With the help of Kuraray Noritake’s powerful material, this clinician helps patients achieve the smiles they want without sacrificing the durability they need.
Introduction
Restoring damaged or missing teeth is an essential aspect of modern dentistry. Advances in materials and techniques have improved dentists’ ability to achieve predictable, long-lasting outcomes. One such advance is the use of chairside esthetic zirconia crowns, which provide excellent strength and durability without compromising esthetics.
KATANA Zirconia ONE
The new and improved block, KATANA™ Zirconia ONE, is a multilayered block consisting of 4 layers of zirconia in graduated shades. The block allows the chairside fabrication of natural-tooth-colored restorations, eliminating additional sintering time. The flexural strength has improved to 933 MPa.
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This case report discusses the use of chairside esthetic zirconia crowns as a viable option for restoring the patient’s smile, highlighting the clinical and technical aspects and the rationale behind selection of materials and techniques used in the procedure.
Patient Presentation
A healthy man aged 66 years presented for a hygiene visit and examination with a chief complaint: he was unhappy with the appearance of his broken upper front 2 teeth. Exam and x-ray findings revealed incisal fractures of both maxillary central incisors, advanced palatal attrition, a deep anterior overbite, and failing Class III resin restorations with recurrent decay on tooth #9 distal and #10 mesial.
The fractures did not involve the pulp and patient was otherwise asymptomatic (Figure 1).
An intraoral image illustrating the condition of the maxillary incisors was taken with the CEREC Primescan (Dentsply Sirona) for patient education. The clinicalimage was shown to the patient, and upon being advised of the findings, he agreed to proceed with full contour crowns to restore both maxillary central incisors and a direct resin restoration for his maxillary left lateral incisor.
Clinical Objective
The clinical objective of this case was to restore the esthetic form and function of the maxillary incisors in the most predictable manner, utilizing the most appropriate materials and techniques for long-term results.
Technique
At the initial visit, a series of digital diagnostic photos was taken for smile design planning. Dual full arch digital impressions with the CEREC Primescan were taken and sent via CEREC Connect to the dental lab technician for the fabrication of a digital diagnostic wax-up of the maxillary central incisors.
At the time of the procedure, both failing composite restorations were removed and the recurrent caries excavated. CARIES DETECTOR (Kuraray America, Inc) was applied to assist in verification of complete caries removal. A composite buildup was placed on tooth #8 using CLEARFIL™ SE Protect, CLEARFIL MAJESTY Flow, and CLEARFIL AP-X composite resin (all Kuraray). A direct resin restoration was placed on #10 using CLEARFIL SE Protect Primer & Bond, MAJESTY Flow, and MAJESTY composite resin.
CLEARFIL SE Protect provides excellent bond strength and has an antibacterial cleansing effect. The author has also found that patients report no incidence of postoperative sensitivity with cases utilizing CLEARFIL SE Protect.
After the composite buildup and minimal preparations with conservative chamfer margins, preparations were completed. The lower jaw, upper jaw, and buccal bite were recorded using the CEREC Primescan in the acquisition phase. The virtual models were then created (Figure 2).
Splinted provisional crowns were fabricated using Bis-Acryl Luxatemp (DMG America) injection technique into a putty index of the printed diagnostic wax-up model. The gingival embrasures were left widened to allow for proper hygiene and to prevent gingival inflammation. The provisionals were cemented with Durelon™ Carboxylate Luting Cement (3M) and the patient was dismissed.
In this case, functional and esthetic demands were high. A high-strength restorative material was needed for long-term predictability and to prevent breaking. The patient had a history of incisal fractures, attrition, deep anterior overbite, and class II malocclusion, and was missing a few posterior teeth bilaterally. The patient’s goal was to restore the esthetics of his smile. KATANA™ Zirconia ONE (Kuraray America, Inc) was selected for the final restorations for its ability to deliver strength without compromising the esthetics.
KATANA Zirconia ONE is a high-strength translucent multilayer block with numerous benefits. There are no shade gradation gaps; each layer has the same high strength; it mills without chipping; and it allows for conservative tooth preparations.
The final crowns were designed in the CEREC 5.2.4 CS software using the biocopy method of an imported STL file of the digital diagnostic wax-up provided by the lab technician. The restoration design proposals were reviewed and modified for proper material thickness, occlusion, contacts, and contours (Figure 3 and Figure 4).
KATANA Zirconia ONE is a multilayer block with 4 zones of different chroma. Using the CEREC 5.2.4 CS software, the clinician can manipulate how much of each layer is desired in the restoration simply by moving the restoration within the block in the manufacture phase. (Figure 5).
The final crown restorations were fabricated using KATANA Zirconia ONE A2 blocks with Dentsply Sirona’s Primemill on the EF (extra fine) milling mode. The margins milled beautifully without chipping. The intaglios milled out incredibly smooth without any overmilling (Figure 6).
Prior to sintering, the sprues were removed with a carbide bur (HM498 FX023, Meisinger USA) at 10,000 fixed on a lab handpiece (Figure 7).
The restorations were then prepolished using Meisinger twist polishers. The EF milling mode on the Primemill produced the detailed anatomy and texture from the digital design, eliminating the need for further hand contouring of the restoration on the lab bench prior to sintering (Figure 8).
The restorations were sintered in the rapid 18-minute cycle using Dentsply Sirona’s CEREC SpeedFire Oven. Post sintering, the KATANA ONE Zirconia Crowns (Kuraray America, Inc) were then stained and glazed using MiYO® Esthetic InSync (Jensen Dental) glaze pastes and colors and fired in the CS Programat Furnace (Ivoclar) (Figure 9).
Final polish was completed with DiaShine® Fine Soft Paste and an Abbott-Robinson wheel.
The patient returned without complaints for the delivery of the final restorations. The crowns were tried in the mouth and proper marginal fit, contacts, occlusion, and esthetics verified. The patient was thrilled with the appearance of the new crowns and approved final permanent cementation.
After the try-in, the intaglio surfaces of the restorations were microetched with aluminum oxide, 50-µm white (Microetcher; Danville). Next, they were steam cleaned and air-dried with an air syringe.
To deliver the crown for final placement, PANAVIA™ SA Cement Universal (Kuraray America, Inc) was used in conjunction with CLEARFIL Universal Bond Quick (Kuraray America, Inc). PANAVIA SA Cement Universal contains MDP, eliminating the need for a separate zirconia primer. It allows for extremely easy cleanup, which makes it even more advantageous.
Summary
This case demonstrates how high strength full-coverage zirconia crowns can now be designed, produced, and placed without compromising the esthetic result using KATANA Zirconia ONE. The results were the delivery of restorations with superb strength of 933 MPa with very beautiful esthetics that rival glass ceramics.
The final restoration blended seamlessly among the neighboring teeth (Figure 10).
The patient expressed his gratitude and appreciation for the appearance of his new smile. When placed adjacent to all-ceramic lithium disilicate crowns, the clinician will note comparable esthetics and translucency.
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