Cosmetic choreography – the basis of a beautiful smile
The demand for cosmetic dental procedures around the world seems unaffected by economic vagaries and appears to be growing at a compounding rate of around 20% per annum.
This growing demand is forcing general dentists to review both their diagnostic and clinical delivery skills, leading to a demand for training programmes in cosmetic dental procedures. A survey of leading international cosmetic dentists carried out by The American Academy of Cosmetic Dentistry found some interesting insights into the public’s attitude to cosmetic dentistry.
The trends observed in these figures seem consistent with anecdotal evidence from cosmetic dentists throughout the world, and found that:
• Colour improvement (whitening) is a patient requirement for all age groups
• The largest population group (20–25 year-olds) are interested in veneers to improve the alignment of their teeth that they were not able to treat as children with orthodontic procedures (mostly due to lack of finances as adolescents)
• The over-50 group are interested in improving their worn smile and discoloured appearance with bleaching and veneers where loss of tooth structure has led to a worn, aged smile.
Given the increasing demand for cosmetic dental procedures commonly driven by the public’s exposure to the ideal smile in the print and visual media, it is important for the practising cosmetic dentist to know how to build and design a natural smile that is similar to the artist creating his outlines on his white canvas.
The great denturists of the mid-20th century, Dr Lombardi and Dr Pound, mastered and taught the art of creating a natural smile as it pertained to edentulous mouths with full and partial dentures.
The great cosmetic dentists of the 20th century, Dr Pincus and Dr Goldstein, used the same foundational guidelines in their creation of beautiful smiles in dentate mouths, utilising the adhesive porcelain systems that are currently available.
A natural smile (Figure 1) has at its foundation the following set of parameters:
• Dental midline parallel or coincident to the mid-facial plane – ensure that all patients undergoing cosmetic or reconstructive procedures are aware of any deviations from this prior to treatment
• Edges of the upper teeth run parallel to the lower lip line in full smile
• The younger the individual, the less wear and more translucency exists at the incisal edges
• Gingival edges of the upper teeth are just covered by the internal aspect of the upper lip line.
Variations of this occur depending on high, normal or low lip lines. High smile lines with excessive gingival display constitute about 10% of cases, with low smile lines being present in around 20% of cases.
When creating an aesthetically pleasing smile – whether it is via porcelain veneers, all porcelain crowns or implant-supported crowns – there are a sequence of steps that should be followed in order to build and create a pleasing, harmonious and natural smile.
The centre line is made parallel to or co-incident with the mid-facial plane (Figure 2). Dental floss is held vertically on the face from the chin point to the midpoint of the hairline and the patient viewed in a sitting position from the front. As the midlines are viewed from the front of the patient, any discrepancy is shown in the mirror.
Discrepancies of less than 2mm can be managed restoratively. Discrepancies greater than 2mm need to be orthodontically managed, if the patient requests coincident midlines at the end of treatment. Proportioning of the teeth as viewed from the front of the patient, utilising the Golden Proportion, will create balance in the smile (Figure 3). Understanding that the reducing proportions of around 62% only relate to the smile as viewed from the front, not side views.
The ratio of the teeth width is commonly 10:6.2 – that is the laterals are around 62% of the width of the centrals, and the canines are 62% of the width of the laterals when viewed from the front.
Common problems in veneering the front six teeth relate to under-preparation of the canines with resultant visual block-out of the premolars. Commonly, teeth to be veneered have prominent canines. The initial prep should bring the canines back into the arch as viewed from the incisal; the secondary prep of the canines to allow room for porcelain (7 to 1 mm) will ensure that the premolars are balanced in the final smile.
The reference between length and width is 5:4, length around 1.2 times the width of the same tooth. Variations of this can be managed by widening or narrowing the marginal ridges so as to vary the amount of light reflection that the viewing eye receives from the observed tooth.
The creation of the incisal silhouette is the final and yet most important step as it imparts life and soul to the smile (Figure 4). Understanding the difference between lengths of the teeth comparing centrals to laterals and the signature curvature of the distal incisal edges controls the secret to lifelike restorations.
Centrals are usually 1-2mm longer than laterals but around the same length as the canines. The gingival levels of the centrals are higher than those of the laterals by around 1mm, yet approximate the same horizontal line of the canines at the free gingival margin.
There must be a lifelike recreation of the incisal silhouette where the marginal ridges flow into the incisal corners. Commonly, lack of preparation in the marginal ridge area creates a square, false look to the veneers. This is because the ceramist does not have enough depth of preparation to shape the porcelain back to its ideal position and create correct depth of colour and light reflection to match the adjacent natural teeth.
The true creation of cosmetic choreography occurs with the understanding of the important role that the individual front teeth play in the smile (Figure 5):
• Centrals are longer and have more translucent edges in younger people, commonly called ‘the age teeth’. With ageing and bruxing wear, the incisal edges flatten and translucency is lost, creating the appearance that we associate with ageing
• Laterals dictate the masculine or feminine traits of a smile. Women more commonly have more rounded, sweeping distal incisal corners whereas men tend to have squarer corners
• Canines are referred to as ‘the personality teeth’. An abiding image remains of the first screen Dracula, Bela Lugosi, and his dominant aggressive canines. Softer, rounder curves on the canines tend to be found in gentler personality styles.
The final component of a natural, bright smile is the transmission of reflected light from the surface of the tooth to the receiving eye (Figure 6).
Natural untouched teeth have a layer of generally high-value enamel covering the inner core of higher hue dentine. The process of bleaching raises the value of enamel sometimes creating a slight grey translucency; it is important to ensure that patients have completed their bleaching prior to final colour selection for their veneers.
The veneering or crowning process replaces some, if not all, of the enamel layer. It is important to carry out this replacement with the most lifelike recreation of the depth of colour to create, in the observing eye, the appearance of a natural smile with the depth of colour that one would expect in natural teeth.
This is the reason that porcelain veneers are more lifelike than PFM crowns, which is the recreation of the depth of colour that a natural tooth possesses. We are too quick to discharge the young, non-decayed mouth to the realms of six-to-twelve month recall, rather than spending time observing what makes a young smile appear to be so lifelike.
Photographic recording of these opportunities should be carried out with patients’ or parents’ permission to create an opportunity to review the visual display of natural teeth on a regular basis. This is to imprint on the generally non-stimulated ‘right brain’ the parameters of a beautiful smile that is ‘mother nature’s’ signature.
Adolfi D (2002). Natural Esthetics. Quintessence Publishing Co Ltd
Magne P, Belser U (2002). Bonded Porcelain Restorations in the Anterior Dentition: A Biomimetic Approach. Quintessence Publishing Co Ltd
Patient survey in: American Academy of Cosmetic Dentistry Journal (1999).
Private communication between Ron Goldstein & Derry Rogers 1996-2002