Introduction:
Zirconia has become a material of choice in prosthetic dentistry due to its exceptional mechanical strength, chemical stability, biocompatibility, and esthetic potential. However, unlike silica-based ceramics, bonding to zirconia remains a clinical challenge, as conventional etching and silanization protocols are ineffective. Achieving durable adhesion requires a combination of optimized surface treatments and adhesive protocols. With the integration of digital workflows and computer-aided design and manufacturing (CAD/CAM) technology, even single-unit restorations like zirconia crowns can benefit from high precision, reduced chair time, and enhanced predictability. This case demonstrates how a fully digital approach, coupled with evidence-based zirconia bonding techniques, can elevate a routine restoration into a long-lasting esthetic and functional success.
Clinical Case Figures and Analysis
The patient presented with pain related to tooth 15, which was undergoing endodontic treatment. Clinical evaluation revealed extensive caries, requiring complete caries removal and core build-up prior to tooth preparation and prosthetic rehabilitation.
After caries removal on tooth 15, a rubber dam was placed to retract soft tissues, isolate the operative field, and ensure a comfortable working environment. In this case, the printed CR-Template was used as a digital, everyday solution for efficient and esthetic rubber dam isolation.
A QuickmatFLEX posterior sectional matrix was used in combination with a plastic wedge, both from Polydentia SA, Lugano, Switzerland, to maintain proper interproximal contour and prevent adhesive interference with adjacent teeth.
According to Hardan et al., achieving optimal adhesion requires not only the appropriate adhesive system but also meticulous handling and isolation. It has been reported that resin‒dentin bond strength may be compromised by high intraoral humidity (78‒94%) and contaminants such as saliva, blood, crevicular fluid, or handpiece lubricant. To address these challenges, the rubber dam is considered essential in restorative dentistry. Its use reduces humidity to ambient levels, promoting stable and durable adhesion to dentin. Moreover, it enhances clinical visibility, visual contrast, and remains a cost-effective and highly efficient isolation method.
A total-etch technique was performed, with the etching agent actively rubbed onto the enamel surface for at least 20 seconds to ensure effective etching and optimal micromechanical retention.
The adhesive agent was applied using ZerofloX™ (MIXPAC Dental, Medmix AG, Baar, Switzerland), a fiber-free micro-applicator equipped with flexible elastomer bristles. This design enables precise and clean delivery of adhesive without the risk of fiber contamination on the bonding surface.
Tooth preparation was completed using retraction cord for optimal gingival management. Leveraging advanced digital dentistry techniques, an intraoral scan of the prepared tooth was performed with the Helios 500 scanner (Eighteeth Company, Changzhou, Jiangsu Province, China) to capture precise digital impressions for subsequent restorative procedures.
Helios 500 fast acquisition speed and intuitive operation enhanced procedural efficiency, contributing to a smooth and reliable digital process. With its clinically proven accuracy, the Helios 500 provided valuable support in achieving the expected outcomes and long-term stability of the zirconia restoration.
The prepared tooth can be clearly seen from multiple views, including visualization of the patient's lower arch.
Shade matching was performed prior to delivery to the patient. The image was captured using the central LEDs of the Smile Lite MDP2 (Smile Line, Switzerland) at maximum power and a polarizing filter placed over the central light. This setup eliminates surface glare, allowing for accurate assessment of tooth color, brightness, and surface features such as incisal halos.
Polarized photography is a non-invasive, contactless technique that enhances contrast and color saturation, making it useful for clinical applications including shade matching, white lesion detection, diagnosis, and monitoring of bleaching treatments. As described in Chapter 6 of Prof. Louis Hardan’s book, this method is simple to perform, requires minimal training, and significantly improves the clarity of intraoral images for diagnosis and documentation.
The captured image was then sent to the laboratory technician to accurately replicate the natural tooth color in the final restoration.
The Standard Tessellation Language (STL) file of the scanned area clearly displayed all details, reflecting the accuracy of the scanner and facilitating precise communication with the laboratory technician.
After receiving the STL files, the models were printed using the Sprintray Pro 2 printer (Los Angeles, CA, USA) with a layer thickness of 100 micrometers (µm). Several studies have shown that varying the printing layer thickness influences the properties of three-dimensional (3D)-printed dental models and materials. For example, Favero et al., reported that models printed using stereolithography (SLA) at different layer heights all met clinically acceptable accuracy standards, with 100 µm layers demonstrating less deviation compared to finer 25 µm layers.
After completing the design using exocad DentalCAD software (exocad GmbH, Darmstadt, Germany), the premolar zirconia crown was milled from an Aizir zirconia disc. Aizir (Aidite Technology Co., Ltd., Qinhuangdao, China) represents the company’s most advanced research and development achievement, integrating several patented technologies into a single disc. This material supports a wide range of clinical indications and offers enhanced systematic processability, a broader sintering temperature range, and a more stable 3D gradient structure. Aizir is designed to contribute to the vision of "Everyone with a healthy and beautiful smile," aiming to redefine the standard of all-ceramic prosthetic materials.
To verify precise adaptation, the crown was first placed on a 3D-printed model prior to clinical delivery.
After milling, the zirconia crown was stained and glazed with Aidite Stain / Glaze external dye paste (Aidite Technology Co., Ltd.,Qinhuangdao,China). This step was essential, as tooth #15 is visible when the patient smiles, and staining allowed for a better esthetic match with the adjacent natural teeth. Studies have shown that the zirconia stain layer requires only a minimal thickness (less than 80µm) to achieve clinically acceptable esthetic results. Additionally, different stain systems can enhance surface smoothness and maintain crown cleanliness. The staining system used in this case met clinical criteria for shade reproduction and surface quality, making it a suitable choice for achieving a natural-looking all-ceramic restoration that harmonizes with the adjacent dentition.
The crown underwent internal surface treatment using Biomic LiSi Connect (Aidite, Qinhuangdao, China). This specialized lithium disilicate-based coating is applied to the intaglio surface of zirconia restorations after one sintering. Upon sintering, LiSi Connect crystallizes into a tightly bonded lithium disilicate layer, forming a glass-ceramic-like interface that significantly enhances the adhesive properties of zirconia.
The ultra-thin coating—measuring approximately 6‒10 µm—does not interfere with the restoration's fit or clinical placement. Following sintering, the zirconia surface exhibits a crystalline structure similar to that of glass ceramics. When subjected to acid etching, this surface develops a rough, porous morphology conducive to micromechanical retention.
LiSi Connect-treated zirconia shows comparable bonding performance to traditional glass ceramics, enabling stable and durable adhesive bonding. The material is compatible with all types of zirconia and supports high bond strength, even for zirconia veneers. Its ability to penetrate the zirconia surface and create a strong, integrated bonding layer makes it a reliable choice for improving the long-term clinical success of zirconia restorations.
A uniform layer of LiSi Connect was sprayed onto the surface of zirconia after its final sintering, followed by sintering according to the manufacturer's specified thermal protocol.
Afterwards, acid etching was performed to condition the lithium disilicate-coated surface. Two options were available: 4.5% hydrofluoric acid (HF) for 90‒120 seconds, or 9.5% HF for 45‒60 seconds. This etching step generated a rough, micro-retentive surface to enhance bonding.
Bonding was completed using a resin-based adhesive. A dual-cure resin cement was selected td to ensure both functional durability and optimal esthetic outcomes.
The final outcome in this case highlights how digital dentistry significantly enhances precision, enabling the fabrication of a well-adapted, natural-looking restoration. As observed from both occlusal and frontal retracted views, the zirconia crown demonstrated excellent esthetic integration and precise adaptation. Impressed by the result, the patient chose to proceed with the restoration of the adjacent teeth to promote a healthy, caries-free oral environment. Although restoring a single crown can present challenges in achieving optimal esthetics, this case illustrates the potential of digital workflows to overcome such limitations.
Conclusions
This case illustrates the successful integration of advanced digital dentistry protocols in the fabrication and placement of a single zirconia crown. From accurate intraoral scanning and CAD/CAM design to surface conditioning with Biomic LiSi Connect and precise staining techniques, each step contributed to achieving excellent esthetics, fit, and long-term bonding potential. The result not only met the patient's functional and esthetic expectations but also encouraged a proactive approach to restoring adjacent teeth. This case underscores the reliability of digital workflows in delivering high-quality, patient-centered restorative outcomes.
Bibliography
● Lin SC, Lin WC, Lin YL, Yan M, Tang CM. In vitro evaluation of the shading effect of various zirconia surface stains on porcelain crowns. Coatings. 2022 May 26;12(6):734.
● https://www.styleitaliano.org/zirconia-magic-where-strength-meets-beauty-in-dentistry/
● Favero CS, English JD, Cozad BE, Wirthlin JO, Short MM, Kasper FK. Effect of print layer height and printer type on the accuracy of 3-dimensional printed orthodontic models. American Journal of Orthodontics and Dentofacial Orthopedics. 2017 Oct 1;152(4):557-65.
● Paul N, Swamy KR, Dhakshaini MR, Sowmya S, Ravi MB. Marginal and internal fit evaluation of conventional metal-ceramic versus zirconia CAD/CAM crowns. Journal of clinical and experimental dentistry. 2020 Jan 1;12(1):e31.
● Hardan L, Bourgi R, Cuevas-Suarez CE, Lukomska-Szymanska M, Monjaras-Avila AJ, Zarow M, Jakubowicz N, Jorquera G, Ashi T, Mancino D, Kharouf N. Novel trends in dental color match using different shade selection methods: a systematic review and meta-analysis. Materials. 2022 Jan 8;15(2):468.
● Hardan L, Bourgi R, Cuevas-Suárez CE, Devoto W, Zarow M, Monteiro P, Jakubowicz N, Zoghbi AE, Skaba D, Mancino D, Kharouf N. Effect of different application modalities on the bonding performance of adhesive systems to dentin: a systematic review and meta-analysis. Cells. 2023 Jan 3;12(1):190.
● Bourgi R, Qaddomi M, Hardan L, Tohme H, Corbani K, Abou Isber S, Daher EA, Nassar N, Kharouf N, Haikel Y. Gingival Contouring and Smile Makeover through Digital Planning and �D Guidance. J. Clin. Med. Res. 2025;6:6208.
● Hardan L, Bourgi R, Lukomska-Szymanska M, Hernández-Cabanillas JC, Zamarripa-Calderón JE, Jorquera G, Ghishan S, Cuevas-Suárez CE. Effect of scanning strategies on the accuracy of digital intraoral scanners: a meta-analysis of in vitro studies. The Journal of Advanced Prosthodontics. 2023 Dec 18;15(6):315.
● AL‐Amleh B, Lyons K, Swain M. Clinical trials in zirconia: a systematic review. Journal of oral rehabilitation. 2010 Aug;37(8):641-52.
● https://www.styleitaliano.org / introducing-printed-cr-template-an-everyday-solution-to-rubber-dam-isolation/
● https://www.styleitaliano.org/rubber-dam-perforations/
About Eighteeth
Changzhou Sifary Medical Technology Co., Ltd, founded in 2016 in Changzhou, Jiangsu, is a professional manufacturer of dental equipment and consumables, as well as a leading enterprise in the domestic dental medical equipment industry, committed to building the first platform for the globalization of Chinese dental instruments, The company's products (Eighteeth products) cover 154 countries and regions worldwide, and it has established cooperation with more than 340 renowned universities and thousands of top experts globally, reaching over a million dentists worldwide.
The company currently has a professional and mature team of nearly 500 people and has introduced mature and efficient R&D management systems, with significant product quality advantages, aiming to provide superior products and services to dentists and patients worldwide.