Principles of Esthetics












21
Principles of
Esthetics
2
The term esthetic is used to connote that something seen is pleasant. The goal of an esthetic makeover
is to develop a beautiful smile and a peaceful and stable masticatory system where the teeth, tissues,
muscles, skeletal structures, and joints all function in harmony. The part of the mouth where high
visibility requires restorations or tooth replacement to acquire a pleasant smile is called the esthetic
zone. This typically includes the maxillary anterior teeth and premolars and frequently extends to
include the rst molars, yet teeth are not the only factor at play aecting dental facial esthetics, also
known as smile design. Several other factors should be taken into consideration, including facial and
lip anatomy, periodontal health, and the interrelationship of the supporting oral structures.
9,10
Smile design has become a very popular practice in dentistry, especially with the advancement in
ceramics in recent decades, which makes it crucial to introduce dental students to the principles of
esthetics as early as possible to be able to comply with this practice. Fabricating an esthetic wax-up
is an excellent exercise to apply those concepts and has become an important part of the dental
anatomy curriculum. It is important to realize that dental facial esthetics is a very broad topic, and
there are several comprehensive textbooks that provide in-depth details as well as ongoing research
of the parameters and perception of a beautiful smile because this can be subject to change with
dierent times and in dierent populations, genders, and races. This chapter oers an introduction
and wide coverage of the basic principles needed for creating an esthetic wax-up on mounted casts.
When planning a new smile, the factor that can be mostly controlled by the dentist is the anterior
teeth. This may include form, size, and shade and is also referred to as dental esthetics or micro-
esthetics. Other factors such as facial form and balance, gingival esthetics, lips, and symmetry are
not entirely under the control of the dentist but do aect the choice of teeth and may have a drastic
eect on the nal outcome. For a beautiful smile, the teeth should be in harmony with the face, lips,
and gingiva, and these interrelationships are classied as macroesthetics.
11

Principles of Esthetics
22
2
Achieving Harmony with the Face
11–13
Evaluation of the shape of the face
The basic shape of the face may be square, tapering, or ovoid (Fig 2-1), and sometimes the shape of
the face may fall between two of these categories (eg, square tapering). The importance of noticing
the shape of the face is to match the anterior tooth form to that of the face. Other factors should still
be considered when deciding the form of the teeth, such as age, gender, and personal preference. For
example, a young male with a square facial form would be ideally matched with long square teeth,
and a female with an ovoid face is ideally matched with round or ovoid teeth.
Fig 2-1
Square
Square tapering Tapering Ovoid
Evaluation of the proportions of the face in horizontal and vertical dimensions
A proportionate face may be divided vertically
into fths, each approximately the width of one
eye (Fig 2-2a), and horizontally into thirds (Fig
2-2b). The top third is from the hairline to the
top of the eyebrows. The middle third is from
the top of the brows to the bottom of the nose.
The bottom third is from the bottom of the nose
to the chin. Esthetic balance is considered ideal
when the facial features fall within these param-
eters. When designing a smile, these proportions
should be noted and taken into consideration to
decide the type of treatment needed to produce
the desired esthetic changes and to have realistic
expectations of the treatment outcome.
Fig 2-2
a
b

Achieving Harmony with the Face
23
Lateral prole of the face
An individual’s lateral prole can be straight, concave, or convex (Fig 2-3). This depends on the rela-
tionship of the maxilla to the mandible and on the degree of prominence of certain facial features,
such as the lips, nose, and chin. Prole convexity or concavity may also result from disproportion in
the size of the jaws. For example, a concave facial prole may result from an oversized mandible and/
or an undersized maxilla. Changing the lateral prole is mostly done by surgical procedures that alter
the size or position of the maxilla and/or mandible or plastic surgery to alter the shape of the nose or
lips. When attempting to improve a patient’s dental esthetics, the lateral prole has to be considered
to direct the patient to the proper treatment approach. A collaboration between the orthodontist,
oral surgeon, and plastic surgeon is needed in severe discrepancies.
Fig 2-3 
Fig 2-4 The interpupillary line is perpendicular to the
facial midline and parallel to the occlusal plane and
gingival margins of the central incisors.
Convex
Straight
Concave
Facial features aecting smile design
Interpupillary line
The interpupillary line is an imaginary line drawn
between the centers of the pupils of the eyes. The
interpupillary line should be perpendicular to the
midline of the face and parallel to the gingival
margins of the central incisors and to the occlu-
sal plane to achieve facial harmony (Fig 2-4).
Midline
The midline is an imaginary line coinciding with
the median plane that passes longitudinally
through the middle of the body from front to back,
dividing it into the right and left halves. There are
three midlines considered in esthetics: the facial
midline and the maxillary and mandibular dental
midlines. The facial midline is dened by land-
marks such as the nose, philtrum, and chin aligned
in a straight line and is ideally in the center of the

Principles of Esthetics
24
2
face. The more centralized the facial midline, the
more inherently harmonious and beautiful the
face is. The dental midline is the midsagittal line of
maxillary and mandibular arches when teeth are
in maximal intercuspation. In a totally symmetric
face, the dental midlines and the facial midline
should coincide, but this is often not the case. In
fact, the maxillary arch midline coincides with the
facial midline in 50% to 70% of the population,
and the maxillary and mandibular arch midlines
coincide in only 25% of the population. Therefore,
the mandibular midline rarely coincides with the
facial midline, but this mismatch does not aect
esthetics much because mandibular teeth are not
usually visible while smiling. However, mismatch
between facial midline and maxillary midline
may have a negative eect on esthetics. There
is a general agreement in the literature that the
maximum midline deviation should not exceed 2
mm to maintain a pleasant smile
12
(Fig 2-5).
Fig 2-5 Shift in maxillary dental midline.
Facial
midline
Dental midline
Achieving Harmony with the Lips
Lips create the boundaries of the smile. The
width, fullness, and symmetry of the lips have
a prominent eect on the beauty of a smile. The
upper lip is usually wider and longer than the
lower lip because the maxillary arch overlaps
the mandibular arch. This makes the lower lip
recessed beneath the upper lip by approximately
30 degrees when the arches are properly aligned.
The relationships between the lips to each other
and to the rest of the face can be analyzed by
using the esthetic plane or the E line. This is
simply a line drawn in the lateral view from the
tip of the nose to the tip of the chin. In an average
face, the lower lip is 2 mm behind the E line, and
the upper lip is 4 mm behind the E line (Fig 2-6).
This should be recognized during smile design as
it aects anterior teeth selection. If the lips are
closer to the E line, the lips and teeth will dominate
the smile, and the nose and chin eect will be
minor, so larger teeth and brighter shades should
be avoided to achieve balance. The opposite also
Fig 2-6 E line.

Achieving Harmony with the Lips
25
holds true: If the lips are farther behind the E line, the nose and chin will dominate the smile, and
therefore larger and brighter teeth are a wiser choice to improve balance with the rest of the face.
14
It is generally considered that fuller, more prominent lips are perceived as more youthful and
therefore more desirable from an esthetic viewpoint, and that wider lips resulting in a wide smile
that is at least half the width of the face is more esthetic compared to a narrower smile. Recognizing
lips anatomy is an important step in smile design, as it determines if an alternative treatment option
should be performed, such as orthodontics to correct anterior teeth inclination that aects lip support
and prominence, or the need for plastic surgery in conjunction with the anterior restorations to reach
the desired outcome. Generally, the thicker the upper lips the smaller the teeth will appear, so if a
patient is considering enhancing the thickness of their lips, this should be done before the dental
procedures rather than after.
13,14
Factors aecting harmony between teeth and lips
11–17
The relationship of maxillary incisal edge positions to the lower border of the upper lips during rest
normally ranges from 2 to 4 mm in younger patients and decreases with age (Fig 2-7).
Buccal corridor
The buccal corridor is the dark space that appears between the buccal surfaces of posterior teeth
and the interior portion of the commissure of the lips during smiling. The teeth are silhouetted
against this dark space due to the color contrast (Fig 2-8). A well-formed buccal corridor produces
the natural appearance of the smile and adds to its depth and attractiveness. The buccal corridor is
aected by other factors such as width of the smile and the maxillary arch; metal restorations; and
fractured, missing, or malpositioned teeth. The lack of a buccal corridor may result in the appearance
of a fake-looking smile.
11
Fig 2-7 
Fig 2-8 Buccal corridors (arrows).
Lip symmetry
Lip symmetry refers to the mirror image appearance of each lip. This involves the actual symmetric
form of the lips at rest and during smiling. While the symmetry of the lips at rest depends on the
natural individual anatomical form, symmetry during smiling depends on the balance in the action
of the facial muscles involved in smiling on the right and left sides. If this balance is disturbed, which
could occur naturally and have a minimal eect or could be more aggressive due to conditions such
as Bell’s palsy (facial paralysis), the result is an asymmetric smile, uneven dental and/or gingival
display, and disruption of the buccal corridor.

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21Principles of Esthetics2The term esthetic is used to connote that something seen is pleasant. The goal of an esthetic makeover is to develop a beautiful smile and a peaceful and stable masticatory system where the teeth, tissues, muscles, skeletal structures, and joints all function in harmony. The part of the mouth where high visibility requires restorations or tooth replacement to acquire a pleasant smile is called the esthetic zone. This typically includes the maxillary anterior teeth and premolars and frequently extends to include the rst molars, yet teeth are not the only factor at play aecting dental facial esthetics, also known as smile design. Several other factors should be taken into consideration, including facial and lip anatomy, periodontal health, and the interrelationship of the supporting oral structures.9,10Smile design has become a very popular practice in dentistry, especially with the advancement in ceramics in recent decades, which makes it crucial to introduce dental students to the principles of esthetics as early as possible to be able to comply with this practice. Fabricating an esthetic wax-up is an excellent exercise to apply those concepts and has become an important part of the dental anatomy curriculum. It is important to realize that dental facial esthetics is a very broad topic, and there are several comprehensive textbooks that provide in-depth details as well as ongoing research of the parameters and perception of a beautiful smile because this can be subject to change with dierent times and in dierent populations, genders, and races. This chapter oers an introduction and wide coverage of the basic principles needed for creating an esthetic wax-up on mounted casts.When planning a new smile, the factor that can be mostly controlled by the dentist is the anterior teeth. This may include form, size, and shade and is also referred to as dental esthetics or micro-esthetics. Other factors such as facial form and balance, gingival esthetics, lips, and symmetry are not entirely under the control of the dentist but do aect the choice of teeth and may have a drastic eect on the nal outcome. For a beautiful smile, the teeth should be in harmony with the face, lips, and gingiva, and these interrelationships are classied as macroesthetics.11 Principles of Esthetics222Achieving Harmony with the Face 11–13Evaluation of the shape of the faceThe basic shape of the face may be square, tapering, or ovoid (Fig 2-1), and sometimes the shape of the face may fall between two of these categories (eg, square tapering). The importance of noticing the shape of the face is to match the anterior tooth form to that of the face. Other factors should still be considered when deciding the form of the teeth, such as age, gender, and personal preference. For example, a young male with a square facial form would be ideally matched with long square teeth, and a female with an ovoid face is ideally matched with round or ovoid teeth.Fig 2-1SquareSquare tapering Tapering OvoidEvaluation of the proportions of the face in horizontal and vertical dimensionsA proportionate face may be divided vertically into fths, each approximately the width of one eye (Fig 2-2a), and horizontally into thirds (Fig 2-2b). The top third is from the hairline to the top of the eyebrows. The middle third is from the top of the brows to the bottom of the nose. The bottom third is from the bottom of the nose to the chin. Esthetic balance is considered ideal when the facial features fall within these param-eters. When designing a smile, these proportions should be noted and taken into consideration to decide the type of treatment needed to produce the desired esthetic changes and to have realistic expectations of the treatment outcome.Fig 2-2ab Achieving Harmony with the Face23Lateral prole of the faceAn individual’s lateral prole can be straight, concave, or convex (Fig 2-3). This depends on the rela-tionship of the maxilla to the mandible and on the degree of prominence of certain facial features, such as the lips, nose, and chin. Prole convexity or concavity may also result from disproportion in the size of the jaws. For example, a concave facial prole may result from an oversized mandible and/or an undersized maxilla. Changing the lateral prole is mostly done by surgical procedures that alter the size or position of the maxilla and/or mandible or plastic surgery to alter the shape of the nose or lips. When attempting to improve a patient’s dental esthetics, the lateral prole has to be considered to direct the patient to the proper treatment approach. A collaboration between the orthodontist, oral surgeon, and plastic surgeon is needed in severe discrepancies.Fig 2-3 Fig 2-4 The interpupillary line is perpendicular to the facial midline and parallel to the occlusal plane and gingival margins of the central incisors.ConvexStraightConcaveFacial features aecting smile designInterpupillary lineThe interpupillary line is an imaginary line drawn between the centers of the pupils of the eyes. The interpupillary line should be perpendicular to the midline of the face and parallel to the gingival margins of the central incisors and to the occlu-sal plane to achieve facial harmony (Fig 2-4).MidlineThe midline is an imaginary line coinciding with the median plane that passes longitudinally through the middle of the body from front to back, dividing it into the right and left halves. There are three midlines considered in esthetics: the facial midline and the maxillary and mandibular dental midlines. The facial midline is dened by land-marks such as the nose, philtrum, and chin aligned in a straight line and is ideally in the center of the Principles of Esthetics242face. The more centralized the facial midline, the more inherently harmonious and beautiful the face is. The dental midline is the midsagittal line of maxillary and mandibular arches when teeth are in maximal intercuspation. In a totally symmetric face, the dental midlines and the facial midline should coincide, but this is often not the case. In fact, the maxillary arch midline coincides with the facial midline in 50% to 70% of the population, and the maxillary and mandibular arch midlines coincide in only 25% of the population. Therefore, the mandibular midline rarely coincides with the facial midline, but this mismatch does not aect esthetics much because mandibular teeth are not usually visible while smiling. However, mismatch between facial midline and maxillary midline may have a negative eect on esthetics. There is a general agreement in the literature that the maximum midline deviation should not exceed 2 mm to maintain a pleasant smile12 (Fig 2-5).Fig 2-5 Shift in maxillary dental midline.Facial midlineDental midlineAchieving Harmony with the LipsLips create the boundaries of the smile. The width, fullness, and symmetry of the lips have a prominent eect on the beauty of a smile. The upper lip is usually wider and longer than the lower lip because the maxillary arch overlaps the mandibular arch. This makes the lower lip recessed beneath the upper lip by approximately 30 degrees when the arches are properly aligned. The relationships between the lips to each other and to the rest of the face can be analyzed by using the esthetic plane or the E line. This is simply a line drawn in the lateral view from the tip of the nose to the tip of the chin. In an average face, the lower lip is 2 mm behind the E line, and the upper lip is 4 mm behind the E line (Fig 2-6). This should be recognized during smile design as it aects anterior teeth selection. If the lips are closer to the E line, the lips and teeth will dominate the smile, and the nose and chin eect will be minor, so larger teeth and brighter shades should be avoided to achieve balance. The opposite also Fig 2-6 E line. Achieving Harmony with the Lips25holds true: If the lips are farther behind the E line, the nose and chin will dominate the smile, and therefore larger and brighter teeth are a wiser choice to improve balance with the rest of the face.14It is generally considered that fuller, more prominent lips are perceived as more youthful and therefore more desirable from an esthetic viewpoint, and that wider lips resulting in a wide smile that is at least half the width of the face is more esthetic compared to a narrower smile. Recognizing lips anatomy is an important step in smile design, as it determines if an alternative treatment option should be performed, such as orthodontics to correct anterior teeth inclination that aects lip support and prominence, or the need for plastic surgery in conjunction with the anterior restorations to reach the desired outcome. Generally, the thicker the upper lips the smaller the teeth will appear, so if a patient is considering enhancing the thickness of their lips, this should be done before the dental procedures rather than after.13,14Factors aecting harmony between teeth and lips11–17 The relationship of maxillary incisal edge positions to the lower border of the upper lips during rest normally ranges from 2 to 4 mm in younger patients and decreases with age (Fig 2-7).Buccal corridorThe buccal corridor is the dark space that appears between the buccal surfaces of posterior teeth and the interior portion of the commissure of the lips during smiling. The teeth are silhouetted against this dark space due to the color contrast (Fig 2-8). A well-formed buccal corridor produces the natural appearance of the smile and adds to its depth and attractiveness. The buccal corridor is aected by other factors such as width of the smile and the maxillary arch; metal restorations; and fractured, missing, or malpositioned teeth. The lack of a buccal corridor may result in the appearance of a fake-looking smile.11Fig 2-7 Fig 2-8 Buccal corridors (arrows).Lip symmetryLip symmetry refers to the mirror image appearance of each lip. This involves the actual symmetric form of the lips at rest and during smiling. While the symmetry of the lips at rest depends on the natural individual anatomical form, symmetry during smiling depends on the balance in the action of the facial muscles involved in smiling on the right and left sides. If this balance is disturbed, which could occur naturally and have a minimal eect or could be more aggressive due to conditions such as Bell’s palsy (facial paralysis), the result is an asymmetric smile, uneven dental and/or gingival display, and disruption of the buccal corridor. Principles of Esthetics262Smile lineSmile line is dened as the relationship of the maxillary incisal edge positions to the lower border of the upper lip during smiling. This determines the display of maxillary teeth and/or gingiva. Tjan and Miller classied the smile line into high, aver-age, and low.15 A high smile line exposes the entire length of the teeth as well as part of the gingiva above the gingival margin; an average smile line reveals the teeth and the interdental papilla; and a low smile line displays only part of the maxillary anterior teeth with a lack of any gingival display (Fig 2-9). Regarding tooth display, a smile is considered optimum if it displays the full clinical crowns of the six maxillary anterior teeth as well as the premolars from a frontal view. The smile line is usually considered acceptable if it is within a range of 2 mm apical to the height of the gingiva on the maxillary central incisors. If more gingival display exists, as in a high smile line, the results become unpleasant; the term gummy smile is used to describe these cases, and corrective peri-odontal surgeries become needed in conjunction with restorative procedures. Both average and low lip lines may result in desirable esthetics, although patients with low smile lines oer less of a treatment challenge, as discrepancies in the gingival margin in relation to the teeth as well as gingival recession —especially at the interdental papilla, causing black triangles—are not revealed upon smiling.Smile arcSmile arc is dened as the relationship between the curvature of the incisal edges of the maxillary ante-rior teeth and the curvature of the upper border of the lower lip during smiling. In an esthetic smile, both curvatures should be parallel to each other, making the smile arc convex. Proper form, align-ment, and lengths of the maxillary anterior teeth are needed to achieve this result. The incisal edges of central incisors and cusp tips of canines typi-cally lie on the same curved line, while the incisal edges of lateral incisors are about 1 mm above the Fig 2-9 Smile lines: (a) high, (b) average, and (c) low.Fig 2-10 (a) Smile arc (central incisors and canines lie on the same line). (b) Convex smile arc in an esthet-ic wax-up (lateral incisors lie above the smile arc).aabbcsame line (Fig 2-10). A smile arc that is rather at or reversed (concave) due to malaligned or missing teeth results in undesirable esthetics9,11 (Fig 2-11). Dental Esthetics (Microesthetics)27Achieving Harmony with the GingivaTwo aspects are in consideration with regard to gingival esthetics: (1) gingival health and (2) gingi-val architecture. Healthy gingiva should be pink, stippled, and rm and exhibit a matte surface. The interdental papillae should be pointed and ll the embrasures to the contact point between the teeth; recession in the interdental papilla leads to the appearance of black triangles between the teeth, which are esthetically unpleasant. The gingival architecture should be symmetric. The collar of the gingiva that surrounds teeth is called the marginal gingiva. The line that connects the marginal gingiva of the maxillary anterior teeth (gingival line) is usually not a straight line. Ideally the canines and the central incisors lie on the same line, and the lateral incisors are slightly incisal to this line. The gingival line should be symmetric and should be parallel to the interpupillary line. Another aspect that should be noted is the gingival zenith. This is the most apical point of the marginal gingiva, which is located distal to the long axis on the maxillary central incisors and canines and along the axes of the maxillary lateral incisors and mandibular incisors due to the relative angulations of these teeth9,11 (Fig 2-12). Dental Esthetics (Microesthetics)Alignment of teeth4,12Properly aligned teeth are a major contributor in achieving the ideal smile. In addition to the angula-tions of the root axis line in the frontal and lateral views discussed in chapter 1, we have to analyze the angulations of the long axes of the crowns of the anterior teeth, which is the same as the root axis line angulation only from the lateral view (incisal portion of the crowns are labial to the gingival portion). Tooth angulation from a lateral view represents the faciolingual alignment of teeth and determines the soft tissue support, lip prominence, and facial prole as well as the appearance of the teeth or microesthetics. For beautiful esthetics, the anterior teeth are facially inclined with their root apices toward the lingual (the maxillary teeth are slightly more inclined than the mandibular). If this angulation is decreased, the lips become less supported and therefore less esthetic, and the nose and chin will dominate the smile. On the other extreme, if the angulation is increased too much, this results in protruded incisors and increased incisal display, causing the smile to be unpleasant as Fig 2-11 Flat smile arc due to same length of lateral and central incisors.Fig 2-12 Gingival zenith. Principles of Esthetics282Morphology of anterior teeth5,6,10The morphologic components of anterior teeth that are apparent upon smiling include labial surfaces, incisal ridges, canine cusp tips and ridges, incisal embrasures, and interproximal contact areas.Labial surfaces of anterior teeth are smooth and slightly convex in a mesiodistal and cervicoincisal direction with the height of contour occurring in the cervical third and extending approximately 0.5 mm labially. Anterior teeth are formed of four developmental lobes (growth centers). The lingual lobe is represented by the cingulum forming the height of contour at the lingual surface, and the three facial lobes are represented by the mamelons, which are three rounded elevations on the incisal edges that appear in the newly erupted teeth and wear away with function but are not a feature of the adult permanent dentition. The middle lobe may be overpronounced, forming a slight elevation in the center of anterior teeth. In the canines, the middle lobe is more pronounced than in the incisors, resulting in their quite convex appearance. The labial surfaces are bounded by the mesiolabial and distolabial line angles, which are slightly rounded, with the distolabial line angle being more convex. As a result of the convexity in the center of anterior teeth produced by the middle lobe and the convex well as increasing the chance of trauma to the maxillary incisors. From the frontal view, the long axes of crowns are distally inclined, making the incisal portion mesial to the gingival portion of the crown. This is opposite the angulation of the root axis lines of these teeth, which tends to be mesially inclined, meaning that even though the entire tooth is angulated mesially as determined by the root axis line, the crown is angulated distally in relation to the root and to the midline of the tooth. Naturally, this distal inclination of the anterior crowns as seen from a frontal view should increase progressively from the central incisors to the canines (ie, it should be least noticeable with the central incisors; Fig 2-13). Another component to be considered regarding the vertical alignment of anterior teeth is the relationship to the midline, which plays a major role in esthetics. It was discussed earlier that a dental midline shifted from the facial midline by 2 mm or less may pass unnoticed. This is true as long as the central incisors are aligned vertically with their incisal plane parallel to the interpupillary line (see Fig 2-4). Lack of proper vertical alignment of maxillary anterior teeth resulting in a canted midline is more esthetically unpleasant than a midline shift. Several studies show that attractiveness scores and acceptability ratings decline consistently as axial midline angulation increases. Proper diagnosis and clinical examination should be completed to detect the possible presence of a canted midline. Factors that may aect alignment and angulations of teeth such as malocclusion, missing teeth, or crowded arch can all negatively aect esthetics and result in a poor smile.Fig 2-13 (a) Axial inclination of crowns from the frontal view. (b) Anterior teeth angulations summary.baMDVertical lineRoot axis lineCrown axis lineFL Dental Esthetics (Microesthetics)29Fig 2-14 (a) Developmental depression in an extracted central incisor. (b) Esthetic wax-up with developmental depressions.Fig 2-15 (a) Extracted central incisor with no developmental depressions. (b) Esthetic wax-up with no developmental depressions.bbaaline angles at the borders, two shallow depressions appear mesial and distal to the middle lobe of the tooth (Fig 2-14). It is important to remember that the prominence of the middle lobe and hence the adjacent developmental depressions may not be apparent in every dentition, and in many cases the labial surface can be smooth between the line angles (Fig 2-15). In anterior restorations and esthetic wax-ups, these features are reproduced if they exist on the contralateral and adjacent teeth or whenever it is found more esthetically pleasing.Incisal edges, also known as incisal ridges, are normally thin and nicely rounded in an unworn dentition (Fig 2-16a). Incisal edges may become thicker due to attrition from aging, malocclusion, or parafunctional habits such as bruxism and clenching. The thin incisal edge wears down and exposes a thicker area on the tooth, resulting in the tooth becoming shorter with a attened, thicker edge. This is commonly associated with an older age appearance (Fig 2-16b).Incisal edges may have dierent size/form according to the tooth type, as follows: The maxillary central incisor has the widest incisal edge, being the widest anterior tooth, and is very straight mesiodis-tally. The maxillary lateral incisor has a more rounded incisal edge as the tooth is smaller and has a more convex general outline. The mandibular central incisor has a very straight and symmetric yet small incisal edge because it is the smallest tooth in the mouth. Finally, the mandibular lateral incisor has an incisal edge that seems to be rotated distally due to the rotation of the crown on the root of the tooth to Fig 2-16 (a) Unworn incisal edge. (b) Incisal edge showing attrition.ba Principles of Esthetics302follow the arch curvature, and the incisal edge is wider and less symmetric than that of the mandibular central incisor (Fig 2-17). From an incisal view, incisal edges resemble a rectangle wide mesiodistally and narrow labiolingually with the corners being the point angles. The distoincisal angle is always more rounded than the mesioincisal one, except in the mandibular central incisors, as these teeth are very symmetric and both point angles may approach 90 degrees (Fig 2-18). The incisal edges of maxillary anterior teeth do not normally contact the opposing teeth in maximal intercuspation, but mandibular incisal edges may have light contact with the lingual surface of the maxillary anterior teeth. In addition to their eect on esthetics, incisal edges enable the anterior teeth to have a direct and indirect eect on masticatory function. The direct eect is providing a means for the anterior teeth to incise and bite food, and the indirect eect is due to their role in guiding the mandible in protrusion, which protects the posterior teeth from horizontal damaging forces and therefore facilitates their masticatory function (anterior guidance).Fig 2-17 Incisal edges morphology.Fig 2-18 (a) Incisal edges are rectangular from the incisal view with point angles at the corners (arrows point to labial developmental depressions). (b) Incisal view of esthetic wax-up; note the distoincisal point angles are more rounded than the mesioincisal point angles.baRoundWidestRotatedSymmeticSmallestIncisal edge positionThe factors considered when positioning the incisal edges in smile design are degree of tooth display, phonetics, occlusion, relative tooth dimensions, and patient preference. The maxillary central incisal edges are the rst to be located on an esthetic wax-up and provide a guide for the remainder of the anterior teeth. Ideally, they should be placed against the inner edge of the vermillion border at the wet-dry line of the lower lip when the patient pronounces the letter “F” and achieve tooth display of 2 to 4 mm at rest in an upright position in younger patients. In addition, contact between maxillary and mandibular incisal edges in protrusion should separate posterior teeth on the mounted casts. The maxillary lateral incisal edges are positioned 1 to 1.5 mm shorter than the central incisal edges. The mandibular incisal edges are positioned behind the maxillary incisors and establish occlusal contact with their lingual surfaces, thus achieving appropriate overjet and overbite. In younger patients, none or little is seen of the mandibular incisors at rest, but aging and tissue sagging due to gravitational eects result in more mandibular display, reaching about 2 to 3 mm by age 60. This eect is the opposite to the aging eect on maxillary incisal display, whereby tissue sagging diminishes tooth display gradually until none of the maxillary incisal edges can be seen by age 60. The correct incisal edge position is therefore crucial because it aects smile esthetics, anterior guidance, and proper pronunciation (Fig 2-19). Dental Esthetics (Microesthetics)31Canine cusps and cusp ridgesCanines have one strong prominent cusp. The distal cusp ridge is longer than the mesial cusp ridge in both maxillary and mandibular canines, making the cusp tip oset to the mesial side (Fig 2-20a). The labial cusp ridge is quite prominent and runs on the labial surface of the canines, giving them a convex appearance in both mesiodistal and incisocervical directions (Fig 2-20b). These features should be perfected in esthetic wax-ups for a natural appear-ance (Fig 2-20c). Canines are the strongest teeth in the mouth. They serve an essential role in esthet-ics by supporting the soft tissue and muscles at the corner of the arch. When a maxillary canine is extracted, this results in sunken tissue and aging appearance. During an esthetic wax-up, the canine cusp tip position depends on a balance between the amount of tooth display as well as occlusion. Ideally the maxillary canine cusp tip falls on the smile arc on the same point as the maxillary central incisal edges (see Fig 2-10) and should allow the disocclusion of posterior teeth in lateral movement to achieve canine guidance. EmbrasuresEmbrasures are the V-shaped spaces between the teeth that allow the escape of food, which essentially reduces food impaction and improves masticatory function. Incisal embrasures are located toward the incisal edge and terminate at the interproximal contact point. Their shapes and sizes are important in achieving natural esthetics and should be reproduced precisely in an esthetic wax-up. For beautiful esthetics, incisal embrasures should become progressively larger posteriorly. Therefore, the embrasure is minimal between the two central incisors, larger between the central and lateral incisors, and largest between the lateral incisor and canine (Fig 2-21). This can be easily achieved during waxing by proper reproduction of the interprox-imal contact location and the incisal edge height and form as well as perfecting the point angles to the correct rounding. If these embrasures are Fig 2-19 Incisal edge position is important to pho- netics, function, and esthetics.Fig 2-20 (a) Canine cusp and cusp ridges. (b) Max-illary canine labial ridge making the tooth convex me-siodistally and incisocervically. (c) Marking the canine labial ridge during an esthetic wax-up to guide nal carv-ing and contouring.a bcD Mmade uniform, this results in an unnatural smile with interproximal contacts that are too long and produces a box-shaped appearance of teeth.17 Principles of Esthetics322Interproximal contact areaInterproximal contact area is dened as the broad zone in which two adjacent teeth touch, bounded by the apex of the V-shaped gingival embrasure at the gingival end and the apex of the incisal embra-sures at the incisal end. Interproximal contact areas ideally follow the 50:40:30 rule in reference to the maxillary central incisor: Ideal proximal contact area between central incisors is about 50% of the length of the central incisors, between central and lateral incisors is about 40% the length of the central incisors, and between the lateral incisor and the canine is about 30% the length of the central incisors 9 (Fig 2-22). Interproximal contacts may inuence dental esthetics by aecting the size of the embrasures as follows: Extending the interproximal contact areas gingivally decreases the size of the gingival embrasures and can help reduce or eliminate black triangles that may appear due to gingival recession, and extending the interproximal contacts further incisally reduces the size of the incisal embrasures. Interproximal contacts may also aect esthetics by creating an optical illusion whereby the teeth appear longer if the interproximal contact areas were increased and shorter if the interproximal contact areas were decreased.17Fig 2-21Fig 2-22 bbaaSize of teeth/Tooth dimensions9,16 Several factors are considered when establishing tooth dimensions (incisocervical length, mesiodistal width, and labiolingual depth); these factors include phonetics, occlusion, the amount of tooth display as guided by the lips and the smile arc as discussed earlier, the general average tooth measurements as well as the ratio between the length and the width of each individual tooth, and the relationship between the lengths and widths of teeth to each other. Dental Esthetics (Microesthetics)33Maxillary central incisors are the focal point of an esthetic smile and create the central dominance. Therefore, discrepancies in the central incisors are the most noticeable and aect esthetics negatively more than the rest of the anterior teeth. Maxillary central incisors are the widest of all anterior teeth with the smallest maxillary mesioincisal embrasure. They express an individual’s age through the incisal edge morphology. Children with newly erupted central incisors will have mamelons; younger adults’ incisal edges are straight, nicely rounded, and relatively thin with no mamelons; and older individuals will exhibit wear, resulting in atter, thicker edges. During an esthetic wax-up, the central incisors should be the rst teeth waxed because their size and form act as a guide for waxing the remaining teeth. The general average length of the maxillary central incisor is 10 to 11 mm, and the width is 75% to 80% of its length. An alteration in this ratio may result in the appearance of the central incisors as too wide or too long, which is very esthetically unpleasant.Maxillary lateral incisors are considered the playful part of the smile and are often asymmetric. They provide individuality and gender characterization by their curvatures. Straight line angles and relatively sharper incisal edges denote masculinity, while convex point and line angles with a round incisal edge denote femininity. Lateral incisors are the narrowest maxillary anterior teeth mesiodis-tally, and their lengths are usually 1 to 1.5 mm shorter than the central incisors; therefore, they do not touch the smile arc and exhibit less wear with aging compared to the central incisors and canines due to diminished occlusal contact.Maxillary canines play a critical point in creating a pleasing smile as they are the junction between the anterior and posterior dental segments and provide support to the corner of the mouth. Canines denote vigor and personality characterization. Masculine canines are aggressive with a sharper cusp tip, and feminine canines exhibit a more rounded cusp tip. For an esthetically pleasing smile, the canines should be the same length as the maxillary central incisors (Fig 2-23).Fig 2-23 Redrawn from Goldstein.16VigorousMasculineYoungFeminineSoftAgedPersonalityGenderAgeEstablishing tooth width17,18We must dierentiate between the actual width and the apparent width. The actual width can be assessed from a facial view of each tooth. The central incisors are the widest anterior teeth, followed by the canines and then the lateral incisors. The central incisor is usually wider than the canine by 1 to 1.5 mm and the lateral incisor by 2 to 3 mm, and the canine is wider than the lateral incisor by 1 to 1.5 mm.9 The apparent width, however, is assessed from the frontal view of the face. Teeth appear to be progressively narrower the farther they are from the midline; therefore, the canines appear to be the narrowest anterior teeth. Principles of Esthetics342The discrepancy between the actual and the apparent width is explained by the tooth position along the curve of the maxillary arch. One of the popular suggested ratios to follow when establishing tooth widths in esthetic wax-ups and smile design is the golden proportion, which states that the lateral incisor apparent width accounts for 62% of the central incisor width, while the canine apparent width accounts for 62% of the lateral incisor width. However, applying the golden proportion is not always possible due to limitation by factors such as lip anatomy, facial form, and arch form. Furthermore, evidence in the literature shows that deviation from the golden proportion may still produce beautiful smiles. Therefore, it is best to consider the golden ratio as a mean rather than a standard. A more exible option with regard to width proportions between teeth is the concept of recurring esthetic dental (RED) proportion. This involves choosing a proportion specically designed for the individual patient that is harmonious with their arch size, anatomy, and facial features. This proportion should be constant as one moves posteriorly and should be symmetric (Fig 2-24). A mathematical formula has been derived that calculates the width of the maxillary central incisor for any RED proportion given a xed intercanine frontal view width. This width is determined by measuring the frontal view width between the distal aspects of the two maxillary canine teeth. The formula is as follows: (frontal view width of the 6 anterior teeth) / 2 (1 + RED + RED2) = width of central incisor.Fig 2-24 Golden proportion on the right teeth and recurring esthetic dental proportion on the left teeth.Z0.62YGolden proportionY = 62% of XZ = 62% of YRED proportion2/1 = constant x3/2 = constant xY0.62XX123The law of face6The face of a tooth is the area on the facial surface of anterior and posterior teeth that is bounded by the transitional line angles as viewed from the facial aspect. The transitional line angles mark the transition from the facial surface to the mesial, distal, cervical, and incisal surfaces. The tooth surface slopes lingually toward the mesial and distal surfaces and toward the cervical root surface from these line angles. Often no transitional line angle appears on the incisal portion of the facial surface; in this situation, the face is bounded by the incisal edge or the occlusal tip. Shadows are created as the light strikes the line angles, and the face of the tooth is the only area that reects light. Therefore, the size of the face of the tooth determines the perceived size of the facial surface. Improper position or contour of transitional line angles will result in a wax-up or a restoration that appears dissimilar even if it is identical in size to the contralateral tooth because the light is being reected from a smaller or larger surface (Fig 2-25).CharacterizationThe purpose of smile design and esthetic wax-ups is to create a natural-looking, beautiful smile. However, the reality is that natural smiles are not necessarily perfectly symmetric, uniform in color, or perfect by Dental Esthetics (Microesthetics)35scientic standards. In addition, perception of beauty is very subjective and diers between genders, ages, and cultures. Purely focusing on the scientic principles is not the best approach and may result in smiles appearing too uniform and perfect and thus perceived as fake. Achieving the ideal smile requires a combination of the esthetic principles and artistic creativity to match the individual’s personality. Realism is achieved by mimicking the surface texture and heights of contour of adjacent teeth. Slight imperfections and random deviations from the norm contribute to the individuality and subtle beauty of a smile. Characterization of teeth to provide individual natural-looking smiles can be done by shaping and contouring the teeth in a wax-up or during a porcelain try-in. This may involve making point and line angles softer or sharper, incorporating vertical lines that accentuate height or horizontal lines that accentuate width, and creating random minor imperfections. With regards to symmetry, it is advised to create mirror image central incisors. This has an important eect in making the smile beautiful; the lateral incisors may show slight asymmetry in a natural smile. Staining and using dierent shades of porcelain is also an important element in characterization of a smile, such as using polychromatic shades for more natural-looking teeth and making the proximal surfaces darker to create shadows that add depth to the smile.13,16Optical illusionsSome techniques may be used to make teeth appear narrower or wider (Fig 2-26) if the space available was not equal to the ideal-sized teeth for esthetics. In addition to the techniques mentioned below, which can be incorporated in a wax-up, dierent stains and shades used in the porcelain can also provide the illusion of narrower or wider teeth. How to make teeth appear narrower in a wax up16: 1. Move the transitional line angles inward toward the midline to reduce the size of the face of the tooth.2. Increase the cervicoincisal length of the interproximal contact area between the teeth.3. Make the incisal edges less horizontal by curving the mesioincisal and distoincisal corners, thus relocating the point angles further inward and increasing the incisal embrasure sizes.4. Slight notching of the incisal edge to break up the horizontal line.5. Avoid horizontal characterization lines.6. Incorporate vertical characterization lines.7. Create a more pronounced cervical line curve.8. Move the labial ridge of the canine and the cusp tip toward the mesial, making the mesial half narrower, because this is the main part of the canine that can be viewed from the facial view.Fig 2-25 (a) Dierent size of the face of teeth aects ap-parent size. (b) Marking face of teeth in esthetic wax-up.ba Principles of Esthetics362AABBFig 2-26a Moving transitional line angles toward the midline to make teeth appear narrower. Apparent width becomes A, which is less than B even though both teeth have the same dimension. Fig 2-26c Vertical character-ization grooves to make teeth appear narrower. Fig 2-26e Making an esthetic wax-up appear narrower by moving the line angles toward the midline, rounding the point angles, and incorporating vertical characterization lines.Fig 2-26d Incorporating hori-zontal characterization grooves to increase the apparent width of teeth.Fig 2-26b Rounding the point angles decreases the mesiodistal width of the incisal edge to make teeth ap-pear narrower. Apparent width B is larger than A even though both teeth are equal in width. Dental Esthetics (Microesthetics)37How to make teeth appear wider in a wax up16:1. Move the transitional line angles further outward toward the proximal ends to increase the size of the face of the tooth and create a wider facial surface.2. Decrease the cervicoincisal length of the interproximal contact area between the teeth.3. Make the incisal edges more horizontal by relocating the point angles further toward the proximal ends and decreasing the incisal embrasure sizes.4. Incorporate horizontal characterization lines.5. Avoid vertical characterization lines.6. Create a less pronounced cervical line curve.7. Move the labial ridge of the canine and the cusp tip to the distal.Fig 2-26h Making incisors in a wax-up appear wider by moving line angles proximally, cervical height of contour cervically, and reducing embrasure sizes.A ABBFig 2-26f Moving the canine labial ridge distally in Fig B to make the canine appear wider.Fig 2-26g Making the canine in an esthetic wax-up appear narrow- er and longer in Fig B by moving the labial ridge mesially, pointing the cusp tip, and incorporating vertical characterization lines.

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