A Comprehensive Review of the Retention and Clinical Performance of Zirconia Crowns
Dental Crowns serve as the number one solution to most kinds of dental issues around the world. Many dentists have researched and concluded that dental crowns are reliable and durable solutions to most of the dental issues that include chipping of the natural tooth, fractures, misshapen or discoloured tooth, decay or any other kinds of issues that affect the teeth. Much research has been done both in-vivo and in vitro of lab studies on patients that has revealed some of the major findings on the type of material that has been used to make the dental crown and the retention and its performance with respect to strength, durability and other health issues. These researches have been able to shed light over the favourable materials that can be used to make the dental crowns and their pros and cons for the patients. It has also provided dentists and dental patients a wide variety of material to choose from for their dental crowns. This can be differentiated on the basis of many factors such as aesthetics, biocompatibility, constituent elements, restoration process and time, budget, durability over the years, maintenance etc.
Zirconia Crowns | Introduction
Zirconia is a new age material that has been recently used by most dentists to prepare dental crowns. More and more dentists are now suggesting zirconia dental crowns for their amazing attributes that are very patient friendly. Although, it is to be noted that Zirconia has been in the dental world for many years now. The first known use of Zirconia for dental crown was in the early 1960’s. The material was itself hard to manage and carve and could not be used efficiently by dentists. Thanks to the development in technology, CAD and CAM machines can now be used to digitally provide the exact shape and size of the dental crown as per the dentist’s requirement.Zirconia crowns were introduced back again by 2010 and this time, more and more dentists were able to work with them.
Not to mention the excellent aesthetics provided by the Zirconia ceramic crown, where the zirconia crown has a partial veneer on top of it made from ceramic for anterior restorations making them almost unrecognisable from the rest of the natural teeth. Zirconia is also known to be the strongest material up until today for dental crown material making them top notch contestants for strength and durability. They have a very good lifespan and require almost no maintenance up until 6 years or so. Their general life can last several years post that as well based on oral hygiene and general habits of the patient.
Zirconia crowns are also very biocompatible and have a high tolerance to thermal exposure. Patients who cannot go in for metal based restorations can easily go for zirconia crowns as they cause almost no allergies in even the most sensitive of patients. Thanks to partly man made element nature, the material is very stable and is highly fracture resistant as well. This makes them an excellent option for those who have bruxism, heavy chewers and those with a heavy bite force.
Zirconia crown price is somewhat more expensive than the other types of crowns. Owing to its high and fine qualities, zirconia crowns cost slightly more than all ceramic or porcelain crowns. They however cost less than gold and titanium based crowns that some patients prefer. The cost of Zirconia dental crown also depends on what location the patient has referred themselves to as many countries have varying zirconia crown cost based on availability and demand.
Retention and Clinical Performance of Zirconia Crowns
Zirconia Crowns are known for their favourable attributes and is a clear preference over other materials for a variety of reasons including but not limited to strength, durability, biocompatibility, Aesthetic appearance and quick restoration process. There are some factors that set Zirconia crowns back when compared to its competitors such as high chair side restoration time, wear and tear on other teeth especially the opposing teeth, Zirconia crown price over other materials and chipping of the veneering. Below is a detailed review of the Clinical performance of Zirconia Crown as studied by researchers:
1.Strength
It was noticed in several in vivo studies conducted by dental researchers that Zirconia was indeed the strongest dental material that can be used to make dental crowns. This was one of the most stable elements that can be easily matched with the natural colour of the teeth to provide both anterior and posterior restorations. Chipping was one of the primary concerns amongst most studies after about 3 years of usage but it was found primarily on Zirconia with Porcelain veneers. Also, patients with single tooth restorations and the combination of many other factors such as occlusal load thermal expansion. The overpressing technique was then invented to combat this issue where a ceramic layer is pressed on top of the zirconia and this has led to a significant drop in chipping instances in patients.
2.Durability
As per studies conducted on patients who had Zirconia based restorations, it was found that as many as 93% of patients had no incidents because of their Zirconia dental crowns and as many as 90% of patients had 0 incidents in their zirconia tooth crowns which is one of the best testaments to a dental material that has lasted in the patient's mouth with no incidents. 24% of patients had no incidents up until 6 years of usage of Zirconia dental crowns which is the highest when compared to other materials such as all ceramic crowns which were at 8%. This states the fact that the retention and clinical performance of Zirconia crowns are superior to the other types of crowns.
3.Fracture Resistance
Many clinical studies have proved the fact that Zirconia and its various varieties such as ZrSio4, Zirconia-TZP etc have been revealed to have lasted as many as 1.5 million chewing cycles (at around 5 years) regardless of variables such as cementing techniques and type. Zirconia is known for its high fracture resistant qualities at mean temperatures and with mean occlusal loads of 1700N, meaning that they were sufficiently able to survive most kinds of patient habits without any problems for about 5 years and more. This proves the fact that the retention of Zirconia crowns is higher than its counterparts such as all ceramic and PFM (Porcelain Fused to Metal) Crowns.
4.Biocompatibility
Zirconia was found to be the most biocompatible material for dental crowns under conditions such as Low corrosion potential, aesthetic appeal, thermal conductivity, high flexural strength and fracture resistance. It is one of the best choices for those who have sensitivity to metal based restorations which leaves them with all ceramic crowns and Zirconia crowns, and the pros of zirconia crowns outweigh ceramic crowns anyday. Most importantly, the bacterial adhesion to zirconia crowns was significantly lower than any other type of material making it perfect for those who are susceptible to caries and decay due to oral and tooth structure.
Zirconia crowns do require some level of oral hygiene and require scaling from time to time to help upkeep the appearance and lower any chances of plaque build up. This is most important for adults who are unable to take care of themselves and therefore may not be able to clean their teeth regularly.
Conclusion
Based on several in vivo and in vitro studies done by dental researchers, it has been established that Zirconia crowns have a very high success rate when compared to other dental materials in this category. There are certain levels of differences in retention and performance which is attributed to factors such as the type of Zirconia used, the luting agent, the cement thickness, the inevitable chemical content of oral fluids and the variation in patient habits such as bite force and bruxism. There are several different types of studies that have taken into account all of these variables in different circumstances and still, Zirconia crowns have been recognised as the most successful in terms of retention and clinical performance.
