Optimal Results with Lithium Disilicate Veneer Cement
Dedicated new resin cement provides strong bonding
Porcelain veneers have been in use in dentistry since the mid-1980s. Originally, veneers were primarily fabricated from feldspathic porcelain, were not strong (flexural strength of approximately 80 MPa), and were mostly bonded to enamel only. Almost 30 years later, stronger, more durable materials are available, such as the IPS e.max® system (Ivoclar Vivadent Inc., www.ivoclarvivadent.us), which uses monolithic lithium disilicate with a flexural strength in the range of 360 to 400 MPa.1 The cements used to bond these glass ceramics have also greatly improved, featuring stronger bonds to both enamel and dentin.
BISCO, Inc. recently introduced a new resin cement, eCEMENT™ (www.bisco.com), that was specifically created to be used with products made of monolithic lithium disilicate; its high bond strengths allow for adherence of glass ceramic to the natural tooth as well as high-quality functioning in the oral environment. The dentist can choose the cement’s light-cure (eCEMENT Light-Cured) or dual-cure (eCEMENT Dual-Cured) formulation, depending on the glass ceramic thickness.
Case Presentation
The patient presented seeking to replace existing porcelain veneers placed 10 years ago. She disliked the color and shape of her veneers and desired a whiter, more esthetic smile (Figure 1). Evaluation of her occlusion did not reveal any abnormalities and her temporomandibular joints were asymptomatic, with no signs of occlusal instability. Therefore, no occlusal therapy was necessary before treatment was inititated.2 Impressions were taken and the models were mounted on a Panadent articulator (Panadent, www.panadent.com) using a Kois Dento-Facial Analyzer (Panadent).3
After discussing the treatment plan with the patient, it was determined that eight new porcelain veneers would be placed, six of which would replace existing veneers on teeth No. 6 through No. 11. It is often difficult to achieve a natural-looking smile with the placement of just six veneers. Placing additional veneers beyond the corner of the mouth, past the canines onto the premolars, can help to fill out the buccal corridor for a fuller, more pleasing smile.4 After the proper incisal edge position was communicated on mounted models, the case was sent to the dental laboratory. A diagnostic wax-up and a putty matrix were created and returned to the office.
The patient returned to the office a few weeks later for evaluation of the wax-up, try-in of the putty matrix, and to provide final approval of the provisional veneers before treatment initiation, as is recommended.5 During the teeth preparation and impression appointment, the existing veneers were removed from teeth No. 6 through No. 11. A diamond bur was used to carefully remove the porcelain to preserve as much remaining tooth structure as possible. A #1 retraction cord soaked in aluminum chloride was placed in the gingival sulcus. The teeth were prepared, leaving as much enamel in place as possible.6 Teeth No. 5 and No. 12 were also prepared for veneer placement.
Before the final impression was taken, a bis-GMA–based temporary material was used in the putty matrix and placed on the teeth to evaluate proper facial and incisal reduction. A #0 retraction cord was placed in the sulcus of teeth No. 5 through No. 12, left in place for approximately 3 to 4 minutes, and then removed. A polyvinyl siloxane impression was taken, along with a maximum intercuspal position bite and opposing impression. The provisional veneers were fabricated with the bis-GMA–based resin, trimmed, and polished. They were seated with ClearTemp™ LC (Ultradent Products, Inc., www.ultradent.com), light-cured after the removal of excess cement, and then adjusted for proper esthetics and function. A new impression of the provisional veneers and the patient’s facebow measurement were sent to the laboratory for evaluation. The patient returned to the office 3 days later for her final evaluation and no further adjustments were necessary.
A few weeks later, the patient returned for the final placement of the new ceramic veneers. After anesthetizing the patient, the provisional veneers were removed using a scaler (Figure 2). All temporary cement was removed; a #0 retraction cord soaked in aluminum chloride was placed in the gingival sulcus. The decision was made to use eCEMENT Light-Cured resin cement. This was chosen because of its excellent bond strength to cut enamel, simple color choices, and the viscosity of the cement, which makes for easy clean-up. The veneers were fabricated using the IPS e.max system.
The existing tooth structure had tetracycline staining evident at the time of preparation. Decisions were made regarding proper depth and thickness of the final veneers during the preparation appointment. A deeper preparation would appear darker, as tetracycline would be more pronounced in the dentin. Not only would this have been an overly aggressive preparation, but also it would have meant less enamel for adhesion, resulting in the need for full-coverage porcelain for proper retention. The decision was made to use a more conservative preparation for enamel bonding, necessitating the use of a more opacious lithium disilicate core with layered porcelain to effectively cover the underlying tooth color.7
After placement, the veneers were evaluated and verified for color, contour, and fit. Next, eCEMENT Light-Cured Translucent shade was tried-in on tooth No. 8 and shade A1 was tried-in on tooth No. 9. The Translucent shade was preferred and selected (Figure 3). The teeth were cleaned with PrepStart (Danville, www.danvillematerials.com) using 27 mm aluminum oxide powder for increased final bond strength. The veneers were treated with Porcelain Etchant (4% HF) (BISCO, Inc.), followed by silane Porcelain Primer (BISCO, Inc.). The teeth were etched using SELECT HV® ETCH 35% Phosphoric Acid Etchant with BAC (BISCO, Inc.). Because the product contains benzalkonium chloride, a known antimicrobial agent, it was determined that no additional antimicrobial cleansing was necessary.
This treatment was followed by bonding with the adhesive resin ALL-BOND UNIVERSAL® Light-Cured Dental Adhesive (BISCO, Inc.). The bonding agent was placed on the tooth, dried with an A-dec air dryer, and light-cured. A light coat of bonding agent was placed in the veneer, followed by the eCEMENT Translucent shade. Starting with tooth No. 8, the veneer was seated and excess cement was removed prior to curing. A 1-second cure was performed and further excess cement was removed with floss in the interproximal contacts. The cement was then cured for 40 seconds; each veneer was seated in this manner. The veneers were adjusted for proper occlusion and minor esthetic refinements were completed (Figure 4). The patient was provided with postoperative instructions before returning home. A follow-up appointment was scheduled for 4 weeks later to allow time for proper tissue healing.
Conclusion
Use of the proper cement when placing lithium disilicate veneers is a tremendous advantage during the cementation phase. Ideal cement viscosity makes clean-up easy, which is an important factor in patient maintenance of gingival health, and great bond strength ensures longevity of the restorations. The cement selected can also affect the final esthetic outcome, which is largely dependent on the preparation color and the laboratory technician’s skill in proper porcelain fabrication. Ultimate success for the patient is determined by the longevity of the veneers with regard to both esthetics and function.
References
1. Adolfi D, Fradeani M. Feldspathic stacked porcelain veneers and pressed porcelain veneers. J Cosmetic Dent. 2012;28(1):66.
2. Dawson PE. Functional Occlusion: From TMJ to Smile Design. St. Louis, MO; Mosby Elsevier; 2007.
3. Kois JC. Treatment Planning I: Diagnostically Driven [manual]. Presented at: Course I: Treatment Planning I; June 2007; Seattle, WA.
4. Morley J. Advanced Anterior Esthetic Seminars [lecture notes]. Presented at: Morley Seminars Training; July 2000; .
5. Chiche G, Pinault A. Esthetics of Anterior Fixed Prosthodontics. Chicago, IL; Quintessence Publishing Co.; 1994.
6. Magne P, Belser UC. Bonded Porcelain Restorations in the Anterior Dentition: A Biomimetic Approach. Chicago, IL; Quintessence Publishing Co.; 2002.
7. Touati B. Extensive prosthetic rehabilitations with multiple all-ceramic crowns. In: Romano R, Bichacho N, Touati B, eds. The Art of the Smile. Chicago, IL; Quintessence Publishing Co.; 2005:25-38.
About the Author
Fred Peck, DDS, AAACD
Private Practitioner
Cincinnati, Ohio
