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Achieving Excellent Indirect Restorations
Indirect restorative materials have changed dramatically in recent years. We have seen the advent of CAD/CAM dentistry and digital impressioning, along with the introduction of a number of new all-ceramic options such as zirconia and lithium disilicate. In a recent article we published in Inside Dentistry, we discussed the death of porcelain-fused-to-metal (PFM) crowns. We have seen a dramatic drop in the use of PFMs and gold as restorative materials. There are a number reasons why this is happening. One is the improved esthetics with these all-ceramic materials. Another issue is related to the high cost of gold.
Today’s all-ceramic materials have excellent translucency and strength. As esthetics have improved, we are now able to use many of these materials as monolithic all-ceramics. By avoiding the layering of porcelain on some of these materials, we have decreased the likelihood of fractures. In addition, zirconia has demonstrated improved physical properties, which was allowed us to use it reliably in the posterior region. Although lithium disilicate tends to be favored in the anterior because of its improved esthetics, the evidence is that it is appropriate in the posterior as well.
With all of these new options, there is often confusion regarding cementation. We have many cement choices today, from self-adhesive cements and composite cements to glass ionomers and now bioactive cements. The resin cement category evolved out of the total-etch and dentin adhesive technologies. For proper use, they require pretreatment of the tooth surface with 37% phosphoric acid and application of a dentin bonding agent prior to application of the resin cement. These cements form a micromechanical bond to both tooth structure. They are relatively insoluble in oral fluids. We also have resin cements that are the self-etching and require no pretreatment of the tooth surface.
Even though our materials have improved, we still must rely on good impression-taking skills to ensure the best possible clinical outcomes when it comes to indirect restorations. Impression taking may be done digitally or with conventional impression materials, but either way we need to be able to see the margin to produce a restoration that fits. This requires that we choose the right system or material as well as understand tissue management and good preparation design.
At the end of the day, we measure success by a happy and healthy patient. The steps we need to take when doing indirect restorative dentistry are many. Any misstep we make can result in an unhappy patient and therefore a failed case. Doing dentistry well isn’t easy. I have a saying I use with dental students: There are two ways to do dentistry—the easy way and the right way. The easy way is never the right way.
About the Author
Gerard Kugel, DMD, MS, PhD
Dean for Research
Department of Prosthodontics and Operative Dentistry
Tufts University of Dental Medicine