Material and methods

This study was approved by the ethical committee of the Pontifical Catholic University of Rio Grande do Sul in Brazil. Informed consent was obtained from the parents of all patients who agreed to participate in this study. The sample was selected by examining subjects in need of orthodontic treatment at the Department of Orthodontics of the School of Dentistry. The inclusion criteria for this study were transverse maxillary deficiency, mixed dentition or early permanent dentition, and no surgical or other treatment that might affect the RME effects during the expansion period. Patients with congenital malformations or periodontal diseases, or above 15 years of age were excluded from the study sample.

In this prospective study, the sample comprised 33 healthy white children (11 boys, 22 girls) with a mean chronologic age of 10.7 years (range, 7.2-14.5 years) and a mean skeletal age of 10.9 years (range, 6.8-15 years). These patients were randomly divided into 2 groups: Haas (n = 18) and hyrax (n = 15). In the Haas group, the Haas-type expander, with 4 bands (first permanent molars and first premolars or first deciduous molars) and buccal and lingual stainless steel bars of 1.0-mm diameter was used ( Fig 1 , A ). In the hyrax group, the hyrax-type expander, with 4 bands, buccal and lingual stainless steel bars of 1.0-mm diameter and a jackscrew with 1.4-mm stainless steel extensions soldered to the lingual surfaces of each pair of bands, was used ( Fig 1 , B ).

A, Haas-type expander and B, hyrax-type expander at the end of the active phase of RME.

Both appliances had expansion jackscrews with activations of a quarter turn equivalent to a 0.2-mm expansion. All patients in the Haas and hyrax groups had RME, with initial activations of 4 quarter turns (0.8 mm) followed by 2 quarter turns per day (0.4 mm) until the expansion screw reached 8 mm.

The i-CAT (Imaging Sciences International, Hatfield, Pa) was used to obtain CBCT images before RME (T1) and at the end of the active expansion phase (T2). The CBCT scans were performed at 120 kV, 8 mA, scan time of 40 seconds, and 0.3-mm voxel dimension. The data for each patient were reconstructed with 0.3-mm slice thickness, and the digital imaging and communications in medicine (DICOM) images were assessed by using the EFILM workstation software program (version 2.1.2, Merge Healthcare, Milwaukee, Wis). All linear and angular measurements were made by a blinded examiner (M.M.), who had no access to the data or the clinical consultations of the patients in this sample.

For transverse maxillary posterior region evaluation, the DICOM files with CBCT images at T1 and T2 were imported into EFILM and visualized as axial images arranged side by side. To obtain standardized axial and coronal slices and thus allow the comparisons between T1 and T2, the following references were used. In the axial slices, the images that displayed the root canal in the most apical region of the palatal root of maxillary first permanent molars were selected. By using the MultiPlanar Reformation tool, the MultiPlanar Reformation line was positioned at the root canal in the most apical region of the palatal root of the maxillary first permanent molars on the right and left sides. From these references, standardized coronal images were produced, and the measurements were made ( Fig 2 ). The landmarks used for evaluation of the maxillary posterior region are shown in Figure 3 and described in Table I .

Transverse maxillary posterior region evaluation: A and B, preexpansion; C and D, at the end of the active phase of expansion.

Landmarks used in the evaluation of the maxillary posterior region.

The analyses of the transversal changes in the maxillary anterior region were performed in a similar way to those of the posterior region. In the axial slices, images at T1 and T2 were selected with the root canals in the most apical region of the roots of the maxillary permanent canines visualized. After that, the MultiPlanar Reformation line was positioned at the root canal in the most apical region of the maxillary permanent canine root on the right and left sides. From theses references, standardized coronal images were produced, and the measurements were made ( Fig 4 ). The landmarks used to evaluate the RME effects in the anterior region of maxilla are shown in Figure 5 and described in Table I .

Transverse maxillary anterior region evaluation: A and B, preexpansion; C and D, at the end of the active phase of expansion.

Landmarks used in the evaluation of the maxillary anterior region.

Results

The overall immediate effects of RME on the transverse plane are shown in Table III . There were significant increases in maxillary width at the skeletal, alveolar, and dental levels for both the Haas ( Table IV ) and the hyrax ( Table V ) groups in all parameters ( P <0.05). There was less expansion at the skeletal than at the dental level, just as the increase in the maxillary apical base was smaller in the posterior region (distances 5-6 and 11-12) compared with the anterior (distances 15-16, 21-22) ( Tables III-V ). The hyrax group had greater statistically significant increases in the maxillary transverse dimensions at the skeletal level than did the Haas group in both posterior (distances 5-6 and 11-12) and anterior (distance 21-22) regions ( Table VI ). There was no significant difference between the groups for the buccal inclination of the maxillary first permanent molars, except for the linear measure (distance 9-10), which indicated greater inclination of these teeth in the Haas group than in the hyrax group ( Table VI ).

Table IV

Immediate changes in the maxillary transverse plane with RME in the Haas group

Variable	T1		T2		Change		P
	Mean (mm)	SE (mm)	Mean (mm)	SE (mm)	Mean (mm)	SE (mm)
Skeletal
Distance 5-6
Posterior apical base width	61.10	0.87	63.29	0.87	2.19	0.15	<0.0001 ∗
Distance 11-12
Posterior midpalatal suture width	00.00	0.11	02.61	0.11	2.62	0.12	<0.0001 ∗
Distance 15-16
Anterior apical base width (inferior)	38.98	0.82	42.28	0.82	3.29	0.30	<0.0001 ∗
Distance 17-18
Anterior apical base width (superior)	39.70	1.12	42.33	1.12	2.62	0.31	<0.0001 ∗
Distance 21-22
Anterior midpalatal suture width	00.00	0.15	03.63	0.15	3.63	0.17	<0.0001 ∗
Alveolar
Distance 3-4
Posterior width at alveolar crest level	51.96	0.69	57.41	0.69	5.44	0.25	<0.0001 ∗
Distance 19-20
Anterior width at midalveolar level	40.56	0.79	44.59	0.79	4.03	0.30	<0.0001 ∗
Dental
Distance 7-8
Intermolar width at occlusal surface	43.42	0.59	51.12	0.59	7.70	0.20	<0.0001 ∗
Distance 9-10
Intermolar width at palatal root apices	30.57	0.71	32.72	0.71	2.15	0.18	<0.0001 ∗

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. A note about sample size
2. Residents’ journal review
3. Attitudes, awareness, and barriers toward evidence-based practice in orthodontics
4. Evaluation of the genotoxic effects of fixed a ppliances on oral mucosal cells and the relationship to nickel and chromium concentrations: An in-vivo study
5. Photoelastic analysis of forces generated by T-loop springs made with stainless steel or titanium-molybdenum alloy
6. Accuracy in tooth positioning with a fully customized lingual orthodontic appliance

Stay updated, free dental videos. Join our Telegram channel

Join