Complete Dentures - Retention and Stability

Question 1

What problems can arise for patients from loss of dentition?

Answer 1

Loss of function (chewing, talking), aesthetics, self-esteem (career and relationships)

Loss of chewing function - unable to eat favourite foods as when they eat, denture can dislodge.
Change in speech - they can develop a slight lisp due to denture dislodging while talking.
Unable to play wind instruments - blowing hard on the instrument can lead to loss of border seal and denture can dislodge. Playing without denture can make it difficult to place instrument onto the lips and blow.
Dentures can damage delicate mucosa resulting in ulceration which can be painful

Question 2

What happens to the alveolar bone in an edentulous patient?

What problems can this cause?

Can you predict this?

Answer 2

Alveolar atrophy. Calcium gets redistributed and so there’s a loss of alveolar bone height, particularly in the first year after extraction. This bone height can be lost more and more over the years, till there’s very little ridge height left, which can cause problems for denture retention and stability.

If it gets really thin, it could cause pathological fracture of the jaw.

It’s impossible to predict how much bone will be lost before extraction.

Question 3

What things may a patient wearing a denture come and complain of?

Answer 3

Pain/discomfort, looseness, aesthetics

Question 4

What questions should you ask about their current denture that is causing the problems?

Answer 4

Since when, how long for, and at what time.
E.g. for pain, how long has it been hurting for, and is it when they put the denture in and it goes away, or is it worse with time (may be due to not enough saliva lubricating denture which can lead to denture rubbing on mucosa).
For looseness, is it all the time or just when chewing?

Question 5

What other questions should you ask a patient who’s a denture wearer?

Answer 5

Denture - how long have they been a denture-wearer, how many sets, age of current set, have there been any successful sets?

Social history - can they attend, carers, transport?

Medical history - muscles of mastication control, medications that cause xerostomia. Any medical emergenices.

Question 6

What things should you check EO in a denture-wearer?

Answer 6

• Asymmetry
• Lip support. Do they have adequate lip support?
• Tooth appearance - too long, worn down, too short, colour
• Overclosure. Too much freeway space can result in a large space for the patient to have to close which can cause problems in chewing, lip support and creasing at corners of the mouth. Freeway space for dentures are determined by dentist and also by wear on the teeth
• TMJ
• MoM control
• Pathology

Question 7

What things should you check for IO denture wearers?

Answer 7

• Ridge assessment. Is it pink and firm, or are they flabby (which means there’s not enough bone support so it’s just soft tissues which can move, and so a denture on top can also move). Are the ridges smooth or are there any lumps and bumps. Palpate this too.
• Is there any ulceration on the ridges or elsewhere in the mouth (breach in the epithelium). If it’s indurated and has rolled margins, this is concerning, as well as if bone is showing.
• Check incisal papilla
• Check rugae to ensure there’s no problems with that.
• Is there any redness of post-dam region?
• Check for papillary hyperplasia to ensure there’s no fungal infection.
• Check tuberosities - this is an area important for denture retention. Ensure there’s no undercuts as dentures are firm and so can’t get in there.
• Check saliva. There is a scale to assess saliva in patients.
• Check for any pathology. Older patients more likely to have oral cancer.

Question 8

What is a vibrating line?

Answer 8

The border between hard palate and soft palate. Denture sits just before this.

Question 9

How many denture wearers are there?

Answer 9

Reducing trends.

But still a lot of people wearing dentures.

Question 10

What is freeway space?

Answer 10

Space between teeth at rest, normally 2-4mm.

Question 11

How do you assess the patient’s dentures?

Answer 11

Upper denture first:

• Retention (see if denture falls down itself when patient opens, pull down on premolars to see if denture falls).
• Stability (rocking, rotating)
• Extension (check if over or under-extending by manipulating lips and cheeks and seeing if it dislodges, paying special attention to the tuberosities).

Lower denture alone:
- Stability (rocking, rotating, neutral zone, teeth positioned over ridge).

Both dentures together:

• Hold denture in place and guide pt into retruded position and check for premature contacts as this will lead to instability in function
• FWS using Willis Gauge.

Denture aesthetics and cleanliness.

Question 12

What is the neutral zone?

Answer 12

A position of balance between the forces of the tongue on one side and the forces of the cheek on the other.

Question 13

Why do you not check for retention in lower dentures?

Answer 13

Hasn’t got as much surface area as upper dentures to form a border-seal.

Question 14

What are the stages of constructing complete dentures?

Answer 14

• Primary impression
• Sent to lab to construct a special tray. This can go to the depth of the patient’s sulcus unlike stock trays.
• Secondary impressions to get an accurate impression of full depth and width of the sulcus, which is important for denture retention and stability.
• Sent to lab to construct record rims.
• Jaw registration done. We record the occlusion and it’s harder because we don’t know the patient’s bite so we need to know rules on where teeth go and what the patient’s bite is in order to create a good ICP and OVD for patient.
• Sent to lab who set up teeth and set up models with the right jaw relationship
• Try in stage with wax dentures. Check for occlusion and aesthetics.
• Send to lab for processing to finish if all good. Otherwise sent for adjustments and re-try in needed.
• Fit of denture appointment. Check everything.
• Review at intervals to ensure dentures are fine. Initially this is every 1 week but might be longer intervals.

Question 15

Define stability and retention

Answer 15

Stability - the forces that keep a denture in place during function
Retention - the forces that stop a denture from coming out

Question 16

What can make retention for complete dentures more difficult than partial dentures?

Answer 16

There’s no clasps or rest seats for retention.

Question 17

Why should you be careful when checking tuberosity region?

Answer 17

Ensure there’s no undercuts as dentures are rigid objects and can’t go over the undercut. This affects stability and retention.

Question 18

What things provide retention for a denture (broadly)?

Answer 18

• Border seal (peripheral seal and post-dam)
• Saliva (weak molecular forces, improved seal).
• Muscular forces (good molecular forces like tongue and buccinator)
• Accessory retention (springs/suction cups, implant retained overdentures, fixatives)

Question 19

Define border seal. How can you get it?

Answer 19

Border seal is the junction between the flange and the cheek. It goes all the way around and this forms a peripheral seal that air, food and water can’t get under to displace the denture.

You get a good border seal by ensuring you do a good secondary impression. Get a special tray 2 mm short of functional sulcus, and then use green stick/pink stick first to create a post-dam, and then apply it in tuberosity region and manipulate lips and cheeks to get a good functional sulcus.

Question 20

What is a post-dam?

Answer 20

A raised area on the posterior surface of an upper denture that sticks in to the tissues to ensure that a tight seal is formed between upper denture and posterior mucosa.

It is made by using green stick/pink stick on a special tray.

Question 21

What is the use of saliva?

Answer 21

Thin coating of it between the denture and mucosa can improve the seal.
This is because of saliva’s stickiness. Weak molecular forces between the saliva particles (cohesion) and forces of adhesion to the mucosa and denture which spread over a larger surface area are more valuable.

Question 22

How do we know that saliva is so helpful?

Answer 22

By assessing those with xerostomia.
Radiotherapy to head and neck which can result in damaged salivary glands, medication and autoimmune conditions like RA or Sjrogen’s.
Assess using a gloved finger and wiping.
And can suggest saliva additions or things to stimulate saliva.

Question 23

What are the good and bad muscular forces that can act on dentures?

Answer 23

Tongue keeps upper denture in place during chewing as the position of front teeth and direction, as well as lack of support can mean back of the denture can fall down.
The buccinator and orbicularis oris can also push on the upper denture to keep it in place.

Tongue keeps lower denture in place. Ensure the tongue can rest over the occlusal plane of the denture slightly by removing the 7s and by making the teeth narrower to avoid tongue cramping.
In the lower denture, the neutral zone must be maintained to balance the forces of the tongue and the forces of the cheek.
Ensure the teeth are over the ridge to avoid the mentalis muscle in the lower lip dislodging lower denture.

Question 24

What accessory retention is possible?

Answer 24

• Springs - can lead to skin and food trapping so is outdated.
• Suction cups - can lead to soft tissue trauma so is outdated.
• Implant-retained overdenture. Can be used to maintain bone, provide support and provide retention. Patients have a higher level of satisfaction and it can improve bite and chewing ability. Uses a ball and socket arrangement, or sometimes bars.
• Fixatives - these increase viscosity of the saliva to help the denture remain sealed in place. They can improve seal, improve QOL, improve biting force, and increase feeling of security. They are however considered by some dentists to be a replacement for providing a good denture so are controversial. Be careful for zinc as overdose can result in tingling/numbness in extremities and loss of balance.

Question 25

When are some instances when patients have poor muscular control?

Answer 25

Parkinson’s, stroke and motor neurone disease. Can cause problems in terms of muscular tone and control, and so denture retention issues.

Question 26

What are the effects of denture instability?

Answer 26

Pain - dentures rub on soft tissues during function as they move and so cause pain. Excess pressure to keep denture in place results in pain.
Speech - dentures move during function.
Chewing ability - can’t chew properly as dentures move, pain
Looseness - loss of retention due to teeth not being in neutral zone, loss of border seal, and loss of muscular control. Not enough saliva.
Social problems - avoidance of food places etc.

Question 27

What are the causes of denture instability?

Answer 27

Premature occlusal contacts
Lateral forces
Changes in support area under the denture

Question 28

What is balanced occlusion and balanced articulation?

Answer 28

Balanced occlusion - the teeth all meeting evenly on both sides when patient bites together.

Balanced articulation - during lateral movements having as many tooth contacts as possible

Question 29

What is denture hyperplasia?

Answer 29

Trauma and ulceration of soft tissues from repeated rubbing

Question 30

How do premature contacts lead to denture instability?

How can you check for it?

Answer 30

So if the teeth meet at one side before the other when you bite down, the upper denture on the other side will fall and the lower denture will raise up so that the tooth on the other side is meeting too. This will result in increased load on the biting tooth and PDL isn’t here to withstand the force so the load spreads down the soft tissues underneath. Can lead to pain in sulcus and on ridge. On the side where it’s not meeting, it can lead to the denture border seal being lost and so denture falls out.

You can check for premature contacts using articulating paper, but make sure you hold the denture in place. If there’s a premature contact, you’d be able to feel it.

Question 31

What other occlusal problems can cause denture instability?

Answer 31

If the teeth aren’t set over the ridge where the biting occurs (palatal fossa in uppers, central fossa in lowers), then this means that loads are spread to the sulcus (if upper teeth too buccal). This leads to pain and possible ulceration.

If there’s not balanced articulation, this causes the same issue as premature contacts with loss of border seal. You can ensure there’s balanced articulation by keeping teeth on the Curve of Wilson/Monson.

When the teeth protrude, they’re not in a straight line because the articular eminence pushes condyles down and forward (Christonsen’s phenomenon). So to keep all teeth in contact, teeth should be set of Curve of Spee.

Question 32

What other issue can lead to denture instability?

Answer 32

Flabby ridge due to bone resorption after extraction. Soft tissues move so dentures move.

Question 33

When setting up teeth, as you go posterior teeth should go….?

Answer 33

Upwards and outwards.

Question 34

Which articulator should you use?

Answer 34

Average value

Question 35

To ensure good retention and stability, what should you do and what are the common problems?

Answer 35

• Check for good border seal.
• Check for balanced articulation and occlusion and no premature contacts.
• For problems with pain and discomfort, it’s normally due to occlusion.
• For older dentures, it may be due to remodelling of the bone underneath, so reline/rebase may be required.