|Year : 2020 | Volume
| Issue : 2 | Page : 29-37
Multislice computed tomography evaluation of the expansion achieved by the nonextraction treatment of orthodontic cases using Damon system
Yasmine M Sayed MDS 1, Safaa M Gaballah2, Eman M El Shourbagy2
1 Department of Orthodontic, Faculty of Dentistry, Tanta University, Tanta, Egypt
2 Department of Orthodontic, Faculty of Dentistry, Cairo University, Cairo, Egypt
|Date of Submission||03-Aug-2018|
|Date of Acceptance||18-Oct-2018|
|Date of Web Publication||26-Sep-2020|
Yasmine M Sayed
Department of Orthodontic, Faculty of Dentistry, Tanta University, Tanta 27941
Source of Support: None, Conflict of Interest: None
The purpose of this study is to evaluate the dental, alveolar changes and behavior of teeth movement during expansion achieved by the nonextraction treatment approach of crowding cases using the Damon system.
Materials and methods
High-resolution multislice computed tomography (MSCT) imaging was performed pretreatment (T1) and posttreatment (T2) on a sample composed of twenty patients aged 17.8 ± 3.7 years in average selected based on a pretreatment class I skeletal and molar relationships, and moderate crowding range between 4.0 and 9.0 mm for the maxilla and 2.0 and 6.0 mm for the mandible. On the Digital Imaging and Communications (files obtained from MSCT scans, dental and alveolar measurements were recorded including interocclusal, interapical widths, angulations of the maxillary and mandibular teeth and four bilateral bone thickness distances at the furcation level.
The evaluation of the study was performed by detecting the dental and alveolar changes between pretreatment and posttreatment MSCT scans. Paired t test was used for statistical analysis. The interocclusal to interapical ratio indicated that, the roots moved by the same distance as the crowns except the canines roots moved 15 times as the crowns. While in the mandible, the roots of the premolars and molars moved less than the crowns but in the canines the opposite was happened. There was a significant increase of the axis angles of the maxillary canines and a significant decrease of the axis angles of the mandibular second premolars and first molars. This expansion resulted in a significant decrease of the buccal bone thickness and alveolar width and a significant increase of the palatal and lingual bone thickness.
The results of this study revealed that the expansion produced a small amount of uprighting in the maxillary teeth and a more significant degree in the mandibular teeth except the mandibular first premolars, were tipped buccally.
Keywords: Damon system, expansion, nonextraction, self-ligating brackets
|How to cite this article:|
Sayed YM, Gaballah SM, El Shourbagy EM. Multislice computed tomography evaluation of the expansion achieved by the nonextraction treatment of orthodontic cases using Damon system. Tanta Dent J 2020;17:29-37
|How to cite this URL:|
Sayed YM, Gaballah SM, El Shourbagy EM. Multislice computed tomography evaluation of the expansion achieved by the nonextraction treatment of orthodontic cases using Damon system. Tanta Dent J [serial online] 2020 [cited 2020 Oct 31];17:29-37. Available from: http://www.tmj.eg.net/text.asp?2020/17/2/29/296176
| Introduction|| |
Crowding is one of the most common problems faced by clinical orthodontists. Various orthodontic philosophies exist with regard to the resolution of crowding, one of them is dental expansion. Several methods have been used to achieve expansion; a common method is dental archwire expansion. This quest has inspired the development of self-ligating brackets aimed at providing the most effective possible treatment. The Damon self-ligating bracket was introduced to the market in 1996. Dr Damon claimed that adequate expansion could be achieved with the Damon system, without expanders. Damon also compared his expansion to the Fränkel functional appliance-type arch widening and stated that, ' The action of the small round archwire (0.014 inch) in the large lumen produces posterior transverse arch widening that accommodates most complete dentitions even in severely crowded arches and without the use of high-force palatal expansion' .
A constant agreement was found among studies that the Damon system produced a statistically significant expansion in all measurements in both arches with the most of the expansion occurred at the premolars ,,,,,,,. Whereas another study found that a significant change was not seen in the canine area . Also showed that, the maxillary arch expansion produced a 0.5° palatal uprighting of the maxillary molars during treatment. While, Jackson found that, the amount of tipping did not show a significant association in either group.
Cattaneo et al. investigated the torque capabilities of active and passive self-ligating brackets using CBCT three-dimensional (3D) imaging analysis and found that following treatment, a significant proclination was seen for the mandibular front teeth.
Arandomized trialbyFleming et al. revealed that, a small amount of increased buccal crown inclination was found; the degree of buccal flaring was slightly greater in the Damon Q group, with 0.66° more change than with in-vation; however, this difference did not have statistical significance.
The current clinical trial aimed to evaluate the dental, alveolar changes and behavior of teeth movement during expansion achieved by the nonextraction treatment approach of crowding cases using the Damon system using multislice computed tomography (MSCT) scans.
| Materials and Methods|| |
The sample of this study consisted of 20 patients treated with a nonextraction approach using the Damon Q system appliance (Ormco Corporation, West Collins Avenue Orange, California, USA) in the Orthodontic Department, Faculty of Dentistry, Tanta University. The patient's age ranged from 13 to 23 years at the start of the treatment, good oral hygiene, permanent dentition, class I skeletal relationship with an acceptable soft tissue facial profile, class I molar relationship, and moderate maxillary and mandibular dental arch crowding. Patients who had received any orthodontic treatment, extraction of any permanent teeth except third molar, skeletal discrepancy, and presence of supernumerary teeth or other congenital anomalies were excluded from selection. Written informed consent was obtained from each patient before orthodontic treatment. MSCT scans were taken pretreatment (T1) after thorough clinical examination with medical and dental history and posttreatment (T2) to determine the changes that occurred during treatment.
MSCT scans were carried out by a trained radiographer. All examinations were performed in the same radiology center. Each patient was positioned horizontally on the scanner table with the Camper's plane perpendicular to the ground. All CTs were obtained with patients in centric occlusion. During scanning, the patient's head was fixed, the perpendicular light beams of the machine were used to standardize the head position in the three planes, thus allowing comparison of the images achieved before and after treatment. Because metal artifacts can influence imaging quality and diagnostic accuracy, the lingual retainers were bonded after CT scanning.
High-resolution MSCT imaging was performed using a Hi Speed NX/i Pro unit (Toshiba Activision 16, Kashiwazaki City, Niigata Prefecture, Japan). The helical scan was set at 120 kV tube voltage, and current of 187 mA. The pitch (feed per rotation/total slice collimation) was 0.75/0.5 mm. The axial images were reconstructed using 2 mm thick slices with 2 mm intervals. The CT images were stored by using Digital Imaging and Communications (DICOM) as a medical-image file format into a portable hard disc. DICOM files were handled using the Millensys DICOM viewer version 8.2 software (Millensys DICOM viewer ver. 8.2 software; Nasr City, Cairo, Egypt).
A clear view of the object being measured was obtained using tools such as rotate, clipping, and zoom. Once a clear and distinct view of the arch or teeth under study was utilized, measurements were taken and recorded. Pictures and data for each patient were recorded. Measurements were obtained on the frontal section view after the image was coordinated in the sagittal and coronal views, unless otherwise stated [Figure 1].
|Figure 1: An example of a three-dimensional coordinate system of a patient's CT scan. CT, computed tomography.|
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Arch width, tooth angulation, and bone thickness were measured at pretreatment (T1) and posttreatment (T2). The arch width measurements included not only the occlusal portion of the canine, first and second premolars, and first molar teeth, but also the interapical areas of each of the respective teeth, along with the angulations of each tooth. Interocclusal distance (IOD) and interapical distance (IAD) were measured by the same methods of Askari . IOD for canines was measured from cusp tip to cusp tip. IAD was measured from apex to apex [Figure 2]a, [Figure 2]b.
|Figure 2: (a) Maxillary canine IOD and IAD measurements. (b) Mandibular canine IOD and IAD measurements. IAD, interapical distance; IOD, interocclusal distance.|
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The IOD for maxillary premolars and mandibular second premolars was measured between nonfunctional cusp tips. However, IOD for the mandibular first premolars were measured from the functional cusps due to rudimentary lingual cusps of these teeth. The IAD was measured from premolar apex to apex. When two roots were present the buccal root apex was chosen [Figure 3]a, [Figure 3]b.
|Figure 3: (a) Maxillary first premolar IOD and IAD measurements. (b). Mandibular first premolar IOD and IAD measurements. IAD, interapical distance; IOD, interocclusal distance.|
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The IOD was measured from central fossa to central fossa as this measurement is less affected by tipping of these teeth than if the cusp tips were chosen. To measure the IAD in the mandible, the mesial root apices were selected by scanning through sectional slices in the frontal view until the first molars' root apices on either side of arch were visible. For maxillary first molars, the IAD of the palatal root was chosen [Figure 4]a, [Figure 4]b.
|Figure 4: (a) Maxillary first molar IOD and IAD measurements. (b) Mandibular first molar IOD and IAD measurements. IAD, interapical distance; IOD, interocclusal distance.|
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The angulations of the maxillary and mandibular teeth were all measured relative to the interocclusal line (A line drawn through the cusp tips of the right and left canines, mandibular first premolars; or a line drawn through the central fossae of the crowns of the right and left maxillary first premolars, second premolars, and first molars) as described by Cattaneo et al.. Angulations were measured separately on each tooth for both the right and the left sides, but the mean of the right and the left for each tooth was calculated for statistical purposes. The maxillary and mandibular canine angulations were measured at the inner junction between the line connecting the root apex to the cusp tip and the interocclusal line [Figure 5]a, [Figure 5]b.
|Figure 5: (a) Maxillary canines angulations. (b) Mandibular canines angulations.|
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The premolar angulation was measured as the inner angle between a line connecting the root apex to the central fossa and the interocclusal line. In the maxillary premolars, if there were two roots available, the inner angle between the furcations to the central fossae line and the interocclusal line was measured. Functional cusps were chosen for first mandibular premolars [Figure 6]a, [Figure 6]b.
|Figure 6: (a) Maxillary second premolars angulations. (b) Mandibular first premolars angulations.|
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The maxillary first molar angulation was measured as the inner angle formed at the junction between the line connecting the furcation to the central fossa and the interocclusal line [Figure 7]a. The mandibular first molar angulation was measured as the inner angle formed between the line connecting the mesial root apex to the central fossa and the interocclusal line [Figure 7]b.
|Figure 7: (a) Maxillary first molars angulations. (b) Mandibular first molars angulations.|
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Other measurements were performed on the axial view to evaluate the transverse changes of the bone after expansion as termed by Corbridge et al. The bone thickness at the furcation level of first molars regions were measured after coordination of the furcation level in the coronal and axial views as shown in [Figure 8].
|Figure 8: CT image orientation of the buccal furcation level. CT, computed tomography.|
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Four bilateral distances were measured the maxillary and mandibular then the average of each pair of measurements was considered for statistical purposes. [Figure 9] and [Figure 10] show the maxillary measurements; the mandibular measurements were showed in [Figure 11] and [Figure 12]. Buccal bone thickness (BBT): the BBT defined as the shortest distance between the outer buccal alveolar cortical plate and the mesiobuccal root of the maxillary first molar or the mesial root of the mandibular first molar; buccal cortical plate thickness (BCPT): the maxillary and mandibular BCPT defined as the distance between the outer and inner borders of the buccal alveolar cortical plate in the inter dental area mesial to the first molar; palatal or lingual bone thickness (PBT, LBT): the PBT defined as the shortest distance between the lingual root of the maxillary first molar and the outer border of the palatal alveolar cortical plate. The LBT defined as the shortest distance between the distal root of the mandibular first molar and the outer border of the lingual alveolar cortical plate; and alveolar width (ALW): the ALW measured from the outer limits of the buccal cortical plate to the outer limits of the palatal cortical plate in the maxilla and to the outer limits of the lingual cortical plate in the mandible passing through the center of the first molar furcation, approximately perpendicular to each cortical plate.
|Figure 9: Diagram show the buccal cortical plate thickness (BCPT), buccal bone thickness (BBT), alveolar width (ALW), and palatal bone thickness (PBT) measurements.|
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|Figure 10: CT image show the buccal cortical plate thickness (BCPT), buccal bone thickness (BBT), alveolar width (ALW), and palatal bone thickness (PBT) measurements. CT, computed tomography.|
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|Figure 11: Diagram show the buccal cortical plate thickness (BCPT), buccal bone thickness (BBT), alveolar width (ALW), and lingual bone thickness (LBT) measurements.|
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|Figure 12: CT image show the buccal cortical plate thickness (BCPT), buccal bone thickness (BBT), alveolar width (ALW), and lingual bone thickness (LBT) measurements. CT, computed tomography.|
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CT measurements were recorded then the data was tabulated. To assess intraobserver reliability, the measurements were repeated for all the patients after 2 weeks. Dahlberg's formula was used for reporting the error between measured and remeasured data . The coefficient of reliability was found to be on average 0.07° with corresponding P values of 0.641 for CT angular measurements and the mean error of the linear measurements was 0.04 mm (0.711). Data analysis was performed using (SPSS, Chicago, USA), version 21. Statistical analysis of the data with different characteristics was performed with the use of the paired t test. A two-tailed P value of 0.05 was considered statistically significant with a 95% confidence interval while P values of 0.001 was considered highly significant with a 99.9% confidence interval.
| Results|| |
The results of the current study were performed on 15 patients (12 females and three males) seeking orthodontic treatment in Orthodontic Department, Faculty of Dentistry, Tanta University, after exclusion of five patients who decided to finish their treatment early before finishing. All the study cases had class I skeletal and molar relationships with moderate arch length deficiency and an acceptable soft tissue facial profile. The mean maxillary crowding was 7 ± 1.9 mm, and the mean mandibular crowding was 4.2 ± 1.3 mm. The mean age of the patients at the start of the treatment was 17.8 ± 3.7 years. The patients were treated with a nonextraction approach using the Damon system appliance and mechanics. The average treatment time was 20.7 ± 2.2 months with number of appointments range between 11 and 17 visits including emergency appointments [Table 1].
The results presented in [Table 2] showed a nonsignificant change in the canine IOD while the IAD increased significantly by 1.762 mm (P < 0.05). The first premolar, second premolar, and molar IOD showed significant increase by 2.369 mm (P < 0.001), 3.323 mm (P < 0.001), and 1.493 mm (P < 0.05), respectively. Moreover, their respective IADs showed significant increase by 2.546 mm (P < 0.001), 3.341 mm (P < 0.001), and 1.893 mm (P < 0.001). The results showed a nonsignificant change in the mandibular canine IOD whereas the IAD increased significantly by 1.515 mm. The first premolar IOD and IAD increased insignificantly. The second premolar, and first molar IOD showed significant increase by 1.935 and 2.185 mm, respectively, while their respective IADs decreased insignificantly.
|Table 2: Descriptive statistics of changes in maxillary arch width (mm) after treatment|
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The CT analysis in [Table 3] showed a significant increase of the axis angle of the maxillary canine by 6.35°. Whereas, a nonsignificant increase of the maxillary first premolars, second premolars and first molars of their axis angles were occurred. In addition, the results showed a significant increase of the axis angle of the mandibular second premolars and first molars by 5.669 and 8.063°, respectively. While, the mandibular first premolars revealed a nonsignificant increase of their angulations, and the mandibular canine did not change.
|Table 3: Descriptive statistics of changes in maxillary dental angulations (deg.) after treatment|
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[Table 4] illustrated the movement behavior of each tooth in the maxillary and mandibular arches regarding the IOD to the IAD ratio and the angulations of each tooth.
|Table 4: Tooth movement behavior in the maxillary and the mandibular arches after Damon's expansion|
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As illustrated in [Table 5], the CT analysis revealed a significant decrease of the maxillary and mandibular BBT by 1.089 and 0.963 mm, respectively. Whereas, the maxillary LBT and the mandibular LBT increased significantly by 1.272 and 1.016 mm, respectively. However, the maxillary and the mandibular ALW decreased significantly by 0.615 and 0.201 mm, correspondingly. The maxillary and mandibular BCPT did not change.
|Table 5: Descriptive statistics of changes in bone measurements (mm) after treatment|
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| Discussion|| |
The current study is a clinical trial that was done by the same clinician, with strict inclusion criteria of the patients, this could improve the reliability of the outcome. The drop-out rate of this study was five cases out of 20. The sample was limited to class I, malocclusions treated with a nonextraction approach so that expansion would not be compromised by movement of the teeth into the extraction spaces. Another consideration was amounts of initial crowding which ranged from 4 to 9 mm because the correction of a small amount of crowding will have little effect on dental arch form. The patients' exhibited age ranged between 13 and 23 years. It was agreed, based on previous studies ,,, that the rate of dimensional changes in arch form rapidly declines after the eruption of permanent dentition. It is therefore reasonable to assume that arch form changes occurring in the present study were primarily appliance related and the effect of growth was negligible.
Over the past few years, most investigations have been studied dental and skeletal changes with the use of dental models and 2D lateral cephalometric radiographs. Indeed, to fully assess the dentoskeletal changes occurring during treatment, 3Ddata sets are needed. These can be obtained from medical CT or cone-beam CT . Therefore, the present study used a 3D MSCT scans in addition to study models and 2D lateral cephalometric radiographs. The results of the CT analysis in the current study revealed that, the canine arch width insignificantly increased in both maxilla and mandible. The maxillary inter- first premolar width showed significant increase while, the mandibular showed nonsignificant increase. The maxillary and mandibular inter-second premolar and intermolar widths showed a significant increase.
In the current study, most of the transverse expansion was observed at the level of the premolars which could highlight how the Damon appliance achieves its crowding relief. This finding was in accordance with Mikulencak who found a clinically and statistically significant change in arch width dimension in the molar and premolar areas after treatment. A significant change was not seen in the canine area.
Another study by Cattaneo et al. reported greater amounts of first premolar expansion with mean values of 4.3 mm, slightly less levels of intermolar (0.9 mm) and intersecond premolar expansion (0.7 mm). Expansion was most pronounced in the premolar region.
Several studies found a statistically significant expansion in all measurements in both arches with the most of the expansion occurred at the premolars. Those were in partial agreement with the current study ,,,,.
The increases in transverse dimensions and the larger amount of expansion reported at the second premolar and first molar could be explained by the use of the Damon CuNiTi broad archwires shape, which are wider than conventional archwires particularly in the buccal segments distal to the first premolar. This could make some doubts about the concept of physiological determined tooth position and 'development of the arch' determined by the body and not by the clinician or the system applied alleged by Damon .
So that, in the present study, the amount of expansion seemed to be correlated with the use of broad-shaped archwires and should not be assigned to the bracket type per se which was supported by the findings of another studies,,,,,,, Ong et al., Cattaneo et al., Pandis et al., Vajaria et al., Weaver et al., and Fleming et al..
However, according to this logic, it would be expected that the amount of mandibular expansion would be as the maxillary after treatment especially that the same archwires were used in both maxilla and mandible, but this was not observed, possibly because of the bone biology of the mandible. Sandström et al. suggested that buccal expansion in the mandibular arch is highly unpredictable and can be influenced by various factors, including anatomy of the underlying structures, inclination of the molars, and architecture of the oral musculature.
In order to differentiate the increases in arch width due to bodily versus tipping movements, the ratios between the interocclusal and the interapical displacement of teeth during arch expansion had been evaluated. Since the increase of the IAD of the maxillary first premolar, second premolar, and first molar was nearly the same or slightly larger than their respective interocclusal measurements, so the arch width increase in the maxilla occurred mainly with a translation movement except the canine. They was tipped as the crown to root movement ratio was 1: 15.
To better understand teeth movement behavior during arch expansion, the relation of the crown to root movement's ratios with the angular changes was performed. Accordingly, the afore-mentioned ratios findings and the increase in the axis angles of all the maxillary teeth signified a buccal root torque and induced a final palatally uprighted teeth.
Conversely, in the mandible, the observed differences between the interocclusal and the interapical displacement indicated that all the mandibular teeth moved by tipping. The canines IADs increased more than the interocclusal with increase in their angulations, which indicate a buccal root torque and a lingual uprightening. The first premolars IODs increased more than their corresponding IADs with decrease in their angulation indicating a buccal tipping of their crowns. The second premolars and first molars IADs decreased while the interocclusal increased, with decrease in their angulations, which indicate a lingual root torque and a final buccally uprighted position.
The results of the CT analysis revealed that, the molar expansion using the Damon system produced a small amount of molar palatal uprightening in the maxilla and a more significant degree of buccal uprightening in the mandible. This was in accordance with the previous results observed in both Mikulencak study which showed that, the maxillary arch expansion using the Damon system produced a 0.5° palatal uprightening of the maxillary molars during treatment, and Ehsani who reported that the significant buccal movement of the roots has different clinical implications for upper molars and lower canines. With upper molars, it suggests a bodily movement as opposed to a tipping movement, whereas with lower canines it can help with retention and stability of treatment results in the long term.
In the current study, the CT analysis revealed that, BBT in the molar area decreased significantly after the treatment with Damon appliance. The mean decrease in the BBT was nearly similar to the mean increase in the PBT and LBT. Which might be attributed to the relative increased buccal expansion.
Even though LBT and BBT showed equal and opposite changes, ALW decreased slightly which can be explained by molars uprightening. This was supported by the study of Marshall et al. who found that, in transverse molar movements during growth, some of the normal decrease in ALW could be explained by erupting maxillary molars with buccal crown torque and then uprighting with age.
The posttreatment BBT in the present study was in accordance with the studies by Paventy who found a significant reduction in buccal bone width and height after expansion with the Damon archwire, and Cattaneo et al. who evaluated only the buccal bone in the second premolars region and found the buccal bone area decreased on both sides in more than half the patients in both groups. In the Damon group, on average, the buccal bone decreased 23 and 18% on the right and left side, respectively. Nevertheless, as in patients treated with rapid maxillary expansion, bone apposition was detected some months after treatment completion . It might be interesting to follow-up the patients at a suitable period after termination of treatment.
| Conclusion|| |
The conclusion of the current study can be summarized as follows:
- The overall transverse expansion revealed that in the maxilla, there was a significant increase in all distances which was mostly evident at the level of the premolars followed by the molars with the exception of the interocclusal width of the canine.
- The expansion produced a small amount of uprightening in the maxillary molars and a more significant degree in the mandibular molars.
- The interpretation of the interocclusal/interapical ratio with the angulation changes revealed that, the expansion in the maxilla was done mainly by bodily movement with the exception of the canines which moved by tipping. The canines, premolars and first molars were palatally uprighted with buccal root torque. In the mandible, the expansion was reached by tipping movement. The canines were uprighted lingually with buccal root torque. The first premolars were tipped bucally with lingual root torque. And the second premolars and first molars were bucally uprighted with lingual root torque.
- The mean decrease in the BBT was nearly similar to the mean increase of the palatal or lingual thickness.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]