LINGUAL TECHNIQUE -   ARIMA'S TRANSFERRING MASTER MOLD

Dr. Valter Ossamu Arima, specialist in orthodontics.
Dr. Neusa Emiko Arima, dental surgeon; coordinator of the lingual laboratory. ( Co-Author)
Dr. Luiz Fernando Eto, specialist and master of orthodontics by PUC-Minas; Prof. in orthodontics specialization course by University and Univale (MG); Abol Chairman. Co-Author)

Key words:
Lingual orthodontics. Set up models. Transferring mold.

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

Abstract

Fabricating molds for indirect bonding in lingual orthodontics which will allow the transference of the bracket to the patient has been a concern for those professionals who choose to make them in their own laboratories. The precision of this transference might be one of the most critical aspects of indirect bonding and it will certainly influence the quality of the results. Various authors have described a number of approaches to make these molds. This article shows a fast and precise system for indirect bonding.

INTRODUCTION

Arima’s transferring mold was developed in order to attain more rapidness and precision in indirect bonding since its main purpose is to correctly position the brackets once anatomical irregularities of lingual face have been counterbalanced, e.g. bonding height, angulation, torque, in/out in the bracket bases. Transference must be as precise as possible so as to avoid any displacement or modification of the material.

MATERIAL AND METHOD

 The monocomponent and light curing material employed in fabricating the Arima’s transferring mold was Bosworth’s Fastray LC acrylic resin. The product is supplied in boxes containing either 12 or 50 sheets of approximately 1,5 millimeter, which come in white or blue, and which are recommended for making individual molds. It will not stick to the model neither will it distort after polymerization. It may be used on patients allergic to monomers. Light curing through physical medium takes place within 20 to 40 seconds. Figures 1A, 1B and 1C show what the Fastray LC acrylic resin looks like. 
 

Figs. 1 A, B, C 

In order to use the Arima’s transferring mold, set-up models with lingual brackets properly positioned should be used. Fig. 2 shows a set-up model put together using the Hiro System, with the brackets already positioned in the lingual surface of the teeth.

FABRICATING ARIMA’S TRANSFERRING MOLD

When the set of brackets and tubes are properly positioned with the pads, the ideal arch is removed. FIG. 3 A, B.
Metallic positioners are used as a bonding element, conferring more precision between the adjustment of the mold and the position of the bracket on the lingual surface of the tooth.
 These positioners are made with .018-inch x .025-inch steel wire which have specific measures for each group of teeth. The postitioners are U-shaped slots with horizontal insertion of 90o angles. However, in the case of the second molars, closed tubes prevent the horizontal insertion of the wire; thus an inverted Y-shaped distal-mesial insertion is necessary.

It has been agreed that, in the case of the U-shaped positioner, the shorter side will always face the mesial region in order to make it easier to tell them apart after they are removed from the patient’s mouth and placed in the molds. FIG.4.

Fig. 4

The metal positioners, held by elastic modules, are inserted in the bracket slots so that they can receive the photopolymerizable acrylic resin. FIG. 5 A,B. 
The mesial-distal distance of the bracket’s slot should be measured so that the width of the metallic positioner can be determined. This will prevent the mesial-distal dislocation of the bracket over the wire. In order to bond the elastic module, 0,5 millimeter should be added to the distance obtained. Displayed below is a table with numbers obtained from Ormco brackets (7th generation) by using a digital paquimeter.

Fig. 5A

Fig. 5B

The mesial-distal distance of the bracket’s slot should be measured so that the width of the metallic positioner can be determined. This will prevent the mesial-distal dislocation of the bracket over the wire. In order to bond the elastic module, 0,5 millimeter should be added to the distance obtained. Displayed below is a table with numbers obtained from Ormco brackets (7th generation) by using a digital paquimeter.

ORMCO’S BRACKETS	mm	MEASUREMENT        OF POSITIONERS
Upper central incisors	2,50	3,0
Upper lateral incisors	2,30	2,8
Upper canines	2,50	3,0
Upper/ lower pre-molars	2,60	3,1
Convertible upper/lower first molars	4,0	4,5
Upper/lower second molars Hinge Cap	5,0	5,5
Single tube	3,5	4,0
Lower incisors	2,0	2,5
Lower canines	2,0	2,5

Measurement of bracket and metallic positioner of an upper central incisor. FIG.6 A, B.  (Below)

Resin sheets should be trimmed according to the mesial-distal width of the teeth so that the Arima’s mold can be made. FIG. 7A, B e C.

Fig. 7A

Fig. 7B

Fig. 7C

Once the models have been isolated and the metallic positioners inserted in the bracket slots, the resin should cover the buccal, occlusal/incisal surface of the teeth, and it should be pressed against the brackets for good adjustment. Next, the resin sheet should be cured. Anterior region. FIG.8A. Posterior region Fig. 8B

Fig. 8A

Fig. 8B

The whole set is carefully removed (Fastray resin, .018 x .025-inch wire and the bracket) and, once again, it should be cured, including the internal part and the pads so that a thorough polymerization is guaranteed. Proximal areas should be trimmed with a low-speed multifaceted drill so that they will not interfere during bonding to the patient’s teeth. FIG. 9 A, B.

Fig. 9A

Fig. 9B

In the internal region of the Arima’s transferring mold, close to the bracket in the incisal edge, a relief area should be created with a spherical low-speed steel drill in order to allow flowing of any resin excess. FIG. 10

Once the relief areas have been created, it is necessary to spray the pads with aluminum oxide at 50 micra; next, a thin layer of anti-adherent should be applied throughout the internal part of the individual mold so that, when it is removed from the tooth, it will not stick. FIG. 11 A and B.

A view of the Arima’s transferring mold with the brackets – internal view, lateral view and a view without the brackets, but with the positioners.        FIG. 12 A,B,C.

CLINICAL INDIRECT BONDING USING THE ARIMA’S TRANSFERRING MOLD

Once the prophylactic procedures and acid-etching have been taken care of, the brackets are individually bonded. After the mold is set in position, the resin excess should be removed before light curing. Next, we remove the Fastray resin from the positioner and the tooth. FIG. 13A. Using a heated probe, we cut the elastic module and later remove the metallic positioner. FIG. 13B.
 

Figures 14 A and B (below) show all the brackets duly bonded and with the first arch.

CONCLUSION

Due to the critical role in the indirect bonding procedures, laboratory work should be carried out observing precise procedures that follow the plan established by the orthodontist. The material used to make the transferring molds should be of high quality, i.e. material that will not deform during bonding, and that proves to be firm, easy to manipulate and cure. 
This technique allows re-utilization of the mold for sporadic re-bonding of brackets at the same time it offers enormous precision in the original positioning of the bracket. 
The precision and the lesser time to transfer the brackets from the set up models to the patient’s mouth makes up for the extra time the orthodontist might spend on laboratory work.

BIBLIOGRAPHICAL REFERENCES

1. ECHARRI,P.  Ortodoncia Lingual. p. 115-142.
2. ROMANO, R. Lingual Orthodontics.1998; p.163-173.
3. TAKEMOTO,K. ; GIUSEPPE S. Invisible Orthodontics. Quintessenz-Verl 2003; p.39- 45            
   
Dr. Valter Ossamu Arima, specialist in orthodontics. ( Author)
Dr. Neusa Emiko Arima, dental surgeon; coordinator of the lingual laboratory. ( Co-Author)
Dr. Luiz Fernando Eto, specialist and master of orthodontics by PUC-Minas; Prof. in orthodontics specialization course by University and Univale (MG); Abol Chairman.(Co-Author)

Contact address 
Valter Ossamu Arima
Av. President Kennedy, 246. Rebouças.
Zip Code: 80.220.200 Curitiba-Paraná-Brazil.
E-mail: valter@onda.com.br

www.lingualnews.com
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