Estetica en Ortodoncia

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O r i g i n a l a r t i c l e

Dental Press J. Orthod.118 v. 15, no. 1, p. 118-131, Jan./Feb. 2010

Aesthetics in Orthodontics: Six horizontalsmile linesCarlos Alexandre Cmara*

Introduction: Smile analysis is an important stage or the diagnosis, planning, treatment andprognosis o any dental treatment involving aesthetic objectives. The evaluation o the in-trinsic characteristics o the smile is a necessary procedure to achieve consistent orm inorthodontic treatments, which in turn makes it necessary to recognize the components and

actors that a ect these characteristics.Objective: The objective o this work is to present six horizontal smile lines and their importance in obtaining the desired results in orthodontictreatments.Conclusion: The analysis o the six horizontal smile lines acilitates the under-standing o the intrinsic characteristics that inter ere in the aesthetics o the mouth. Moreover,a harmonization o these lines gives each pro essional a higher possibility o success in theirtreatments that include aesthetic objectives.

Abstract

Keywords: Orthodontics. Aesthetics in Orthodontics. Dental aesthetics. Mouth aesthetics. Smile.

* Specialist in Orthodontics (FO-UERJ). Certifed member o the Brazilian Board o Orthodontics and Facial Orthopedics (BBO).

INTRODUCTIONObtaining a beauti ul smile is always the

main objective o any aesthetic dental treatment.A ter all, it is the beauty o the smile that willmake the di erence between an acceptable orpleasing aesthetic result or any given treatment.Nevertheless, in spite o its importance, the in-trinsic characteristics o the smile are little dis-cussed. Much is said o the clinical consequenceso dental procedures on the smile, but its in-

trinsic characteristics are not widely evaluated.These characteristics can sometimes be alteredand sometimes not, as they are integral parts o the individual. As such, the eld o dentistry has

no reach over these characteristics, and can onlymake evaluations o them.

Evaluating beauty is always subjective. How-ever, we need adequate tools to overcome thechallenge o this subjectivity. In orthodontics, it is not enough only to recognize what is inter er-ing with the smileit requires a diagnosis o what is not normal, in order to establish a treatment plan. Just as in unctional problems, in which we

ollow conducts that lead us to a diagnosis o the

anomalies, aesthetic problems also require param-eters so we can nd the de ects. When searchingor the visualization o problems, several rules and

assumptions are created, leading sometimes to an


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underestimation o de ects or an overvaluing o rules, creating paradigms that are not supportedby proven scienti c data. The very essence o aes-thetic dentistry, which involves artistic criteria,contributes to this act. The use o simple and re-liable mechanisms can improve the possibilities o success, i not eliminate per ormance errors.

There are some tools that can be used or that purpose. The Diagram o Facial Aesthetic Re er-ences (DFAR) is an auxiliary diagnostic tool that is well suited to that purpose. The diagram con-sists o six rames that surround the maxillary in-cisors and canines; their limits are speci c to each

aesthetic re erence. The unction o the DFAR isto give an exact idea o the positioning and ratiosbetween teeth, as well as their relationship withthe gum and lips.5 Originally conceived to aidin the visualization o maxillary anterior teeth,DFAR, when aided by additional data, makes it possible to objectively evaluate the smile, acili-tating the aesthetic diagnosis and prognosis. Thus,the objective o this work will be to present thenew characteristics o DFAR and its role in thesix horizontal smile lines, which in turn assist

the diagnosis, treatment and prognosis o mouthaesthetics.

DIAGRAM OF FACIAL AESTHETICREFERENCES - DFAR (new characteristics)

The Diagram o Facial Aesthetic Re erences(DFAR) was created to acilitate the visualiza-

tion o maxillary anterior teeth, by suggestingwhat needs to be created or achieved with thoseteeth, aiming or the best possible dental aesthet-ics. The objective o the diagram is to give anexact idea o the positioning and ratios betweenteeth, as well as their relationship with the gumand lips in rontal view. As previously mentioned,the diagram consists o six rames that surroundthe maxillary incisors and canines; their limits arespeci c to each dental re erence. Each rame sur-rounds its respective tooth, observing its limits(Fig 1). Although these rames can serve as re er-ences in the di erent observation planes, DFAR is

evaluated at a 90

view rom the rontal planeinother words, perpendicular to it. Its use acilitatesthe planning and visualization o the best aesthet-ic positioning o anterior teeth, and its objective isto provide data that can assist the reorganizationand restructuring o those teeth, whenever theyneed to be repositioned and/or restored. However,although the original conception o DFAR is use-

ul to assist in the evaluation o mouth aesthet-ics, a ew re erences o dental, gingival and labialstructures can be added to its ormat, improving

and acilitating the visualization o the smile.In its original ormat, DFAR makes re erence

to the gingival apexes, which are most apical land-marks o the gingival contour. The present reeval-uation will add the locations o the extremities o gingival papillae (papillary tips) and emphasizethe contact points (Fig 2).

FIGURE 1 - Diagram o Facial Aesthetic Re erences (DFAR). FIGURE 2 - DFAR with new re erence points: contact points and gingivalpapillary tips.


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Aesthetics in Orthodontics: Six horizontal smile lines


The union o these points will orm lines that give evaluative re erences in the analysis o thesmile. As such, DFAR will intrinsically have ourlines, ormed by the ollowing structures (Fig 3):

Cervical linegingival apexes. Papillary linepapillary tips. Contact points linecontact points. Incisal lineincisal edges (incisal line).The relationship o the papillary line with

the contact points line will create a band namedconnector band, in a re erence to the concept o dental connectors.19 This band, ormed by thetwo lines (papillary and contact points), added

to the cervical and incisal lines, will provide thehorizontal dental re erences o the smile in arontal view.

The other two lines that make up the groupo horizontal smile lines are the upper lip lineand lower lip line. These lines, along with thedental and gingival lines, compose the group o six horizontal smile lines (Fig 4).

CERVICAL LINEThe cervical or gingival line is ormed rom

the union o the apexes o the canines, maxil-lary lateral and central incisors. As the most api-cal point o the gingival contour, the apex in

maxillary teeth is usually located distal to thelong axis o the tooth. However, this rule doesnot always apply to the maxillary lateral inci-sors. On those teeth, the gingival limit may becentered on the long axis. Because the apexeso the maxillary canines are most o ten higherthan the lateral incisors and about the same levelas the central incisors, the cervical line attains aconvex aspect in relation to the occlusal plane.That would be the ideal orm o the cervical line. When the lateral incisors are positioned moreapical, at the same height as the canines andcentral incisors, the line becomes plain. When

the gingival contour o the canines is below thelateral incisors, the line ormed will be concave(Figs 5 to 7). The concave cervical line is the least pleasing among the three possibilities.

There will be situations in which the heightso the anterior teeth will be asymmetrical, lead-ing to the ormation o an asymmetrical cervicalline (Fig 8). It should be clear that the positiono the gingival apexes can vary widely betweenteeth and each individual will have a uniquelyshaped cervical line, making it practically impos-

sible to characterize all the possibilities. The no-menclature used or the cervical line (plain, con-cave, and convex) serves only as an evaluation

FIGURE 3 - Aesthetic re erence lines: Cervical Line (A); Papillary Line(B); Contact Points Line (C); Incisal Line (d ).

A

B

C

D

FIGURE 4 - The six horizontal smile lines. Cervical Line (A); Papillary Line(B); Contact Points Line (C); Incisal Line (d ); Upper Lip Line (e ); LowerLip Line (F).


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re erence. The variation in the cervical height o teeth will depend on the periodontal conditionso each tooth, as well as on tooth size, tipping,eruption pattern, and occlusal plane tipping.

INCISAL LINEThe incisal line ollows the edges o anterior

maxillary teeth. The ideal is that in young pa-tients the incisal edges o the central incisors bebelow the edges o the lateral incisors and ca-nines in a rontal view. In that con guration, the

orm o the incisal line resembles the outlineo a deep plate (Fig 9). A change in the posi-

tioning o the incisal edges modi es that gure. When the incisal edge o the central incisors areno longer below the lateral incisors, the outlinewill change, becoming known as shallow plate,or depending on the relation, an inverted plate.

In general, the con guration o the incisal lineis related to the patients age. Over time, thereis wear o the central incisors, leading to thesechanges. However, it is not only wear-relatedchanges that a ect the outline o the incisal line.

FIGURE 6 - Plain orm o the cervical line. FIGURE 7 - Concave orm o the cervical line.

FIGURE 5 - Convex orm o the cervical line.

FIGURE 8 - Asymmetrical cervical line. FIGURE 9 - Incisal line in the orm o a deep plate.


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As with the cervical line, tooth size, tipping,eruption patterns, and occlusal plane tipping canalso alter the outline. The most utilized termwhen the incisal line orms an inverted plateis inverted smile. The line becomes concave inrelation to the rontal occlusal plane, giving anaged and anti-aesthetic appearance. The classi -cation o the incisal line may also use the nomen-clature concave (inverted plate), plain (shal-low plate) and convex (deep plate). Other

requently used terms to describe the incisal lineare the smile arch,25 incisal curvature6 andseagull wing.16

CONTACT POINTS LINEThe contact between anterior maxillary teeth

is done in a descending ashion, starting rom thecanine. The contact between the canine and lat-eral incisor is positioned higher than the contact between the lateral and central incisors; the con-tact between the central incisors is even lower.The contact points should be narrow, unlessthere is a discrepancy in the mesio-distal diam-eter o the crown.2 The position o the contact

between teeth is related to tooth position andorm.16 As such, the line that unites these points

will be parallel to the incisal line, whenever thereis no discrepancy between the sizes, shapes andangles o anterior teeth. Although there is a con-tact point whenever a tooth touches another, theideal is when that contact happens in an areabroader than a single point, orming a connect-ing space. Connecting spaces are areas in whichteeth appear to touch. As will be seen urtheron, this act has a positive infuence on dentalaesthetics. For practical purposes, whenever thedental contact takes place over an area instead o in a single point, we consider the most apical siteas the re erence or the contact point (Fig 10).

PAPILLARY LINEThe papillary line is ormed by the tips o the

gingival papillae located between the canines and

lateral incisors, and between the maxillary lateral

incisors and central incisors. There are no studiesthat have evaluated the standard height or thisrelationship. In other words, there is no de nitiono an ideal model or the relationship betweenthe heights o the papillae. Nevertheless, based onworks that evaluated the ideal height o the cen-tral incisors and the relationship between the pap-illary tips and the position and size o teeth,13,27 it can be presumed that an ideal line would beparallel to the line ormed by the contact points.According to the work o Kurt and Kokich,13 thepapilla in the central incisors lls hal the size o those teeth, under normal conditions. As such, it would be expected that the same pattern wouldbe repeated or the lateral incisors and canines.Given that the lateral incisors are smaller than thecentral incisors and the papilla should ll hal theheight o their crowns, the position o the papillabetween the central and lateral incisor should bein an apical aspect in relation to that o the centralincisors, as well as to the papilla o the lateral inci-sor and canine (Fig 11).

Connector bandThe location where anterior teeth appear to

touch is named a connecting space. As previouslymentioned, there is a di erence between a con-necting space and a contact point. Contact pointsare small areas in which teeth touch. Connect-ing spaces are larger, broader, and can be de ned

FIGURE 10 - Contact points line. This line should have a certain parallel-ism with the incisal line.


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as zones in which two adjacent teeth appear totouch. The best aesthetic relationship o anteriorteeth is one that ollows the 50-40-30 rule orthe connecting space.19 This rule establishes that the connecting space between the central inci-sors should be 50% o the size o those teeth. Theideal connecting space between the central andlateral incisor is 40% o the length o the centralincisors, and the connecting space between thelateral incisor and the canine is 30% o the samere erence. Although the re erence points to de-termine the connecting space were not de nedby Morley and Eubank,19 these re erences can becreated rom the contact points and the gingivalpapilla. There ore, whenever there are no dark spaces or diastemas between two teeth, with thespace lled by the gingival papilla, the area o theconnecting spaces will be delimited by the papil-lary tips and the contact points. As such, usingthe papillary line and the contact points line as

re erence, we will have a band named connec-tor band. The gure o this band resembles theshape o a hang glider (Fig 12). Small changesin this band can make a di erence in dental aes-thetics. Dental remodeling can increase or de-crease the connecting space, resulting in an im-proved con guration o the area (Fig 13).

Clinical ApplicationThe clinical evaluation o DFAR with the

our lines and connector band will permit the useo a checklist that will be able to detect errors intooth positions and their relationship to the gin-giva. By observing the orm o each line, a plancan be drawn ocusing on correcting the de ects,harmonizing the lines, and later evaluating theachieved results. This evaluation acilitates thediagnosis and makes it easier and more practical

or all pro essionals who treat aesthetic problemsto detect problems (Fig 14).

FIGURE 11 - Papillary line. It consists o the tips o gingival papillae. FIGURE 12 - Connector band. This band is delimited by the contact pointsline and papillary line. The fgure o the band resembles the shape o ahang glider.

FIGURE 13 - Un avorable ratio o the connector band 30-40-30-40-30 (A). A simple re-contour with the addition o composite resin between the centralincisors led to the ormation o a avorable connector band: 30-40-50-40-30 ( B).

A B


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Lip analysisIn addition to teeth, DFAR also involves the

lips. A ter the labial evaluation, the six horizon-tal smile lines are ound in addition to the ourdento-gingival lines, there are the upper and low-er lip lines. Both the upper and lower lips havea marked e ect on the beauty o the smile. In-dividually, each lip will infuence the dentolabialensemble, and together they will create guresthat will determine the visible tooth exposure.The lip separation that occurs during smiling willpermit the exposure o dental and gingival struc-tures. This separation can be called labial unveil-ing, as it will be this unveiling that will give thedental work a chance to be shown (Fig 15). Labialunveiling is what makes possible the evaluationo the relationship between the white (teeth) andpink (gums) aesthetics, and their relationship withthe lips. The three-dimensional relationship thesestructures have with one another is what willcause the e ect o beauty or not.

This concept is essential, as it leads to the needto know a series o actors that infuence that un-veiling. The greater or lesser tooth exposure willbe infuenced by labial unveiling and all intrinsic

actors to it, such as its ormation, stages, phasesand lip involvement. As such, be ore we beginevaluating the upper and lower lip lines, we willpresent the actors that a ect the smile.

Smile formationThe smile can be de ned as a change in acial

expression that involves a sparkle in the eyes, anupper curvature in the corners o the lips, no soundemission, and less distortion o muscle orms thanwith a laugh.12 It begins at the commissure andextends laterally; the lips may initially remain incontact, except in people who do not eature pas-sive lip seal or have a short upper lip. As the smileexpands, the lips separate, the commissures curveupwards, and the teeth are exposed. The maxil-laries are separated, and a dark space develops be-tween upper and lower teeth, known as negativespace.18 During smiling, upper lip height is dimin-ished, and the width o the mouth is increased by23% to 28% compared to the lip at rest.26

FIGURE 14 - CHECKLIST Cervical line: concave (accentuated) and asymmetrical. Incisal line: inverted deep plate orm (concave) and asymmetrical.Connector band: 30% (13/12) 20% (12/11) 40% (11/21) 20% (21-22) 20% (22/23) (A). CHECKLIST Cervical line: concave (slight) and symmetrical.Incisal line: deep plate orm (convex) and symmetrical. Connector band: 30% (13/12) 35% (12/11) 40% (11/21) 35% (21/22) 30% (22/23) (B).

FIGURE 15 - Labial unveiling.

dentAl exposition AreA

A B


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The symmetry o muscle activity should not be overestimated. In normal people, individualvariability o motor unction is observed be-tween di erent sides o the same individual.Combined measurements, both o skin mobilityand muscle activity, indicate that there is an av-erage asymmetry o 64% between the sides o the human ace.4

Stages of the smileIn smile analysis, its stages should be observed.

There are two stages in smile ormation: the rst (voluntary smile) elevates the upper lip towards

the nasolabial groove through the contraction o the elevator muscles that originate in this grooveand are inserted in the lip. The medial bundles el-evate the lip in the area o the anterior teeth, andthe lateral bundles act on the area o the poste-rior teeth. The lip then nd meets resistance dueto the adipose tissue in the cheeks. The secondstage (spontaneous smile) begins with higherelevation, both in the lip and in the nasolabialgroove, under the action o three muscle groups:the elevator o the upper lip, originating in the

in raorbital area; the zygomatic major muscleand the upper bers o the buccinator muscle.23

The appearance o hal -shut eyes should accom-pany the nal stage and represents the contrac-tion o the periocular musculature (orbicularmuscles o the eyes), in order to support themaximum elevation o the upper lip through thenasolabial old. The hal -shut look that accompa-nies the smile is a muscular trigger o the acethat activates the centers in the temporal anteriorarea o the brain, which regulates the productiono pleasant emotions. There ore, without this nalaction o semi-closure o the eyes, the noticeablehappy smile is probably a alse smile, without joy

rom the person who gives it 9 (Fig 16).

Phases of the smileIn addition to the stages, the smile also ol-

lows phases. These phases are three old: the rst is named the initial peak phase, which corre-sponds to the period in which the lips depart

rom a neutral position until the position o maximum lip contraction during the spontane-ous smile. During this phase, mouth width isincreased and lip height is reduced, the commis-sures move upwards and sideways in the same

ratio, with great individual variability in the di-rection o the movement o these points. It is

FIGURE 16 - Resting position (A). First stage o the smile Social smile ( B). Second stage o the smile Spontaneous smile. Notice that in this stage thepatients eyes are hal -shut. ( C).

A B C


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the shortest phase o the cycle, lasting on aver-age less than 0.5 second. The second phase is lipsupport. It is during this phase that the smileis dependent on stimulus. The duration o thisphase is quite variable and depends on individualvolition. The last phase is the decline, in whichthe lips close again. The duration o this phaseis usually longer than the initial peak phase, but as with the support phase, it is not possible tomeasure its duration because it is subject to astimulus. In evaluating the smile cycle, it canbe observed that the only reproducible phase isthe initial one. Unlike the other phases, which

can be infuenced by individual volition, thepeak phase depends only on the initial stimu-lus that causes the smile, although its duration isextremely brie .26 This hinders the collection o static images, such as photographs, as it is practi-cally impossible to record the maximum smileobtained during the rst phase. That is why sev-eral authors advise against evaluating the smileusing photographic images, recommending in-stead that video images be taken.1,24

Stimulating and recording the smileAlthough 18 types o smiles have been re-

corded,9 the smile that directly interests the eldo dentistry is the one that expresses joy. Thisis the smile type known as Duchenne, in whichthere is a contraction o the orbicular muscula-ture o the eyes combined with traction o thecorner o the lip by the zygomatic major muscle;among the di erent types o smiles, it is the onethat best demonstrates satis action or happiness.It is the spontaneous smile.9 As such, the smilethat expresses pleasure is the type that pro es-sionals seek to record. For that type o record,a stimulus is necessary. In this case, the stimu-lus becomes a problem, as what is unny to oneperson is not so to another. The di culty in ob-taining photographs that represent the patientsnatural smile in clinical practice was observed byRigsbee et al,22 who reported that the interac-

tion o the photographing pro essional and thepatient should not be underestimated, and sug-gested the use o phrases to obtain the picture. This method is also recommended by Zachris-son30, who suggests the use o the word cheeseto stimulate the exposure o the incisors dur-ing smiling. For records o the resting position,the author recommended that teeth be slightlyapart, and that perioral so t tissues and the man-dibular position be relaxed.30 Although the useo phrases can be use ul, the best way to obtaina smile is through comic stimulus. The use o videos, photographs, or even the pro essionals

comic ability can be used to provoke the stimu-lus. What is important is that the stimulus causesa smile that expresses pleasure. For evaluationsthat involve the relationship between the teethand upper lip, it is recommended, in spite o possible questioning, that the patient pronouncethe sound o the letter e in an uninhibited andexaggerated manner. This causes the maximumelevation o the upper lip.21

Recording the smile is another problem. Theideal is that static (photographs) and moving

(video) records be made. In the static records,image gathering should include close-up shotsin rontal, sagittal, and oblique planes. For themoving records, video should be recorded anduploaded to a computer, and the best image se-lected.24,25 During the evaluation, pre erence canbe given to the social or spontaneous smile withmaximum elevation o the upper lip. What isimportant is that the initial record be the sameas the nal record, so that di erences can beevaluated without inter erence rom the di er-ent stages. In other words, i the rst record wasmade in stage 1, so should the nal record.

UPPER LIP LINEThe upper lip line represents the lower edge

o the lip, and dictates the exposure o upperteeth. Not only anterior teeth have their expo-sure limited by this line, but posterior teeth as


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well. Several authors recommend that duringsmiling, the position o the lower edge o the up-per lip should coincide with the gingival edge o the maxillary central incisor.14,15,17 However, oth-er authors consider that a smile could be aesthet-ically acceptable with exposure o up to 2 mmo gingival tissue.3,10,30This di erence in opinionsleads to inadequate and con using concepts that do not help the standardization o smile classi -cations. Although the simplest way to classi y thesmile lineusing the relationship between themaxillary incisors and the upper lipis throughheight (low, medium, and high), the description

o the parameters is still inadequate. For example,the classi cation o smile heights as described byTjan et al29 used by Dong et al,8 regards as highany smile in which the crown o the maxillarycentral incisor is totally exposed. There ore, asmile with a band o gingival tissue only 1 mmthick would receive the same classi cation as asmile with, or instance, 5 mm o gingival tissueexposure. The same can be said o the classi ca-tion described by Teo,28 which classi es as Class Iall smiles in which the buccal sur ace o the inci-

sor is totally exposed, regardless o the amount o visible gingival tissue. Likewise, the classi cationo a smile when the upper lip does not exposethe maxillary incisors is also con using in the de-scriptions by some authors.3,11 In the Goldstein11 classi cation,a smile eaturing the upper lip cov-ering only 1 mm o the crown o the maxillarycentral incisor will receive the same classi ca-tion as another smile with the upper lip coveringmore than hal or even the entire crown o themaxillary central incisor.

As previously mentioned, the ideal is or theheight o the smile line to be classi ed using asre erence the relationship between the loweredge o the upper lip and the gingival edge o the maxillary central incisor. However, a 2 mmlimit should be established above and below thegingival edge, thus instituting the three classeso smile height: high, medium, and low (Fig 17).

As such, a positive aspect is that, with a 4 mmdi erence, the di erentiation o high and lowsmilesthe smile types that lead patients to seek treatmentis clinically acilitated.21 Moreover,a numeric di erentiation is created among theheights, making it easier to measure their clas-si cation.

Smile height is infuenced by age and gender.The older the individual, the greater is the ten-dency or a low-type smile.7 This piece o in or-mation is clinically relevant, as high smiles tendto become medium smiles with age, and lowsmiles become even lower over time. In other

words, there is a possibility o sel -correction orgingival smiles over time, which is not true orlow smiles.

Gender also seems to infuence smile height.Although not many studies exist on the subject,the work o Puppin21 shows that there is a greatertendency or women to show medium (55.9%)and high (37.7%) smile lines, while men eaturemedium (54%) and low (23.8%) smile lines.These ndings are similar to the values ound inthe work o Peck, Peck and Kataja,20 who also ob-

served that medium (52.2%) and high (32.5%)smiles are more common in women and that me-dium (48%) and low (33%) smiles prevail in men.

The smile line can be regarded as a determin-ing actor in the evaluation o mouth aesthetics.

FIGURE 17 - High smile (A); medium smile (B); low smile (C).

Ahigh smile

Bmedium smile

Clow smile


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The aesthetic results o orthodontic treatmentsalways maintain a strong relationship to this line.It is not uncommon or the conclusion o orth-odontic treatments to be compromised by thesmile line. Either high or low smiles can com-promise the results. This is perhaps the great challenge o contemporary orthodontics in itssearch or excellence. The integration betweenthe di erent dentistry specialties will need to beexpanded also to the medical elds that can posi-tively inter ere in the solution o mouth aesthet-ic problems that are compromised by the nega-tive infuence o the smile line, in particular the

upper lip line. Medical and dental interventionsthat are able to correct a negative labial infuenceare always welcome. This integrated approach bypro essional teams will bring new possibilities o better results, expanding treatment options, andperhaps creating a higher demand or the solu-tion o problems involving mouth, acial anddental aesthetics.

LOWER LIP LINEAlthough the lower lip line is less studied

than the upper lip line, it is no less important. It consists o the group ormed by the upper andlower lips that will produce labial unveiling.

In general, it is the shape o the lower lip andthe incisal edges o maxillary and mandibulartips that create a pleasing or unpleasing smile en-semble.25 What is important is that the maxillaryincisal plane and the shape o the lower lip retaina harmonious relationship.30 That harmony isrepresented in the parallelism o the arch ormedthe incisal edges o maxillary teeth with the up-per edge o the lower lip.

There should be harmony between the cur-vature o the incisal edge o anterior maxillaryteeth with the curvature o the upper edge o the lower lip during voluntary smiling.11 This re-lationship between the incisal edges o caninesand maxillary incisors with the lower lip is calledthe smile arch.10,24 The ideal is or the curvature

o incisal edges to be parallel to the lower lip andthe incisal edges slightly apart or so tly touch-ing the lip. However, this is only possible whenthe lower lip creates a natural curvature, with thecorners o the mouth turned upwards, and incisaledges ollow that curvature. In other words, inorder to achieve a pleasing e ect, it is necessarythat dental and labial structures be symmetrical.In case the lips or teeth limit the parallelism be-tween them, the smile arch will not be possible.Labial asymmetry is also a limiting actor or thisharmony between teeth and lip.

As previously mentioned, the ideal is that the

line ormed by the incisal edges o anterior teethcreates the orm o a deep plate, in which thecentral incisors are positioned more in erior tothe lateral incisors and canines, and are in har-mony with the other smile lines5 (Fig 18).

This con guration varies with age. As age ad-vances, the deep plate orm is altered, givingway to a new shallow plate or inverted plate

orm. That is, the line that contours the incisaledge becomes plainer or more concave. The wearin the incisal edges creates these new orms over

time. Knowledge o these characteristics createsthe possibility o rejuvenating or aging a smile. Achange in the plate orms can make this e ect possible5 (Fig 19).

FIGURE 18 - The vertical positioning o the maxillary incisors and caninesorms a curvature; the line that contours this relationship resembles the

fgure o a deep plate.

m a ch


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It should be clear that the ideal relationshipo parallelism between maxillary teeth and low-er lip is dictated by the lip. The contraction pat-tern o the lower lips and their relationship withteeth are much less uni orm than those o theupper lips. Whereas in the relationship betweenthe upper lip and maxillary teeth it is possibleto establish three de ned positions with regardto the smile line (high, medium, and low), thesame is not possible with the lower lip. Thesmiles own dynamics complicate this evalua-tion. The possibility o an individual opening hismouth wider or not makes a standardized evalu-

ation more di cult. Maxillary teeth may occa-sionally touch the lower lip (contact position),remain apart (non-contact position), or else becovered by the lip (covered position).10 Thissituation can vary among individuals or even inthe same person depending on mouth opening.The muscle contractions o the lower lip alsoalter this relationship. Muscles such as the riso-rius, mentalis, triangularis and quadratus o thelower lip are responsible or the contraction o the lower lip and its greater or lesser participa-

tion during smiling inter eres in labial contrac-tion and symmetry.23 Variations in the contrac-tion and intensity o muscle groups play an im-portant role in the creation o di erent smiles.

Vigorous contractions pull down the lower lip,increasing tooth exposure. Individuals with in-tense contractions o the lower lip tend to alsoexpose their lower teeth (Fig 20).

This situation requires attention, as the needsand possibilities o the aesthetic treatment change perspective, because the evaluation isusually made o the relationship between thelips and maxillary teeth, and not the ull arch.Seeking parallelism between the incisal line andthe lower lip (smile arch) is totally un easible,showing us that establishing aesthetic rules andobjectives by taking the lower lip in consider-

ation does not allow standardizations. Anothersituation that also creates di culties in obtain-ing the smile arch is when the lower lip con-tracts in an inverted ashion; the contraction o the lower lip is greater in the area o the caninesthan in the area o the incisors, possibly due togreater action by the risorius muscle. When theupper lip also contracts in the same manner, theappearance o mirroring is created betweenthe lips. This lower lip contour is usually ac-companied by a low smile line and the gure

ormed by the lips resembles the in nity symbol( ). (Fig 21). This in nity-type smile gure in-dicates an un avorable prognosis or mouth aes-thetic treatments.

FIGURE 19 - The vertical repositioning o the maxillary incisors and canines, a ter an ortho-surgical treatment eaturing maxillary impaction and rotation,resulted in an improved relationship between the incisal edges o the maxillary anterior teeth and the lower lip, creating the deep plate fgure. Thisconvex line gives a more pleasing and jovial aesthetic aspect ( A, B).

A B


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CONCLUSIONKnowledge o the intrinsic characteristics o

the smile helps in the aesthetic perception o it.Being able to evaluate the smile o each patient assures the pro essional o the possibility o see-ing what needs to be done, what can be done, andwhat should be accepted. In other words, beingable to interpret the nuances o a smile gives eachorthodontist the opportunity to act in a consciousmanner in the mouth aesthetic treatment o theirpatients, allowing the diagnosis to be integratedwith the prognosis and giving a realistic outlook o the results than can be obtained. In that per-spective, the six horizontal smile lines meet thispurpose, as the analysis o these lines acilitates theunderstanding o the intrinsic characteristics o thesmile and gives each pro essional a better look intotheir chances or success. Nevertheless, we knowthat observing the six lines is not enough to evalu-ate a smile. Several other actors also need to betaken in consideration. Buccal corridor, number o exposed teeth during smiling, rontal, oblique andpro le acial analyses, relationship between restingand speech positions and the smile are some actorsthat should also be observed in order to achievea better diagnosis o mouth aesthetics. Althoughthese components were not examined in this work,

they should not be ignored, as, along with the sixlines, they can allow a complete observation o thesmile, acilitating its understanding and treatment possibilities.

ACKNOWLEDGEMENTSAdilson Torreo, Adilson Torreo Filho, Aldino

Puppin, Isana lvares, Jonas Capelli Jr., MarcoAntnio Almeida, Vera Cosendey.

FIGURE 21 - Mirroring o lower lip and upper lip orms. Notice that thearea o the lower lip (yellow arrow) is closer to the upper lip than thelateral areas (white arrows). The fgure ormed by the lips resembles theinfnity symbol ( ).

FIGURE 20 - Excessive contraction o the lower lip, completely exposing the mandibular incisors.

Submitted: March 2009Revised and accepted: December 2009


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Cmara CA

131 v 15 no 1 p 118 131 Jan /Feb 2010

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Contact addressCarlos Alexandre CmaraRua Joaquim Fagundes 597, TirolCEP: 59.022-500 Natal / RNE-mail: [email protected]

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