Advanced Techniques for Diastema Closure. A Microscopic Perspective

Автор: Dr. David J. Clark, DDS
AMED Founder & Past President 2002-2004
Статья опубликована в журнале CONTEMPORARY ESTHETICS | september 2007

In dentistry, much of what we do and read is anecdotally driven. Additionally, most clinical assessments over the past century were done with little or no magnification, meaning they were based on incomplete visual information. Our opinions have been shaped by decades of clinical studies about restoration failures, marginal integrity, tissue health, and many other parameters. It seems that our house of dental decision-making has been built on sand.

Today, a small but growing number of dentists are routinely operating with high magnification levels. Once a clinician begins his or her journey using advanced magnification, that clinician may begin to reinvent many procedures (Figures 1 and 2). Users of advanced magnification also may find themselves pressed to problem solve on the fly as they encounter visual cues that are new to them, and neither the problem nor the solution is addressed in mainstream dental publications. This article will discuss how, when using magnification, some clinicians noted the benefits of a rounded marginal profile. A new anatomic matrix system that this author has developed (Bioclear) and its use with the Injection Molded Composite technique will be detailed.

Figure 1. Author using an operating microscope with multiple levels of magnification – 2.5×, 4×, 6×, 10×, 16×, 24×. Xenon coaxial light provides shadowless illumination in previously inaccessible visual environments, such as deep in the sulcus
Figure 2. After sharpening a red wax pencil at 24×, die trimming and margin identification was performed at high level 8×-12× magnification. The cleaner the margin, the better the tissue response and the deeper in the sulcus you can safely operate

Magnification provides a squared, not linear, relationship between powers of magnification and picture elements or pixels of information. In other words, clinicians working at 3.5× see 10 times more visual information, and at 10× clinicians see 100 times more than with the naked eye. If clinicians move to 25× for brief periods of observation throughout the clinical day, they will see 625 times more than with the naked eye1 (Table 1).

Table 1. Magnification and Visual Information


10× 16× 25×

Information Content

16× 100× 256× 625×

Picture Element

660 2640 10560 66000 168960 412500

Ethics and Diastema Closure

Many esthetic procedures can improve the structural integrity of the tooth and also facilitate better health of the surrounding gingiva. Diastema closure, at least in the anterior sextant, does not give either of these secondary benefits. Sadly, the esthetic diastema closure often results in significant compromises in the root–crown architecture, and increased plaque retention with subsequent deterioration in periodontal health. Increased caries activity often follows. Any discrepancy greater than 50 µm will cause untoward tissue response2-5. When using advanced magnification, clinicians found that a bulbous contour is actually far less detrimental than other often ignored and clinically unseen factors5. To «do no harm» performing elective diastema closure, clinicians must elevate their game.

Tables 2 and 3 highlight a magnification-based approach to the multiple factors that determine the gingival reaction to prosthetic and restorative intervention into the sulcus and pericrestal zones. Once clinicians begin to analyze margins with advanced magnification, they can begin to discuss margins in 3 axes — x, y, z — (Table 2). Also, clinicians can see how certain parameters can affect the bioburden on gingival tissue, resulting in chronic tissue inflammation. Table 3 lists the parameters to be avoided because they will tip the scale and create an excessive bioburden, compounding any negative factors from a poorly constructed margin junction.

Table 2. Microscopic Protocol for Margin Evaluation of Porcelain or Composite


Sub ←→ Plus


Undercontoured Emergence Profile ←→ Rounded Emergence Profile


Short ←→ Long


Sub is an underhang (shelf of tooth structure)
Plus is an overhang (shelf of restorative material)


Undercountered Emergence Profile is concave at the enamel and cementum intersection
Rounded Emergence Profile is convex, causing a «potbelly» effect, at the enamel and cementum intersection


Short occlusal – gingival line
Long occlusal – gingival line

Ideally, a restoration margin should be centered along the 3 axes (←→)

Table 3. Parameters for Maximizing Total Potential Tissue Health

No residual cement or calculus apical to finish lines

No root roughness from errant bur movements

No microroughness or porosities of porcelain or composite

No microleakage

Not avoiding these parameters can create an excessive bioburden, compounding any negative alignment on the axes in Table 2.

Tables 2 and 3 adapted from: Clark DJ, Kim J. Optimizing gingival esthetics: a microscopic perspective. Oral Health. April 2005; 95:116-126.

Extreme Diastema Closure

When patients ask that large diastemas be closed, alternative choices should always be discussed; however, patients will sometimes choose the most expedient option, such as direct composite. When faced with this challenge, clinicians have limited options:

Option 1 — No Matrix:
In the severe diastema case featured in this article, it appears that the previous clinician used the papilla as the gingival matrix. This resulted in a good esthetic space closure, but a biologically horrific contour (Case Photos 1-4). A sharp 90° angle combined with a lumpy and porous surface created a poor environment for soft-tissue health. Note the torrent of blood visible as the removal of old composite is performed (Case Photo 5).

Option 2 — With Matrix, With Wedge:
The problems with traditional clear mylar strips are that they are flat and require wedging, do not conform to the tooth, and are nearly impossible to maintain deep in the sulcus. The result is often an esthetic compromise. Holding all 4 ends of the strips while simultaneously light-curing is always a challenge (Figures 3-5).

Figure 3. Midtreatment view of a composite replacement on tooth No.8. Note the flat mylar strip does not conform to a round tooth
Figure 4. Wedge placement only exacerbates the flat contour
Figure 5. Flat embrasure, gingival diastema, and point contact are classic dilemmas of traditional anterior composite technique. This incisor embrasure has hygienic contours, but a black triangle at the gingival embrasure

Option 3 — With Matrix, Without Wedge:
This approach can yield the worst of both worlds, incomplete space closure and gingival overhang.

Option 4 — Bioclear Matrix System and Injection Molded Composite technique:
With this technique, the Bioclear matrices intimately adapt to the gingival margins and duplicate full rounded contours (Figure 6).

  1. Use the total-etch technique on the preparation.
  2. Place a lightly filled bonding resin, such as OptiBond Solo Plus (Kerr Corporation).
  3. Inject a flowable composite (Figure 7).
  4. Inject a paste composite (Figure 8).
  5. Light-cure all 3 resins together for a seamless filling (Figures 9-10).
Fig 6. Bioclear matrix on tooth Fig 7. Injection of a flowable
composite into the matrix
Fig 8. Injection of a paste
composite into the matrix
Figure 9. In this extreme diastema closure, maxillary Bioclear matrices are modified and slide to the depth of the sulcus without lacerating the tissue. Note the tissue blanching. Also note that the anatomic shape allows hands-free and wedge-free use as the matrices hug the teeth
Figure 10. Immediately after using the injection molding technique, the matrices move nicely to close the incisal gap but continue to hug the cervical area of the teeth. The sulcus itself provides stabilization

Case Report

The featured case demonstrates retreatment of a classic iatrogenic diastema closure. A 29-year-old woman reported with chief complaints of oral malodor, bleeding gums, brown stain, floss shredding, and incomplete diastema closure in the area of teeth Nos. 8 and 9. The patient desired complete diastema closure and resolution of the above mentioned problems. She had previously received composite restorations to close her diastema. A plan including preprosthetic orthodontics to evenly distribute the spacing followed by porcelain laminates was presented to the patient. She declined the comprehensive approach and was given informed consent regarding the esthetic compromises before beginning treatment.

Case Photo 1, 2. Preoperative view. Note the dingy interproximal space between
teeth Nos.8 and 9. Pigmented tissue camouflages the cyanotic tissues
Case Photo 3. Prewedging compresses the papilla and allows enhanced visualization of the sulcus
Case Photo 4. After 3 minutes the wedge was withdrawn to reveal unacceptable previous treatment and offending sharp ledge of composite. Vision, retraction, and tissue manipulation are subtle building blocks in modern microdentistry
Case Photo 5. Significant hemorrhage associated with the well intentioned but iatrogenic composites

The treatment plan chosen was to place Bioclear matrices with the Injection Molded Composite technique. First, the old composite was removed with a coarse flame-shaped diamond. Then the gingiva was lightly sculpted to create space for the delicate Bioclear sectional matrix (Case Photos 6-8). This sculpting can be accomplished with a mini tip and electrosurgery, laser, or sodium bicarbonate spray. In this case, sodium bicarbonate spray was used to simultaneously sculpt tissue and clean and detoxify the sickly cementoenamel junction surfaces.

Case Photo 6. Old composite was removed and the area was sprayed with sodium bicarbonate (Prophy-Jet, Dentsply International)
Case Photo 7. High magnification (16×) view of Case Photo 6
Case Photo 8. Tissue was stabilized with ferric sulphate (Ultradent Products Inc). Fluid control must be absolute because no wedge will be used

Next we see an occlusal view of the Bioclear matrix (prototype stage) with rounded, anatomic adaptation to the root (Case Photo 9). No wedge is required to press the matrix to position.

Case Photo 9. Bioclear matrices in position. Note that they are used hands-free and wedge-free

The immediate postoperative result is featured in Case Photo 10. Because the patient had chosen young incisal mamelons from the tooth library, the teeth were lengthened and mamelons with vertical grooves to mitigate the squareness of the tooth were built into the anatomy.

Case Photo 10. Immediate postoperative view. Final polish was accomplished with a combination of discs and rubber points

Two-week follow up (Case Photos 11-12) showed improved tissue health in spite of the fact that the gingival contours are far more bulbous than in the first treatment.

Case Photo 11, 12. The final restorations, 2 weeks after treatment. High magnification (16×) view


The «magnification escalation» in dentistry is likely to continue. With advanced magnification, there are previously unthinkable possibilities. The extreme diastema closure represents one such possibility. New techniques and instruments are currently being developed to meet the needs of this growing segment of practicing dentists. The concept of rounded marginal profiles with exquisite tissue health is a significant departure from the past. Restorations created using the Injection Molded Composite technique and with anatomically specific matrices are a glimpse into the future.


Dr. Clark has financial interest in Bioclear and Interproximator matrix system components. The techniques described in the article are the intellectual property of the author and can be used without charge by permission. Further information and hands-on courses are available from the author.


  1. Mora AF. Fundamentals of advanced magnification. Presented at: The Academy of Microscope Enhanced Dentistry Scientific Session; November 4-6, 2003; Scottsdale Ariz.
  2. Lang NP, Kiel RA, Anderhalden K. Clinical and microbiological effects of subgingival restorations with overhanging or clinically perfect margins. J Clin Periodontol. 1983; 10:563-578.
  3. Clark DJ, Kim J. Optimizing gingival esthetics: a microscopic perspective. Oral Health.2005; 95:116-126.
  4. De Boever JA, De Boever AL, De Vree HM. Periodontal aspects of cementation: materials, techniques and their biologic reactions [in French]. Rev Belge Med Dent. 1998; 53:181-192.
  5. Sorensen SE, Larsen IB, Jörgensen KD. Gingival and alveolar bone reaction to marginal fit of subgingival crown margins. Scand J Dent Res. 1986; 94:109-114.
  6. Sorenson JA. A rationale for comparison of plaque-retaining properties of crown systems. J Prosthet Dent. 1989; 62:264-269.