FALL 1995

EDGELINES

© 1995 Two Swan Advertising Agency

TIP-EDGE GRAPHIC

Article On Edgewise Brackets AndFriction Misses The Tip-Edge Point

By: Peter C. Kesling, D.D.S.

Published Quarterly In The USA

APPLIANCE UPDATES - Q’S & A’S - CASE REPORTS - TECHNIQUE TIPS - REVIEWS

PROFESSOR CHARLES BOLENDER HELPSSTUDENT DURING TIP-EDGE COURSE ATSTRASBOURG UNIVERSITY (SEE PAGE 4).

Tippy makes the friction problemdisappear into thin air. Cover Story.

Figure 2. Crown tipping is an inseparable part of distal tooth movement during sliding mechanics. The effect this has on theeffective vertical dimension of three different edgewise type archwire slots is graphically represented. A) Conventional, narrow,preadjusted archwire slot rapidly closes down on the archwire to cause binding. B) Archwire slot with pivot points in center(Sved) also gets smaller to create binding. C) Tip-Edge archwire slot becomes, in effect, larger vertically making bindingimpossible. This feature also facilitates moving directly into full size archwires.

A recent review of edgewisebracket designs and their effectson friction with archwires in-cluded mention of the Tip-Edgebracket1. The author, Dr. C.G.Matasa, who is not an orthodon-tist, evidently doesn’t appreciatethe functions of the Tip-Edgeslot. He completely missed thepoint.

Matasa also referred to theTip-Edge bracket as a spin-offof the Sved bracket. While re-sembling each other at firstglance, they function in entirelydifferent ways.

However, most orthodon-tists also don’t realize that it isactually the binding between theupper and lower surfaces of op-

posed ends of archwire slots andarchwires that makes frictionclinically significant.

Furthermore it is only thebinding that occurs when a tooth(and its bracket) tips mesially ordistally that is significant. Suchtipping occurs during translationof a tooth along a continuousarchwire—even though stepssuch as the use of power arms orwide brackets are used.

The bracket tips because thetooth tends to rotate about itscenter of resistance. For a typicalcanine this point is located ap-proximately 10 millimeters gin-gival to the archwire slot.2

The more force that is ap-plied to move a canine distally

the greater the friction that isgenerated at each end of theslot. It is much like trying tolead a mule, the harder one pullsthe greater the resistance (Fig-ure 1).

During translation a con-ventional, narrow archwire slotrapidly closes down on thearchwire to cause binding, (Fig-ure 2-A).

Figure 1. The more force applied to aconventional edgewise bracket thegreater the friction.

Continued on page 2

ROTATING CANINES:Common reason for caninesrotating duringt r e a t m e n trevealed inQ’s and A’s.Page 2.

Individual Root Torquing auxil-iaries pro-

vide 3-Dcontrolof pon-t i c s .Page 3.

IRTA’S CANCONTROL BRIDGES:

DR. RICHARD PARKHOUSE CONGRAT-ULATES DR. PETER KESLING AFTER HISPRESENTATION IN CHESTER, ENGLAND(SEE PAGE 4).

TIP-EDGE—The Little Engine That Could,moves an entiresociety over the

mounta in .Page 4.

Pg 2 COVER STORY — QUESTIONS & ANSWERS

Brackets And Friction Continued from page 1

A Sved type slot does notlead to unlimited tipping becausethe pivot points are directly op-posite to one another. Therefore,the points move together as thetooth tips, and begin to bind onthe archwire. This, of course, isthe same action as with all con-ventional edgewise archwireslots—albeit friction might begreater due to the proximity ofpivot points (Figure 2-B).

In the Tip-Edge bracket theportions of the ends of the slotthat would bind on the archwirehave been removed—binding isabsent. The slightest amount oftipping causes the effectivearchwire slot to increase (from.022" up to as much as .028").This, of course, makes frictiondisappear into thin air! (Figure2-C.)

Edgewise Slot isSource of Friction

The role the conventionaledgewise archwire slot plays inthe creation of friction is evenmore evident if one considers theformula for the frictional force(Ffr) between two sliding sur-faces:

Ffr = µ x F

The value of µ (coefficientof friction) is determined by thematerials themselves (Figure 3).“F” represents the force press-ing the two surfaces together.3

Neither contact area sizenor speed of movement havemuch effect on friction. Also,surprisingly, friction is about thesame under wet or dry condi-tions.

In orthodontics, the signifi-cant variable in determining fric-tion is the force pressing thesurfaces together. It is mainly thevertical forces pressing each end

begin to “take a set” within afew days. Both features tend toreduce ligature/archwire friction.Techniques Can AlsoVary Friction

Conventional, (continuousarchwire) edgewise techniquescan create friction at several ar-eas in each quadrant:

A. Canine bracket duringcanine retraction

B. Canine and premolarbrackets as well asmolar tubes duringfinal space closure

In contrast, orthodontistsusing Tip-Edge brackets and theDifferential Straight Arch® Tech-nique may have the best of allworlds. The only sliding betweenattachments and archwiresduring canine retraction and/orposterior space closure occurs inthe molar tubes.

The friction of a wire slid-ing through a molar tube is lessthan that when sliding through abracket. This is true for threereasons:

A. Molar (as the anchortooth) does not tip.

B. Molar tube is longer(wider).

C. No ligatures.The resultant drop in fric-

tion permits relatively rapidcontinuous tooth movementswith minimal strain on anchor-age. This is an advantage beingrecognized by more and moreorthodontists each day as theyabandon static slots for the dy-namics of Tip-Edge.

1. Matasa, CG. The Orthodontic MaterialsInsider, Vol. 8, No. 1, March 1995.2. Tidy DC. Frictional forces in fixed appli-ances. Am J Orthod Dentofac Orthop 1989;96:249-254.3. Bednar JR, Gruendeman GW, Sandrik JL.A comparative study of frictional forces be-tween orthodontic brackets and archwires. AmJ Orthod Dentofac Orthop 1991; 100:513-522.

Figure 3. Values of the static co-efficients of friction between variousmaterials.1

Material/ material, µµµµµ

Steel/steel 0.55Diamond/metal 0.15Sapphire/steel 0.15Metal/metal 0.15Diamond/Diamond 0.10Teflon/steel 0.04

also vary depending on bracketwidth and slot size. However,most important of all is slot de-sign.Tip-Edge Gets The “F”Out of Friction

The Tip-Edge archwire slotdesign prevents the creation ofvertical forces between thebracket and the archwire duringretraction. This could then resultin zero friction because one ofthe components (F) of the for-mula for friction, might itself bezero:

Ffr = µ x 0

Ffr = 0

In fact, because of its uniquedesign, it seems it would be dif-ficult to design a study to com-pare the friction of Tip-Edgeto conventional edgewise brack-ets. In order to simulate theclinical situation, all bracketstested should be free to tip as

of short steps rather than in asmooth continuous motion—butnot when Tip-Edge brackets areemployed (Figure 4-B).

Obviously the forces press-ing slots against the archwiresare not constant. They vary de-pending on the retractive force,the angulation of the slot to thearchwire and/or the size of thearchwire. Vertical forces be-tween brackets and archwires

they move along the archwire.If this were the case, the ends ofthe conventional edgewise slotswould bite into the archwirewhile the effective size of theTip-Edge slot would increase.

Of course, there is anotherfactor that can cause frictionduring space closing or retrac-tion—ligatures. However, steelties can purposely be madeloosely and elastomeric ligatures

Figure 4. A) Conventional edgewise slot binds on wire until friction stops freesliding. Tooth must upright before sliding can resume. B) Tip-Edge slot preventsbinding. Retraction can take place in one smooth, uninterrupted motion under lessthan ¼ ounce (15 grams of force).

of the slot against the archwirethat cause frictional problems.With a conventional archwireslot these forces (F) are directlyrelated to the horizontal pull ap-plied to the tooth.

Eventually crown move-ment stops (Figure 4-A) and canonly resume after periodontalremodeling permits the tooth toupright which in turn reduces thefriction between the archwireand each end of the archwireslot.

This causes teeth to trans-late along archwires in a series

Q. It always amazes me how quickly and easily the mandibularcanines tip distally when aligning crowded incisors. However, it alsoseems this causes the canines to rotate mesiolingually—but not allthe time. Why is this? EL PASO, TEXAS

A. In cases of mild anterior crowding it is customary to placea plain (no vertical loops) .016" archwire with the intermaxillarycircles pressing lightly against the mesial surfaces of the canine brack-ets. This mild force, plus straightening of the archwire as the anteriorteeth align causes the canines to tip distally.

Q’s and A’sHowever, this will cause the

intermaxillary circles to rest overthe labial surfaces of the mesialwings of the canine brackets fora short period of time. Since thedistal portions of the circles arelingual to the buccal segmentsof the wire there is a tendencyto rotate the canines—see fig-ure.

(A) Intermaxillary circles should not contactthe canine brackets. (B) If the circles aretoo far apart they can press on the labialsurfaces of the mesial wing tips and causeundesired mesiolingual canine rotation.Ligature ties deleted for clarity.

RETRACTIVE FORCE ➛ ➛ ➛ ➛ ➛ ➛ ➛ ➛ ➛ ➛

TECHNIQUE TIP – CASE REPORT Pg 3

CASE REPORT

Using IRTA’s To Provide Third Order Control of PonticsOn occasion it is necessary

to hold spaces during ortho-dontic treatment for finalprosthodontic restorations orimplants to replace missingteeth. Attempting to accomplishthis with coil springs is difficultand imprecise.

The use of a pontic the samesize and shape as that desiredfor the final restoration not onlyeliminates repeated adjustmentsof coil springs, but also enhancesthe patient’s appearancethroughout his or her treatment.

During Stages I and II whenround wires are generally usedto facilitate retraction and biteopening, some type of auxiliaryor archwire manipulation is re-quired to prevent the labio-lingual rotation of the ponticaround the archwire. In the past,attempts to provide the neces-sary torque control with a roundbase archwire have provedawkward to fabricate and werecrude in appearance.

Individual Root TorquingAuxiliaries (IRTA’s) provide anesthetic means of precisely hold-

jacent tooth to lock the pontic inplace mesiodistally (the tail ofthe IRTA should extend throughthe brackets of at least two adja-cent teeth for adequate torquecontrol).

With proper shade selec-tion it is difficult to differentiatethe pontic from adjacent teethwhen the archwire is fully en-gaged. The fact that an IRTA isvirtually invisible, significantlyenhances the overall estheticappearance of the appliance(Figure 2).

Once retraction has beencompleted and the patient isready for final uprightingand torquing, rectangular basearchwires can be used to holdthe pontic in its properly torquedposition until appliance removal(if using a Tip-Edge bracketwithout a Deep-Groove, a Side-Winder uprighting spring orTip-Edge elastomeric ring wouldbe required to achieve full torquecontrol with the rectangulararchwire).

Figure 1. Pontic with attached bracketligated to archwire. IRTA is engagedthrough vertical slot and adjusted toprovide third order control of pontic.

Figure 2. Archwire fully ligated withattached pontic to replace missingmaxillary left cuspid. End of IRTA isannealed and bent just distal to themaxillary right central incisor bracketto keep pontic from sliding distally.

ing pontics in place withoutarchwire manipulation or otherauxiliaries. Once the desiredspace has been established, animpression is taken and theproper shade selected. Thelaboratory then adapts theproper size pontic to rest pas-sively against the alveolar ridgewith no visible space betweenit and gingival tissue.

At the patient’s next visitthe labial/buccal surface of thepontic is buffed lightly with agreen rubber wheel and abracket is bonded using theDirect-On® adhesive system.The archwire is then removedfrom the patient’s mouth and the

pontic is ligated to it. An Indi-vidual Root Torquing Auxiliaryis engaged into the vertical slotof the bracket attached to thepontic. The IRTA is then ad-justed so the pontic exerts slightpressure against the alveolarridge without blanching theunderlying tissue when thearchwire is fully engaged. Thearchwire and attached ponticare engaged as a single unit(Figure 1).

To prevent the pontic fromsliding along the main archwiremesiodistally, the end of theIndividual Root Torquing Aux-iliary can be bent either mesialor distal to the bracket on an ad-

K.K. .............................. Female, 18 YearsClass 2, Division IINon-ExtractionArchwires Used ..................... 6 (2U, 4L)Adjustments ......... 15, Time: 22 MonthsRetention ................................. Positioner

Cephalometric Changes:Start - Dotted Finish-Solid–

1-APo -3.0 mm +1.0mmWits +6.0 mm +1.5 mmSN-MP 23.0o 25.0o

ANB 4.0o 3.0o

SNA 82.0o 81.0o

SNB 78.0o 78.0o

–1-SN 94.0o 101.0o

CeramaFlex® Tip-Edge brackets wereplaced in the maxillary arch and metalTip-Edge brackets in the mandibu-lar. Australian archwires (.016") withstrong anchor bends. Class II elas-tics pulling 1 oz. on each side wereworn 24 hours each day.

After 7 months, Stage II began withthe incisors edge-to-edge. Space inmandibular right quadrant was closedwithout braking mechanics to correctthe midline which had shifted slightlyto the left.

This 18 year old female presented with a Class II Division 2 malocclusionwith a deep anterior overbite and generalized spacing of the mandibular arch.A previous orthodontist had insisted that headgear would be required to cor-rect her overbite. She sought a second opinion and was pleased to learn thatno extraoral forces would be needed with Tip-Edge. Due to the spacing presentin the mandibular arch and the position of the mandibular incisors (3mm be-hind the A-Po line) a nonextraction treatment plan was initiated.

Approximately 10 months after plac-ing the appliances, Stage III mechan-ics were initiated with maxillary andmandibular .022" Australian wires.Dual IRTA’s were placed to torquethe maxillary central incisors (Tip-Edge Today, Summer 1994).

Pg 4 COURSE / LECTURE NEWS

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Tip-Edge Course in Strasbourg, FranceE.B.S. Meeting—a Tip-Edge Forum

Drs. Bolender (front row left and right) and students during Tip-Edge Course at theUniversity of Strasbourg.

The EuropeanBegg Society heldits biannual meetingMay 19th-24th inmedieval Chester,England. The meet-ing, under the direc-tion of its president,Dr. Richard Park-house, was well at-tended. Speakers in-

cluded Professors Jim Moss, Hans Pancherz, Kuni Miyajima andMilton Sims as well as Drs. Hans Booy, Peter Kesling, ThomasRocke and Richard Parkhouse. It is interesting to note that Tip-Edgehas become the appliance of choice for all these speakers as well asmost of the other members of the association. Could a Society namechange be eminent?

A side trip to northern Wales included a ride on the FfestiniogRailway—a small, steam driven train that was originally used byslate miners in the mountains of Snowdonia. A stop at ancient ConwayCastle concluded a most enjoyable day.

Tip-Edge Association of MexicoThe third quarterly meeting was held July 28 at TP Mexico’s

new offices in Mexico City. Over eighty orthodontists were in atten-dance as well as Andrew Kesling, President of TP Orthodontics.

Presentations were given by Drs. Antonio Valle (Stage Two andclinical cases), Eduardo Aquilar (Pre Stage Three) and ThomasMendoza (Protraction With Tip-Edge Ceramic Brackets). All of thespeakers have had training in Tip-Edge and the D.S.A.T. with Drs.Kesling and Rocke at the Orthodontic Center, Westville, Indiana.

Drs. Richard Parkhouse, Thomas Rocke, and PeterKesling in front of antique, steam driven slate train.

A two day Tip-Edge course was given in France in March. Itwas held at the University of Strasbourg and organized by Prof.Charles Bolender of the University.

All the orthodontic speciality training students of the Universi-ties of Reims, Nancy and Strasbourg attended. Their official univer-sity training is a four year program resulting in a “Certificat d’étudesspéciales Mention Orthodontíe” (C.E.C.S.M.O.). This “certificate” isnecessary to be an officially recognized orthodontist in France.

Prof. Bolender was assisted in teaching the Tip-Edge course byhis son Dr. Yves Bolender and brother Dr. Guy Bolender.

A more advanced course for orthodontists in private practice isplanned for September 4th and 5th. It will be held at the same loca-tion, Faculté de Chirurgie Dentaire de Strasbourg.

TP Orthodontics UKFountain Court

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