Fixed/removable prosthetics
Fixed/removable prosthetics
Fixed/removable prosthetic restorations form a part of prosthodontics. Unlike with full dentures, fixed/removable restorations always involve natural teeth and/or implants. As opposed to purely removable dentures (which include full dentures and partials retained on natural teeth with clasps), fixed/removable dentures consist of two sections, i.e. one fixed and one removable section.
Fixed/removable denture including CoCr, clasps, precision attachment and double crowns (demo model)
Fixed telescopic crowns (primary)
The patient-removable section with its retainers and connectors (e.g. clasps, precision attachments, telescopic crowns, press-stud systems, magnets etc.) is anchored on the periodontally-borne, fixed section of the restoration usually consisting of single crowns or bridge abutments supported on natural teeth, implants or implant abutments.
Removable partial denture (secondary section)
Removable lower partial denture
A removable bridge (usually "telescopic" and borne on telescopic crowns) replaces teeth with bridge units and almost never requires mucosal coverage.
Other types of fixed/removable prostheses always include sections which are supported by and exert pressure on the mucosa. A coverdenture fully covers all connectors and includes teeth corresponding to those of a full denture. That section of a fixed/removable prosthesis covering the hard upper palate is referred to as the palate and sections on edentulous areas of alveolar ridge are called saddles. In fixed/removable prostheses with multiple saddles they are often connected via a metal base – in the maxilla using a major connector (transverse) and via a lingual bar in the lower. Fixed/removable prostheses may also be totally metal-free. Missing teeth are usually replaced with prefabricated acrylic denture teeth and less frequently with prefabricated porcelain teeth.
When fabricating fixed/removable prostheses, special impression material and techniques are employed in an attempt to ensure that the denture base rests uniformly on the jaw. Exceeding the resilience of the mucosa or repeated "scrubbing" movements of the fixed/removable prosthesis may quickly result in pressure spots. After months or years, the bony denture base undergoes varying degrees of physiological and pressure-induced atrophy. The denture base can be relined to restore congruency.
Unlike purely fixed prosthetic restorations, fixed/removable prostheses can be cleaned and repaired extraorally. In addition, examining the residual dentition and maintaining its hygiene is easier. In case of loss of load-bearing abutments, fixed/removable restorations can often be extended without needing remaking.
Placing implants to increase the number of abutments supporting fixed/removable prostheses results in firmer, more stable retention and relieves the loading on the residual natural dentition.
Fixed/removable prostheses replacing not only missing teeth, but also other anatomical structures are referred to as maxillofacial appliances.
Tooth/implant-borne bridges are normally not considered to be fixed/removable restorations but rather purely fixed prostheses (possibly operator-removable) supported on natural teeth and implants.
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Word of the day
| English | German |
|---|---|
| ridge lap pontic | sattelförmige Auflage |
Focus text of the month
Full dentures Full dentures (also called complete dentures) are removable restorations. They replace all the teeth in an edentulous jaw, mainly using prefabricated acrylic denture teeth and less… Full dentures Full dentures (also called complete dentures) are removable restorations. They replace all the teeth in an edentulous jaw, mainly using prefabricated acrylic denture teeth and less commonly made from porcelain. The denture base in the upper and lower jaw is generally made from acrylic (e.g. acrylates); in cases with particular requirements the hard palate of the upper jaw is covered by a metal palatal plate. There is no alternative restoration to full dentures without involving implants. An overdenture is a partial denture. An overdenture completely covers all elements connecting it to existing teeth or implants.
As no information regarding occlusal height, occlusal relationship, tooth position etc. can be derived from existing teeth for full dentures, step-by-step reconstruction of intermaxillary relationship and soft-tissue support, function and aesthetics using anatomical conditions is a particular challenge. The consistency of measured values such as the mandibular rest position or the extent of its variability due to tooth loss and restoration is therefore debatable. Diagnostic impressions of the jaw and, if applicable also an existing denture, are traditionally taken using stock trays for the fabrication of full dentures. Custom trays (functional trays) fabricated on the diagnostic models or existing dentures are used for taking functional impressions, after adaptation and additions (e.g. using thermoplastics, silicones). Positionally stable, slow-curing impression material (e.g. PVS) on the one hand produces different compression depending on the resilience of the mucosa, thus resulting in uniform pressure distribution to prevent pressure spots at a later stage. In addition, functional movements (swallowing, tongue, mouth, jaw and lip movements) are recorded to relieve anatomical and functional boundaries (e.g. mobile mucosal sections, fraenums or soft palate). The aim with full dentures in the upper jaw, therefore, is to achieve suction adhesion (distal post dam on the junction between the hard and soft palate, the palatal vibrating line); in the lower jaw the least objective is to have the denture rest in position.
Bite registration and determination of the midline, occlusal plane and height are completed using templates with bite rims or arrow point tracing; these are checked, for example, using speech tests. Facebow transfer can be used for arbitrary hinge axis determination. A try-in of the prefabricated denture teeth set up in wax on the acrylic baseplate enables a check of the aesthetics, retention, occlusion, articulation and speech function prior to finishing. The denture is finished in the dental laboratory. Various procedures are used with cold and heat-curing acrylics, pressing, packing, syringing and pouring, flasks or overcasts etc. Following final adjustment of the occlusion and articulation, trimming and polishing the denture is fitted in the patient's mouth.
In recent times this sequence with five to six appointments, which has been established for decades, has been considerably reduced (to two to three appointments) thanks to extensive digitisation. Different manufacturers offer the transfer of data acquired from the patient into a computer-supported virtual system. Digitised patient anatomy and prefabricated teeth or dental arches are placed in relationship to each other in a virtual articulator using CAD programmes and the denture base is then milled from a blank using a CAM process. The dental arches are either integrated in the milling blank pre-set (full denture is fabricated right away) or set up using prefabricated teeth (wax try-in and adjustment possible). |
Occlusal view of previous/new full dentures
Full dentures viewed from the fitting surfaces
Full dentures, lateral view