Bridges and crowns of metal and plastic have a plastic coating, located only on the visible surfaces of the teeth from the side of the lips, and the rest of the device is made of metal. This type of devices are often used in practice because of their lower cost and faster production, mainly for patients who do not have high aesthetic requirements or do not have the financial ability for a ceramic device.
A metal and plastic bridge is a cast metal device with crowns, a pontic and a plastic coating. Metal alloys are biocompatible, precious and resistant to abrasion and corrosion. The plastic coating is placed only in the outer (vestibular – visible) side with a protective metal edging. This edge is in the top of the crown and protects the plastic from masticatory forces.
In these bridges grinding of teeth is required on the visible side (towards the lips and cheeks) in order to secure an area to apply the layer of plastic. In order to piece together the metal and plastic, retention beads, edges, etc. are made to provide structural strength of the device. A disadvantage of this type of crowns and bridges is the bond between the aesthetic plastic part and the metal, and the labile colour of the plastic. Over the years, it gets old and changes. With load or mechanical friction (solid foods or hard toothbrushes and rough tooth brushing), the aesthetics of the bridge is disrupted. Modeling (dental production) cannot always mimic every detail of the teeth. In defects or breakage of the plastic coating, adjustments in the mouth are difficult. This requires removal of the bridge and replacing the plastic, if possible, otherwise the structure must be developed anew.
The making of this type of bridge is standard. It includes preparation, planning of the device, preparation of the carrier teeth, an impression, fabrication in a dental lab, fitting and fixation. For larger devices (5-6 teeth, all front teeth or whole jaw), a careful fitting of the metal skeleton is carried out and only then the plastic coating is put. A more detailed method for making bridges and crowns is described in the section Fabrication of crowns (read more…). To avoid the disadvantages of plastic and increase the aesthetic and functional effect, the devices can be replaced by a new one or one made of metal and ceramics.