The purpose was to determine the effect of different environments (artificial saliva, human saliva, distilled water, dry storage) on frictional forces between various tribological systems made from self-ligating brackets in combination with stainless-steel wires (dimensions: 0.016″×0.022″, 0.018″×0.025″ and 0.019″×0.025″). An universal testing-machine applied a normal force of 1 N. Two-way ANOVA and Tukey post-hoc tests (α=5%) were used. Saliva had significantly higher frictional forces (p<0.001). Yet, the influence of the media depends on the wire dimensions. The results were not as straightforward as in 0.018″×0.025″, which had a clear order (dry storage
The purpose of this study was to investigate the effects of curing mode with a high-power LED curing unit (VALO) in terms of microtensile bond strength (μTBS) to dentin and microhardness of two dual-cure resin cements. Panavia V5 (V5) and Rely X Ultimate (RXU) were polymerized using one of three curing modes with VALO or self-cure mode to bond a CAD/CAM resin block to a flat dentin surface. Specimens were sectioned and subjected to μTBS test. Vickers hardness values of V5 and RXU were also measured. Two-way ANOVA indicated curing mode and resin cement affected μTBS. For self-cure mode, V5 had significantly higher μTBS than RXU (p<0.05). Higher irradiance did not always provide higher μTBS of dual-cure resin cement to dentin. One-way ANOVA indicated the curing modes affected microhardness of each cement. As for microhardness of RXU, there were significant differences between selfcure mode and light cure modes (p<0.05).
The aim of the present work was measuring the effect of varying normal forces on frictional forces applied to different bracket types in combination with archwires made of NiTi and stainless steel of variable cross section. The measurements were carried out in artificial saliva. Three-way ANOVA and Bonferroni post-hoc tests (α=0.05) were applied. Except for one subgroup the combination of normal force, bracket system and wire dimension had significant effect on friction (p<0.001) as friction increased with increasing normal forces. Only moderately tied ligatures or passive self-ligating brackets generate low friction forces. There was a statistically significant order (0.016"×0.022"<0.018"×0.025"<0.019"×0.025") for stainless steel wire material. Finite element modeling simulation showed the increasing effect of active clip force on friction especially for 0.025" wire profiles. If compared to NiTi wires, stainless steel archwires delivered higher friction. Combinations between wire-type and ligation should be chosen carefully for the intended treatment step.
Objective
Tooth movement with elastic chains requires defined force magnitudes. This study assessed the force behaviour of different elastic chains at different configurations of gap width.
Methods
Self‐ligating brackets of teeth 5 & 6 and 2 & 3 were bonded to two movable aluminium plates. The plates were positioned on a joint basis with varying distances of 0.5, 2.0, 4.0, 6.0, and 8.0 mm. Reset forces of open and closed chains from four different manufacturers were investigated in four different configurations. Configurations differed in either having an additional intermediate ring within the gap (#1, #3) and/or having intermediate rings between teeth adjacent to the gap (#1, #2), or by no intermediate rings (#4). Forces were measured with a universal testing machine. The results were statistically analysed using U‐test, H‐test and (if applicable) post‐hoc tests with a significance level of .05.
Results
Configurations #1 and #3, and #2 and #4 formed homogenous subgroups (P < .001). Initial forces in configuration #4 were significantly higher than in configuration #3 (P = .029). Initial forces in closed chains were significantly higher than for open chains (P = .029).
Conclusions
Intermediate chain rings adjacent to the gap are not required to modulate the force. In contrast, leaving a ring unapplied in the tooth gap can help modulate the force. Open thermoset chains with an additional ring within the gap (#3) seem to produce suitable initial forces for a gap closure of 4 mm. With a residual gap width of <2 mm, open thermoset chains and closed thermoset chains (#4) seem suitable.
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