Methodology
A prospective randomized control study will be conducted in Department of Dentistry at AIIMS, Jodhpur. Fifty four subjects requiring treatment for anterior cross bite correction will be included in the present study. Subjects will be randomly allocated into two groups: one as fixed appliance therapy (FA) group and other as removable appliance therapy (RA) group. Randomization code will be computer generated and allocation concealment will be done using sealed opaque envelopes. Inclusion Criteria: 1. Subjects in mixed dentition with anterior cross bite affecting one or more incisors. 2. Subjects with minimal space discrepancy of less than 4mm. 3. Subjects with no history of previous orthodontic treatment. Exclusion Criteria: 1. Subjects with more than two teeth in cross bite. 2. Subjects with skeletal malocclusions. 3. Subjects with cleft lip or palate and medically compromised conditions.
After getting an informed written consent, patients will be randomly allocated into two groups with each group consisting of twenty seven patients. After randomization, all patients will be treated according to a pre-set standard concept. Study models and diagnostic radiographs will be taken for all subjects at the start (T0) and immediately after treatment completion (T1). Materials used will be: 1. Gloves and Mask 2. Alginate impression material 3. Dental stone for study models 4. Diagnostic radiographs 5. Components of removable appliance therapy 6. Components of fixed appliance therapy
Methodology: Removable appliance therapy: The appliance will comprise an acrylic plate, with double cantilever spring for the incisors in anterior crossbite, bilateral occlusal coverage of the posterior teeth, stainless steel clasps on either the deciduous first molars or the first premolars (if erupted) and the permanent molars. The double cantilever springs will be activated once a month until normal incisor overjet is achieved. Occlusal coverage is used to avoid vertical interlock between the incisors in crossbite and the mandibular incisors and also to increase retention of the appliance. The occlusal coverage will be removed as soon as the anterior crossbite is corrected. The patient is firmly instructed by the dentist to wear the appliance day and night, except for meals and tooth-brushing, i.e. the appliance has to be worn full time. Progress will be evaluated after every four weeks. Fixed appliance therapy: The fixed appliance will consist of 0.022-inch slot (MBT prescription) pre-adjusted edgewise appliance in the form of two by four appliance. 2x4 appliance comprises of bonds/bands on the permanent maxillary first molars with brackets bonded to the four maxillary incisors and a continuous arch wire. Deciduous canines will be bonded if the lateral incisors are in erupting stage. All patients will be treated using round nickel titanium arch wires for initial alignment and cross bite correction. To raise the bite glass ionomer cement (GIC) will be placed on the occlusal surface of maxillary or mandibular permanent first molars. This will avoid the vertical interlock between the incisors and allow free labial movement of incisors in cross bite. GIC will be removed as soon as the anterior cross bite is corrected and a positive overjet is established. Treatment progress will be evaluated once for every four weeks.
The outcome measures in the study includes the following: • Success rate of anterior cross bite correction (Yes / No) • Treatment duration in months: From insertion to date of appliance removal • Number of visits taken to correct the anterior crossbite • Overjet in millimeters • Change in maxillary incisor inclination using cephalometric analysis Successful treatment will defined as positive overjet (normal inter-incisal relationship) for all incisors at T1, when treatment is completed or at the latest within one year of treatment start T0. The duration of treatment and number of visits will be registered from the patient files as the time taken in months and number of visits to correct the anterior crossbite. If normal overjet is not achieved, the treatment time is recorded as one year, i.e. the pre-set maximum duration of treatment. If the anterior crossbite is not corrected within one year, the outcome is defined as unsuccessful. Thus, all cases, successful or not, will be included in the final analysis. Statistical analysis: The sample size for each group is calculated based on a significance level of α = 0.05 and a power (1-β) of 90 percent to detect a mean difference of 1 month (±1 month) in treatment duration between the groups. Regarding the sample size calculation, each group would require 21 subjects. In order to compensate for possible dropouts, it is decided to select further 12 patients, i.e. 27 subjects for each group. SPSS software (Version 20.0) will be used for statistical analysis of the data. For numerical variables, arithmetic means and standard deviation will be calculated. Analysis of means will be made with independent sample t-test to compare active treatment duration and treatment effects between the groups. A P value of less than 5 percent (P=0.05) will be regarded as statistically significant.
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