Abstract
The complexity of the reactions required to equilibrate a simple force applied to a tooth have been shown. The elastic response which might be expected when an implant is subjected to lateral loads has been discussed. A lateral load has been shown to induce maximum stress concentrations at the alveolar bone crest. The mechanical factors which effect the stresses produced by a tranverse load have been studied in the laboratory experiments using photoelastic techniques and a double exposure radiographic procedure which was devised. It was found that the maximum stresses were generated at the alveolar crest and that the magnitude of these local stresses was proportional to the applied moment and related to the flexural stiffness of the implant and to the difference in modulus between the implant material and the bone. An analysis of two hundred and eighty two functional implants in vivo has shown that bone resorbtion had occurred in the alveolar bone crest in the majority of cases. There is some evidence that a methodical assessment of specified mechanical and biological factors provides a criteria for determining whether a particular implant is likely to be successful. The problems of obtaining data from radiographs by visual assessment have been discussed. The use of densitometric techniques to obtain data from processed x-ray films of bone sites has been studied. A simple formula has been shown to be sufficiently good representation of the x-ray absorbtion of aluminium. The absorbtion behaviour of cortical and cancellous bone was calibrated against an aluminium wedge. The effect of x-rays passing through two dissimilar materials has been shown. Finally there is some evidence that the detection of flaws in the cancellous bone may be improved by the use of densitometric techniques.