Clinical Evaluation of Monolithic Zirconia Crowns for Posterior Teeth Restorations
The world of dentistry is constantly evolving keeping up with the needs of the ever changing and evolving mankind. More and more people want newer, quicker and modern solutions for all their problems and dental issues are not excluded from this. A lot of attention is now paid to aesthetics and appearance and other functions and factors may have taken a back seat today. The same applies to dental solutions and restorations but when it comes to medical sciences, functionality and resilience of a treatment modality can never take a back seat. This then created a demand for dynamic new methods and procedures that can help patients deal with their new age requirements.
Zirconia crowns can easily be the number one solution which bridges the gap between functionality and modern esthetics. Zirconia crowns have both resilience and appearance, both of which are extremely important for the new age patients today. Even in the case of pediatric patients, zirconia and other esthetically pleasing restorative materials are preferred over the conventional methods, let alone for adult patients. All in all, it is safe to conclude that modern dental age problems need a modern solution which is solved by Zirconia crowns.
Like any other crown, Zirconia crowns serve their purpose of replacing the original defective tooth and protecting what is left of the original tooth after the treatment procedure. It acts like a crown or a cap that sits on the original tooth and helps restore the functionality of the human tooth which includes:
- Mastication
- Jaw line features
- Self-esteem when talking or smiling
- Enunciation and speech
- Protection of the jaw bone etc.
Zirconia dental crown however does not stop at just that - these new age crowns are made from Zirconia dioxide which is stabilised using Yttrium that helps in various factors such as strength, resilience, durability and biocompatibility. The best feature of Zirconia is the white, opaque teeth-like colour that it has which can be made to easily mimic the actual human tooth. Zirconia tooth crown that is used in the anterior region can be colour matched and stained to match the patients’ actual teeth colour. On the other hand, Zirconia crown tooth can be easily used in posterior teeth as a perfect dental crown option that has excellent strength and which does not cause regression or wearing down on adjacent or opposing teeth. We will be discussing these features in detail in the section ahead.
Monolithic Zirconia Crowns
Monolithic Zirconia crown is the most common form of Zirconia crown that is milled out of a single block of Zirconium Dioxide and then designed as a crown using CAD/CAM technology for the specific size and measurement of the patient. They are usually solid white and are preferred for posterior restorations. They also lack the colour matching tendencies which is why they are preferred for molars and premolar restorations. Zirconia Ceramic crowns are milled and designed in labs but can be easily done in a dentists’ office as well with only a few modern technological equipment. This is another factor that aids in the preference of Zirconia crowns as they can be designed and made use within a few hours and therefore reducing the overall restoration time drastically.
Monolithic crowns are preferred by patients as well as dentists because of plenty of reasons such as:
1. Strength
When these crowns are milled from a single block and then developed into a crown using modern CAD/CAM technology, not only are they stronger and more resilient than the rest of the options, they are also more efficient as the technology eliminates any chance of error and variation in the restorative material over the process.
As such, Monolithic or solid zirconia crowns have better strength than its counterparts mainly because of the role of stabilisers. The Stabilisers that are used on ZIrconia crowns are higher in these solid crowns and therefore are more stronger and resilient than their counterparts. Yttrium is the most common type of stabiliser found in Monolithic Zirconia crowns for the posterior teeth.
2. Efficient
The entire process of developing and using a Monolithic crown is highly efficient and can be done in just a few hours. With only a few modern machines, dental labs can quickly develop their own crowns in-house which makes the turnaround for restorations much higher by reducing the time spent on crown preparations.
Because solid zirconias or the monolithic zirconias do not have any glazing process which needs higher time to create the right stain by matching the crown to the patients’ teeth, the process is preparing solid zirconia is faster than the other kinds.
3. Controls Teeth Wearing
Monolithic Zirconia crowns are also known for reducing the overall impact that they have on the surrounding teeth as they are drastically better than metal or ceramic crowns in this respect. They do not cause excessive wearing of the teeth adjacent or opposing the crown and are overall better. It may even be better as a choice when compared with its counterparts for patients who have Bruxism. Monolithic crowns do not wear down as much as other kinds of crowns during long term teeth grinding.
4. Better for Posterior Restorations
Since monolithic crowns are made with more stabilisers such as Yttrium, they are sturdy and more durable than Layered or Highly Translucent Zirconia crowns. This is why they can withstand more bite force and are perfect for molars and premolars and for posterior restorations as a whole.
Y-TZP or the Yttria tetragonal Polycrystalline stabiliser that may be used for solid or monolithic crowns is an Oxide additive which helps in increasing the strength and helps in stabilising the element by providing exceptional mechanical strength, flexural strength and fracture resistance to the element.
5. Cost
The cost of Zirconia dental crowns vary according to the type of zirconia crown selected and the procedure. Zirconia crown costs anywhere between a few hundred dollars but the Monolithic Zirconia prices are cheaper than its counterparts. The more translucent the crown is, the higher the Zirconia crowns’ cost. Most patients and dentists therefore prefer Monolithic zirconia crowns for posterior teeth because of its cost efficiency.
Use of Monolithic Crowns for Posterior Restorations - Clinical Notes
Several studies have been conducted by various hospitals and medical universities with a sample size of patients ranging between 30 to 100 where the patients were diagnosed with dental issues that required them to get crowns. All of these patients were then treated by using a Monolithic Zirconia crown for their posterior restoration requirement and the results of these studies have been published in all major websites. All of these studies were highly successful as Zirconia in the Monolithic form has performed exceptionally well for posterior restorations in all patients.
The study was done over a span of several weeks ranging upto an year or two and all patients in various studies had excellent results which were measured on the following factors
- Gingival Index
- Plaque Index
- Probing Depth
- Attrition of Antagonist Teeth
- Marginal Adaptation
- Colour match
- Gross Fracture
- Surface Texture
- Other Complications - Mechanical or biological
Mentioned above are some of the Periodontic factors and Survival factors of the teeth after the restoration was completed in the patient. All patients were mapped against these parameters. Apart from this, most studies also included external factors such as Age, Sex, type of teeth that needed the restoration, the condition of the antagonist teeth, region of restoration etc as well to map the test results in an optimum form. 93% to 100% was the range for acceptance of the monolithic crown in most kinds of patients where in most patients recorded ‘Excellent’ for almost all parameters for upto 96 weeks of the study.
In simple words, it can be concluded that the studies reveal the success and likelihood of the use of Monolithic crowns for posterior restorations as the rate of success is very high when compared to other restorative materials in the market. Also, the complications that may occur over the period of study were also very, very few when compared to other restorative materials. The studies all translate into the high likeliness of Monolithic zirconia crowns surviving successfully in the patient’s mouth with very little complications or failures.
Speaking from the patients' perspective, opting for a Monolithic Zirconia crown can be extremely helpful in cutting down on post operative risks which include fractures, infections in the gums or pulp of the tooth and excessive wear on the surrounding teeth due to the material. It is also a quick restorative technique as custom based crowns can be quickly prepared in-house if the machines are present or in a lab within a few hours. It cuts down on the time and money patients spend in getting teeth restorations done. Monolithic Zirconia crowns last much longer than its counterparts without any issues and have a very good success rate in maximum cases.
Given that Zirconia crowns are metal free restorations and their high biocompatibility, they are highly recommended by dentists worldwide for all patients and especially those who are ultra sensitive and need non-metal based restorations. When it comes to post-treatment maintenance and care, Zirconia crowns are still better than most other materials. They can help in better oral health and they are easy to care for. Zirconia crowns require high oral and dental hygiene in order to thrive and perform well and therefore all patients are advised to stick to a good oral hygiene routine to help the crown perform well for a long period of time.
With good after care and excellent oral health, monolithic zirconia crowns perform in an optimum manner with good durability, excellent resilience and low occurrences of fractures or infection in the patient's mouth.
