Evaluation of Mini Plates Anchorage With Forsus Fatigue Resistant Device
Condition: Malocclusion, Angle Class II, Division 1
MeSH terms: Malocclusion; Malocclusion, Angle Class II; Overbite; Fatigue
Study type: Interventional

Summary: 
      The purpose of this study is to determine if the Forsus Fatigue resistant Device appliance
      with direct skeletal mini plates anchorage is capable of achievement of skeletal mandibular
      effects while preventing the excessive proclination of the lower incisors at the end of the
      treatment when compared to the conventional Forsus Fatigue resistant Device appliance applied
      to the upper and lower dental arches in female patients with skeletal Class II malocclusion
    

Detailed description: 
      1. Background:

           Class II malocclusions are characterized by an incorrect relationship between the
           maxillary and mandibular arches due to skeletal or dental problems or a combination of
           both. The prevalence of this malocclusion was recently found to be 20.6% in the Egyptian
           population in the age between 11 and 14 years with mandibular retrusion as its most
           common characteristic. It was also mentioned that other populations showed the
           predominance of the mandibular retrusion (80%) as opposed to only 20% expressing
           excessive maxillary development.

           Class II profiles attractiveness was previously investigated in the literature. It was
           found that patients, their peers, orthodontists and oral surgeons, rated subjects with
           Class I profiles as more attractive than others with Class II profiles. It was also
           reported that the profile of normal adolescent patients were more favorably perceived by
           laypersons than untreated Class II division 1 malocclusion subjects.

           In growing patients having Class II mandibular retrusion, functional orthopedic
           appliances are commonly used for mandibular advancement based on the concept of growth
           modification. However, two main problems appeared to compromise the desired treatment
           outcomes of these appliances; the need for patient cooperation and the lack of the
           possibility of combining their use with fixed appliance therapy in order to shorten
           treatment duration.

           Many systematic reviews and meta-analyses were recently performed in the literature
           answering the question of whether removable functional appliances (RFAs) produced
           skeletal effects for correction the skeletal discrepancy through inducing actual
           increase in mandibular dimensions. Most recently two systematic reviews concluded that
           the skeletal effects of RFAs were minimal and could be considered of negligible clinical
           importance. They mentioned that treatment of Class II malocclusion with RFAs was
           associated with a minimal stimulation of mandibular growth, a minimal restriction of
           maxillary growth and more significant dento-alveolar and soft tissue changes.

           Fixed functional appliances were first introduced by Emil Herbst in 1905. Many types of
           fixed functional appliances were developed since then; including Jasper jumper and Twin
           force Bite corrector . The Forsus Fatigue Resistant Device (FFRD) was introduced by Bill
           Vogt in 2006. It represented a semi-rigid fixed functional alternative that was intended
           to overcome breakage problems of flexible fixed functional appliances. However, it was
           proven that dental changes were more significant than skeletal changes in the final
           occlusal results. These changes included mesial movement of the mandibular molars and
           proclination of the mandibular incisors. These unwanted tooth movements appeared to
           compromise the actual skeletal correction and jeopardize the stability of the results.

           Several attempts were proposed to counteract the unwanted dento-alveolar side effects of
           fixed functional appliances. Use of lingual arches, increase the dimensions of the
           archwires, the introduction of negative torque in the archwires and the use of lower
           incisor brackets with lingual crown torque are some examples. Some studies used the mini
           implants in an attempt to limit the unwanted dental effects of fixed functional
           appliances. These studies proved that mini implants anchorage reduced the lower incisors
           proclination but they in turn increased the upper incisors retroclination and were not
           able to achieve significant skeletal mandibular effects.

           Titanium mini plates were introduced for the use for orthodontic anchorage in 1999 as a
           skeletal anchorage system for open bite correction. They were proven to be well accepted
           by patients and providers, safe and effective adjunct for complex orthodontic cases.
           Other uses of mini plates in orthodontics included maxillary and mandibular molars
           distalization and orthodontic anchorage where it was reported that they were able to
           provide absolute anchorage. Bone anchored maxillary protraction using mini plates was
           reported to be successful in producing significant forward maxillary growth in Class III
           growing subjects. Recently mini plates were used for the direct loading of FFRD for
           correction of skeletal Class II malocclusion. They reported actual skeletal changes
           through the increase in the mandibular length with minimal dento-alveolar side effects.
           However, these results are only preliminary and have to be taken with caution because
           the study did not include control group.

        2. Research Hypothesis:

           The null hypothesis (H0) of this research is that use of direct mini plate anchorage in
           conjunction with FFRD will not be able to induce skeletal rather than dental effects for
           correction of the skeletal Class II malocclusion in comparison with conventional FFRD
           therapy or with untreated growing Class II control subjects.

        3. Objectives:

           The primary objective of this study is to determine if mini plates use in conjunction
           with FFRD will induce supplemental growth of the mandible in Class II malocclusion
           subjects with mandibular retrognathism.

           Secondary objectives include

           To determine if mini plates use in conjunction with FFRD will be able to:

             -  Reduce the dento-alveolar side effects produced by fixed functional appliances in
                treatment of skeletal Class II subjects

             -  Correct the soft tissue convexity in Class II subjects

             -  Correct molar and canines relationships

             -  Develop a patients' well-accepted treatment modality for correction of skeletal
                Class II malocclusion.

        4. Study design

           According to the norms of the CONSORT STATEMENT, this study will be clinical with
           intervention, in which the allocation of the subjects will be randomized (block
           randomization). This study will be parallel with blinding for the outcome assessors. The
           primary purpose of this study will be treatment.

        5. Participants - Settings and locations where the data are collected

           The treatment will be performed in the outpatient clinics of Department of Orthodontics
           of Cairo State University. This public university predominantly serves low-income
           population living in Cairo, Egypt. Data will be collected from April 2015 through August
           2016.

        6. Interventions

      Two groups will receive treatment. Group 1 will be treated with the FFRD and mini plates
      anchorage for 10 months or until the correction of the malocclusion . Group 2 will be treated
      with conventional FFRD for 10 months or until the correction of the malocclusion. A third
      untreated control group will be included with an observation period of 6-8 months.

      7a. Sample size

      Our sample size calculation is based on a study which compared the use of Herbst appliance
      with and without mini implants anchorage and reported a significant increase in the Herbst
      mini screw group over their control group. The mean change in the mandibular length in the
      treatment and control groups were 4.6±2.43 mm and 0.9±2.09 mm respectively. Thus the mean
      difference was 3.7 with the within group standard deviation set at 2.26.

      Because three groups will be compared, Bonferroni adjustment was used as alpha level/number
      of comparisons = 0.05/3= 0.0167 to adjust for multiple comparisons.

      Power and Sample size calculation (PS) software (department of biostatistics Vanderbilt
      University) was used for sample size calculation. A t test was performed with the power was
      set as 0.9, allocation ratio of 1:1:1 and the Type I error probability (alpha) associated
      with this test was set as 0.0167. Results of the test showed that "The Group sample sizes of
      11, 11 and 11 achieve 90% power to reject the null hypothesis of equal means with a
      significance level (alpha) of 0.0167"

      Therefore, 33 subjects will be needed, with 11 subjects in each group. To account for patient
      loss to follow up (attrition), a sample size of 48 patients will be selected and divided into
      three groups, sixteen each.

      7b. Interim analysis and stopping guidelines

      In the group with mini plates anchorage, in case of mobility in the mini-plates in any
      subject, the load will be removed for about two weeks. After that, the load will be restored.
      If the mobility persists, surgical exposure of the mini plate will be done and either
      insertion of longer mini screws ion the same mini plate or a change in the position of the
      mini plate will be done.

      Any harms, adverse effects or unintended effects of the study intervention will be documented
      and reported. Post-surgical swelling and pain are anticipated and will be addressed by
      antibiotics and pain killers. Other unanticipated surgical harms have to be immediately
      managed and will be reported. Harms related to the orthodontic appliances will be managed by
      the principal investigator.

      8. Randomization

      8a. Sequence generation

      The randomization of the recruited subjects will be done with a randomized list, using
      random.org website. This list is made by an individual not involved in the clinical trial
      (S.B.)

      8b. Type

      The type of randomization will be block randomization. The number of blocks and block sizes
      will be blinded to the investigators.

      9. Allocation and concealment mechanism

        -  Each patient will be allocated a number from sequentially numbered opaque sealed
           envelopes after fulfillment of the inclusion criteria and signing the informed consent
           to be enrolled in the study.

        -  According to the number, the patients will be then allocated into one of the groups
           using a randomization table.

           10. Implementation

      Before the beginning of the research, the allocation sequence will be generated by a person
      not involved in the study (Dr S.B.). The random list will be sealed from the principal
      investigator who will enroll participants. After the participant takes a sealed number, S.B.
      will be contacted to implement the allocation. All the study contributors will have no access
      to the random list. The envelopes will be closed with the type of treatment selected for
      storage of the information.

      11. Blinding

      Blinding will be carried out only for the data assessment because the researchers,
      participants and subjects can not be blinded. Therefore, a person who does not know the
      nature of the trial will analyze the data.
    

Intervention name(s): FFRD and mini plates group; Conventional FFRD
Intervention type(s): Device; Device
Intervention description(s): FFRD direct loading over mini plates inserted in the mandibular symphysis; FFRD inserted between maxillary and mandibular arches with the pushrods placed distal to mandibular canines
Other intervention name(s): Mini plates anchored FFRD; Dental anchored FFRD
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: Forsus Fatigue Resistant Device; Class II; anchorage; FFRD; mini plates; fixed functional appliance