Customising wedges

Wooden wedges are very useful tools in restorative dentistry. They allow for the protection of soft tissues during tooth preparation, retraction of the rubber dam, separation of the teeth to protect the adjacent tooth, seal the matrix band against the cervical margin and separate teeth to allow a contact point to be formed accounting for the thickness of the band, thickness of bonding agent and shrinkage of restorative material.

The issue with most wooden wedges is that they are too large in an occlusogingival direction so tend to displace and deform the matrix band away from the adjacent tooth. This requires some customisation of the wedge to fit each specific cavity that it is being used on. Burnishing the band doesn't tend to overcome this and just leaves a lumpy surface on the interproximal surface. Ideally we want the band sitting passively against the adjacent tooth without having to force it there. 

The next time you prepare a class II cavity, look at the interproximal area from the buccal or lingual aspect. The distance between the base of the interproximal box to the gingiva is about the dimension your wedge needs to be. For deep preparations the wedge will often be too large. Any amount of wedge that sticks above the base of the box will deform the matrix band. The issue can be seen that the preparation is located too close to the gingiva to  place a wedge but it can be seen from the other point of view that the gingiva is located too close to the preparation to allow the wedge to fit. 

 

Figure 1: 1. Interproximal caries necessitating cavity preparation. Begin with the end in mind and thinking about how you will customise the wedge to ensure a good contact and well contoured restoration. In this case, the papilla rises high and will be in the way of fitting a good sized wedge. 2. Schematically, a gingivectomy was performed and the wedge fitted in before preparation. 3. The wedge was modified during the course of tooth preparation.

Rubber dam can assist in retracting the gingiva enough in equigingival margins but subgingival margins usually require some form of gingivectomy to fit the wedge. The wedge itself has some capacity to displace the soft tissue but if it is not seating in well or won't sit below the margin of the cavity, don't hesitate to cut the interdental papilla away.

Once there is space to fit a wedge, pre-wedge the teeth with as large of a wooden wedge that will fit. Hammer that in with quite a bit of force. Failure to push the wedge in at this point will mean all the customisation during the preparation will be in the wrong place on the wedge. When you then go to force it in to separate the teeth for the restoration, you will find that the wedge is impinging on the band again. Teeth need time to separate as the PDL stretches slowly. After opening the enamel with your bur, you can come back and compress the wedge in further. The moisture from the water spray can act as lubricant for the wedge to slip in further and the water can expand the wedge slightly providing further separation. 

Most of the customisation occurs during the cavity preparation. Rotary instruents will cut tooth structure and wood alike and in preparing the floor of your cavity, the wood will be shaped to match the cavity. This is the place that would normally deform the band so has to be removed. This is usually where I would end the customisation and most of the time it would work if I used a separating ring and burnished the band but what I have been doing lately is taking the wedge out and customising it further. I would take the wedge out to allow the band to seat down past the margin but before fitting it back it I would adjust it using a rotary instrument. The part where I have started adjusting is in the buccal and lingual embrasures on the side of the tooth being prepared. You can see a hollowed out area where the preparation is but just adjacent to this, it can get in the way of the band once that is in place. I have found my success increase in gaining a good contact now that I do this. Most of the time if the band is sitting well passively and I think I have good separation of the teeth with a large wedge I will skip using a separating ring. Partly because I think it is unnecesary, partly because it can ruin the buccal and lingual contour of the restoration and partly because they aren't always available in the public clinics. 

 

Figure 2: 1. The customised wedge has removed the superfluous material which allows the band to sit against the adjacent tooth. The distance between the gingiva and the cavity margin determines how thick the wedge will be after customisation. If that dimension is too small the wedge is likely to break on insertion and removal. Gingivectomy may be indicated here. 2. A non customised wedge is sitting up into the cavity and is displacing the band away from the adjacent tooth. Customisation needs to be considered in three dimensions and the wedge material removed from the gingival aspect as well as the buccal and lingual embrasure areas to avoid displacing the matrix band.

 

 If there is insufficient material left on the base of the wedge after preparation it may be that the gingiva is invading into your wedge site too far and is not allowing a large enough wedge to fit. The first wedge can displace the tissues enough to fit an even larger wedge in but if you take the wedge out and it is too weak to be put back in consider a gingivectomy there to allow a larger wedge to fit in. You can customise the wedge again by running a slow speed round bur along the floor of the cavity or it can be estimated and done extraorally.