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Durable Cementation of Lithium- Disilicate Crowns and Veneers

24 Mar 2021
Lithium-disilicate has long been a reliable standard for indirect restorations, with its superb dimensional stability and precision finishing. In particular with the advancement of minimally invasive restorations and no-preparation  veneers, Lithium-discilicate opens up great possibilities, but the cementation technique and material becomes even more critical for the final outcomes. The evolution of cements and cementation techniques can therefore be a key parametre in minimally invasive restorations. Further to the cement mechanical properties and influence in the aesthetics, the addition of bio-interactive or regenerative qualities can significantly increase the options for the clinician. Read about a calcium silicate–based dual-cure resin cement with calcium and fluoride release capabilities in the case report by Dr. Jack D. Griffin!

Abstract: Clinicians have many restorative options from which to choose. For indirect restorations, the selection of cementation technique is critical to a successful outcome. One emerging trend in dentistry today is the development of materials that have bio-interactive or regenerative qualities. This case presentation reports on the use of a calcium silicate–based dual-cure resin cement that has shown to be effective for use with full-coverage lithium-disilicate restorations due to not only its excellent clinical characteristics but also calcium and fluoride release capabilities. The case also includes conservative lithium-disilicate veneer restorations.

Many viable material choices are available in restorative dentistry today. Despite the ever-growing arsenal of newer materials and techniques, clinicians are often reluctant to change from using those materials and methods with which they are most familiar and have had success. Above all else, clinicians want predictable, repeatable results. Restorative dental materials have advanced to meet the increasingly bio-friendly and metal-free esthetic demands of the public today. Contemporary materials are expected to have, not a negative, but a positive effect on living tissues. An aversion to metal, the avoidance of potential allergies, and the systemic effect of dental materials all drive the dental profession to be more biologically tolerant.

Versatile Predictability
When working with indirect restorative materials, clinicians require consistency in esthetics, functionality, durability, and patient comfort. Zirconia and lithium disilicate have become dominant materials in modern metal-free dentistry. They are commonly used for restorations ranging from conservatively prepared veneers to full-coverage crowns to full-arch prostheses. Factors such as occlusion, parafunctional habits, esthetics, and biological effects influence a clinician’s choice of indirect materials. The success of lithium disilicate, specifically IPS e.max® (Ivoclar Vivadent, ivoclarvivadent.com), has been well documented, and it has become one of the most versatile esthetic materials in dentistry. The dental profession has had more than 15 years of clinical performance and numerous studies to fairly evaluate this material, its clinical properties, and durability. Success has been observed in both full-coverage and conservative restorations as well as in anterior and posterior situations. High translucency imparts vitality to a restoration and is important to its esthetic success.9 The esthetic predictability of lithium disilicate, particularly when used in conservative anterior preparations, makes it a popular cosmetic material choice. Lithium disilicate is available in several different levels of opacities. The opacity should be chosen on a case-by-case basis depending on preparation shade, thickness of the restoration, and desired final shade.

Modern Cementation
Cementation technique is critical to restoration success, and clinicians have many materials and methods from which to choose: cement or bond, light cure or chemical cure, acid-etch or no etch, bonding agent or self-adhesive, silane or sandblasting, etc. Retention is but one of many factors influencing cement choice. Other factors include long-term physical properties, color predictability, ease of clean-up, and the luting material’s compatibility with the restoration material. Self-adhesive resin cements work well with retentive preparations, but light-cure resin cements with separate steps for phosphoric acid-etching and adhesion provide better long-term results with preparations that have less-than-ideal retention.
Light-cure-only resin cements are often used with conservative anterior restorations because of their longer working time, predictable clean-up, excellent esthetics and color stability, and high strength. Transparent light-cure resins have been demonstrated to yield superior color stability when compared to luting materials with more color or that are dual cure. Full-coverage restorations allow for greater diversity in cementation choices. Self-adhesive dual-cure resin cements are popular with full-coverage restorations because of their simplicity and predictable results. They provide a moderate bond to dentin and good esthetics. A newer emphasis has been placed on cements that are bio-interactive or regenerative in nature. Bioavailable ions generate an alkaline pH environment, neutralize acid, and ultimately promote healing, which may result in a less sensitive, longer-lasting restoration. The cement responds to the oral environment to provide therapeutic ions. Calcium silicate–based dual-cure resin cements have shown to be an effective choice for full-coverage lithium disilicate because of excellent clinical characteristics along with calcium and fluoride release. The following case report demonstrates the use of an ionreleasing self-etch, self-adhesive calcium-silicate resin cement with layered lithium-disilicate crowns and a translucent lightcure resin cement for placement of lithiumdisilicate veneers.

Crown and Veneer Case
A 61-year-old patient presented with her tooth No. 9 crown loose, and she could actually remove it (Figure 1). Many years earlier the patient had had endodontic surgery, an apicoectomy and retrograde filling to repair a failing silverpoint obturation, and was now symptom free. The silver point remained in the tooth and showed no lesions on radiograph. Tooth No. 8 had an unbonded porcelain veneer that had come off “several times” before. She wanted to replace the restorations on the central incisors with ones that would be a “lighter color” and to bleach her other teeth (Figure 2). A full series of photographs was taken and reviewed with the patient. Occasionally, in the author’s experience, patients might want to choose a “lighter color” for their restorations and attempt to bleach their other teeth until they match. After some discussion and patient education, the patient accepted a plan calling for lithium-disilicate porcelain restorations on teeth Nos. 5 through 12, which included full coverage on the central incisors and conservative veneer preparations on the other teeth. A full-coverage restoration for tooth No. 8 was chosen because the existing preparation was primarily in dentin, there was a history of veneer failure, and doing so would provide the laboratory with symmetrical consistency in restoration thickness. Another full series of photographs was taken, a mock-up was done, and a temporary impression matrix was made. The patient chose a final VITA 3D shade of .5M1 (VITA, vitanorthamerica.com). Preparations were done using a course diamond (NeoDiamond®, Microcopy, microcopydental.com), with 1.5 mm occlusal clearance and chamfer margins. On teeth Nos. 5 through 7 and 10 through 12, 0.5 mm veneer preparations were executed with a finishing diamond, staying in enamel in all places except abfraction areas at the gingival margins. Preparation corners were rounded to reduce internal stresses on the restorations.