P. Leppard

Tooth extrusion effects on microvessel volumes, endothelial areas, and fenestrae in molar apical periodontal ligament

Extrusive tooth loads, simulating short-term orthodontic movements, have not previously been used for transmission electron microscopic quantification of their effects on the periodontal ligament vessels. In this study, a continuous extrusive load of 1.0 N, applied to the rat maxillary first molar for 30 minutes, produced statistically significant changes in the microvascular bed of the tensioned apical periodontal ligament. The mean vascular volume, as a percentage of apical periodontal ligament volume, increased (p less than 0.01) in postcapillary-sized venules, venous capillaries, arterial capillaries, and terminal arterioles from 16.6% to 22.3%, 2.0% to 2.7%, 0.4% to 1.0%, and 1.0% to 2.5%, respectively. Mean endothelial surface area per cubic millimeter of apical periodontal ligament tissue increased (p less than 0.01) in postcapillary-sized venules from 16.8 to 25.7 x 10(6) microns 2/mm3, in venous capillaries from 3.0 to 4.8 x 10(6) microns 2/mm3, and in arterial capillaries from 0.7 to 1.5 x 10(6) microns 2/mm3. The number of fenestrae per square micron of endothelium in postcapillary-sized venules, venous capillaries, and arterial capillaries showed a mean increase from 0.02 to 0.07, 0.11 to 0.31, and 0.02 to 0.21 fenestrae/microns 2, respectively (p less than 0.01). Fenestrae per cubic millimeter of periodontal ligament tissue also demonstrated a statistically significant increase with extrusion (p less than 0.01) in postcapillary-sized venules from 0.37 to 1.55 x 10(6) fenestrae/mm3, in venous capillaries from 0.27 to 1.34 x 10(6) fenestrae/mm3, and in arterial capillaries from 0.02 to 0.22 x 10(6) fenestrae/mm3. Fenestrae in control vessels had a mean diameter of 54.2 +/- 0.56 nm (SE) compared with 61.1 +/- 0.7 nm in tensioned vessels (p less than 0.01). This investigation demonstrates multiple ultrastructural changes in the periodontal ligament microvascular bed after tooth extrusion.

An analysis of the effect of tooth intrusion on the microvascular bed and fenestrae in the apical periodontal ligament of the rat molar.

An analysis of the rat apical periodontal ligament (PDL) microvascular bed and fenestrae was conducted to evaluate the effect of a continuous 1.0 N intrusive tooth load for 30 minutes. The microvascular bed consisted of postcapillary-sized venules, venous and arterial capillaries, and terminal arterioles. Intrusion produced significant increases (p less than 0.01) in vascular volume for postcapillary-sized venules and venous capillaries in three of the four animals. Arterial capillaries, overall, showed a statistically significant increase (p less than 0.01). The endothelial surface area (micron2 x 10(6)) per cubic millimeter of PDL responded variably in postcapillary-sized venules and venous capillaries but showed a strong trend to increase in arterial capillaries. After tooth intrusion a significant reduction (p less than 0.01) occurred in the number of fenestrae per square micrometer of endothelium in postcapillary-sized venules and venous capillaries. Fenestrae in the control PDL had a mean diameter of 51.5 nm +/- 0.6 (SE), whereas those on the intrusion side were smaller (p less than 0.05), measuring 49.9 nm +/- 0.4 (SE).

A review of the technical features of breast cancer screening illustrated by a specific model using South Australian cancer registry data

This paper illustrates many of the concepts and issues relating to breast cancer screening by reference to a case study of screening in South Australia and by a survey of the mathematical screening models. This work is motivated by the observation that, for some women, the prospects for a breast cancer cure appear to be enhanced if the disease is detected early. We use data from the South Australian Cancer Registry to estimate some of the parameters which describe the pattern of this disease in the South Australian female population, and the underlying model is then used to estimate the impact of various screening designs on the efficacy of a variety of breast cancer screening programmes.

A Note on the Sensitivities of Self-reporting and Screen Detection of Primary Breast Tumours

Screening programs for breast cancer are widely used to reduce the impact of breast cancer in populations. For example, the South Australian Breast X–ray Service, BreastScreen SA, established in 1989, is a participant in the National Program of Early Detection of Breast Cancer. BreastScreen SA has collected information on both screening–detected and interval or self–reported cases, which enables the estimation of various important attributes of the screening mechanism. In this paper, a tailored model is fitted to the BreastScreen SA data. The probabilities that the screening detects a tumour of a given size and that an individual reports a tumour by a specified size in the absence of screening are estimated. Estimates of the distribution of sizes detected in the absence of screening, and at the first two screenings, are also given.