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An artificial caries technique, using a diffusion controlled acidified gel, was used to create in vitro artificial lesions adjacent to composite restorations. Prior to gel immersion, test specimens were temperature-cycled in a machine designed specifically for this purpose. Examination of control specimens showed little evidence of leakage, the presence of a cavity wall lesion being used as an indication of leakage. Compared to the controls, the test specimens showed either a reduction or no change in leakage pattern. It is suggested that thermal percolation may not be of clinical significance in relation to composite restorations.

A total of 327 post-retained crowns were examined radiographically and a number of features were assessed including the length of post, length of remaining root filling, periapical condition, fit and angulation of the post and quality of root filling. The post length was equal to or greater than that of the crown in only 34% of cases. Although the majority of posts fitted well laterally, 43% did not extend longitudinally as far as the end of the prepared post hole. Some 20% deviated from the line of the root canal but the number of actual lateral perforations was small. A total of 47% of the teeth had areas of radiolucency around the root apices. A majority of root fillings were judged to be unsatisfactory and there was no radiographic evidence of any root filling at all in nearly 10% of cases.

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