Bar prosthesis

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Bar construction on implants in the upper jaw to accommodate a prosthesis

A bar prosthesis is a partial prosthesis that is attached to a bar. The bar has a holding and supporting function and a round or rectangular cross-section. The bar splinters two teeth or implants . The bar can be lasered or soldered on to the root caps , anchor crowns or superstructures of dental implants . Several such bars can be connected to one another. Bar prostheses are removable prostheses that can also be fixed using bolts. They fall under the category of combined dentures, as part of the prosthetic restoration is firmly anchored in the mouth and the other part (with metal base and retaining elements) is removable.

For a bar, at least two teeth must be ground and crowned or it is installed between two implants. The crowns are connected by the bar and are permanently cemented in the mouth. A matrix is integrated into the prosthesis and can be reinforced with metal to increase the breaking strength. The prosthesis is held on the bar by friction or wedging, depending on the profile of the bar. A suitable bar rider is worked into the denture base. This enables a hinge-like connection between the bar and the prosthesis.

Manufacturing

After taking an impression of the ground teeth to accommodate the crown / bar construction, they are manufactured in the dental laboratory. Intermediate steps for determining the jaw relation , for checking the position of the jaws in relation to one another, for checking the accuracy of fit and for the functionality of the bar are required. The selection of the bar depends on the remaining teeth. Gold , platinum or non-precious metal alloys are used as the material . The matrices can be made of metal or plastic (Bredent system).

Dolder footbridge

Bar joint prosthesis according to Dolder for the primary locking of two maxillary implants (historical film 1976)

The Dolder bar joint is an anchoring element that allows three degrees of freedom, translational and rotational movements. The bar is egg-shaped and allows for resilience compensation. The support and hold is mainly provided by dentures carried by the gums (gingival support). In the Dolder bar joint, there is a resilience margin of 0.5–1 mm between the bar with an oval cross-section and the rider - when the prosthesis is in the rest position. This distance decreases with increasing chewing pressure due to the yielding of the gingiva until the load changes to periodontal load (absorption of the chewing forces by the teeth).

Bar construction according to Zimmermann

The "bar construction according to Zimmermann" (according to MDT Suzanne Zimmermann from 2010) is a construction that gives the patient a sense of security and stability from the outset thanks to its stable and rectangular bar with approx. 4 × 3 mm (this varies depending on the space available) gives without the patient noticing a "wobbling" of the prosthesis, since degrees of freedom are largely avoided. The patient feels this bar construction more like his own teeth, similar to a fixed bridge. Since TK-Snap assembly parts (from Si-Tec) are used here for the hold, which hit the vertical web from the horizontal, the pull-off forces are used as best as possible. Another advantage of the Zimmermann bar is that the TK-Snap friction elements sit in ready-made mounting boxes in the prosthesis and can therefore be easily removed and, if worn, can be used again in the exact position, which is often a challenge with other bar constructions to position the friction elements correctly. In addition, if the bar is manufactured correctly, the patient hears a slight snap or click when the prosthesis is inserted, and this confirms that the prosthesis is in the correct position on the ridge.

Implant-supported bar prostheses

Bar prostheses can be attached to at least two implants. They are mainly used in edentulous patients with a broken jawbone . When using four implants, the functional life of the implants is better guaranteed. Ideally, the implants are distributed interforaminally in the lower jaw, ie in the frontal jaw area between the two mental foramina , which reliably prevents injury to the mandibular nerve . Should there be any remaining teeth, this can be included. A connection of still existing natural teeth with the implant-supported bar prosthesis is not mandatory.

  • Bar framework on implants, upper jaw plaster model

  • Secondary construction prosthesis

  • Prosthesis inserted over the bar construction

  • Front view of the dentures

  • Bar prosthesis.png
  • Bar prostheses.png

advantages

  • Implants blocked by bars should be replaced with dentures immediately (without waiting for osseointegration )
  • With periodontally weakened teeth, the root load is reduced by reducing the lever arm
  • The removable prosthesis is held firmly by the rider's clamping effect
  • The bars make bar prostheses very stable.
  • If a metal base is used in the prosthesis, a palate plate can be dispensed with.
  • Bar prostheses can be designed gracefully and are therefore extremely comfortable to wear.

disadvantage

  • There is difficult oral hygiene below the bar.
  • The costs are increased by the implant supply
  • Food remains under the prosthesis are not unusual
  • Wear of the bar riders, thereby loosening the prosthesis hold over time
  • If the bar is not tension-free, implants are at risk from peri-implantitis , screw loosening or implant breakage.

forecast

Bar prostheses are a reliable form of denture for severely reduced dentures. Long-term restoration can be guaranteed, especially with the use of implants.

Individual evidence

  1. ↑ Harald Schrenker: Compromises and limits in prosthetics . Spitta Verlag GmbH & Co. KG, 2003, ISBN 978-3-934211-61-2 , pp. 27–.
  2. ↑ Klaus M. Lehmann, Elmar Hellwig, Hans-Jürgen Wenz: Dental Propaedeutics: Introduction to Dentistry; with 32 tables . Deutscher Ärzteverlag, 2012, ISBN 978-3-7691-3434-6 , pp. 324–326.
  3. ↑ Eugen Dolder, Bar Prosthetics. The bar-joint prosthesis - the bar-attachment prosthesis. Hüthig Verlag, 1966.
  4. ↑ Suzanne Zimmermann: "Bar construction according to Zimmermann" . Ed .: Verlag Neuer Merkur. Dental-Labor magazine, August 2019, p. 82 .
  5. ↑ K.-U. Bochdam, K.-U. Benner, T. Holland-Letz, F. Hölzle Clinical follow-up examination of implant-supported full dentures in the edentulous and residual dentition - a comparison between telescopic dentures and the established bar dentures
  6. ↑ Wolfgang Dinkelacker: Implant prosthetics: Biomechanical and prosthetic concepts in implantology . Thieme, May 28, 2014, ISBN 978-3-13-173811-0 , p. 128–.
  7. ↑ K.-U. Bochdam implant-supported telescopic prostheses - does the integration of remaining teeth make sense? - a microbiological follow-up examination