Clear Orthodontic Expander Versus Hyrax (COE-Hyarx)

Evaluating the Clinical Performance of a Novel Clear Orthodontic Expander Versus Hyrax: A Randomized Clinical Trial

This study will be conducted to evaluate the effectiveness of a clear expander fabricated from 2-mm biocompatible polyethylene terephthalate glycol (PETG) thermoforming material integrated with an expansion screw in achieving dental and skeletal expansion in adolescent patients, compared with the conventional Hyrax expander.

Study Overview

• Status: Recruiting
• Conditions: Malocclusion; Narrow Maxilla
• Intervention / Treatment: Device: New clear expander; Device: Hyrax expander

Detailed Description

This will be a multicenter randomize clinical trial with two-arm parallel groups, and will be conducted at the Department of Orthodontics, College of Dentistry, University of Baghdad, as well as different specialized dental centers affiliated with the Iraqi Ministry of Health, and some private clinics.

The sample size will be calculated based on previous studies with similar aim to measure the skeletal expansion. A minimum sample size of 17 patients was required, and in order to account for a 15% dropout, a total of 20 patients will be recruited for each group (new clear expander and hyrax expander). The amount of 2.5 mm or greater of maxillary sutural opening will be considered clinically effective.

Two randomizations will be employed, one for the expander type and the other for the cleaning method of the new expander, a computer random generator will be used to develop a simple randomization with an equal allocation ratio (1:1) and without stratification.

Data Collection and Measurements will be include, CBCT evaluation, Intraoral scan of the maxillary arch evaluation, overjet and overbite, CBCT-derived cephalometric images will be used to measure the maxillary mandibular plane angle, Microbial evaluation after using two different methods for cleaning the new clear expander and at the end of the treatment, the patient will be asked to fill out a questionnaire about the treatment, giving information about their experience and satisfaction during treatment.

Data will be analyzed using the Statistical Package for Social Sciences for Windows, version 26.0, including Descriptive Statistics 9numbers, frequencies, percentages, mean, median, and standard deviations), Reliability Statistics (an intraclass correlation coefficient), and Inferential Statistics (Levene's test, Shapiro Wilk test, Paired samples t-test and Independent samples t-test).

• Study Type: Interventional
• Enrollment (Estimated): 40
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Noor FK Al-Khawaja, BDS, MSc; Phone Number: +9647712222834; Email: noor.alkhawaja@codental.uobaghdad.edu.iq

Study Locations

• Iraq
  • Al-Rusafa, Bab Al-moadham
    • Baghdad, Al-Rusafa, Bab Al-moadham, Iraq
      • Recruiting
      • University of Baghdad/Collage of Dentistry
      • Contact: Noor FK Al-Khawaja, BDS, MSc; Phone Number: +9647712222834; Email: noor.alkhawaja@codental.uobaghdad.edu.iq

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Patients' age at the start of treatment will range from 10-14 years.
2. Unstable unilateral or bilateral posterior crossbite due to maxillary constriction.
3. The first molars are fully erupted.
4. Good oral health free from caries and periodontal problems at the start of treatment.
5. Good general health.

Exclusion Criteria:

1. Patients with obvious facial asymmetry.
2. Patients with orofacial cleft.
3. Patients with previous orthodontic treatment.
4. Patients with bad oral habits.
5. Patients with active periodontal disease.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: New clear expander; After obtaining the 3D-printed maxillary dental cast, a 2 mm PETG (rigid) thermoforming material (Leone® S.p.A., Florence, Italy) will be adapted separately to the maxillary cast using a pressure molding vacuum machine. The clear appliance will then be trimmed and finished. Depending on the degree of maxillary constriction, a Leone® Standard or universal expansion screw (Leone® S.p.A.,Florence, Italy) measuring 6-9 mm will be incorporated into the appliance and positioned in the midline of the maxillary cast after splitting the appliance midpalatally embedded in acrylic composed from Methyl methacrylate monomer and Methyl methacrylate polymer Orthocryl® liquid (monomer), and Orthocryl® EQ-powder (polymer) (Dentaurum GmbH & Co. KG, Ispringen, Germany)	Device: New clear expander; All patients with a clear expander will be instructed to wear the appliance 24 hours a day, except during eating and cleaning. The expander will be activated twice daily (0.2 mm per turn). Patients will be provided with an instruction brochure and advised to use a reminder to ensure compliance. The expansion will continue until the desired amount of the maxillary arch expansion occurs when the maxillary first molars' palatal cusps occlude the lingual side of the mandibular first molar buccal cusps to overcome the expected relapse due to the elasticity of the palatal soft tissue.
Experimental: Hyrax expander; After obtaining the 3D-printed maxillary dental cast, patients will be treated with a Hyrax expander using a rapid expander from Leone® S.p.A., Florence, Italy, cemented in the upper first premolars and first molars. If the first premolars had not yet erupted, the Hyrax expander will be cemented in the upper first permanent molars only.	Device: Hyrax expander; The activation protocol for the Hyrax expander will be the same in all patients, twice daily (0.2 mm per turn). The expansion will continue until the desired amount of the maxillary arch expansion occurs when the maxillary first molars' palatal cusps occlude the lingual side of the mandibular first molar buccal cusps to overcome the expected relapse due to the elasticity of the palatal soft tissue.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
CBCT evaluation	Skeletal and dentoalveolar measurements will be assessed using cone-beam computed tomography (CBCT). Skeletal measurements will include nasal width, midpalatal suture gap, and palatal height, measured in millimeters (mm). Dentoalveolar measurements will include vertical dental heights and maxillary width measured in millimeters (mm), as well as dental inclination measured in degrees (°). All measurements will be obtained from CBCT images using dedicated three-dimensional imaging analysis software.	pre-treatment (T0) and immediately post-treatment (T1) around one to two months

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Intraoral scan of the maxillary arch evaluation	Maxillary transverse dental measurements will be assessed using a digital intraoral scan. The parameters evaluated will include intercanine width, interpremolar width, intermolar width, and intermolar transpalatal width, all measured in millimeters (mm) using three-dimensional digital dental model analysis software.	pre-treatment (T0) and post-treatment (T1) around one to two months
Clinical evaluation	Overjet and overbite will be evaluated clinically using a calibrated orthodontic ruler, with measurements recorded in millimeters (mm).	pre-treatment (T0) and immediately post-treatment (T1) around one to two months
Cephalometric analysis	CBCT-derived cephalometric images will be used to measure the maxillary mandibular plane angle in degrees (°) to evaluate the vertical relationship using cephalometric analysis software.	pre-treatment (T0) and immediately post-treatment (T1) around one to two months
Microbial evaluation	Patients will be allocated into two groups according to the cleaning method: brushing with a toothbrush and aligner foam (China) or using Efferdent cleaning tablets (USA). Biofilm samples will be collected using sterile swabs with Amies transport medium (Boen Healthcare Co., Ltd., China). The outcome measure will be bacterial biofilm accumulation, assessed by bacteriological analysis based on bacterial colony counting, expressed as colony-forming units per milliliter (CFU/ml).	after one month.
Patient satisfaction with the appliance	At the end of treatment, patient-reported experience and satisfaction will be assessed using a structured questionnaire. Responses will be recorded as questionnaire scores using a 3-point Likert-type scale.	around one to two months

Collaborators and Investigators

• Sponsor: University of Baghdad
• Investigators: Study Chair: Yassir A Yassir, Ph.D. (UK), University of Baghdad

Study record dates

Study Major Dates

• Study Start (Actual): February 1, 2026
• Primary Completion (Estimated): November 1, 2026
• Study Completion (Estimated): February 1, 2027

Study Registration Dates

• First Submitted: January 12, 2026
• First Submitted That Met QC Criteria: January 21, 2026
• First Posted (Actual): January 23, 2026

Study Record Updates

• Last Update Posted (Actual): April 22, 2026
• Last Update Submitted That Met QC Criteria: April 17, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: adolescent; clinical trial; thermoplastic material; clear expander; hyrax
• Additional Relevant MeSH Terms: Stomatognathic Diseases; Tooth Diseases; Malocclusion
• Other Study ID Numbers: 1158425; 1158 (Other Identifier: College of Dentistry / University of Baghdad)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No