Direct Bonding in Diastema Closure - High Drama, Immediate Resolution

by Nathan Blitz, B.Sc., DDS

This article outlines the technique for "one appointment" closure of spaces or gaps between teeth.

Direct bonding calls on our understanding of basic principles of tooth sculpting and contouring.1 It challenges our knowledge of smile design, arch form, tooth morphology and arrangement. Furthermore the actualization of our dental vision tests our skills and is, at times, intimidating and exhilarating. Diastema closure results in dramatic, immediate smile improvement which enhances the patients appearance and may have a positive influence on emotional health and self esteem.

Chief Complaint

This patient wished to "get rid of the gaps" between his teeth. He was not happy with the appearance of his smile due to the color and shape of his incisors. Most of all, he detested his diagtemag (Fig 1a, b).

History

This 43 year old Caucasian male is in excellent health. He is a successful businessman with a background in marketing. In the past he has spoken to various dentists about diastema closure. The advice he was given could be classified in one of the following categories:

Leave it alone
See an Orthodontist
Extract the centrals and place a bridge
Place crowns.

He rejected these options and was referred to me by a colleague.

Past dental history consisted of placement of composite and amalgam restorations, endodontic treatment of 1.1, extractions and conservative soft tissue care by a periodontist.

Clinical Examination

A thorough clinical examination along with radiological interpretation of all film records revealed no abnormalities or pathology. Lamina dura is distinct and good bone height is present. There are no TMJ symptoms. Tooth 1.1 has had endodontic treatment. Periodontal health is indicated by the firm, pink, stippled gingiva and the absence of any pocket depth greater than 3 mm. Missing teeth include all four first molars and all four wisdom teeth. The second molars have tipped and drifted mesially so that 1.7 is contacting 1.5. A space of 1.3 mm exists between 2.7 and 2.5. The space between the mandibular molars and bicuspids is 4.5-5 mm There is a 3.5 mm overjet and 40% overbite. Incisal edges of 1.1 and particularly 2.1 are chipped and worn. Numerous vertical and horizontal fracture lines are visible and areas of discoloration are present. Diastema width between the centrals is 5.2 mm Between the left cuspid and lateral it is 3.1 mm. The spaces between the other incisors measure 1 mm each (Fig. 1c, d).

Fig. 1a This patient was not happy with the appearance of his smile due to the color and shape of his incisors. He wanted to "get rid of the gaps" between his teeth.

Fig. 1b. His smile seems unnatural because he is consciously trying to hide the maxillary incisors with his lower lip. He showed this much tooth in his smile only for the slides.

Fig. 1c. There is an excess of space available along the anterior perimeter of the arch.

Fig. 1d The diastema between the left lateral and cuspid measures 3.1 mm and 5.2 mm between the centrals.

Fig. 2a Total excess space from the mesial of the right cuspid to the mesial of the left cuspids is 11.3 mm.

Fig. 2b The patient refused orthodontic treatment but was determined to have his diastemas closed immediately.

Fig. 2c Direct bonding was introduced, hopefully, as a prelude to orthodontics and porcelain veneers. Should he opt to have orthodontic treatment, L mm. Diastemas can be repeatedly opened in the composite, with a carbide, to make room for the retraction of these teeth to the desired position.

The width of the centrals is 9 mm which is 0. 5 mm wider than average.2 The length is 11 mm which is 0. 5 mm longer than average. The proportion of width to length (4.25) is excellent but seems wrong because of the distorting3 presence of the 5.2 mm diastema. When the patient smiles, his lower lip covers the incisal surfaces of the maxillary anterior teeth. The Trubyte Tooth Indicator Analysis shows that 11 mm is an acceptable length of incisor for this patient. Maxillary and mandibular midlines do not coincide. The maxillary midline matches the facial midline.

Diagnosis

The patient exhibits a mutilated class 11 occlusion. The maxillary incisors appear aged because they are worn, discolored and maligned. There is an excess of space available along the perimeter of the arch. This is evident in the 5.2 mm diastema between the centrals and the 3.1 mm diastema between the left lateral and cuspid. The total excess space from the mesial of the right cuspid to the mesial of the left cuspid is 11.3 mm (Fig. 2a, b, c). The patient's smile seems unnatural because he is making an automatic effort to cover his maxillary incisors with his lower lip (Fig. 1b, d).

Treatment Plan

Complete orthodontic realignment to upright molars, retract the incisors and reduce the overjet.
Posterior bridgework to replace the missing first molars or the redistributed space.
Indirect porcelain veneers to rejuvenate the maxillary incisors.

The patient adamantly refused orthodontic treatment. He requested to have his "gaps closed now." The suggestion was made to use direct bonding with composite material to treat the diastemas. Should he opt to have orthodontic treatment as was recommended, it would be very simple to periodically open a 1 mm diastema in the composite and allow the mechanics of orthodontics to bring the incisors together. This process of introducing 1 mm diastemas and orthodontic closure of the resultant space would be repeated until the desired positioning of the incisors is achieved. Throughout treatment the diastema would be reduced by 80% of the original size. The patient again refused orthodontics but he liked the idea of using a material that is amenable to change. He agreed it would be prudent to use a composite material on a temporary basis and add to it, or subtract, as his comfort and esthetics would dictate over the next several months. Once we had the result we would be pleased with, we could reproduce it in a superior, more durable material (porcelain laminate veneers). Parameters of cost and treatment time were set up and thoroughly discussed.

Measurements of the diastema indicate that the distal of the centrals must be reduced or we will end up with teeth that are wider than they are long. An intraoral mock up clearly demonstrates this problem to the patient. The solution is readily apparent to him in the diagnostic wax-ups done on study models where the centrals were reduced on the distal by 0.5 mm at the gingiva and increasing to as much as 2.5 mm towards the incisal. The width to length proportion of the centrals; must be pleasing. This is an absolute rule in aesthetic rehabilitation (Fig. 3a, b, c, d).4

Discussion of Treatment

Eight maxillary anterior teeth are anesthetized. Shade selection is accomplished with the patient's active participation. We decided to use shade A3 at the gingival and shade A2 for the body. A more translucent shade is required for the incisal. Braided '"00" plain cord is gently introduced into the labial and interproximal sulcus of the upper incisors. Depth (0.5 mm ) guide striations are placed using LVS-1 Brasseler. A medium grit round end tapered diamond 'erases" the grooves as the preparation is extended toward the interproximal and the facial incisal line angle. The mesial of the centrals is barely instrumented but on the distal an average of 1. 5 mm of tooth structure (0.5 mm at the distal-gingival increasing to 2.5 mm at the distal-incisal) is removed. As a chamfer margin is created, the gingiva is gently deflected (protected) with an 8A plastic instrument. The preparation is extended to the gingival crest. The extension of the preparation into the interproximal is dictated by the visibility of this surface due to the presence of diastemas.

All the involved teeth are prepared simultaneously because optimum access is only available prior to the placement of the resin. The teeth are cleaned using chlorhexidine (Hibiclens) soap and pumice on a cotton pellet. The "'total etch" otherwise known as the 'Kanca technique"5,6 is utilized to prepare the teeth for bonding one at a time. The instrumented enamel surface and any exposed dentin is etched for 15 seconds using 10% Phosphoric acid. Studies have shown a decrease in bond strength of composite to dentine as the exposure time is increased beyond 15 seconds.7 Uninstrumented enamel surfaces would require 15 seconds exposure to 32% phosphoric acid for adequate etch. The acid is then rinsed off thoroughly. Primers are applied and air dried. (All-Bond 2, Bisco, Itasca II.) Next, the unfilled resin adhesive is placed, thinned out with a gentle spray of air and polymerized for 20 seconds.

The diastema is treated using the sandwich technique to avoid "shine through". This can be accomplished by restoring the lingual half of the diastema with a hybrid composite. (T.P.H., Caulk, Milford DE.) This restored lingual surface will now become functional. Occlusal forces dictate the use of a high strength material in this location. Because of these indications, a hybrid composite is used. Measurements with a Boley gauge ensure that the proper width is being created.

Microfil resin (Renamel, Cosmedent, Chicago IL.) shade A3, is applied to the gingival 2-3 mm and polymerized for forty seconds. Renamel A2 is layered onto the body of the incisor and the labial half of the diastema. Vertical grooves are placed with an I.P.C. Carver near the incisal, at 45 degrees to the facial and the composite is polymerized for forty seconds. Renamel incisal medium is now used to fill the grooves and cover the incisal 2 mm The resin is again polymerized for forty seconds. The entire structure is overbuilt to allow for contouring and finishing.

Contouring

Carbide burs (ET, Brasseler, Savanah GA) are used dry to contour the veneers and establish anatomy. Height of contour is kept away from the interproximal to make the centrals seem narrower. The placement of vertical concavities also creates the illusion of a narrower tooth. When the margins are being treated, the gingiva is protected (deflected gently) with an 8A plastic instrument. A surgical blade (#12, Bard-Parker, Franklin Lakes NJ) is used to remove overhangs. Discs (Flexi-Disc, Cosmedent, Chicago IL) are used to reduce and shape the incisal edge and the proximal line angles. The incisal embrasures are refined using these discs. Contours are checked from different perspectives. The emergence profile is evaluated.

Finishing

The proximal, supragingival surfaces are smoothed using metal Compo-Strips (Premier, Norristown, PA) and plastic FlexiStrips (Cosmedent, Chicago IL). In the contact area only the fine-superfine FlexiStrips are used. Smoothing of the labial surfaces is achieved with light pressure using rubber Polishers and Finishers (Ivoclar-Vivadent, Amherst, NY) and Enhance rubber discs (Caulk, Milford, DE). The final polish is accomplished using a Shofu Super-Snap BuffDisk (Shofu, Menlo Park, CA) and Prisma- Gloss (Caulk, Milford, DE). Floss is used to carry the paste interproximally. In order to avoid any interproximal bleeding, the subgingival areas are not finished until the end of the appointment once all the treated teeth are restored.

The entire procedure is now repeated for the left central and subsequently for the laterals, cuspids and bicuspids. Interproximally, the composite is applied directly against the finished veneer. It may adhere but it will not bond to a polished surface. On completion of the second veneer the teeth are separated by placing into the gingival embrasure, from the lingual aspect, an 8A plastic instrument and gently twisting or torquing it. A popping sound is heard when the teeth separate. Now the finishing procedures can be performed on this second restoration. Once all the teeth are restored, the occlusion is checked and refined. The patient is instructed in the care of his bonded restorations and asked to return in one week for fine adjustments and slides.

Fig. 3a The completed smile is pleasing and normal now that the patient is not trying to hide his maxillary teeth with his lower lip.

Fig. 3b The incisal edges follow the smile line by tracing the superior border of the lower lip, this results in lip framing that is attractive to the eye.

Fig. 3c The diastemas have been eliminated utilizing the "sandwich technique."

Fig. 3d The lingual aspects of these spaces have been restored with hybrid composite.

Summary and Conclusion

Aesthetic rehabilitation in complex diastema closure cases is guided by the principles of proportion. The width to length ratio of the centrals must be pleasing. Achievement of this proper balance dictates treatment. It determines the following:

the amount of distal proximal reduction
the decision to completely veneer the incisors vs. just adding to the interproximal
the number of teeth to be treated
the placement and location of naturally occurring prominences and concavities to create the illusion of a narrower tooth.

The proper accommodation of these four topics will permit the maintenance or restoration of acceptable dimensions in the centrals. If they are made to appear harmonious then the principle of the "golden proportion" (1.6:1:0.6) can be achieved among the centrals, laterals and cuspids.

Direct bonding in diastema closure cases allow the dentist and the patient complete control in the formation of that smile. This treatment modality is challenging and ultimately rewarding for the patient and the dentist. At times it enables us to restore form and function and to make our patients whole again not just figuratively but literally.

References

Mayeda D. Journal of the American Academy of Cosmetic Dentistry, Winter 1991 Vol. 6 No. 2
Wheeler R. An Atlas of Tooth Form, W. B. Sauders C., Fourth Edition 1969
Lombardi R. E. The Principles of Visual Perception and Their clinical Application To Denture Esthetics. Journal of Prosthetic Dentistry 1973;29:358
Chiche G. Pinault A., Smile Rejuvenation: A Methodic Approach. Practical Periodontics and Aesthetic Dentistry. Vol. 5 No 3: April 1993; 37-43
Kanca J. Bonding To Tooth Structure! A Rational Rationale for a Clinical Protocol. Joumal of Esthetic Dentistry 1989: 1: 135-138
Kanca J. Dental Adhesion and The All Bond System. Journal of Esthetic Dentistry August 1991:129-132
Suh B. Cincione F., All Bond II: The Fourth Generation Bonding System. Esthetic Dentistry Update Vol. 3 No.3: June 1992: 61-66

Sources Consulted

Miller M., Diastema Closure. Reality 1996: Vol 10, Section 2:385- 387
Miller M., Direct Resin Veneers. Reality 1996: Vol 10, Section 2: 393-395
Mopper W., O'Malley M., Renamel Restorative System. The Illustrated Technique Guide. 1986 revised 1992.

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