Diastema Closure: A Restorative Design and Treatment Challenge

INTRODUCTION
In my last article (March 2015, Dentistry Today), I addressed the importance of impacting as many of the senses in our aesthetic designs as possible (ie, visual, auditory, touch, taste, and the artistic sense of emotion); the rationale being, the more of the senses we can positively impact, the greater the success of our case (Synesthesia).¹ Most obvious in aesthetic dentistry is the capability that we have to impact the visual sense. Offenses to our eye and any visual tension that is created can manifest in many different forms including the following: excess spacing, crowding, the gummy smile, discoloration, and combinations of all of these. Approaches to treatment of these are as varied as the look each presents.

Perhaps no condition is more sought out to correct than the patient who has a large diastema centered in his or her smile (Figures 1 to 4). Causes of this condition are varied. A developmental disproportion of tooth size to the arch size (arch length redundancy); a pull, or force, created by the labial frenum; or behavioral habits (thumbsucking at early age) can all contribute to an unsightly space between teeth in the smile zone that most particularly impacts the central incisors. However, germane to our discussion is not so much the etiology as it is treatment methods to counter this.

Orthodontic treatment is always first in the line of consideration of treatment modalities. It provides the patient with the opportunity to correct most alignment issues. However, what it cannot do is impact tooth mass or tooth anatomical design. It does not impact shade change, and in certain circumstances cannot deliver the optimal occlusal interrelationship between maxillary and mandibular teeth. The decision to approach treatment orthodontically or restoratively is one that must be shared among the patient, orthodontist, and aesthetic restorative dentist.

In this article, I will focus on the challenge in treatment and design of arch length redundancy, or excess spacing in the form of the anterior diastema.

CASE REPORT
Diagnosis and Treatment Planning
The patient desired improvements in proportion and shade, along with the closure of the diastema between her central incisors. The size of the space between the upper central incisors (teeth Nos. 8 and 9) was significant. The lateral incisors were rotated and the overall shade was unaesthetic. In addition, there was soft-tissue imbalance on each side of the dental midline and tooth mass was in disproportion to facial form. To our advantage, the patient was in a stable and functional occlusion.

Treatment choices proposed to the patient included the following:

1. Orthodontic realignment without consideration of aesthetic restorative involvement. Estimated treatment time 2 to 3 years.

2. Orthodontic realignment to position the anterior teeth more ideally along with aesthetic restorative design including bleaching and subsequent matching of porcelain laminate veneers on teeth Nos. 7 to 10 to that bleached shade of her natural dentition. Estimated treatment time one to 2 years.

3. Aesthetic restorative design involving soft-tissue alteration, porcelain laminate veneers on all teeth in smile zone (Nos. 4 to 13) with enhancement of anatomical design/proportion and shade change. Estimated treatment time 6 to 8 weeks.

Orthodontic realignment without consideration of aesthetic restorative involvement was not a consideration by the patient. Orthodontic alignment of the anterior segment would have resulted in equally spacing the anterior teeth so as to make a more proportioned position between them. Porcelain laminate veneers would then be designed to fill the diastemas equally; however, this would still fall short of ideal proportion of all teeth in the smile zone to each other and proportion to the surrounding and critically important features of the gingiva, lips, and face. The patient also declined this option.

The third option would utilize aesthetic restorative procedures, providing comprehensive answers to the aesthetic challenges, both intraorally and extraorally. Intraorally in that we were able to create teeth that were inherently proportional to one another and to the surrounding gingiva, and extraorally in that we were able to create proportion to the lips and face that frames them.² This was the option chosen by the patient.

Figures 5 to 7. Side-by-side views of pre-op full face, frontal natural smile, and lateral natural smile, along with imaged views of each created by imaging software (Envision A Smile).

Much has to be considered in the successful outcome of a case involving significant space closure. The first consideration is to be able to communicate with and educate the patient on what is aesthetically possible. In a profession and procedure that is visually based (especially by the patient), all the words of even the greatest communicator will place second to the visual representation of what is to be attained. This is done in my practice through the use of cosmetic imaging utilizing Envision A Smile Imaging Software (Envision A Smile). Through this technology I am able to represent, in an anatomically correct way, the visual possibilities of aesthetic change. I am able to do this from the following 3 perspectives (Figures 5 to 7): (1) full-face view, (2) frontal view, and (3) lateral view.

The full-face view allows the patient to visualize the extraoral benefit of dimensional and color change. The impact of this is very telling on the overall facial volume change in the lower third of the face (Figure 5).

Figures 8a and 8b. Gürel’s illustration of interproximal reduction technique. (With permission to reprint. Gürel G. Porcelain laminate veneers for diastema closure. In: Gürel G, ed. The Science and Art of Porcelain Laminate Veneers. Chicago, IL: Quintessence Publishing; 2003:371-372.)

The frontal view perhaps is the most accurate representation and allows the patient to see the close-up impact of dimensional change (Figure 6). Within the context of this, the patient can appreciate the effect on increasing volume and broadness of the smile through enhancing buccal corridor deficiencies, tooth length, gingival alteration, and of course, color/shade.

The lateral view perspective is unique (Figure 7) and I believe has an extraordinary impact on the patient when explained in this manner, as I do in my consultations. “This is a view that is not readily seen by you because it is simply a difficult angle to do so. However, this is a view that is significantly viewed in social settings. When you are in a crowd of people, most will see or view you from this (lateral) position.”

It is here that the importance of filling out the smile zone (in terms of proportion and shade) is most important. Designing a smile and doing it with a resultant natural appearance requires that it encompass the smile zone (the number of teeth revealed through the natural animations of smiling and laughing and function). If a patient desires only to treat the anterior 6 teeth (as is often requested), then adherence to the patient’s natural existing shade and often proportion of teeth in the bicuspid, molar areas must be followed, or a gross offense in smile design is committed.

Figures 9 and 10. Gürel’s gingival zenith alteration and adjacent clinical example. (With permission to reprint. Gürel G. Smile design. In: Gürel G, ed. The Science and Art of Porcelain Laminate Veneers. Chicago, IL: Quintessence Publishing; 2003:67-71.)

So, when that patient comes along who wants to change shade, change proportion, change position of only the front 6 teeth and disregard the posterior teeth in the smile zone, we must somehow communicate the error of this way of thinking. In preparation for this request in my consultations, I will often image (in addition to the 3 views aforementioned) only the front 6 teeth with the changes of color and proportion, and show the patient. It is incredible how often this clarifies my rationale to patients. It is this lateral view perspective in imaging that provides this opportunity. I am not about doing any more dentistry or involving any more teeth in treatment than is necessary to attain the results that I know the patient wants. Sometimes it is one tooth; sometimes it is a full-mouth reconstruction.

This patient chose to pursue treatment involving the upper 10 teeth along with the recommended changes in gingival architecture. Her choice was solely based upon all the information and choices she was given. I simply educated her on all the possibilities and allowed her to make the decision. This is the mark of a relaxing and comfortable consultation that often results in acceptance and success of the treatment plan.

Clinical Treatment Begins
In the case of excess spacing/diastemas, the goal is to fill the spaces that exist in a proportional aesthetic manner. In every case, a preoperative mounted diagnostic wax-up is fabricated. This, along with the computer-imaged views, allows me to have an accurate blueprint of each case before even touching a patient’s teeth (suffice it to say, full-mouth radiographs, clinical examination, full photographic series, health history, etc, were also completed preoperatively).

Figures 11 and 12. Pre-op closeup of interdental area between teeth Nos. 8 and 9, along with occlusal view of gingival interproximal alteration.

Design Concept
Evaluation of the preoperative models is critical in determining the amount of soft-tissue change that will be necessary and the extent of tooth preparation. From a mathematical perspective, the amount of space between the central incisors is measured. To fill this space equally from each side, half the distance between the teeth is calculated and then added to the respective right and left central incisors. Obviously, when this is done, it is important to understand that reduction of the distal aspect of the centrals has to be undertaken to maintain aesthetic length-to-width ratios. When this occurs, space is then created between the centrals and laterals, laterals and cuspids, cuspids and bicuspids, and so on, depending on the number of diastemas or spaces to be closed. Preparation in this manner is undertaken until all space demands are filled in a proportional way (Figure 8).³

Gingival Alteration
As previously mentioned, to move teeth mesially to close a space, the clinician must reduce distally to maintain semblance of proportion. As this is done, the architecture of the gingiva must also change. Without consideration of this, the end result would be restorations with a mesial angular tilt creating visual tension and a compromise of the optimal aesthetic result.⁴ To avoid this unaesthetic dilemma, we must contour the zenith of the gingival margin and move it in the same direction as to what the intended result for the restoration is (Figure 9).

Another important consideration in the treatment of the soft tissue is that of the interdental papilla, especially where it exists between the central incisors. The goal is to create interdental gingival architecture that replicates a nicely pointed papilla. As can be seen in this patient, the diastema is filled with tissue that anatomically is flat at the soft-tissue crest (Figure 10). With the use of a diode laser (NV Microlaser [DenMat]), thinning of the mesial aspect of the interdental area on each of the central incisors is accomplished. The papilla area is sculpted and narrowed subgingivally (Figure 11). It is important to probe this area preoperatively to know the extent of sulcular depth available so as not to impinge upon the biologic space and create iatrogenic pathology.⁵ Additionally, it is important not to reduce the papilla vertically. This guards against the potential creation of a dark triangle. This area of soft tissue alteration, I believe, is singly the most important aspect of treatment in the diastema closure. It provides the opportunity for attainment of an anatomically correct papilla and ultimately dresses the accompanying restoration with a natural and aesthetic emergence profile and surrounding gingival contour. I will usually do this in advance of any tooth preparation. It provides me with the proper stage by which to prepare the teeth.

Preparations
In most diastema closure cases, the amount of tooth preparation facially is fairly minimal, especially if the arch alignment is good. A proximal slice subgingivally and mesially, extending to the lingual proximal line angle, is my first step in tooth prep design (teeth Nos. 8 and 9). The same is done on the distal aspect to reduce the tooth by the amount to be added in the diastema being closed. A key point of preparation uniqueness in diastema closure is extending the prep design through the interproximal extending to the lingual proximal line angle. This allows the ceramist to provide the proper interproximal contour along with the opportunity to apply opacifiers within the ceramic restoration design to block out the darkness of the oral cavity that would otherwise show through in the diastema area (Figures 12 to 16).

Incisal and facial reduction/preparation follows. The amount of reduction is dictated by the space needed to meet the structural and aesthetic demands of the ceramic chosen. The use of the aesthetic pre-evaluative temporaries (APTs) over the nonprepared teeth provides a means to visualize the final outcome and to ensure conservative tooth preparation from the facial aspect.⁶ This is normal protocol on all aesthetic cases I do. It is a failsafe method to avoid over-reduction of teeth. The resultant outcome is conservation and maintenance of the integrity of the all-important enamel along with greatly minimizing the likelihood of postoperative sensitivities and problems.

Final details in preparation design lie in the gingival preparation margin and line angles. The gingival prep margin or finish line location is determined by the underlying tooth/preparation shade. If the tooth/prep shade is light, then finishing the margin at or above the gingival margin is applicable. For example: if the underlying tooth/prep shade is an A-1 (or whatever shade system you use) and the desired shade of the restoration is A-1, then you can logically finish at or above the gingival margin and create a nice blend. This is especially true if the cervical aspect of the prep is minimal and you utilize a more transparent ceramic. A very natural gradation of shade occurs in these scenarios. If, however, the tooth/prep shade is a darker color, say A-4 (tetracycline discoloration as an extreme example), then it becomes imperative to finish the preparation margin subgingivally and further interproximally so as to provide an emergence shade that is uniform and not dark at the gingival or interproximal areas. The use of opacifiers and more opaque ceramic shades is often necessary in this type of case. Offense to these preparation design principles usually will manifest as an obvious and unaesthetic line of demarcation between the preparation and the restoration. This is an aesthetic failure and must be redesigned to achieve an optimal result. Final impressions were taken using a vinyl polysiloxane (VPS) (Flexitime Heavy Body/Light Body [Heraeus Kulzer]) and provisional restorations placed using Venus Temp 2 Provisional (Heraeus Kulzer) replicating the dimensional positions of the diagnostic wax-up. Records of length, incisal edge position, impression of the provisionals, and shade, along with photographs preoperatively and imaged views (Envision A Smile) were forwarded to the laboratory team (Hak Joo Savercool, ceramist at the San Diego Aesthetic Dental Studio).

The choice of ceramic used in this case was lithium disilicate (IPS e.max [Ivoclar Vivadent]). This high-strength polycrystalline ceramic choice would provide the needed high aesthetics necessary for this diastema closure case as well as long-term predictability.

Delivery of the Final Restorations
The provisionals were removed and preparations cleaned and debrided using Consepsis Scrub (Ultradent Products]), then rinsed and dried. Next, all the restorations were examined on the model and then individually placed upon the preparations. Each was evaluated for marginal adaptation and interproximal contact and initial occlusal position. The lithium disilicate restorations were then cleaned and prepared for placement. This entailed steam cleaning; applying phosphoric acid gel for about 15 seconds on the internal surfaces of the restorations; rinsing the restorations thoroughly with water; and the placement of silane (Pulpdent) and a universal adhesive (Scotchbond Universal [3M ESPE]). 

Preparation of the tooth surface entailed microetching (MicroEtcher [Danville Materials]), etching with phosphoric acid (15 to 20 seconds), then rinsing and gently drying (but not desiccating) the tooth surfaces so as to maintain an optimal environment for bonding.

Increments of translucent light-cured resin cement (RelyX Veneer [3M ESPE]) were placed inside each restoration along with a small increment along the margin of the preparation, and each was then placed into position. Next, any excess cement was gently wiped from the face of each restoration with the edge of a cotton roll moving from the surface of the restoration toward the margins. A sable brush was then used to remove the excess at the gingival margin and interproximally. The soft bristles of the sable art brush ensure smooth removal and minimize potential trauma to the soft tissues. Starting with the central incisors and progressing posteriorly, each restoration was gently held in place and spot tacked to secure its position. Floss (Glide [Oral-B]) was then used to remove excess cement and to burnish the margins interproximally. Light curing was then done, positioning the curing light (Elipar [3M ESPE]) from the facial, interproximal, and palatal positions.

Adjustment of the occlusion was minimal due to the detail of good records and an outstanding laboratory team. Cleanup entailed minimal time and effort and was completed by polishing the adjusted areas of porcelain and all margins (Figures 17 and 18).

CLOSING COMMENTS
Each case of aesthetic dentistry is a work of art requiring treatment methods and protocols specific for each case type. To engage in the treatment of a case without the realization and knowledge that each demands a different technique or approach often results in inaccurate preparation. This translates into inferior outcomes aesthetically and greater likelihood of postoperative complications.

Acknowledgment
The author would like to acknowledge Dr. Galip Gürel for the illustrations taken from his book The Science and Art of Porcelain Laminate Veneers.

References

1. Ahmad I. Four esthetic tales. In: Romano R, ed. The Art of the Smile: Integrating Prosthodontics, Orthodontics, Periodontics, Dental Technology, and Plastic Surgery in Esthetic Dental Treatment. Chicago, IL: Quintessence Publishing; 2005:82-92.
2. Chiche G, Pinault A. Artistic and scientific principles applied to esthetic dentistry. In: Chiche G, Pinault A. Esthetics of Anterior Fixed Prosthodontics. Chicago, IL: Quintessence Publishing; 1993:13-31.
3. Gürel G. Porcelain laminate veneers for diastema closure. In: Gürel G, ed. The Science and Art of Porcelain Laminate Veneers. Chicago, IL: Quintessence Publishing; 2003:371-372.
4. Gürel G. Smile design. In: Gürel G, ed. The Science and Art of Porcelain Laminate Veneers. Chicago, IL: Quintessence Publishing; 2003:67-71.
5. Kois JC. New paradigms for anterior tooth preparation. Rationale and technique. Oral Health. 1998;88:19-30.
6. Gürel G Atlas of porcelain laminate veneers. In: Gürel G, ed. The Science and Art of Porcelain Laminate Veneers. Chicago, IL: Quintessence Publishing; 2003:248-271.

Dr. Kirtley 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. He also serves as a visiting lecturer at New York University College of Dentistry. He 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 can be reached at (317) 841-1111 or via email at the address george@smilesbygeorge.com.

Disclosure: Dr. Kirtley reports no disclosures.