Scottish Dental

Combination syndrome – the challenges

14 November, 2014 / editorial
 

With the growth and interest in dental implants it is easy to think that implantology is a faction of dentistry in its own right. This is not the case; dental implants are simply a tool to aid the restoration of the debilitated dentition when conventional dentistry no longer offers an acceptable solution.

For patients with missing teeth, the key to successful treatment has always been and will remain the prosthodontic planning and management. The “surgical implantologist” is a valued member of the restorative team but should not be the first thought when replacing teeth is required. Comprehensive multidisciplinary planning is essential.

This, and the following articles in this series, will focus on some of the challenges in planning and management of patients with problems regularly encountered in general practice.

Combination syndrome (CS) is a term that was first used in prosthetic dentistry by Kelly in 1972¹ to describe the situation where only six to eight lower anterior teeth remain functioning against an upper complete denture. He listed five changes that he felt may be indicative of a “syndrome”. These were:

1. Loss of bone from the anterior part of the maxillary ridge
2. Overgrowth of the tuberosities
3. Papillary hyperplasia in the hard palate
4. Extrusion of the lower anterior teeth
5. The loss of bone under the free end saddle denture bases.

These changes and signs were added to later include:

1. Loss of vertical dimension
2. Occlusal plane discrepancy
3. Anterior spatial repositioning of the mandible
4. Poor adaptation of the prosthesis
5. Epullis fissuratum
6. Periodontal breakdown.(See Fig 1)

There is controversy within the profession whether these signs constitute a “syndrome” and it is more likely that we are simply describing anatomical changes that take place as a result of a specific pattern of tooth loss and the treatment choices made by the patient and the dentist. What is clear, however, is that this is a common situation which is particularly troubling for the patient and a challenge for us to treat effectively.

The most significant factor is the loss of the upper anterior bone, which then dictates the other changes which occur (see Fig 2).

It is also suggested that excessive occlusal forces are a significant contributing factor. Due to the flabby ridge which develops over the premaxillae, there is no stable vertical stop for the denture. Without lower posteriors, the upper denture easily tips, losing the seal on the post-dam. One of the theories about development of the enlarged tuberosities is negative pressure from the tipping of the denture. Of course, disuse over eruption of upper molars prior to extraction could also be a likely cause.The prevalence of CS was documented by Shen² in1989. They examined 150 consecutive complete maxillary edentulous patients, a group including complete upper and lower denture wearers, upper against lower complete dentition, upper against unilateral lower tooth loss and upper against bilateral posterior tooth loss.

They found:

1. The incidence of CS in the maxillary complete denture population was 7 per cent
2. The incidence of CS in maxillary denture opposed by natural anterior mandibular teeth was 24 per cent.

The numbers were not great but the trend certainly exists.

Like Kelly before, Shen also found that the presence or absence of a removable lower partial denture (RPD) has little or no effect on preventing the problem.

This article looks to explain how the situation occurs, what can be done to prevent it in the first place and, once realised, the options for managing it.

The timeline for tooth loss for heavily restored dentitions and especially periodontal patients, seems to follow a similar pattern: loss of lower molars, upper molars, upper interiors and lastly

lower anteriors. From both perspectives this makes sense: the posterior teeth have the most complicated anatomy, are the most challenging to restore and for 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 scaremongering. Kiliaridis³ reported that tooth movement of more than 2mm only occurs in 25 per cent of situations 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 1 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 periodontal breakdown. The key is the susceptibility to periodontal 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 compensatory 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, sometim
es bringing bone with them but often with pneumatisation 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:

1. 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 anteriors with fixed bridgework, or implant supported, before resorption and fibrous replacement takes place.

Periodontal patients are the most challenging, as investing in good restorative treatment on questionable teeth involves considerable skill, both in terms of communication and multidisciplinary restorative techniques.

Acceptance of conventional treatment options can be aided by provision of hybrid Maryland bridges or aesthetic (no visible clasping) cobalt chrome dentures and periodontal splints.

The hybrid Maryland bridge involves minor preparation of the abutment teeth to accept rests and guide planes. Crucially with this type of Maryland an adhesive cement is not required and a simple glass ionomer can be used (see Figs 6 and 7).

Arcylic dentures, while useful as interim prostheses and to allow a patient to become accustomed to managing a denture, are rarely capable of providing adequate stability and posterior support. If bone resorption is to be kept to a minimum, it is essential that lateral movement of the denture is prevented, this is most predictably achieved with a well-designed RPD using guide planes and lock-in rest seats.

Where necessary, undercuts can be created on teeth for clasps using composite resin. The RPD must extend onto the most resorption resistant areas – the retromolar pads and buccal shelves (see Fig 8).

As noted by Jameson⁵, hyperfunction of the remaining anterior teeth should be avoided through correct adjustment, and maintenance of the occlusion.

In the next article we will look at how the CS patient can be managed both by conventional means and with the help of dental implants.

References:

1. Changes caused by a mandibular removable partial denture opposing a maxillary complete denture. Kelly.E, J.Prosthet Dent, 1972
2. Prevalence of the combination syndrome among denture patients. Shen.K ,J.Prothet Dent, 1989
3. Vertical position, rotation and tipping of molars without antagonists Kiliaridis et al, Int J Pros 2000
4. A review of the shortened dental arch concept focusing on the work by the Kayser/Nijmegen group Kanno and Carlsson, J.Oral Rehab 2006
5. Combining fixed and removable restorations with linear occlusion in treating combination syndrome: a discussion of treatment options Jameson WS, Gen Dent. 2003.

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