Indications and Contraindications of a Dental Crown


Crown and bridges are being served to dental patients routinely as its manufacturing has become fast, readily available. It is a dependable option. 

Although, the crown & bridge is generally considered very safe and it is associated with a low incidence of complications, there are some precautions that need to be considered.

Indications of a Dental Crown

1. Cases where the tooth has been damaged beyond repair: If the patient has a large cavity that cannot be fixed with a filling, but the dentist determines that the dentine and pulp are in good condition then he will recommend that a crown be placed to save the tooth.

2. When large fillings need replacing: Fillings need replacing every so often, your dentist may recommend installing a crown instead of re-filling the tooth, the reasons for this are the crown is a long term solution and it is esthetically more pleasing.

3. Fractured tooth: In the case that a tooth gets fractured due to a dental trauma or progressive tooth decay, it is highly recommended that a procedure known as post and core be performed. The post and core procedure simply put, is the placement of an implant without extracting the root. In this procedure a small rod is inserted into the root of the affected tooth, this rod will slightly protrude and the core or crown will be attached to it. For this procedure, the tooth in question will require a root canal before the post and core can be done.

4. Enhanced esthetics: For patients who have discolored or uneven teeth, or even for those who have large fillings the use of crowns can greatly improve the esthetics of their smile.

5. To cover dental implants: When a patient has lost a tooth for any reason, and an implant is required to maintain proper function, the implant will be covered by a porcelain crown that has been made to match your existing teeth.

6. To affix dental bridges or dentures: A dental bridge is a prosthetic used to replace missing teeth, these bridges are permanently adjoined to either dental implants or crowned teeth. The dental crowns are used to hold the prosthetic in place.

7. Dental erosion: The tooth enamel can be dissolved by the acidity in foods; when the enamel has been compromised, porcelain crowns are the ideal solution to prevent the progression of tooth decay to the dentine and pulp. Other forms of erosion include tooth abrasion which occurs from improper uses of toothbrushes, brushing too hard, improper flossing or biting on hard foods. And it also includes conditions where natural tooth to tooth friction happens, as in the case of involuntary grinding known as bruxism.

Contraindications

As with any medical procedure, it is possible that complications can arise. Among the risk factors and contraindications of dental crown procedures, we can list the following:

1. Illnesses where the use of anesthesia is contraindicated: These may include severe heart disease, recent strokes and allergic reactions to anesthesia.

2. The use of crowns is not indicated in cases where the problem can be solved with a filling.

3. There is a risk that during the preparation phase, the tooth’s surface can become too thin or be perforated by an instrument.

4. During the preparation procedure, nerve damage can occur, if this should happen, it will be necessary to perform a root canal.

5. Bite misalignment, although in most cases dental crowns can correct TMJ (temporomandibular joint), if the crown is incorrectly placed, it can exacerbate the problem in some patients. Once the dental crown is in place, your dentist should check the fit taking into account the surrounding teeth as well as the whole bite.

6. Allergic reactions to one or more of the materials. Dental crowns can be made from a variety of materials, choosing the right material will minimize the chances of an allergic reaction.

7. Infections, if the dental crown is not properly sealed or if the damaged tissue was not properly removed, the area might become infected.

 

 


Properties of Dental Materials- Terminology

You must know the properties of the materials used in dentistry to understand its function and how and why it works in oral cavity. It also helps in manipulating it. The main properties you should know about are following:

  • Stress
  • Strain
  • Elasticity Modulus
  • Elastic Limit
  • Thermal Expansion
  • Hygroscopic Expansion
  • Setting Expansion
To read the entire lecture (in premium Iridium course), click at the link HERE.

Oral Hygiene

General information



Regular oral hygiene by mechanical brushing and cleaning between the teeth removes soft dental plaque. When dental plaque becomes mineralised (calculus), it must be removed by a dental practitioner. Dental plaque and calculus can cause periodontal disease (eg gingivitis) and dental caries.

Frequent exposure to dietary sugar and carbohydrates leads to an increase in the risk of dental caries. Avoid sucrose in sticky forms and limit other sugars (eg acidic drinks) and carbohydrates as snacks between meals.

Avoid drinks other than water at bedtime after brushing teeth (including milk, formula and expressed breastmilk)—saliva flow diminishes during sleep and the sugar from the drink remains on the teeth overnight. This is a common cause of dental caries in children and the elderly.

Interdental cleaning

Interdental cleaning using floss or interdental brushes is recommended once each day before brushing the teeth. Brushing teeth with a toothbrush does not remove plaque from between the teeth or below the gum line.

Dental floss can be used to wipe the interdental tooth surface to remove plaque (back and forth, then up and down several times on each tooth surface). Manual dental floss, floss-holding devices or automated flossing devices are available—the choice is based on personal preference or level of dexterity.

Interdental brushes areas effective as dental floss in plaque removal, and often more effective for debris removal. They require less dexterity than dental floss. Interdental brushes are particularly useful in patients with gum recession or disease, where the spaces between the teeth are larger.

Interdental wood sticks can remove food particles, but do not effectively remove plaque.

Water jets do not effectively remove plaque.

Tooth and tongue cleaning

Soft-bristle toothbrushes are recommended; hard-bristle toothbrushes are not more effective and can damage the gums and the softer root surface. Children younger than 6 years should use a children’s toothbrush. Powered toothbrushes with a rotation oscillation action are slightly more effective at plaque removal than manual brushes. Powered toothbrushes are useful for people with dexterity or disability problems, and for carers. Toothbrushes should be replaced once damaged or when the bristles become deformed.

Advise patients to use a fluoride-containing toothpaste; for recommended concentrations of fluoride in toothpaste. Toothpastes that do not contain fluoride provide little protection against dental caries. Toothpastes also contain other additives (eg abrasives, detergents, antibacterial, bleaches, remineralising agents).

Toothpastes that do not contain fluoride provide little protection against dental caries.

Advise patients to brush teeth for 2 minutes, twice each day with fluoride toothpaste. Toothpaste should be spat out and not swallowed to minimise fluoride ingestion; the mouth should not be rinsed to allow increased uptake of fluoride from the saliva.

Advise patients to brush or gently scrape the tongue, but not to brush or massage the gums.

Mouthwash

Mouthwash is usually not required as part of a standard oral hygiene routine, provided mechanical cleaning (toothbrushing, interdental cleaning) is performed properly. Mouthwash should not be used as substitute for proper mechanical teeth cleaning.

Fluoride-containing mouthwashes can be used as an additional source of fluoride for people at high risk of dental caries on the recommendation of a dentist.

Mouthwash that inhibits plaque formation (eg chlorhexidine) can be used for a short duration in addition to mechanical tooth cleaning, usually when pain associated with periodontal disease restricts mechanical cleaning (see Management of necrotising gingivitis and Gingivitis).

Alcohol-containing mouthwashes may be associated with oral cancer and are not recommended. See here for further information on mouthwashes.

Specialised oral hygiene

People with dental implants, bridges, crowns that are joined together, and orthodontic brackets should follow the oral hygiene advice from their dentist.

Denture hygiene

Dentures should be regularly cleaned twice a day to remove food particles and plaque. Advise patients to remove dentures from the mouth and clean them with warm water, mild soap and a toothbrush, denture brush or soft nail brush. Avoid cleaning dentures with hot water, toothpaste, kitchen detergents, laundry bleaches, methylated spirits, antiseptics or abrasives (unless instructed to by a dental practitioner). Patients should clean their gums and remaining teeth with a soft toothbrush and toothpaste.

Advise patients to place dentures in a dry environment overnight after cleaning them. Traditionally, it was recommended that dentures were kept in liquid overnight. However, allowing the cleaned denture to dry out at night is more effective for reducing yeast colonisation and plaque accumulation, compared with both denture cleansers and water. Although repeated cycles of hydration and dehydration can change the shape of the denture, these changes are small and not clinically significant.

Dentures should be cleaned then placed in a dry environment at night. If there is a build-up of hard deposits (tartar, calculus), dentures can be soaked overnight in a solution of white vinegar (diluted 1:4), then cleaned as usual. Advise patients to see their dentist for professional cleaning if hard deposits cannot be removed.

Denture-associated erythematous stomatitis is prevented by regular cleaning of the dentures and storing them in a dry environment overnight. Advise patients with denture-associated erythematous stomatitis to optimise denture hygiene—it can take 1 month for symptoms to improve; see Oral candidiasis and Candida-associated lesions for further information.








Ref: Therapeutic Guidelines Limited 2019 (www.tg.org.au)

Dental Anatomy and Terminology

Anatomy of the tooth and surrounding tissues

Enamel: This is the hard, calcified substance that makes the surface of a crown of a tooth.

Dentin: This is the calcified tissue that forms the major part of a tooth. In the crown of the tooth, the dentine is covered by enamel. The pulp
chamber of the tooth is surrounded by dentine.

Pulp: This is the organ at the centre of a tooth that contains blood vessels, connective and neural tissue, and cells that produce dentine-odontoblast. Blood vessels and neural tissue enter the tooth from the apex of the root.

Gingiva: This is the marginal part of the gum that surrounds the tooth where it emerges from the deeper, supporting tissues.

Periodontal ligament: This is the ligament that connects a tooth, by its root, to the supporting bone.

Cementum: This is the calcified tissue on the surface of the root of a tooth, which provides attachment for the periodontal ligament.

Fissure: It is a naturally occurring crevice in the enamel.

Crown: This is the part of the tooth that is visible and is above the gingival margin.

Root: This is the part of the tooth below the gingival margin; it is connected through cementum on its surface and the fibres of the periodontal ligament to the supporting bone.


Dental numbering system

There are numerous dental numbering systems to identify teeth and their maturity. The most commonly used system in Australia is the Federation Dentaire Internationale (FDI) system (see Figures). When communicating with a dentist, identify which numbering system is being used.

The FDI numbering system divides the mouth into quadrants. The first number indicates the quadrant and whether it is a primary or secondary tooth. The second number indicates the tooth; tooth numbering begins at the central incisor and counts backward to the molars.

Using the FDI numbering system, for adults, the quadrants are numbered as:

1. patient’s upper right is quadrant 1 
2. patient’s upper left is quadrant 2 
3. patient’s lower left is quadrant 3 
4. patient’s lower right is quadrant 4




For primary teeth in children, the quadrants are numbered as:

1. patient’s upper right is quadrant 5 
2. patient’s upper left is quadrant 6 
3. patient’s lower left is quadrant 7 
4. patient’s lower right is quadrant 8




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Ref: Therapeutic Guidelines 2019

Domains of Practice in Australian Dentistry

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Domain 6. Patient Care 

 6.1 Clinical Information Gathering  

It covers the collection and recording of information that is necessary and relevant. 

As an Australian dentist you must be able to:   

 

1. obtain and record a relevant history of the patient’s medical, social and oral health status  

2. perform an examination for health, disease and abnormalities of the dentition, mouth and associated structures  

3. select necessary clinical, pathology and other diagnostic procedures and interpret results  

4. take radiographs relevant to dental practice  

5. evaluate individual patient risk factors for oral disease 

6. maintain accurate, consistent, legible and contemporaneous records of patient management and protect patient privacy  

 

6.2 Diagnosis and Management Planning  

  • It covers the identification of disease or abnormalities that require treatment or investigation As an Australian dentist you must be able to:   

  • 1. recognise health as it relates to the individual  

  • 2. diagnose disease or abnormalities of the dentition, mouth and associated structures and identify conditions which require management  

  • 3. determine the impact of risk factors, systemic disease and medications on oral health and treatment planning   

  • 4. formulate and record a comprehensive, patient-centred, evidence-based oral health treatment plan  

  • 5. determine when and how to refer patients to the appropriate health professional  

  • 6. obtain and record patient informed consent and financial consent for treatment  

 

6.3 Clinical Treatment and Evaluation  

It covers the provision of evidence-based patient-centred care. 

As an Australian dentist you must be able to:    

1. apply the principles of disease and trauma prevention and early intervention in the management of the dentition, mouth and associated structures  

2. apply the principles of behaviour management  

3. manage a patient’s anxiety and pain related to the dentition, mouth and associated structures  

4. manage surgical and non-surgical treatment of diseases and conditions of the periodontium and supporting tissues of the teeth or their replacements  

5. manage surgical and non-surgical treatment of pulp and periapical diseases and conditions with endodontic treatment  

6. manage the loss of tooth structure by restoring the dentition with direct and indirect restorations  

7. utilise patient removable prostheses to rehabilitate, restore appearance and function, prevent injury and stabilise the occlusion 

8. utilise fixed prostheses to rehabilitate, restore appearance and function and stabilise the occlusion  

9. manage oral conditions, pathology and medically related disorders and diseases associated with the dentition, mouth and associated structures  

10. manage skeletal and dental occlusal discrepancies  

11. manage the removal of teeth and oral surgical procedures  

12. administer, apply and/or prescribe pharmaceutical agents  

13. evaluate and monitor the progress of treatment and oral health outcomes  

14. manage dental emergencies. 

15. manage medical emergencies.