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Ortho - international magazine of orthodontics No.1, 2017

| industry report rapid overbite correction Fig. 5a Fig. 5b Fig. 5c Fig. 5d Fig. 5e Fig. 5f resistant to orthodontic correction. This strong skeletal growth pattern is another reason deep over- bites are one of the most difficult challenges, and where BT2s are valuable in controlling or breaking the pattern of CNS-muscle hyperactivity. Fig. 5g Fig. 5h When to apply BT2s? Humans use only approximately 10 % of their muscle activity for chewing (25 lbs). However, it is well known during clenching and other parafunctional ac- tivity that these forces can exceed 10 times the chew- ing force (250 to 300 lbs). Normal swallowing takes place approximately 600–1,000 times/day or more (in- cluding during chewing and speaking) that maintains the restriction of dental eruption in the buccal seg- ments into adult life (Figs. 4a & b). BT2s are used in con- junction with active self-ligating appliances due to the low resistance of the appliance shown in vitro, to per- mit unobstructed and controlled extrusive move- ments of the archwires at the upper and lower buccal segments. Once the posterior vertical dimension in- creases and the incisors begin to develop a positive overbite relationship, the tongue generally begins to rebalance vertically into the greater vertical space and more posteriorly into a more natural tongue position. This assumes the aetiology of the deep overbite has been additionally controlled long term with an ante- rior bite plane to be worn for one-year post-treatment, then overnight every night. In addition to CNS-muscle hyperactivity, deep overbites are associated with skeletal counter clock- wise rotation of the mandible as part of the archial growth path of patients with brachyfacial types.10-11 This can explain why it is not unusual that as the orthodontist attempts to increase the vertical dimen- sion in a growing child with strong anterosuperior growth of the condyles and a counter clockwise mandibular rotation pattern compounded by severe CNS-muscle hyperactivity, the deep overbite is highly BT2s are recommended at all ages, including for both early interceptive treatment in children, and in adults (Figs. 5a–h). Prior to the placement of BT2s, all patients, particularly sensitive adults are informed most importantly, that the new BT2 technology will save several months (up to 3–4 months) of orthodon- tic treatment of the overbite that is the largest chal- lenge. Sensitive patients are instructed it will possibly take 2–3 days to accommodate to the new vertical height, and to the feeling of the BT2s where wax is also provided to place over the BT2s for 3 days. Eating may temporarily be affected requiring soft foods, and they may also possibly affect speech mildly and temporarily (that is uncommon with the bulbous ends of two BT2s). The ideal recommended time of BT2 placement is at the time of the bracket placement (that are regularly positioned on the labial aspects). BT2s and active self-ligating brackets are ideal with synergistic, specialised i-Arch wires (SIA Orthodontic Manufac- turer) that have a higher vertical dimension than horizontal dimension (for example .018 x .014) for early moments of torque for control of the roots re- quired in deep overbite correction. The archwires, once again, incorporate compensat- ing curve on the upper archwire and reverse curve of Spee for the lower archwire to further facilitate incisor intrusion. BT2s are worn for at least 6 months and tooth movements are facilitated by the eruption (or extrusion) of the buccal segments, where the rhomboid-shaped elastics (1/4, 4.5 oz) are place bi- laterally. No clinically significant root resorption is Figs. 5a & b: A severe, skeletal mandibular overclosure is characterised by a counter clockwise rotation of the mandible associated with CNS-muscle hyperactivity including clenching and parafunction that is ideal for BT2 application. Figs. 5c & d: A deep overbite with wear of the cusp tips associated with CNS-muscle hyperactivity are shown in the Class II division 2 malocclusion on the patient’s left side. In addition, periodontal gingival recession is evident. Fig. 5e: Panoramic radiograph reveals the intrusive effect on the buccal segments classified as skeletal restriction of eruption, with CNS-muscle hyperactivity. Early periodontal bone loss is additionally observed. Fig. 5f: Downward and backward rotation of the mandible during BT2 treatment that improves the initial severe chin protrusion. Figs. 5g & h: Good harmony and balance are restored to the smile with a Class I functional occlusion and good incisor torque. Extensive gingival allografting was also successfully undertaken that was associated with parafunction and possibly toothbrush abrasion causing the initial, severe gingival recession. 34 ortho 1 2017

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