Force system evaluation of symmetrical beta-titanium T-loop springs preactivated by curvature and concentrated bends
Sergei Godeiro Fernandes Rabelo Caldas, Renato Parsekian Martins, Marília Regalado Galvão, Camilla Ivini Viana Vieira, and Lídia Parsekian Martins. Am J Orthod Dentofacial Orthop 2011;140:e53-e58
I ntroduction: The objective of this research was to compare the effect of preactivation on the force system of beta-titanium T-loop springs (TLSs). Methods: Twenty TLSs with dimensions of 6 × 10 mm, of 0.017 × 0.025-in beta-titanium alloy, were randomly divided into 2 groups according to their preactivation. By using a moment transducer coupled to a digital extensometer indicator adapted to a testing machine, the amounts of horizontal force and moment produced were recorded at every 0.5 mm of deactivation from 5 mm of the initial activation in an interbracket distance of 23 mm. The moment-to-force ratio, the “neutral position” and the load-deflection ratio were also calculated. Results: TLSs preactivated by curvature delivered horizontal forces significantly lower than those preactivated by concentrated bends. No differences were found in relation to the moments produced throughout the deactivation of both groups. The moment-to-force ratios were systematically higher on the TLSs preactivated by curvature than those preactivated by concentrated bends, except on 5 mm of activation. Significant differences were found in the load-deflection rates and “neutral position.” Conclusions: The TLSs preactivated by curvature delivered lower horizontal forces and higher moment-to-force and load-deflection ratios than did those preactivated by concentrated bends.
Accuracy of cone-beam computed tomography in predicting the diameter of unerupted teeth
Emerald Nguyen, Darrell Boychuk, and Maria Orellana. Am J Orthod Dentofacial Orthop 2011;140:e59-e66
I ntroduction: An accurate prediction of the mesiodistal diameter (MDD) of the erupting permanent teeth is essential in orthodontic diagnosis and treatment planning during the mixed dentition period. Our objective was to test the accuracy and reproducibility of cone-beam computed tomography (CBCT) in predicting the MDD of unerupted teeth. Our secondary objective was to determine the accuracy and reproducibility of 3 viewing methods by using 2 CBCT software programs, InVivoDental (version 4.0, Anatomage, San Jose, Calif) and CBWorks (version 3.0, CyberMed, Seoul, Korea) in measuring the MDD of teeth in models simulating unerupted teeth. Methods: CBCT data were collected on the CB MercuRay (Hitachi Medical Corporation, Tokyo, Japan). Models of unerupted teeth (n = 25), created by embedding 25 tooth samples into a polydimethylsiloxane polymer with a similar density to tissues surrounding teeth, were scanned and measured by 2 investigators. Repeated MDD measurements of each sample were made by using 3 CBCT viewing methods: InVivo Section, InVivo Volume Render (both Anatomage), and CBWorks Volume Render (version 3.0, CyberMed). These measurements were then compared with the MDD physically measured by digital calipers before the teeth were embedded and scanned. Results: All 3 of the new methods had mean measurements that were statistically significantly less ( P <0.0001) than the physical method, adjusting for investigator and tooth effects. Specifically, InVivo Section measurements were 0.3 mm (95% CI, −0.4 to −0.2) less than the measurements with calipers, InVivo Volume Render measurements were 0.5 mm less (95% CI, −0.6 to −0.4) than those with calipers, and CBWorks Volume Render measurements were 0.4 mm less (95% CI, −0.4 to −0.3) than those with calipers. Conclusions: Overall, there were high correlation values among the 3 viewing methods, indicating that CBCT can be used to measure the MDD of unerupted teeth. The InVivo Section method had the greatest correlation with the calipers.
Accuracy of cone-beam computed tomography in predicting the diameter of unerupted teeth
Emerald Nguyen, Darrell Boychuk, and Maria Orellana. Am J Orthod Dentofacial Orthop 2011;140:e59-e66
I ntroduction: An accurate prediction of the mesiodistal diameter (MDD) of the erupting permanent teeth is essential in orthodontic diagnosis and treatment planning during the mixed dentition period. Our objective was to test the accuracy and reproducibility of cone-beam computed tomography (CBCT) in predicting the MDD of unerupted teeth. Our secondary objective was to determine the accuracy and reproducibility of 3 viewing methods by using 2 CBCT software programs, InVivoDental (version 4.0, Anatomage, San Jose, Calif) and CBWorks (version 3.0, CyberMed, Seoul, Korea) in measuring the MDD of teeth in models simulating unerupted teeth. Methods: CBCT data were collected on the CB MercuRay (Hitachi Medical Corporation, Tokyo, Japan). Models of unerupted teeth (n = 25), created by embedding 25 tooth samples into a polydimethylsiloxane polymer with a similar density to tissues surrounding teeth, were scanned and measured by 2 investigators. Repeated MDD measurements of each sample were made by using 3 CBCT viewing methods: InVivo Section, InVivo Volume Render (both Anatomage), and CBWorks Volume Render (version 3.0, CyberMed). These measurements were then compared with the MDD physically measured by digital calipers before the teeth were embedded and scanned. Results: All 3 of the new methods had mean measurements that were statistically significantly less ( P <0.0001) than the physical method, adjusting for investigator and tooth effects. Specifically, InVivo Section measurements were 0.3 mm (95% CI, −0.4 to −0.2) less than the measurements with calipers, InVivo Volume Render measurements were 0.5 mm less (95% CI, −0.6 to −0.4) than those with calipers, and CBWorks Volume Render measurements were 0.4 mm less (95% CI, −0.4 to −0.3) than those with calipers. Conclusions: Overall, there were high correlation values among the 3 viewing methods, indicating that CBCT can be used to measure the MDD of unerupted teeth. The InVivo Section method had the greatest correlation with the calipers.
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