Zirconium Dioxide (ZrO2) – or “Zirconia” as it is more commonly known, was discovered in 1789 by the German chemist M. H. Klaproth. However, it was only introduced into dentistry a few decades ago: a product of the increasing desire for highly esthetic restorations. Zirconia became an attractive alterative material in dentistry because of its high esthetic potential and comparable strength to traditional metals. In the field of implant dentistry, Titanium has been the mainstay in implant manufacturing; however, Zirconia became a viable option because it possesses superior properties, including a higher tensile strength, compressive strength, and modulus of elasticity when compared to either Titanium alloy or commercially pure Titanium.
Clinical benefits of One-piece Zirconia Systems
- Having a single stage procedure.
- Decreased chair time – preparing the abutment is similar to preparing a traditional crown, and intuitive for the experienced operator.
- Less complex armamentatium, fewer parts required for restorative procedures.
- Elimination of lab time for implant abutment fabrication; no need for healing abutments, screws, analogs or transfer copings.
- No internal screws, no internal gaps, no micro gaps, fewer locations for hardware failures.
- Excellent soft tissue integration.
- Less consequences from gingival recession. As minor recession may occur over time when chewing forces are extreme, and exposure of the white implant surface will be less noticeable than Titanium.
- No gray gingival show through. Zirconia implants will never cause the unaesthetic gray gingival tint which attracts the eye and makes Titanium implant restorations in the esthetic zone very challenging.
- Flexural Strength. Zirconia is bone friendly and has good flexural strength for supporting implant prostheses.
- Improved gingival health. Due to the lack of micro gaps and the neutral polarity of the implant surface, there is much less tendency to have an erythematous, inflamed implant neck as is often seen after removal of the healing abutment with Titanium implants.
- Force distribution. The one-piece design allows force to be transmitted equally throughout the structure.
- No metal parts. Zirconia is the only material outside of Titanium being used for dental implants. This is advantageous for those with metal allergies or with an interest in holistic dentistry.
Clinical Disadvantages of one-piece Zirconia Systems
- The implant must be protected during healing.
- Less ability to compensate for incorrect implant angulation.
- Necessity for good patient compliance. Not every patient may be able to be compliant enough to allow for the necessary healing phase without force being applied to the implant.
- The healing process may last from 3 to 6 months, depending on bone quality.
One-Piece Implant Concept
The one-piece component implant was conceived in an attempt to copy nature. Imagine an implant restoration without micro gaps, internal screws, or inner gaps. The one-piece implant allows axial forces to be applied into a solid structure without attachments, made entirely of one material with no physical interruption and excellent flexural strength. One of the major advantages of the “HIP” processed Zirconia is its ability to be prepared intraorally, as ceramics do not conduct heat like metal or natural tooth structure. Preparation of the abutment can occur immediately after insertion or after osseointegration, and allows what is essentially a custom abutment to be prepared. Despite these apparent advantages, there has been a well-documented history of unsuccessful one-piece titanium implant systems, which has hindered the ability of the Zirconia one-piece implant gain acceptance into the implant community. These Titanium one-piece systems were often used to also provide immediate loading, which has not been shown to provide predictable success. Unlike the Titanium one-piece implant, the goal of the Zirconia one-piece is not to provide immediate loading, but to provide immediate aesthetics. One should also consider the differences in the cost of manufacturing and the environmental implications for one and two-piece implant systems. Certainly the engineering of the many intricate components of the two-piece implant system is fascinating, but it creates exponentially more leftover material and pollution to process the much greater number of parts. The implant industry is an ever-expanding, multi-million dollar enterprise that may see little benefit from reducing the number of parts involved in implant systems, as this may in turn reduce profit. Despite this, the need for more efficient and environmentally friendly industrial operations is critical and the push towards a more economical solution will continue. In the world we’re living in today, my opinion is that less is more and that a one-piece implant is an all-around better solution, like the one-piece tooth we all are born with.
The Zirconia Implant surface characteristics
Zirconia has been shown through a number of clinical studies to have great tissue biocompatibility and long-term stability. When in contact with tissue fluids, the implant surface carries a neutral polarity which disables bacterial aggregation. This, in combination with the lack of a micro gap, makes the one-piece Zirconia implant a great tool for management of the soft tissues. These characteristics allow for excellent gingival health and even spontaneous growth of soft tissues, which is an advantage for the long-term esthetics of dental implants.
Bone and soft tissue level
Just as with any dental implant, the best aesthetics will be achieved when the implant has good bony support on all four walls. Clearly this is best accomplished with an atraumatic extraction and ideal placement of the implant, but when this is not possible, bone grafting may be necessary. If a significant amount of marginal bone is lost during extraction or there is a vertical discrepancy in ridge height compared to adjacent teeth, an implant restoration will require a longer crown to compensate. This situation should be avoided in the esthetic zone, particularly in patients with a high smile line. If a one-wall or small volume defect is present and the patient is planned for immediate implant placement, bone grafting material may be used, which is very well-accepted by Zirconia implants. For larger defects where a significant volume of bone is missing, a two-stage procedure should be undertaken and implant placement delayed until completion of grafting.