Quite commonly people who undergo dental treatments to get crowns fixed have unrealistic hopes regarding their permanence and lifespan. So, they get shocked when the crown falls out unexpectedly. When this happens to you, the most important thing is to remain cool, place the crown in a packet and schedule an appointment with your dentist as soon as possible.Do not waste Time Re-fixingthe crown is an emergency because food particles are free to enter the margins ofthe prepared tooth and become grounds for development of microbes and hence maycause re-infection. Therefore, the issue should be addressed as quickly as possible. 

Tooth decay- Youhave to understand the fact that although crowns and implants are made from non-corrosive metals and therefore not prone to decay, the tooth under them may get decayed if correct oral care routine– brushing, flossing and undergoing deep cleaning at the dentists’ office regularly – is not followed. You may develop gum disease or even periodontal disease after few years. When the hard tissue decays, it weakens the cement with which the crown was fixed and a forceful bite will cause it to pop out. The most common area for the decay to develop is at the gumline.  Depending on the severity of the decay your dentist may or may not be able to re-fix your old crown and then a filling will be required; a new crown may need to be made.

Hard foods- Dentists constantly advise patients with crowns to avoid biting into hard food substances.It doesn’t matter how resistant the material of the crown is, if you continue to put high biting pressure on the crown, for instance chewing on pens, opening caps of the cold drinks or grinding and clenching your teeth, you will ultimately crack the surface of the crown and loosen the crown.  

Sticky eatables-The same logic is applicable for sticky substances. For example, substances like candiesor caramel become stuck to the crowns surface and, when you try to detach it with your tongue or by chewing, you also make the crown loose. The bonding between the crown and the tooth gets altered and your crown comes out. In these cases, it is usually easy to paste the crown back on its position with cement.

The foundation of the crown loses mass-Tooth mass can be lost sometimes in trauma, fractures, periodontal disease in later stages, jaw misalignment etc. The crown was prepared according to the jaw bone alignment and therefore crown becomes unable when the bone structure changes its shape. Using mouthguards during sports and treating periodontal disease before it worsens are some of the best ways to prevent the crown dislodgement.

The bonding cement of the crown weakens overtime-Crowns are fabricated from very strong materials to tolerate biting and eatingpressures for years.  But because of the continuous load over crown formany years, the bonding agent of the crown can weaken over time making thecrown loose.  In these cases too, the crown can be easily re-fixed.

Tooth structure below the crown is very less-Sometimesthe tooth foundation below the crown is very less and is not enough to hold thecrown firmly. This is most common in back teeth. If your crown is comingout again and again, better option is to go for crown lengthening procedure to increase the surface area oftooth prepared for the crown.

The crown’s upper layer broke. In some cases of crowns,especially in porcelain fused to metal crowns, due to forceful biting, the crown’s outer layer can chip off from the metal coping after many years of usage. Depending upon the location of porcelain chip off, crown may get loose and you may need a new crown to maintain integrity with adjacent teeth. 

Don’ts 

A horrible idea would be trying to place the crown back on the tooth yourself,because in the absence of high-quality cement it would simply fall out again. You may be lucky first time but you may swallow it next time if it comes out.Though swallowing crown is not a problem in majority of cases as it is excreted through stools but it may poses a problem if it enters your wind pipe and stuck.You can also purchase temporary bonding agents from the local chemist, but it’s not good to try this activity if you are not sure if the tooth is broken or just the crown has come out. Remember to avoid chewing any solid food on the side where the crown is dislodged, so that you don’t damage the tooth even further.