The topic for today’s article is one of the modern and very popular solutions in the field of aesthetic dentistry. Let’s take a closer look at zirconium crowns for teeth: advantages and disadvantages, installation procedure, manufacturing materials, care nuances, and differences from other types of prostheses – all so that you decide whether they suit you or not.
What are their features?
These are the so-called metal-free constructions, which are now in demand for the restoration of the jaw row. They are made from a natural material, very durable and environmentally friendly, additionally enriched with aluminum and stabilized with yttrium. As a result of this treatment, an attractive white color (and without an unnatural sheen) and moderate transparency were added to the natural hardness and durability.
If you look at what a zirconium crown looks like, and what it is in dental practice, you will see that it is a multilayer blank, soft and pliable. For top manufacturers, for example, Katana or Kuraray Noritake, this is a disc block – a set from which you can “blind” a design of the desired shape, as convenient and correct as possible for the patient’s jaw, and then finally bake it. This approach allows you to achieve the best results from prosthetics.
Before the development of computers, the manual turning of material was unnecessarily laborious. But with modern technology, the process has been automated, and thanks to digital scanning, CAD/CAM design, and robotic manufacturing, the best precision possible.
Indications/contraindications for installation
Considering why zirconium crowns are good, what they are, and what features they have, it should be noted that dentists do not always recommend them.
These dentures are not advised if:
- There is a serious malocclusion (it is too deep);
- Incisors are very small;
- There is bruxism and there is a possibility that the antagonist premolars will quickly wear out;
- In the oral cavity, infection, and/or inflammation – first the patient will need to be cured;
- The client has a systemic disease that reduces immunity, for example, AIDS, diabetes, oncology;
- A person suffers from psychosis;
- The woman who came to restore her smile is pregnant.
Well, the indications for installation are as follows:
- The enamel has changed its color (visibly darkened or turned yellow);
- There are congenital anomalies in the height or shape of the teeth;
- There are tremas and/or diastemas and they are too large;
- The incisor or molar is destroyed by caries or significantly chipped;
- Intolerance to all other dental materials was revealed.
Types of crowns based on zirconium dioxide: what are these prostheses
They are distinguished by translucency, that is, by the degree of light transmission – according to this parameter, 3 types of them are distinguished:
- With minimal transparency (STML in Katana classification); they are durable, resistant to stress, and suitable for those people who have the wrong bite.
- With reinforced – not so hard, but provide as close to the natural color as possible; replace individual jaw units, in the lines of Japanese manufacturers are marked HT.
- With the maximum – their other name is ultra translucent; despite the apparent fragility, they are very practical, therefore they are the best choice for anterior teeth, and also aesthetic – they do not need additional coating, they are designated as UTML.
In addition, according to their design, all crowns are divided into 2 types – we will consider each in detail.
Models on a zirconium crown frame
Modern classics – two-layer, with a geometry modeled after metal-ceramic. Such prostheses have a solid base, made of a single piece, with an aesthetically attractive phosphor coating. They perfectly decorate a smile, outwardly not differing from natural jaw units. Usually, they are installed in front, but they are not suitable as molars, as they can crack or even chip in the process of eating.
In full anatomy, monolithic
So, all-zirconium crown, what is it? In fact, a tooth that is carved from a piece of mineral is hardened and strengthened. It does not look as impressive as the previous type (although it is also quite aesthetically pleasing), but it is distinguished by maximum strength, and hence practicality. The best choice for the chewing area, but you can put it in front.
Such a prosthesis is coated with special paints to give it the desired color and then fired to finally fix its performance characteristics.
Why zirconium crowns are good: pros and cons
For objectivity and clarity of comparison, we summarize their advantages and disadvantages in a table.
- It Withstands mechanical loads as well as metal
- Not afraid of corrosion
- Galvanically neutral – do not oxidize
- Tightly adhere to the remains of a destroyed tooth, which means they sit perfectly
- Look natural and aesthetically pleasing
- When preparing, they require minimal preparation of the jaw unit
- Freely transmit x-ray
- Hypoallergenic and fully compatible with the soft tissues of the human body
- Do not bring discomfort during the reception of cold or hot food
- The risk of rapid erasure of molars from the opposite row
- There is a possibility of chipping off the decorative porcelain coating
- Relatively high cost
And one more practical point – you can easily attach a zirconium crown to an implant: the advantages and disadvantages of prostheses are at a glance and, as you can see, there are much more pluses than minuses, and they are more important. Therefore, this technology can and should be used to ennoble a smile.
This is a multi-step process. The time spent at each stage may vary depending on the condition of the patient’s oral cavity: in some cases, problems are eliminated in 1 visit to the doctor, and somewhere in 2-3 sessions. Other works – analysis, design modeling, its turning on a robotic machine – in all situations are approximately equally fast, thanks to the use of modern computerization tools. Let’s look at the steps in order.
Diagnosis and treatment
The orthopedist examines and refers to the dentist-therapist. And this expert:
- Finds and eliminates pathologies – caries, inflammation of the gums, diseases;
- Makes x-rays clean canals, removes pulpitis, performs filling;
- Puts pin tabs to provide extension;
- Removes a completely destroyed jaw unit and implants an artificial root.
In the latter case, you will have to wait for engraftment for several months. After that, the patient will be ready to return to the orthopedist and proceed to the second stage of installation.
It is mandatory, and we mentioned it when we compiled a table of the features of zirconium crowns and the advantages and disadvantages of their varieties. However, you will have to remove a very small layer of enamel – about 0.4 mm. And this is a painless procedure since there are simply no nerve endings in hard tissues. Although those who have hypersensitivity, or those who are simply afraid of dental operations, will definitely be offered local anesthesia.
Teeth fluoridation – what is it and what is deep fluoride treatment for?
Impression taking, temporary prosthetics
In just a couple of minutes, a 3D scanner will create a three-dimensional model of the jaw unit, after which the data will be sent to the CAD / CAM program used. She will automatically process and, strictly according to the data, make a sample for the future crown; again, it won’t take long – an hour, no longer. To protect the oral cavity from damage, the processed incisor will be closed with a plastic cap.
Making the right design
It is machined on a computerized milling machine – from a block blank of the material in question, in accordance with the design results. The result is a prosthesis that perfectly repeats the shape and even the shade of the color of the destroyed jaw unit. It undergoes firing and, due to sintering, acquires density and strength. If it is two-layer, a phosphor coating is applied to it, after which it is subjected to repeated heat treatment.
The fitting, final installation
Usually, these two operations are carried out in one visit. And all because, when it comes to zirconium crowns for teeth, the pros and cons, the key advantage in their manufacture is a high degree of precision in the processing of the mineral. The resulting design will be able to fit really tightly, it will not have to be corrected, and it will not slip or fall off.
If the patient experiences discomfort during fixation, the orthopedist grinds the prosthesis on his own; when this is not enough, the doctor sends it back to the laboratory and indicates which geometry parameters need to be corrected. Then the client will need to visit the doctor’s office again.
For high-quality fixing, the selected model sits on dental cement. All work takes half an hour, no more.
Complications, possible problems
If the installation is done correctly, no further difficulties arise. True, immediately after it, some people experience a feeling of excessive tension in the masticatory muscles, and the diction becomes slightly slurred, but these are shortcomings of zirconium crowns caused by the habituation of the jaw, and they quickly pass, in just a few days.
Worse, when the adjacent tissue begins to become inflamed if caries begins. This happens when the preparation for prosthetics was performed poorly if the jaw unit was not sealed. Faced with this, the orthopedist will decide how to treat – with the removal of the prosthesis or through the hole made in it. The appearance of such problems is also possible in cases of insufficient fit, but this happens very rarely because the model made from the cast accurately reproduces the shape of the tooth. In practice, this happens when something bothers the patient, but he is embarrassed to admit it. Therefore, when installing, it is so important to inform the doctor about even the slightest feeling of discomfort.
Complications include the following symptoms:
- Severe pain at the site of surgery, high body temperature, chills;
- Swelling of the gums, redness, and inflammation at the point of manipulation;
- Loosening of the prosthesis.
With the manifestation of any of them, it is necessary, without delay, to sign up for a consultation with an orthopedist.
Considering dental crowns made of zirconium oxide (what are they, pros and cons, design options), we almost lost sight of one important detail – they do not require any special attention. It is enough just to clean them in the morning and in the evening, using a regular brush and paste, and follow a few simple and logical rules:
- Rinse your mouth with water after each meal;
- Remove food particles stuck in the gaps with floss or irrigator;
- Do not gnaw hard foods – caramel, nuts (chocolate or apples are possible);
- Visit the dentist twice a year – for prevention and professional treatment.
The cost of these prostheses
When it comes to the disadvantages and advantages of zirconium crowns, the price is often considered a minus – they say that it is too expensive and the like. Yes, they are more expensive than cermets, but they are more practical.
The amount of their manufacture and installation, by the way, in different clinics can be quite different – it consists of a number of factors:
- Costs for diagnostics and preliminary treatment (caries, pulpitis);
- The need for implantation of an artificial root;
- Type of the selected model – two-layer or monolithic;
- Orthopedic qualification;
- Location and reputation of the medical institution;
- Do you have your own laboratory or do you have to involve third-party specialists;
- Use of computerized equipment in the design.
Metal-ceramic or zirconium crowns: what are these options, which is better
For the most objective comparison, we will again use the clarity of the table.
- Compatibility with soft and hard tissues
- Preparation features
- Installation locations
- The nature of the manufacture
- Color change
- Implant compatibility
- prone to chipping
- Sometimes cause irritation and related reactions
- Require to remove of up to 2 mm of enamel
- Side sections
- Manually, with far from the highest accuracy
- Medium, their artificial origin is often not hidden
- Lose luster and transparency over time, become gray
- With contraindications and reservations
- Differs in hardness (especially in monolithic execution)
- Completely hypoallergenic
- The layer is not so significant – only 0.4-0.5 mm
- Whole jaw (depending on the type of prosthesis)
- On a robotic machine, according to a 3D model made thanks to CAD / CAM
- aesthetic; look and read on the Internet how metal-ceramic and zirconium crowns look, the shortcomings (according to reviews and photos) of the first are noticeable even with a cursory comparison
- Remain exactly the shade that was selected in the manufacture
- Cost a little more
The selection of a specific option should be carried out individually, taking into account not only the strength and aesthetics but also the maximum possible mass of the prosthesis (if it turns out to be too heavy, this will lead to a gradual decrease in the gums). There is no particular difference in the issue of complexity, duration, safety, and quality of the installation – it all depends on the skill of the doctor.
And yet, after analyzing the pros and cons of zirconium crowns, we can say with confidence that they are definitely not inferior to metal-ceramic ones, even in terms of service life. If properly fixed, you can wear them for up to 15 years or even longer without worrying that they will turn yellow – just polish them at the dentist twice a year – eating cold and hot food and not experiencing discomfort, sparkling with a snow-white smile. And if at the same time, you also do not forget about caution – gently bite hard foods and do not gnaw nuts with sweets – then you won’t have to think about cracks and chips.
So, is this a good choice? Yes, definitely, especially considering how widely zirconium crown is used in dentistry today: crowns, with their pros and cons, are already well understood. It is known how such prostheses will “behave” in the future for 10-15 years, and it is clear that they will not bring unpleasant surprises – so put them on and wear them in good health.