Clinical studies

There has been a considerable amount of work done to evaluate the success or otherwise of DBAs in clinical studies. However, one of the great problems has been that many of the DBAs have been considerably changed or a new material introduced by the time these studies are completed or published. Many of the studies have also been performed on NCCL, which means the outcomes cannot really be applied to restorations in other parts of the mouth because NCCL dentine is usually sclerosed and therefore different from that of an intracoronal cavity. However, these outcomes will provide some indication as to whether the DBA is able to achieve a durable bond under very harsh conditions. Since the early materials were introduced, the retention rates of the DBAs to sclerosed cervical dentine have steadily improved to extent that retention rates are little different from GICs [79].

With regard to clinical studies on posterior teeth restored with a DBA, there is still little evidence available. It would seem though, that clinical studies of resin composite restorations are showing evidence that when placed in the correct manner and the patient has a low caries rate, restoration survival is approaching that of amalgam [30].

When it comes to the use of DBAs, it is important to follow the manufacturers' directions carefully. Overetching can create a situation where there will potentially be a region of poorly or uninfiltrated dentine. This zone may be susceptible to acid or enzyme attack from oral bacteria, hence leading to bond failure [82].

In the case of the self-etching priming materials, this is not believed to be a problem. However, the converse problem may occur: as mentioned, the dentine or smear layer may neutralize the etching primer if the primer has a relatively high pH. The anecdotal evidence would seem to indicate that gentle agitation of these solutions may assist with the etching. However, there are no research data to support this [35, 79].

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