Arch Forms Ortho / orthodontic courses by Indian dental academy

8/12/2019 Arch Forms Ortho / orthodontic courses by Indian dental academy

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INDIAN DENTAL

ACADEMYLeader in continuing dental education

www.indiandentalacademy.com



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INTRODUCTION

The achievement of a stable,functional and esthetic arch form haslong been one of the prime

objectives of orthodontics

Despite numerous investigations,there is little agreement as to the

best size and shape for an idealorthodontic arch form.



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Various authors have used differentcurved mathemetical models,butstability of these arch forms has not

been established

The mandibular dental arch isconsidered as a reference element of

diagnosis and therapy in dentofacialorthopedics.



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DEFINITION

ARCH FORM-

-position and relationship theteeth have with each otherin all 3 dimensions



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-It is the collective response of allteeth to all of the environment forcesand their resultant positions in the

oral cavity (Brader-1974)



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-dental arch form is made up ofteeth which assumes uniquepositions along a compound curve

representing an equilibrium at allpoints and delimited by thecounterbalancing force fields of the

tongue and of the circumoraltissues(Brader)



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DETERMINATION OF

ARCH FORM

Determined by

-skeletal pattern

-muscular forcesneutral zone

( Mills 1968)



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TYPES OF ARCH FORM

BONWILL HAWLEY ELLIPSE PARABOLA CHUCKS ARCH FORM

CANTENARY CURVE BRADER PENTAMORPHIC COMPUTER PRIDICTION VARI-SIMPLEX DESIGN ROTH TRUE ARCH

STRAIGHT WIRE M.B.T BEGG ARCH FORM LINGUAL ARCH FORM



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BONWILL

In 1885, he noted the tripodshape of the lower jaw anddeclared that it formed an

equilateral triangle with the baseextending from condyle tocondyle and the sides extending

from each condyle to the midlineof the central incisors.



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He stated that this triangleexisted for the properfunctioning of the teeth.

Importantly, he noted that thebicuspids and molars formed astraight line from the cuspids to

the condyles.



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It was proposed that thebicuspids and molars should bealigned along these extended

straight lines. Hawley did, however, advised

against the strict use of thismethod for determining archform, and that it be used only asa guide in establishing arch form.



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Arch form is constant for allinduviduals

The radius of the arch varieddepending on the size of the anteriorteeth

This arch form is no longerrecommended



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PARABOLA

Angle , 1907, - Defined line ofocclusion, as being the linewith which, in form and position

according to type, the teeth mustbe in harmony If in normalocclusion. The form Of this linewas said to resemble a Parabolic

curve but one that varied greatlydue to race, type, temperament,etc. of the individual.



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In describing the First order bends,Angle objected particularly to thestraight line proposed from cuspid to

third molar. Angle stated that a straight line

existed from the cuspid to the mesio-buccal cusp of the first molar,

however, there was a naturalcurvature needed in the molar region.



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LandmarksA,D,D,E,E



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GRAY

In 1942, Grays Anatomy stated :

The maxillary dental arch formsan elliptical curve...Themandibular dental arch forms aparabolic curve



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CHUCK

Chuck -In 1934, noted the variation inhuman arch form and pointed out thatarch forms had been referred to as

square, round, oval, tapering. He stated that while the Bonwill-

Hawley arch form was not suitable foruse in each patient, it could serve as a

template for the construction ofindividualized arch forms.



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Chuck superimposed this arch formon a millimeter grid and used thistemplate for archwire construction

according to Angles method. Chuck suggested that the bicuspid

regions should be wider than thecuspids to prevent excessive

expansion of the cuspids.



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DRAWBACKS OF PARABOLA-

ELLIPSE ARCH FORM

MacConaill -1949, stated that, inconsidering the line of occlusion, itwould be impossible for an ellipse and

a parabola to meet one another atevery point.

He concluded that the ellipse-parabola description of the two dental

arches, although elegant, had noimmediate relation to function.



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BLACK

In 1902, he stated that the upperteeth are arranged in a semi-ellipse and that the lower teeth

were arranged similarly on asmaller curve.



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CATENARY CURVE

Mcconnail and scher -1949

He stated that the catenarycurve, fit so many cases withexactness that it could be takenas the ideal curve of commonocclusions.



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Shape formed by a length of chainheld at each end and allowed to drop

Catenary curve could be described asa central core or central perimeteraround which teeth arrangethemselves



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Ignores narrowing of archform overthe second molar

The length of the chain and thedistance between the supportsdetermine the precise shape of thecurve



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Catenary curve fits the dental archform of the premolar-canine-incisorsegment of a arch very nicely for

most individuals

The curve doesnt fit accurately if itis extended posteriorly, because the

dental arch normally curves linguallyin the second and third molar region



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Catenary curve a betterrepresentation of mandibular dentalarch

Ellipse or parabola representsmaxillary arch (Neilans-1968)

Catenary curve is a good fit in

27%of the samples studied (WhiteLW-1977)



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In 1957, Scott also supported theconcept of the catenary curve asthe shape of the human arch

based on the developmentalanatomy of the dental arches andsurrounding anatomic structures.



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He pointed out that the basalbone of the maxilla and mandibleremains much more constant in

form in all mammals and forms afoundation on which a great dealof variation in form of alveolar

processes are constructed



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Burdi and Lillie in 1966 statedthat the basic bony arch isestablished as early as 9.5 weeks

in utero and that this form wasthat of the catenary curve.



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The geometry of the curve of thedental arch form was said to bebest approximated by a closed

curve with the curvilinearproperties inherent in the trifocalellipse, with the teeth occupying

only the portion at theconstricted end of the curve.



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Brader recommended an arch guidewith five arch forms.

The selection of the proper arch formwas based on arch width at thesecond molars as measured at thefacial, gingival surface.

The maxillary archform was selectedone size larger than the mandibulararch form.



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It differs from a cantenary curve inproducing greater width acrosspremolar

The Brader arch form will moreclosely approximate the normal

position of the second and thirdmolars



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SELECTION OF ARCH WIRE

Measure thegreatest intermolardiameter in

millimeter This measurement

gives the optimumarch curve on

guide chart



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The unique geometry of the Braderarch is that it forms a superior dentalarch form

The primary determinants of archform morphology are the tissue force

in resting state



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The geometry of the dental archform is so related with the restingforces of the tongue

PR=C



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The lips and cheek exert inwardcounterbalancing tension against theteeth

PI=Pe+t{1/R+1/R}



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DRAWBACK OF BRADER


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DRAWBACK OF BRADER

ARCH FORM

Many clinicians found that thisarch form created excessivenarrowing in the cuspid region of

many patients and led toexcessive wear of the incisalportion of the cuspids.



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The anterior section of Vari-simplexarch forms is flatter than PAR archforms and more pointed compared to

roth arch forms



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TYPES OF ARCH FORM



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Vari simplex arch form serves merelyas treatment guide, they neverintended to be final arch wire

Final mandibular arch wire is alwaysfitted to the original study model



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Care is taken to determine thatcuspids are not expanded

Mandibular expansion occures inmolar and premolar region

The maxillary arch form is built to fitthe mandibular arch form



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Dr Alexander does not correlate archform to the facial type to keep thecuspid stable.

He does not use Tweeds concept ofco-relating upper and lower archwires since similar arch wires are notplaced in upper and lower arch at thesame time



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PENTAMORPHIC ARCHES

By Ricketts

Atleast 10 factors needed to betaken into account in the research of

arch form



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Twelve arch forms were originallyidentified, these were narroweddown to 5 by ricketts and are called

as pentamorphic arches



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They are

-narrow ovoid

-ovoid

-normal ideal

-tapered

-narrow tapered



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NARROW OVOID OVOID



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NORMAL IDEAL



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TAPERED NARROW TAPERED



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ROTH TRU-ARCH FORMS

The Roth Tru-Arch form was derived fromhis extensive clinical testing and recordingof jaw-movement pattern in treatedpatients who were out of retention andhad stable results

Comparison with arch form derived byAndrews from measurement of his 120

normal cases shows that the Roth archform is wider by few millimeter in thebicuspid region



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Roth notes that superimposition ofhis Tru-Arch form on Ricketts normalform shows that they coincides

almost exactley The Roth Tru-Arch form actually

overcorrects the arch width

slightly;over correction is part ofroths goal



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Arch width varies with facial type

the brachyprosopic arch is seldommore than 2-3mm wider than the

dolichoprosopic arch, but theindividual jaw width may wary moreand the arch wire should be adjusted

to harmonize



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The widest point in the entire arch isat the 1stmolars, but in the frontpart of the arch, the widest part is in

the bicuspids and not cuspids



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There are actually 5 arcs in the arch

-1) the arc acros front

-2,3) another arc in each cuspid ,bicuspid region

-4,5)a uniform curve in the buccalsegment


S


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TYPES

TAPERED

OVOID

SQUARE


STRAIGHT WIRE TECHNIQUE


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STRAIGHT WIRE TECHNIQUE

The arch wire used in this techniqueis slightly expanded in the bicuspidregion to allow proper functional

movements and it is close to rotharch forms



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M B T ARCH FORM


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M.B.T ARCH FORM

M.B.T technique uses arch formused by chuck(1932)

Classified by chuck in 1932

Tapered (narrow)

Ovoid (normal)

Square (broad)


TAPERED


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TAPERED

Ovoid arch formhas the narrowestinter canine width

Used in-gingival recessionin canine andpremolar region

-single archtreatment cases



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SQUARE


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SQUARE

Used in cases withbroad arch forms,

Useful atleast in

part of thetreatment in casesrequiringexpansion of upper

arch, buccaluprighting of lowerposteriors


ANDREIKO THEORY OF ARCH


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ANDREIKO THEORY OF ARCH

FORM

By Andreiko et al -1994

Shape of the mandible shoulddectate arch form,with the teeth

aligned and contained with in thelimits of the mandibular bone



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ADVANTAGES

-The arch form are derived fromthe skeletal and dental anatomy and

are therefore designed to be closerto an anatomic ideal thanmathemetical ideal

-Individualized treatment issimplified


ARCH FORM CONSIDERATIONS


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IN BEGG TREATMENT

Dr BEGG each patient is an entityunto himself, as far as the mostfavorable arch form should bear in

relation to rest of the face and skull



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An arch wire as light as 0.016 canalter the arch form if kept in thebrackets for few months


METHOD TO DRAW INDIVIDUAL


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ARCH FORM

The arch form consists of 3 segmentsan anterior segment between thetwo canine teeth, and 2 posterior

segments from canine to molars oneither side



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The dimensions and curvetures ofthese segments depends on

1)-anterior tooth material-

determines the anterior segmentlength from one canine cusp to theother canine cusp



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2)-width across the cusp tips of 33,43,mesio buccal cusp of 36,46 and distobuccal cusp of 37,47 determines the

transverse dimension of the arch



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3)-arch length measured asperpendicular distance from the midpoint between 31,41 to the line

joining the tips of disto buccal cuspsof 37-47,determines the sagittaldimension of the arch


DRAWING A ARCH FORM


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DRAWING A ARCH FORM

Obtain the above said measurementsfrom patient

Draw a midline on a graph paper

Transfer the canine locations on thegraph paper on either side of thearch midline



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Take a 4 long 0.016 s.S wire.Markon it the length of the anteriorsegment,the wire is flexed such thar

these pointslie on the canine locationin graph,the wire gives the anteriorcurvature



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Location of mesio buccal cusps offirst molars are marked exactely andthe canine marking is extended to it

using a straight or curved line The upper arch form is drawn

parallel to and outside the lower arch

form keeping a distance of 2-3 mm


COMPUTER PREDICTION


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Schulof-1975

Various other arch form have beenconstructed using algebraic

equations



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Arch form are produced frommeasurements of intermolar width,intercanine width and arch depth

from labial surface of incisors to laststanding molars


OTHER ARCH FORMS


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OTHER ARCH FORMS

Williams -1917 described anteriorteeth as lying on the arc of a circle

with its centre midway between thebuccal grooves of 1stmolar



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Sicher-1952-upper arch-elliptical,lower arch-parabolic

Baz -1958 determined normal arch

size by a geometric constructionbased on measurements taken frompatients face



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Kato-1964 no great disparitybetween arches, same arch formmay be classified differently by

different workers Lu 1964 dental arch could be

described by a polynomial equation

of the 4th

degree


THE RELAPSE TENDENCY INHERENT IN


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ARCH FORM CHANGES

MCCAULEY,STRANG,GRABER,ANDERSON,HUGGINS,MILLS,LUDWIG--numerous authors who had

reported that when inter-cuspidand inter-molar width had beenchanged during orthodontic

treatment, there was a strongtendency for these teeth toreturn to their pre-treatmentposition. www.indiandentalacademy.com


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Walter- reported themaintenance of slight increase inmandibular inter-cuspid width

after all retention had beenremoved for what was termed anadequate period.

.



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Steadman also reported similarresults.

Arnold later pointed out that at

least five years must elapsebefore an apparent maintenanceof increase in inter-cuspid width

could be accepted



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1. Inter-cuspid width was expandedduring treatment but had a strongtendency to return to or close to itsoriginal pre-treatment width in bothnon-extraction and extraction cases.

2. It would appear that the inter-firstbicuspid width showed the greatest

treatment increase in width with onlya minimal amount of post-treatmentwidth decrease.



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5. The inter-molar width ofnonextraction cases showedsignifi- cant increase in width

with treatment and theextraction cases showed asignificant decrease with

treatment, However there wereno changes in either extractionor non-extraction cases post-retention. www.indiandentalacademy.com


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6. The incisor to inter-molardistance decreased withtreatment and had a slight

tendency to continue to decreasepost-retention.



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In 1995 De La Cruz, et al.,studied the long term changes inarch form of 45 Class I and 42

Class II Division 1 cases afterorthodontic treatment and aminimum of 10 years post

retention.



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They concluded that arch formtended to return toward the pre-treatment shape after retentionand that the greater thetreatment change, the greaterthe tendency for post-retentionchange.

They suggested that the patientspre-treatment arch formappeared to be the best guide forfuture arch form stability,www.indiandentalacademy.com

NORMAL GROWTH AND


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DEVELOPMENT

Arch dimensions changes withgrowth, it is therefore necessary todistinguish changes induced by

appliance therapy from those thatoccur from natural growth



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MOORREES-has pointed out thatconsiderable individual variations inarch form will occur with normal

growth, with a general tendencytowards an increase in the intermolarwidth during the change over from

the decidous to permanent dentition.



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It is difficult to predict the growthpotential in induvidual patients, butinformation is available on the

average changes in arch dimensionin centered samples



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The average changes reported byMoyers et al shows changes in archwidth vary between males and

females and that more growth inwidth occurs in upper than the lowerarch, this growth occurs mainly

between 7 to 12 years of age, after12years growth in width is seen onlyin males



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SINCLAIR et al have confirmed that theincrease in molar width after age 12 isstatistically different in males and females.

-Male arches grow wider than female

arches-Lower intercanine width increasessignificantly in the change over dentitionbut does not increase in permanent

dentiton after 12 years of age



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-upper and lower inter molar widthincrease spontaneously to aconsiderable extent between ages of

7 and 18 in males-little changes in arch width occurs inthe premolar region after age of 12



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-changes in arch width may not beaccompanied by changes in archlength,there is a tendrncy towards a

decrease in arch depth in third andforth decades


APPLIANCE INDUCED GROWTH


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APPLIANCE INDUCED GROWTH

It is difficult to determine thecontribution of appliance, as anormal growth change would be

expected for each individual



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McNAMARA and BURDON-it seemslogical to consider increasing archsize at a young age so that skeletal

,dentoalveolar, and muscularadoptations can occur before theeruption of permanent dentition.



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An appliance inserted in an activelygrowing patients, shows a favorableresponse,however this response may

have occurred in the absence oftreatment,the relative contribution ofappliance being difficult to determine



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SPILLANCE and McNAMARA-Examined the records of PATIENTS IN

THE Michigan study who presented withnarrow arch forms and compared themwith the average sample. result show thatthose with initially narrow arch forms tendto become more average, and ppliance

therapy is therefore more likely to achievea stable change


INTER CANINE WIDTH


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C

LEWIS & LEHMAN & BAUME haveshown that the inter canine widthincreases during eruption of

permanent incisors and again duringeruption permanent canines



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DUTERLOO and BIERMAN show that thealveolar crest is relatively inactive afterthe deciduous teeth erupt, but it is mostactive during eruption of permanent teeth

and then becomes relatively inactive againafter the permanent teeth have erupted.Therefore if mandibular lateral expansionis ever to be considered, the optimal timeis prior to and during eruption ofpermanent teeth


FACIAL FORM VS ARCH FORM


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dolicocephalic form --longer butnarrower and deeper maxillary archand palate.

Brachy cephalic type --wider butshorter and more shallow palate andmaxillary arch.


ROLE OF SOFT TISSUE MATRIX

IN MAINTAINING ARCH FORM;


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IN MAINTAINING ARCH FORM;

Frankel postulates that the increasein crowding is the result ofhypertonic muscles in the buccinator

mechanism restricting the lateralgrowth of teeth and their supportingtissues.



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The equilibrium theory states thatthe positions of the teeth aredetermined by the balance between

the intrinsic forces of tongue, lips,dental occlusion, and periodontalligament

Supported by Tomes-1873 Opposed by Scott-1967



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ORAL RESPIRATION- Ricketts hasshown that mouth breathing tends tolead to narrow arches, cross bitesand increased crowding

Linder-Aronson and backstrom reportthat children scheduled foradenoidectomy generally have

longer, more narrow faces thancontrol children



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AJO 1980 January Anoop Sondhi, John F. Cleall and

Ellar A. Be Gole

Distal movements of canines duringtreatment does not ensure stableincrease in mandiular inter canine

width.


Analysis of change in arch form

with premolar expansion


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with premolar expansion

Ellen A.BeGole, Cyril Sadowsky (Ajo-1998)

The arch forms of 38 cases in which

expansion, while maintaining archform, were analyzed beforetreatment, after treatment, and an

average of 6 to 8 years afterretention.



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Significant stable expansion of thepremolar and molar widths may bepossible in both the maxillary and

mandibular arches in nonextractioncases.



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Gender has a differential effect onthe maxillary arches of cleft andnoncleft patients; significant

differences are present in thenoncleft group (wider and longerarches in males), but not in theunoperated cleft group.



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BCLP results in an anteriorlyprogressive constriction of the upperdental arch in both genders.

The BCLP group has a significantlylonger maxillary dental arch, which isattributed to the premaxillary

anterior projection.


CONCLUSION


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Clinicians should be cautious whentreating to mathematically derivedarches, since studies have not

determined conclusively what thatshape might be


Thank you


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y


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Arch Forms Ortho / orthodontic courses by Indian dental academy

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