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A dental crown is a tooth-shaped "cap" that is placed over a tooth – covering the tooth to restore its shape and size, strength, and/or to improve its appearance.
A dental crown may be needed in the following situations:
Ø To protect a weak tooth (for instance, from decay) from breaking or to hold together parts of a cracked tooth
Ø To restore an already broken tooth or a tooth that has been severely worn down
Ø To cover and support a tooth with a large filling when there isn't a lot of tooth left
Ø To hold a dental bridge in place
Ø To cover misshapened or severely discolored teeth
Ø To cover a dental implant
Permanent crowns can be made from all metal, porcelain-fused-to-metal, all resin, or all ceramic.
Metals used in crowns include gold alloy, other alloys (for example, palladium) or a base-metal alloy (for example, nickel or chromium). Metal crowns withstand biting and chewing forces well and probably last the longest in terms of wear down. The metallic color is the main drawback. Metal crowns are a good choice for out-of-sight molars.
Porcelain-fused-to-metal dental crowns can be color matched to your adjacent teeth (unlike the metallic crowns). However, more wearing to the opposing teeth occurs with this crown type compared with metal or resin crowns. The crown's porcelain portion can also chip or break off. However, sometimes the metal underlying the crown's porcelain can show through as a dark line, especially at the gum line and even more so if your gums recede. These crowns can be a good choice for front or back teeth.
All-resin dental crowns are less expensive than other crown types. However, they wear down over time and are more prone to fractures than porcelain-fused-to-metal crowns.
All-ceramic or all-porcelain dental crowns provide the best natural color match than any other crown type and may be more suitable for people with metal allergies. However, they are not as strong as porcelain-fused-to-metal crowns and they wear down opposing teeth a little more than metal or resin crowns. All-ceramic crowns are a good choice for front teeth.
Preparing a tooth for a crown usually requires two visits to the dentist -- the first step involves examining and preparing the tooth, the second visit involves placement of the permanent crown.
Onlays and 3/4 crowns are variations on the technique of dental crowns. The difference between these crowns and the crowns discussed previously is their coverage of the underlying tooth. The "traditional" crown covers the entire tooth; onlays and 3/4 crowns cover the underlying tooth to a lesser extent.
Ex.13. Find in the text English equivalents for the following words and word-combinations:
Сплав; розмір; різниця; форма; міцність; металокерамічна коронка; відновлювати; передні зуби; утримувати мостоподібний протез; біля лінії ясен; основний недолік; зуби, що змінили колір; зуби, що втратили форму; дешевший; з часом; зуби-антагоністи; постійна коронка; в меншій мірі, суцільнокерамічні коронки.
Ex.14. Answer the questions:
1. What is the function of dental crown? 2. In what cases may a dental crown be needed?
3. What materials are used for permanent crowns fabrication? 4. What is the main drawback of metal crowns? 5. What advantages have porcelain-fused-to-metal dental crowns? 6. What are disadvantages of porcelain-fused-to-metal dental crowns? 7. What teeth are porcelain-fused-to-metal dental crowns suitable for? 8. What types of dental crowns are more suitable for people with metal allergies? 9. How many visits does tooth preparing for a crown usually requires?
Ex.15. Complete the sentences:
1.A dental crown covers the tooth to _______ its shape and size, strength, and/or to improve its appearance. 2. A dental crown may be needed to hold a dental________ in place. 3. Porcelain-fused-to-metal dental crowns can be a good _______ for front or back teeth. 4. All-resin dental crowns are more prone to _________ than porcelain-fused-to-metal crowns. 5. Preparing a tooth for a crown usually requires ______ visits to the dentist. 6. Metal crowns are a good choice for ___________ molars.
Ex.16.Insert English equivalents of the Ukrainian words in brackets.Translate the abstract:
Your newly crowned (зуб) may be (чутливий) immediately (після) the (процедури) as the (анестезія) begins to wear off. (Якщо) the tooth that has been crowned still has a (нерв) in it, you (можете) experience some heat and cold sensitivity. Your (стоматолог) may recommend that you (чистити) your teeth with (зубною пастою) designed for sensitive teeth. (Біль) or sensitivity that occurs when you bite down (зазвичай) means that the (коронка) is too high on the tooth. If this is the case, (зателефонуйте) your dentist. He or she (зможе) easily fix this (проблему).
Ex.17. Insert the missing prepositions (of,on, from, between, around, at) where necessary. Translate the abstract into your native language:
On average, dental crowns last _______ 5 and 15 years. The life span ___ a crown depends __ the amount of "wear and tear" the crown is exposed to, how well you follow___ good oral hygiene practices, and your personal mouth-related habits (you should avoid ___ such habits as grinding or clenching your teeth, chewing ice, biting your fingernails, and using your teeth to open packaging).
While a crowned tooth does not require any special care, remember that simply because a tooth is crowned does not mean the underlying tooth is protected ____ decay or gum disease. Therefore, continue to follow good oral hygiene practices, including brushing your teeth ___ least twice a day and flossing once a day-especially ______ the crown area where the gum meets the tooth.
Ex.18. Insert the missing words given below:
Post-crown refers to a type of dental crown used on ________ teeth that require additional endodontic (root canal) _________. This single structure combines the crown with the post-core.
When the top of a tooth is lost due to _______ there may be very little for the crown to actually hold onto. To gain 'retention' as dentists call it, a post is placed ________ the tooth and acts as a seat for the crown. Post crowns have a shorter __________ than normal crowns as the roots may be brittle (ламкі) and weaker. Usually a post ______ is a better option than having the tooth extracted with a subsequent denture or _______ .
(decay ,therapy, lifespan, affected, inside, bridge, crown)
Ex.19. Read the text and entitle it. Write out unknown words. Make a plan of this text.
At the first visit in preparation for a crown, your dentist may take a few X-rays to check the roots of the tooth receiving the crown and surrounding bone.
Before the process of making your crown is begun, your dentist will anesthetize (numb) your tooth and the gum tissue around the tooth. Next, the tooth receiving the crown is filed down along the chewing surface and sides to make room for the crown. The amount removed depends on the type of crown used (for instance, all-metal crowns are thinner, requiring less tooth structure removal than all-porcelain or porcelain-fused-to-metal ones). If, on the other hand, a large area of the tooth is missing (due to decay or damage), your dentist will use filling material to "build up" the tooth to support the crown. After reshaping the tooth, your dentist will use impression paste to make an impression of the tooth to receive the crown. Impressions of the teeth above and below the tooth to receive the dental crown will also be made to make sure that the crown will not affect your bite.
The impressions are sent to a dental laboratory where the crown will be manufactured. The crown is usually returned to your dentist's office in 2 to 3 weeks. If your crown is made of porcelain, your dentist will also select the shade that most closely matches the color of the neighboring teeth. During this first office visit your dentist will make a temporary crown to cover and protect the prepared tooth while the crown is being made. Temporary crowns usually are made of acrylic and are held in place using a temporary cement.
At your second visit, your dentist will remove your temporary crown and check the fit and color of the permanent crown. If everything is acceptable, a local anesthetic will be used to numb the tooth and the new crown is permanently cemented in place.
Ex. 20. Ask the questions to have the following answers:
1.Before the process of making your crown is begun, your dentist will anesthetize your tooth and the gum tissue around the tooth. (When?)
2. The amount removed depends on the type of crown used. (What?)
3. The impressions are sent to a dental laboratory. (Where?)
4. During this first office visit your dentist will make a temporary crown to cover and protect the prepared tooth while the crown is being made. (Why?)
5. Your dentist may take a few X-rays to check the roots of the tooth receiving the crown and surrounding bone. (What …for?)
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