Scottish Dental

Assessing the options

09 January, 2015 / clinical
 Edinburgh Dental Specialists  

In the last article we explained what combination syndrome (CS) is, the factors leading to the creation of a CS patient, the signs associated and possible preventive strategies. In this article we will look at possible treatment/management options in both conventional and dental implant based dentistry.

The first step in any comprehensive treatment plan is to know exactly what you are dealing with.

The goals in treating the CS patient are:

1. To regain a healthy, stable and functional dentition
2. To achieve the patient’s aesthetic goals
3. To educate the patient on the long-term management of their condition.

As mentioned before, the patient’s primary complaint is usually a loose denture and loss of aesthetics (from not seeing enough of the upper teeth) together with overclosure.

Of course, it is important to gather all information on the biological issues that may be affecting the patient (caries, restorative, periodontal, occlusal, general health etc), but no treatment should commence until the definitive end result has been visualised and agreed. In this way, treatment is not carried out on teeth that, while savable, may perhaps be better lost as part of the overall plan.

When aesthetics are involved, this type of ‘facially generated treatment plan’ can save considerable time and effort.

The facially generated treatment plan

The starting point is to see what the desired aesthetic result would be. Only then can you design a plan to achieve it.

While there are many guidelines to aesthetics and smile design, it is ultimately subjective and wax-ups on models are of limited use as they don’t show how the patient’s lips move and it is difficult for patients to relate them to their situation. If skilled in Photoshop, imaging can be employed.

The simplest planning tool, however, is to set up the upper six to eight denture teeth directly in the patient’s mouth. In this way, it is possible to work with the patient and move the teeth until the patient accepts the result.

As a general guide, (age and gender dependant), aim for approximately 1-2mm of the incisal edges to show at rest and (with normal lip mobility of 6mm) approximately 7-9mm of incisal show during a wide smile. Photographs from before the patient lost their teeth can be especially helpful. Simply bringing the lowers up to meet the new aesthetic design of the uppers (in centric relation) provides the new vertical dimension of occlusion – or shows what additional treatment may be required to realise the aesthetic goals.(Figs 1 & 2)

Speech can be assessed and it is possible to see immediately if any over-eruption of the lowers has occurred and if it is acceptable or not. Often an over-erupted lower anterior segment will be accepted as a compromise once the uppers can be seen again. If the compromise is still unacceptable, then reduction of the lowers is required. (This could be through restorative, orthodontic or surgical means).

If the lowers are sufficiently compromised to require removal, and implants are being considered, it is important that the surgeon is advised to reduce the alveolar ridge to provide sufficient restorative space. Failure to do so is a common mistake and can result in an unacceptably thin over-denture or bridge, difficult oral hygiene management and frequent fractures.

Once the aesthetic goals have defined the space requirements for upper and lower, it is possible to plan the restorative phase. For the majority of cases, an upper complete denture against a lower bilateral, free-end saddle denture will be the simplest conventional solution. A number of considerations are required:

Upper complete denture

Impression technique for flabby anterior ridge. Various options are suggested by prosthodontists with the goal of any technique being to provide a good fitting, stable and retentive base. For a conventional upper denture impression, a mucocompressive technique (close-fitting special tray) is thought to provide optimal loading and, therefore, comfort during function.

The flabby ridge, however, can cause a displacing effect if it is compressed during the impressing, so a technique that allows it to remain non-compressed is recommended – a mucostatic technique. A combination technique is therefore recommended.

Possible solutions are:

1. Two-part special tray
2. Open special tray and plaster of paris
3. Spaced special tray
4. Perforated special tray over the flabby ridge.

The simplest is the spaced/perforated tray – the number of spacers depend on the material being used; for a monophase silicone or polyether – one spacer over the palate and ridges and three (with perforations) over the flabby ridge. Use of green stick compound over the post dam and to create a ‘stop’ together with tuberosity border moulding. Once taken, the impression should be reseated to confirm good retention (Fig 3).

Lower partial denture

If an upper complete denture is the treatment of choice, then posterior support is essential and a lower shortened arch should not be accepted.

It doesn’t matter how good a fitting upper 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:

1. 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, guideplanes 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, impression material is used for the impression. At the same time, the bite registration in centric relation can also be taken (Figs 4 & 5).

The above techniques will allow fabrication of stable retentive bases, the final challenge is in managing the occlusion. Anticipating bruxing or clenching, it is important to have the dentures constructed with a degree of anterior open bite. Generally, about 1mm is sufficient not to impose on speech. Balanced occlusion with shallow cusps helps reduce the destabilising 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:

1. 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).

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 multitude of factors including: bone loss to date, aesthetic goals, functional goals, budget, parafunctional history, medical history, etc.

A number of studies¹ 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 iatrogenically create a combination syndrome if the patient elects, or is led, to have a fixed implant bridge (all on four type restoration) in the mandible.

The edentulous lower jaw is the most common to receive dental implants. In the class III mandible, there is often an abundance of bone anteriorly and provision of a fixed bridge – with implants placed between the foramina – while resolving the problem of the loose lower denture will, due to the point of force application in occlusion, being on or anterior to the upper ridge result in tipping and loosening of the upper denture. In such a situation, patients should either be guided to a lower over-denture restoration (for simple posterior support from the mandibular residual ridge and denture) or consented to the lower bridge on the understanding that implant treatment will be required in the upper (Fig 9).

Alternative option

If the patient is willing to accept the lower shortened arch, then an entirely different treatment plan may be followed. Providing there is sufficient bone remaining in the upper anterior maxillae, then splinted implants in the upper may be the only treatment necessary (Fig 10).

With a fixed (or removable) splinted implant supported restoration in the upper, posterior support is no longer necessary, as the potentially damaging force vectors from the lower anteriors can be negated and shared across the maxilla. Being osseointegrated and having no periodontal ligament, the implants will not drift and potential ‘off axis’ loading of the implants is not in itself likely to compromise the implant bone support².

It is important to place, and splint, as many implants as necessary to mechanically protect against functional and potential parafunctional forces.

When there is sufficient bone, this treatment option is often the one of choice as many of the patients criteria are addressed:

• Aesthetics improved
• No moving upper denture
• Fixed bridge that doesn’t come out
• Palate exposed
• No lower denture/any denture required
• Cost effective
• Long term.

By no means comprehensive, the above discussion shows that potentially crippling bone loss can be avoided through good restorative treatment and, should the CS patient present, then treatment options both conventional and implant supported are available.

About the author

This article was submitted by Edinburgh Dental Specialists. Please contact us if you would like further information or advice on managing similar cases, tele-dentist@edinburghdentist.com

References

1. The combination syndrome: a literature review. Palmquistetal J. Prosthet Dent 2003
2. Tilting of posterior mandibular and maxillary implants for improved prosthesis support. Krekmanov L et al. JOMI 2000

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