In lingual movement of anterior teeth with sliding mechanics, the mechanism of lingual tipping occurring in the anterior teeth was investigated based on the finite element method. In the intramaxillary retraction, lingual tipping of the anterior teeth was caused by elastic deflection of the archwire. When decreasing the retraction force or increasing the archwire size, the lingual tipping decreased. When using an archwire with antibowing bend, deflection of the archwire and lingual tipping of the anterior teeth could be prevented. When incorporating lingual root torque into the anterior brackets, the lingual tipping of the anterior teeth could be prevented, but the deflection of the archwire could not be prevented. In a retraction of the anterior teeth using anchor screw, lingual tipping was caused by not only deflection of the archwire but also rotation of the whole dentition. When incorporating antibowing bend into the archwire, the deflection of the archwire could be prevented, but the rotation of the whole dentition could not be prevented. When applying a parallel force to the archwire with a long arm, the action line of the retraction force passed near the center of resistance of the anterior teeth, and thereby the anterior teeth moved bodily without rotation of the whole dentition and deflection of the archwire.

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The multi-slot lingual bracket has the following advantages: 1. Upper lateral incisor is prevented excessive proclination when it is aligned to labial side. 2. A horizontal slot and vertical slot are compensated their weak points each other. 3. It is possible to open the space earlier where the tooth cannot be placed bracket due to crowding. 4. Lingual straight archwire is easily carried out by using small size brackets on the molar teeth. 5. Tartar is prevented to invade to the bracket slot and under the tie wing because of the large bracket size. These benefits will be presented with a case report. This patient was a Japanese girl aged 14 years. Her chief complaints were crowding and proclined incisors. The crowding and large overjet were observed. The inter-molar relationship was an Angle Class II. In the lateral cephalogram, skeletal Class II and high mandibular plane angle with backward rotation of the mandible were analyzed. The upper and lower incisors were proclined. Above these findings, this case was diagnosed as an Angle Class II crowding with high mandibular plane angle. The upper both first premolars and lower both second premolars were extracted. Then, upper incisors were retracted by using lingual multi-bracket appliance and mid-palatal miniscrews.

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In lingual orthodontic treatment, the placement of brackets by applying a Set-up model and indirect core is the decisive factor in achieving the treatment goal. However, in both digital and analog conventional manner, occlusal plane angle and tooth angle of front view are not always accurate. Therefore, TOP analyzer system （Tagahara Occlusal Plane analyzer system）, pioneered and developed by the author, has come up with a solution to this existing problem by its clinical application. This system provides precision, ease of use and it is appropriate for interdisciplinary approach.

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We have been using elinesystem for 2 years which is created by Dr. Scuzzo in 2017. As we have been producing conventional analogue set-up model on the other hand. A lot of doctors adopt oral scanner currently and combinations to order for set-up model is also increasing compare to before such as (Digital system) • Making digital set-up model from digital impression • Making digital set-up model from silicon impression (Analog system) • Making analog set-up model from digital impression • Making analog set-up model from silicon impression In addition, there are some characteristics of both methods such as (Digital system) • Plaster model is not required • Unaffected by wax to deformed (Analog system) • To be able to remake and re-setup quicker when re-bonding • To be able to touch set-up models directly Then I describe about characteristics of digital/analog setup and whether digital technology brings positive impact on orthodontics as a dental technician's view.

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