The esthetic zone of smile - Virtual Journal of Orthodontics

function outcomes. The firstmeasurable assessment was madeby Andrew by his ‘Six keys tonormal occlusion’ which couldmeasure the final outcome of thetreatment and which became afuture foundation for developingpreadjusted appliance system withvarying degrees of tip and torquevalues 3 .It must be understood thatthere is no universal “ideal” smile.The most important esthetic goalin orthodontics is to achieve a“balanced” smile, which can bestbe described as an appropriatepositioning of the teeth andgingival scaffold within thedynamic display zone 4 .As mentioned above, this includeslateral, vertical, andanteroposterior aspects, as well asthe cant of the maxillary anteriortransverse occlusal plane and thesagittal cant of the maxillaryocclusal plane. Smile design andmechanotherapy must be builtaround this esthetic plane ofocclusion, which is often differentfrom the natural plane ofocclusion. The first considerationin obtaining a consonant smile arc,or preserving an already consonantsmile arc, is bracketpositioning .Smile design alsonecessitates changes in overalltreatment mechanics. In cases withhigh labial ectopic maxillarycanines, for instance, levelling witha continuous archwire will intrudethe maxillary central and lateralincisors and thus flatten the smilearc .For such cases segmentedarchtechnique using cantileversprings offers better control oflevelling and of the aesthetic planeof occlusion. Creating attractivesmile depends upon factors likewhether the problem is dental orskeletal, any periodontal disease,missing teeth, etc .During thiscourse of action an orthodontistmay spend much time in detailingas was spent for major correctionslike skeletal discrepancy, severecrowding, space closure androtations .Frequently the patientsbecome impatient because of therequirement of the second andthird order changes in buccalsegment 3 . For this role of bracketselection and placement plays avery important role 3 . People with anormal dental appearance arejudged more socially attractiveover many personal characteristicsthan those with malocclusions.Those with poor dental estheticshave been linked to lack of selfconfidenceand are thought to bedisadvantaged in social,educational, and occupationalsettings 4 . Though, various authorshave written extensively in theliterature regarding the importanceof various factors to be consideredin aspect to smile designing. Thisarticle reviews concepts andprinciples of smile esthetics inorthodontic treatment that shouldlend esthetics to the entireorofacial complex involving unity,form, colour, function and displayof dentition.Clinical EvaluationThe most important aspect of theclinical assessment is for theclinician to know what to evaluate13

image size). The resulting numberwas copied and pasted in place ofthe width reading, and the changeswere applied to the JPEG file.Evaluation of smile design is tobe considered under followingclinical evaluation;1) Dento-facial analysisFig 1 - Video camera set on atripod at 4 feet distance from thesubject in sitting position2) Dental analysisTooth analysisTooth and lip analysisStandardization of imageThe frames can be edited in avideo editing software (DVD videosoft studio) This converts the videointo JPEG. Then, each JPEG file ofthe selected subjects can beopened in Adobe Photoshop CS2(Adobe Systems, San Jose,California) and then adjusted byusing the ruler option in the frame.The method used to standardizethe image was as described byDesai et al 7 First, the resolutionwas changed to 300 pixels per inchby going to ‘‘image > image size.’’Then, the ruler function waschosen and set to millimeter whichcan measure a minimum of 0.1mmlength. On the parallel end of theruler, a 10-mm area, close to thesmile, was measured. That numberwas divided into 10 (10/measurement on JPEG file) andmultiplied by the width value foundin image size screen (image >Tooth and gingivalanalysisDENTO-FACIAL ANALYSISMidline DiscrepancyIdeally, the dental midline shouldbe in align with the facial midlinebut usually it does not. As long asthe midline is parallel with the longaxis of the face, midlinediscrepancies of up to 4 mm willgenerally not be perceived asunesthetic. Slight corrections ofmidlines can be accomplished withrestorative dentistry as long as themaxillary centrals are maderelatively symmetric and correctintertooth relationships aremaintained. If the individual teethdo not require restoration andthere is a large midlinediscrepancy, the ideal treatment isorthodontic treatment. One shouldalso check the soft tissueattachment hindering the closureof midline diastema 6 (fig2)15

Fig 2- Midline diastema greaterthan 4mm requires orthodontictreatmentDENTAL ANALYSISTooth analysisbeen discussed in the literature tobe between 70% to 80% 8 .Smileswith these values were most oftendeemed “esthetic to highlyesthetic.” The most estheticallypleasing ratio was 80%. It isextremely important to note thatthe esthetic perception of widthto-lengthratios is significantlyaffected by the outline form andthe reflective surface of the tooth.The lateral incisors are between 1mm to a maximum of 2.5 mmshorter than the central 8 . For amore petite smile, more toward the2 mm to 2.5 mm length isrecommended. The canine isslightly shorter than the centralbetween 0.5 to 1 mm 8 .The next step is to evaluate therelationship of the lips to the teeth,ie, visual tooth display bothstatically and dynamically 7 .Intratooth evaluationThe average length for maxillarycentral incisors has been measuredat between10 mm to 11 mm.Patients who seek esthetics as aprimary reason for treatment wantto have a full smile with “aboveaverage” looking teeth. Acc toEdward Larren 8 the esthetic zonefor the central incisor to bebetween 10.5 mm and 12 mm. Agood length to start the design is11 mm, as it can be modifiedbased on the many other treatmentplanning parameters. The widthto- length esthetic relationship hasContacts, connectors, andEmbrasure MorphologyThe elements of tooth contacts,connectors, and embrasures can beof real significance in planning thetreatment of the smile. Contacts(interdental contact points) aredefined as the exact place that theteeth and touch (what makes flosssnap). The connector (also referredto as the interdental contact area)is where the incisors and canines“appear” to touch. The contactpoints progress apically as theteeth proceed from the midline tothe posterior. The connector heightis greatest between the centralincisors and diminishes from the16

central to the posterior teeth. Theembrasures (the triangular spaceincisal to the contact) ideally arelarger as the teeth progressposteriorly. The shape of the spacebetween your teeth called theembrasure These should beconsider before finishing thecontacts as they can be to wide ornarrow 10 .(fig 3 and 4)Fig 3-embrasures can be too wide or narrowgiving unesthethic appearanceFig 4- Contact between anterior teeth iswhere teethactually touch; connector iswhere teeth appear to touch. Embrasures aresmallest between central incisors and growlarger as they progress posteriorly indentitionIntertooth evaluationTooth proportionality and GoldenratioWhen a person smiles and theteeth are displayed, there is anintertooth relationship that needsto be maintained for thecomposition to be consideredesthetic. The maxillary centralincisors should be relatively butnot perfectly symmetrical. Theyshould dominate but notoverwhelm the smile 8 .This isobviously very subjective, butresearch has shown that in smilesdetermined to be esthetic, therewas a clear dominance of themaxillary central incisor. Minooetal 9 had suggested that thegolden proportion was not thesame perceived maxillary anteriorteeth widths of individuals with anesthetic smile and concluded thatdue to variety in nature, estheticsin dentistry cannot be justifiedmathematically; individuals shouldnot be standardized in the sameway . Though many authorsrecommend using the goldenproportion to define the opticalwidth of the maxillary teeth as theygo posteriorly many studies hasdemonstrated that the actualmeasurements of most people’santerior teeth do not in fact followthe golden proportion. It has notbeen determined that if a person’soptical tooth display followed thegolden proportion that this beconsidered more esthetic thanother arrangements. Acc to EdwardLarren 8 experience, the relationhipof the maxillary lateral to centralincisor comes very close to thegolden proportion in an estheticsmile, and can be used as a guidein shaping teeth 9 . A good guide isto make the optical width of thelateral incisor about 65% of thecentral incisor (or a little less thantwo thirds).The canine does notfollow the golden proportionoptically and is generally about75% to 80% or about three fourthsto four fifths of the optical width of17

the lateral incisor in smiles thatwere considered highly esthetic,with an esthetically acceptablezone from 70% to 85% (fig 5 and 6)Fig 5–The golden proportionmust be maintained so as to getthe best esthethicsFig 6- Width to length ratio isnot the same and esthethicpercentages is does not followsthe golden proportion 8Tooth and lip analysisIncisor exposure and Smile LinePublished reports have shown thatthe average 30-year-old womandisplays about 3.5 mm ofmaxillary central incisor toothstructure when the lips are at restThe prosthodontic literature hasgenerally recommended settingdenture teeth so that 2 mm oftooth structure is displayed at rest.In the author’s experience, the 2mm exposed at rest is generallyless than desired by estheticallydriven patients , for most patientswho have improved esthetics astheir primary treatment goal,between 3 mm and 4 mmdisplayed at rest will be estheticallyideal. Another guide for evaluatingthe esthetic position of themaxillary anterior incisal edgesapplies when the patient smiles; inan esthetic composition, the tips ofthe maxillary anterior teeth comevery close to touch the lower lip upto a maximum of 3 mm away .Theesthetic treatment would be toreposition the incisal edges of themaxillary anterior teeth withinthese two dentolabial estheticzones. The modality of treatmentwould be determined inconjunction with the evaluation ofall the other smile design andtreatment goal parameters. Ifpatients display less than 4 mm ofthe maxillary central at rest andthe teeth need to be lengthened,the length will generally beachieved by adding to the incisaledge. In an esthetic smile, theedges of the maxillary anteriorteeth follow a convex or gull-wingcourse matching the curvature ofthe lower lip and are generallyradially parallel to the horizon.From a frontal view, the maxillaryarch from central to molar appearsto curve upward, but not always. Ifit does, this apparent curve may be18

a result of a slight posterior cant tothe maxilla or the frequentappearance of the Curve of Spee inthe intact dentition. Slight tomoderate deviations to this patterncan be effectively treated withesthetic recontouring orconservative restorative dentistry.In situations where there is idealtooth form and color but there arediscrepancies to the smile line orvisual tooth display, restorativedentistry is not indicated, as thiswould cause unnecessarymutilation of otherwise healthytooth structure. In these clinicalsituations, and when there ismoderate to severe distortion ofthe smile line, orthodontics wouldbe the more appropriatetreatment 10 .(fig 7)Fig 7- Incisors exposure andsmile line Transverse narrowing of themaxilla, especially in the premolarregion. Expansion of the maxillaryarch is required in order to fill thecorners of the smile. Palatal angulation of themaxillary posterior dentition.Increased palatal root torque and/or expansion of the posteriormaxillary dentition, primarily thepremolar region, are required. Incosmetic dentistry, an increase inthe thickness of the buccal aspectof ceramic restorations on thepremolar teeth may help to fill outthe smile. Retro-positioned maxilla.Maxillary advancement is thetreatment of choiceA broad smile with a minimalbuccal corridor is deemed mostesthetic by lay people;however, abroad smile without a buccalcorridor could also be perceived asfake.If the space appears excessivewhen the patient is smiling, a smallamount of the contours of themaxillary posterior restorations—assuming restorations need to beplaced for restorative reasons. Ifconservative additive or subtractive(ie, esthetic contouring) techniqueswill not work esthetically, thenorthodontics should beconsidered 14 .(fg 8)Dark Buccal CorridorIn an esthetic smile there is whathas been termed negative space,which is a small space between themaxillary posterior teeth and theinside of the cheek 13 . The presenceof dark buccal corridors may bedue to:Fig 8– Right and left buccalcorridors must be considered19

The vertical exposure of themaxillary incisors in relation to theupper lip at rest should be 2−4mm, and on smiling the entirecrown of the maxillary incisorsshould be exposed, with up to 1−2mm of associated gingiva. Aspontaneous smile, which isinvoluntary and expresses joyousemotion, tends to raise the upperlip slightly more than a posedsmile, which is voluntary .DENTO-GINGIVAL ANALYSISThe lips frame the teeth andgingiva. The gingiva frames theteeth. The ratio of tooth structureto the amount of gingival andlabial tissue should be harmonizedto prevent an over-dominance ofany one element. The verticalaspects of smile anatomy are thedegree of maxillary anterior toothdisplay (Morley ratio), upper lipdrape, and gingival display. In ayouthful smile, 75-100% of themaxillary central incisors should bepositioned below an imaginary linedrawn between the commissures.(fig 9)Fig 9 – a; acceptable morley ratiob; excessive display of incisorsOther factors to consider indesigning esthetic gingivalrelationships are: gingival line (therelationships of free gingivalmargins of the maxillary teeth),gingival scalloping and contour,papillary tip positioning, andgingival colorGingival Line and its ZenithThe key esthetic issue is that thegingival line for the anterior teethshould be relatively horizontal tothe horizon and relativelysymmetric on both sides of themidline. It may radiate up slightlyas it goes posterior. It is not criticalthat the lateral incisor gingival linefall incisal to the central as this isnot obvious when a person issmiling. Positioning the lateral tothe central incisor within 0.5 mmgingivally and 1 mm incisally isgenerally perceived as esthetic aslong as horizontal symmetry ismaintained. The contour of thegingival (ie, gingival scallop) to thetip of the papilla should bebetween 4 mm or 5mm and thetips of the papillae should have the20

same radiating symmetry as theincisal edges and the free gingivalmargins. In an esthetic smile, thevolume of the gingiva from theapical aspect of the free gingivalmargin to the tip of the papilla isabout 40% to 50% of the lengthof the maxillary anterior tooth andfully fills the gingival embrasure .Insituations where this conditiondoes not exist, periodontal andorthodontic procedures are thetreatments of choice to create thecorrect gingival architecture.Orthodontics not only positions theteeth but also can repositiongingiva and bone. Gingival colorshould appear pink and healthy orconsistent with the healthy color ofindividual race variations 15,16 .(fig10)According to the accreditationcriteria for the American Academyof Cosmetic Dentistry, “Thegingival shape of the mandibularincisors and the maxillary lateralsshould exhibit a symmetricalhalfoval or half-circular shape. Themaxillary centrals and caninesshould exhibit a gingival shapethat is more elliptical. Thus, thegingival zenith (the most apicalpoint of the gingival tissue) islocated distal to the longitudinalaxis of the maxillary centrals andcanines (Fig 11). The gingivalzenith of the maxillary laterals andmandibular incisors shouldcoincide with their longitudinalaxis 16 .Fig 10 -Ideal gingival scallop 8Two concepts of cosmetic dentistrythat are important to the finalesthetic outcome of orthodonticpatients are gingival shape andgingival contour. In cosmeticdentistry, care is taken in theassessment of the gingivalarchitecture for the anterior teethto have certain characteristics.Gingival shape refers to curvatureof the gingival margin of the tooth,determined by the cementoenameljunction and the osseous crest.Fig 11- Gingival shape refers tocurvature of gingival margin oftooth. Gingival zenith (mostapical point of gingival tissue) isdistal to longitudinal axis ofmaxillary central incisors andcanines. Gingival zenith ofmaxillary lateral incisors shouldcoincide with their longitudinalaxis.Conclusion21

Today, various protocols of smiledesign are available. However,most clinicians wish to use thesimplest protocol with the mostpredictable results. It is to benoted that smile design shouldalways be a multifactorial decisionmakingprocess that allows theclinician to treat patients with anindividualised and interdisciplinaryapproach. The Esthethic zone ofsmile presented in this articleclearly indicates the mostimportant components of smiledesign, their clinical significanceduring the smile design procedure.I believe that the maintain theesthethic zone through theseparameters is a simple andpractical that can help the clinicianto easily comprehend the‘complex’ smile design proceduresof orthodontics.References1- Tjan AHL, Miller GD. Some esthetic factorsin a smile. J. Prosthet. Dent. 1984; 51:24-8.2- Grove Philip. Webster’s Internationaldictionary of the English language, Ed. 14,Springfield, Mass, 1961, G and C. MerriamCompany Publishers, II,21513- Anoop sondi; the implications of Bracketselection and Bracket Placement onFinishing details ;Seminars inOrthodontics ;2001;9;155-1644- Marc b. Ackerman; james l. Ackerman, ;smile analysis and design in the digitalera; journal of clinical orthodontics ;2002;volume xxxvi ; 4;231-2365- Moorrees CFA, Kean MR. Natural headposition: a basic consideration in theinterpretation of cephalometricradiographs. Am J Phys Anthropol; 1958;16: 213−2346- Farhad B Naini;Daljit S gill; FacialAesthetics: Clinical Aessement ; DentUpdate 2008; 35: 159-1707- Shyam Desai, Madhur Upadhyay, andRavindra Nanda. Dynamic smile analysis:Changes with age. Am. J. Orthod.Dentofac. Orthop. 2009;136:310.e1-310.e108- Edward A. McLaren,Smile Analysis andEsthetic Design:“In the Zone”; Insidedentistry; 2009;july/aug; 44-489- Minoomahsh i d evaluation of ‘‘goldenproportion’’ in individuals with an estheticsmile; J esthet restor dent 16:185–193,200410-Varun Pratap Singh; Principles of SmileAnalysis in Orthodontics- A ClinicalOverview; Health Renaissance, January-April 2011; Vol 9 (No.1);35-4011-J. Bennett, R. P. McLaughlin: “OrthodonticManagement of the Dentition with thePreadjusted Appliance,” ISBN 1 899066Isis Medical Media 1997.12-Strang , R.H.W. A textbook oforthodontia . Philadelphia; Lea andFebiger , 199313-Moore T, Buccal corridors and smileesthetics. Am J OrthodonticsDentofacialOrthopedics.2005;127(2):208-213.14-Hulsey CM. An esthetic evaluation oftooth-lip relationships present in smile.Am J Orthod 1970;57:132-44.15-Kurth JR, Kokich VG. Open gingivalembrasures after orthodontic treatment inadults: Prevalence and etiology. Am JOrthod Dentofacial Orthop 2001;120:116-2316-David M. Sarver; Principles of cosmeticdentistry in orthodontics: Part 1. Shapeand proportionality of anterior teeth; Am JOrthod Dentofacial Orthop2004;126:749-522