Restorative Dentistry

Mind the Gap

Why do we like implants? They are a modern, highly successful treatment and allow our patients to avoid the discomfort and limitations of wearing dentures and good practice builders once we have learned the techniques.

As an example, I should like to consider the case of a maxillary lateral incisor that has been root filled, then apicected but has then developed a periapical abscess and requires extraction. Conventional wisdom says, extract the tooth, allow some months for healing then implant osseointegration, and meanwhile restore aesthetics with a removable partial denture, the so-called flipper. Again I ask myself why, when we want to prevent the patient having to wear a denture, this is the very object we provide for several months. I believe we can and should do better.

The first tip relates to the previous apicectomy, which may have left a fenestration in the labial plate when there has been healing by fibrous tissue rather than by new bone. If this is not diagnosed then, when the implant is placed, it will fail, and yes I have made and learned from this mistake. Once the tooth has been atraumatically removed gently probe the socket for the integrity of the labial plate. If there is a palpable fenestration or there is doubt it is a wise move to place bone chips into the socket and leave them 4 – 6 months to form the scaffold for new alveolar bone before placing the implant. A visual check of the labialplate at implany placement can also be beneficial, especially as some authorities advocate always placing bone grafting materials on the labial plate.

The necessary treatment time delays mentioned above can be very frustrating for patients who have to wear a denture. There is an alternative as described below. There are two clinical presentations: (a) if the tooth needs extracting or (b) the tooth has already been extracted.

Case A

Here before the tooth has been extracted take an impression of the palatal surface using a small amount of impression putty, and using your thumb, move a little material over the incisal edge until it covers not more than 2mm of the labial face.

Now extract the tooth as atraumatically as possible. The next stage is haemostasis which can be achieved by any or all of the following, local anaesthetic injection into the gingival papillae, placing haemostatic sponge into the socket if there is room or pressure. The next stage is to apply rubber dam. If available, air abrade the interproximal surfaces of the adjacent teeth to produce a low energy surface then acid etch in the usual way. Measure and cut off a small piece of composite reinforcement material (I always used ‘Everstick rod’ Sticktech, Turku, Finland) and set aside. Now replace the putty matrix and the palatal surface and make sure it is very firmly held in place.

NB if you do not do this the resulting pontic will be high on the bite and likely to fracture off the first time the patient bites together. Whilst still holding the matrix firmly in place, fit the reinforcing rod between the contact points, apply a small amount of flowable composite to each end, and get your nurse to tack cure the rod in place for 5 seconds.

The next stage is to create the palatal surface by syringing in more flowable composite and tack curing. The hardest place to reproduce well is the incisal edge, and that is why it is essential in making the matrix that an accurate impression of this area is taken first. Again tack cure the area. You can now remove the matrix. The next stage is to stretch the rubber dam in a labio-palatal direction between your index finger and thumb. The dam acts as a separator between composite and mucosa. Apply increments of filled composite to fill the space.

I found it essential to have my nurse hold out a pad of different coloured filled and flowable composites in one hand whilst holding the curing light in the other and tack curing as the pontic is built up. By the time this process is completed and the labial shape created do not be surprised if the small muscles in your thumb particularly are feeling the strain. Once you are satisfied with the form of the pontic your nurse can fully cure out the composite for you. Remove the rubber dam and ask the patient to close slowly and carefully onto articulating paper to mark where occlusal equilibration is required. The pontic can then be finally polished, and if you have the material available sealed with a clear glazing composite.

Case B

In this case the tooth has already been extracted and the patient may be wearing a denture. Ask you technician to either fit a denture tooth in place on the B set of study models (see Model Practice) or wax up a tooth to the correct occlusion. Make the palatal matrix and proceed as before.

In each case it is easy to remove this pontic when the time comes using forceps. Should it require replacement then the interproximal surfaces of the adjacent teeth can be cleaned (I used air abrasion for this), re-etched and the pontic rebonded in place using a small amount of flowable composite cured by your nurse.

Occasionally you may need to make an etch retained bridge of a more permanent nature. This is easy if the tooth to be replaced is missing, but what if it is not? What are you going to advise a patient who adamantly refuses to live with either a denture or a space? About 25 years ago I faced just such a demand and was challenged to find a solution. In those days the standard etch bridges were metal based of Maryland or Rochette design – composite reinforcement was in its infancy. The key question is therefore how to ensure an absolutely accurate interproximal fit as adjusting metal was clearly not an option. If we think laterally for a few minutes, then when we have to add a tooth to a denture for an immediate replacement, what percentage fit perfectly on first trial into the mouth without adjustment? In my experience about half, and this is predicated on the judgement of your technician in sectioning the model. The tendency is always to remove that little bit more plaster to ensure there will not be a gap, a practice we cannot accept in the case we have to restore. However, there is a solution if we think outside the box.

1. What do we have to achieve?
2. An absolutely accurate impression of the interproximal surfaces of the adjacent teeth and thus the width available for the pontic.
3. How can we achieve this goal easily?
4. Take your air turbine, insert a long thin diamond bur and remove the mesial and distal surfaces on the tooth that you are going to extract until the contact points have been cleared by at least 1 mm starting from the palatal aspect. Now take your working impression. This removes the need for any educated guesswork by your technician who now has just the fit surface to the mucosa to remove from the working cast in order to make your bridge.

Palatal view – Incisal view

The tooth to be extracted can then be temporarily restored to stabilise the space and recreate reasonable aesthetics by etching and bonding into place composite to replace what you sliced away. In these cases I always wanted the bridge back from my technician within a week just to be on the safe side – but see ‘A Cunning Little Plan’ There will be gingival recession and a gap will appear between the mucosa and the fit surface of the pontic over time. In my case above my patient had a low lip line and accepted the result which was still functioning over 10 years later.

Now I would use reinforced composites bridges rather than metal backed for these case, .not least because the light transmission characteristics and therefore the aesthetic result are superior. It is also possible, using the right materials to bond further composite to the pontic.

In this next case (Fig 3), my patient had an Angles Class III occlusion, some periodontal disease with significant bone loss around her maxillary molars, slightly mobile central incisors, and a demand that she wished to have her instanding lateral incisors brought labially into the arch. Orthodontics had been considered, but there were issues about both the time such treatment would take and the bony support for anchorage posteriorly. I was asked to provide an answer. The technique here was to use the B set study models to make a wax mock up of the possible result. Once patient consent had been given, I prepared the UR2 and UL2 as described in case A above, and made two separate immediate bridges bonded to the central incisor and canine (Fig 4). Purists may claim that I should only have used the canine as an abutment; my reply I made a splint bridge.