The patient, a 21-year old woman , had a convex profile , class I dental malocclusion ,anterior open bite of 4 mm . She was a mouth breather and presented tongue thrust. Her chief complain was the anterior open bite .(Figure 1)

Figure 1. Pretreatment intraoral photography

The cephalometric analysis indicated that she had a skeletal class II profile ,proclination of the maxillary central incisor ,high mandibular plane angle that contributed to the class II skeletal relationship and increased lower facial height.

Figure 2. Pretreatment cephalometric film

The panoramic radiograph showed bilateral mandibular third molars. The level of alveolar bone crest was within the normal range. (Figure 3)

Figure 3. Pretreatment panoramic X-ray

Figure 4. Intraoral photography at the start of the treatment.

Theories to explain the cause of anterior open bite: digital habits , airway obstruction, tongue posture, unfavourable growth, tongue trust .²

The patient presented tongue thrust and mouth breathing. She was reffered for myofunctional exercises for tongue thrusting before orthodontic mechanics began.

·To maintain class I molar and canine relationship with ideal overjet and overbite while maintaining facial esthetics

·Avoid extrusion of the molars and clockwise rotation of the mandible during treatment

·Close the anterior open bite

Anterior open-bite treatment alternative:

1.Extrusion or eruption of anterior teeth. Several authors reported the side- effects of this orthodontic movement: root resorption, less stability and esthetics ⁷

2.Intrusion of the lateral teeth- Studies reported different methods to intrude the posterior teeth ( posterior bite blocks, high- pull headgear , mini-implants )⁸

3. Orthognathic surgical impaction of the posterior maxilla to allow the mandible to autorotate counter clockwise and close the bite .

4. Extraction of the first premolars in order to close the bite and reduce the overjet.

5. Surgical removal of all third molars was indicated before appliance removal.

The patient refused orthognathic surgery and premolar extractions and elected the less invasive orthodontic treatment .

After obtaining the informed consent the orthodontic treatment began and 0,22 Roth straight-wire fixed appliances were bonded. After leveling and aligning, during upper arch expansion, we took impressions and made intermediate study models. We noticed that palatal cusps of the upper premolars could not be intruded by classic mechanics. We decided to intrude first and second bicuspids to resolve the open bite. Skeletal anchorage was indicated and two orthodontic mini-implants were inserted on the palatal side between the premolars.

In the palatal area the soft tissue is thicker than in other areas¹² . It is important to measure the soft tissue thickness to determine the ideal length of the mini-implant .

Mini–implant failure arises from the possible complications : root/periodontal damage, damage to neurovascular tissues, mini-implant fracture, soft tissue problems, biomechanical side-effects. ^{14, 15, 16, 17}.

In this case the patient had no complications

The optimal force for intrusion reported by several authors are : 20 g of force for the anterior teeth- Burstone⁹, Gianelly and Goldman 15-50 g force¹⁰ .For the molar intrusion, the initial force recommended by Umemori et al is 500 g ¹¹, Melson and Fiorelly used 50 g buccolingualy to intrude maxillary molars.¹³. Reitan and Rygh ⁶ reported that intrusion is more stable than extrusion

In this case the implants were loaded after one week with a 100-150 force using an elastic chain.

The intrusion rate obtained was 0,5-1 mm per month without root resorbtion or vitality problems.

Tongue therapy was performed.

Before the finishing stage, a panoramic x-ray was taken. The third molars were removed .(Figure 6)

Figure 5. Intraoral photography after the mini-implant activation

Figure 6. Panoramic X-ray before the removal of the third molars.

Figure 7. Clinical situation after intrusion with orthodontic implants.