A metal-based denture is one in which a portion of the denture body is made of a substantial metal casting rather than all plastic (acrylic resin). This procedure is usually done on the lower denture.
There are two types of metal-based dentures.
The metal base portion of the denture is in direct contact with underlying supporting tissues.
The base is fabricated from a special medical grade alloy that is hypoallergenic and very biocompatible with tissues. Generally, tissues in contact with this type of material are very healthy in appearance.
The metal base portion of the denture is not in direct contact with underlying supporting tissues. A soft or hard plastic liner may be interposed between the metal and supporting tissues.
A soft liner is generally preferred to hard plastic since it is more comfortable to wear; however, the soft liner usually should be replaced on an annual basis.
Sometimes it is necessary to construct a very narrow denture in order to avoid any structures that would loosen the prosthesis, such as muscles flexing, and so forth. In addition, necessary surgical procedures to reposition a muscle attachment (called a frenum) can sometimes be avoided with these narrow type dentures.
However, such narrow dentures are weak and tend to break quite easily when fabricated just from plastic. A metal base provides the needed strength to design a very narrow denture in order to follow the confines of a patient's lower resorbed alveolar ridge (the remaining bony ridge). In addition, the metal base provides long-term dimensional stability and strength that is not enjoyed with an all-plastic denture base.
The added weight of the metal base provides a more natural perception for many patients. Many patients prefer the additional weight on the lower jaw.
A private study measured the actual weight of cadaver jaw ridges and teeth that would normally be lost after the extraction of teeth and associated natural shrinkage of the jawbones. It was found that the weight of these tissues closely approximated the weight of a metal base. Therefore, it is likely that the more natural feeling perceived by persons wearing metal-based dentures is probably real rather than imagined.
The additional weight of a metal base also contributes to lower denture stability by causing the denture to settle down onto a jaw ridge.
by Joseph J. Massad, D.D.S.