August, 2011

Deep Bite Correction with Cetlin’s Intrusion Arch

Dr. Amit Prakash
Senior lecturer
Department of Orthodontics and Dentofacial Orthopedics
Darshan dental college and hospital, Loyara, Udaipur

Dr. Arundhati P. Tandur
Professor
Department of Orthodontics and Dentofacial Orthopedics
K.L.E.S Institute of Dental Sciences, Bangalore

Dr. Tarulatha  Shyagali
Reader
Department of Orthodontics and Dentofacial Orthopedics
Darshan dental college and hospital, Loyara, Udaipur

Dr. Rahul Bhargava
Senior lecturer
Department of Conservative dentistry
Darshan dental college and hospital, Loyara, Udaipur

Corresponding address –

Dr. Amit Prakash
Department of Orthodontics and Dentofacial Orthopedics
Darshan dental college and hospital, Loyara, Udaipur

E-mail address-
drprakash24@yahoo.co.in
amitprakash30@gmail.com

Abstract

The orthodontic correction of deep overbite can be achieved with several mechanisms that will result in true intrusion of anterior teeth.  Deep overbite correction by intrusion of anterior teeth affords a number of advantages including simplifying control of the vertical dimension and allowing forward rotation of the mandible to aid in Class II correction. Intrusion of anterior teeth to correct deep overbite may be indicated in patients with unaesthetic excessive maxillary incisor showing at rest and a deep mandibular curve of spee associated with a long lower facial height. This article highlights the treatment of deep bite with Cetlin’s intrusion arch.

Key words: Deep bite, Class II division 2

Most Class II division 2 malocclusions manifest a deep overbite. This can be corrected by the intrusion of the maxillary anterior teeth. By intruding the anteriors the roots of the incisors are brought into a wider part of the premaxilla, which makes retraction and torque control of the incisors easier and reduces the risk of encroaching on the labial or palatal cortex.

Basic principles

Intrusion of the upper incisors is difficult. An appropriate, effective and clinically manageable biomechanical system is required. Burstone¹ has listed the important principles for obtaining intrusion- light and constant force, single point of force application, sequential intrusion, good control of anchorage, analysis of forces and moments involved in different biomechanical situations.

Light constant force

About 20gms of force is sufficient to intrude the upper incisors. If a heavier force is applied, it leads to root resorption and problematic anchorage control. Therefore, to intrude incisors, a wire with a low deflection rate should be used. 0.018” Australian special plus wire is the wire of choice. This intrusion arch used was Norman Cetlin’s design.² Helices are used to engage light retraction elastics if needed. They can be opened to facilitate insertion and removal. Intrusion force is provided with two tipback bends 2-2.5mm anterior to the molar auxiliary tube. Bends allow for sliding when incisors are intruded and retracted.

Single point of force application

Even a round wire in an edgewise slot tends to produce torque due 2 point contact. The derived force system is indefinite and unpredictable. Secondary effects vary in such a system. An intrusion archwire tied to a sectional wire allows for forces to be applied to a single point and it is easy to manage.

Anchorage control

Control of the reacting unit is crucial. On molars, extrusive forces and movements that tend to tip the crown distally are applied. To limit these undesired movements, intrusive forces are kept low. Only a few appliances can be added to the molars to enhance the anchorage.

These are:

1. Low palatal bar to counteract extrusive components

2. High pull headgear to counteract extrusive and tipping movements

3. Sectional wire from first to second molar to prevent distal tipping

Case report

A 23 year old female reported with the chief complaint of irregularly placed upper front teeth. She had a skeletal and dental class II malocclusion with upper and lower anterior crowding. She had an overbite of 7mm (100 %) and an anterior marginal gingival discrepancy. (Fig 1)

Fig 1-Pre-treatment photographs

Treatment progress

Only upper anteriors were bonded initially. Cetlin’s intrusion arch made up of sectional 0.017x.025 stainless steel wire was placed in the upper centrals. In the auxiliary tube an 0.016 premium plus wire with the anchor bend was placed. Intrusion forces of 40 gm  was balanced, which guided upper incisor root apices lingually, thereby reducing the need for root torque to finish the case. Anchor bends in the upper archwire will procline the upper incisors, but with a tight cinch, the incisors did not procline and there was controlled lingual root movement of the central incisors. After 2 months, a sectional 0.019x.025 stainless steel wire was placed in the upper centrals. (Fig 2) An 0.018 premium plus wire with the anchor bend was placed in the auxiliary tube. 4mm of intrusion was achieved in 5 months which has corrected the deep bite and the anterior gingival marginal discrepancy. (Fig 3) Case was treated with a fixed functional appliance (Forsus) and treatment was completed in 18 months. (Fig 4) Pre and post radiographs shows absence of root resorption. (Fig 5,6)

Fig 2-With Cetlin’s intrusion arch (0.018 SS base archwire with sectional 0.019x0.025 SS)

Fig 3-After intrusion

Fig 4- Post treatment with corrected deep bite and anterior marginal discrepancy

Fig 5- Pre treatment radiographs after intrusion

Fig 6- Post treatment radiographs after intrusion

Conclusion

There are several factors that need particular focus in Class 2 division II malocclusions. The upper incisors, being retroclined by forces from the lip morphology, are likely to be extruded. A study by Lapatki ³ found that the upper incisor tips are indeed at a more inferior position in Class 2 division II malocclusions than in Class 1. Intrusion of the incisors is, therefore, likely to be a sensible biomechanical aim.  In some Class II, division 2 malocclusions, the incisors are so severely lingually tipped that the center of resistance (CR) is anterior to the point of force application (PFA). Proclination before intrusion may cause extrusion of the incisors and impaction of their roots on the palatal cortex of the premaxilla. In this biomechanical system, the PFA should be moved in front of the CR. Intrusion with this method is easier and stable.

References

1. Graber, Vanarsdall, Vig- Orthodontics- Current principles and Techniques.  Elsevier Mosby publishers – 4^th Edition: 873-878, 2005.

2. Charles Burstone – Deep overbite reduction by intrusion. Am J Orthod Dentofac Orthop 1977; 72:1-22.

3. Lapatki BG, Mager AS, Schulte-Moenting J and Jonas IE. The importance of the level of the lip line and resting lip pressure in Class II Division 2 malocclusion. Journal of dental research 81: 323-328, 2002.