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Microleakage may be defined as the passage of bacteria, fluids, molecules or ions between a cavity wall and the restorative material applied to it. Many techniques have been devised to test the cavity-sealing properties of restorations both in vitro and in vivo . These techniques include the use of dyes, radioactive isotopes, air pressure, bacteria, neutron activation analysis, artificial caries and scanning electron microscopy. Some form of thermal stressing has frequently been included in the experimental protocol. Research has shown that freshly packed amalgam restorations leak but that this leakage tends to decrease as fillings age. Cavity varnishes and liners reduce initial leakage of the material. Many of the tooth-coloured restorative materials in common use have been shown to leak. Acrylic restorations appear particularly susceptible to leakage after thermal stressing. There is some evidence that the newer composite materials may form a good cavity seal.

Comparable flap operations incorporating curettage and osteoplasties were performed in 17 patients on opposite sides of the same jaw on separate occasions. For one side a cover of phenoxymethyl penicillin 250 mg q.d.s. for 5 days commencing at the time of operation was given and for the other side a placebo was used. Healing was more advanced at 1 week after operation and there was less post-operative discomfort during the first week when the penicillin cover was used. There was a tendency towards less facial swelling when penicillin was administered but the difference was not significant.

The aim of this study was to compare the conventional visual and tactile method of detecting carious dentine during cavity preparation using a mirror, probe and excavator with a visual method enhanced by a dye. The dye, 1% acid red in propylene glycol, was used on 100 cavities prepared by dental students and passed as clinically satisfactory by their teachers. Results showed dye stain at the enamel-dentine junction in 57 cavities (57%) which had been assessed as caries-free in this area using conventional visual and tactile means. Subsequent laboratory work on extracted carious teeth confirmed histologically that the dye stains demineralised dentine. If clinicians consider it important to render the enamel-dentine junction caries-free, it might be prudent to use the dye as an aid to diagnosis in this area.

Since the invention and application of rotary instruments, the operative treatment of carious lesions has often resulted in considerable removal of tooth structure. More recently, newer techniques for removal of carious dentine have been developed in an attempt to minimise this excessive tissue loss. The following article reviews and discusses some of the techniques available to excavate demineralised dentine clinically. These methods can be classified as mechanical and non-mechanical, rotary and non-rotary and include: dental handpieces/burs, manual excavators, air-abrasion, air-polishing, ultrasonication, sono-abrasion, chemo-mechanical methods, lasers and enzymes. The advantages and disadvantages of each technique are discussed.

Dentine becomes infected as a result of caries lesion formation on root surfaces and when lesions progress following cavitation of enamel lesions. However, this infection is unimportant because the driving force for lesion formation and progression is the overlying biofilm. This explains why root surface caries can be controlled by mechanical plaque control and fluoride, and restorations are not needed to arrest these lesions. Similarly, the infected dentine in cavitated coronal lesions does not have to be removed to arrest the lesion. If the lesion is either accessible or opened for cleaning by the patient or parent, the lesion can be arrested. Sealing of infected dentine within the tooth, either by a Hall crown in the primary dentition or by partial caries removal prior to placing a well-sealed filling, will also arrest the lesion. When restoring deep lesions in symptomless, vital teeth, vigorous excavation of infected dentine is likely to expose the pulp and make root canal treatment necessary. Thus ‘complete excavation’ is not needed and should be avoided. CPD/Clinical Relevance: Root surface caries can be arrested by cleaning and fluoride application. Restorations are not essential. Vigorous excavation of softened dentine in deep cavities of symptomless, vital teeth is contra-indicated. It is not needed and increases the risk of pulp exposure.