdam Palatal Distractor; ?, unknown. can be associated with the distractor, with the permucosal entry side of the distractor or associated with the surgical intervention itself. In 147 patients, 61 episodes of treatment related difficulties were reported (one patient can have more than one treatment related difficulty). More than half of the reported difficulties were appliance related (33/61). No big differences of distractor related problems were seen between patients with a congenital Author's personal copy Effects of bone-borne surgical assisted rapid maxillary expansion 171 Table 4 e Clinical report of treatment related difficulties Author, year of publication N Follow-up (months) Distractor Appliance related difficulties (N distractor) Permucosal difficulties (N patients) Surgical difficulties (N patients) Seitz et al. (2007) 22 D 3 MWD 1 loosening of distractor Not reported 2 midline shift 2 vertical displacement Scolozzi et al. (2007) 8C 12e36 TPD 1 abutment plate loose No difficulties Koudstaal et al. (2006a) 5D 8C 3 RPD No difficulties 1 dislocation of distractor No difficulties No difficulties No difficulties 1 additional hyrax needed due to extreme opening in front region in a osteopatia striata case Koudstaal et al. (2006b) 10 C 3 TPD 3 loosening of distractor 1 abutment plate loose 1 oronasal fistula 1 palatal abscess No difficulties Ramieri et al. (2005) 27 D 12 TPD 5 loosening of distractor 2 dislocation of distractor 8 palatal ulceration 1 mucosal ulceration in the vestibule No difficulties 3 abutment plate loose Gerlach and Zahl (2003) 10 6 Magdeburg No distractor failure 1 oronasal fistula No difficulties Neyt et al. (2002) 57 D 3e6 TPD 14 loosening of distractor 3 abutment plate loose 3 palatal ulceration 1 infraorbital hypoaesthesia 1 nasal bleeding 2 wound infections 3 cheek haematomas Abbreviations: D, developmental deformity; C, Congenital deformity. Table 5 e Evaluation of the orthodontic effects Author, year of publication Objective method used N T2 (weeks) Buccal tipping in degree (SD) % of expansion relative to IMD Ratio ICD:IMD ICD IPD IMD Tausche et al. (2007) 3D cephalometrics on virtual axial computer tomography model 10 17 Ramieri et al. (2005) Digitized plaster dental cast 11* 16# 2e3 2e3 23.1 22.2 19.6 20.5 14.9 21 1:0.65 1:0.95 Matteini and Mommaerts (2001) Digitized plaster dental cast 20 2e3 22.4 21.9 20.8 1:0.93 Pinto et al. (2001) Digitized plaster dental cast 20 2e3 28.8 25.9 20.4 1:0.71 Right P1: 3.0 Left P1: 3.9 Right M1: 3.5 Left M1: 2.5 P1: 0.9 (9.9) M1: -/-8.3 (9.6) Abbreviations: SD, standard deviation; ICD, intercanine distance; IPD, interpremolar distance; IMD, intermolar distance. * Without pterygoid dysjunction. # With pterygoid dysjunction. malformation (6/26) and patients with a developmental deformity (28/113). Most distractor failures, such as loosening or dislocation, occurred during the consolidation period and an intervention to solve the problem was not always needed. Difficulties associated with the permucosal entry side (ulceration of the palatal mucosa, palatal abscess and oronasal fistula) were reported 15 times. Surgically related difficulties were reported in 12 cases, of which four had an asymmetric opening of the maxillary segments and one case with osteopatia striata [OMIM: %166500] needed an additional hyrax-appli- ance because the bone-anchored expander alone did not result in posterior opening of the midpalatal suture (Koudstaal et al., 2006a). Orthodontic and orthopaedic effects Five studies were identified, which assessed the orthodontic and orthopaedic effects of the expansion: in four of them measurements were performed on dental casts (Matteini and Mommaerts, 2001; Pinto et al., 2001; Gerlach and Zahl, 2003; Ramieri et al., 2005) and in one on 3D CT data (Tausche et al., 2007). The study of Gerlach Author's personal copy 172 Journal of Cranio-Maxillo-Facial Surgery and Zahl (2003) could not be evaluated because the landmarks were not defined. Also two different surgical procedures were used without presenting the outcome data separately. Detailed information is provided in Table 5. Post-expansion results, without additional orthodontic interventions, showed more movement of the dorsal part of the palate when pterygoid dysjunction was part of the procedure and the distractor was placed at the level of the first molar. Using this procedure, the ratio between increases of intercanine to intermolar width was 1:0.93 (Matteini and Mommaerts, 2001) and 1:0.95 (Ramieri et al., 2005). Without pterygoid dysjunction and placement of the distractor at the level of the second premolar the ratio was 1:0.71 (Pinto et al., 2001), and 1:0.65 (Ramieri et al., 2005). In the latter three studies, patients had a developmental deformity and a TPD was used. In the CT study (Tausche et al., 2007) the percentage of the transmitted expansion of the screw was calculated by dividing the width increment of the anatomical structures by the amount of screw expansion. However, orthodontic intervention with fixed appliances had already started before the SARME. This bias makes it difficult to calculate the orthodontic effects of bone-borne SARME per se. Tipping of the teeth which would be used for anchorage in teeth-anchored SARME, was assessed in two studies but the CT study (Tausche et al., 2007) was biased for the above mentioned reason. Measured on dental casts the average tipping for first maxillary premolars and first maxillary molars was 0.9 buccal tip and 8.3 palatal tip, respectively (Pinto et al., 2001). Adverse dental effects and pain Ramieri et al. (2005) evaluated periodontal health and thermal sensitivity of the central incisors, premolars and molars. At follow-up 1 year after expansion, a slight increase of gingival recession was seen in 7% of the teeth and a loss of thermal sensitivity in 15% of the teeth. One study evaluated pain perception rated on a visual analogue scale ranging from 0 to 100. The pain did not exceed a level of 20 (Gerlach and Zahl, 2003). These figures should be interpreted with caution as the methods and descriptions of the results were not detailed. DISCUSSION This systematic review dealt with the effects of boneborne SARME and concerns an overall sample of 159 patients. The inclusion criteria that were used focused on larger studies with at least 5 patients. 23 publications were found on bone-borne SARME of which 10 were included in this review. Of the publications considered, three reported qualitative clinical experience, and 7 performed quantitative measurements. The heterogeneity of the retrieved publications and the wide variety of outcome variables posed serious restrictions in this attempt to review the literature in a quantitative systematic manner, and thus meta-analysis of combined data was not possible. Since the introduction of bone-borne SARME in 1999 (Mommaerts, 1999), the distractors as well as the surgical experience have been developing continuously. The TPD was the first bone-borne expander introduced and in 6 out of 10 studies included in this systematic review a TPD was used. Most of the reported difficulties associated with bone-borne SARME were found using the TPD, because all three studies with complications as main outcome variable used it. For the other appliances, no studies were found with complications as the main outcome variable. Two studies (Neyt et al., 2002; Ramieri et al., 2005) classified the difficulties encountered during surgery, distraction and consolidation according to Paley (1990). According to this classification, minor difficulties that are self-resolving (i.e., ulceration around the distractor) were also reported. As not all papers consistently reported complications and problems, it is not possible to draw any definitive conclusions about the difficulties associated with bone-borne SARME. It is possible that studies were compromised by the early experience of the surgeon, using early versions of the distractors. Differences were found using the transverse maxillary changes according to the associated surgical procedure. Without pterygoid dysjunction, and with the distractor placed at the level of the second premolar, the transverse opening between the maxillary halves was V-shaped with more expansion anteriorly than posteriorly. With pterygoid dysjunction and the distractor placed at the level of the first molar, the expansion was more parallel. For the assumed advantages of bone-borne SARME compared with tooth-borne SARME, very weak evidence was found for less tipping of teeth normally used for anchorage with tooth-borne appliances. Average buccal tipping of teeth in tooth-borne SARME is 6.48 for premolars and 7.04e9.63 for molars (Chung and Goldman, 2003; Byloff and Mossaz, 2004). In contrast, in boneborne SARME this was 0.9 buccal tip and 8.9 palatal tip, respectively (Pinto et al., 2001). However these results are based on only one case series study on 20 patients without a control group. For other assumed advantages no evidence was found from the data available in the studies. Although SARME, tooth-borne or bone-borne, is a well accepted treatment modality, no strict consensus exists for the surgical protocol, the distraction protocol as well as the consolidation (retention) of the SARME. We found four different surgical protocols, the rate of distraction varied from 0.33 to 1.0 mm daily, most studies had a latency period (before start of activation) of 7 days, but 1 and 2 days were also found (Scolozzi et al., 2007; Tausche et al., 2007). Most studies were performed using dental casts but SARME has not only an influence on the position of the teeth and the alveolar bone, but also on the hard and soft tissues in the mid-face, as the nasal floor, nasal cavity and the width of the nose. With currently available technology, a 3-dimensional volumetric analysis would be preferable to fully understand the changes that are produced by SARME. Although most encountered treatment difficulties were minor, the high incidence of distractor loosening Author's personal copy Effects of bone-borne surgical assisted rapid maxillary expansion 173 suggests the need to develop a better anchored distractor. Cost-effectiveness and patient perception have not been studied. Since more expanders are commercially available now there is a need for more research on the effects of tooth-borne and bone-borne SARME. A search in the International Clinical Trials Registry Platform of the World Health Organization (www.who.int/trialsearch) as well as in the International Clinical Trials Registry of the U.S. National institutes of Health (www. clinicaltrials.gov, both accessed April 11, 2008) did not reveal any ongoing controlled randomized clinical trials in this field. This might be due to the fact that the technique is still developing and performing a randomized clinical trial might be difficult. For this reason, another approach was chosen with the Eurocran Distraction Study. In this study patients to be treated by distraction osteogenesis in fourteen participating centres in Europe have been enrolled in a prospective registry and followed in a standardised way until 24-month after surgery (Shaw et al., 2002; Kuijpers-Jagtman and Wijdeveld, 2005). Future research on bone-borne SARME should aim to demonstrate the following features: Randomized clinical trial design. Control group of tooth-anchored SARME. 3-dimensional volumetric analysis of bony and soft tissue changes. Standardised surgical protocol. Standardised distraction protocol. Standardised reporting of treatment difficulties. Interim follow-up of 3 months after removal of the distractor. Follow-up of at least 1 year after the completion of the combined orthodontic-surgical treatment. CONCLUSION This systematic review has demonstrated currently there are no RCT’s or CCT’s published on bone-borne SARME. The expected advantages when compared with tooth-borne SARME show that so far only very weak evidence exist that there is less buccal tipping of the teeth used as anchor teeth in tooth-borne expansion. The heterogeneity of the retrieved publications and the wide variety of outcome variables posed serious restrictions on the review of the literature in a quantitative systematic manner. There is a need for well designed clinical trials research on the effects of tooth-borne and boneborne SARME. ACKNOWLEDGMENTS The chairperson of the Eurocran Distraction Osteogenesis Group is Prof. Anne Marie Kuijpers-Jagtman and the members are: Hospital of Plastic Surgery, Polanica Zdrój, Poland, Prof. K. Kobus; Free University Medical Centre, Amsterdam, The Netherlands, Dr. E. Becking; Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands, Prof. P. Stoelinga, Dr. W. Borstlap; Morriston Hospital, Swansea, United Kingdom, Dr. A.W. Sugar; Blackburn Royal Infirmary, Blackburn, United Kingdom, Dr. M. Morton; Erasmus Hospital and Queen Fabiola Children’s Hospital Université Libre de Bruxelles, Brussels, Belgium, Prof. C. Malevez; General Hospital Sint Jan, Bruges, Belgium, Prof. M. Mommaerts; Medical University Hannover, Germany, and General Hospital Sint Jan, Bruges, Belgium, Dr. G. Swennen; Medical University Leipzig, Germany, Prof. A. Hemprich, Dr. T. Hierl; Hôpital Trousseau, Paris, France, Dr. P.A. Diner, Dr. C. Tomat; Helsinki University Central Hospital, Helsinki, Finland, Dr. J. Hukki, Dr. K. Hurmerinta; Bellaria Hospital University of Bologna, Bologna, Italy, Dr. A. Bianchi; St. Anna University Hospital, Ferrara, Italy, Prof. L. Clauser. Their input in this systematic review is highly appreciated. References Barber AF, Sims MR: Rapid maxillary expansion and external root resorption in man: a scanning electron microscope study. 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KUIJPERS-JAGTMAN, DDS, PhD, FDSRCS (Eng) Department of Orthodontics and Oral Biology Radboud University Nijmegen Medical Centre 309 Dentistry PO Box 9101 6500 HB Nijmegen The Netherlands Tel.: +31 24 3614005 Fax: +31 24 3540631 E-mail: [email protected] Paper received 1 September 2008 Accepted 3 June 2009