Objectives

Materials and Methods

Results

Conclusion

KeyWords

Rectangular Wires as substitutes for the MAA and a Torquing Auxiliary in the Begg treatment -An Experimental study

Authors:

Tejashri Pradhan, MDS Associate Professor Department of Orthodontics and Dentofacial Orthopedics, Tatyasaheb Kore Dental College and Research Centre, New Pargaon - 4161 37 Maharashtra, India e-mail: tejashripradhan@hotmail.com Phone: 9960511 444

Vijay Jayade, MDS Former Professor and HOD, Department of Orthodontics and Dentofacial Orthopedics SD.M. College of Dental Sciences, Dharwad, Presently Professor Emeritus, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India

1. To measure and compare the torquing action of different rectangular wires with those of the MAA and a four spur auxiliary. 2. To select or recommend ideal rectangular wires for different torque requirements in the Begg technique.

An experimental set up consisting of an upper typodont with ivorine teeth was employed. It was fitted with the Begg brackets. Rectangular wire sectionals in 0.016"x 0.022", 0.017" x 0.025", 0.018" x 0.025" and 019" x 0.025" sizes and made of Stainless Steel, Braided Stainless Steel, Superelastic NiTi, Braided NiTi, Copper NiTi, a -Titanium and B- Titanium were tested. The MAA and the four spur torquing auxiliary were made in 0.009" supreme grade and 0.012" premium plus grade wires respectively. Torquing forces generated by the above wi res inserted in the ribbon mode and the auxiliaries were accurately measured using a dial gauge and components of an electric circuit. Force comparisons were drawn to find out if forces generated by any\of the rectangular sectionals were comparable with those generated by the MAA and the four spur torquing auxiliar.

1. Forces were higher when rectangular wires were engaged first rather than piggyback. 2. Torquing effects of braided NiTi sectionals in 0.025" x 0.Q17" size engaged before the basewire are comparable with the MAA. 3. Torquing effects of braided stainless steel sectional in 0.025" x 0.017" size and Superelastic Niti sectional in 0.025" x 0.017" size engaged before the base wire are comparable to those of the four spur auxiliary.

Appropriate rectangular sectionals can be effectively substituted for the MAA or the four spur torquing auxiliary.

Controlled tipping, torque, Rectangular sectionals, MAA and four spur auxiliary.

INTRODUCTION a decline now, it is still practiced by many orthodontists in India and in some other countries.

The li ght wire tec hnique was introduced to the profession by Dr. P. R. Begg in 1954. It soon became immensely popular because of some original ideas, especia ll y the appli cation of light forces. Although on

7

However, the present day Begg practi ce differs from the traditional Beggl as it aims to overcome many of the drawbacks of the latter. One such major difference

relates to bio-mechanica l considerations. The Classica l Bcgg treatment consisted of uncontrolled tipping during the firs t two stages and root movements in the third stage. One the other hand, the current emphas is is on contro lled tipping in the initial stages, since it makes the overa ll treatment more efficient mechanics-w ise and also minimizes possibi lity of root resorption.

Mol lenhauer's2 aligning auxi liary (popu larly ca lled as thc "MAA") has been incorporated in the modern refi ned Begg practi ce for control led labio- l ingual tipping of the anteriors during the fi rst and second stages of treatment. MAA, besides aligning, also exerts ultra light torquing and uprighting forces on the anterior tceth. The gentle torquing effect does not appreciably deepen the bi te nor tax the anchorage. Thi s is accomplished by usi ng a stiff base w ire in the 0.018" premium plus grade, in combination w ith very gentle root movi ng forces from the MAA made in ultra light 0.009" supreme grade wi re.

Idea llabio-l ingual incli nations of the teeth at the finish of appliance therapy are very important for obtaining stable results. The Begg torquing auxil iary (usuall y having four spurs, sometimes two spurs) used in the III stage provides opt imum force to improve the ax ial inclination of the anterior teeth . The des ired max illary and mandibu lar incisor inclinations, th rough their interincisa l angle, not only increase the posttreatment stabi l ity but also enhance dental and facia l esthetics. However, the time and skill involved in fabri cati ng the torquing auxiliaries or the MAA puts off many operators from employing them, thus affecti ng the quality of their treatmen t results.

Therefore it was fe lt that there was a need to explore substi tute components which could be ei ther obtained preformed or fabricated easily, and which would serve, equall y efficiently, the same purpose as of a torquing auxi l iary or the MAA.

A rectangular w ire bent along its narrow dimension (i.c. in the edgewise mode) in the form of an arc of a c ircle but engaged in ri bbon mode in Begg brackets acts like a torquing auxiliary. Usi ng modern wi res such as NiTi, Cu NiTi, rectangular braided stai nless steel, rectangular braided NiTi w ire etc, it should be possible to develop torqu ing forces ranging from ultra l ight to l igh t range, to establish equiva lence between certain rectangu lar w ires on one hand and the MAA and torquing auxiliary on the other. This study was designed to eva luate the torquing action of different rectangular wires and help in selecting the appropriate rectangular w irc for a given cl in ica l situation.

8

MATERIALS AND METHODS The study was ca rri ed out at the Department of O rthodontics, S.D .M . Co llege of Dental Sc iences, Dharwad. It consisted of an experimental comparison of d i fferent rectangular w ires w ith the MAA and torquing auxiliary. A pilot study was undertaken, which indicated that it is possible to use for root movements a rectangular w ire bent in the form of an arc in the edgewi se mode (a long the narrow dimension) but engaged in the ribbon mode.

Materials I) The rectangular wi res tested were (Fi g 1)

Figure 1 : Armamentarium

a) 0.016" x 0.022" and 0.017" x 0.025" Stainless Steel

h) 0.016" x 0.022", 0.01 7" x 0.025", 0.018" x 0.025" and 0.019"x 0.025"Braided Stain less Steel

c) 0.01 6" x 0.022", 0.01 7" x 0.025", 0.018" x 0.025" and 0.019"x 0.025" Super elastic N iti

d) 0.01 7" x 0.025" Braided Ni ti

e) 0.01 7" x 0.025" and 0.019"x 0.025" Copper Niti (35°C)

f) 0.018" x 0.022" a- Titanium

g) 0.01 7" x 0.025" and 0.019"x 0.025" B- Titanium

(All the above were tested in ribbon mode, although the dimensions mentioned are in the edgewise mode, since it is the way they are commonly designated)

h) 0.022" x 0.018" N iTi Torque Bar (TP Lab3)

II) The MAA was made of 0.009" supreme wi re and the torquing auxi liary was made of 0.012" premium plus w ire (A.J. Wi lcock Co. Australi a).

Methodology The methodology was adopted from M.Hammond and W.P.Rock's4 method. The basis of this experiment was an upper typodont (Fig 2) in which ivorine teeth were

Figure 2 : Typodont

fixed. The roots of the six anterior teeth were allowed free antero-posteri or movement by trimming the lab ial and lingual wa lls of the acrylic sockets. Begg brackets were fi xed to the teeth. Roots of the anterior teeth were built up with acrylic and screws were inserted in the apica l area. The teeth were aligned to idea l arch form so as to ensure that the brackets were correctly positioned. A 0.020" premium wire was used for making the base arch wi re. The test jaw was mounted on a wooden frame. A dial gauge was fixed to a metal post fitted on the same base (Fig 3).

Figure 3 : Experimental set-up

The indicator arm of the gauge was suspended verti ca lly so that forces from the horizontal movement of the root ap ices could be read on the dial gauge.

Electrica l Ci rcuit

A thin copper conducting plate of 3mm width extending over the six anterior teeth, was fi xed over the acrylic

9

1;"",,----= = =---= .=:: - ---- - - -

on the labia l aspect. This plate had small vertical projections extending ap ica lly in the area of incisors. Each of the four inc isor roots also ca rri ed copper conducting plates fitted at the level of the verti ca l projections. One end of an electri ca l wire was soldered to the labial conduct ing plate, and its other end was connected to a battery cell. Another w ire connected from the battery cell to a bulb formed one part of the circuit .Each of the conducting points on the four incisor roots also had pieces of electri ca l w ires soldered on them. Th e other ends of th ese wires co uld be indiv iduall y connected (depending on the tooth on which force measurement was made) to an electri ca l w ire. The other end of this wire was connected to the bulb, thus completi ng the other part of the circuit (Fig 4). All the way through the experiment, the two

Figure 4 : Electrical Circuit

conducting points were maintained in a constant position.

Rectangular sectionals were cut from anterior part of preformed lower archw ires (in the di fferent sizes and made from different materials as mentioned above) with the curvatures maintained at the original preformed arc. These were engaged in the brackets in two different ways (as described below) and force measurements were taken.

A. At the beginning, the rectangular sectional wire that was being tested was engaged in the Begg brackets, and the base w ire was fixed piggyback over the rectangular wire (Fig 5). The two wires were tied into

Figure 5 : Rectangular wire bent in edge wise mode but engaged in ribbon mode torque.

the bracket with a ligature wi re. Thi s allowed lingual root torque to fully mani fest itself (Fig 6). At this point,

..• -~ ~."

:" j 1-~" .l .. ' .. ,-_ .. ,,*, , 4h.~~. "t ~ ,

Figure 6 : Rectangular wire engaged before the base wire, and palatal root allowed to manifest.

a thread was tied between the screw at the api ca l area of one of the four incisors and the dial gauge arm (with dial gauge at zero position as seen in Fig 7) . The thread

Figure 7 : Thread tied at the root apex, and Dial gauge maintained in '0' position.

was pulled away from the lingually inclined position till the contact occurred at the two conducting points and the light glowed (Fig 8). The pulling force required for the light to glow was read at this juncture. An average of three readings was taken. The procedure was repeated for all four incisors, employing various rectangular sectionals

B. For all the rectangular sectionals, another set of readings was taken by engaging them piggyback over the main wire. The MAA, torquing auxi liary and the torque bar were always engaged piggyback over the base wire.

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Figure B : Thread pulled from torqued to pre torqued postion completing the circuit, and the reading taken.

Thus the forces were measured at the root apex. The readings for different rectangular w ires were directl y compared with those of MAA (Fig 9), four spur auxiliary (fig 10) and TP Niti Torque Bar.

Figure 9 : Mollenhauer's Aligning Auxiliary IMAAJ.

, ".

j , .. ~J ~,~, _ . ' t •• -.

~. f '''l. ;.~ .. ~ .. . t,.\".!A HI,t ..... '-....a..... •

Figure 10 : Four spur auxiliary.

RESULTS Table No. I : Forces generated in grams by the rectangular wi res engaged before the base w ire

DIAMETER R. LATERAL R. CENTRAL L. CENTRAL L. LATERAL

OFTHEWIRE ROOT ROOT ROOT ROOT

Stainless Stee l

0.022"x 0.016" 18 20.5 19.5 18

0.025"x 0.01 7" 20 26 25.5 20

Braided

Stai nless Stee l

0.022"x 0.016" 11.5 14 14 11 .5

0.025"x 0.01 7" 14.5 16.5 16 13.5

0.025"x 0.018" 1 5 18 18 15

0.025"x 0.01 9" 16 19.5 20 16

NiTi

O.022"x 0.01 6" 11 14 14 11

0.025"x 0.01 7" 12.5 16 16 12.5

0.025"x 0.018" 14 18.5 18 14

0.025"x 0.01 9" 16.5 20 19.5 16.5

Braided Niti

0.025"x 0.01 7" 10.5 12.5 12 10

Cu-N iTi

0.025"x 0.01 7" 12.5 16 16.5 12.5

0.025"x 0.019" 15.5 18.5 18 15.5

a - Titanium

0.025"x 0.018" 16 17.5 18 15.5

& - Titanium

0.025"x 0.01 7" 12.5 15.5 15 12.5

0.025"x 0.01 9" 15.3 19 20 16

N.B. The force va lues equivalent to those of MAA are pri nted in bo ld font, and to those of four spur torquing auxiliary are underlined.

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Table No. II. forces generated in grams by rectangular wires engaged piggy back and also the MAA, torquing

auxiliary and the torque bar.

DIAMETER R. LATERAL R. CENTRAL l. CENTRAL l. LATERAL

Of THE WIRE ROOT ROOT ROOT ROOT

Sta inless Steel

0.022"x 0.016" 16.5 20 19 16 0.025"x 0.Q17" 18.5 21 21.5 18 Braidcd

Stain less Steel

0.022"x 0.016" 11 12.5 12 11.5

0.025"x 0.017" 11 .5 13.5 14 11 .5 0.025"x 0.018" 12.5 15 15 12

0.025"x 0.019" 14 17 17.5 14

NiTi

0.022"x 0.016" 9.5 12 12.5 10 0.025"x 0.017" 10.5 13.5 13 1 0.5

0.025"x 0.018" 11 .5 1 5.5 15.5 11 .5

0.025"x 0.Q19" 13 17 16.5 12.5

Braided Niti

0.025"x 0.017" 7.5 10 10 7.5

Cu- NiTi

0.025"x 0.017" 11 12.5 13 11.5

0.025"x 0.019" 13 16.5 16 13

a - Titanium

0.025"x 0.018" 13.5 15 16 13.5

P -Titanium

0.025"x 0.017" 11 13 12.5 11

0.025"x 0.019" 11.5 14 13 12

Four spur 0.012" P + 14.5 16.5 17.5 15

MAA 0.009" Sup 11 13 12.5 11

Torque Bar 0.022"xO.018" 11.5 14 13 12 ..

N.B The force values equivalent to those of MAA are prmted m bold font, and to those of four spur torqumg auxiliary are underlined.

DISCUSSION

Mechanism of root movement and controlled tipping in the Begg technique

Dr Julie Ann Staggers' rightly pointed out that uncontrolled tipping fo llowed by root movement is not an efficient method of retraction. As already mentioned, the emphasis of refined Begg is on contro lled tipping followed by root movement. She also raised a doubt whether the MlF ratio of approx imately 12:1, required for root movements, could be obtai ned in the Begg tcchnique. The explanation provided below wi ll show how the required MlF ratios both for root movement and controlled tipping are obtained in the refi ned Begg.

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The four spur auxiliary for lingual root torque in third stage, which is commonly used at present, is the one made in 0.012"premium plus wi re. Although the forces produced by this auxi l ia ry are low, the moments generated by them are adequate. Thi s is because the moment arm is much greater in a torquing auxiliary than in a rectangular arch wi re twisted for torquing effect, as was pointed out by Nikolai' (Diagram 1).

When the moment produced by the torquing auxi liary acts in conjunction w ith light CI II elastics, the MlF ratio is close to the requ ired 12 :1 mm for controlled root movement in the lingual direction.

~, ~..,.'

,.,. ' . , .... w·J.1·~

Diagram 1

The Class II elastic force, acting alone on the upper anterior teeth, would cause their uncontrolled tipping in crown lingual root labia l fashion (as in Diagram 2A). The intrusive force in the archwire would resist this tipping by providing a counter-moment (Diagram 26). The couple generated by the MAA augments thi s counter-moment (Diagram 2C). Depending on the ratio of combined counter-moments to the magnitude of CI II force, a M/F ratio of about 8 :1 as required for contro lled tipping could be provided . To obta in satisfactory M/F ratio in II stage, MAA should be cont inued till the end of the II stage. Thi s prevents undesirable uncontrolled lab ial tipping of incisor roots, and therefore shortens the III stage.

Rationale for testing various wires We thought of testing w ires of different dimensions and different physical properti es based on composi ti on, as we had to select wires w hich would generate forces comparable to those of two mechanisms namely,

1) Lighter forces exerted by the MAA, and

2) Stronger forces equivalent to that of a torquing auxiliary

Methodology The method used in this study was aimed at measuring the forces exerted by torquing elements at the root apex. The present study differed somewhat from the original study of Hammond and Rock' as well as an earli er study conducted by Dr Anuradha Sooda' in our Department on different designs of torqu ing aux iliaries, wherein the forces were measured at the bracket level. As the moment arm of the torqu ing spur is sufficiently long, it is possible to lift the spur and measure the force at the spur tip. On the other hand, the moment arm in the case of rectangular wire, is too short to lift similar to a torquing spur. Therefore, we made a slight modifi cation from the previous studies, based on the analysis provided by Hammond and Rock', for measuring forces exerted by torquing elements at the root apex.

13

A

02

0 1

B

Diagram 2

F2

c

Diagram 3 The lever system represented by a torquing auxiliary

As shown in the above diagram 3 by Hammond and Rock4, there is defin ite proportional ity between the force exerted at the crown level by any torquing element and the force experienced at the root apex level, which is expressed as

FXD=FXD

Since it was not poss ible to directly measure the forces forming the couple that generated from rectangular wi re-bracket relatio nship at the c rown leve l, we dec ided to measure the forces experienced at the roots apex level required for pulling the roots from their full y torqued position to the pretorqued posi tion .This was done for all rectangular wires, as also for the MAA made of 0 .009" supreme w ire and the four spur torquing aux iliary made in 0.012"premium plus w ire. Thus a direct comparison was possible.

Forces measured were a combination of the actual force experienced at the root apex plus the force required to overcome friction between the root and the mesia l and distal aspect of the socket wa lls. A formula was devised to estimate these two forces as close to the actual va lues as possible. The derivation of the formul a is explained in the appendix.

Interpretation of the Results

1) The amo unt of fo rce produced increased progressively from a sma ller cross-section of the wire to that of a higher cross section, as wou ld be expected.

2) Forces produced are always more when rectangular wi res are engaged first rather than piggyback. (D iag 4). This could be beca use a portion of the rectangu lar wire projects beyond the bracket slot when it is engaged piggyback, as shown in diagram no. 4.

'-v _ Diagram 4 Rectangular wire engaged before and

engaged piggyback

31 The magnitude of force varied from material to material. Highest forces were produced by Stainless Steel and the least forces were produced by the braided Niti wires.

4) Comparison of the va lues of rectangular wi res and the MAA or th e four spur aux ili ary o n the experimental set up

a) The forces generated by 0.02S"x 0.01 7" braided NiTi engaged before the base wi re and 0.02S"x 0.017" braided stain less steel, 0.02S"x 0.017"a­titanium and 0.02S"x 0.017" Cu-NiTi engaged piggyback are comparable w ith the MAA (0.009" supreme).

b) The wi res which generate higher forces than the MAA but lesser forces than the four spur auxiliary are 0.022" x 0.016" braided stainless steel and 0.022" x 0.016" super elastic Niti engaged before the base wire; as also 0.02S"x 0.018" braided stain less steel and 0.02S"x 0.018" super elastic N iTi engaged piggyback over the base wi re. Th ese cou ld be used as braking mechanism during the second stage.

cl Forces generated by 0.02S"x 0.01 7" braided stainless steel, 0.02S"x 0.017" Super elastic Niti, 0.022"x 0.018" a-titanium and 0.02S"x 0.017" Cu-N iti engaged before the base w ire and 0.02S"x 0.019" Super elasti c Niti , 0.02S"x 0.019" braided stain less steel and 0.02S"x 0.019" Cu-NiTi and 0.02S"x 0.019" B- titanium engaged piggyback are comparable w ith the four

14

spur auxil ia ry (0.01 2"premium plus ) as seen in the tables I & II .

d) Forces produced by rectangular stain less steel wi res were 10und to be much higher than the forces exerted by the four spur torquing auxi liary.

e) Forces produced by the braided NiTi and Super elasti c Niti were constant over time.

SUMMARY AND CONCLUSIONS The forces exerted by certain sectional rectangular wires (which had a curvature along the narrow dimension i.e. in an edgewise mode; but were engaged in the ribbon model were compared to those from the MAA and the four spur torquing auxiliary on the same experimental set up. The results were as follows:

Forces produced by stainless steel wires were found to be the highest followed by braided stain less steel, super elasti c Niti, a-titanium, Cu NiTi , and B­titanium.

2 Forces produced are always slightly higher when rectangular w ires are engaged first rather than piggyback.

3 Forces generated by 0.02S"x 0.017" braided NiTi engaged before the base wire are comparable with those from MAA (0.009" supreme)

4 Forces generated by 0.02S"x 0.01 7"braided stainless steel and 0.02S"x 0.o17"Super elastic Niti, engaged before the base w ire are comparab le with the four spur auxiliary (0.01 2"premium pl us)

Hence, the 0.025" x 0.017"braided NiTi wi re ("Turbo" w ire of Mis Ormco) is efficient in bringing about contro lled tipping in the initial stages and 0.025" x 0.017" braided stainless steel is a usefu l substitute for the four spur torquing auxiliary in the third stage of Begg mechanics.

REFERENCES

1. Begg P R, Kesling P C. Begg Orthodontic theory and technique. 2nd ed.Phiiadelphia: W.B. Saunders Company 1971.p130-139.

2. Mollenhauer B. An aligning auxiliary for ribbon arch brackets: rectangular boxes from ultra fi ne high tensile wires. Aust Orthod J 1990; 11 :219-226.

3. T P Orthodontics Catalog. 1990: Product no. 343-101,95.

4. Hammond M , Rock W P. Forces produced by auxiliary torqu ing springs in Begg technique. Br J Orthod 1991; 18 : 219-223.

5. Staggers lui ie and German e Nicholas. Clinical considerations in the use of retract ion mechanics. Clin Orthod 199 1; XXV: 364-369

6. Nikolai R I. Bioengineering analysis of orthodontic mechanics.2nd ed. Phil adelphia: Lea & Febiger. 1985.307-308.

7. Sooda Anuradha. Evaluation of forces in all three planes produced by torquing auxiliaries of various d es igns m ad e from different di am eter w ires.Dissertation submitted to Karnatak University, 1997; 5-7 and 20.

APPENDIX

The M/F rat io for controll ed tipping should be approx imately liz of that for root movement. Since the class II elastics used in different stages usuall y remain the same throughout the treatment, it wou ld mean that the moment produced by the MAA (MM) in the initial stages should be approx imately one half in magnitude of the moment produced by the torquing auxiliary (MT) in the third stage. As the moment arm (box height in the MAA and torquing spur length) is kept at Smm for both, this would further mean that the forces measured for the MAA (FM) should be approximately one half the forces measured for the torquing auxiliary (FT) as deducted below :

M = F x 0 and M = F x 0 "'I M T T

o is same .i.e. 5mm in both the cases . Since M should be liz of M , F must be liz of F . "

T M T

Such a relationship was observed in an earlier study . 7

carn ed out by Dr. Anuradha Sooda . In the present study such a relationship was not observed. (The force measured for the torquing auxiliary on the central incisor is approx imately 17gms,while that from MAA on the same tooth is 13gms as can be seen from Table no 1I ).The difference in the two studies is expla ined below:

The force noted at the apex is a combination of the force experienced from the torquing element plus the frict ional resistance created by the contact of the root aga inst the wa ll of acry liC socket. In the previous experiments, force for lifting the spurs away from the tooth surface was directl y measured. Therefore friction did not play any appreciable role.

The apparent discrepancy is resolved using the equation given by Hammond and Rock', which is furth er elaborated as under:

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F2

D2

DI

Diagram 6 The lever system represented by torquing auxiliary

F x O=F x O , 2

If we term the force measured at the apex as A and the frictional resistance as R,

F = A - R. 2

Further 01 in both the experimental setups is 5 mm and 02 is approximately 1Smm. Substituting these va lues, the derivation is as follows:

o x F = 0 x (A - R). I , 2

SXF, Therefore ~ = A-R,

O ,XF, Therefore 0 = A-R

2

Therefore R =A - 1/3 F

A (i .e. observed force at the apex noted in our study) for four spur auxi liary is 17 gms and the same for MAA is 13gms.

F1 (i.e. force measured for the Smm of moment arm of the torquing auxiliary or the MAA in th e previous study) for the torquing auxiliary was 30 gms and for the MAA was 15 gms.

Substituti ng these va lues,

R for four spur auxi li ary = 17 - 3013 = 7 gms and R for MAA is 13-15/3 = 8 gms

Thus, the frictional res istance obtained in both the situations is nearly the same, and it is approximately 7 to 8 gms. Thus, it can be seen that the method of measuring the forces at the apex is va l idated, although the force magnitudes noti ced in our experiment are apparently at va riance from the earlier method.

Hence, the present study was undertaken to find out experimenta lly which rectangular wires (composition wise as well as size-wise) would have capabiliti es comparable to th e MAA or the four spur torquing aux iliary.