Bridge Bodies

Bridge bodies are vital bridge prosthesis elements that restore the function and aesthetic appearance of one or more lost teeth. The design of the body involves many important factors and should be carefully planned to meet the aesthetic and functional needs of the patient. Here are the factors affecting body...
Porcelain Teeth
Bridge Bodies
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Bridge bodies are vital bridge prosthesis elements that restore the function and aesthetic appearance of one or more lost teeth. The design of the body involves many important factors and should be carefully planned to meet the aesthetic and functional needs of the patient. Here are the factors affecting body design:

  • Aesthetics: It is important for the body to be aesthetically compatible with the dental alignment and appear natural. Tooth color and form should be considered.
  • Function: The body should replace the function of the lost teeth. It should assist in providing an effective and correct chewing function of the dental alignment.
  • Cleaning Ease: The body design should facilitate the patient’s ability to clean the prosthesis and maintain oral hygiene. It should also control plaque to protect the health of the gums and supporting tissues.
  • Edentulous Ridge: The body should replace the position of the lost tooth or teeth and maintain the continuity of the healthy tissues of the supporting teeth.
  • Patient Comfort: The body should be designed for the patient to use comfortably and to increase comfort.

Another important aspect of body planning involves biological factors. These factors concern the preservation and protection of the residual ridge, supporting teeth, and supporting tissues. Here are the subheadings of biological factors:

  • Body-Ridge Contact: It is important for the body to fit compatibly with the ridge and sit correctly.
  • Dental Plaque: The body design should facilitate dental plaque control and be appropriately cleanable to maintain gum health.
  • Shape of the Gingival Surface of the Body: Proper design of the gingival surface of the body helps support the health of oral tissues.
  • Body Construction Materials: The biocompatibility and durability of the materials used in body construction should be considered.
  • Direction of Occlusal Forces: The body design should ensure that occlusal forces are transmitted in the correct direction. These factors should be considered for a successful bridge body design and customized for each patient. This can increase patient satisfaction and the longevity of the prosthesis.

 

Body-ridge contact is a critical factor. Here are some important points to consider in this regard:

  • The contact area between the body and the ridge should be small and as convex as possible. This helps prevent tissue irritation and inflammation.
  • If there is contact along the gingivofacial angle of the body, there should be no gap between the body and the soft tissues on the facial side of the ridge. This enhances the fit between the tissue and the body.
  • The apex of the body should not exceed the mucogingival junction. Otherwise, bruising may occur in this area, and the body should contact the attached keratinized gums.
  • In the laboratory, on the model, scraping the area of the ridge where the body will sit and fitting the body with pressure is not recommended. This pressure can lead to inflammation and leave marks of the body on the ridge.
  • Generally, it is accepted that the body should not apply pressure to the ridge.

Dental plaque is the main cause of ridge irritation and should be prevented with good oral hygiene, plaque control, and the ability to clean well under the body. Cleanability is directly proportional to the shape of the ridge and the type of material used.

The gingival surface of the body should allow easy cleaning by the patient. This helps maintain good oral hygiene using dental floss and interdental brushes. Additionally, the aesthetic appearance of bodies designed in visible areas is also important.

Body design can be examined under three main headings according to their relationships with the ridge: Ridge-lap (Saddle-eye shape), Modified Ridge-lap, and Hygienic. Each design has its advantages and disadvantages, and the choice should be made based on the patient’s needs and oral conditions.

Ridge lap body design offers a shape that includes all the contours of the missing tooth and resembles a tooth. However, it can present challenges in terms of cleanability and can cause tissue irritation.

The Modified Ridge-lap body design is created to maintain aesthetic appearance while providing ease of cleaning. This design allows contact between the body and tissue only on the crest’s buccal side by making alterations on the lingual surface. The lingual surface is as convex as possible, and all contacts between the body and the crest are passive. This design is important in that it allows only the lingual surface to be convex for maxillary posterior and all anterior bodies.

The Hygienic body design is particularly used for the completion of missing mandibular first molars. This design restores occlusal function and stabilizes neighboring and opposing teeth. The body is made completely convex in the faciolingual and mesiodistal direction, which allows for easy cleaning. However, a disadvantage of this design might be that it can cause food to get trapped between the tissue and the underside of the body, frequently bringing the patient’s tongue to an uncomfortable area. Also, it fails to provide tissue support. It is important to note that the Hygienic body design is contraindicated in the presence of minimal vertical space and can cause tissue proliferation when the body is too close to the crest. In cases of excessive resorption in the mandibular posterior and anterior areas, modified hygienic designs (such as conical and oval body designs) can be applied, thereby providing tissue support. Conical bodies are rounded and cleanable, suitable for use on thin mandibular crests. The Oval body design is a round-ending design used in areas where aesthetics are important.

The body material can be made from various materials such as ceramic, metal-ceramic, and cast metal. Clinical studies have shown that all materials used for the body are generally well-tolerated but any of these materials can cause some inflammation in the gingival tissue. Porcelain has been observed to be easy to clean and hygienic, hence many clinicians prefer glazed porcelain as the sole material in contact with the edentulous crest. Glazed porcelain and well-polished gold are preferred for contact with the tissue.

Finally, the body design plays a role in reducing the impact of occlusal forces. It is suggested that reducing the bucco-lingual width of the body by 30% effectively reduces the impact of occlusal forces on the supporting teeth.

Mechanical factors are a significant factor affecting the success of fixed prosthesis bodies. Mechanical problems can arise due to inappropriate material selection, poor metal substructure planning, inadequate tooth preparation, and occlusion issues. Particularly, long-bodied posterior bridges tend to flex due to high occlusal forces.

Metal-ceramic bodies are preferred for their durability, ease of cleaning, and natural appearance. However, some important mechanical factors should be considered for a well-made metal-ceramic body:

  • The metal substructure must be properly fused with the porcelain. At least 1-2 mm space should be provided for the porcelain. Excessive thickness of the porcelain can negatively affect the support and cause fractures.
  • The smoothness of the metal surface is important. If air bubbles form at the porcelain-metal interface, bonding strength can decrease, increasing the risk of mechanical failure.
  • The metal substructure should avoid sharp angles to prevent stress concentrations.
  • Any deformation at the metal-porcelain junction can cause porcelain to fracture. Therefore, occlusal contacts at the junction should be avoided.

Aesthetic factors are important in achieving a natural tooth appearance in fixed prosthesis bodies. Some aesthetic factors include:

  • The body should give the impression to the observer that it is a natural tooth.
  • Shadows on natural teeth and the proportions between the teeth should be considered.
  • The width and height of the missing tooth gap must be taken into account.
  • In cases of severe resorption, procedures like crest augmentation can be applied.
  • In anterior bodies, aesthetics should be the primary focus. The body should resemble the teeth in color and shape. The lip-tooth relationship is also important; interproximal spaces or contact areas should be placed according to whether the lip line is low or high.
  • Posterior bodies should reflect the anatomical characteristics of the natural tooth. Changes in the body design can be made considering the length of the edentulous crest, the level of resorption, aesthetic factors, and occlusion. Reductions in the body can lessen the force on the supporting teeth. Reductions made from the lingual surface provide ease of hygiene and can increase tissue stimulation.

These factors represent important considerations affecting the success of fixed prosthesis bodies. Since each patient’s situation can be different, taking these factors into account and planning according to the patient’s needs is crucial.

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