Cellular fluid shear stress on implant surfaces-establishment of a novel experimental set up.

BACKGROUND: Mechanostimuli of different cells can affect a wide array of cellular and inter-cellular biological processes responsible for dental implant healing. The purpose of this in vitro study was to establish a new test model to create a reproducible flow-induced fluid shear stress (FSS) of osteoblast cells on implant surfaces. METHODS: As FSS effects on osteoblasts are detectable at 10 dyn/cm2, a custom-made flow chamber was created. Computer-aided verification of circulation processes was performed. In order to verify FSS effects, cells were analysed via light and fluorescence microscopy. RESULTS: Utilising computer-aided simulations, the underside of the upper plate was considered to have optimal conditions for cell culturing. At this site, a flow-induced orientation of osteoblast cell clusters and an altered cell morphology with cellular elongation and alteration of actin fibres in the fluid flow direction was detected. CONCLUSIONS: FSS simulation using this novel flow chamber might mimic the peri-implant situation in the phase of loaded implant healing. With this FSS flow chamber, osteoblast cells' sensitivity to FSS was verified in the form of morphological changes and cell re-clustering towards the direction of the flow. Different shear forces can be created simultaneously in a single experiment.

Comparative clinical evaluation of different epinephrine concentrations in 4% articaine for dental local infiltration anesthesia.

OBJECTIVES: The aims of this study were to compare and evaluate the clinical anesthetic efficacy of five 4% articaine solutions with and without epinephrine in pulpal anesthesia after infiltration. MATERIALS AND METHODS: In a randomized, double-blinded, crossover study, ten volunteers received local anesthesia infiltration in the maxillary right central incisor with five different solutions (4% articaine + epinephrine 1:100,000, + epinephrine 1:200,000, + epinephrine 1:300,000, + epinephrine 1:400,000, without epinephrine). Electronic pulp tester was used to calculate the onset, utilization time, time to recede, and the surface integral under the time-effect curve. Additionally, cardiovascular parameters and post-experimental soft tissue anesthesia were examined. RESULTS: Onset as well as time to recede was not influenced by the epinephrine concentration. When using the epinephrine-free agent, time to recede was significantly shorter. Upon decreasing epinephrine concentration, duration of pulpal anesthesia and total anesthetic efficacy declined. The shortest time of anesthesia and lowest anesthetic efficacy were seen for the solution without epinephrine. No association was found between the local anesthetic drug and cardiovascular parameters. Soft tissue anesthesia was significantly shorter without epinephrine. CONCLUSIONS: This study shows the substantial benefits of vasoconstrictors in dental infiltration anesthesia. These findings were reflected by means of prolonged and deeper therapeutic effect in a dose-dependent manner. CLINICAL RELEVANCE: Even when utilizing agents with reduced amount of epinephrine, a safe anesthesia is possible. The epinephrine-free solutions resulted in a distinct limitation of utilization time and efficacy.