Jawbone reduction in immediate prostheses. A comparison between overdentures and complete dentures

In a randomized controlled clinical trial 74 patients who required immediate dentures were randomly treated with immediate overdentures on 2 lower canines or immediate complete dentures. Mandibular bone reduction was measured using oblique lateral cephalometric radiographs made at base-line and the results compared with those of one year and two years after denture treatment. Analysis of the data showed that the average bone reduction in the lower canine regions in the first year was 0.75 in the immediate overdenture group and 1.90 mm in the immediate complete denture group. In the posterior parts of the mandible the bone reduction was respectively 0.77 and 1.77 mm. The differences were statistically significant in all measured regions. The differences in the first two years were significant in all regions except the molar region. Retention of roots of canines beneath a mandibular denture in immediate denture patients, even when they were in poor condition, reduced the collapse of the alveolar processes in all region of the mandible.     

Projection techniques in dental radiology

The radiographic technique largely determines the amount of information that can be obtained from a (dental) radiograph. Therefore an adequate choice of the projection technique is at least as important for dose reduction as the various measures for radiation protection that can be applied during the exposure.     

Dose distribution in tissues

Biological effects of ionising radiation are dependent on the distribution of doses in tissue. In this article parameters influencing the distribution of dose in tissue are discussed with emphasis on intraoral and rotational panoramic radiography. For both examinations the probability to develop stochastic effects is estimated. For intraoral radiography the probability ranges from 0.1 to 0.3 per million exposures and for rotational panoramic radiography from 0.4 to 0.8 per million. For the whole Dutch population the probability to develop stochastic effects is 0-2 persons per year and 0-1 person per year respectively. Dental radiography is therefore justified if further diagnostic information is to be expected and exposure circumstances are optimal.     

Interhemispheric steal. An experimental study

In 21 cats the pressure in the occluded middle cerebral artery (MCA) was recorded by way of a catheter, introduced in the most proximal portion of this artery by way of the transorbital approach. The effect of temporary occlusion of the ipsilateral and contralateral common carotid artery on the pressure in the occluded MCA was studied. The results seem to prove the existence of the so-called "interhemispheric steal" syndrome.