Orthodontic Approaches to Correct Deep Bite in Mixed Dentition Patients

Purpose: Deep bite, an increase from the normal overbite, is a problem that can be caused by a dentoalveolar and/or skeletal origin, and it is more common in class II malocclusion patients. Among children, the prevalence has been reported to range from 3 to 39%. This large variance can be explained by factors such as diagnosis criteria, sex, and ethnic group. Even though the stability and relapse of deep bite treatment have been previously discussed on permanent dentition, there is a lack of studies investigating their management during mixed dentition. Hence the goal of this clinical trial is to assess if any of the currently available approaches is more efficient considering factors such as costs, number of appointments, complications and patient's experience.

Hypothesis: The investigators hypothesized that the three active treatment approaches (bonded vs. cemented vs. removable) would produce similar dentoalveolar, skeletal and functional improvements. Those improvements would be larger than those observed on untreated children.

Justification: There is a lack of evidence regarding what early treatment approach for the deep bite is more effective, produces fewer side effects, and is more comfortable for patients. No randomized controlled trial evaluating the effectiveness of deep bite treatment during the mixed dentition has been identified. Early intervention may simplify future comprehensive orthodontic treatment. Moderate to severe deep bite cases could affect sagittal mandibular growth.

Objectives: This study aims to evaluate the effectiveness of two deep bite orthodontic treatments among children in the mixed dentition phase. Additionally, treatment duration, quality of life changes and complications of the different performed interventions will be assessed.

Research Method/Procedures: This study will be a stratified, parallel randomized controlled, single-blinded, with an allocation ratio of 1:1:1. The sample will be composed by children in mixed dentition (7-11 year olds), referred or self-referred to the orthodontic clinic at the University of Alberta (Edmonton, Alberta, Canada). The inclusion criteria will be: presence of moderate to severe deep bite (overbite >5.0 mm), fully erupted maxillary and mandibular incisors, as well as first permanent molars, no missing permanent incisors and molars, no clinically noticeable craniofacial syndromes and no clear need for immediate intervention to manage severe sagittal, transversal or vertical malocclusions. The participants will be divided into three groups:

1. no treatment of deep bite now - deferral to permanent dentition;
2. treatment with a cemented modified palatal Nance appliance including an anterior bite-plane;
3. treatment with a composite build up in the palatal aspect of the upper central incisors.

The effectiveness of interventions (elimination of the moderate to severe anterior deep bite) will be assessed as a primary outcome. Secondarily, treatment duration, compliance, and complications among patients using the appliances will be evaluated. The treatment effectiveness will be evaluated according to the following criteria:

• The success rate of deep overbite correction (yes or no). The success in overbite correction will be defined as the complete dissolution of deep bite, with an overbite <3mm. This will be assessed by comparing digital bite models from before (T0) and after treatment (T1).
• Treatment duration in months: from the beginning until the end of the intervention (correction of deep bite up to a maximum of 12 months). The number of appointments will also be calculated.
• Measurement of overjet and overbite in millimeters; arch length to incisal edge in millimeters; maxillary dental arch length total (ALT) in millimeters; transverse maxillary molar distance (MD) in millimeters. Obtained from digital bite models.
• Cephalometric analysis. Skeletal and vertical sagittal measurements, as well as interdental, maxillary and mandibular dentoalveolar measurements, will be collected for each participant. Conventional 2-D Lateral cephalograms will be taken from all patients before treatment (T0) and at the end of the active intervention (T1).

The overjet, overbite, and the arch length will be measured electronically. Cephalometric measurements will be made with a commercial software. All measurements were made to the nearest 0.1 mm by an orthodontist. The analyses will be blinded regarding treatment received and time. Changes in the different measures were calculated as the difference between T1 and T0. Finally, the duration of treatment (no more than 12 months) will be considered.

Data on all patients will be analyzed on an intention-to-treat (ITT) basis, i.e., if the deep bite was not corrected during the 1-year trial period, the outcome will be declared unsuccessful. Thus, all patients, successful or not, will be included in the final analysis. The dropouts during the trial will be evaluated regarding the reasons and the data collected during the study to be considered as effective or ineffective.

Cephalometric and digital bite models measurements of 10 patients will be repeated by the same observer, a trained orthodontist, after four weeks to measure the intraobserver reliability. The reliability will be measured using Dahlberg formula for random error analysis and intraclass correlation (ICC) for the evaluation of systematic errors.

As a secondary outcome, the number of breakages, additional appointments for appliance repairs, appliance repairs made and emergency appointments will be collected to evaluate the complications of each treatment. In the removable appliance group, the compliance will be evaluated using a using an incorporated microsensor.

Quality of life will be assessed using previously validated questionnaires specific to age groups. For 8 to 10 year-old the CPQ8-10 which consists of 25 questions distributed among 4 domains (oral symptoms, functional limitations, emotional well-being and social well-being). For 11 to 12-year-old the CPQ11-14 which consists of 37 questions distributed among 4 domains (oral symptoms, functional limitations, emotional well-being and social well-being). The P-CPQ, a measure of parental/caregiver perceptions of the oral health-related quality of life of children will also be used.

The sample size was calculated based on a power analysis, considering overbite as the primary variable. To achieve a power of the study of 0.8, a difference among treatments of 1mm (variance of 1.5mm2) at a level of 0.05, each group of patients under investigation had to include 24 subjects. Considering a possible dropout rate of 20% in each group, 29 subjects will be recruited in each group, resulting in a total initial sample of 87 children. Data from Bacetti et al 2012 study comparing deep bite correction between mixed mention and permanent dentition used as reference (1.7 mm difference with sd of 1.3 mm).

A computer-generated list of random numbers will be used to randomly selected sample from a large pool of participants (SPSS Inc., Chicago.). This process will be conducted by a person not involved in the study. The random allocation process will be performed using opaque sealed envelopes which will contain the assigned group for each patient and were not opened until the onset of the trial. The enrolment of participants and their assignment will be done by an orthodontic staff member not directly involved in the intervention and follow-up. A computer-generated list of random numbers will be used to randomly selected sample from a large pool of participants (SPSS Inc., Chicago.). This process will be conducted by a person not involved in the study. The random allocation process will be performed using opaque sealed envelopes which contained the assigned group for each patient and were not opened until the onset of the trial.

Plan for Data Analysis: Data normality will be examined using the Shapiro-Wilk test. A multiple analysis of variance (MANOVA) will be used to evaluate repeated-measures data between T0 and T1 in each group. Intergroup comparison among different intervention groups will be performed using multiple analyses of variance (MANOVA), with Tukey ́s posthoc test. All statistical analyses will be conducted using IBM SPSS Statistics 22 (SPSS Inc., Chicago, IL, USA) software, with a 0.05 level of significance.