ABSTRACT
T-loop is one of the most popular closing loops in orthodontic profession. However its activation is in the contrary to Bouschinger effect theory, since the formed bends would be opened during activation. The purpose of this study was to add a helix in a way to be more respondent to the Bouschinger effect theory.To compare the load deflection, maximal elastic load and range between three different types of T-loop.5 sample of each 3 different designs of T-loop [group 1: original T-loop, group 2: T-loop with the two inner helices, group 3: T-loop with the two helices constructed outside the horizontal part] had been tested with universal testing machine [Instron]. The load -deflection curves was plotted and the mechanical properties [load deflection, maximal elastic load and range] were measured. One way ANOVA was used to identify statistical differences between designs.The mean value of maximal elastic load in group 1 [6.02 +/- 0.27] was significantly higher than group 2 [5.16 +/- 0.46] and in group 2 were significantly higher than group3 [4.35 +/- 0.25] [p<0.001]. A significantly higher load deflection was reported in group 1 [0.73 +/- 0.36] in comparison to group2 [0.56 +/- 0.74] and group 3[0.56 +/- 0.69] [p=0.002], with no significant difference between two latest groups [p=0.999]. The mean range in group 3 [4.15 +/- 0.10] was significantly lower than group 1[5.43 +/- 0.13] and group 2 [5.59 +/- 0.15] [p=<0.001] with no significant difference between group 1 and 2 [p=0.149].The results revealed that increasing length of T-loop with helices will decrease Load deflection rate the place and design of helices might not be a crucial factor. The new design of T-loop with helices relevant to Bouschinger effect theory needs a further survey regarding their position
ABSTRACT
One of the most prevalent problems in individuals suffering from resonance disorder is nasal air escape. Super Nasal Oral Ratio System [SNORS] is such an instrument which determines ratio of air escape from nasal and oral cavities. A precise judgment may be implemented by comparing the measured ratio of these patients with those of normal persons. It was an analytical-descriptive study in which 30 words [validated by speech pathologists] were chosen. The cases including 22 female and 15 male were asked to read these terms 10 times and then nasal ratio for each term was measured by SNORS. The test was repeated two weeks later to assure reliability of the words. There was no significant difference in ratio of each term. However repetition of the test showed no significant difference between words for nasal ratio but for 8 words. In 22 selected words 10 words [5 words nasal consonant and 5 words without it] with lowest standard deviation were selected as final list. The final list of words may be used for assignment of nasal ratio in males and females by SNORS