The Synesthetic Effect

George E. Kirtley, DDS


Yes, another article on cosmetic dentistry. I bet you can’t wait. If you haven’t seen it all by now…well, where have you been? Hopefully not stuck somewhere between “Should I break contacts?” and “Can you really bond to dentin?” All kidding aside, every article on cosmetic dentistry that is titled “Cosmetic Dentistry” is questionably titled. Why? Because we never just impact aesthetics when we cut tissue, and rarely in true aesthetic design do we limit our invasion to just tooth structure. We potentially impact the entire dynamics of the masticatory model, including the teeth, the periodontium, the temporomandibular joint, the muscles, and face; often failing to consider the true depth of our impact by not realizing the effect on our senses of taste, touch, sight, and hearing. Irfan Ahmad1 describes the effect that dental change can have on our given senses. The “Synesthetic Effect,” as it is termed, basically suggests that the more senses that can be positively impacted, the more positive, complete, and successful the result. This is not limited to dentistry. This concept is clearly noted in the entertainment industry and how the makers of movies strive to visually, audibly, and emotionally engage the viewer. In our medium of dentistry, or aesthetic restorative dentistry, we can stimulate the sense of sight by dramatically changing one’s smile. We can stimulate the sense of touch by creating the smoothness of good arch form and alignment and bite. Hearing the words of compliment can impact the auditory sense. Taste can be improved through the eradication of dental disease and design of prostheses. The synergy of all the above impact is what is artistically known as the sixth sense, emotion, which in the end can be the most powerful. So, when we treatment plan, we must equally consider the unseen parts and their profound impact toward an equally profound result. It is within our power to do so.

The following case (Figure 1) involves the consideration of all the above. In the treatment planning, much was divulged through the simple questioning and involvement of the patient in the interview process. It is during this time of casual conversation that you can truly visualize the scope of aesthetic need and the psychological impact of a compromised smile.2 The negative aspect of this patient’s smile was obvious not only in the eyes of the perceiver but, also, in her own eyes by how she tended to use her hand to cover her mouth when she spoke, along with an obvious reluctance to smile. We have all observed this in self-conscious patients. It is the visual sense that is most dramatically affected. However, the aforementioned non-appearance benefits were what she would ultimately realize to have an equal impact on the complete success of her case.

Figure 1a. Full-face preoperative photo. Figure 1b. Frontal 1:2 natural smile.
Figure 2a. Full-face pre-op, before and after using imaging software (Envision A Smile).
Figure 2b. Frontal smile pre-op, before and after using imaging software.
Figure 2c. Lateral smile pre-op and lateral smile, before and after using imaging software.

Comprehensive clinical, radiographic, and photographic examinations were completed. Mounted diagnostic casts and a mounted diagnostic wax-up were of course an integral part of the pretreatment analysis. Computer-generated imaging (Envision A Smile) was utilized to give the patient a preoperative visual of an anatomically correct image of the possibilities (Figure 2). To be able to show 3 perspectives (full face, frontal smile, and lateral smile) of this proposed change to the patient in advance of any treatment was significant in the acceptance of the case. It is easier to explain the various aesthetic options to a patient using visuals rather than with verbal explanations and descriptions. This also works extremely well in aiding communication with the dental laboratory team.3

“Of all our inventions for mass communication, pictures still speak the most universally understood language.”
–Walt Disney (b. 1901 – d. 1966)

Aesthetic Evaluation
Aesthetics were an obvious concern, characterized by the visual tension created from the ill-proportioned relationship of teeth to each other: teeth-to-lips and gingiva; teeth-, lips-, and gingiva-to-face; excessive gingival display; color of teeth; incisal wear; buccal corridor deficiency; and non-display of lower teeth.4

The existing dentition was a mix of old and defective restorations and crowns along with evidence of occlusal instability characterized by abfractions and incisal wear. The lateral incisors were congenitally missing and the cuspids had been moved orthodontically into the lateral position. The cuspids had been restored in an attempt to mimic lateral incisors, and the bicuspids restored to mimic cuspids. The obvious failure to address soft-tissue architecture stood as the primary cause of visual tension (Figure 3). The aesthetic failure of this original attempt started with the orthodontic translation of the cuspids into the lateral position. The resultant effect dramatically and negatively impacted functional and aesthetic position, ultimately requiring a more invasive approach for correction.

Complicating factors in substituting cuspids for missing laterals in the maxillary arch can be significant. They include but are not limited to the following:

1. Lack of canine eminence, creating narrow buccal corridors
2. Interference of the lingual cusp, of the bicuspid in cuspid position, with lateral excursions
3. Curved labial contour of the cuspid
4. Difficulty in managing the papilla due to line angle of cuspid versus lateral incisor
5. Labial lingual thickness of the cuspid versus lateral
6. Lack of framing of the dental arch as it relates to the corners of the mouth
7. Prominent cuspid osseous eminence versus a more flat osseous contour of a lateral.

Figure 3. Frontal retracted view. (Note the arrows depicting movement of gingival tissues and buccal corridors.)
Figure 4a. Frontal view with old
restorations removed. (Note the arrows depicting intended direction of gingival change.)
Figure 4b. Frontal view with pre-op provisional restorations in place.
Figure 5a. Flap fully elevated. Figure 5b. Provisional restorations placed to provide reference to intended margin
relative to osseous levels.
Figure 5c. A periodontal probe was used (not shown here) to measure difference between intended margin of restoration and the existing level of bone. Then, an end-cutting diamond (Brasseler USA) was used to remove bone to desired level.

Treatment Begins
To attain an aesthetic and functional result, a multidisciplinary approach was necessary. The aesthetic challenge was to reduce crown length and to attain crown length in the anterior segment at the same time. This would create a more proper gingival architecture and stage by which to aesthetically design the patient’s smile. The defective crowns were removed and teeth grossly prepared (Figure 4a). Preparation of the cuspids in the lateral position requires significant slenderizing/narrowing of the cuspid. Additional reduction/contouring in the cervical facial aspect to diminish and narrow the neck, to gain proper aesthetic emergence profile (to mimic an aesthetic natural lateral incisor), was also necessary. As we change the preparation design of the anterior teeth, we must also equally consider the visual effect upon the gingival architecture. Fabrication of provisional crowns to the ideal cervical position provided perspective as to the desired final gingival position. The provisional restorations (Figure 4b) clearly demonstrated the gingival excessiveness of the central incisors and gingival inadequacy of the laterals. Use of the computer-generated digital image also gave an additional perspective to the periodontist for the desired aesthetic gingival position.

Figure 6a. Reducing eminence of cuspid. Figure 6b. Horizontal releasing incisions in periosteum to allow for coronal positioning of flap.
Figure 6c. Flap repositioned around provisional crowns;
the gingival margin defined
excisionally with a scalpel.
Figure 6d. Emdogain (Straumann USA), an enamel matrix protein, placed on the root surfaces for 2 minutes; rinsed with sterile water.
Figure 6e. Flap sutured to place around provisional restorations.

Periodontal Surgery
The uniqueness of this case lies in the need to crown lengthen and crown shorten at the same time. Vertical incisions were made distal to the “lateral position” on both left and right sides extending up into the mucolabial fold. An incision was made around each of the teeth not involving the existing interdental papilla. A partial thickness flap was then elevated, exposing the underlying bony architecture. The provisional restorations were placed on the prepped teeth to give perspective to the margin location in relation to the underlying osseous anatomy (Figure 5a). This provided the periodontist a guide to perform osteoectomy and osteoplasty to the labial bony margin to promote ideal biologic width response with the proposed functionally aesthetic crown design (Figures 5b and 5c).

The pronounced eminence of the cuspid anatomy was gently flattened using a smooth diamond (Red Stripe [Brasseler USA]). This would ultimately allow for a more natural design seen around an aesthetic lateral incisor (Figure 6a). A periosteal releasing incision allowed the flap to be coronally positioned without tension around the cervical aspect of the provisional restorations (Figure 6b). The gingival margins of teeth Nos. 8 and 9 were then scalloped to ideal position using a No. 15C scalpel blade (Figure 6c). The root surfaces of all exposed teeth were planed and the smear layer removed using a pH neutral, 24% ethylenediaminetetraacetic acid (PrefGel [Straumann USA]). Next, an enamel matrix protein (Emdogain [Straumann USA]) was placed on the root surfaces for 2 minutes, and then rinsed with sterile water (Figure 6d). This provided an environment to enhance cementum development and regeneration of the flap to the root surface.5-11 The flap was then coronally advanced and sutured to position around the teeth and provisional restorations (Figure 6e).

The provisional restorations were then cemented with TempoCem (DMG America) and the patient was given postoperative care instructions requiring her to rinse twice a day with a chlorhexidine gluconate solution (Scrub-Stat 4% chlorexidine gluconate [Ecolab]), along with diligent post-op cleaning and stimulation of the surgical area.

During the healing phase of the maxillary anterior area, the lower arch was prepared and taken to completion. Preparation design on the lower arch was minimal in the anterior area due to the change in position of the upper anterior teeth. The “initial” functional guidance designs were worked out during the provisional phase of the uppers with the lower provisionals and, ultimately, with the lower restored arch.

The healing phase for the upper arch periodontal surgery required approximately 16 weeks (Figure 7). After this period of healing time, the patient was released from the periodontist and appointed for the restoration of the upper arch.

Figure 7. Provisional restorations at 16 weeks post-surgery. Figure 8. Occlusal view of the lithium disilicate (IPS e.max [Ivoclar Vivadent]) all-ceramic restorations on the model.
Figures 9a and 9b. (a) T-Scan Occlusal Analysis system (Tekscan) and (b) with scanner in use.
Figures 10a and 10b. Frontal view of natural smile (a) before and (b) after.
Figures 10c and 10d. Retracted 1:2 view (c) before and (d) after.
Figures 10e and 10f. Retracted 1:1 view (e) before and (f) after.

Maxillary Arch Preparation
The (surgical) provisional restorations were removed in the anterior. The previously prepared anterior teeth were refined and then the remaining teeth in the upper arch were prepared for full-coverage ceramic crowns. Slight alterations in the soft tissue, defining the architecture of the gingival margins in the anterior, were made using a portable diode laser (NV Microlaser [DenMat]).

A full-arch vinyl polysiloxane (VPS) impression (Flexitime Heavy/Light Body [Heraeus Kulzer]) was taken on the upper arch along with an opposing VPS impression (Flexitime) and an accurate bite registration (JET BLUE BITE [Coltene]). In addition, the following were included with the case for the laboratory team:

1. Photographs of the preparation shade
2. Photographs of the provisional restorations (full face and 1:2 retracted)
3. Preoperative photographs
4. Imaged (Envision A Smile) photographs (1:2 natural smile frontal view and lateral view)
5. Measured length of the central incisor provisional restoration
6. The mounted diagnostic wax-up
7. Face-bow record (Artex Articulators [Jensen Industries]).

Prior to seeing the patient, each restoration was evaluated on and off the model (Figure 8) for any obvious aesthetic concerns. The patient was seated and local anesthetic was administered. The provisional restorations were then removed. Next, the preparations and sulcular areas were cleaned (Consepsis Scrub [Ultradent Products]), rinsed, and dried. Then, the preparations were microetched and, again, rinsed and dried. Each restoration was tried in the mouth individually to evaluate margin integrity, and then en masse to evaluate contact relationships and occlusion. Once verified, the lithium disilicate (IPS e.max [Ivoclar Vivadent]) restorations were cleaned and then internally etched with hydrofluoric acid solution (in lieu of having the lab team do this etching step, we prefer to do this procedure chairside after try-in). The restorations were then thoroughly rinsed with water, steam cleaned, dried with clean and dry oil-free air, and the internal surfaces were treated with silane to enhance the chemical bond to the resin luting cement.

A self-etching, self-priming, dual-cure resin cement (RelyX Unicem [3M ESPE]) was used to lightly fill each of the anterior 6 crowns, and to also apply a thin bead of the cement around the preparation margins; then each restoration was pushed gently into place. This cement, which is dispensed easily from an automix cartridge, has excellent handling characteristics allowing for easy removal of cement excess in the gel stage with virtually no postoperative sensitivity.12 The cement was allowed to naturally cure to a gel state before any effort of excess removal was taken. At this stage, floss (Glide [Oral-B]) was used to remove the excess cement interproximally, and an explorer was utilized to remove the gel-stage cement from the lingual and facial margins.

A personal preference in the use of dual-cure resin cements: when using a dual-cure resin for cementing multiple restorations, I have found it less stressful and problematic to avoid any initial light curing (ie, the light wave technique) before clean-up, to eliminate the potential problem of having to remove cement that has cured too quickly/too much. After cleanup was accomplished, the resin cement in the anterior segment was light cured.

After cementation of the anterior segment was completed, the posterior segments were then cemented one side at a time with the same aforementioned protocols being followed. All areas were then additionally light cured.

Figure 11. Full-face post-op photo; a very happy patient with a beautiful and self-confident smile.

All margins were finished with Red and Yellow Stripe diamond burs (Brasseler USA), as needed. Then, final polish was accomplished with a prophy cup and diamond paste (Diamond Polishing Paste [American Dental Supply]) at all accessible margins. The interpoximal areas were further smoothed with Yellow finishing strips (Brasseler USA) and diamond polishing paste, and again flossed.

Gross occlusal adjustment was done, removing any obvious prematurities. The patient was appointed for a 24-hour post-op to recheck the occlusion, done to eliminate the potential inaccuracy of the anesthetic effect in evaluating the bite. Final occlusal adjustment, utilizing T-Scan Occlusal Analysis with BiteForce Dynamics (Tekscan), was completed the next day. The T-Scan (Figure 9) is a system that provides dynamic occlusal measurement—revealing the level and timing of force on individual teeth and the occlusal stability of the overall bite.13 The ability to accurately interpret “How does that feel?” from a patient, while asking the patient to provide feedback from tapping on articulating paper, is brought into perspective when seeing the T-Scan in action; much inaccuracy, as compared to the use of articulating paper alone, is quite often divulged. Once the necessary adjustments were made, the final polish was imparted to the porcelain surfaces (Dialite Intraoral Porcelain Polishing Kit [Brasseler USA]). In our cases, I rarely have significant adjustment on delivery of the case; this is a testimonial to the importance of proper record taking throughout the treatment process and the quality of the laboratory team involved in fabricated the restorations (San Diego Aesthetic Dental Studio; Hak Joo Savercool, ceramist).

In the case presented, aesthetic concerns on the upper arch differed greatly from the lower arch, and much of the preparation design on the lower arch was minimal. The anterior segment of the maxillary arch presented unique preparation challenges. The length-to-width ratios were massively improved via the surgical crown lengthening and shortening procedures. Preparation design of the central incisor and cuspid (in lateral position) required significant interproximal and subgingival attention. The location of the preparation design in these areas allowed for favorable aesthetic and biologic design of the restorations, resulting in the ability to create a natural emergence profile while at the same time closing the dark triangles that existed in the preoperative restorations. The added length (cervically) on the central incisors, with combined shortening of the incisal edge along with repositioning of the gingival margin coronally on the cuspids, provided a complete change in perspective of the anterior smile zone segment (Figure 10). This, along with minimally opening the vertical dimension of occlusion, provided the necessary room to ideally address the incisal/lingual functional relationship between the lower incisal edge and the lingual of the upper central incisors. Anterior/lateral guidance and proper space for a healthy envelope of function were predictably attained in the provisional stage of treatment and replicated in the permanent ceramic restorations.

Postoperative commentary by the patient is always revealing. Obvious to the patient is the joy of visual change and improvement of aesthetics. However, as so often occurs, it is the contribution and detail of the unseen components of smile design—the comfort of feel, the enhancement of taste, and the hearing of compliments—that equally impact the overall interpretation of case success (Figure 11).

The author would like to thank Dr. Jay Beagle, periodontist, of Indianapolis, Ind.


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Dr. Kirtley has been involved in the field of cosmetic dentistry since 1985 and has positioned himself as an international leader in dentistry through teaching, lecturing, writing, and providing aesthetic smiles seen on patients throughout the United States and Europe. He completed his DDS at Indiana University. He is an accredited member of the American Academy of Cosmetic Dentistry and the British Academy of Cosmetic Dentistry, and presently one of a very few dentists worldwide to be accredited both in the United States and the United Kingdom. He is a part of the leading cosmetic teaching institution, The Aesthetic Advantage, located at the Rosenthal Institute in New York City. Additionally, he serves as a visiting lecturer at New York University College of Dentistry. He can be reached by phone at (317) 841-1111 or via email at

Disclosure: Dr. Kirtley receives honoraria for lecturing on behalf of Heraeus Kulzer but was not compensated for writing this article.