Predictable Porcelain Repair With Composite Resin

Mitch Conditt, DDS

Learning Objectives:  

As a result of reviewing this case study, the reader should:

• Understand the role of composites in porcelain veneer repair and aesthetics
• Be able to visualize the process of repairing porcelain veneers using different types of composite resins 

Most dentists now provide their patients with the options of porcelain veneers or porcelain crowns to improve the appearance of their smiles. Many journals have published the importance, both professionally and personally, of an attractive smile. Yet barely half of these patients are satisfied with the appearance of their own smile . With the more aesthetically conscience baby boomer population coming into their prime, dentists are experiencing their demand to look and feel younger. Fortunately, we now have tools and techniques available to respond and, in many cases, change the lives of these individuals. Porcelain veneers have been successfully placed for over two decades. With the continuous improvement of bonding agents and composite resin cements, the success of these restorations continues to rise. Along with these material innovations and what seems to be a growing awareness of occlusion, the occurrence of chips and fractures in these porcelain restorations has been minimized . Nevertheless, there will always be the occasional need to repair a porcelain restoration, if only from trauma.

Case Presentation 

The following case shows a severe traumatic fracture to a 10-year-old porcelain veneer on a 45-year-old female. Radiographs revealed no pulpal injury from the trauma. While several veneers had fractures within the porcelain, tooth #9 was an immediate concern (Figure 1). This veneer and others will require replacement, but the patient opted for long term repair only at this time. Fortunately, with current porcelain repair techniques, dentin bonding agents, and contemporary composite formulations, this task can be predictable, long-term, and aesthetic.

Any large direct anterior composite restoration has to begin with proper shade assessment and color mapping. In this case, the adjacent veneer was used as a guide (Figure 2). An alginate impression of the fracture was taken, a stone model was fabricated, and replacement of the fracture with a composite mock-up was performed. A silicone matrix would later be fabricated from this mock-up and used to accurately reproduce the palatal anatomy and incisal edge for the first initial layer of composite. A matrix of this type was not mandatory and this palatal increment could have been placed freehand, but it was much easier for the author to build the anatomy on a composite mock up in the laboratory than directly in the patient’s mouth. This silicone matrix also substituted for matrices placed interproximally to help form the lingual embrasures (Figures 3-4-5).

Porcelain Treatment 

The variations in the techniques begins with how one roughens the porcelain. Some clinicians suggest sandblasting the porcelain with aluminum oxide; others recommend roughening with a diamond. Still others suggest that roughening of the porcelain is altogether unnecessary. Treating the porcelain with hydrofluoric acid of different percentages often constitutes the next step. Although still widely used, some kits have concluded that this step also is unnecessary. Silane (though its name varies from kit to kit), however, seems to remain essential in all the techniques.

For this patient, the porcelain was roughened with a course diamond. A scalloped bevel extending approximately 4 mm in length was placed with this same diamond. The larger bevel provided a greater surface area for the composite, which helped increase fracture resistance. The scalloping also concealed the junction of the composite and porcelain materials (Figure 6). The lingual was also beveled, but to a lesser degree than required on the facial aspect. In this case, there was remaining enamel and dentin exposed after the fracture. To prevent hydrofluoric acid or silane from contacting the tooth structure, a thin layer of composite was placed for additional protection. Clear matrices placed interproximally prohibited the contact of etchant or bonding agent with the adjacent teeth. These were removed once the boding agent was cured (Figure 7).

Total-Etch Technique 

After roughening the porcelain with a course diamond, the tooth surface was cleansed with 2% chlorohexidine gluconate for 20 seconds. Phosphoric acid 35% was placed on the enamel for 15 seconds and dentin for 12 seconds, rinsed thoroughly, and blotted dry. An etchant with an antibacterial included could have also been used for the cleansing and etching steps simultaneously. Next, the tooth was remoistened with a rewetting agent) for 20 seconds and blotted. A bonding agent was placed on the tooth in multiple coats for 20 seconds and dried with light air for 5 to 10 seconds to evaporate the acetone and leaving a shiny appearance on the dentin. This was then cured with a halogen light for 10 seconds.

Composite Placement 

A contemporary composite resin was chosen for the repair, use of this material would eliminate the need to use both a microfill and a hybrid resin. In this particular case, a micro-matrix composite resin was chosen for the repair. Due to its strength and polishability, the need for the sandwich technique of surrounding the stronger hybrid with the more aesthetic microfil was eliminated . The custom shade guide for this material greatly aided with the operator’s selection and application of the opaque, body and incisal shades. Each individual shade tab listed the opaque, body, and incisal shades that were required to achieve a proper shade match with the patient’s veneers. In this case, the desired shade (A1) required the use of an A2 opaque shade, A1, and the clear enamel shade. The opaque shade was selected to conceal and protect the tooth structure from the hydrofluoric acid and silane. This also helped to mask any possible show-through of the darker tooth structure.

Clear matrix strips were used to protect the adjacent teeth from etchant and bonding agents. They were not necessary after this process, because the silicone putty matrix would be used to form the lingual embrasures. Once the dentin was protected, the porcelain was prepared. Hydrofluoric acid (9.5%) was placed on the roughened and beveled porcelain for 60 seconds, rinsed thoroughly, and dried. Silane was then applied to the porcelain for 5 seconds and air dried. The bonding agent was applied over the porcelain and composite, thinned with air, and cured for 10 seconds. If there were any exposed tooth structures present, they too would have been included in the bonding procedure.

The next resin applied was a very thin layer (0.5 mm) of the translucent shade. If this layer is placed too thick it can give a grayish appearance or a decrease in value. The silicone matrix was used to adapt the composite for proper lingual anatomy and the initial contour of the lingual embrasures (Figure 8). Most of the body of the tooth, including the mammelons, was created with the A2 shade. This body shade was brought to full thickness on the facial aspect--except for between the mammelons and along the interproximals areas (Figure 9). These areas will be brought to full contour with an incisal shade for translucency. Placing an incisal shade over the middle and gingival third of the restoration would be unnecessary.

The mammelon characteristics were created to mimic the optical effects present on the adjacent tooth. Tooth #8, a porcelain veneer, was designed with three very distinct mammelons. After polymerizing the composite, the operator noticed the middle mammelon was too long incisally, so it was recontoured with a finishing bur to its correct dimensions (Figure 10). The bonding agent was once again painted over the surface of the composite after the oxygen inhibited layer had been removed with the finishing bur. This step allowed the following layer of composite to bond properly (Figure 11). Another layer of A1 was placed to complete the middle third to full facial contour (Figure 12). The white halo at the incisal edge of the patient’s teeth was reproduced with a very thin line of white tint, which was painted on the edge of the CE lingual layer (Figure 13). Lastly, the interproximal regions and the areas between the mammelons were filled with a final layer of microhybrid resin  to again mimic the facial incisal translucency of porcelain (Figure 14).

Finishing and Polishing 

Initial contouring was accomplished with finishing discs. Discs and points were used to polish the lingual anatomy, which was minimal due to the successful application of the silicone matrix. The discs and points ere also used to contour and finish the facial and incisal surfaces. Final polishing with a polishing disc rendered an aesthetic luster for the small-particle resin restoration.

Conclusion 

The aesthetic capabilities (eg, color matching, polishability) of this composite will allow the patient to show her smile with confidence. From the clinician’s perspective, the bond strength of the adhesive agent allowed the delivery of a predictable, conservative repair for the damaged porcelain restoration. As the physical and optical qualities of contemporary composite resins continue to increase, their utility for direct restorations will undoubtedly follow.

*Private practice, Fort Worth, TX.

Related Reading: 

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