Clinical Evaluation of Bio-creative Therapy for En Masse Retraction of the Maxillary Anterior Teeth
Condition: Malocclusion, Angle Class II, Division 1
MeSH terms: Malocclusion; Malocclusion, Angle Class II; Overbite
Study type: Interventional

Summary: 
      The purpose of this study is to compare the effectiveness and efficiency of labial versus
      lingual biocreative therapy in achieving en masse retraction of the maxillary anterior teeth
      in subjects with class II malocclusion requiring upper first premolar extraction.
    

Detailed description: 
      1. Background:

           Maximum anchorage is commonly required in patients with severe protrusion. Conventional
           retraction by sliding mechanics in extraction cases have been associated with variable
           degrees of anchorage loss. Use of miniscrew for reinforcement of orthodontic anchorage
           has become increasingly popular in recent years. Miniscrews are convenient, save time,
           and do not require patient cooperation. However, sliding mechanics with direct anchorage
           from mini-screw can have several biomechanical drawbacks. The force used during
           retraction is not reciprocal, posteriorly it is negated by the miniscrew, not by teeth.
           As a result, either the entire arch or the anterior segment rotates around the center of
           resistance. These mechanics produce posterior open bite and anterior deep overbite. To
           avoid this problem, Chung et al, introduced the technique that minimizes side effects by
           replacing the posterior appliance segments with the partially osteointegrated C-implant.
           This system was called "biocreative therapy".

           With the bio-creative approach, true intrusion vectors on the anterior teeth can be
           applied without unwanted reactive forces affecting the posterior teeth, the posterior
           teeth are left intact.

           In Labial biocreative therapy type I, a 0.016 × 0.022-in stainless steel utility
           archwire is placed from the anterior segment into the implant tube, and gable bends are
           used to generate an anterior torque moment on the anterior segment of the teeth to
           provide bodily movement during en-masse retraction. On the other hand, in biocreative
           therapy type II, en masse anterior retraction is accomplished by applying retraction
           force via NiTi coil springs between an anterior retraction hook placed between the
           lateral incisor and the canine and the skeletal anchorage. An overlay intrusion arch
           wire is used to generate torque on the anterior segment of teeth; thereby various
           patterns of tooth movement can be obtained through the combination of intrusion force,
           retraction force, and length of the retraction hook. Location and management of the
           center of resistance (Cres) with respect to retraction force vectors is critical. The
           clinician should select the length of a power arm according to the desired type of tooth
           movement; controlled lingual crown tipping, root tipping, or bodily movement.

           Adult orthodontics is an increasing part of the orthodontic practice. However, adult
           patients are often annoyed by the appearance of labial brackets and tend to delay or
           avoid starting orthodontic treatment. Lingual orthodontics is a viable option for these
           patients as being "invisible orthodontic treatment". The disadvantages of lingual
           orthodontics include the excessive chair time, complicated bio-mechanics, patient
           discomfort, expensive lab procedures, and high material prices. However, several
           innovations have improved the use of lingual orthodontics, such as customized lingual
           brackets and two-dimensional lingual brackets that can be bonded directly. Nonetheless,
           the efficient control of anterior torque and intrusion during retraction continues to be
           a limiting challenge.

           Mini-implants placed on each side of the palate have been used in conjunction with
           lingual orthodontics to avoid uncontrolled tipping and the deepening of the anterior
           bite during en masse retraction. A lever arm is soldered to the main lingual arch wire.
           This moves the force vector apically and closer to the center of resistance, thereby
           allowing better control of torque during retraction. However, play within the slot
           allows some of the torque to be lost during retraction. In addition, unwanted canting of
           the occlusal plane may occur if bilateral mini-implants are not in the same horizontal
           plane, due to different force vectors generated during retraction. Moreover, the sliding
           mechanics may be adversely affected by friction within bracket slots and tubes, causing
           unwanted distalization of posterior teeth.

           Lingual Biocreative therapy for anterior retraction offers several advantages. En masse
           retraction of the maxillary anterior dentition is achieved using C-lingual retractor and
           C-palatal plate. The C-lingual retractor is bonded to the lingual surfaces of the upper
           six anteriors, providing excellent esthetics. The C-palatal plate is fixed near the
           median palatal suture with mini-implants. The upper posterior orthodontic appliances are
           not needed as anchorage for 3-dimensional retraction of the upper anteriors.

           Lingual biocreative therapy technique can be used to provide patients with esthetic
           treatment, excellent anchorage control offered by skeletal anchorage, rapid and
           controlled retraction, simplified orthodontic bio-mechanics, and avoiding unnecessary
           use of complex orthodontic devices. Posterior teeth are not disturbed by friction in the
           appliance.

           As the majority of research work related to biocreative therapy technique was mainly
           case reports, three-dimensional finite element analyses, and three retrospective studies
           using two-dimensional cephalometric data, and the fact that no studies; up to the time
           of this writing; compared the labial and lingual biocreative techniques, the idea of
           this study has aroused as to use the advanced technology of three-dimensional imaging to
           clinically evaluate and compare the effects of labial and lingual biocreative therapy
           for en masse retraction of the maxillary anterior teeth.

        2. Research Hypothesis:

           The null hypothesis (H0) of this research is that there will be no statistically
           significant differences between labial and lingual biocreative therapy in the mean
           change in the upper incisor inclination after en masse retraction of the anterior teeth
           in subjects with class II malocclusion requiring upper first premolar extraction.

        3. Objectives:

           The primary objective of this study is to determine if there will be statistically
           significant differences between labial and lingual biocreative therapy in the mean
           change in the upper incisor inclination after en masse retraction of the anterior teeth.

           Secondary objectives include:

           To compare between labial and lingual biocreative therapy regarding:

             -  Changes in the soft tissue parameters including the nasolabial angle, inter-labial
                gap, and position of the upper and lower lips in the antero-posterior dimension;
                that would contribute to soft tissue profile correction.

             -  Molar anchorage loss.

             -  Patient satisfaction from treatment with either the labial or lingual biocreative
                therapy.

             -  Vertical movement of the crown of the six maxillary anterior teeth.

             -  Changes in the transverse dimension of the upper arch.

             -  Skeletal measurements including the mean change in the position of point A from the
                Nasion perpendicular plane and change in the SNA angle.

             -  Time duration required to complete the retraction phase.

        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 Ain Shams
           University. This public university predominantly serves low-income population living in
           Cairo, Egypt. Data will be collected from January 2016 through November 2017.

        6. Interventions Two groups will receive treatment. Group 1 will be treated with the labial
           biocreative therapy group until the achievement of normal overjet (1 to 3 mm).

      Group 2 will be treated with lingual biocreative therapy group until the achievement of
      normal overjet (1 to 3 mm).

      7a. Sample size Sample size calculation was based on the studies by Kim et al and Kim et al.
      For the labial group, a mean change in the upper incisor inclination to SN plane of 15.33
      degrees, with a standard deviation of 6.85 was reported by Kim et al who compared
      pre-treatment cephalometric radiographs with those taken after en-masse retraction of the 6
      anterior teeth using temporary skeletal anchorage devices as the exclusive source of
      anchorage. No brackets or bands were placed on the posterior dentition during retraction.
      Regarding the lingual group, the mean change in the upper incisor inclination to SN plane of
      7.8 degrees, with a standard deviation of 5.5 was reported by Kim et al who compared
      pre-treatment cephalometric radiographs with those taken after en-masse retraction of the 6
      anterior teeth using the lingual biocreative therapy technique.

      The effect size ratio was calculated to be 1.212 using G*power software (Universität
      Düsseldorf, Germany). A t-test assuming equal variance for two independent groups was used
      and the power was set as 0.8, allocation ratio of 1:1 and the Type I error probability
      (alpha) associated with this test was set as 0.05. Results of the test showed that "the group
      sample sizes of 12 each would achieve 80.09% power to reject the null hypothesis of equal
      means with a significance level (alpha) of 0.05 using a two-sided two-sample equal variance
      t-test".

      Therefore, 24 subjects will be needed, with 12 subjects in each group. To account for patient
      loss to follow up (attrition), a sample size of 30 patients will be selected and divided into
      two groups, fifteen each.

      7b. Interim analysis and stopping guidelines In both groups, in case of mobility in the
      skeletal anchorage device used in any subject, the load will be removed for about two weeks
      and oral hygiene instructions will be reinforced. After that, the load will be restored. If
      the mobility persists, surgical exposure of the skeletal anchorage device will be done and
      either insertion of longer mini screws or a change in the position of the skeletal anchorage
      device 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 (A.Z.) 8b. Type The type of randomization will be block
      randomization. The number of blocks and block size 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 fulfilment 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 A.Z.). The random list will be
           sealed from the principal investigator who will enrol participants. After the
           participant takes a sealed number, A.Z. 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): Biocreative therapy
Intervention type(s): Procedure
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Outcomes Assessor)
Primary purpose: Treatment
Keywords: en masse retraction; biocreative therapy; class II; skeletal anchorage