GETTING STARTED WITH LINGUAL: UNDERSTANDING AND MANAGING YOUR LAB WORK WITH SELF-LIGATING EVOLUTION BRACKETS

Kulbir Singh Goraya
Private Practice,  D-577, Ranjit Avenue, Amritsar-143001, Punjab, India.
Email: ksg577@yahoo.com

www.lingualnews.com, Vol  6 No. 1, August 2008

The objective of this article is to overview the in-office laboratory procedures for indirect bonding of self-ligating lingual brackets, Evolution SLT with its Smart Jig technology (Adenta GmbH, Gilching, Germany) using the Hiro Technique(1,2)

Introduction

Due to increasing popularity of lingual orthodontics in today’s time, many clinicians are incorporating lingual orthodontics in their practices. With the advent of newer materials and technologies and as a result of the refinements and innovations carried out by senior doctors, it has become simpler for the present day practitioners to offer lingual orthodontics to their patients. The lingual technique is more difficult and complex than the labial technique for several reasons, such as, difficulties in bracket positioning, patient discomfort, maintenance of oral hygiene and mechanical difficulties (3). With the use of self–ligating lingual brackets many of these problems can be overcome (3,7).
 
Self-ligating brackets are ligatureless brackets that have an inbuilt mechanical device to close off the bracket slot. Mainly, there are two types of self-ligating brackets: one has a spring clip, which presses against the archwire, and the other has a passive self-ligating clip (4).These brackets have many benefits, such as, reduced friction, improved oral hygiene, no soft tissue laceration and improved full archwire engagement (5). All these features are not only time-saving (6) but also contribute to the efficiency of lingual orthodontic treatment (7).

In order to practice lingual orthodontics, it is important to understand how the case is set-up and how indirect bonding is carried out. There are many options for finding the ideal position of bracket placement on the lingual surfaces of the teeth:
A. T.A.R.G. (11)
B. Ray Set (Biaggini Medical Devices, Viale San Bartolomeo -19126 La Spezia, Italy.)
C. Slot machine (Creekmore Enterprises, Houston, Texas-77079)
D. CLASS (8)
E. LinguSet ( Dentaurum Group, Turnstraße 31, 75228 Ispringen, Germany ), etc.

Furthermore, there have been a couple of inventions like the Hiro Technique (1,2) and the Lingual Bracket Jig (9) that have simplified the laboratory work to an extent that it can be conveniently carried out in one’s own office without incurring much cost. The method described in this article is the “Hiro Technique” using self-ligating lingual brackets, Evolution SLT with its Smart Jig (Adenta GmbH, Gilching, Germany).

Laboratory Work

A. Creating an Ideal Set-up
1. Take PVS impressions of the arches and pour the models with good quality stone. There is no need to make a base at this point.
2. After taking out the casts, cut a small groove at the base of the model conforming to the shape of the arch (Figure 1). This groove will become part of each sectioned tooth (Figure 2- see arrow) and will act as a guide while positioning it back on the set-up base. 
3. Apply separating medium to the model and after it has dried, pour stone in the base former and position the cast in it, ensuring that the cast is centered correctly in the base former.

Figure 1. The groove is visible on the base of the model and        separating medium is being applied to the base of model.

Figure 2. Tooth being sectioned. Arrow indicates the impression of the groove engraved on the sectioned tooth.

4. After the base has set, carefully tease out the model from the base. This base will act as a set-up base (Figure 5- B).

Figure 5. A- Sectioned teeth held together in wax. B- Set-up base.

5. After taking out the model, position it back on the base. Mark the longitudinal axis of the teeth beginning from the incisal edge/cusp tip of the tooth to the bottom of the base.  Also number each tooth for identification and with the diamond disk section teeth into individual units (Figure 2).While sectioning, cut the body of the cast from both the palatal and buccal aspects without touching the contact area. Rest of the sectioning should be completed by putting a sharp instrument in the cut (created by the disc) and applying controlled gentle force laterally. The sectioned teeth should be given proper shape so that when set-up is realized, these units can be easily re-positioned in wax. At this point it is important to ensure that all surfaces of these sectioned teeth are still virgin and intact.

6. Position these sectioned teeth on the previously taken PVS impressions (Figure 3) and pour melted wax over them (Figure 4).

Figure3. Sectioned teeth positioned in the PVS impression.

Figure 4. Sectioned teeth held together in wax in the impression.

7. Once the wax hardens up, carefully take out the sectioned teeth embedded in wax as a single unit (Figure 5- A) from the impression and position it on the set-up base (Figure 5- B). Now seal this assembly on the set-up base, making sure that the previously drawn longitudinal axes of these teeth coincides with the corresponding lines on the base(Figure 6). This will ensure that the sectioned teeth have been positioned correctly on the base.

Figure 5. A- Sectioned teeth held together in wax. B- Set-up base.

Figure 6. Sectioned teeth mounted on the set-up base. Long axes of the teeth are coinciding with the lines on the base.

8. Draw longitudinal axes on the lingual surfaces of the teeth. Also mark horizontal lines across the lingual surfaces of the teeth indicating bracket positioning height. Now complete the ideal set-up (Figure 7) according to the prescription by fulfilling treatment goals and objectives. Depending upon the complexity of the case, the set-up can also be realized on a semi-adjustable articulator.

Figure 7. Final teeth set-up.

B. Indirect bracket positioning of Evolution SLT with the Hiro Technique.

Since morphology of lingual surfaces is irregular and variable it is important to achieve custom contouring and thickness standardization of bracket bases (10) (especially in anterior teeth), by adding the required amount of resin on bracket pads, to fill in the gaps between the bracket pads and the stone model of the teeth. This helps in avoiding several first-order bends in the archwire during the alignment phase (11,12). Indirect bonding is highly recommended for precise customization of bracket bases to help control the in-out, tip, torque and height of brackets.

The “Hiro Technique” is a great invention in indirect bonding because of its inherent simplicity in carrying out the procedure without any expensive, elaborate and technique sensitive equipment. Equally important is the smart jig, an integral part of the Evolution brackets, which has further refined the “Hiro technique” not only in the manner in which the transfer caps are fabricated, but also in the way in which these caps can be disconnected from their respective brackets.

About the Smart Jig

Jigs are of two types: one, for the anterior teeth (Figure15-A, see arrow) and the other, for the posteriors. (Figure15-B, see arrow). Jigs enable us to fabricate single-tooth transfer caps with lot of ease. The role of the Smart Jig is to connect the transfer cap and the bracket together with the help of an elastomeric ligature (Figure 15-C). By simply removing the ligature, the smart jig disconnects from the bracket taking the transfer cap with it. This results in reduced chair-time during the bonding and re-bonding stages because the operator does not have to cut through the resin core in order to separate the transfer cap from the bracket.

Figure 15. A- The Evolution bracket and the Jig for anterior teeth. B- The Evolution bracket and the Jig for posterior teeth. C- The transfer cap-bracket assembly. D- Customized bracket base.

About the Evolution SLT

It is a self-ligating lingual bracket with a spring clip that allows occlusal archwire insertion. The buccal-lingual height of the bracket is 2.1mm (Figure 8).The bracket can be opened and closed with a modified scaler, or a special opening instrument. The spring clips are designed as bite planes for lower incisors and have a safety release feature built into them. Any force in excess of 600 grams applied to the bracket, will cause the clip to open, thereby releasing the archwire out of the slot.

Figure 8. Adenta’s Evolution bracket.

Procedure

1. Bend .018x.025 stainless steel wire (full slot) conforming to the lingual shape of the arch. This wire should be bent accurately by making a small curve for anterior segment. Mark midline on the wire and also mark in-between the canine and premolar. While bending the wire, it is important not to introduce any torque, tip or any other bend in the wire except for the offset bend in the canine and premolar area or if required, in between the second bicuspid and molar area (Figure 9).

Figure 9. .018x.025 SS ideal archwire.

2. Place Evolution brackets on the ideal arch wire and close their spring clips in order to secure these on to the wire. Now position this assembly on the model (Figure 10). At this point, only some part of bracket bases will be touching the palatal surfaces of the teeth (Figure 11). Later on, the remaining space will be filled in by applying resin to the bracket base in order to set the desired torque, in-out and rotations.

Figure 10. The Evolution brackets secured on to the full slot .018x.025 SS ideal archwire on the model.

Figure 11. The uneven gaps between the bracket pads and the lingual surfaces of the teeth are clearly visible.

3. Put “jigs” in the brackets [with the wire secured in the slots] and secure these to the brackets with elastomeric ligature (Figure 12). Now bend jigs over the teeth going from lingual to labial. While bending, care should be taken in keeping the minimal gap between the jig and the tooth surface (Figure 12-see arrow) so that a minimum amount of resin material is used in fabricating individual-tooth transfer caps.

Figure 12. The jigs are secured on the archwire-bracket assembly with an elastomeric ligature and one of the jigs is bent.

4. Apply a coat of separating liquid to the teeth on the cast and allow the separator to dry before proceeding any further. This will not only prevent the pencil marks from transferring on to the transfer caps /customized bracket bases, but will also facilitate easy separation of transfer caps / customized bases from the indirect bonding model. Drying the separating medium can be hastened by placing the model in a microwave oven for 15 seconds (13). Now position the assembly on the model and put some light cure adhesive at the rear end of the wire and model in the molar area. Secure this assembly on the model by light curing the orthodontic adhesive (Figure13).

Figure 13. .018x.025 SS ideal archwire is held in place on the model by light curing the band cementing cement in the molar area.

5. Fabricate single-tooth transfer caps with light cure Tiger Bond Band Cement (Class One Orthodontics, Lubbock, TX 79414) by putting material onto each jig and tooth in the incisal/occlusal area and some part of the labial surface. Avoid putting any material on the brackets and on the vestibular surfaces of the posterior teeth. In order to help identify transfer caps, it is recommended to write tooth number on each cap (Figure 15-C).Light cure the cement in order to complete the ‘transfer cap’ fabrication process (Figure 14). These caps are sufficiently rigid and stable to reliably accomplish the bonding and re-bonding procedures. At this stage, it is important to note that customization of bracket pads is still pending, i.e., the gaps between the bracket bases and the lingual surfaces of the stone model of teeth still exist.

 6. Once the transfer caps are fabricated, gently separate the whole assembly from the model. Remove each elastomeric ligature to separate the transfer cap-jig combination from the bracket and the wire.

7. Now release the wire from the brackets by opening their spring clips.

Figure 14. Fabrication of single-tooth transfer caps on the indirect bonding model.

8. Re-attach each bracket to its corresponding transfer cap-jig assembly with the help of an elastomeric ligature (Figure 15-C).

Fig 15 C- The transfer cap-bracket assembly.

9. A small amount of light cure orthodontic adhesive like Enlight (Ormco Corporation, 1717 West Collins Ave; Orange, CA 92867) is put onto bracket bases (Figure16), and the transfer caps carrying the brackets are positioned back on the corresponding stone model of the teeth (Figure 17). Excess material around the brackets is cleaned before light curing them for 20 seconds depending upon the intensity of the light curing unit. This results in precise customization of bracket bases (Figure 15-D) that compensates for the irregular and variable morphology of lingual surfaces of the teeth.

Figure 16. Orthodontic adhesive is being applied to the bracket base prior to its customization.

Figure17. After the orthodontic adhesive application to the bracket pads, transfer caps carrying these brackets are re-positioned on the model in order to customize their bracket bases.

10. Microetch the customized bases with a Microetcher (Trade mark of Danville Engineering, CA.), using 50Micron Aluminium Oxide for 2-3 seconds to increase the surface area of the base for proper bonding (14). Be sure to clean the customized base with soap and water (15) as leaving powder on the base will weaken the bond strength (16). While Microetching, due care must be taken in containing the sand blasting debris, using sandblasting chamber, etc (17). The appliance is now ready for bonding. The operator is free to use either the light cure composite or the self cure type while bonding the brackets to the patient’s teeth. A modified Hiro system can also be used for indirect bonding as recommended by Adenta in which customization of bracket bases is done prior to fabricating the transfer caps.

Conclusions

1. Using the “Hiro technique” with Evolution brackets and smart jigs, enables the operator to carry out indirect bonding from fabricating single–tooth transfer caps to customization of bracket bases in a simple, quick, accurate and economical way.

2. Transfer caps fabricated with the help of smart jigs may result in reduced chair-time during the bonding and re- bonding stages, as the operator doesn’t have to cut through the resin core in order to separate the transfer cap from the bracket.

3. Apart from creating customized bracket bases, .018x.025 stainless steel ideal archwire can also serve as a template for all archwires that are going to be used during the entire treatment.

Acknowledgement

The author would like to thank Dr. Alfredo Gilbert Reisman for introducing him to this technique.

References

1. Hiro by Dr. Toshiaki Hiro. U.S. Patent No. 6,174,163. Jan.16, 2001.
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5. Shivpuja PK, Berger J. A comparative study of conventional ligation and self-ligation bracket systems. Am J Orthod Dentofacial Orthop. 1994;106(5): 472-480.
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10. Scholz RP, Swartz ML. Lingual Orthodontics: A Status Report. Part 3: Indirect Bonding –Laboratory and Clinical Procedures. J Clin Orthod. 1982; 16(12): 812-820.
11. Fillion D. The Thickness Measurement System with the DALI Program.In:Romano R, editors. Lingual Orthodontics. Hamilton, Ontario: BC Decker; 1998. P.175-184.
12. Smith JR, Gorman JC, et al .Keys to Success in Lingual Therapy- Part 1. J Clin Orthod 1986; 20(4): 252-261.
13. Hilgers James J. Getting That Indirect Bonding Monster Off Your Back ..or Indirect Bonding Made Easy. Clin Impress; 2(3):6-10.
14. Gange P. Interviews : Paul Gange on the Present State of Bonding. J Clin Orthod. 1995; XXIX (7): 429-436.
15. Geron S. In-office bracket positioning of different Lingual brackets with the new Lingual Bracket Jig [LBJ]. 4(1) http://www.lingualnews.com; 2006.
16. White L. A New Look at Indirect Bonding. Cyber Journal Of Orthodontics. Available from URL: http://www.oc-j.com/sept02/White.htm; 2002.
17. Zimring JF. Pearls: Controlling Sandblasting Debris. J Clin. Orthod.1997; XXXI (2): 105-105.

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Adult and Lingual Orthodontics
EDITORS:
Dr. Silvia Geron D.M.D., M.Sc
Dr. Rafi Romano D.M.D., M.Sc
Dr. Pablo Echarri D.M.D., M.Sc