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What is an Esthetic Wax-Up ? 


An esthetic wax-up is a process in which wax is applied to a model of the patient’s teeth to simulate the procedure and results of planned reconstruction, repair, or enhancement of a smile.  

Esthetic wax-ups are indicated when anterior restorations are planned to restore caries lesions, fractures, wear (attrition/erosion/abrasion), diastema, intrinsic discoloration, or microdontia that most commonly affect the lateral incisors (peg-shaped lateral) or to generally enhance a poor smile. Several factors should be considered before initiating the treatment, such as caries risk, periodontal health, existing restorations, alternative treatment options, and patient expectations.

First of all we have to put into consideration some principles that are very crucial to know before we start implementation of the procedure. 


Dental Esthetics (Microesthetics)


Alignment of teeth

Properly aligned teeth are a major contributor in achieving the ideal smile. Tooth angulation from a lateral view represents the faciolingual alignment of teeth and determines the soft tissue support, lip prominence, and facial profile as well as the appearance of the teeth. 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 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). 

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. 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. Lack of proper vertical alignment of maxillary anterior teeth resulting in a canted midline is more esthetically unpleasant than a midline shift. 


Morphology of anterior teeth

The 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 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 line angles at the borders, two shallow depressions appear mesial and distal to the middle lobe of the tooth. 

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 angle. 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. 

(a) Developmental depression in an extracted central incisor. (b) Esthetic wax-up with developmental depressions. 

(a) Extracted central incisor with no developmental depressions. (b) Esthetic wax-up with no developmental depressions.

Incisal edges are normally thin and nicely rounded in an unworn dentition. 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 flattened, thicker edge. This is commonly associated with an older age appearance. Incisal edges may have different 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 mesiodistally. 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 follow the arch curvature, and the incisal edge is wider and less symmetric than that of the mandibular central incisor. 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. In addition to their effect on esthetics, incisal edges enable the anterior teeth to have a direct and indirect effect on masticatory function. The direct effect is providing a means for the anterior teeth to incise and bite food, and the indirect effect 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). 

Incisal edge position

The 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 first 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 result in more mandibular display. This effect is the opposite to the aging effect on maxillary incisal display, whereby tissue sagging diminishes tooth display gradually until none of the maxillary incisal edges can be seen by age. The correct incisal edge position is therefore crucial because it affects smile esthetics, anterior guidance, and proper pronunciation. 


Incisal edge position is important to phonetics, function and esthetics.


Canine cusps and cusp ridges

Canines 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 offset to the mesial side. 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. These features should be perfected in esthetic wax-ups for a natural 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 and should allow the disocclusion of posterior teeth in lateral movement to achieve canine guidance.

Embrasures

Embrasures 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. This can be easily achieved during waxing by proper reproduction of the interproximal contact location and the incisal edge height and form as well as perfecting the point angles to the correct rounding. If these embrasures are made uniform, this results in an unnatural smile with interproximal contacts that are too long and produces a box-shaped appearance of teeth. 

Interproximal contact area

Interproximal contact area is defined 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 embrasures 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. 

Interproximal contacts may influence dental esthetics by affecting 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 affect 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. 


Size of teeth/Tooth dimensions :

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, 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.
Maxillary 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 affect 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. During an esthetic wax-up, the central incisors should be the first 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 mesiodistally 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. 

Establishing tooth width

We must differentiate 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.
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. The 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 flexible option with regard to width proportions between teeth is the concept of recurring esthetic dental (RED) proportion. This involves choosing a proportion specifically designed for the individual patient that is harmonious with their arch size, anatomy, and facial features. RED proportion states the following : the width proportion between two adjacent teeth as viewed from the frontal should remain constant while progressing successively distally. This proportion should be constant as one moves posteriorly and should be symmetric. Dividing the frontal view width of the maxillary lateral incisor by the frontal view width of the central incisor yields a quotient that should be the same as the quotient obtained by dividing the frontal view width of the maxillary canine by the frontal view width of the lateral incisor. Generally the values of the RED proportions used are between 60% - 80%. 

 A mathematical formula has been derived that calculates the width of the maxillary central incisor for any RED proportion given a fixed 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.

Once the ideal width of the central incisor has been calculated, the width of the central incisor is multiplied by the desired RED proportion to determine the frontal view width of the lateral incisor. The resulting lateral incisor width is multiplied by the same RED proportion to yoeld the desired frontal view width of the canine. 

The golden proportion could be defined as the 62% RED proportion, and is one of many RED proportions that can be applied. Thus, RED proportion has a more universal application. 

The law of face

The 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 reflects 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 reflected from a smaller or larger surface.

Characterization

The 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 scientific standards. In addition, perception of beauty is very subjective and differs between genders, ages, and cultures. Purely focusing on the scientific 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 effect in making the smile beautiful; the lateral incisors may show slight asymmetry in a natural smile.
Staining and using different shades of porcelain is also an important element in characterization of a smile, such as using polychromatic shades for more natural-looking teeth.

Optical illusions

Some techniques may be used to make teeth appear narrower or wider 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, different stains and shades used in the porcelain can also provide the illusion of narrower or wider teeth. 

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.
Rounding the point angles decreases the mesiodistal width of the incisal edges to make teeth appear narrower. Apparent width B is larger than A even though both teeth are equal in width.


How to make teeth appear narrower in a wax-up :

1️⃣ Move the transitional line angles inward toward the midline to reduce the size of the face of the tooth.
2️⃣ Increase the cervicoincisal length of the interproximal contact area between the teeth.
3️⃣ 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.
4️⃣ Slight notching of the incisal edge to break up the horizontal line.
5️⃣ Avoid horizontal characterization lines.
6️⃣ Incorporate vertical characterization lines.
7️⃣ Create a more pronounced cervical line curve.
8️⃣ 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.

How to make teeth appear wider in a wax-up :

1️⃣ 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.
2️⃣ Decrease the cervicoincisal length of the interproximal contact area between the teeth.
3️⃣ Make the incisal edges more horizontal by relocating the point angles further toward the proximal ends and decreasing the incisal embrasure sizes.
4️⃣ Incorporate horizontal characterization lines.
5️⃣ Avoid vertical characterization lines.
6️⃣ Create a less pronounced cervical line curve.
7️⃣ Move the labial ridge of the canine and the cusp tip to the distal.


Vertical characterization groove to make teeth narrower.

Horizontal characterization groove to increase the apparent width of teeth.


Making the incisors appear wider in the wax-up by moving the line angles proximally, cervical height of contour cervically and reducing the embrasure 


Making an esthetic wax-up appear narrower by moving the line angles toward the midline, rounding the point angles and incorporating vertical characterization lines.


Moving the canine labial ridge distally in Fig. B to make the canine appear wider.


Making the canine appear narrower and longer in Fig.B by moving the lavial ridge mesially, pointing the cusp tip and incorporating vertical characterization line.

Stay tuned for " Part 2 " ,, How To Implement ? ..