Letter to the Editor, "Sjögren's Disease Is Not a Clinical Risk Factor for Periodontitis".

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The MemoFlex II, a non-robotic approach to follow-the-leader motion of a snake-like instrument for surgery using four predetermined physical tracks.

The fields of Minimally Invasive Surgery (MIS) and Natural Orifices Transluminal Endoscopic Surgery (NOTES) strive to reduce the level of invasiveness by entering the body through smaller incisions and natural orifices. Hyper-redundant snake-like instruments can help in this pursuit of reducing invasiveness. Such instruments can pass along multi-curved pathways through the body without any support or guidance from its anatomical environment. In this way, the width of the surgical pathway and thus the invasiveness of the procedure can be reduced significantly. This is referred to as Follow-the-Leader (FTL) motion. Generally, surgical instruments intended for FTL-motion are robotic systems that require medical grade actuators, sensors, and controllers, driving up costs and increasing their footprint in the operation room. Our goal was to discard the need for these elements and develop a non-robotic instrument capable of FTL-motion along pre-determined paths. A proof of concept prototype called MemoFlex II was developed, consisting of a cable-driven hyper-redundant shaft that is controlled via four physical tracks. The MemoFlex II was able to perform 3D FTL-motion along pre-determined paths. Among other things, this study reports on a Ø8 mm shaft containing seven segments and 14 degrees of freedom (DOFs) following several multi-curved paths with an average maximal footprint between 11.0 and 17.1 mm.

Senescence rates in patients with end-stage renal disease: a critical appraisal of the Gompertz model.

The most frequently used model to describe the exponential increase in mortality rate over age is the Gompertz equation. Logarithmically transformed, the equation conforms to a straight line, of which the slope has been interpreted as the rate of senescence. Earlier, we proposed the derivative function of the Gompertz equation as a superior descriptor of senescence rate. Here, we tested both measures of the rate of senescence in a population of patients with end-stage renal disease. It is clinical dogma that patients on dialysis experience accelerated senescence, whereas those with a functional kidney transplant have mortality rates comparable to the general population. Therefore, we calculated the age-specific mortality rates for European patients on dialysis (n=274 221; follow-up=594 767 person-years), for European patients with a functioning kidney transplant (n=61 286; follow-up=345 024 person-years), and for the general European population. We found higher mortality rates, but a smaller slope of logarithmic mortality curve for patients on dialysis compared with both patients with a functioning kidney transplant and the general population (P<0.001). A classical interpretation of the Gompertz model would imply that the rate of senescence in patients on dialysis is lower than in patients with a functioning transplant and lower than in the general population. In contrast, the derivative function of the Gompertz equation yielded the highest senescence rates for patients on dialysis, whereas the rate was similar in patients with a functioning transplant and the general population. We conclude that the rate of senescence is better described by the derivative function of the Gompertz equation.

[Erosion effect of a newly developed soft drink]. / De erosiepotentie van een nieuwe frisdrank.

In this article, the erosion effect of a newly developed soft drink available in 3 different flavours is compared with the erosion effect of some common soft drinks. Several basic parameters of the soft drinks were determined: pH, titratable acidity, and the calcium as well as phosphate concentration. Three methods were used to assess in vitro the erosion depth of the soft drinks in enamel specimens. Erosion depth is defined as the mean height of lost enamel. The methods used were atomic absorption spectroscopy for calcium loss, a colorimetric ammonium molybdate method for phosphate loss and non-contact profilometry for enamel volume loss. The newly developed soft drink realized statistically significantly less erosion depth when compared with cola and apple juice and statistically non-significantly less erosion depth when compared with orange soda.