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Whangarei Dental Crowns



What is a crown?

A dental crown is a tooth-shaped “cap” that is placed over a prepared tooth to restore its shape and size. It is used to provide strength to the tooth or to improve its appearance.

The crown procedure involves preparing the tooth to accept a crown, taking an impression for the lab to produce the crown, making and placing a temporary crown while the lab makes the permanent crown and, finally, to cement the fabricated crown, usually at a subsequent appointment.

Some crowns are “milled” at the dentist office thus eliminating the need for a follow-up appointment to have the crown cemented. The dentist will prepare the tooth and take a digital impression, which will instruct a milling machine to carve out a crown from a block of tooth coloured material. The milled crown will be placed on the tooth after about 45 minutes of milling.

This sounds great and, in time, will be the future of dentistry. However, milled crowns must be considerably thicker than laboratory made crowns and thus require more tooth to be remove during the preparation stage. Currently, Kowhai Dental does not use the one-visit type of milled crown due to the high failure rate and the large amount of tooth that must be removed for these milled crowns. Material and techniques are always improving and we may include milled crowns in the future as advancements meet our criteria.

Why do I need a crown instead of a filling?

A crown is required to restore a tooth when there has been a large portion the tooth lost to decay, previous fillings or a fracture. A filling will fill a space in a tooth formed by decay or a small chip. A filling requires sufficient remaining tooth structure to not only hold the filling in place, but to allow function of the tooth with the remaining tooth structure. A filling has no inherent strength and is intended to occupy the space left behind after decay removal. An affected tooth must have sufficient remaining tooth structure to be successful.

Crowns are made from materials that are strong enough to distribute biting forces to the compromised or fractured tooth. Crowns are made from metal, porcelain, zirconium or a combination of these materials. The type of crown used is dependent on the circumstances presented to restore the tooth.

How should I take care of my temporary crown?

A temporary crown is placed on a tooth during a crown procedure while the permanent crown is made in the dental laboratory. It is placed to protect the tooth, as well as maintain the space between adjacent teeth. If a temporary crown comes off, the tooth will be sensitive (unless it has had a root canal) and the space between the adjacent teeth will change as they shift. It is important to keep a temporary crown I’m place until the permanent crown is placed.

Temporary crowns are just that - temporary. Special care must be taken while wearing a temporary crown in order to protect it. Avoid sticky foods like caramels and chewing gum as these can pull the temporary crown off. Avoid really hard foods like nuts, crackling and raw vegetables as those types of foods can break a temporary crown.

Flossing around a temporary crown requires a slight modification to the technique. Instead of pulling the floss back out the way it came in, let go of one end of the floss and pull out the free end so the floss will not grab the temporary crown and pull it off.

If your temporary crown comes off, place it back over the tooth as best you can and see your dentist as soon as possible to have it recemented. Even a few hours without a temporary crown can allow teeth to shift thus making placement of the permanent crown more difficult. You can use petroleum jelly or toothpaste in the temporary crown to help hold it in place until you can get it recemented.

How long will a crown last?

A crown is intended to last forever. However, the useful life of a crown is dependant on the health of the tooth it is on. Crowns restore the lost part of a tooth. The remaining part of the tooth is still susceptible to disease. It is imperative to maintain a crowned tooth with proper maintenance.

Crowns made from porcelain materials can fracture, just like a tooth. Sometimes a fractured porcelain crown can be repaired but it is best to have a fractured crown replaced with a stronger type of crown.

What factors determine a crown’s lifespan?

Crowns are meant to last a lifetime with proper maintenance. Under most circumstances, the life span of a crown depends on the tooth supporting the crown. The crown itself will not deteriorate over time.

If a crown is placed in a high stress area, meaning it’s the only tooth that bites against another tooth, then the wear and tear on that tooth supporting the crown will increase, thus shortening the tooth’s life.

What is that black line at the gumline on a crowned tooth?

A dark line next to the gum line of your crown is usually just the metal of a porcelain fused to metal crown showing through at the edge. This can occur as the gums recede with age or gum problems. Although unsightly, the dark line is not a problem with the crown, other than cosmetic.

Sometimes the dark line is actually the root of the tooth showing as the gums recede. This is not an issue with the crown but should be checked to ensure gum problems are not present.

Are there alternatives to crowns?

A crown is made from extremely durable materials which are intended to replace missing parts of a tooth critical to function. In some cases, a partial crown can be used to restore the compromised tooth. A partial crown is also known as an Onlay, where the biting tips of back teeth are replaced by a partial crown which is “laid over” the mostly intact tooth. Onlay crowns are more conservative than a conventional crown where very little of the tooth is removed prior to placement.

Since crowns are expensive, you might get away with a large filling for a while. This option must be considered temporary as the filling material will not last that long.

Why is my crown sensitive?

It is normal for a newly placed crown to be sensitive to heat or cold for a week or two after placement. This is due to the curing process of the material used to cement the crown in place.

All metal crowns can be sensitive for a while longer (up to 6 months) due to the thermal conduction of the metal. Over time, the tooth will build up a layer of new tooth structure inside the tooth which will insulate the nerve from the metal used to make the crown.

If sensitivity persists, the crown could be slightly out of adjustment for your bite. It only takes a fraction of a millimetre to put a tooth out of alignment. If the crowned tooth was cracked or the lost part of the tooth was very close to the nerve of the tooth, the nerve may be compromised and require a root canal to alleviate symptoms. See your dentist if your crown is sensitive for a prolonged period of time.

Which is the best crown to have?

The best crown to have depends on the desired outcome. Some crowns are placed for aesthetic reasons while others are place to restore normal function.

All-metal crowns are actually the best type of crown for back teeth. Metal crowns, either gold or other metals, required very little of the tooth to be removed during preparation. Metal crowns do not chip or fracture. However, most people do not like the look of metal crowns and are willing to compromise durability for aesthetics.

Porcelain fused to metal crowns are the most popular type of crown. They are relatively strong and provide reasonable aesthetics. They can chip when abused and do require a substantial amount of tooth removal during preparation.

All-porcelain crowns are the choice for cosmetic dentistry. Although they are not as strong as porcelain fused to metal, they are certainly the best looking. All-porcelain crowns are mostly used on front teeth where aesthetic demand is the highest.

Zirconium crowns are relatively new and show a lot of promise in dentistry. They are strong and require minimal preparation for placement. However, zirconium crowns are typically all one colour and do stand out from surrounding teeth that naturally have a colour gradient, light at the tip and darker near the gum line.

Which crown is the most natural looking?

The most natural looking crown is an all-porcelain crown. All-porcelain crowns reflect light very similarly to a natural tooth, thus giving it the best aesthetic value.

All-porcelain crowns can be used when proper circumstances exist. First, the tooth being crowned must not be too discoloured as the porcelain cannot mask very dark teeth. For dark teeth, a porcelain fused to metal or zirconium crown must be used.

All-porcelain crowns are not very strong and, therefore, cannot be used when there are excessive strains on the tooth to be crowned. They also require a significant portion of the tooth to be removed for placement.

Can a crown be repaired?

If a crown is chipped, sometimes the chipped porcelain can be replaced with a white (composite) filling. The filling will never be as strong as the original crown but may be worth attempting as the only alternative is to replace the crown.

Chipped crowns on back teeth can rarely be repaired successfully and therefore require replacement.