Crowns Zirconia: dental crowns on zirconium dioxide
The invention zirconium structures has opened new horizons in esthetic dentistry. The colour and shape of natural teeth today is a real trend. In this article we consider the basic properties of this material, indications and contraindications to the use of zirconium prostheses, manufacturing steps, advantages and disadvantages. Separately and on the role of digital simulation in achieving absolute precision designs.
Zirconia: what is it
Zirconia is one of the most widely used material in CAD/CAM modeling. Base for the production is zircon. Zirconium oxide obtained by a certain chemical treatment. Next, the powder is mixed with additives, some of which determine the temperature regime of the sintering of the prosthesis, others affect the forming. Specialists also distinguish and translucent Zirconia. By and large it’s the same material, but with improved transparent properties. Thanks to a good combination of aesthetic and physical characteristics, a modified zirconium dioxide can be used to restore both front and side teeth.
What is the superiority of crowns based on zirconium dioxide?
Let’s look at why dental crowns made of zirconium dioxide have become so popular.
- High strength superior physical properties even some metal frames. Also, this material does not deform with time (strength of the fracture exceeds the fracture strength of the human tooth is almost in 8 times).
- Perfect aesthetics. Prostheses based on Zirconia look natural, they are impossible to distinguish from natural teeth.
- Hypoallergenic. No metal component minimizes the likelihood of allergic reactions that is often observed when solid metal and metal-ceramic constructions.
- Absolute biocompatibility. The chemical stability and biological indifference, Zirconia has no aggressive effects on periodontal tissues.
- Optical identity. Since the frame structure is a transparent material, the prosthesis perfectly integrated into the dentition. Because the indicators light transmittance of Zirconia and teeth enamel is practically identical.
- Low thermal conductivity provides reliable protection polovoy the camera. Now with the prosthetics on live teeth can not be afraid of changes in temperature that is observed in the case of using sintered metal.
- Ease of design. Crowns made of zirconium dioxide have a much lower weight than metal-ceramic counterparts.
- The color stability. The chemical stability, the color of the design does not change with time.
- No dark line along gingival margin. The use of dentures with a metal frame can lead to recession of the gums (when broken borders the edge of the structure) and exposure in the cervical region of the gray metal plates. The use of prostheses made of Zirconia, exclude the possibility of development of this complication.
- The integrity of the prosthesis. The relationship of the ceramic mass from zirconium dioxide, ensures a good adhesion between the framework and the facing material.
- Smooth outer profile makes the construction data No. 1 when the prosthetic implant. Why? Exclusively polished surface prevents the accumulation of plaque, prevents the development of inflammatory processes in the periodontium, improves oral hygiene.
Indications and contraindications: a brief overview
Shown crowns based on zirconium dioxide for the restoration of the anatomical shape, color, function of the teeth and for replacement of defects of dentition (as through the use of dental bridges, and dentures on implants). Metal-free dentures doctors do not recommend to apply in case of:
- Deep bite.
- The low height of the clinical crowns.
- The presence of inflammatory processes in oral mucosa.
When dentition defects large extent, it is better to choose metal fittings.
Relative contraindications include:
- mental disorders in the period of exacerbation;
- acute infectious diseases;
If solid metal, metal-ceramic prostheses technician models in their own hand, for the manufacture of ceramic structures has developed a special high-tech computer program. We are talking about CAD/CAM modeling. This allows you to save time and also significantly improves the accuracy of prostheses (accuracy up to 40 microns).
Program CAD/CAM consists of:
- Transmitting the image in 3 planes of the scanning device. This device can be in the form of intraoral camera in the doctor’s office, or it can be stationary equipment for use in the dental laboratory.
- The program, which is carried out by computer simulation. Options:
- modeling of the chewing surface on the basis of teeth-antagonists;
- a simple reconstruction of virtual design;
- the creation of prosthesis taking into account sredneakhtubinsky parameters of the teeth and dentition.
- Installation for cutting out frames. Depending on the number of cutters can be made from 1 to 14. The purpose of these devices is conventionally divided:
- for cutting regular ceramic;
- processing of hard ceramics;
- universal, with which it is possible to produce metal, plastic, and all kinds of ceramics.
System Cerek 1 – the first version of the program CAD/CAM. The prosthesis was carried out as follows: after preparation of teeth received optical impression (due to the display model on the screen). The process simulation was carried out using the computer.
Seek 2 consists of milling installation, the high resolution camera that allows you to achieve even more improvement of ceramic prostheses.
CAD/CAM is a revolutionary new equipment, allowing to achieve unprecedented accuracy and efficiency in prosthetic dentistry.
A software simulation can be used in the manufacture of:
- single crowns;
- bridges as a small and large extent;
- telescopic crowns;
- temporary structures;
- inlays, veneers;
- kultovyh tabs (solid and collapsible).
The stages of
We present our stages of dental prosthetics using CAD/CAM:
- A podiatrist holds teeth preparation.
- Get the prints.
- The technician pours a collapsible model.
- The model is placed in the scanner, where the scan conversion of the model parameters to the virtual digital image.
- The technician on the monitor screen produces modeling based on the scanned data of the surface relief of teeth. The reproduction is thus represented in three dimensions.
- After the modeling phase, information is transmitted to the production module.
- The set of commands supplied to the control unit and milling device, which is cutting out designs with all the pre-modeled characteristics and parameters. In the result, the technician is finished prosthesis.
- Sintering of the structure of Zirconia occurs in a furnace (at a temperature of 1600 degrees).
- Roasting gives the final prosthesis parameters: dimensions, hardness, transparency.
- The fitting of the prosthesis. Determining whether they comply with the requirements for construction as part of the physician and the patient. Fixation of the prosthesis on the permanent cement — the final stage of prosthetics.
Let’s look at the advantages of prosthetics with the use of systems for software simulation.
- The high precision of the prosthesis provides a perfect marginal seal, prevents the development of secondary caries, accelerates reparative processes in periodontal tissues.
- The ability to adjust the thickness of the frame.
- Achieving geometric accuracy of the structures at the replacement of the long defects.
- Digital monitoring of the occlusion.
- High speed of manufacture.
Always after delivery of the finished design, a podiatrist talks about the requirements of oral hygiene. The service life of zirconium crowns and other fixed constructions, depends on the quality of teeth cleaning.
- First, the patient should visit the dentist every six months for inspection and removal of dental plaque. Using ultrasound, a special set of polishing tools, paste (with the necessary calcium and fluorine, the desired level of abrasiveness), system Air flow, the hygienist removes the hard deposits and soft plaque («plaque smoker»), produces polished surfaces. At home to achieve this same effect using regular toothpaste and brush impossible.
- After setting crowns made of zirconium dioxide not to chew solid foods.
- Every meal should end with a rinse of the mouth.
- The cleaning should be done twice a day. Begin with sweeping movements, the direction of which in the upper jaw — from top to bottom, when cleaning the lower teeth from bottom to top. Also, remember that you need to clean all the walls (external and internal), for chewing surfaces, use a translational motion. Finish your oral hygiene in a circular motion (without pressure) in the area of the gums, making a kind of massage that will improve blood flow and tissue oxygenation.
- Except toothbrush and paste, for quality cleaning interdental spaces should floss, brushes.
If in the mouth fixed bridge, for purification washing space will be efficient irrigators. The detection of signs of inflammation of the gums (in the case of gingivitis, periodontitis) oral irrigator can be filled with decoctions of herbs such as chamomile, sage, calendula.
The possibility of using digital simulation, high precision design, chemical resistance, exceptional aesthetic properties, adequate strength, biocompatibility with periodontal tissues, all of these characteristics derive honored prostheses on the basis of zirconium dioxide on a fundamentally new level, leaving far behind «its main competitors».