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Content:
1. Dental Morphology
A. Central Incisors
B. Lateral Incisors
C. Canines
D. Premolars
2. The Incisal Edge
3. Gingival Esthetics
4. Width/Length Ratio
5. Recurring aesthetic Dental
(RED) proportions
6. Shade and characteristics
A.
Central incisors:
This
is the most important and dominant tooth because of its location and size. The
two incisors are ideally symmetrical. Together, they form the dental midline
that should be completely vertical and ideally corresponds with the facial
midline [1].
Buccal
Aspect. The buccal surface is convex in both mesiodistal and incisogingival
directions, the convexity is greater at the cervical third than at incisal
third. The three mamolons and lobes form the macro texture of the tooth,
consiting of alternating convexities and concavities in the mesiodistal
direction [2].
Transition
lines are located at the transition between light reflective and deflective
zones on the buccal surface, they are esthetically important, manipulating
their location changes the perceived tooth width [1, 3].
Mesial
and Distal Outline. Both outlines are convex, but the distal is more so.
The contact points move gingivally towards the distal, making the incisal
embrasures wider towards the distal as well [2].
The
incisal outline. The incisal edge is almost flat. The incisal plane should
be parallel to the inter-papillary line. And the distal incisal angle is more
rounded than the mesial [1].
B.
Lateral Incisors:
The
lateral incisors resemble a smaller and rounder version of the central
incisors. They have rounder mesial, distal outlines. The incisal edge is also
rounder and 0.5 - 1 mm shorter. The tooth has a lower width/height ratio in
comparison (Fuller et al, 2001). It is less important that the laterals are
symmetrical. In fact, it is asymmetrical in 70% of the patients [1].
C.
Canines:
The crown of the upper canine is seen
mainly from its mesial side. Canines are bulky and greatly convex in the
mesiodistal direction and they have a smaller Width/Length ratio [2].
The mesial outline (between the
contact point and gingiva) is convex and longer than its concave distal
outline. Canines have an incisal cusp with two incisal slopes: the shorter
mesial slope and the longer distal slope, this usually changes after natural
attrition [2].
D.
Premolars:
Premolars
are similar to the outline of canines from the buccal perspective, they are
shorter and appear smaller because of their posterior location. Depending on
the smile width, the second premolar and first molars may also appear in the
smile [2,3].
Note:
due to the word limit, this section discussed the upper anterior teeth only.
Lower anterior teeth morphology are out of the scope of this article.
2.
The Incisal edge:
Esthetic
treatment planning should start from determining the location of the incisal
edge of the central incisor. And from there, the optimum length of the tooth
can be calculated, which ranges between 10.4 to 11.2 mm. This assists in
determining the incisal edge location and width/height ratio of the remaining
teeth [3].
The
location of the incisal edge is influenced by age. Less upper and more lower
incisal visibility is seen as we advance in age, this is caused by the effect
of aging on lips and normal dental wear. At the age of 20, around 3.5 mm of the
upper incisors is shown when at rest position. Furthermore, the amount of teeth
visibility during speech and smiling is additionally dictated by patient’s
desired self image. In addition, the smile line should correspond to the curve
of the lower lip when smiling [3,1].
Furthermore,
the letter F places the incisal edge buccolingually between the mucosal and
cutaneous parts of the lower lip. Additionally, the letter S brings the
mandible forward to correctly pronounce the letter S [1].
3.
Gingival Esthetics:
Healthy
gingiva has a stippled appearance, it is a pale pink and does not bleed on
probing. On the other hand, inflamed gingiva has a shiny red appearance that
bleeds on probing. Before any esthetic treatment is started, the gingival
health has to be established to prevent common complications [4].
The
gingival margins on the centrals and canines are on the same horizontal level,
the lateral is slightly below that by 0.5 - 1 mm. Symmetry between the right
and left sides is important especially on the easily compared central incisors
[3,4].
The
zenith points are the most apical point on the gingival margins, their location
is influenced by the root curvature. They influence the perceived long axis of the
tooth. As a general rule, they are located slightly distally, with the
exception of the centrally positioned zenith point on the lateral incisor
[3,1].
The
gingival papilla fills the spaces between the teeth. Its partial resorption
causes an unpleasant appearance known as the black triangles. The distance
between the contact point and crestal bone dictates the presence or absence of
the papilla. When this space is 5 mm or less, the papilla was present in 100%
of the patients. When it was 6 mm, the papilla was present in 56% of the
patients. And when the distance was 7mm, it was present in only 27% of the
patients [5].
The
need for management of gingival esthetics depends on the level of the upper
lips, low lip level conceals the gingiva making its management less important.
Gingivectomy or gingivoplasy can be used to correct excessive gingival display
or to modify the location of the zenith points, accounting for the biologic
width in the process. Additionally, periodontal surgeries like apically positioned
flap can restore gingival recession when indicated [3,4].
4.
Width/length ratio
This
is one of the most important elements to consider. Changing the width or length
of a tooth without considering the width/length ratio can cause excessively
wide or long teeth. An example of this would be closing anterior spaces of
normally proportioned anterior teeth, leading to wide square-shaped teeth [3].
Pascal
studied 146 extracted anterior teeth to analyze their average width, length and
width/length ratio, he included worn teeth as well. The study’s results are
displayed in table 1 [6].
|
Centrals
|
Laterals
|
Canines
|
Premolars
|
|
Unworn
|
Worn
|
Unworn
|
Worn
|
Unworn
|
Worn
|
Unworn
|
Worn
|
Width
|
9.10 - 9.24
|
7.07 - 7.38
|
7.90 - 8.06
|
7.84
|
Length*
|
11.69
|
10.67
|
9.55
|
9.34
|
10.83
|
9.90
|
9.33
|
W/L ratio
|
78%
|
73%
|
73%
|
|
Table 1: Mean measurements of anterior teeth by
mm.
*: Length was measured from the cementoenamel
junction. This can result in longer teeth than what is clinically observed,
as CEJ is often covered by gingiva.
|
|
5.
Recurring Esthetic Dental (RED) Proportions:
I
will write briefly about this to avoid re-using materials from the previous
assessment.
At
the beginning, Levin [8] theorized that the golden proportions (0.628) is found
in nature. And that esthetically pleasing smiles have this ratio between the
teeth. Meaning that each tooth is %628 of its preceding tooth.
However,
subsequent studies have shown that the golden proportions is not a requirement
of pleasant smiles. On the contrary, it was found that utilizing this
proportion for unsuitable cases can cause an overly dominant central incisors
and excessively narrow canines [7].
Instead,
it was suggested that pleasant smiles have a Recurring Esthetic Dental (RED)
proportion that is constant for each successive tooth. [14]. The RED
proportions influences the buccal corridor as well. The buccal corridor is the
amount of empty space between the posterior teeth (premolars and molars) and
the inner cheek when smiling. In addition to soft tissue influence, higher RED proportions
cause more visible posterior teeth which is associated with a wider buccal
corridor [1].
6.
Shade and characteristics:
Shade
matching is one of the most important and challenging aspects of the esthetic
treatment, failure in shade or characteristics hampers otherwise well executed
treatments.
Dental
clinics should be equipped with color corrected lights (Daylight - 6500K) and a
neutrally colored environment for accurate shade matching. It is useful to
confirm the selected shade with different lighting conditions. Electronic
devices used for shade reading are yet to gain more popularity and reliability
[10].
Shade
matching is done on a wet tooth at the beginning of the appointment to avoid
eye strain and subsequent increased value after tooth dehydration [9].
Shade
communication with the lab should be detailed. A high quality close up image
with optimum lighting of the tooth and shade tab provides the technician with
valuable information. Furthermore, it is possible to accentuate the tooth’s special
characterizations by digitally decreasing the value (Brightness) and increasing
the contrast of the close up image [11].
Traditional
methods for shade matching rely mainly on chroma and value. This has proven to
be insufficient. Vanini’s work offers more predicable and detailed approach for
shade matching [10].
Vanini’s
introduced the 5 dimensional color concept:
• Chromaticity: This is the hue and chroma. 80% of teeth hue are
close to the shade A (Vita classic shade guide) which has a red-orange hue.
• Value: Also known as brightness or luminosity. It is noteworthy
that young enamel teeth incorporate perikimatas that increase surface light
reflection, and subsequently increases value in comparison with older smooth
enamel.
• Intensities: they are the milky white opaque spots, Categorized
as Stains, Small clouds, Snowflakes or Horizontal.
• Opalescence: it is caused by the translucent enamel at the edges
of the tooth. It is categorized as: mamelon-like, split-mamelons, comb-like,
window-like and stain-like.
• Characterizations: they are described as: mamelons, bands,
margins, stains or cracks. [10]
An illustration demonstrates the esthetic principles combined:
1: Dental midline ideally corresponds to the facial midline and mandibular
dental midline.
2: Gingival line: notice the location of the zenith
points. The lateral incisor zenith point is located centrally and 0.5 - 1 mm
below the line.
3: Incisal plane: notice the location of
the incisal edges. The lateral incisor is 0.5 - 1 mm shorter. Notice the corresponding
curvature of this line with the lower lip during smiling.
4: Contact points: notice how their
gingival location towards distal. Also notice the incisal embrasures increase
in size towards distal.
5: Shade and characteristics: In
addition to shade value and hue and chroma, teeth have variety of special
features that contribute to its appearance, such as the location of the
transitions lines, surface macro and micro texture, opalescence or intensities.
6: Width/length ratio: it is around
78% for central incisors and 73% for laterals and canines. Also notice the RED
proportions
7: Buccal corridor contributes to the
fullness of the smile.
References:
1.
MacKenzie, L. Tooth
Morphology. [Lecture]. Smile-On Education Support Platform. 2015.
2. James L Fuller, Gerald E. Denehy, Thomas M.
Schulein. Concise dental anatomy and morphology 4th
edition. Year Book Medical Pub. 2001.
3. Gürel, G. The Science and Art of Porcelain
Laminate Veneers. Quintessence publishing. 2003.
4. Kakar, A. Interdisciplinary Treatment-
Periodontics [Lecture], Smile-on Education Support Platform. 2016.
5.
Yu-Jen Wu, Yu-Kang, Shay-Min. The Influence of the
Distance from the Contact Point to the Crest of Bone on the Presence of the
Interproximal Dental Papilla. 2003.
6.
Pascal Magne, PD, Dr Med Dent, German O.
Gallucci, DMD and Urs C. Belser,.Anatomic crown width/length ratios of
unworn and worn maxillary teeth in white subjects، 2003.
7. PRESTON, J. The Golden Proportion Revisited.
Esthet Restor Dent, 5(6), pp. 247-251. 1993.
8. Levin,E. Dental Esthetics And
The Golden Proportion. The journal of prosthetic
dentistry 40 (3), St Louis, Mosby: Academy
of Denture Prosthetics and other prosthetic dentistry societies. 1978.
pp.244-252
9. Hilton, T., Ferracane, J. and Broome, J. Summitt's
fundamentals of operative dentistry. 2014. Ch 6, 16.
10. Vanini, L. Determination and communication of
color using the five color dimensions of teeth. Practical Procedures and
Aesthetic Dentistry. 2001
11. Brambilla, G. Advanced Anterior Composite Techniques.
[Webinar] Smile-on Education Support Platform. 2015.
