Cobalt chrome dentures are a less bulky, stronger alternative to acrylic dentures; however, they are considerably more expensive than acrylic dentures and are not a suitable type of denture for those who require full dentures due to the way that they are retained in the mouth.
This type of denture consists of a metal framework which sits on the palate in upper dentures and around the lingual side of the alveolar ridge in lower dentures. Acrylic is used to hold the false teeth in place and is incorporated into the metal framework.
Retention of cobalt chrome dentures is usually achieved by the use of metal clasps which are included in the denture design. These metal clasps fit closely around existing teeth or crowns and are strategically placed so that the denture is evenly supported and is more likely to remain stable during use. Occlusal rests can also be used to help retain and support a cobalt chrome denture. An occlusal rest is created by the dentist cutting a seat or small pit into the biting surface of a patients existing restoration – such as a filling or crown. The denture will then be made to include a ‘plug’ which will accurately fit into the occlusal rest (without altering the patients bite); this allows the existing tooth and denture to fit together like jigsaw pieces and helps to hold the denture in place.
The metal framework of a chrome denture is designed specifically for each individual patient; this is due to the laws of physics! Relevant points to consider when designing the framework for a denture of this type include;
- The position of existing teeth
- The number of existing teeth
- Restorations present in existing teeth
- The shape of the palate or alveolar ridge
- Patient preferences for overall design e.g. for upper cobalt chrome dentures some patients prefer to have their palate covered while other prefer to have minimal coverage of their palate
The in surgery procedure for making a cobalt chrome dentures is much the same as that for making acrylic dentures, however, there is often an extra stage and appointment required for a try-in of the metal framework which obviously has to be as accurate as possible in order to be comfortable and functional, also the fact that cobalt chrome is difficult to adjust, unlike acrylic, means that there is very little room for error!
Many dental laboratories do not make the cobalt chrome framework for dentures themselves, and will often have to send models, impressions, bite registrations, design requirements, etc, to another laboratory who specialise in the making of these. Due to the involvement of another dental laboratory or simply due to the complexity of this task, there can often be, at this stage, a two week gap between appointments for patients and dentists which in turn, prolongs the overall treatment time taken to make the denture.
There are advantages and disadvantages to choosing a cobalt chrome partial denture over an acrylic partial denture.
Cobalt Chrome Dentures – Advantages
- Less bulky
- Less coverage of soft tissues and is therefore less likely to affect ability to taste of food
- Does not rely on suction (good for those with a reduced saliva flow)
Cobalt Chrome Dentures – Disadvantages
- Difficult to adjust
- Difficult to add extra teeth on to if future extractions are required
- Clasps can sometimes be positioned in easy to see areas
- May required creation of occlusal rests
- Takes a longer time to make the denture
Many patients who wear partial dentures prefer one type of denture over another and once they have found a type and design of denture that they are happy with, will usually stick to that same type of denture in the future if possible.