Trial design and any changes after trial commencement

This project was a single-center RCT with 2 parallel arms and a 1:1 allocation ratio. This RCT followed the Consolidated Standards of Reporting Trials statement and guidelines, and did not require changes in methods after trial commencement.

Participants, eligibility criteria, and settings

This study was approved by the Ethics in Research Committee of Bauru Dental School, University of São Paulo, Bauru, Brazil (protocol no. 68551617.8.0000.5417/2.112.035). In addition, the protocol of this study was registered at Clinicaltrials.gov with the identifier NCT03702881 .

Patients were recruited at the Orthodontic Clinic of Bauru Dental School, University of São Paulo, Bauru, Brazil, from June 2017 to April 2018. The selection criteria included patients aged between 7 and 11 years, anterior open bite >1 mm (clinically evaluated as the vertical distance between the incisal edges of the maxillary and mandibular central incisors), erupted permanent first permanent molars, with the maxillary and mandibular permanent central incisors fully erupted, without or with only mild crowding, and without the need of maxillary expansion. To differentiate between incomplete eruption and open bite for the younger patients, we considered the vertical relationship between lateral and central incisors. If the maxillary lateral incisors were closer to the occlusal plane than the maxillary central incisors and these central incisors still showed a negative overbite greater than 1 mm, the condition was classified as an open bite. This method was adopted on the basis of previous studies. ^{, ,} Children with previous orthodontic treatment, craniofacial anomalies or syndromes, tooth agenesis, loss of permanent teeth, severe crowding, maxillary constriction, or posterior crossbite were excluded.

Informed consent was obtained from the patients and their parents or legal guardians before recruitment.

Interventions

Bonded spurs (Morelli Ortodontia, Sorocaba, São Paulo, Brazil) were installed at the cervical and incisal regions of the palatal and lingual surfaces of the maxillary and mandibular incisors, respectively. These regions were selected to prevent possible occlusal interferences during treatment. ^, The spurs were bonded using the Transbond XT light cure orthodontic adhesive (3M Unitek, Monrovia, Calif). The spurs were sharpened with a carborundum disk before bonding.

The experimental group comprised patients treated with bonded spurs combined with posterior build-ups. Posterior build-ups consisted of 2-3 mm resin blocks of light-cured orthodontic cement (Ortho Bite; FGM, Joinville, Santa Catarina, Brazil) bonded on the palatal cusps of all maxillary posterior teeth to maintain the natural occlusal force balance ( Fig 1 , A ). The maxillary molars were chosen on the basis of a previous study, and because of the facility for relative isolation. Posterior build-ups wore down in a few patients (4 of 25) and were rebuilt only once during treatment. The comparison group comprised patients treated with only bonded spurs ( Fig 1 , B ). The treatment follow-up was 12 months, as previously reported for similar studies. ^{, ,} Posterior build-ups were removed in the experimental group before obtaining the second digital lateral headfilms (which were taken on the same day). Bonded spurs were maintained as active retention in both groups.

A, Protocol including bonded spurs combined with posterior build-ups. B, Protocol including conventional bonded spurs.

Digital lateral headfilms were obtained using Orthophos XG 3D (Dentsply Sirona, Bensheim, Germany) at pretreatment and after 12 months of treatment for all patients.

Outcomes (primary and secondary) and any changes after trial commencement

The change in the overbite was considered as the primary outcome measurement.

Secondary outcome measurements included the changes in the gonial angle, mandibular plane angle, lower anterior face height, inclination/position/height of the maxillary and mandibular incisors, and maxillary and mandibular molar extrusion.

All measurements ( Table I ) were performed using Dolphin Imaging software (version 11.5; Dolphin Imaging and Management Solutions, Chatsworth, Calif).

The anterior open bite was considered corrected when the overbite was equal or greater than 0 (0 meaning an end-to-end vertical incisor relationship), cephalometrically confirmed as the distance in millimeters between the incisal edges of the maxillary and mandibular central incisors, perpendicular to the occlusal plane. ^, There were no outcome changes after trial commencement.

Sample size calculation

The sample size was calculated to provide 80% of test power at a significance level of 0.05 to detect an intergroup difference of 1.5 mm in the overbite with a previously reported standard deviation of 1.69 mm. The minimal sample size required per group was 21 patients.

Interim analyses and stopping guidelines

Not applicable.

Randomization (random number generation, allocation concealment, implementation)

The randomization scheme was obtained by using the Web site Randomization.com ( http://www.randomization.com ). This software generated the randomization list using random block sizes, ensuring equal distribution in both groups. Fifty patients were randomized before trial commencement.

Allocation concealment was achieved with sequentially numbered opaque and sealed envelopes containing the treatment allocation cards. Opacity was implemented by inserting the card with the assignment into the foil. The envelopes were prepared before the trial commencement. The patient’s name and baseline information were written on the envelope before opening it. All envelopes were torn open instead of being unsealed. The envelopes were securely stored in a different location from the trial site.

The generation of randomization lists, allocation concealment, and implementation (enrollment of participants/treatment assignment/deliver intervention) were performed independently by different persons.

Blinding

Blinding of either patient or operator was not possible because both knew the type of appliance installed. However, the assessment of the lateral radiographs was blinded. All radiographs were unidentified before the assessor’s evaluation, and all those taken at T2 showed the presence of bonded spurs and the absence of posterior build-ups.

Statistical analyses (primary and secondary outcomes, subgroup analyses)

Lateral headfilms of 30% of the sample were randomly selected and retraced by the same examiner after a 30-day interval. Intraobserver reliability was assessed with the intraclass correlation coefficient.

Normal distribution was tested using the Shapiro-Wilk test. Sex distribution was compared with the Fisher exact test. Intergroup comparisons regarding age and cephalometric variables were performed with t or Mann-Whitney U tests, depending on normality. The influence of pretreatment predictor variables (Ar.Go.Me, SN.GoGn, LAFH, and the initial amount of anterior open bite) on the overbite change was evaluated with multiple linear regression analysis considering all patients. Statistical analyses were performed using SPSS software (version 25; IBM, Armonk, NY). Results were considered significant at P <0.05.

Participant flow

A total of 1025 children were assessed for eligibility; 969 were excluded because they did not meet the inclusion criteria, and 6 declined to participate. Fifty patients were randomized in a 1:1 ratio ( Fig 2 ).

Consolidated Standards of Reporting Trials flow diagram.

Baseline data

The groups showed similar characteristics regarding age and sex distribution and initial cephalometric variables ( Tables II and III ; Fig 3 , A ).

Table III

Pretreatment (T1) and posttreatment (T2) measurements

Variable	Experimental group (n = 24)						Comparison group (n = 25)
	T1			T2			T1			T2
	Mean	SD	Median	Mean	SD	Median	Mean	SD	Median	Mean	SD	Median
Vertical component
Ar.Go.Me, °	129.95	6.01	129.05	129.29	6.29	127.50	131.48	5.20	131.90	130.80	5.15	130.70
SN.GoGn, °	34.47	5.29	33.90	34.30	4.91	33.70	34.42	4.34	34.10	34.10	5.02	34.20
LAFH, mm	56.11	3.42	55.60	56.66	3.59	56.70	56.92	4.33	56.80	57.66	4.52	56.70
Dental relationship
Overbite, mm	−4.45	1.49	−4.05	0.39	1.42	0.35	−4.36	1.65	−4.30	0.48	1.57	1.00
Maxillary dentoalveolar component
Mx1.NA, °	27.85	5.08	25.65	22.36	4.11	22.70	29.28	5.24	30.70	23.85	5.37	25.20
Mx1-NA, mm	4.54	1.81	4.25	4.30	1.54	4.10	5.46	2.12	5.50	5.10	2.38	5.20
Mx1-PP, mm	21.18	2.57	21.70	23.92	2.22	24.40	21.74	2.85	21.80	24.66	2.53	24.50
Mx6-PP, mm	16.96	1.64	17.05	17.08	1.70	17.40	17.10	2.65	16.70	17.92	2.73	17.70
Mandibular dentoalveolar component
Md1.NB, °	27.84	4.32	27.15	24.78	4.08	24.70	29.60	5.84	30.60	26.48	6.70	27.50
Md1-NB, mm	4.82	1.36	4.75	4.94	1.47	4.60	5.56	1.84	5.60	5.62	1.83	5.70
Md1-GoMe, mm	31.56	2.20	31.15	33.96	2.32	34.00	32.31	2.54	31.90	34.56	2.32	34.50
Md6-GoMe, mm	24.37	2.12	24.25	24.88	2.37	25.00	24.50	1.99	24.20	24.86	2.11	25.00

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