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Citation Information : Australasian Orthodontic Journal. Volume 38, Issue 1, Pages 41-50, DOI: https://doi.org/10.21307/aoj-2022.005
License : (CC-BY-4.0)
Received Date : October-2021 / Accepted: December-2021 / Published Online: 17-January-2022
The objective of the present study was to compare the dentoskeletal effects of mini-screw-assisted rapid maxillary expansion (RME) in children with different body mass index (BMI) percentiles.
The study was performed on 20 patients who were divided into two groups based on their BMI percentiles as normal-weight (
A statistically significant increase was observed in maxillary intermolar and intercanine distances and palatal area measurements in both groups (
Mini-screw-assisted RME treatment significantly increased maxillary intermolar and intercanine width, and the palatal area in both groups; however, there was no significant difference between the BMI groups.
The number of overweight and obese individuals is increasing at an alarming rate in both developing and developed countries. According to the World Health Organization, childhood obesity has become a significant health problem as it rapidly increases. Based on predictions, 254 million children aged 5 to 19 are projected to become obese by 2030.1 While obesity is generally related to high calorie intake and low physical activity, genetic factors and hormonal disorders may also play a role. Obesity can lead to an increase in skeletal growth by amplifying bone density. Accordingly, it is known that obese children complete their cervical vertebral maturation prematurely when compared to their normal-weight peers.2–4
Rapid maxillary expansion (RME) is a method frequently applied to treat a maxillary transverse deficiency in children and adolescents.5,6 A variety of expansion devices have been developed but tooth-borne appliances have been mostly used. The disadvantages of tooth-borne expansion appliances involve the buccal tilting of the supporting teeth and a potential increase in gingival recession. Contemporary bone-borne RME appliances are used as an alternative to tooth-borne appliances to overcome the tipping disadvantages.7–10
The objective of the present study was to compare the dento-skeletal effects of mini-screw-assisted RME in children of different body mass index (BMI) percentiles by analysing postero-anterior (P-A) and lateral cephalometric radiographs in additional to three-dimensional (3D) models.
The study was conducted with the approval of Ordu University Local Ethics Committee (2018/95) on 20 patients (17 female, 3 males; mean age: 13.60 ± 1.39) who presented to Ordu University Faculty of Dentistry Department of Orthodontics for orthodontic treatment. Each patient complained of a unilateral or a bilateral buccal crossbite resulting from a maxillary transverse deficiency. Informed consent was obtained from the parents prior to commencement. Individuals with poor oral hygiene, severe periodontal disease, a systemic disorder, a craniofacial anomaly, or a history of previous orthodontic treatment were excluded from the study. The sample size was calculated using the G*Power software program (version 126.96.36.199; Axel Buchner, Universität Düsseldorf, Düsseldorf, Germany) and the total sample size required to identify a moderate effect (0.60) with 80% power was found to be 19.
The patients were divided into two groups based on their BMI percentiles: the participants in the first group were normal-weight individuals (n = 10), while the second group was comprised of overweight and obese individuals (n = 10). The patients in both groups received intraoral and extraoral orthodontic photographs plus impressions and their chronological ages were recorded at their first appointments. The body weight and height calculations were performed using a digital scale with a sensitivity of 0.1 kg and a 1 mm graduation stadiometer.
The lateral cephalometric and P-A cephalometric radiographs were captured by a cephalometer (Kodak 8000C Digital Panoramic and Cephalometric System, Cephalostat, Corestream Health Inc. Rochester NY, USA), while the patient was in natural head position with their lips relaxed. The patient’s dental models were obtained and pre-treatment intraoral and extraoral photographs were also recorded.
A mini-screw-assisted RME appliance was designed for each patient. After an intra-oral fit of the appliance was checked by the clinician, mini-screw holes were placed in the acrylic. Following palatal local anaesthesia, four mini-screws, two on the right and two on the left side, were inserted between the first and second premolars and the mesial area of the first molar (Fig. 1). The parents were instructed about the screw-turning protocol after the placement of the appliance.
For both groups, the expansion screw was activated one-quarter of a turn in the morning and in the evening (one-quarter turn: 0.2 mm) during the first week. After fourteen-quarter turns had been activated, a daily one-quarter-turn routine was performed during the following weeks. The screw-turning protocol was maintained until the palatal cusps of the maxillary first molar were aligned with the buccal cusps of the mandibular first molar. Following the completion of the active expansion, the expansion screw was fixed by composite resin cured in the screw mechanism and the appliance was passively intraorally maintained for three months. After the retention phase, lateral and P-A cephalometric radiographs, dental models, intraoral and extraoral photographic records were taken.
The linear and angular measurements determined on lateral and P-A cephalometric radiographs were carried out using cephalometric software (Facad, trial version, Linkoping, Sweden) (Figs. 2–4).
The plaster models were scanned by a three-dimensional scanner (3 Shape Trios 3, Copenhagen, Denmark) and the acquired data converted into an .stl format. Linear and area measurements were performed on the pre-treatment and post-treatment model images using a dedicated program (Mesh Mixer, USA) (Figs. 5, 6).
To determine examiner reliability, all measurements were repeated by one researcher on randomly-selected radiographs and model images after 3 weeks.
The statistical analysis was carried out using the SPSS software program (SPSS Inc., Windows compatible version 20; Chicago, IL, USA). The data distribution was evaluated by applying the Shapiro–Wilk test of normality. The independent t-test was applied to the normally distributed parameters, while the Mann–Whitney U test was applied to the parameters not showing a normal distribution for the intergroup comparison of cephalometric and model measurements. For the within-group comparison of values, the paired t-test was applied to the normally distributed parameters, while the Wilcoxon signed-rank test was applied to the values not showing a normal distribution. A value of P < 0.05 was acknowledged to be statistically significant.
Of the individuals included in the present study who successfully completed the RME procedure, the mean age was 13.85 ± 1.37 in the normal-weight group and 13.35 ± 1.44 in the overweight-obese group. There was no statistically significant difference related to age between the two groups (P > 0.05). The study initially recruited 24 patients; however, three patients from the normal-weight group and one patient from the overweight-obese group were excluded from the study due to poor oral hygiene-induced gingival hyperplasia, and mini-screw loss and lack of hygiene, respectively.
The intra-class correlation coefficients for all measurements were > 0.920, confirming measurement reliability.
The comparison of the initial lateral cephalometric film values of both groups is provided in Table I. The values were found to be similar in each group (P > 0.05). The intra-group comparison of the changes in the lateral cephalometric parameters induced by RME is shown in Table II. While a significant change was observed in the ANB, SN-GoMe, Z angle, Wits appraisal, total anterior facial height and lower anterior facial height parameters in the normal-weight group (P < 0.05), a statistically significant change was observed in the gonial and nasolabial angles in the overweight-obese group. Changes occurring in other lateral cephalometric radiograph parameters were not statistically significant (P > 0.05). The comparison of differences occurring in lateral cephalometric radiographic measurements before and after the RME treatment is shown in Table III. A statistically significant difference was observed only in nasolabial angle parameters upon comparing the cephalometric changes between the groups (P < 0.05).
A comparison of the initial P-A cephalometric film values of both groups is shown in Table I. The values were found to be similar in each group (P > 0.05). The intra-group comparison of the RME-induced changes is shown in Table II. A statistically significant increase in latero-nasal and maxillary widths was observed in the P-A radiographic measurements of the overweight-obese group (P < 0.05). The changes occurring in P-A parameters in the normal-weight group were not statistically significant (P > 0.05). A comparison of the differences in P-A radiographic measurements before and after RME treatment is presented in Table III. There was a significant difference in latero-nasal width parameters between the groups (P < 0.05).
A comparison of the initial 3D model measurement values of both groups is presented in Table I. The initial parameters were found to show similarities between the groups (P > 0.05). The intra-group comparison of changes induced by RME is shown in Table II. There was a statistically significant increase observed in maxillary intercanine and intermolar distances and palatal area measurements in both groups (P < 0.05). The change in mandibular intercanine and intermolar width parameters was not statistically significant in either group (P > 0.05). A comparison of the differences between the pre-RME-treatment and post-RME-treatment is presented in Table III. No significant difference was found between the groups upon comparing the measurement changes on the 3D models.
In the present prospective clinical study, normal-weight and obese-overweight individuals each with a transverse maxillary deficiency underwent an expansion procedure using a mini-screw-assisted RME appliance.
In a tooth-borne RME appliance, the supporting teeth may incline toward the buccal and, as a result, periodontal problems may arise.7,8 Similarly, the skeletal effect is limited in tooth-borne RME appliances. With the advent of mini-screws, mini-screw-assisted RME appliances have been designed to promote enhanced skeletal support and effect. Numerous studies have evaluated the dental and skeletal effects of tooth-borne and mini-screw-assisted RME appliances;11–13 however, no studies assessing the dental and skeletal effects of an RME in children with different BMI percentiles have been conducted.
Lim et al.14 reported that mini-screw-assisted RME without surgically assisted bone damage is an effective method for the treatment of a maxillary transverse deficiency in adolescents. In the present study, a mini-screw-assisted RME appliance was placed to create more skeletal change and enable expected post-treatment stability.
Obesity is recognised to have a negative effect on general health status over time. Childhood obesity may lead to metabolic and cardiovascular problems, gastrointestinal diseases, orthopaedic complications, and bone fractures.15–17 While there are several methods by which body mass might be evaluated, as the most reliable and practical method, the BMI percentile was used in the present study to assess the BMI of the participating children.18 The BMI percentile can be expressed as a percentage generated from a graphical or percentage calculator and specifically determined for any age or gender. Individuals below the fifth percentile are regarded as underweight; if the BMI falls between the fifth and eighty-fourth percentile, it reflects a normal-weight; if it falls between the eighty-fifth and ninety-fourth percentile, the individual is considered overweight; and individuals falling on the ninety-fifth percentile or above are regarded as obese.19
Obesity is the primary factor in the development of obstructive sleep apnoea (OSA).20 It is suggested that tooth-borne RME appliances can be used in the treatment of OSA in children.21 In recent years, mini-screw-assisted RME appliances have been widely used to achieve a greater skeletal effect.7 Hur et al.22 reported that mini-screw-assisted RME appliances could be an effective treatment alternative in the management of adults with moderate sleep apnoea by increasing the airway dimension and reducing resistance. In addition, Saloom et al.23 evaluated orthodontic movement in obese and normal-weight patients and reported that obese subjects needed less time to achieve tooth alignment compared with normal-weight patients; however, this difference was not statistically significant. Therefore, the present study investigated normal-weight and obese-overweight patients following expansion generated by a mini-screw-assisted RME appliance.
Numerous studies have been conducted to determine the effects of obesity on bone metabolism.4,24 Giuca et al.4 evaluated cervical vertebrae maturation by applying a carpal analysis of 50 children. It was concluded that obese children had higher mean values and significantly higher cervical vertebrae maturation scores when compared to normal-weight children. Similarly, following a study investigating the effects of childhood obesity on bone density and size, Leonard et al.20 stated that the vertebral bone densities and the whole-body frame sizes of obese children were greater than non-obese children. Although there are studies evaluating palatal suture maturation in adolescents and children by three-dimensional methods,25–28 no study concerned with palatal suture maturation in children or adolescents with different body mass indices has been identified.
Following a study in which different screw-turning protocols were applied, Perillo et al.29 stated that RME increased the distance between the maxillary molars. Chung and Font30 applied a conventional Haas-type RME appliance on 20 children whose mean age was 11.7 years and evaluated the effects on dental casts and on lateral and P-A cephalometric radiographs. Based on the cast measurements, an increase in maxillary intermolar and interpremolar widths was observed after the expansion procedure. There were further increases in nasal and maxillary widths based on P-A cephalometric measurements. In the present study, an increase was observed in intermolar and intercanine distances and palatal area measurements in both groups based on measurements conducted on the 3-D models. However, increases occurring in measurements performed on 3-D models did not reflect a statistically significant difference between the groups. A statistically significant increase was observed in latero-nasal and maxillary widths in the overweight-obese group based on measurements performed on the P-A cephalometric radiographs. Similarly while a statistically significant change occurred in the gonial and nasolabial angles in the obese-overweight group, based on lateral cephalometric films, a significant change was detected in the SN-GoMe, Wits, FMA, Z angle, total and lower anterior facial height parameters in the normal-weight group as a result of the mini-screw-assisted RME.
The present study had limitations. The number of patients decreased due to the specific clinical study conditions, co-operation problems, oral hygiene and periodontal issues. Future prospective clinical studies should be designed to incorporate larger sample sizes.
Mini-screw-assisted RME treatment significantly increased maxillary intercanine width, intermolar width and the palatal area in both groups. The increase in these measurements was not statistically significant between the groups.
An increase in latero-nasal and maxillary widths was observed in the overweight-obese group on P-A cephalometric radiographs. A significant difference in latero-nasal width was observed between the groups.
There was a statistically significant change in the gonial and nasolabial angles in the obese-overweight group. A significant change was observed in the ANB, SN-GoMe, Z angle, Wits appraisal, total anterior facial height and lower anterior facial height measurements in the normal-weight group. A significant difference was noted in the gonial and nasolabial angles in the overweight-obese group.