Adhesive Bridge Preparation

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Dr Muzzafar Zaman Dental Advice

5 min readJun 5, 2020

Closeup / prosthodontics or prosthetic / tooth crown and bridge implant dentistry equipment and model express fix restoration

An adhesive bridge is one that involves no/minimal preparation to the adjacent teeth. This is a huge advantage over a conventional bridge which relies on extensive preparation of the adjacent teeth which otherwise may be healthy.

We also know from long-term studies that 20% to 30% of all prepared bridge abutments will eventually become non-vital and need root canal treatment. This significantly reduces prognosis and there is also a likelihood that the root canal treatment may fail in the future or indeed the abutment which will, therefore, require post-reinforcement.

Post reinforcements, especially on the anterior teeth, are notorious for failing especially when root fractures occur.

An adhesive bridge can involve no preparation whatsoever or very minimal preparation only within the enamel itself. Previously, when the adhesive bridge was advocated, it was common practice to prepare the adjacent teeth.

On upper teeth, this involved preparation to the palatal surfaces and lowers, the lingual surface. The reason why preparation was thought to be needed was to accommodate the occlusion.

The early adhesive bridges had a high failure rate because often preparation went into the dentine in order to accommodate the occlusion. As a result, bridges would fall out and also let’s not forget that there no effective dentine enamel bonding agents like now.

Things have moved on and now it is widely advocated that there should be no preparation. You may ask, what about the occlusion?

When an adhesive bridge is cemented on without any tooth preparation, the lower opposing teeth will initially be in premature and occlusal interference with the upper bridge wing abutment. However, it has been shown that within time, the occlusion will re-adapt and maximum intercuspation will re-occur as before the treatment. This is using the Dahl principle.

By carrying out no preparation whatsoever, this maximises the retention of the bridge wing to the surface of the tooth. It is always better to gain retention from enamel rather than dentine. All studies show that retention to enamel is always much superior compared to retention to dentine.

The retention is gained by etching the enamel with 37% phosphoric acid for 20seconds. It goes without saying that the enamel must be completely free of plaque and a good way of achieving this is simply to scale the surface of the enamel before etching.

Once the enamel is dry then the bridge can be bonded onto the tooth surface. It is also imperative that the laboratory etches the surface of the bridge which is going to be the fitting surface. Whilst you are handling the bridge, you need to make sure that the bridge surface does not become contaminated with saliva.

The process of etching the enamel and the surface of the bridge retailer creates micromechanical retention.

On the surface of the enamel, the enamel prisms are preferentially dissolved creating porosity into which the composite resin will flow. Likewise, the surface of the attached bridge will have a roughened surface onto which the composite resin will flow. As a result, resin tags provided the necessary micromechanical retention.

It is not necessary to prepare grooves or slots onto the tooth preparation as micromechanical retention through etching is sufficient.

Another drawback of preparing grooves or slots onto the tooth preparation surface is that it makes the fitting and fabrication of the bridge more problematic and errors will have increased.

On some occasions, however, it is recognised that a small amount of preparation may be better but it is always imperative that the dentine is not exposed. In this way, the preparation is always intra-enamel.

Another common question that arises is whether two bridge retainers on either side are better than a single cantilever retainer. You would think that retainers on both sides would be more effective however studies show that the single cantilever adhesive bridge retainer is more effective.

Of course, you need to take into account the size of the tooth you are replacing in relation to the surface area of the adjacent tooth you are using for retention. Although we talked about the occlusion on the bridge retainer, it is important that the occlusion on the bridge pontic is none or very minimal. This needs to be checked in normal intercuspation but also in lateral and protrusive/ intrusive movements of the mandible.

If the surface of the tooth that you are preparing has a restoration, it is better to replace the restoration if you think that it will need replacing soon. Also, a new composite restoration will bond on better than an old composite restoration.

In conclusion, the adhesive bridge preparation should be non-prepared -and within enamel if anything. No grooves or slots are required at all. Initially, there will be occlusal interference however using the Dahl principle, the normal intercuspation of the teeth will re-establish. The maximum surface area of the abutment should be used however it can stop short of 1 to 1.5 mm of the palatal or lingual surface for aesthetics.

In conclusion, the adhesive resin-bonded bridge is extremely effective and a much less invasive procedure than other forms of tooth replacement such as fixed bridges and dental implants. They also do not have all the disadvantages of acrylic dentures. Adhesive resin-bonded bridges are easy to implement as no or very little tooth preparation is required.