Changing Smiles - Changing Concepts

INTRODUCTION

Esthetic and cosmetic dentistry has become the major focus in the field. Dale Carnegie (1888-1955) a famous American scholar described smile as the most important methods of influencing people. Television and movies have exposed viewers to beautiful faces and brilliant smiles; however teeth are not in perfect balance with their surrounding structures. So how do we define Aesthetics!! aesthetics can be defined as “well developed sense or perception of natural beauty .

The goal is to achieve a pleasing balance between idealism and diversity. Idealism and proportion are tools not goals; they are merely a guide within which the artist imagination has free play 1.Brisman ( 1980 ) demonstrated two kinds of symmetry, a horizontal symmetry in which the design shows similar elements from left to right in a regular sequence ( piano, picket fence ) and a radiating symmetry in which one segment is a mirror image of the other, but these seemed to be monotonous.

When beginning with aesthetics, we must begin with an appraisal of the position of the maxillarycentral incisors relative to the upper lip. This assessment is made with the patient’s upper lip at rest. Using a millimetre ruler or a periodontal probe, we determine the position of the incisal edge of the maxillary central incisor relative to the upper lip. The position of the maxillary central incisor can be either acceptable or unacceptable. An acceptable amount of incisal edge display at rest depends on the patient’s age.3 Previous studies have shown that with advancing age, the amount of incisal display decreases proportionally.

If the incisal edge display is inadequate,then a primary objective of interdisciplinary treatment may be to lengthen the maxillary incisal edges. This objective could be accomplishedwith restorative dentistry4,orthodontic extrusion5 or orthognathic surgery6.Choosingthe correct procedure will depend on the patient’s facial proportions, existing crown length andopposing occlusion. If the incisal edge display is excessive, then an objective of treatmentcould be to move the maxillary incisors apically by either equilibration,restoration7, orthodonticsor orthognathic surgery. The decision between these disciplines again will depend onthe patient’s existing anterior occlusion, facial proportion or both.

The second aspect of aesthetic tooth positioning to be evaluated is the maxillary dental midline. If the midline is deviated to the right or left, studies have shown that midline deviations of up to3 or 4 mm are not noticed by laypeople if the long axes of the teeth are parallel with the long axis of the face9. So perhaps the most important relationship to evaluate is the mediolateral inclination of the maxillary central incisors. Researchers have found that if the incisors are inclined by 2 mm to the right or left, laypeople regard this discrepancy as unesthetic.9A canted midline can be corrected with orthodontics or restorative dentistry. Usually the decision will depend on whether the maxillary incisors will require restoration.2

Facial references to dental aesthetics:

Horizontal reference: the interpupillary line helps to evaluate the parallelism of incisal plane, gingival margins and to identify a maxillary cant if present. As described by Vig and Brundothe upper lip helps to evaluate average maxillary incisor display of 1.91mm for men, 3.40 for women, 3.65mm for short lips, 0.59mm for long lips, 3.37mm ( up to 29years ) for young people and 1.26mm for old people ( 30-50 years ). The lower lip line evaluated the buccolingual position of the incisal edges of maxillary incisors and the smile curve.3

Vertical reference: the line passing through Glabella, nose and chin is the most commonly employed vertical reference but the centre of the upper lip is more preferable due to facial asymmetry.

CASE REPORT 1

A 25 year old girl came reported to the department with a complaint of unaesthetic smile, artificial and uneven looking upper front teeth. She was a beautician by profession; she gave a history of prosthetic treatment done in the aesthetic zone in order to correct her smile. On examination it was found that there was six unit porcelain fused to metal Fixed Dental Prosthesis on her maxillary anterior teeth. A quick aesthetic analysis revealed,

1. A short upper lip
2. Canted gingival zenith line
3. Midline shift
4. Dark cervical margins / the Umbrella effect8
5. Increased opacity and value ( figure 1 )

Figure.1

Based on her aesthetic analysis the following treatment plan was formulated and executed,

1. Functional analysis of diagnostic models: since full coverage restorations of all ceramic materials were planned a functional analysis of the models mounted with the help of facebow could help eliminate any occlusaldiscrepencies that may effect the longitivity of the restorations. A facially generated treatment plan could help in establishing the incisal edge position of the maxillary teeth.
2. Diagnostic mock up: a diagnostic mock up is a blue print that is made based on the principles of aesthetics and having the final restoration in mind. Having the facially generated treatment plan in mind the excessive maxillary display due to the short lip could be successfully treated by apically positioning the maxillary anterior teeth either by orthodontic intrusion or by a surgical crown lengthening. This is first achieved by a mock up and a surgical stent is prepared with a provisionalisation material to guide the extent of crown lengthening procedure.( figure 2 )
3. Periodontal crown lengthening: a surgical crown lengthening procedure was performed; gingivectemy was done to the desired crown level. Then a flap was elevated and the bone trimmed 3mm above the desired gingival margins.
4. Provisionalisation is done to immediately exhibit the overview of the final result and to achieve guided healing of the cervical gingiva.( figure 3 )
5. Confirming the incisal edge position in the provisional for esthetics and function.
6. E - max ( lithium disilicate ) full coverage crowns were fabricated, the incisal edge position transferred through a silicone index of the approved provisional.( figure 4 )

Figure.2

Figure.3

Figure.4

CASE REPORT 2

A 35 year old lady reported to the department with a complaint of proclined and spaced teeth, she had been give the options of orthodontics and surgical intervention but due to time constraints she wanted restorative management of her smile. An aesthetic analysis of her smile zone reveals midline diastema, midline shift, midline cant and a mesiolabially rotated right lateral incisor.( figure 5 )

Figure.5

Based on her aesthetic analysis the following treatment plan was formulated and executed,

1. Functional analysis of mounted diagnostic models: diagnostic models were mounted on a semi adjustable articulator with a face bow transfer and a centric record, a functional analysis was done to eliminate any deflective interference to the path of closure.
2. A Diagnostic mock up is done on the articulated models, the maxillary cant was first corrected, the midline diastema was closed, the midline could not be restored to the ideal but a deviation of 2 - 3mm which was clinically acceptable and un noticeable was confirmed.( figure 6 )
3. For the management of proclined and rotated incisors, endodontic management both the central incisors and the right lateral incisor was required.
4. Provisional were fabricated based on the diagnostic wax up after tooth preparation. These provisional were left in place to evaluate them for the final incisal edge position for aesthetics and function.( figure 7 )
5. Since the midline diastema closure was carried out, the process eventually increased the width of the anterior restorations. An illusionary perception had to be created by working on the line angles and the buccal surfaces. The line angles were brought closer reducing the surface area of the reflecting buccal surface hence less light was reflected giving a illusion of a narrow surface.
6. This incisal edge position was copied either with a silicone guide or a custom incisal guide table to the final restoration. The final restoration was planned with full veneer individual E - max restorations for the incisors and partial veneer restoration on the canines to restore the smile line.( figure 8 )

Figure.6

Figure.7

DISCUSSION

The case report 1 had a short upper lip hence the incisor exposure was more. More concentration needs to be given at the cervical margins of such patients. The so called Umbrella effect is actually an optical phenomenon that is produced by the upper lip, because this feature will significantly influence the interaction of light with the teeth and the supporting tissues. When the lips are retracted (in case of oral photography) the apical extension of framework generally will not have a strong impact on the optical behavior of the crown because the light can be directly distributed into the tissues.When the upper lip is in normal position however the difference becomes significant because direct penetration of light into the surrounding periodontal tissues is prevented.

Reduced metal frameworks and extended porcelain margins are imperative to permit trans illumination of gingiva. All ceramic restorations that are bonded to the prepared teeth with an aesthetic resin cement impart the natural looking aesthetics to the cervical area as well. In case report 2, it was confirmative during the diagnostic mock up that the deviated midline could not be accurately restored. Since the cant of the central incisors exaggerated the midline shift, it was planned to primarily correct the cant which reduced the exaggeration of the midline shift.

The study on perception of orthodontist, general dentist and lay people to altered aesthetics aids the Dental professional in making specific treatment recommendations. According to this studyThe threshold level at which orthodontists rated midline deviations as significantly less esthetic was 4mm, which means that the maxillary dental midline had to be shifted as much as 4mm on one side before it became consistently noticeable.

However the incisor crown angulation was identified to a deviation of just 2mm as less esthetic by dentist and lay man9. Another study evaluating the perception to midline diastema showed unaesthetic smile with increase in the diastema at a threshold levels of 1.5mm10. Based on these results the midline cant for the patient was corrected mandatorily but the deviated midline was only refined within the permitted limits, however in the process of closing the midline diastema the width of the incisors had to be manipulated by working on the illusionary perception. When it is not clinically possible to reestablish correct tooth proportion, the clinician can try to create the illusion of having modified the tooth size.12 without actually doing so.

This can be done by working on the line angles and buccal surfaces of the anterior teeth.The light that directly strikes the buccal surface between the line angles is reflected, while the mesial and distal areas outside these lines deflect it and are therefore less noticeable. However its true that perfectly vertical dental midline reinforces the perception of order and organization but also imparts some artificiality.

Miller et al found that the dental midline coincided with the median line of the face in 70.4% of the population, this is consistent with the “dentogenic concept”, which states that an eccentric midline, if not too exaggerated, is acceptable and lends to the illusion of the natural dentition11.

CONCLUSION

Restoring Esthetics always begins with the thought process of symmetry, proportion and idealism (the golden proportion)in mind but characterizing smile has also been an important consideration since the very onset of dynesthetic theory for complete dentures which requires equal attention.Various methods have evolved to recreate the perfect teeth/smile (smile designing software ) but never at the cost of being un natural. The goal in a natural smile is to achieve a pleasing balance between idealism and diversity, because in a subtle way natural dentitions are always asymmetrical.

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