Restoration of Form and Function for Failing Disto-Occlusal Amalgam Fillings

Irfan Ahmad, BDS

Case Presentation

A 42-year-old female patient presented for treatment of the posterior maxilla. Clinical examination of the site revealed a failing disto-occlusal amalgam restoration in tooth #12(24) and a temporary mesiodistal-occlusal dressing in tooth #13(25) (Figure 1). Upon completion of diagnostic evaluation, the clinician determined that the existing restorations required replacement. The optimal treatment modality had to address each of these factors while satisfying the aesthetic expectations of the patient. A decision had to be made as to how to treat the affected dentition and restore optimal bioaesthetics.

The Solution

Due to the current controversy about fillings containing mercury and the ever-increasing desire of patients to have more cosmetic fillings, the use of amalgam is being questioned. In accordance with the aesthetic requirements of the patient, it was determined to replace the amalgam with microhybrid composite resins (ceramic optimized polymers or Ceromers) with a high filler content (80% by weight), which would provide a suitable alternative to more invasive or expensive procedures. The inorganic ceramic filler would provide enhanced physical properties, while the glass particle content would improve the aesthetics (ie, fluorescence and radiopacity) of the restoration. Once the patient consented to the treatment, the procedure was initiated.

Occlusal contacts were obtained with articulation paper; these marks determined the peripheral limits of the filling and ascertained the jaw movements in various excursions. The treatment site was isolated with a rubber dam, and the existing restorations were removed under a controlled environment of high-speed suction to aspirate the aerosol formed during the drilling procedure. The rubber dam ensured that the amalgam spray, created by the bur of the turbine handpiece, did not contact the soft tissues of the oral environment, where it could have become embedded and formed an amalgam tattoo. Once microhybrid composite resin had been placed in the maxillary second premolar (Figure 2), treatment was initiated at the first premolar site. Following the removal of the amalgam restoration in tooth #12(24), a wooden wedge was placed distally to accommodate a matrix band and establish a tight contact point (Figure 3).

Cavity design was determined by the extent of decay and discoloration of the tooth and completed accordingly. Once cleansing with 0.2% chlorhexidine gluconate was completed,¹ the cavity was etched with 37% phosphoric acid for 20 seconds and thoroughly rinsed. A generic bonding agent was applied to moisten the dentin and enamel (Figure 4), and the stainless steel matrix band was placed around the tooth.

Utilizing a flat plastic instrument, increments of hybrid composite resin were placed in a hollow 'V' shape of 1-mm to 1.5-mm depth. Each arm of the restoration was placed and cured separately on the buccal and lingual axial walls. Where the cavity extended to a greater depth, an opaque dentin shade of the composite resin was utilized to mask pulpal floor discoloration and gain a deeper chroma in the color (Figure 5). Successive layers were subsequently built up using translucent enamel shades. When the penultimate layer was completed, a reamer that had been dipped into a light-cured stain was used to shape fissure stains into the malleable composite material (Figure 6). The final layer was then placed to complete the stratification and to cover the stained fissure patterns, using the existing occlusal morphology landmarks as a reference. Cuspal inclines were also accomplished at this stage.

The rubber dam was removed to facilitate examination of anatomy and occlusal contacts. Finishing tips and polishing pastes were utilized to finalize cusps, inclines, and fissure patterns. The filling margins were etched for 20 seconds (Figure 7) and rinsed until the enamel displayed a frosted appearance. The etched enamel margins were brushed with a surface sealing resin and cured for 20 seconds to seal any microcracks that might have resulted from the finishing and polishing procedures (Figure 8).² The definitive restorations exhibited correct anatomical form and aesthetics that were indistinguishable from the natural dentition (Figure 9).

Conclusion

The objective for bioaesthetic, direct posterior restorations is not merely treatment of disease to alleviate the symptoms of the patient, but to restore form and achieve optimal function. In order to fabricate bioaesthetic restorations, the clinician must address topography, stratification, optical characteristics, and strength. Once the clinician has mastered these elements and the proper clinical protocol, it is possible to provide bioaesthetic restorations with correct form that will serve the recipient with improved function and longevity.

* Private practice, London, England

References
1. Gwinnett AJ. Effect of cavity disinfection on bond strength to dentin. J Esthet Dent 1992;4(suppl):11-13.
2. Crispin BJ. Contemporary Esthetic Dentistry: Practice Fundamentals. Quintessence Publishing. Carol Stream, IL: 1994.