Prosthetic maintenance

Question 1

Define dental prosthesis

Answer 1

• An artificial replacement for one of more teeth and supporting structures
• It is important to maintain these prosthesis daily to ensure longevity and health of remaining tissues
• Patients with prosthesis are at a greater risk of dental caries and periodontal disease due to plaque retentive areas

Question 2

For removable partial dentures, list the materials

Answer 2

• Cobalt-chromium and all acrylic
• Cobalt-chromium dentures consist of a Co-Cr framework that is cast via the lost-wax casting technique. Artificial acrylic teeth are secured to the Co-Cr framework via pink acrylic.
• Acrylic dentures have no Co-Cr and the entire denture is made out of acrylic.
• In some older dentures the teeth may be made of porcelain
• All acrylic RPDs are usually a lot weaker than Co-Cr RPDs which are usually very strong (and more expensive)

Question 3

List the surfaces of a complete denture

Answer 3

• The components of a complete denture are the denture base, surfaces, and teeth
• The denture base is all parts of the complete denture excluding the acrylic teeth and the acrylic holding the teeth to the denture base
• The surfaces include the polished surfaces which are the external or outer surfaces that are in contact with the cheeks and lips and tongue
• The impression surfaces are the surfaces in contact with the edentulous ridges and hard palate of the upper arch and the edentulous ridges of the lower arch.
• The occlusal surface is the surface that makes contact with the opposing natural teeth or denture teeth.

Question 4

Describe crowns and bridgeworks in terms of the materials they are made of, and define a 3 unit bridge

Answer 4

• Another term for Crown and bridgework is a Fixed Prosthesis
• It is usually much more expensive than dentures.
• The basic principle for a crown is that a natural tooth is cut down so that an impression is taken and a crown is made that is permanently cemented onto the cut down natural tooth
• Crowns can be Ceramometal crowns
• A bridge is where one or more artificial teeth or pontics straddle the space between 2 or more natural teeth which have been cut down to allow crowns to be made
• 3 unit bridge: 2 crowns + 1 pontic

Question 5

List the types of bridges available and the materials they are made of

Answer 5

• Cantilever bridge: bridges that are designed when abutment teeth are prepared on only one side of the missing toothless gap. In such cases, the pontic is located outside the abutment teeth.
• Some crownand bridgework involves implants
• Materials: metals, ceramics, combination of both

Question 6

List the two types of relines

Answer 6

• Hard relines: with aryclic

* Soft relines: with soft liner such as viscogel or Lynal

Question 7

List the indications for hard denture relines and explain direct and indirect relining.

Answer 7

• Resorption of the residual ridge occurs throughout life after the teeth are extracted and even though a denture will have fitted well when first issued to the patient, most dentures will in time start to rock and become unstable.

There are 2 methods of relining:
• Direct reline procedure: Done directly in the patient’s mouth. Kooliner is an acrylic type material that can be used in the mouth. It is mixed and placed onto the tissue fitting or impression surface of the patient’s denture, and then gently inserted into the patient’s mouth. When the material has set (cured), the denture is removed and trimmed and polished

• Indirect reline procedure: where an impression is taken in the denture and the denture is relined in the laboratory. The impression material can be Polyvinylsiloxane (this slide), OR Light and/or heavy body Zinc Oxide –Eugenol. The material is mixed and placed on the impression surface of the upper denture and then inserted into the patients mouth. When the material is set, it is removed and sent to the lab which converts the impression surface recorded by the impression material into acrylic. The acrylic bonds chemically to the old dentures.

Question 8

Explain soft denture relines

Answer 8

• Soft relines are carried out in the same principleas hard denture relines.
• Most soft relines are done in the patient’s mouth and most dentists use Viscogel.
• The mixed material is placed on the impression surface of the denture to be relined and then placed in the patient’s mouth
• Viscogel hardens slowly over time and is usually very comfortable for the patient
• The major disadvantage with the use of this material is that it needs to be removed and replaced within a month or so of placement. So, it is only a temporary reline material

Question 9

List 3 indications of soft relines

Answer 9

• Can use the surface as an impression
• Allows tissues to heal
• For badly fitting dentures while new dentures are being constructed

Question 10

List the post operative instructions given to patients after a soft reline

Answer 10

• Remove excess with scissors or knife
• Don’t pull material as it may damage
• If food gets caught in lining, remove food debris with tweezers
• Don’t brush
• Tell them that a soft reline is not permanent
• Leave dentures out at night but leave tooth surface downwards in water

Question 11

Explain permanent soft relines

Answer 11

• Permanent soft relines are done by the technician in the prosthetic laboratory.
• They are technically difficult to do and cannot be adjusted with a handpiece and bur.
• They are only rarely done these days

Question 12

List the 6 things you would see in dentures of patients with poor denture hygiene

Answer 12

• Mucins (mucopolysaccharides and glycoproteins) and food debris
• Denture pellicle (salivary glycoproteins) and denture biofilm/ plaque
• Bacteria or candida albicans
• Matrix for calculus formation and stain formation. Can contribute to breath malodour
• Denture calculus
• Stains

Question 13

Describe how to care for dentures during intra-oral procedures

Answer 13

• Place denture in a disposable cup and rinse in water. Clean it with an ultrasonic cleaner. Leave the dentures in a disposable cup in antimicrobial solution
• Place cup in a safe place to avoid knocking over
• At the end of the appointment, remember to rinse denture and hand back to patient
• Any formof fluoride application should be done with the dentures out of the mouth.
• Note that strong fluoride solutions can lead to discoloration of some denture components.

Question 14

Explain the provision of appropriate in-office care for fixed prosthesis and the types of fluoride treatment materials you would use

Answer 14

• Remove loose debris
• Use a toothbrush with a non-abrasive fluoride containing dentifrice to remove biofilm. This will prevent abrasion of prosthesis surfaces and any areas of exposed root surfaces.
• Acidulated fluoride preparations are contraindicated for prosthetics as they can damage them
• Give interdental hygiene instructions

Question 15

Explain the in-office care for patients with a removable partial denture

Answer 15

• Remove it, place in a cup and run it under running water

* Place in a cleaning solution in a bad in an ultrasonic cleaner

Question 16

Explain at home care procedures for removable partial prosthesis

Answer 16

• Rinse then brush it with a denture brush. Partially fill the sink with water and brush the denture over the water so if dropped, the denture doesn’t get damaged. Do not use an electric toothbrush to clean a denture. A clasp brush may be used to clean the inner surfaces of the clasps or retainers

Question 17

Recognise when there is a need for referral to dental officer for repair and adjustment (4)

Answer 17

• Broken denture
• Ill fitting denture
• Poor retention
• Bite is poor/ defective occlusion

Question 18

Explain how ill-fitting dentures are assessed by the dentist

Answer 18

• For ill-fitting dentures or where patients experience sore spots, the dentist can use disclosing pastes (e.g. Fit-checker) to identify the sore spot or ill-fitting area of the denture.
• Fit-checker comes as 2 low viscosity pastes that are mixed with a small spatula and a thin layer is smeared over the area that the patient is complaining about.
• Then the denture is placed in the mouth.
The principle is that where there is an over-extension in the acrylic, the paste will be pushed away and the offending acrylic will show through. This offending region can then be adjusted by the dentist

Question 19

Describe the appropriate home care regime for patients with complete and/or partial dentures, including the precautions the patient should take

Answer 19

• Do not continuously wear the prosthesis as this can damage the oral mucosa and lead to denture stomatitis of oral candidiasis. Leave it out at night.
• Clean dentures well, have good oral hygiene, leave them out at night. If infection occurs, then topical antifungals can be used.

Question 20

List the procedures for cleaning complete dentures and the types of denture cleaning solutions

Answer 20

• Rinse thoroughly
• Remove any denture adhesives with light brushing
• Can use denture cleaning tablets. The bubbling effect of released oxygen loosens debris. Only 10 -15 minutes needed. They can corrode metal parts.
• Sodium hypochlorite (disinfectant) is good as it will kill most micro-organisms, but not for cobalt chromium dentures as it can blacken them
• Dilute acids can be used (5% HCl) but this can cause corrosion of metal components
• Denture pastes such as abrasive calcium carbonate can degrade the acrylic resin denture base and teeth
• Household detergents can be used. Just don’t use scouring powders.
• The denture brush has two surfaces. 1 is rounded for inner impression surface and the other one is for occlusal surfaces.
• Do not apply excessive pressure with abrasive pastes as this can damage the denture, alter the appearance of the denture and create plaque traps.

Question 21

List the additional care instructions for the care of acrylic resin

Answer 21

• In cold water when not in mouth. Do not place in hot or boiling water as this may distort the denture base. Do not scrape with sharp instruments
• Soft lining materials, whether temporary or permanent, should be washed with cold water and soft cloths/ soft brushes.
• Leave denture overnight in water with teeth facing down to avoid distorting the soft lining.
• Denture adhesives such as Polident can be used as a temporary solution until the denture can be relined.