Criteria for Success in Creating Beautiful Smiles, a cosmetic dentistry article by Toronto dentist, Dr. Nathan Blitz.

This article outlines some of the principles utilized in the design and creation of beautiful smiles.

Esthetic restorative efforts in the formation of beautiful smiles are defined and guided by certain universal principles. Although these fundamental guidelines can be readily assessed at the completion of treatment, they must be evaluated during the Planning and operative, stages in order to be properly incorporated in our final restorations. These criteria lend themselves to five distinct classifications. The first deals with General Evaluation and considers (1.) smile line, (2.) buccal corridor, (3.) midline and (4.) principles of golden proportion. The second group deals with Specific Evaluation and involves (1.) proportion of the centrals, (2.) incisal edge position, (3.) emergence profile and (4.) labial contour. The third criteria evaluates Treatment of Embrasures at the (1.) incisal and (2.) gingival. The fourth group presents Periodontal Related Issues under the headings (1.) periodontal health, (2.) margin placement and design, (3.) gingival contour and shape, (4.) symmetrical cervical-incisal tooth length. The final classification assesses Materials and Finish under the headings of (1.) choice of materials, (2.) labial anatomy, (3.) surface finish, and (4.) shade selection. A. General Evaluation 1. Smile line The smile line refers to an imaginary line along the incisal edges of the maxillary anterior teeth which should mimic the curvature of the superior border of the lower lip while smiling (Fig. 1,2).¹ It should not be confused with the lip line which refers to the position of the upper lip during smile formation and thereby determines the display of tooth or gingiva.²

Figure 1
Figure 2

Fig. 1 The smile line refers to an imaginary line along the incisal edges of the maxillary anterior teeth which should mimic the curvature of the superior border of the lower lip while smiling.

Fig. 2 The smile line has been restored through tooth lengthening with eight IPS Empress (Ivoclar-Williams, Amherst NY) veneers. Minor discrepancies between facial and dental midlines are acceptable and in most instances not noticeable.

The lower face has a series of horizontal delineations that display a steady progression in their degree of curvature during smile formation. This is noted in the evaluation of the following structures of the overwhelming majority of pleasing smiles: a. The superior border of the upper lip b. The inferior border of the upper lip c. The incisal edge of the maxillary anterior teeth d. The superior border of the lower lip (c and d should mimic each other) e. The inferior border of the lower lip f. The inferior border of the lower jaw Proper placement of the incisal edges of our anterior restorations reinforces and maintains these harmonious patterns that we see in ideal, natural smile lines. The rejuvenation of the anterior dentition demands harmonious accommodation of the requirements of esthetics and function. These considerations are inseparable and are in fact determinants of each other. Esthetics, phonetics and the smile line help determine the incisal edge position. However, we should be cognizant that facial asymmetry can sometimes prevent the incisal edges from following the smile line. 2. Buccal corridor Buccal corridor refers to the dark space (negative space) visible during smile formation between the corners of the mouth and the buccal surfaces of the maxillary teeth. In many cases a more descriptive term would be the "Tunnel Syndrome." It's appearance is influenced by the width of the smile and the maxillary arch, the tone of the facial muscles and the positioning of the labial surfaces of the upper bicuspids. The unattractive, negative space should be kept to a minimum. This problem can be solved or minimized by restoring the bicuspids. It should not be eliminated completely because a hint of negative space imparts to the smile a suggestion of depth.1 The negative space or Tunnel Syndrome is accentuated when the six maxillary anteriors are rejuvenated. The improvements in hue and value of these newly restored teeth exaggerates the sense of depth, darkness and prominence of the buccal corridor. Because of this concern, it is advisable in some cosmetic cases to avoid restoring the six maxillary anteriors by limiting treatment to the four incisors or else including the bicuspids in the restorative process. 3. Midline The facial and dental midlines must be evaluated. The midline should be perpendicular to the incisal and occlusal plane and parallel to the midline of the face.2 Minor discrepancies between facial and dental midlines are acceptable (Fig. 1,2) and in most instances not noticeable.3 Various anatomical land- marks (midline of the nose, forehead, chin, philtrum, interpupilary distance) can be used as guides to midline assessments. Rufenacht and Goldstein agree that the midline should be placed in the center of the smile and its location be guided by symmetry and balance of that smile rather than facial anatomy.1,2 4. Principles of golden proportion These principles suggest that there is an ideal mathematical ratio (1.6 : 1 : 0.6)4,5,6 between the apparent rather than the actual widths of the centrals, laterals and cuspids when they are viewed simultaneously from the front. The discrepancy between the apparent and actual widths is explained by the positioning of these teeth along the curve of the arch. The principles of golden proportion are used as a guide rather than a rigid, mathematical formula. A sense of proportion must be displayed by these teeth and the dominance of the centrals must be readily apparent (Fig. 2).

Figure 3

Fig. 3 These teeth are chipped and discoloured. Due to excessive wear and trauma the centrals no longer exhibit proper proportions.

Figure 4

Fig. 4 This is a prematurely aged dentition. The patient hopes to change the shape and colour of her teeth and dramatically alter her smile.

Figure 5

Fig. 5 The centrals are the proper width but appear to be too wide because in reality they are too short. The correct length can be determined using the ratio of 4:5 and the clinical width of the centrals.

Figure 6

Fig. 6 To avoid excessive wear of the opposing dentition Empress porcelain will be used for the fabrication of the veneers. Its wear rate is between that of enamel and amalgam.

B. Specific Evaluation 1. Proportions of the Centrals The proportions of the centrals must be aesthetic and mathematically correct. 6 The width to length ratio of the centrals should be 4:5. A range for their width of 75%-80% of their length is most acceptable.7 Knowing the width we can thus calculate the ideal, esthetic length for worn, short centrals (Fig. 5,6,9,10). They must be the dominant teeth in a smile and they must display pleasing proportions. The centrals are the key to the smile.2 Their shape and location influences or determines the appearance and placement of the laterals and cuspids (Fig. 3,4,7,8). 2. Incisal edge position Phonetics help determine the incisal edge position (IEP). The incisal edges should lightly touch the vermilion border of the lower lip when making F and V sounds.8,9 This location then helps verify the length of each tooth. The principles of proportion are also instrumental in determining desired tooth length. The pitch of each anterior tooth is determined by the combination of correct lip support and the linguolabial position of the incisal edge. This location influences anterior guidance and the labial and lingual contours. All these factors play a dominant role in both esthetics and function.9 Correct Incisal Edge Position is crucial because it: a. determines the pitch of the anterior teeth b. contributes to establishing labial contours c. provides proper lip support d. influences anterior guidance e. together with anterior guidance determines lingual contours f. delineates our restorations by following the curvature of the superior border of the lower lip 3. Emergence profile The emergence profile must mimic the silhouette of the natural dentition from the facial and lateral views. A proper emergence profile will help avoid swelling and inflammation of soft tissue or conversely it will avoid the appearance of unsightly dark spaces in the gingival embrasure. The emergence profile must reproduce in porcelain, or other material of choice, the idealized, natural eruption of enamel from healthy gingiva (Fig. 9,10). 4. Labial contour The labial contour should exhibit two (gingival and incisal) planes. This should be evaluated from the lateral view. The most common error of anterior restorations is over contouring the incisal one third and thereby making the profile of the incisors too straight or too flat.10 The diagnosis for this consists of incisor profile evaluation and this assessment can be verified by locating the incisal edge position relative to the mucous cutaneous border of the lower lip during F and V formation.

The quality of the sound is not relevant because the patient can adapt to make the correct sounds even if the IEP is wrong. This contact location with the lower lip determines the most labial limit of IEP. The most lingual limit of IEP placement is determined by the position of the mandibular incisors and the patient's tolerable anterior incisal guidance.11 The incisors should exhibit facial curvature consisting of two planes (gingival and incisal [Fig. 9,10]). Curvature that is too pronounced will result in a very restricted, uncomfortable anterior incisal guidance. Absence of two distinct planes will result in flat incisor profiles. In both instances the IEP will be incorrect. C. Treatment of Embrasures 1. Incisal embrasures From the central to the cuspid there should be a natural, progressive increase in the size of the incisal embrasure (Fig. 7,8). This is a function of the anatomy of these teeth and as a result, the contact point moves apically as we proceed from central to cuspid. Failure to provide proper incisal embrasures will make the teeth appear too uniform. It will impart to the dentition the appearance of "Chicklets." The individuality of the incisors will be lost if their incisal embrasures are not properly developed. 2. Cervical embrasures Tooth material should not be exposed in the cervical embrasure area (Fig. 9,10). This may require lingual extension during preparation of the cervical, interproximal regions. Such preparation has been described as an elbow or dog's leg. "Black triangle disease" should be avoided. The darkness of the oral cavity should not be visible in the interproximal triangle between the gingiva and the contact area. At times this will require a longer contact area that will be extended towards the cervical. Improperly developed cervical embrasures that involve over extended, bulky restorations will result in swollen and inflamed gingival tissues.

D. Periodontally Related Issues 1. Periodontal health Periodontal health must be established prior to placement of final restorations and if at all possible even before commencement of restorative treatment. In order that the gingiva be healthy we must pay special care to all aspects of treatment from preparation and impression taking to temporization. The temporaries must display excellence of fit, marginal adaptation, emergence profile, gingival contour, incisal contour, and a properly developed occlusion in centric and excursive movement. If these standards of excellence are not met, then we will have recession, inflammation and disease and our final restorations will be doomed to failure even before they are inserted. 2. Margins placement and design Wherever possible, the margins should be 0.5 mm. apical to the height of gingiva. The margin design will vary from butt joint to chamfer depending on procedure, location and material of treatment. Bevel margins are reserved for metal. 3. Gingival contour and shape The gingiva should be pink, stippled, firm and it should exhibit a matte surface. The papillae should be pointed and should fill the gingival embrasure right up to the contact area. This will avoid "Black Triangle Disease." The cervical, gingival height of the centrals should be symmetrical. It can also match that of the cuspids. It is acceptable for the laterals to display the same gingival level. However the resultant smile may be too uniform and it is preferable to exhibit a rise and fall in the soft tissue by having the gingival contour over the laterals located towards the incisal compared to this tissue level on the centrals and cuspids. The least desirable gingival placement over the laterals is for it to be apical to that of the centrals and or cuspids. The gingival tooth interface on the mandibular incisors and the maxillary laterals should exhibit a symmetrical half oval or half circular shape. The maxillary centrals and cuspids should exhibit an interface that is more elliptical in it's shape. Thus the gingival zenith (the most apical point of gingival tissue) is located distal to the longitudinal axis of the maxillary centrals and cuspids (Fig. 9,10). The gingival zenith of the maxillary laterals and mandibular incisors coincides with their longitudinal axis. 4. Symmetrical cervical-incisal tooth length Symmetrical length is crucial for the centrals. It becomes less absolute the further we move away from the midline. Gingival height and the smile line are influencing factors. E. Materials and Finish 1. Choice of materials Our choices of materials, from luting cement to the type of porcelain we use, must be based on the specific, justifiable requirements of each case. The requirements of strength and aesthetics can be accommodated through the materials of choice for our restorations.

Figure 7

Fig. 7 From the central to the cuspid there should be a natural, progressive increase in the size of the incisal embrasure. The individuality of the incisors will be lost if their incisal embrasures are not properly developed.

Figure 8

Fig. 8 The labial anatomy should mimic the morphology of the natural dentition. The presence of lobes will allow a more natural and varied pattern of reflected light and their proper placement can influence the perception of width.

Figure 9

Fig. 9 Tooth material should not be exposed in the cervical embrasure area and 'Black Triangle Disease" should be avoided. The gingival zenith of the maxillary laterals and mandibular incisors should coincide with their longitudinal axis.

Figure 10

Fig. 10 The emergence profile must reproduce in porcelain the idealized eruption of enamel from healthy gingiva. The anterior restorations should exhibit facial curvature consisting of two planes. This will avoid making the incisors too straight or too flat.

For direct veneers, hybrids must be used in certain situations because of the requirements for strength, and in other circumstances microfills are needed for their polisheability and enamel-like finish. The right choice of materials can avoid "show through" of tooth structure and in the case of diastema, the darkness of the oral cavity. 2. Labial anatomy The labial anatomy should mimic the morphology of the natural dentition (Fig. 7,8). The presence of lobes is very important because it will allow a more natural and varied pattern of reflected light. The proper placement of lobes can also influence the perception of width. Incisors of similar dimensions can be made to appear wider by placing the lobes slightly closer to the interproximal surfaces and conversely teeth can be made to appear narrower by locating the lobes and height of contour slightly closer together. 3. Surface finish Consideration must be given to customizing the proper surface texture for each individual i.e., smooth vs. perikymata (stippling, rippling of enamel). The degree of polish and luster should be influenced by the visible, adjacent and opposing, untreated dentition. 4. Shade selection After the completion of any required bleaching on visible teeth that will not be covered, shade selection must be customized for each individual. It should be appropriate, natural and polychromatic. The body of the tooth can be fairly uniform in colour but the gingival third must be noticeably richer in chroma. The incisal has blue, violet and gray to convey translucency. Incisal clouds may also be present. If appropriate a thin halo can be incorporated in the restoration and a hint of faint, internal mamelons may be desirable in some situations. Maverick stains and crazing lines as long as they are faint and not overpowering can add to a pleasing result. Conclusion The incorporation of certain, universal principles in the design and formation of beautiful smiles must begin at the treatment planning stage. It will guide our treatment choices and often influence our preparation design. The product of our cosmetic efforts is always on display and it is subject to evaluation and critique by colleagues, patients and the public. Adherence to basic criteria of cosmetic dentistry and the essential guidelines that are utilized in rigorous, critical evaluations of our smile restorations, will allow us to achieve the desired results. References 1. Rufenacht C. Fundamentals of Esthetics. Chicago, IL: Quintessence Publishing Co. 1990. 2. Goldstein R. E. Esthetics in Dentistry. Philadelphia, Pa: J.B. Lippincott Co. 1976. 3. Miller E. C., Bodden W. R., Jamison H. C. A Study of the Relationship of the Dental Midline to the Facial Midline. J Prosthet Dent. 1979;41:657-660 4. Levin E. I. Dental Esthetics and the Golden Proportion. J Prosthet. Dent. 1978;40:244 5. Ricketts R. M. The Biologic significance ofthe Divine Proportion and Fibonacci Series. Am. J. Orthod. 1982;81:351 6. Lombardi R. E. The Principles of Visua Perception and their Clinical Application to Denture Esthetics. J. Prosth. Dent 1973:29:358 7. Chiche G. Pinault A. Esthetics ofanterior Fixed Restorations. Chicago: Quintessence Publishing Co 1993 8. Pound E. Personalized Denture Procedures. Dentist's manual. Anaheim, Californiai Denar Corp. 1973 9. Dawson R E. Evaluation Diagnosis and Treatment of Occlusal Problems. St. Louis, Mo: C.V. Mosby 1974 10. Dawson P. E. Determining the determinants of occlusion. Int. Periodont. Rest. Dent. 1983:6:9 11. Chiche Gerard J. Smile Rejuvenation: A Methodic Approach. Practical Periodontics and Aesthetic Dentistry. April 1993 Note: Some of this material is derived from accreditation protocol as established by the American Academy of Cosmetic Dentistry.

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