Denture relining – called relining for short – improves the fit, support and function of an existing denture by readjusting it to changed conditions of the surrounding soft tissues and the supporting jawbone. The oral mucosa and the jawbone it covers are subjected to constant pressure by a denture. A denture must therefore distribute this pressure as evenly as possible over the denture base via its so-called base, thereby largely sparing the hard and soft tissues under load. Nevertheless, the jawbone reacts to the pressure load by receding. This leads to gradual alveolar ridge atrophy (recession of the part of the jawbone that used to support teeth), which is particularly detrimental to denture retention in the mandible. The shape of the denture base and denture bearing no longer match. The surrounding soft tissues are also subject to changes. Weight fluctuations, but also muscle loss of the cheek and lip muscles, lead to a poorer sealing of the denture margins by the soft tissues, so that penetrating air reduces the suction adhesion of the denture or food residues lead to irritation. The need for relining may arise not only for total dentures (full dentures), but also for the mucosa-supported portion of a clasp denture or a combined denture such as a telescopic denture. In this case, atrophy of the jawbone leads to excessive stress on the remaining teeth, which may become loose as a result. Free-end dentures sink in too far and thus deflect the supporting teeth too much. For the reasons mentioned, it is important to adjust the denture to the changed conditions again and again with the aid of relining. The occlusal complex (the rows of teeth set up in the acrylic) remains unaffected. Only the denture base (the side of the denture facing the jaw) is readjusted to the oral situation.
Indications (areas of application)
- Recurrent (recurring) pressure sores.
- Poor fixation of the prosthesis by the surrounding soft tissues
- Retention (lat. : retinere = “to hold back”) of food debris under the edge of the prosthesis.
- Denture loosens when chewing or speaking – too little suction adhesion.
- Tooth loosening of teeth supplied with braces, telescopic crowns or attachments.
- Pain in the abutment teeth – due to the increasing load, because the denture areas supported by mucosa are worse supported.
- After denture extensions in the area of extracted (pulled) teeth.
Contraindications
- Change of jaw relation (positional relation of both jaws to each other) required – both in case of too high and too low relation, the latter in case of strongly abraded (rubbed off) denture teeth, there is an indication for new fabrication of a denture
- Significantly underextended (much too short) denture margins – new supply.
- Need for pre-prosthetic surgery (surgical corrections to the prosthesis site prior to reprovision).
- Intolerance to methyl methacrylate – alternatives: polycarbonates, polyacetals, polyamides, rubber.
The process
I. Direct relining
This type of relining has significant disadvantages compared to the indirect method mentioned under II. Because the setting reaction occurs without pressure, the hardened relining material is porous and therefore more susceptible to adhesion of food debris and bacteria, making it less hygienic. Since curing must take place at body temperature, more residual monomer remains in the material, increasing the risk of allergization to the denture resin. In addition, the plastic phase in which the material margins can be functionally shaped is only very short. Direct relinings are therefore usually only a temporary (bridging in time) measure until the functional capability of the prosthesis can be restored with a more time-consuming indirect relining. Procedure:
- Preparation of the denture – cleaning and roughening of the denture base (side of the denture facing the mucosa).
- Mixing cold polymerizing (curing) PMMA-based resin (polymethyl methacrylate).
- Applying the cold polymer to the denture base.
- Insertion into the mouth and fixation in the final position until the resin hardens.
- Functional impression to reshape denture margins – Before the relining material hardens, active and passive functional movements are made to adapt the denture margins to the surrounding soft tissue during mastication, swallowing and speech.
- Reworking the margins
II. Indirect relining
For indirect relining, the denture is made in the dental laboratory after appropriate pre-treatment at the dentist. Procedure dentist:
- Preparation of the denture – cleaning
- If necessary, functional edge design – Thermoplastic material is applied to too short prosthesis edges and adapted to the soft tissue situation.
- Mixing impression material – usually addition-curing silicone or polyether.
- Applying the impression material to the denture base.
- Insertion into the mouth
- Fixing in the final position until the impression material hardens – either by the dentist (mouth-open technique) or by the patient when the teeth are closed (mouth-closed technique)
- Functional impression – active and passive functional movements prior to hardening of the impression material (cf. I.)
Laboratory:
- Pouring the impression with plaster
- Socketing in an auxiliary device (relining device, fixator or articulator) to ensure vertical relation (bite height)
- Making a counter – pouring the oral (facing the oral cavity) side of the prosthesis also with plaster. The counter is clearly fixed in its positional relationship to prosthesis by the auxiliary device.
- Removal of the impression material
- Grinding of the denture base (jaw side of the denture).
- Filling the hollowed areas – either with cold polymer (see I.) and subsequent polymerization (curing) in the pressure pot or hot polymer with subsequent curing under pressure in a water bath.
- Detachment of the prosthesis from the plaster base.
- Finishing the border zones and final polishing of the entire prosthesis.
Dentist:
When the relined denture is reinstalled, the following parameters are checked and corrected if necessary:
- Occlusion (final bite and chewing movements).
- Freedom of movement for the frenulum of the lips, cheeks and tongue.
- Embedding of the functional margins in the surrounding soft tissues.
III. soft relining
The procedure is the same as indirect relining, with the dental laboratory adjusting the layer thicknesses of the soft relining material to the different loading zones. A particularly unfavorable denture bed, as is the case with mandibular atrophy (lower jaw with severe reduction of the bone portion that used to support the tooth), is less at risk of pressure points as a result. A soft relining material based on PMMA (polymethyl methacrylate) contains so-called plasticizers, which ensure that the denture base can be compressed. However, external (added) plasticizers in particular volatilize in the medium term, so that the plastic becomes brittle after six to twelve months. If the material is inherently elastic, it retains its elasticity for longer but is less stable in terms of color. Germ colonization of these materials is easier than with hard relining resins, so that this in turn can cause irritation of the mucous membrane. Polysiloxane-based relinings are significantly more durable and therefore preferable.
After the procedure
As a rule, an appointment is made promptly to check the pressure points.
Possible complications
- Pressure points
- Altered occlusion (final bite and chewing movements) due to relining-induced change in vertical relation (bite elevation).
