Bone-borne distractor versus tooth-borne distractor for maxillary expansion : a Systematic Review Distrator ósseo versus distrator dentário para expansão maxilar : uma revisão sistemática Distractor óseo versus distractor dental para la expansión maxilar : una revisión sistemática

The etiology of transverse maxillary deficiency is considered multifactorial, and has a deleterious effect on the bone development of the maxilla and nasal cavities, causing maxillary atresia and posterior crossbite. The objective of this systematic review was to compare in the scientific literature the effectiveness of the maxillary disjunction treated using dental distractor versus bone distractor. A systematic literature review was performed using the Science Direct, Embase, Cochrane Collaboration Library, and PubMed / MEDLINE databases. The search strategy provided a total of 119 studies. After screening by reading the titles and abstracts, seven articles met all the criteria and were included in this systematic review. Studies have shown that the choice of type of orthodontic-orthopedic appliance is directly related to the prior individualized planning of each patient. With regard to patients who are in the development phase, the recommendation is the use of dental maxillary expanders, such as the Hyrax appliance. In addition, it is not recommended to perform rapid Research, Society and Development, v. 9, n. 11, e259119055, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.9055 3 maxillary expansion in adult patients, due to the expansion resistance that occurs in the palatine sutures. The treatment of patients with closed median palatine suture must be done by surgically assisted maxillary expansion.

maxillary expansion in adult patients, due to the expansion resistance that occurs in the palatine sutures. The treatment of patients with closed median palatine suture must be done by surgically assisted maxillary expansion.

Introduction
In order to establish an ideal occlusion, the upper dental arch needs to be proportionally larger than the lower dental arch, causing the palatal cusps of the premolars and maxillary molars to adequately adapt to the occlusal fossae of the premolars and mandibular molars. Treatments involving dental malocclusions are often associated with corrections of transverse maxillary deficiencies (Cappellette-Júnior et al., 2017;Souza et al., 2018).
The etiology of transverse maxillary deficiency is considered multifactorial, and has a deleterious effect on the bone development of the maxilla and nasal cavities, causing maxillary atresia and posterior crossbite (Park et al., 2017;Cappellette-Júnior et al., 2017).
Rapid maxillary expansion (RME) is indicated to treat conditions that are related to transverse maxillary deficiency, through the use of an orthodontic-orthopedic appliance in young patients, in which the process of ossification of the medial palatal suture has not been completed (Zhang et al., 2017;Sánchez et al., 2020).
The mechanism of action of RME is based on the use of forces that are applied to the teeth and the alveolar process, thus causing the disjunction of the maxillary bones, expanding the median palatal suture (Canan, Şenişik., 2017). The maxillary expanders are a type of orthodontic-orthopedic device used to promote RME, through the rupture of the medial palatal suture. The principle of action of these devices is based on the use of an expander screw that is positioned transversely to the center of the palate, resting on the upper posterior teeth, with or without mucous support (Hassan et al., 2014;Alghamdi et al., 2017). Development, v. 9, n. 11, e259119055, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.9055 However, in adult patients, the median palatal suture is closed, making it impossible to correct transverse maxillary discrepancies through the use of intraoral orthodontic appliances.
The osteogenic activity of the median palatal suture corresponding to the transverse growth of the palate continues until 16 years of age for females and 18 years of age for males. To obtain a better result in the bone expansion process, other procedures such as surgically assisted rapid maxillary expansion (SARME) have been used (Krüsi et al., 2019). The therapeutic protocol for this type of approach is based on the combination of orthodontic procedures and different surgical techniques that promote an increase in the space of the dental arch (Fonseca et al., 2019). Therefore, the objective of this systematic review was to compare in the scientific literature the efficacy of the maxillary disjunction treated using dental distractor versus bone distractor.

Material and Methods
This study followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) Statement (Moher, Liberati., 2009;Honório, HM, Santiago., 2018). The following review question was developed according to population, intervention, comparison, and outcome (PICO): "Bone-borne distractor versus tooth-borne: What is the most appropriate treatment method for rapid maxillary expansion?" and a keyword search was performed. A literature search was performed in September of 2020 in the following electronic databases: Science Direct, Embase, Cochrane Collaboration Library, and PubMed/MEDLINE.
The search was carried out without time and language restrictions. Hand searches were also conducted by cross-checking the reference lists of the included articles. Duplicates were removed upon identification. Manuscripts that were not published in English were translated for further evaluation. The search strategy was based on combinations of the following keywords: ("Maxillary expansion", "Orthognathic surgery", "Skeletal stability", "Surgically assisted rapid maxillary expansion", "bone-borne distraction", "Tooth-borne distraction"[tw]).
The reviewer independently screened and assessed potential articles. Studies that did not fulfil the inclusion criteria were excluded. In the first stage, the titles and abstracts of all retrieved reports were screened for potentially eligible studies. The full text articles of the previously identified studies were then examined in detail according to predefined eligibility criteria for inclusion in the qualitative review. Disagreements were solved by discussion between the authors. Eligibility criteria: The review included randomized controlled trials, Research, Society and Development, v. 9, n. 11, e259119055, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.9055 6 comparing the bone distraction device with the dental distraction device for maxillary expansion. Exclusion criteria: Animal studies, opinion articles, letters to the editor, review articles, interviews, updates, abstracts, and unpublished studies were excluded. The review authors independently screened the articles for data extraction. Any disagreements were resolved by discussion.

Study selection and characteristics
The search strategy developed in this systematic review identified a total of 119 studies located in the evaluated databases. After screening by reading the titles and abstracts and excluding duplicate articles, 13 studies were considered potentially eligible and read in full by the evaluators. At the end of the analysis, seven articles published between 2009 and 2016 met all inclusion criteria and were selected for systematic review. The flowchart applied for the article selection and selection process is illustrated in Figure 1. All the studies included performed a comparative analysis between the maxillary disjunction treated by a dental versus bone distractor. In total, 264 patients were evaluated in the ten selected studies, with the sample ranging from 28 patients (Kunz et al., 2016) to 50 patients (Landes et al., 2009). The follow-up time ranged from 3 months (Seeberger et al., 2015) to 22 months (Nada et al., 2012). The main methodological aspects and observed results can be seen in Table 1.

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In conclusion, the results of this prospective randomized patient trial show that there is no significant difference between the two groups. In surgically assisted rapid maxillary expansion, when using either a boneborne or toothborne distractor, the widening achieved at dental level is stable at the 12month follow up. Over-correction does not seem to be necessary. Landes et al. (2009)

Main results
The selected studies point out the importance of an individualized treatment, making a plan according to the individual characteristics of each patient. Koudstaal et al. (2009) point out that patients diagnosed with skeletal maturation and transverse maxillary hypoplasia, the performance of SARME associated with the use of dental distractors provided a stable clinical result, less invasive and with a lower financial cost. The author also points out that there is an indication for a bone distractor (Rotterdam palatal distractor) in patients with congenital deformity and extremely narrow jaws.
In the study developed by Landes et al. (2009), the authors concluded that dental distractors should be chosen whenever the symmetry of the dental arch is in good periodontal condition, whereas bone distraction in cases of great space limitations, reduced number of teeth and compromised parodontics at the price of a more asymmetric expansion. Nada et al. (2012) described that the amount of tooth expansion increased significantly from canines to molars through bone distraction, while it tended to be more parallel along the arch with tooth expansion.
The study by Zandi et al. (2014) obtained strong points for the present analysis: a randomized clinical study design; operation of all patients by the same surgeon using uniform surgical technique, expansion protocol and distraction device (in each group); and using an advanced imaging technique to evaluate the results. The dental and bone devices produced a V-shaped expansion of the dentoskeletal structures with greater widening at the level of the dental arch than in the nasal floor area (segmental inclination). Subsequently, parallel expansion of the dental arch, palatal bone and nasal floor was observed. The amount and pattern of expansion were not significantly different between maxillary expansion through the dental and bone distractor. The overall rate of complications was negligible in both Development, v. 9, n. 11, e259119055, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.9055 12 techniques. The selection of the distraction device should be based on the needs of each individual patient.
In the study by Seeberger et al. (2015), both SARME with dental or bone distractor are effective treatment modalities to correct transversal maxillary deficiencies. Bone devices have been found to cause greater widening of the skeletal nasal floor compared to dental devices.
The nasal floor had a V-opening from anterior to posterior, regardless of the device used. In the first molar, the dental device group showed significantly greater buccal inclination than the bone device group. For Kunz et al. (2016), both a Hyrax device and a transpalatal distractor can be used to obtain transverse expansion of a narrow maxilla with the help of surgery. The Hyrax appliance should result in a parallel expansion pattern with the transverse increase in its largest axis between the premolars. The transpalatal distractor should be selected whenever a more V-shaped pattern of transverse expansion with a more anterior maximum increase is necessary.

Discussion
The maxilla shows a different behavior during human development, showing an antero-posterior growth through the remodeling process, where bone deposition and reabsorption occurs. The horizontal growth of the maxillary arch is accomplished by remodeling the maxillary tuberosity. These bones are connected by a cartilaginous tissue that is later replaced by mineralized tissue. The medial palatal suture is located in the anteroposterior direction, associating the base of the skull with the facial skeleton, being responsible for the growth of the maxilla in the transversal direction (Enlow, Hans., 2012). Cappellette-Júnior et al. (2017) and Park et al. (2017), mentioned that transverse maxillary deficiencies can cause maxillary atresia, asymmetric facial growth, positioning and functional deviation of the mandible, periodontal problems and dentofacial involvement.
However, when these skeletal deformities are correctly diagnosed, they adapt better to orthopedic treatment, when compared to other deformities present in the regions of the craniofacial complex. These findings corroborate the present study, in which it was observed that the performance of SARME associated with the use of dental distractors provided good results in the treatment of atrophic jaws.
According to Hartono et al. (2018), in order to establish the method to be used for the correction of transverse maxillary deficiency, one must take into account the quantity and quality of orthodontic anchorage of the expanders. Most clinical failures associated with RME Development, v. 9, n. 11, e259119055, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i11.9055 13 when using only the orthodontic appliance occur due to resistance to expansion, as well as the presence of pain during bone expansion. In adult patients, due to the closure of the palatal suture, it is not feasible to perform the treatment using only orthodontic appliances, in which case a SARME is indicated, in which a combination of procedures is performed to obtain better results. These findings are in agreement with the results observed in the present systematic review, in which it was possible to observe that the selection of the distraction device must be based on the needs of each individual patient.
According to Algharbi et al. (2018) and Maspero et al. (2020) the Hyrax orthodonticorthopedic appliance is the most commonly used in young people, due to its easy adaptation, being activated by the patient or guardian with professional guidance through an intraoral device. Activation is painless, and occurs between 2 to 4 weeks, and should be used for a minimum of 3 months. It has advantages related to hygiene, not causing ulcerative and erythematous lesions in the palatal mucosa. However, there are other types of expanders, which vary according to teeth conformity (Machado et al., 2012;Gómez et al., 2019). In the present systematic review, it was observed, as shown by the study by Kunz et al. (2016), that the use of the Hyrax appliance promotes a parallel pattern of expansion with the transverse increase in the largest axis between maxillary premolars. However, when transverse expansion is indicated with a maximum increase earlier, one should choose to use a transpalatal distractor.

Conclusion
In view of the diagnosis and indication of maxillary expansion, it is up to the professional to choose the type of expander device as well as the expansion protocol to be used, however the choice of the type of orthodontic-orthopedic device is directly related to the prior individualized planning of each patient. With regard to patients who are in the stage of pubertal development, the recommendation is the use of dental maxillary expanders, such as the Hyrax appliance. RME is a procedure that has several advantages in the treatment of transverse defects of the upper arch. However, this procedure is limited in adult patients, due to an expansion resistance that occurs in the maxillozygomatic and maxillofrontal sutures. The treatment of patients with closed median palatal suture should be done through SARME, using a combination of procedures, orthodontic and surgical, thus providing better results in the treatment of patients with transverse maxillary deficiencies.