REPAIR IN ZIRCONIA CROWNS

[drmithila]

 

Despite the best intentions to fabricate and deliver durable metal-free res­torations, from time to time patients may present requiring repairs to such dental work. When this occurs, a solution must be considered that will not only function properly, but also satisfy patient needs as well. Testing a dentist’s and technician’s knowledge and skill set, such cases may require unconventional methods and material selections to achieve optimal results.

That said, it is important to remember that when selecting restorative materials, it is essential to choose the proper material for the indication at hand to prevent postoperative complications.
Although many of the restorative materials used in dental laboratories and dental offices today are much stronger than those used in the past, there may still be a propensity among certain products to develop complications. When teeth have been restored with veneers, partial dentures, or full dentures, it is important to communicate to the patient the proper methods of caring for their restorations. Even then, fractures and chips may be unavoidable.

Before Image. View of the prepared porcelain pontic. (Note: The preparation was left in existing porcelain and not taken to the depth of the zirconium oxide substructure in order to have a stronger porcelain-porcelain bond.)	After Image. Close-up view of the repaired restoration after cementation.
Figure 1. Hydrofluoric (HF) acid (9% HF [Ultradent Products]) was applied to the No. 9 pontic.	Figure 2. The HF was rinsed thoroughly with copious amounts of water.
Figure 3. Monobond Plus (Ivoclar Vivadent) was then applied to the internal aspect of the restoration.	Figure 4. The porcelain at the pontic site also was treated with Monobond Plus.

ZIRCONIA-BASED RESTORATIONS 
Of the many materials used today, zirconia-based ceramics have been widely used in the fabrication of crowns and dental prostheses.1 Although approved for indications such as single crowns, fixed partial dentures, and implant abutments; chipping and fractures are seen as major problems and clinical setbacks when using this material.1 This is a direct result of the different pressures at which the porcelain and zirconia are prepared before being placed together.¹ As a result, there is a greater chance of separation and, consequently, chipping and fractures of the porcelain that overlays the underlying zirconia substructure.¹
Researchers and dental laboratory technicians are still conducting studies to determine the best way to fabricate zirconia-based restorations, since the incidence of chipping and fracture is believed to originate in the fabrication and design processes, not the material itself.² Given the challenges presented by zirconia restorations, dentists and technicians have sought alternative methods to correct the intraoral cracks and fractures that occur in order to preserve the structures that are still intact.2 These methods save patients chair and recovery time, as well as cost.²

LITHIUM DISILICATE
Lithium disilicate, another recently introduced all-ceramic material for restorations, has been gaining in popularity for several reasons.^3,4 The controlled size, shape, and density of this material’s crystalline structure contributes to a ceramic that demonstrates greater strength and durability.^3,5 Lithium disilicate can be used to fabricate a very strong and durable monolithic restoration.6 These single-material restorations are more resistant to chipping and fracture, since there are no layering porcelains present to separate.^7,8 The material’s relatively low refractive index produces optical properties, such as translucency, that produce excellent aesthetics.^3,8 Materials like lithium disilicate eliminate the chipping and fracture problems that have plagued patients in the past, even though zirconia-based restorations are still considered aesthetic and effective.

 

        

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