CPD article
patients to look after. They are the first affected by loss
of support; upper molars having more roots are maintained longer than the lowers. The vector of force from lower anteriors against upper anteriors is favourable for the lowers and unfavourable for the uppers – whether it’s periodontal bone loss or post retained crowns. Patient choices, how they are
guided during the tooth loss process and their occlusion have a combining effect on the healing of the residual alveolar ridge. When a patient first starts to lose posterior teeth they, understandably, wish to avoid a removable denture, and fixed bridgework may not be chosen either because they, or the attending clinician, feel it is not worthwhile due to compromised abutments or simply not necessary. For one or two teeth, this is quite
acceptable and indeed replacing teeth simply to maintain “posterior support” or to prevent other teeth moving is rarely necessary and can be unnecessary scaremon- gering. Kiliaridis3 reported that tooth movement of more than 2mm only occurs in 25 per cent of situa- tions and so a policy of replacing all missing teeth to prevent movement is not justified. There comes a point when the
occlusion moves from being stable to unstable, at which point the loss of posterior support is very much an issue. In terms of when this happens, there are again a number of factors: Kayser and Nijmegen4 have shown that two occluding posterior units on either side (all premolars) in a class ı occlusion with periodontally sound teeth, will provide predictable long-term support and acceptable function – the shortened dental arch concept (SDA) (see Fig 3). In this case, the idea of providing
restorations to increase posterior support is incorrect and largely unnecessary. Here, the indication for restoration provision would be at the “request” of the patient. There are, of course, many
patients with extreme shortened arches who do not exhibit any problems whatsoever, no concerns over function or aesthetics and no mobility of teeth or perio- dontal breakdown. The key is the susceptibility to periodontal
Hybrid Maryland with guide planes and rest seats Fig 7
Fig 8
Lower aesthetic RPD design with saddle impression trays
Fig 9 Lower aesthetic RPD try-in
“Denture fabrication has a number of specific challenges”
disease and what the patients do with their teeth. Once the upper anteriors are lost,
the upper ridge is tasked with taking the load from the lower anteriors through the complete denture. In susceptible individuals, the residual ridge is slowly replaced with fibrous tissue. Clinically, these patients complain that their upper denture is loose, eating is difficult and their appearance is no longer satisfactory as the teeth are disappearing under their upper lip (see Fig 4). During the process of the loss
of the upper teeth and destruction of the alveolar ridge, the lower anterior ridge exhibits compensa- tory alveolar growth where the remaining lower teeth erupt with the alveolar ridge. Here, patients will often complain that they “see too much” of the lower teeth. The tuberosities will have
enlarged, sometimes bringing bone with them but often with pneuma- tisation of the sinuses (see Fig 5).
Resolving the problems at this
stage can be very demanding. Denture fabrication has a number of specific challenges and aesthetic improvement is often limited by the new anatomy. Furthermore, these are the most difficult problems to surgically resolve.
Prevention Trying to prevent patients from reaching this stage of tooth loss is critical. Things that should be considered are: ı. Education about their situation in order to accept tooth replacement 2. Treatment and stabilisation of any periodontal disease 3. Provision of tooth replacement by conventional means – conventional bridges, Maryland hybrid bridges or cobalt chrome dentures 4. Maintaining roots in posterior mandible and anterior maxillae for ‘overdenture’ abutments 5. Replacement of missing upper
Continued » Scottish Dental magazine 57
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