The Fountain of Youth: colour and incisal anatomy

A youthful appearance has certain distinct characteristics. In a split second the human eye can undoubtedly determine pretty accurately somebody’s age. The smile is a very important part of those characteristics. If a smile is restored with age appropriate traits it will not distract the human eye in thinking something is wrong. It will harmonize the smile. And an harmonious smile is a beautiful smile. We can even play with it in chipping away some years.

Very worn teeth with cracks, uneven wear, and different patterns of discoloration are considered in most cases as complicated to restore. Unworn flawless teeth on the other hand might be even more challenging and complex as well. It is copying nature and nature only. And for Mother Nature respect is due.

So the question raises: what are the characteristics of youthful teeth? Why do we instantly know rather precisely the age of teeth?First of all length. The youthful anterior teeth have not yet been exposed for long to wear in any form. And their length is at the maximum. Therefore the incisal edge is still undamaged. In adult open bite cases those incisal edges can also be observed. The shape of the incisal edge is still in its pristine garland form with rounded angles and open embrasures. The teeth of young people have enamel with high value and dentin with low chromaticity and high fluorescence. The thick enamel layer in young tooth looks ‘milky’ in a lot of cases. No dentin is exposed at the cervical part of the tooth. Because no attrition, erosion, abrasion or a combination of the above has effected and shortened the tooth the incisal edge consists completely out of enamel before the transition into the dentin mamelons. The phenomenon of opalescence occurs. Giving the tooth a beautiful halo. Different colors can be observed by the eye because of different ways the enamel structure transfers, reflects or absorbs the light. The color of a young tooth is at its whitest because of lack of discolorations, absence of secondary and tertiary dentine and the porosity of the enamel. The surface of a young tooth displays a lot of structure (lobes, perikymata) in the rich enamel layer.

The following case shows step by step the restorative considerations in making a tooth appear youthful.

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Fig.1
Initial situation. A 17 year old patient suffered a trauma on her teeth several years ago. The teeth have recently started to discolor and she was seen by endodontologist Marga Ree.(photo courtesy M.Ree)

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Fig.2
Initial X-ray shows apical radiolucencies on both central incisors (photo courtesy M. Ree).

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Fig.3
Root canal treatments were carried out. After internal bleaching fiber posts were placed.(photo courtesy M. Ree).

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Fig.4
The endodontic treatment and internal bleaching had significantly improved the color of the teeth involved.

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Fig.5
Patient came with the request to have her teeth restored in a way that all signs of the trauma would disappear. Obviously the color of the old composite restoration had to be revised, but also the shape of the two centrals was incongruent with the rest of the anterior anatomy displayed.

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Fig.6
The patient had received orthodontic treatment in the past. A difference in root and crown angulation of the teeth 11 and 21 can be noted.

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Fig.7
In consent with the patient it was decided not to sacrifice any enamel or dentin to correct the difference in angulation. Nonetheless a treatment goal of symmetry of the two central incisors was defined.

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Fig.8
The existing original anterior anatomy can be described as youthful.

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Fig.9
Impressions and preoperative photographs were made to create the wax-up on the study models.

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Fig.10
A silicone index was made to have reference of the desired dimensions during treatment.

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Fig.11
Rubber dam isolation. Note that the color scheme is very diffused.

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Fig.12
The color mock-up is ideally made intraorally before the rubber dam is in place while the teeth are still fully hydrated. In this case therefore it was the first step to be taken after placement of the rubber dam. The composite is light cured before analysis. Dehydration of teeth changes the colors significantly within minutes.

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Fig.13
Removing the old composite lays bare cracks in the enamel that later on need to be made invisible in the restoration.

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Fig.14
With the LM Fissura instrument the transition of restoration to tooth is marked. In order to prevent excess on the palatal at the end which requires a lot of time to remove.

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Fig.15
The palatal wall is built with an enamel composite. This first layer already extends in its shape towards the labial and therefore the color chosen for this layer is of importance in creating the desirable halo in the incisal third. Which is characteristically completely intact in youthful teeth. If you want to artificially enhance the white halo effect even more a very thin layer of a white dentin composite can accentuate the halo.

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Fig.16
The matrix gives a round contour to the proximal wall. This contour shapes the tooth in a youthful way because it immediately gives the restoration a nice, open embrasure.

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Fig.17
The dentin is applied in a three mamelon shape, each mamelon for every developmental lobe. In older teeth mamelon formation might look more diffused. In youthful teeth mamelons are usually quite distinct in shape. Now a highly translucent enamel composite can be placed in between the mamelons to try to recreate the opalescence and translucency of natural enamel. The hydroxyapatite structure of natural enamel gives a certain light reflection and passing through of light. That brings light back to the eye that appears blueish. The highly translucent enamel composite in between the mamelons and the halo appears blueish to the eye as well. It mimics the opalescence effect of natural enamel. Natural enamel has the highest opalescence even compared to the most recent composites.
The dentin in youthful teeth is low in chromaticity. Choosing a whiter dentin in youthful teeth compared to old teeth is therefore a good choice. In this case the teeth were endodontically treated and had lost a lot of dentin because of the endodontic access that had to be made. That has an impact on the appearance of the tooth. Restoring the tooth with a fluorescent dentin will restore some of the lost brightness.

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Fig.18
Tooth #21 completed with final layer of white enamel composite.

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Fig.19
Application of ‘The Youth Elixir’ before the final layer

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Fig.20
First check with the help of the silicone index after application of the last layer. First to be adjusted is the incisal thickness.

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Fig.21
The transitional lines are identified by a pencil and corrected so that they are straight and symmetrical

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Fig.22
From the lateral view the three facial planes can be checked. A smooth curve should be seen. In this case, a little reduction on the mid facial is necessary.

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Fig.23
Primary shape established. Note that the dehydration of the natural enamel makes the composite to appear yellow. The teeth are now ready for further rejuvenation

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Fig.24
Unworn lower incisors and cuspids are waving with youth; let them be the inspiration! The central lower incisors are already somewhat worn.

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Fig.25
The surface structure is created with a diamond bur in slow motion and without water.

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Fig.26
To create the beautiful garland form of the incisal edge the bur was slightly tilted.

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Fig.27
Just resting the bur while it is not operating on the lateral can give you the perfect indication for the angle the bur has to be used on the central.

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Fig.28
With a rubber polishing cup the bur impressions can be smoothened out to look more natural.

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Fig.29
Final polishing steps are carried out.

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Fig.30
Just before removing the rubber dam. At the incisal edge a tooth only consists of enamel. This gives a beautiful opalescent effect in that incisal area. Copying that with composite is difficult, but the use of very translucent composite helps. The highly translucent composite in between the mamelons creates contrast and a blue appearance. And the enamel at the edge a halo. With a certain light reflection (red waves) amber can be seen, without, an amber colored composite has been added.

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Fig.31
Final result. The garland form of the incisal edge says young.

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Fig.32
The colors of the final restorations are in harmony with the other characteristic anterior teeth. Also important in the final outcome is the health of the gingiva. The patient had continuous oral hygiene instructions during the whole course.

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Fig.33
There are no more transitions visible and the difference in root and crown angulation from the beginning is corrected. Symmetry of the two centrals is achieved.

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Fig.34
Final beautiful youthful smile: despite endodontically treated the teeth look vivid.

Conclusions

Creating youthful teeth is a combination of factors. It starts by the inspiration the patient offers you. Their own teeth or a picture of how they used to be. Then the quest for youth can begin. With the knowledge of anatomy and material characteristics a tooth damaged by wear or trauma can be almost reconstructed to what it used to look like. Almost is a word added out of humbleness towards the tremendous beauty of nature. But fortunately trying to copy it is always an option!

Bibliography

1. Lee YK.Opalescence of human teeth and dental esthetic restorative materials.
Dent Mater J. 2016 Dec 1;35(6):845-854. Epub 2016 Aug 20.
2. Manauta J, Salat A. Layers, An atlas of composite resin stratification. Chapter 2 In and chapter 4 Mid Quintessence Books, 2012
3. Fahl N Jr. A polychromatic composite layering approach for solv- ing a complex Class IV/direct veneer-diastema combination: part I. Pract Proced Aesthet Dent. 2006;18(10):641-5.
4. Pecho OE, Ghinea R, do Amaral EA, Cardona JC, Della Bona A, Pérez MM. Relevant optical properties for direct restorative materials.Dent Mater. 2016 May;32(5):e105-12.

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