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Historically, dental students have beentaught that the incisal edge of the max-illary central incisors should extend

ap proximately 2.0 mm coronal to the upper lip,when the lip is in repose.1 This statement is cor-rect only if the patient has a horizontallystraight lip in repose.

This article examines 3 different commonlip phenotypes and the determination ofappropriate maxillary central incisor incisaledge position.

THREE LIP PHENOTYPES There are 3 basic lip phenotypes in humanswhen the maxillary lip is in repose.2,3 Anexample of each of the following 3 pheno-types is shown:

1. Straight lip (Figure 1).2. Moderately arched lip (Figure 2).3. Maximally arched lip (Figure 3).

Basic Rules for Incisal-PlaneDetermination

A basic rule of maxillary incisal-plane deter-mination is that there should be “some”tooth display when the upper lip is in re -pose.1 Otherwise, it looks as if the person hasno upper teeth, unless he or she is smiling.Only the lips-in-repose straight lip, however,can be used to help determine the idealincisal edge position of maxillary centralincisor teeth. If a patient has a moderatelyarched or maximally arched lip in repose,other guidelines must be used to determinethe incisal edge position, because 50% to100% of the maxillary incisor teeth may bedisplayed when the lips are in repose withthese latter 2 phenotypes.

Producing the Lips-in-Repose PositionThe lips-in-repose position is produced byhaving patients lick their lips and the facialsurfaces of their upper teeth, and then in -structing them to part their lips. Another wayto achieve this position is to instruct thepatient to say “hi” with a relaxed upper lipwithout smiling. These 2 methods relax theupper lip, allowing it to fall passively.

Restorative Tooth Position Versus Lip Position

As mentioned previously, there should almostalways be some tooth display with a straightlip in repose.1 In patients who present with notooth display, restoring 2.0 mm of tooth dis-play with lips in repose may feel unnatural,especially when enunciating an f or v sound.Those sounds are produced by placing theincisal edges of the maxillary anterior teeth incontact with the vermillion border of thelower lip.4 In these cases, especially in olderpatients, it may be necessary to leave thepatient in provisional restorations for a periodof time to allow the patient to adjust to theincreased length. Patient acceptance andaccommodation of the increased incisorlength almost always occurs, especially inwomen, because the new look is more youth-ful and attractive.

In cases of moderately or maximallyarched lips, other general rules must be uti-lized to determine ideal position when maxil-lary incisor teeth are being restored:

1. When the patient is smiling, the max-illary central incisors should be perceivedfrom a frontal view as the longest teeth in theincisal plane—longer than the lateral inci-

sors and cuspids.5 Even though the cuspidsare actually approximately the same lengthas the centrals when measured apicocoronal-ly from the cemento-enamel junction (CEJ) tothe incisal edge,6 the centrals should appearlonger because they should be at the apex ofthe u-shaped incisal plane arch (Figure 1b).

2. The average unworn maxillary centralincisor is approximately 11 mm long, fromthe CEJ to the incisal edge.6

3. The maxillary incisal plane should paral-lel the u or quarter-moon shape of the lower lip.3

4. Dominant central incisors present amore youthful and sexy look.

If these markers are plugged into theincisal-plane formula, optimal maxillary in -cisal edge position can be determined, evenwithout the aid of a straight lip in repose toassist. The optimal maxillary incisal planeshould also parallel the gingival line, theupper lip, and the pupillary line.3 Ideally, itshould also be parallel to the mandibularincisal plane, but this is not essential to estab-lish an attractive smile.

If the restored patient has an asymmetricalface, such that the left and right occlusal planesare also asymmetrical and not parallel to thepupillary line, always begin by paralleling theincisal edges of the restored maxillary centralincisors with the pupillary line. The incisalplane should then extend proportionately dis-tally to the lateral incisors and cuspids, and thento the occlusal plane of the posterior teeth, evenif the right and left sides of those planes are notparallel to the pupillary line and are not exactlythe same perceived length from a frontal viewdue to the patient’s facial asymmetry.

Figures 4 to 6 show 3 restorative pa tients,

Steven T.Cutbirth,DDS

Importance of Lip TypeClassification

Maxillary Central Incisor Length Determination Versus Lip Phenotype

RESTORATIVE

Figures 2a to 2c. (a) Moderately arched lip inrepose, (b) full smile, and (c) full-face smile.

Figures 3a to 3c. (a) Maximally arched lip inrepose, (b) full smile, and (c) full-face smile.

Figures 1a to 1c. (a) Straight lip in repose, (b) fullsmile, and (c) full-face smile.

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each representing one of the 3 lip phe-notypes. Views of before and after treat-ment are presented for each case withlips in repose, full smile, and full-facesmile.

Case 1: Straight lip (Figure 4).Case 2: Moderately arched lip (Fig -

ure 5).Case 3: Maximally arched lip (Fig -

ure 6).

IN SUMMARYMaxillary incisal-plane determinationshould be a definitive restorative proce-dure. One should consider the patient’slip phenotype, tooth length, and paral-lelism of the maxillary incisal plane,upper and lower lip lines, maxillary gin-gival line, and pupillary line. The maxil-lary central incisors should be perceivedas the longest teeth in the incisal planewhen observed from a frontal view. The3 basic maxillary lip phenotypes arestraight lip, moderately arched lip, andmaximally arched lip. Only the lips-in-repose straight lip can be used to assistin determining the optimal maxillarycentral incisal edge length.�

References 1. Morgan JP III, Haug RH. Evaluation of the cran-iomaxillofacial deformity patient. In: GreenbergAM, Prein J, eds. Craniomaxillofacial Recon -structive and Corrective Bone Surgery: Principles

of Internal Fixation Using the AO/ASIF Technique.New York, NY: Springer-Verlag; 2002:17.

2. Goldstein RE. Esthetics in Dentistry. Phila del -phia, PA: JB Lippincott; 1976.

3. Garber DA, Salama MA. The aesthetic smile:diagnosis and treatment. Periodontol 2000.1996;11:18-28.

4. Teaching sounds to children with speech delays.speechandlanguagekids.com/how-to-teach-a-new-sound. Accessed February 3, 2014.

5. Hasanreisoglu U, Berksun S, Aras K, et al. Ananalysis of maxillary anterior teeth: facial and den-tal proportions. J Prosthet Dent. 2005;94:530-538.

6. Magne P, Gallucci GO, Belser UC. Anatomic crownwidth/length ratios of unworn and worn maxillaryteeth in white subjects. J Prosthet Dent.2003;89:453-461.

Dr. Cutbirth practices restorative dentistry inWaco, Tex (wacosedationdentist.com), and isdirector of the Center for Aesthetic Restor -ative Dentistry (CARD) (centerforard.com),located in Dallas, a hands-on, complexrestorative teaching center for practicing den-tists. He graduated from Baylor DentalCollege in 1979, then completed a 2-year fel-lowship at Baylor, then was a member of theteaching faculty at the Pankey Institute inFlorida for 20 years. He has lectured andpublished extensively on the topics of sys-tematic restoration of the severely worn den-tition with vertical dimension increase, diag-nosis and treatment of occlusal problemsand facial pain, complex aesthetic restorativedentistry, ridge modification and bone graft-ing for small-diameter implant utilization, andthe most effective/productive dental practicesystem. He can be reached at (254) 772-5420 or at card1611@gmail.com.

Disclosure: Dr. Cutbrith is an occasional lec-turer for 3M ESPE but has received no com-pensation for the writing of this article.

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Before After

Figures 4a to 4f. (a) Straight lip phenotype—before: in repose; (b) full smile; (c) full-facesmile; (d) straight lip phenotype—after: in repose; (e) full smile; and (f) full-face smile.

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Before After

Figures 5a to 5f. (a) Moderately arched lip phenotype—before: in repose; (b) full smile;(c) full-face smile; (d) moderately arched lip phenotype—after: in repose; (e) full smile;and (f) full-face smile.

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Before After

Figures 6a to 6f. (a) Maximally arched lip phenotype—before: in repose; (b) full smile; (c) full-face smile; (d) maximally arched lip phenotype—after: in repose; (e) full smile; and (f) full-face smile.