Dental arch changes after open bite treatment with spurs associated with posterior build-ups in the mixed dentition: A randomized clinical trial


This single-center, 2-arm, parallel-group randomized clinical trial aimed to compare the dimensional dental arch changes after anterior open bite (AOB) treatment with bonded spurs associated with posterior build-ups vs bonded spurs alone.


Patients aged between 7 and 11 years with AOB were recruited at a university clinic and randomly allocated into 2 groups. The experimental group was treated with bonded spurs associated with posterior build-ups (SBU) and the comparison group with bonded spurs alone (S). Digital dental models were obtained at pretreatment and after 12 months of treatment. The overbite change was the primary outcome. The randomization list was obtained at the Web site . Allocation concealment involved sequentially numbered, sealed, and opaque envelopes. The outcomes’ assessment was blinded. Analysis of covariance was used for intergroup comparisons ( P <0.05). Mean difference (MD) and 95% confidence interval (CI) were obtained.


Twenty-four patients (mean age, 8.22 ± 1.06 years; 7 males and 17 females) were included in the SBU group, and 25 patients (mean age, 8.30 ± 0.99 years; 11 males and 14 females) were included in the comparison group. After a 12-month follow-up, the overbite increased approximately 4 mm in both groups (MD, −0.11 mm; 95% CI, −1.03 to 0.80). Means of anterior dentoalveolar vertical development ranged from 2.24 mm (S group) to 2.49 mm (SBU group) and from 1.31 mm (SBU group) to 1.55 mm (S group) for the maxilla (MD, −0.24 mm; 95% CI, −0.91 to 0.44) and mandible (MD, 0.29 mm; 95% CI, −0.39 to 0.96), respectively. The maxillary intermolar distance decreased in the SBU group and increased in the S group (MD, −0.48 mm; 95% CI, −0.92 to −0.03). The mandibular intermolar distance increased in the SBU group and decreased in the comparison group (MD, 0.26 mm; 95% CI, 0.004-0.52). Plaque accumulation around the spurs was observed in some patients.


Both protocols demonstrated similar improvements in the AOB with similar effects on the dental arches. The SBU group showed a slight decrease in the maxillary intermolar distance and a slight increase in the mandibular intermolar distance, whereas opposite changes were observed for the S group.


This trial was registered at (Identifier NCT03702881 ).


The study protocol was not published.


This work was supported by the São Paulo Research Foundation (FAPESP) grants nos. 2017/06440-3, 2018/05238-9, and 2018/24003-2; and financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil (CAPES), Finance Code 001.


  • The anterior open bite was treated with bonded spurs, with or without posterior build-ups.

  • The therapies produced similar improvements in anterior open bite.

  • Dentoalveolar and dental arch dimensional changes were similar.

  • Group with build-ups had a slight decrease in maxillary intermolar distance.

  • This group also had a slight increase in the mandibular intermolar distance.

  • The opposite was found in the group treated with bonded spurs alone.

Anterior open bite (AOB) malocclusion has a multifactorial etiology, , and can be caused by environmental factors, including deleterious habits and mouth breathing. Thumb sucking, pacifier, and tongue thrust are the most common deleterious habits. , AOB malocclusion treatment in the mixed dentition aims to interrupt the deleterious habits and allow extrusion of the anterior teeth. Bonded spurs are efficient in mixed dentition, acting as a reminder to stop deleterious habits. Their effects are similar to those produced by the palatal crib.

Some protocols integrate therapies that interrupt the habits and control the vertical dimension because AOB is usually associated with a vertical growth pattern. Vertical chincup has been reported as an associated therapy to bonded spurs that produce AOB correction with a significant decrease in the gonial angle. Nevertheless, patient compliance is necessary. One alternative during AOB treatment in adults is posterior build-ups associated with fixed orthodontic appliances. Intrusion of maxillary molars and a significant counterclockwise rotation of the mandible were reported using this protocol. Thus, the association of bonded spurs and posterior build-ups in the mixed dentition might be an alternative for AOB treatment.

Over the years, the studies have mainly focused on the evaluation of the cephalometric changes in AOB early treatment. In addition, some systematic reviews reported the lack of randomized clinical trials (RCTs) on this topic. , Although cephalometric evaluations bring a perspective of the skeletal and dentoalveolar changes, the dental arch dimensional changes cannot be demonstrated using radiographs. Only 1 RCT reported dental arch changes after AOB early treatment comparing fixed and removable palatal cribs. However, no evaluation of the dental arch changes after AOB early treatment with bonded spurs neither alone nor associated with other therapy as posterior build-ups have been reported. Therefore, the present study was planned to help to fill this void.

Specific objectives or hypotheses

This RCT aimed to compare the dimensional changes on maxillary and mandibular dental arches after AOB treatment with bonded spurs associated with posterior build-ups (SBU) and bonded spurs alone (S). The null hypothesis tested was that both therapies have similar dental arch outcomes.


Trial design and any changes after trial commencement

This study was conducted as a 2-arm parallel, single-center RCT with a 1:1 allocation ratio, following the Consolidated Standards of Reporting Trials guidelines. An untreated control group was not included because of ethical reasons.

Participants, eligibility criteria, and settings

The Ethics in Research Committee of Bauru Dental School, University of São Paulo, Bauru, Brazil approved the study (protocol no. 68551617.8.0000.5417/2.112.035). The protocol was registered at with the identifier NCT03702881 . Subjects’ recruitment was performed at Bauru Dental School, University of São Paulo, Bauru, Brazil, from June 2017 to April 2018. Inclusion criteria were patients aged between 7 and 11 years, AOB >1 mm (clinically evaluated as the vertical distance between the incisal edges of the maxillary and mandibular central incisors), presence of fully erupted permanent maxillary and mandibular first molars and central incisors, and the absence or mild incisor crowding. The vertical relationship between lateral and central incisors was considered to differentiate incomplete eruption from the open bite in children in the first transitional period of the mixed dentition. If the maxillary lateral incisors were closer to the occlusal plane than the maxillary central incisors and the central incisors still showed a negative overbite (>1 mm), the condition was classified as open bite and the subject was considered eligible for treatment, as suggested in previous studies. , , All included patients presented a history of at least 1 deleterious habit. Exclusion criteria included previous orthodontic treatment, presence of craniofacial anomalies or syndromes, and tooth agenesis. For this specific study, patients with AOB with maxillary constriction and posterior crossbite (clinically evaluated) were also excluded, as in previous studies, , , , because the treatment protocols used in this trial did not aim to correct these conditions.

Informed consent was signed by all patients and their parents or legal guardians before recruitment.


The spurs (Morelli Ortodontia, Sorocaba, São Paulo, Brazil) were bonded at the cervical region of the palatal surfaces of the maxillary incisors and the incisal region of the lingual surfaces of the mandibular incisors in all patients using Transbond XT light cure orthodontic adhesive (3M Unitek, Monrovia, CA). , A carborundum disk was used to sharpen the spurs before bonding.

Posterior build-ups, 2-3 mm resin blocks of light-cured orthodontic cement (Ortho Bite; FGM Dental Products, Joinville, Santa Catarina, Brazil), were bonded on the functional cusps of the maxillary posterior teeth, as previously suggested, only in the SBU group ( Fig 1 , A ). The S group included patients treated with bonded spurs alone ( Fig 1 , B ). New spurs and build-ups were rebonded as soon as possible in patients who were debonded or when build-ups were worn down. The treatment follow-up was 12 months, as reported in previous studies. , , After this period, the posterior build-ups were removed in the SBU group and then, intraoral scanning was performed on the same day. Spurs were maintained as active retention in both groups.

Fig 1
A, Bonded spurs associated with posterior build-ups. B, Bonded spurs alone.

Digital dental models acquired from intraoral scanning (TRIOS3; 3Shape, Copenhagen, Denmark) were obtained at pretreatment (T1) and after 12 months of treatment (T2).

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

The primary outcome was the change in the overbite. The changes in the anterior dentoalveolar vertical development, crown heights of incisors and permanent first molars, and arch dimensions (arch perimeter, arch length, intermolar distance) were considered secondary outcomes. The evaluations were performed using the OrthoAnalyzer 3D software (3Shape, Copenhagen, Denmark). All measured variables and their references are defined in Table I , Figure 2 , and the Supplementary Figure . , , The maxillary and mandibular occlusal planes ( Table I ; Supplementary Fig ) were used as references for the dentoalveolar vertical development measurement, as reported in previous studies. , AOB was considered corrected if the overbite was 0 (end-to-end vertical incisor relationship) or had a positive value. ,

Fig 2
Overbite measurement.

Table I
Digital dental model variables
Digital model variables Definition
Dental relationship, mm
Overbite The vertical distance between the mesiodistal midpoints of the incisal edges of the most erupted maxillary and mandibular central incisors ( Fig 2 ). ,
Vertical development, mm
Mx and Md anterior dentoalveolar vertical development The vertical and perpendicular distance from the alveolar process at the level between central incisors contact or a middle point between them (in the presence of spaces) to the occlusal plane, in a frontal view. The occlusal plane was determined by a line passing through the mesiobuccal cusp tip of the right and left permanent first molars and the mesiobuccal cusp tip of the right deciduous first molar or first premolar, in the maxilla and the mandible ( Supplementary Fig ). The 3 smaller purple arrows indicate the points used to create the occlusal plane represented as the green plane).
Mx1, Mx6, Md1, Md6 clinical crown heights The vertical distance between the incisal/occlusal and cervical limits of the tooth long axis buccal aspect of the central incisors and permanent first molars, respectively ( Supplementary Fig ). The means between the right and left sides were considered. ,
Arch dimensions, mm
Arch perimeter Measured as the sum of 4 segments: the linear distance between the mesial aspects of the permanent first molar and deciduous canine; linear distance between the mesial aspects of the deciduous canine and the central incisor, measured on the right and left sides ( Supplementary Fig ). ,
Arch length Measured perpendicularly to the horizontal plane from a line connecting the mesial aspects of the permanent first molars to a contact point between the central incisors or to a midpoint between them at the level of the gingival margin, in the absence of contact point ( Supplementary Fig ). ,
6-6 Interfirst permanent molars width at the level of the palatal/lingual gingival margin midpoint ( Supplementary Fig ). ,

Mx , Maxillary; Md , mandibular; 1 , central incisor; 6 , permanent first molar; 6-6 , interfirst permanent molar distance.

Sample size calculation

Sample size calculation was performed considering a significance level of 0.05, a test power of 80%, and an intergroup difference of 1.5 mm in the overbite with a standard deviation of 1.69 mm, as reported in a previous study. A minimum number of 21 patients was required in each group.

Interim analyses and stopping guidelines

Not applicable.

Randomization (random number generation, allocation concealment, implementation)

The randomization list was generated using random block sizes in the Web site ( ), ensuring equal distribution in the groups. Allocation concealment involved sequentially numbered, sealed, and opaque envelopes, containing the treatment allocation cards. The card with the assigned treatment was inserted into a foil for additional opacity. The envelopes were prepared before trial commencement. Before opening the envelope, the patient’s name and baseline information were written on its external surface. After, the envelopes were torn open and then were stored in a secured place different from the trial site. Different operators performed the randomization list, allocation concealment, and implementation.


Double blinding was not possible because the operator and patients knew the appliances that were installed during the clinical procedure. However, the digital dental models were unidentified and blindly assessed by a different operator (S.A.B.P). This trained operator was not involved with the randomization process or patients’ treatment.

Statistical analyses (primary and secondary outcomes, subgroup analyses)

Digital dental models (T1 and T2) of 15 patients were randomly selected and re-assessed by the same examiner (S.A.B.P) after 1 month. The intraclass correlation coefficient was used to evaluate the intraexaminer reliability.

All statistical analyses were performed using the SPSS statistical software (version 25; IBM, Armonk, NY). To adjust for the baseline values of each outcome, an analysis of covariance was used. Mean differences and their 95% confidence intervals (CIs) were obtained. The statistical significance was set at P <0.05.


Participant flow

During recruitment (June 2017 to April 2018), 1025 children were assessed for eligibility. From this sample, 969 were excluded because they did not meet the selection criteria, and 6 declined to participate in the study. Fifty patients were randomized in a 1:1 ratio ( Fig 3 ).

Fig 3
Consolidated Standards of Reporting Trials flow diagram.

Baseline data

The groups showed similar age and sex distribution ( Table II ). Baseline characteristics were also similar in both groups ( Table III ).

Table II
Baseline data: Age and sex distribution
Variable SBU group (n = 24) S Group (n = 25)
Mean SD Mean SD
Age, y 8.22 1.06 8.30 0.99
(Min, 7.00; Max, 10.67) (Min, 7.00; Max, 11.00)
n % n %
Female 17 70.8 14 56.0
Male 7 29.2 11 44.0

SD, Standard deviation; Min , minimum; Max , maximum.
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Jun 12, 2021 | Posted by in Orthodontics | Comments Off on Dental arch changes after open bite treatment with spurs associated with posterior build-ups in the mixed dentition: A randomized clinical trial
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