Browsing by Subject "Tooth Movement, Minor"

Now showing 1 - 3 of 3
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    A Study of the Physical Properties of Latex as Related to Orthodontic Tooth Movement
    (1971) Vornholt, John William
    Latex elastics have long been used in orthodontics, and force decay has always been a disadvantage. Reports differ on the load-deflection properties of rubber. Decay in elastic bands has ranged from 8% to 74.9%, depending on test conditions. A study was designed to ascertain (1) whether better quality controls would minimize decay and give better reproducibility in force from one elastic band to the next; and (2) whether the amount of stretch to which the elastic body is subjected affects the rate of decay. The quality control testing consisted of selecting elastic bands of identical size, shape, and color. This was followed by testing each one with a 100 gram weight and separating out all elastics which tested out to a given length. This test-controlled sample was then used to study the physical properties of latex. A load-deflection study was performed from this test-controlled sample, and revealed a curvilinear relationship. From the load-deflection curve, four force values were chosen which would represent 1) minimal stretching in the elastic deformation range, 2) maximal stretching in the elastic deformation range, 3) minimal stretching in the permanent deformation range, and 4) maximal stretching in the permanent deformation range. In the decay phase of the study, four more groups of elastics from the test-controlled sample were loaded with the four force values previously mentioned. The force was then measured after one and 12 hours and after one, seven, 14 and 21 days. Thus the decay of force could be calculated for each group over a three-week period. The results showed that more rigid quality control does produce a more predictable decay rate and force. The load-deflection properties of latex elastic were shown to be curvilinear, and the decay rate was affected by the amount of stretch to which the elastic body was subjected. However, if the elastic was stretched within the elastic deformation range, the decay rate remained the same regardless of the length of stretch. Therefore, it is recommended that the clinician use latex elastic in the elastic deformation range and thereby reduce the decay rate.
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    Displacement of Anchorage in Controlled Root Movement at Various Force Values
    (1970) Winkler, Robert A.; Cunningham, Donald; Garner, LaForrest; Mitchel, David; Norman, Richard; Shanks, Jim
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    Testing of Orthodontic Springs Using Geometric Variables
    (1995) Markham, David; Chen, Jie; Katona, Thomas R.; Arbuckle, Gordon R.; Baldwin, James J.; Shanks, James C.
    A common method of space closure utilizes loops formed in orthodontic arch wires. The loops must provide adequate force characteristics to maintain controlled tooth movement. Generally, a moment-to-force (M/F) ratio of 10 mm is considered effective. The 1/2 Baldwin Spring is an effective loop, but it is difficult to fabricate and potentially irritating in the oral cavity. T- and L-loops are commonly used in orthodontics. They are conceivably less effective for controlled tooth movements but are simple to fabricate and relatively more comfortable in the oral cavity. This study demonstrates how altering the vertical and horizontal dimensions of the T- and L-loops affects their force characteristics. The vertical dimensions were 6 mm and 7 mm for the T- and L-loop. The horizontal dimensions were 6 mm, 7 mm, and 8 mm for the T-loop and 4 mm, 5 mm, and 6 mm for the L-loop. The experimental groups were named according to loop shape, vertical dimension, and horizontal dimension: T66, T67, T68, T76, T77, T78; L64, L65, L66, L74, L75, L76. Specimens were fabricated from 0.016 in x 0.022 in stainless steel and tested at 1 mm, 2 mm, and 3 mm horizontal activation distances (dx). Then they were preactivated by 30° gable bends, heat-treated (30°-htx), and tested again. Experimental data collection included the moment about the z axis (Mr) and the force along the x axis (Fx). TheMr/ Fx ratio was calculated. The T-loop with 30°-htx provided the highest M/F ratios at 1 mm dx and ranged from 5.15 mm (T68) to 6.67 mm (T67) (p<0.05). The T77 with 30°-htx exhibited the most consistent M/F ratios at 1 mm, 2 mm, and 3 mm dx: 6.09 mm, 6.01 mm, 6.04 mm consecutively (p~.6309). The L-loop provided scattered data ranging from -0.50 mm (L65) to 4.15 mm (L75). In general, 30°-htx increased the M/F ratio in all groups. T6* loops provided higher M/F ratios than TT* loops at small dx. T*8 loops provided consistently low M/F ratios ranging from 4.92 mm (T68) to 5.18 mm (T78). Altering the vertical and horizontal dimensions of the Tand L-loop significantly affects their force characteristics (p<0.05). None of the geometrically altered T- and L-loop designs provided ideal M/F ratios. These data suggest that the best T-loop designs for space closure are T66,T67, and T77.