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Summary The aim of this study was to evaluate objectively and clinically the relative improvement in retention forces of complete dentures with the use of three proprietary denture fixatives. Using the UCL Retentiometer, retention forces of ill‐fitting maxillary complete dentures were measured with saliva alone as the interface medium and with the use of the three test denture fixatives in edentulous subjects over a peroid of 6 h. Results showed that forces with saliva alone were consistently and significantly lower when compared with the forces measured at any test period with the use of the test fixatives. A sixfold improvement in forces from the salivary baseline values was observed when these materials were used. However, the test fixatives showed substantial variations in retention forces depending on the physical formulation of the material. Whilst the powder Variety was effective immediately after its application, retention forces with the liquid and paste materials did not peak until 3 h post‐insertion. Measurements at 6 h post‐insertion stage showed that the powder fixative was the least effective of the three materials. This was mainly attributed to the rapid washing of the active ingredients by saliva because of the absence of oily base present in the paste and liquid materials.

The non‐linear response of the tooth to external stresses is due to the interaction of the fibrous, cellular and vascular elements of the supportive tissues. In this study the relaxation of the central incisors after the suden removal of axial forces of 2.5 Newton was investigated in three monkeys. The displacement‐time curve was analysed using a technique of exponential curve fitting. Analysis shows that the periodontium is viscoelastic in nature and may be represented by three and possibly five Voigt elements. Comparison of the upper and lower incisors indicate that while the same basic processes are active in both mandible and maxilla they are different in magnitude. In the case of the fastest acting Voigt element the response is more rapid for lower teeth than for upper ones, corresponding either to less damping or a stronger spring constant. This difference in magnitude is presumably due either to differences in the architecture of the periodontium and alveolar bone or to the local blood supply. The authors are indebted to Dr. M. Braden of the London Hospital Medical College for his advice and guidance. Thanks are due also to members of the Department of Medical Physics of the University College Hospital, particularly Mr. J. S. Clifton for his encouragement, Mr. M. Conway and Mr. R. Favre for the construction of the force applicator and Mr. K. J. Cassell for his assistance.

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