Full dentures and some partial dentures transfer some of the biting forces to the gums. Full dentures, especially upper full dentures, stay in place because of their accurate fit to underlying structure of the mouth. That underlying structure, once upon a time, used to hold teeth. It’s purpose in life was to hold teeth and to receive and dissipate the forces placed on them. No longer.
When the bone underlying a denture is denied its purpose in life – supporting teeth and dissipating the forces placed on it – it tends to shrink in size. Its new purpose is merely to support a denture and the much diminished forces placed indirectly on it via the cushioning action of the gums. Nature, being very efficient, alters the structure so that it is appropriate to the demands placed upon it. The tissues supporting the denture shrink in size and shape. The dentures lose their fit and become loose. Chewing is less efficient.
It’s a vicious cycle. As the efficiency of chewing diminishes, so do the forces placed on the gums. Nature responds by shrinking the underlying bone even faster.
“Faster” is perhaps misleading. It’s a gradual process that occurs over several years. People adapt to gradual change, and in the case of denture wearers, that is unfortunate – folks tend to persist in learning to use dentures that don’t fit very well. They forget how well they used to fit. Their persistence and adaptability – generally “noble” characteristics – work against them.
Relines Slow Disuse Atrophy
The shrinking process is called “atrophy.” When normal stimulation or function of a body part diminishes, so does the body part. That is atrophy caused by disuse (or, more correctly, diminished use.) If the surface of the denture that contacts the gums is, from time to time, adjusted to fit the new shape of the gums, the the function of the denture improves. Forces are transmitted more efficiently. Disuse atrophy slows down.
The process of adjusting the denture to fit the new (shrunken) shape of the gums is known as relining the denture.
Part of a Re-Care appointment for denture wearers is to check the function, retention, stability and efficiency of their dentures. Often, even though the patient is satisfied with the denture, it is obvious to us that a reline is called for.
Sometimes it’s obvious to the patient.
Types of Relines
Denture relines can be done:
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in the dental office – a “chairside” reline: The reline is done using materials that set in the mouth.
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Disadvantage:This material will not polymerize as well as heat-cured material. It will also leach (toxic?) ingredients as it is setting. You will know this from the unpleasant taste and smell.
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Advantage: You keep your denture. You don’t have to face the world without teeth for a few days.
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by a dental laboratory: The reline is done using materials that are heat-processed in the dental laboratory.
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Advantage: The resultant heat-processed material will be less toxic.
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Disadvantage: You face the world without teeth during the few days the laboratory is doing its thing.
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Either type can be:
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a resilient material – a “soft reline”
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Disadvantage: Soft reline materials don’t last as long and tend to be more costly.
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Advantage: Soft materials are kinder to tissue which can made tender by the pressure of dentures on them.
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a rigid material”
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Disadvantage: Some people’s gums become tender with chewing forces. In the lower jaw, the nerve can be close to the surface and become sore.
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Advantage: Rigid reline materials transmit chewing forces more efficiently. Therefore rigid materials are used unless there is some reason not to do so.
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Soft Relines in turn can be:
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Temporary – They are intended to last only for a month or so, usually during healing or to allow irritated tissues to heal.
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“Permanent” – They are intended to last for a few years.
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Immediate Denture Relines
“Immediate Dentures” are provided at the same appointment that the teeth are extracted. This prevents “facing the world” without teeth and helps protect the extraction sites during healing.
That is because as the bone and gums heal it “remodels” itself and shrinks in the process. The remodelling of healing occurs over a time span of a few months. The longer-term shrinkage of disuse atrophy occurs over a time span of years. During healing several relines are usually required. They are almost always the soft, chairside, temporary type.
Duplicate Denture Strategy
Relining dentures is a necessary evil. No one wants to face the world without their dentures. Many denture wearers deal with the problem by having two sets of dentures. One of them is inevitably the “favourite,” the other is the “backup.”
It usually works like this (using complete upper and lower dentures as an example):
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Teeth are removed and a set of immediate dentures is delivered at that appointment.
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During healing, a series of soft relines are done as required.
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Once healing is complete new dentures are made to fit the fully healed shape of the denture-bearing tissues.
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The new dentures are delivered and the patient adapts to them.
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The original immediate dentures (with the soft reline) are sent for a laboratory processed reline.
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This second set is delivered and the patient adapts to them as well.
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One of these sets of dentures becomes “the favourite.” Eventually – typically a few years later – they will need to be relined.
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The backup set (with perhaps a chairside reline) can be worn while the other set is at the lab.
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The relined “favourites” can be adapted to and the backups sent for a lab-processed reline.
There is the added advantage to this strategy that if a denture becomes lost or broken, a spare is available. This strategy has prevented many a foreign vacation from being spoiled.