Clinical Continued »
denture you make if you can’t achieve stable, long-term, posterior support from balanced even contacts with the lower. To achieve this, certain considerations
for the lower are also required: ı. Rigid and stable – most effectively achieved by being tooth supported anteriorly with chrome guideplanes – acrylic and flexible dentures will not achieve this
2. Retentive – anterior clasping, guide- planes and use of a good denture fixative under the edentulous bases.
A similar situation to the upper exists in
that there is the potential for a tooth/tissue compression differential in the lower when making a chrome. For the best stability, it is important to compensate for this. The simplest approach is the use of a split-cast technique (Applegate split-cast technique). When the framework is returned for
fit, verify that the close-fit special trays are on the edentulous saddle areas. These are border moulded with greenstick and a monophase, or mucocompressive, impres- sion material is used for the impression. At the same time, the bite registration in centric relation can also be taken (Figs 4 and 5). The above techniques will allow fabri-
cation of stable retentive bases, the final challenge is in managing the occlu- sion. Anticipating bruxing or clenching, it is important to have the dentures constructed with a degree of anterior open bite. Generally, about ımm is sufficient not to impose on speech. Balanced occlusion with shallow cusps helps reduce the desta- bilising lateral forces. Even after this, it is essential to monitor patients to ensure that the posterior support is being maintained. Often, after a few months, the anterior
teeth are found to be occluding with the upper base and destabilisation is occurring. This should not be allowed to continue, even if the patient is happy with the situation. Options at this point are:
ı. New bite registration and resetting of posterior teeth
2. Addition of tooth-coloured acrylic or composite, chair side, to the posteriors to open the vertical (Figs 6-8). Regular review appointments are required to ensure stability is maintained.
Use of implants in the CS patient Dental implants can be used to manage the combination syndrome patient. Any implant treatment will depend on a multi- tude of factors including: bone loss to date, aesthetic goals, functional goals, budget,
52 Scottish Dental magazine Fig 6-8
Acrylic or composite can be added to the occlusal surface of the denture teeth to maintain posterior support
“Implants can be used to manage the CS patient”
parafunctional history, medical history, etc. A number of studiesı have looked at
the bone resorption in the posterior mandible for a conventional removable partial denture (RPD) versus two-implant over-denture versus a fixed implant bridge (four or more implants between the foramina). The results show that ‘no denture’ or a ‘fixed bridge’ have the least bone resorption. Next best is two implants supporting an over-denture and then the RPD. It is postulated that this is because the hyper-eruption does not occur with the implants. This would suggest that a reasonable
option is for removal of the remaining lower teeth and placement of implants before bone loss has occurred. While this is indeed an option for some patients, it should not be a ‘treat all’ approach. We
would suggest that all factors need to be taken into consideration as part of the comprehensive planning process to arrive at a solution that best suits the individual’s needs, dental goals and budget. While implant placement in the lower
arch may reduce bone loss in the posterior mandible, what effect does this have on the upper arch? The literature is unclear on whether an implant-supported restoration in the lower results in more or less CS-type bone loss in the upper. Bone loss, however, does occur and all papers agree that loss of posterior occluding contacts is particularly damaging. Patients undertaking implant treatment in the lower should be guided to understanding that continual bone loss in the upper will likely occur. Special mention should be made for
the class III mandibular relationship F/F patient. Here, it is possible to iatrogeni- cally create a combination syndrome if the patient elects, or is led, to have a fixed implant bridge (all on four type restora- tion) in the mandible. The edentulous lower jaw is the most common to receive dental implants. In the
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