February, 2012

Asymmetric “T” Loop archwire for Deep Bite correction – A Case Report.

Authors:

Dr. JIGAR R. DOSHI  _M.D.S

Corresponding Author

Assistant Professor, Department of Orthodontics

Darshan Dental College and Hospital, Loyara, Udaipur

Phone: + 91-9537110110

E-mail: drjigar009@yahoo.co.in

Dr. KALYANI TRIVEDI  _M.D.S

Professor  & H.O.D,

Department of Orthodontics

Darshan dental college and hospital, Loyara, Udaipur

Email:  kalyanimtrivedi@rediffmail.Com

Dr. TARULATHA SHYAGALI  _M.D.S

Reader, Department of Orthodontics

Darshan Dental College and Hospital, Loyara, Udaipur

Phone:  +91- 7742129768

Email:  drdeepu20@yahoo.com

Abstract:

A deep bite is a very common malocclusion in orthodontics. Whenever a deep bite is present it is due to the extrusion of anterior teeth. There are three options to correct it. Correction of the Curve of Spee, intrusion and retraction by segmental mechanics and deep bite correction by a continuous loop archwire. Retraction and intrusion of the six anterior teeth under the edgewise system is usually carried out in two distinct steps: canine retraction followed by incisor retraction. In the begg and Tip- Edge techniques, canine and incisors are retracted and intruded by enmasse.

Key Words:  Deep bite correction, Loop mechanics, Asymmetric “T” Loop

The advantage of the separate canine retraction is that molar anchorage is conserved.  Towards the end of treatment there is frequently a need for additional maxillary anterior intrusion, space closure and lingual root torque.

The Asymmetric “T” Loop Archwire:

The asymmetric “T” loop archwire, a system made of .019 x .025” TMA (.022” brackets)  and .017 x .025 TMA (.018”brackets) has been proven effective in achieving simultaneous intrusion and retraction of incisors. This asymmetric “T” loop archwire has a loop that is placed distal to the upper lateral incisors. The loop can be activated intraorally for the multiple adjustments like, intrusion and retraction of incisors, or to increase torque during retraction.¹

Construction:

A small rounded bird beak plier is used to bend the loop into a preformed TMA archwire. Shape memory of the wire and the loop configuration make this a multipurpose system which can be incorporated into a continuous archwire. The vertical portion of the loop should be 5mm, the anterior loop 2mm, and the posterior loop 5mm. The archwire has an exaggerated reverse Curve of Spee and strong distal molar rotation. Bend the loop invards to prevent irritation to the cheek. (Fig 1)

Fig 1: Asymmetric “T” loop Archwire ( .019 x .025” TMA wire).

Case Report:

A 16 year old female reported with a chief complaint of irregularly and forward placed front teeth. On clinical examination and cephalometric evaluation she was diagnosed as an Angle class I dentoalveolar malocclusion with skeletal class II jaw relationship with anterior crowding in the upper and lower arch. She had an overbite of 6mm with excessive gingival display during smiling. (Fig 2) Her treatment plan was to extract the four I^st premolar teeth followed by fixed appliance therapy with the MBT pre-adjusted edgewise appliance( 0.022 slot).

Fig 2: Pre treatment photographs.

Treatment Progress:

The treatment started by banding and bonding of the upper and lower arch with a .022” preadjusted edgewise appliance. Leveling and aligning is done by .016” upper and lower Niti followed by a .019” x .025” Cu Niti and upper and lower  .019” x .025” SS wire. After leveling and aligning separate canine retraction was done by using an .011 x .030” 9mm  Niti coil spring. During retraction of the canine, anchorage control was maintained by using a .017 x .025 CIA intrusion archwire in the upper arch along with a TPA in the upper arch along with banding of  2^nd molars and a Lingual arch in the lower.  After canine retraction, simultaneous intrusion and retraction of the upper anterior teeth is done by using .019 x .025” TMA Asymmetric “T” loop archwire. (Fig 3) Reactivation was done by starching and bending of the wire behind 2^nd molar. Within 3-4 months a significant amount of intrusion and retraction was achieved. (Fig 4) After intrusion and retraction had been achieved, torque expression was achieved by using .019” x 025” TMA wire. (Fig 5) The treatment was completed within 18 months and pre and post radiographs showed absence of root resorption. (Fig 6, 7, 8)

Fig 3: With Asymmetric “T” Loop Archwire ( .019 x .025” TMA wire in .022” slot).

Fig 4: After Intrusion.

Fig 5: During Finishing Procedure ( by .019 x 25 TMA wires).

Fig 6: Post treatment photographs with corrected deep bite.

Fig 7: Pre treatment Xray.

Fig 8: Post treatment X-ray showing no root resorption.

Conclusion:

A deep bite has been considered one of the most common malocclusions and the most difficult to successfully treat. Therefore, the optimal treatment of deep bites requires a proper diagnosis, a careful treatment plan and an efficient appliance design.² Not all patients with deep overbite should be treated with the same mechanics. Some patients require intrusion of the anterior teeth, while others require primarily extrusion. This article has discussed the principles of incisor intrusion and has demonstrated the use of the Asymmetric “T” loop archwire that are capable of intruding incisors with minimal side effects on the posterior teeth. After correction, the deep bite was retained using a maxillary removable retainer with an anterior bite plane. It was needed for several years to maintain the correction.

Bibliography:

1. Hilgers JJ, Farzin N. Adjuncts to Bioprogressive Therapy The Asymmetrical “T” Archwire.  JCO 1992; 26(2):81-86.
   1. Burstone CR. Deep overbite correction by intrusion . Am J Orthod,   Volume 1977 Jul (1 – 22).
   2. Tayer BH. Modified T Loop archwire. JCO  1981;15(8)565-70.