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Minimally Invasive Restorative Dentistry

A Biomimetic Approach

It is widely accepted that prevention is the most conservative, least costly method of maintaining a patient’s teeth over the long term.1,2 Prevention has been the cornerstone of modern dentistry, but even with the encouragement and education provided by a trained staff, clinicians will encounter some patients who present with compliance issues. Many times, compliance with home care—especially during orthodontic treatment—is neglected, requiring invasive restorative procedures.

The severity of the resulting damage can often be seen in the form of extrinsic stains (ie, white spot surface lesions) as well as cavitated carious lesions.3 These lesions, which are caused by the accumulation of plaque and bacteria,4,5 can be addressed through treatments of varying invasiveness. Depending on the severity of the lesion and its etiology, therapy may consist of prophylaxis, air abrasion, tooth whitening, resin bonding, prosthetic restoration, or some combination thereof.

Minimally invasive treatments are procedures that restore form, function, and aesthetics with minimal removal of sound tooth structure.6-8 As a person ages, so do their restorations. Eventually, previously restored teeth will deteriorate and require replacement restorations.9,10 Fortunately, restorative materials and procedures are constantly evolving. If an initial restoration is created using minimally invasive procedures, sound tooth structure will often be available for a subsequent restoration.

 

Case Presentation

Following orthodontic treatment, a 15-year-old female presented for evaluation and treatment of numerous demineralized lesions (Figure 1). The patient’s chief complaint was the unaesthetic appearance created by the lesions around and beneath previously worn orthodontic brackets. After a thorough clinical examination and radiographs, a treatment plan was formed. Using a minimally invasive approach, the clinician prescribed the use of a remineralizing toothpaste to repair the demineralized enamel.11 Should this manner of treatment prove insufficient to produce the required outcome, additional minimally invasive procedures would be undertaken.

 

The Initial Hygiene Protocol

During a subsequent hygiene visit, the patient was again instructed on the use of a toothbrush and dental floss. As part of the hygiene regimen, the patient also received instruction on the application of a remineralizing toothpaste, which would provide active calcium and phosphate to repair the damage of the demineralization and prevent the need for future restorations. Follow-up appointments revealed that many of these demineralized areas were adjacent to tissues that did not respond well to the patient’s home care regimen.

Consequently, the decision was made to restore the porous decalcified tooth structure and create a smoother tooth surface that would simplify cleaning and reduce plaque retention. The tissues were weeping sulcular fluid and a number of lesions had cavitated beyond the possibility of remineralization. The author opted to place minimally invasive restorations in the cavitated lesions of teeth #6 through #11 and #27 (Figure 2).

Minimally Invasive Restorative Care

Air abrasion was selected for its minimally invasive properties utilized to selectively remove the carious lesions and demineralized enamel and to establish a substrate that would be conducive to subsequent adhesive bonding procedures.6,12,13 Tissues were retracted where the lesion extended subgingivally. The method used consisted of a simultaneous spray of aluminous oxide air abrasion particles and copious amounts of water, which created a parallel water stream with the air abrasion particles. This technique minimizes aspiration as the moist air abrasion particles are suctioned up in the HVE and enhances the effectiveness of the particle stream when removing softened tooth structure. The air abrasion particles should be angled at the tooth and away from the gingiva, thus minimizing both trauma and embedding aluminous oxide into the tissues. To be sure that all caries were removed, a sharp explorer and an extremely sharp titanium nitride-coated microspoon excavator were used. The tactile approach taught at most dental schools today was utilized. As observed in the final preparations (Figures 3-4-5), the design did not follow any conventional forms.

Isolation of the lesions was crucial to a successful bonding process. Much of the demineralized areas were adjacent to unhealthy gingival tissues at the time of preparation. Applying a rubber dam, therefore, would have been more cumbersome than performing single-tooth isolation using a contoured Mylar matrix strip. The contour strips are three-dimensionally shaped to encircle the tooth, thereby completely isolating the work area. They are then flared at the gingival with the cone end of a cone-socketed hand instrument. This technique not only creates a cervical seal but also helps establish an optimal emergence profile. This procedure was more efficient than using a #212 clamp placed on the tooth being restored as it causes much more tissue trauma. The contour strip, meanwhile, completely isolates the work area as it created the emergence profile, which generally cannot be detected with an explorer postoperatively. The resulting composite is polymerized against a Mylar strip and does not require finishing if matrixed appropriately. Essentially, a curve is created at the gingiva during the shaping of the contour strip, virtually recreating and mimicking the placement of the original CEJ for proper hold and protection of the tissues.

(Continued from page 1 )

 

The subgingival placement of the restoration margins and the selective contouring of the strip created a surface that would support long-term gingival health (Figure 6). The portion of the gingival composite built up against the Mylar strip provided an extremely smooth surface without any oxygen-inhibited layer, rendering polishing unnecessary. The contoured Mylar strips were trimmed, placed around the facial and proximal surfaces of the tooth, and sealed in place with an unfilled resin also placed on the gingival surface of the strips for stabilization (Figure 7).

Upon placement of the matrix form, a 37% phosphoric acid etchant was placed on the prepared lesion for 15 seconds,13 rinsed for 20 seconds, and lightly air dried. The etch was placed on the enamel first and then spread onto the dentin to greatly reduce exposure time. The bonding agent should be left on for 30 seconds to ensure an adequate hybrid zone. This allows the proper penetration of the resin to occur. With the area matrixed in correlation to the final margins, the prepared and etched tooth structure was coated with a bonding agent. Thoroughly wetting the dentin allowed the composite resin to penetrate into the tooth, remove any excess intertubular fluids, and create the hybridized zone. After thinning the bonding agent with a steady stream of dry air, the entire bonded surface was light cured for 30 seconds. The appropriate dentin-shaded resin was placed into the deep dentin portions of the preparations and polymerized. The final layer of enamel-shaded composite resin was placed to create the full contour and the surface translucency of the restoration. The entire process was conducted on each tooth involved. Bands were placed simultaneously on each independent tooth and then removed simultaneously.

After the composite resin had been brought to full contour and was thoroughly polymerized, the matrix was removed, and the final shaping, surface texturing, and polishing were completed, ensuring that the teeth would match the unprepared tooth (Figure 8). Due to the inherent polishability of the microhybrid composite selected, these restorations were shaped and polished using primarily two burs. A 30-fluted flame-shaped bur was used to create the contours and textures; the final polish was rendered with a fine-polishing rubber point. The surface luster was buffed to the prerestored luster of the patient’s buccal tooth structure.

 

Follow-up and Maintenance

As observed in one- and two-week follow-up visits, there was an excellent gingival response to the polished restorations (Figures 9-10-11-12). With conscientious home care, these minimally invasive restorations should provide years of enjoyment for the patient. If the patient decided at a later date to pursue additional aesthetic enhancement, porcelain laminate veneers can be considered once the gingival tissues have matured and home care remains consistent.

Discussion

Air abrasion is an effective process that can remove demineralized enamel and the underlying carious dentin.14,15 In the author’s experience, air abrasion also creates an ideal surface for achieving excellent bond strengths to both dentin and enamel.12,13 Frequently, teeth can be prepared, as described in the aforementioned adhesive bonding procedure, via air abrasion without the need for anesthesia, especially when used with the water spray. The simultaneous delivery of the aluminous oxide and warm water keeps the scatter of aluminous oxide powder to a minimum.

The microhybrid composite resin was selected for replacing the missing tooth structure because of its ability to match the shade and translucency of the adjacent tooth structures. The physical properties (eg, fracture toughness, flexure modulus, wear resistance) and polishability of the microhybrid resins also make them suitable treatment options for the use of such indications as previously described.16,17

Conclusion

Preventive dental maintenance is the most cost-effective means of preserving dentition. Neglect can lead to a variety of problems, ranging from white spot surface lesions to fully engulfed carious lesions. Minimally invasive treatment should follow only dedicated preventive maintenance. The patient in this case underwent a minimally invasive procedure that preserved sound tooth structure. This preservation lends itself to better future treatment options as dental technology advances.

 

Private practice, St. Paul, MN.

 

References

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  2. Widstrom E. Prevention and dental health services. Oral Health Prev Dent 2004;2(Suppl1):255-258.
  3. Greenwell L. Bleaching techniques in restorative dentistry: An Illustrated Guide. London, UK: Martin Dunitz, 2001:1-23.
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  11. Additional aids to the remineralization of tooth structure. In: Reynolds EC, Walsh LJ. Preservation and Restoration of Teeth. 2nd ed. 2005, p111-118.
  12. Manhart J, Mehl A, Schroeter R, et al. Bond strength of composite to dentin treated by air abrasion. Oper Dent 1999;24(4):223-232.
  13. Berry EA 3rd, Ward M. Bond strength of resin composite to air-abraded enamel. Quintessence Int 1995;26(8):559-562.
  14. Rosenberg SP. Air abrasion in the aesthetic restorative practice. Pract Periodontics Aesthet Dent 1999;11(7):843-844.
  15. Bryant CL. The role of air abrasion in preventing and treating early pit and fissure caries. J Can Dent Assoc 1999;65(10);566-569.
  16. Okuda WH. Achieving optimal aesthetics for direct and indirect restorations with microhybrid composite resins. Pract Proced Aesthet Dent 2005;17(3):177-184.
  17. Mitra SB, Wu D, Holmes BN. An application of nanotechnology in advanced dental materials. J Am Dent Assoc 2003;134(10):1382-1390.
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