the objective of the current study is to compare the dentofacial effects of the mini-plate anchored Herbst appliance Versus the dentally anchored Twin force bite corrector Appliance in Young Adult Class II Orthodontic Patients with retruded mandible.

Study design:

Prospective randomized clinical study.

Study setting and population:

This study will be conducted on twenty orthodontic patients. The number of patients was dependent on a power study.

Sample size calculation was based on the observed average effect size derived from previous article addressing "the effect of skeletally anchored Forsus FRD using miniplates for the treatment of Class II malocclusion.

Intervention:

The orthodontic patients involved in this study will be treated by using fixed orthodontic appliances followed by one of two different types of fixed functional appliances; the type IV Herbst appliance (miniplate anchored appliance) and the Twin Force Bite Corrector (dentally anchored appliance). According to the type of the fixed functional appliance the patients will be randomly divided into two groups. The random allocation will be achieved by computer software:

• Group I: Include ten young adult orthodontic patients who are treated by using fixed orthodontic appliances followed by the type IV Herbst appliance (mini plate anchored appliance). The age of patients will be (15-20y).
• Group II: Include ten young adult orthodontic patients who are treated by using fixed orthodontic appliances followed by the Twin Force Bite Corrector appliance (dentally anchored appliance). The age of patients will be (15-20y).

Records:

The following diagnostic records will be taken for each patient before and after the fixed functional orthopedic treatment:

1. Standardized study casts.
2. Standardized extra-oral and intra-oral photographs.
3. Lateral cephalometric and panoramic radiographs.

Treatment steps:

As for Group Ι:

1. Two mini plates are chosen, the last hole in every plate is used to solder the ball housing of type IV Herbst appliance.
2. The two mini plates are placed bilateral at the mandibular symphysis and fixed by at least 3 screws, the surgical wound is sutured leaving an extended part of the plate in the oral cavity which contain the soldered ball housing.
3. The surgical wound is left for 2 weeks for proper soft tissue healing, in the meantime separation in the arch, band placement on the first premolar and molar bilateral followed by impression for construction of the upper Herbst splint.
4. Cementation of upper Herbst splint with connecting the telescopic piston through fitting of the plunger into the tube bilaterally.
5. When reactivation of the telescopic piston is needed, extension rings are used.

As for Group ΙΙ:

1. The patients will be treated by fixed orthodontic appliance with using series of orthodontic NiTi arch wires for levelling and alignment.
2. Installation of series of orthodontic stainless steel arch wires until 0.0019 x 0.0025 inch for both arches.
3. Installation of the Twin Force Bite Corrector appliance for 4 to 6 months.
4. Using of class ΙΙ intra-oral elastics for both sides for 2 to 3 months.
5. Finally follow finishing steps for each patient.

Data management and analysis:

The collected data will be tabulated statistically analyzed using Statistical Package for Social Sciences (SPSS, version 18, Inc, and Chicago, Ill).

Inclusion Criteria:

• Participants will be selected based on the following inclusion criteria:

  1. Skeletal class 2 malocclusion due to mandibular retrusion with increased overjet (SNA= 82±4, ANB=≥4°).
  2. Mandibular arch with minimum (up to 4mm) or no crowding.
  3. All permanent teeth are erupted (3rd molar not included).
  4. Good oral and general health.
  5. No systemic disease or regular medication that could interfere and/or affect orthodontic teeth movement.
  6. No previous orthodontic treatment.

Exclusion Criteria:

- 1. Patients with a blocked-out tooth that will not allow for placement of the bracket at the initial bonding appointment.

2. Patients with untreated decay or any endodontic lesions.