Dental emergencies seem to arise at the most inconvenient times. Some dental emergencies are serious while others are inconveniences at best. Anyone who has had a temporary crown or a permanent dental crown/onlay/porcelain veneer should be aware that it could eventually come off. They may be able to be placed back on, or may need to be completely replaced…But why does it happen?
How Do Dental Crowns Stay On Your Teeth?
Dental crowns are placed over your prepared tooth using a special adhesive cement. This cement has the ability to bond to both your natural tooth structure as well as the inner lining of the dental crown. Depending on the type of dental crown your dentist will use a different type of cement. The shape of the tooth is also important in keeping the crown on. The tooth is prepared by the dentist to be “retentive”, meaning that the shaping of the tooth itself helps to keep the crown on as well.
Why Would My Dental Crown Come Off?
–Tooth Decay. A tooth that has a dental crown needs to be kept clean through brushing, flossing and rinsing. Tooth decay can still occur at the margins of the dental crown, (where the crown edge ends and the tooth begins) and eventually make their way up and under the dental crown. If tooth decay does occur under a crown, it may need a new crown to be fabricated or if the tooth decay progresses far enough a root canal may be needed to salvage the tooth.
–Sticky, Chewy Foods. This can occur from continual use or just one time chewing a sticky piece of candy. Generally, over time these sticky, chewy foods can slowly break the cement seal and work a dental crown loose. If it is just pulled off from a candy, your dentist will examine both the tooth and the crown to ensure there is no tooth decay or damage to the tooth or crown. If all is well, your dentist may be able to simply recement the crown and you will be on your way.
–Crown Damage. A dental crown is a man made tooth shell that is capable of fracturing or breaking over time. Our teeth absorb extreme amounts of force on a daily basis. The metal or porcelain on a crown can wear through, chip, or fracture.
–Oral Habits. Yes, our habits can effect the longevity of a dental crown. Bad habits include teeth grinding (bruxism), clenching, nail biting, ice chewing, using teeth to open packages and bottles, chewing on pens, etc.. These forces will break porcelain, wear metal, and stress the adhesive bond causing the dental crown to loosen over time,.
–Small/Short Teeth. This can usually be overcome by your dentist “building” your tooth back up with dental resins but in some instances all of the teeth are shorter due to teeth grinding. The shortness is directly related to a decrease in retentiveness. This creates an issue over time, as the crown adhesive is working doubly hard to maintain its place on the tooth.
–Cement Breakdown. This can occur when the margin seal is broken causing the cement to leak out, or if a small amount of blood or saliva gets under the dental crown while cementing. If there is any moisture (saliva or blood) on the tooth upon cementation this can cause a weaker bond to develop for the cement. This will lead to a loosening of the crown over time. Simple fix in most cases is to just recement the dental crown back on either using a different cement or ensuring the area is clean and dry.
–Poor Fit. Sometimes a tooth is not prepared ideally, an impression of the tooth is distorted, the lab creates a poor fit to the tooth, or it is not completely seated on the tooth during cementation. When these issues occur, leakage of bacteria and saliva occur under the crown and loosen it.
As mentioned earlier, a dental crown coming off is a routine dental emergency but usually not a painful one. In many cases (if the dentist is unavailable), the patients try to temporarily recement their dental crown back on using fixodent (denture adhesive), toothpaste, or temporary dental cement from the local drug store. The best course of action is to see your dentist as soon as you can to ensure you do not experience any discomfort, do not swallow the dental crown, or permanently damage the tooth or crown.