Managing Congenitally Missing Lateral E Incisors Part 1: Canine … · treatment alternatives for replacing missing lateral incisors. C E 4 ADVANCED ESTHETICS & INTERDISCIPLINARY

Managing patients with congeni-tally missing maxillary lateral

incisors raises several important issues:Amount of space? Patient age? Type ofmalocclusion? Condition of the adja-cent teeth? There are three treatmentoptions that exist for replacing missinglateral incisors. These options include:canine substitution, a tooth-supportedrestoration, and a single-tooth implant.There are also specific criteria that mustbe addressed when choosing the appro-priate treatment option. The primaryconsideration among all treatment plansshould be conservation. Generally, thetreatment of choice should be the leastinvasive option that satisfies the expectedesthetic and functional objectives. Theorthodontist plays a key role in achiev-ing specific space requirements by po-sitioning teeth in an ideal restorativeposition. For example, canine substitu-tion can be an excellent, esthetic treat-ment option for replacing missing lat-erals. However, if it is used in the wrongpatient, the final result may be lessthan ideal. Ultimately, an interdiscipli-nary approach is the most predictableway to achieve optimal final esthetics.

SELECTING THE APPROPRIATE PATIENT

There are specific dental and facialcriteria that must be evaluated beforechoosing canine substitution as thetreatment of choice for replacing a miss-ing maxillary lateral incisor. They includemalocclusion and amount of crowd-ing, profile, canine shape and color, andlip level (Figure 1A through Figure1C).1,2 If these selection criteria arefulfilled, the patient can expect a func-tional and esthetic final result.3

MALOCCLUSIONThere are two types of malocclu-

sions that permit canine substitution.The first is an Angle class II malocclu-sion with no crowding in the mandib-ular arch. In this occlusal pattern, themolar relationship remains class II andthe first premolars are located in thetraditional canine position (Figure 2Aand Figure 2B). The second alternativeis an Angle class I malocclusion withsufficient crowding to necessitate man-dibular extractions. With either of thesetwo malocclusions, the final occlusalscheme should be designed so that the

Managing Congenitally Missing LateralIncisors Part 1: Canine Substitution

Learning Objectives

After reading this article, thereader should be able to:• evaluate specific patient selection

criteria and determine if canine sub-stitution is an appropriate treat-ment alternative for replacingcongenitally missing maxillary later-al incisors.

• identify how to position the caninesto satisfy functional requirementsand achieve proper esthetics.

• recognize the importance of inter-disciplinary treatment planning toachieve optimal anterior esthetics.

Greggory A. Kinzer, DDS, MSDAffiliate Assistant Professor

School of DentistryUniversity of Washington

Seattle, Washington

Private PracticeSeattle, Washington

Vincent O. Kokich Jr, DMD, MSDAffiliate Assistant Professor

Department of OrthodonticsSchool of Dentistry

University of WashingtonSeattle, Washington

Private PracticeTacoma, Washington

Abstract:Dentists often encounter patients with missing or malformed teeth. The maxillary lateral incisor is the sec-ond most common congenitally absent tooth. There are three treatment options that exist for replacingmissing lateral incisors. They include canine substitution, a tooth-supported restoration, or a single-toothimplant. Selecting the appropriate option depends on the malocclusion, specific space requirements, tooth-size relationship, and size and shape of the canine. The ideal treatment is the most conservative alternativethat satisfies individual esthetic and functional requirements. Often the ideal option is canine substitution.Although the orthodontist positions the canine in the most esthetic and functional location, the restora-tive dentist will often need to place a porcelain veneer or crown to re-create normal lateral incisor shapeand color. This article closely examines patient selection and illustrates the importance of interdisciplinarytreatment planning to achieve optimal esthetics. It is the first of a three-part series discussing the threetreatment alternatives for replacing missing lateral incisors.

CE

4 ADVANCED ESTHETICS & INTERDISCIPLINARY DENTISTRY SEPTEMBER 2007—VOLUME 3, NUMBER 3

Reprinted with permission from Journal of Esthetic and Restorative Dentistry, Volume 17, Number 1, 2005.

lateral excursive movements are in ananterior group function.2-5

Evaluation of the anterior tooth-sizerelationship is important when substi-tuting canines for lateral incisors. Theanterior tooth size excess that is creat-ed in the maxillary arch must often bereduced to establish a normal overbiteand overjet relationship.1 Therefore, acritical step in the patient-selection pro-cess is the completion of a diagnosticwax-up. This enables the orthodontistand dentist to evaluate the final occlu-sion, measure how much canine reduc-tion is necessary, and determine if anesthetic final result is achievable.4-6

PROFILEAfter one of the two occlusal criteria

has been satisfied, the profile should beevaluated. Generally, a balanced, rela-tively straight profile is ideal (Figure 3Aand Figure 3B). However, a mildly con-vex profile also may be acceptable (Figure4). A patient with a moderately convexprofile, retrusive mandible, and a defi-cient chin prominence may not be anappropriate candidate for canine substi-tution. A better alternative may be onethat addresses not only the dental mal-occlusion, but the facial profile as well.

CANINE SHAPE AND COLORThe shape and color of the canine are

important factors to consider for caninesubstitution to be considered esthetic.Naturally, the canine is a much largertooth than the lateral incisor it is replac-ing. With a wider crown and a more con-vex labial surface, a significant amountof reduction is often required for theorthodontist to achieve a normal oc-clusion and acceptable esthetics (Figure5). If a significant amount of enamelmust be removed to establish propersurface contours, the underlying dentinmay begin to show though the thin enam-el, thereby decreasing the esthetics.7 Ina canine with a greater degree of labialconvexity, dentin exposure can occurleading to the need for restorative inter-vention. Depending on the amount ofincisal edge wear of the canine, it may benecessary to restore the mesioincisal anddistoincisal edges to recreate normal

Figure 1A through Figure 1C Evaluation of specific dental and facial criteria is necessary whenselecting the appropriate patient for canine substitution.

Figure 3A and Figure 3B A balanced facial profile is ideal.

Figure 4 A mildly convex profile may also beacceptable.

Figure 2A and Figure 2B Maxillary canines erupting into the edentulous lateral incisor position (A).Class II molar relationship in canine substitution patients (B).

A B

C

A B

A B

Generally, the treatmentof choice should be theleast invasive option

that satisfies the expected esthetic andfunctional objectives.

6 ADVANCED ESTHETICS & INTERDISCIPLINARY DENTISTRY SEPTEMBER 2007—VOLUME 3, NUMBER 3

8 ADVANCED ESTHETICS & INTERDISCIPLINARY DENTISTRY SEPTEMBER 2007—VOLUME 3, NUMBER 3

lateral contours.2,8 The color of the nat-ural canine should also be addressedand should approximate that of thecentral incisor (Figure 6). However,it is not uncommon for the canine tobe more saturated with color, resultingin a tooth that is one to two shades dark-er than the central incisor. The mostconservative way to correct the color dif-ference is to individually bleach thecanine. If this fails to approximate thedesired color, a veneer may be indicated.

A significant amount of incisal andpalatal reduction is generally requiredfor the orthodontist to vertically posi-tion the canine in the appropriate later-al incisor location. Unfortunately, this ex-poses dentin, which occasionally requiresrestorative intervention. Zachrisson hasshown that extensive grinding using dia-mond instruments with abundant waterspray cooling can be performed on youngteeth without long-term changes in toothsensitivity. However, he found that short-term increases in tooth sensitivity werenoted with temperature changes for 1 to3 days after grinding.7,9

Finally, crown width at the cemen-to-enamel junction (CEJ) should beevaluated on the pretreatment periapi-cal radiograph to help determine thefinal emergence profile (Figure 7). Acanine with a narrow mesiodistal widthat the CEJ produces a more estheticemergence profile than one with awide CEJ width (Figure 8). The ideallateral incisor substitute is a canine thatis the same color as the central incisor,is narrow at the CEJ buccolinguallyand mesiodistally, and has a relativelyflat labial surface and narrow mid-crownwidth buccolingually.

LIP LEVELIf the patient has an excessive gingi-

va-to-lip distance on smiling, the gin-gival levels will be more visible. Thismay be due to a vertical maxillary ex-cess or a hypermobile lip. The gingivalmargin of the natural canine should bepositioned slightly incisal to the centralincisor gingival margin. This helps cam-ouflage the substituted canine. Occasion-ally, a gingivectomy may need to be per-formed to properly position the mar-

Figure 8 A narrow width at the CEJ produces amore esthetic emergence profile.

Figure 7 Radiographic evaluation of crownwidth at the CEJ.

Figure 10 The canine root eminence may beprominent.

Figure 6 The color of the canine and centralincisor crowns should match.

Figure 5 Significant reduction is often required toachieve an acceptable occlusion and ideal esthetics.

Figure 9A and Figure 9B Gingivectomy reestablishes proper gingival margin contours (A). Onemonth post-gingivectomy demonstrates nice gingival architecture (B).

Figure 11 Significant equilibration of the labialand palatal crown surfaces is often required.

A B

10 ADVANCED ESTHETICS & INTERDISCIPLINARY DENTISTRY SEPTEMBER 2007—VOLUME 3, NUMBER 3

ginal gingiva (Figure 9A and Figure 9B).The gingival margin of the first pre-molar is naturally positioned more coro-nally than the central incisor. If this isa concern to the patient, crown length-ening can be performed followed byplacement of a veneer to establish ide-al crown lengths and gingival margincontours. Finally, in patients with highsmile lines, a prominent canine rooteminence could also be an estheticconcern (Figure 10).5

TREATMENTProper bracket placement is impor-

tant when treating patients with caninesubstitution. The orthodontist shouldplace the brackets according to gingi-val margin height rather than incisaledge or cusp tip. Typically, the bracketson the canines should be placed at adistance from the gingival margin thatwill erupt these teeth into the appro-priate lateral incisor vertical position.As they erupt, a thicker portion of thecrown comes into contact with themandibular incisors (Figure 11). Thisoften causes prematurities that must beequilibrated periodically during the

alignment stage of orthodontic treat-ment. During finishing, the ortho-dontist must reduce the width of thecanine interproximally to achieve opti-mal esthetics and a normal overjet rela-tionship. After the teeth have beenaligned and the canines reshaped, thereis frequently a need for restorative treat-ment to recreate ideal lateral incisorcolor and contour. This may be ac-complished with bleaching, compositeresin, or a porcelain veneer. Generally,the treatment of choice is the most con-servative restoration that satisfies thepatient’s esthetic requirements. A step-wise simulation of the typical treat-ment sequence is shown in Figure 12Athrough Figure 12H.

SUMMARYCanine substitution can be an excel-

lent treatment alternative for congeni-tally missing maxillary lateral incisors.Patient selection depends on the type ofmalocclusion, profile, canine shape andcolor, and smiling lip level. Pre-treatmentevaluation of these selection criteria isnecessary to ensure treatment successand predictable esthetics.

The orthodontist typically plays thekey role in diagnosis and treatment ofthese patients. However, adjunctive res-torative treatment is often necessary torecreate ideal lateral incisor shape andcolor. Therefore, interdisciplinary treat-ment planning is necessary to achieveoptimal final esthetics.

REFERENCES1. Kokich VG. Managing orthodontic-restora-

tive treatment for the adolescent patient. InMcNamara JA, Brudon WL, eds. Orthodonticsand Dentofacial Orthopedics. 2001; AnnArbor, Michigan: Needham Press, Inc.

2. Zachrisson BU. Improving orthodontic re-sults in cases with maxillary incisors missing.Amer J Orthod. 1978;73(3):274-289.

3. Robertsson S, Mohlin B. The congentiallymissing upper lateral incisor. A retrospectivestudy of orthodontic space closure versusrestorative treatment. Eur J Orthod. 2000;22:697-710.

4. Tuverson DL. Orthodontic treatment usingcanines in place of missing maxillary lateralincisors. Amer J Orthod. 1970;58(2):109-127.

5. Senty EL. The maxillary cuspid and missinglateral incisors: Esthetics and occlusion. AngleOrthodontist. 1976;46:365-371.

6. Zachrisson BU, Rosa M. Integrating estheticdentistry and space closure in patients withmissing maxillary lateral incisors. J Clin Orthod.2001;35:221-234.

7. Zachrisson BU, Mjor IA. Remodeling of teeth bygrinding. Amer J Orthod. 1975;68(5):545-553.

8. Sabri R. Management of missing lateral inci-sors. J Am Dent Assoc. 1999;130:80-84.

9. Thordarson A, Zachrisson BU, Mjor IA. Re-modeling of canines to the shape of lateralincisors by grinding: A long-term clinical andradiographic evaluation. Amer J Orthod Dento-fac Orthop. 1991;100(2):123-132.

Figure 12A through Figure 12H Irregulargingival architecture (A). Incisal wear affectsproper crown width-to-length ratio (B).Orthodontic intrusion is necessary to facilitaterestorative lengthening of the central incisors(C). Provisional composite restorations complet-ed (D). Orthodontic extrusion of the canines (E).Ideal length of the canines as lateral incisors (F).Cuspal equilibration completed (G). Compositerestoration of the mesio-incisal corners (H).

A B C

D E F

G H

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1. The treatment options that exist forreplacing missing lateral incisors include: a. canine substitution.b. a tooth-supported restoration.c. a single-tooth implant.d. all of the above

2. The primary consideration among alltreatment plans should be:a. function.b. esthetics.c. conservation.d. cost.

3. The specific dental and facial criteria that mustbe evaluated before choosing canine substitu-tion as the treatment of choice for replacingmissing maxillary lateral incisors include:a. malocclusion and amount of crowding.b. canine shape and color.c. age and gender of the patient.d. a and b

4. How many types of malocclusions permitcanine substitution?a. oneb. twoc. threed. four

5. To establish a normal overbite and overjetrelationship, what must often be reduced?a. The teeth directly posterior to the malocclusion.b. The anterior tooth size excess that is created in

the maxillary arch. c. The posterior tooth size that is created in the

mandibular arch.d. The teeth directly anterior to the malocclusion.

6. Depending on the amount of incisal edgewear of the canine, it may be necessary torestore which edges to recreate normallateral contours?a. distolateral and mesiobuccalb. lingual and labialc. mesioincisal and distoincisald. distolingual and mesiobuccal-lingual

7. A significant amount of what reduction is gen-erally required for the orthodontist to verticallyposition the canine in the appropriate lateralincisor location?a. incisal and palatalb. lingual and labialc. incisal onlyd. labial only

8. The ideal lateral incisor substitute is a caninethat is the same color as the central incisor,narrow at the CEJ buccolingually andmesiodistally, and has a relatively flat labialsurface and narrow mid-crown width:a. mesiodistally.b. labially.c. buccolingually.d. mesio-occlusally.

9. The orthodontist should place thebrackets according to gingival marginheight rather than:a. incisal edge.b. cusp tip.c. lingual angle.d. a and b

10. Typically, the brackets on the canines shouldbe placed at a distance from what gingivalmargin that will erupt these teeth into theappropriate lateral incisor vertical position?a. labialb. lingualc. gingivald. interproximal

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