The purpose of this study was to clarify the effect of the loop position, transpalatal arch, and number of posterior teeth in en-masse retraction of anterior teeth with T-loop springs made from a titanium molybdenum alloy. Long-term orthodontic movements were simulated with the finite element method. The position of the T-loop changed the movement pattern of the anterior and posterior teeth; that is, the mesial loop moved both the teeth bodily and the center loop tipped the posterior teeth. The transpalatal arch prevented rotation of the posterior teeth. The addition of the second molar to the posterior teeth decreased the movement ratio of the posterior to anterior teeth by about two-thirds.

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In this study, we experimentally produced some types of temporary carboxylate cement containing a combination of HY-agents: zinc fluoride, fluorinated strontium, and tannic acid. Cement samples were then tested for antibacterial activity against Streptococcus mutans and Actinomyces naeslundii. The results showed that temporary cements of all types exhibited antibacterial activity. A comparison of cases with and without temporary carboxylate cement revealed a higher level of antibacterial activity with temporary carboxylate cement. Because the cement with zinc fluoride exihibited the highest level of antibacterial activity against S. mutans, the results suggest that zinc fluoride can enhance the antibacterial activity of commercial temporary carboxylate cement containing a combination of HY-agents. A combination of zinc fluoride, fluorinated strontium, and tannic acid showed the same level of antibacterial activity against A. naeslundii. The results reveal that the enhanced anti-bacterial activity of commercial temporary carboxylate cement with HY-agents can be attributed to their synergistic effect.

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