Browsing by Subject "Tooth Movement Techniques -- Methods"

Now showing 1 - 6 of 6
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    Determination of the 3D Load System for Space Closure Using Keyhole and Teardrop Closing Loops in a Full Arch
    (2008) Gajda, Steven W.; Roberts, W. Eugene; Hohlt, William H.; Baldwin, James J.; Shanks, James C.; Katona, Thomas R.; Chen, Jie
    The current movement in dentistry is to provide treatment that is evidence-based rather than opinion-based. Unfortunately, there is a lack of evidence for most orthodontic appliances. Much work has been done to find the appropriate load system to move teeth, but research has only been done with laboratory techniques that may not be applied clinically. Ideally, appliances should be tested in all three dimensions with techniques (e.g. type of ligation) that replicate clinical procedures. This can be accomplished with a new patented technology, the orthodontic force tester (OFT). The OFT allows an entire arch with brackets and a full arch wire to be set up while measurements are made on target teeth. With the OFT, appliances can be tested to ascertain if they provide the prescribed load system, and if not, then modify them or develop new ones. In this experiment two different commercially available prefabricated closing loop arch wires (keyhole and teardrop) were tested with variations in gable bends, interbracket loop position, and activation. The application being tested is closing space between a lateral incisor and canine in a first premolar extraction case after the canine has been retracted. While the trend shows that the keyhole loop produces higher overall force the two loops are not significantly different in the forces or moments that they generate. The one exception is that the keyhole loop produces higher lingual forces at the canine when the loop is in the mesial position. Also, few wire configuration were able to produce M/F sufficient to translate teeth. The wire configurations that can provide the proper load system to translate teeth in the lingual direction at the incisor were in the mesial position and had second order gable bends at the alpha position. The loop design had little effect on the M/F ratios.
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    The Effects of Interbracket Position and Distance on the Orthodontic Triangular Loop
    (2003) Bulucea, Irina; Chen, Jie; Katona, Thomas R.; Baldwin, James J.; Roberts, W. Eugene; Shanks, James C.
    Orthodontic closing loops offer an efficient way to control the moment to force ratios (M/F) delivered during space closure. The triangular loop is often used in the Graduate Orthodontic Clinic at the Indiana University School of Dentistry. Previous studies on the triangular loop were concerned with various loop geometries. The present project was designed to study the triangular loop in a clinically realistic experimental set up. Compared to the previous studies, three major changes were implemented: instead of two coplanar brackets, the current study employed a bracketed typodont arch (1) the effects of loop locations (2) and different interbracket distances were considered (3). The measured moment and forces reflect considerable differences in the systems due to the new experimental set up. As in previous studies, the triangular loops were fabricated from 0.016 X 0.022- inch stainless steel wire. The loops were equilateral triangles with 8 mm sides, ligated to the arch wire by elastomeric rings. There were 4 loop locations: location 1 was at 1.2 mm away from the mesial bracket; location 2 was at 3 .2 mm away from the distal bracket; location 3 was centered in the middle of the original interbracket distance; location 4 was located 2.6 mm away from the mesial bracket. There were three interbracket distances (IB). The original IB (IBl) of 12.6 mm was decreased by 3 mm (IB 2) and by 6 mm (IB 3). The loops were activated by 1.6 mm and 3.3 mm. Force and moment components were measured along three mutual perpendicular axes (x, y, and z) corresponding to the buccolingual, mesiodistal, occlusogingival axes respectively. Comparisons of Mx/Fy and Mz/Fy at the mesial and distal, by three activation levels, three interbracket distances, and four locations, and all interaction effects, were performed using a mixed design repeated measures ANOV A procedure. The General Linear Model (GLM) procedure for unbalanced designs was used because not all interbracket distances could be accommodated with all loop locations. Activation distance was the within specimen repeated factor. Loop location and interbracket distance were the between specimen factor. It was theorized that the location of the triangular loop, as well as the interbracket distance, have a considerable effect on the generated M/F. The Null Hypothesis was that there are no significant differences (p > 0.05) in the M/F ratios generated by the triangular loop as the loop position changes relative to the brackets, and there are no significant differences (p>0.05) in the M/F ratios generated by the triangular loop as the interbracket distance becomes shorter with space closure. Statistical significant interactions were found for Mx/Fy and Mz/Fy at location 2, for all activations, at both the mesial and distal measures. Therefore we rejected the first part of the Null Hypothesis (no differences as the loop location changes), and accept the second part (no differences as the interbracket distance shortens). We were able to see clear trends at all loop locations, as well as interbracket distances, and draw useful clinical implications. We found that the mesial closing forces are quite small when compared to those at the distal. We attributed this discrepancy to the U shape geometry of the continuous arch wire technique. We observed that if closing loops are delivered with no activation, then counterproductive M/F ratios are produced. Our data also indicated that anchorage becomes more critical as the interbracket distance shortens. Finally, we determined that wire tie ligation for prevention of rotation along the long axis of the tooth is especially important for the lateral incisor.
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    Effects of Positions and Magnitudes of Preactivation Bends on the Force Systems Generated by Orthodontic Stainless Steel T-Loop Springs
    (2000) Park, Bo Young; Chen, Jie; Baldwin, James J.; Hohlt, William F.; Katona, Thomas R.; Shanks, James C.
    Space closure of any kind in orthodontic treatment first needs a determination of the anchorage requirement. The clinician should control the force system accurately to achieve the differential space closure depending upon the diagnosis and treatment goals. Orthodontic T-loops have been used widely to close spaces. Several modifications have been made to achieve differential space closure. However, each modification has some clinical limitation and disadvantage. The purpose of this study is to look at the effects of preactivation bend position and magnitude on the force system and the possible implications in differential space closure. Five groups of orthodontic T-loops were studied. Each experimental group consisted of 20 T-loops and the positions or magnitudes of the preactivation bends were changed in each group. The forces and moments were measured, and the M/F ratios were computed. This study showed that the magnitude of the moment increased if (a) the preactivation position move closer to the bracket, or (b) the magnitude of preactivation is increased. There were extrusive forces acting on the side where the preactivation bends were closer to the bracket, or where the greater magnitude of preactivation existed.
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    Miniature Implants for Orthodontic Anchorage
    (2001) Deguchi, Toru; Garetto, Lawrence P.; Katona, Thomas R.; Hohlt, Thomas R.; Roberts, W. Eugene; Shanks, James C.
    Anchorage control is fundamental to successful orthodontic treatment. Dental implants can serve as ideal anchorage units because of their stability in bone. Previous studies limit the use of existing implants for anchorage because of their large size. Minimizing the size of the implant would reduce the extent of the surgery and may result in a decreased and less traumatic healing period. The objective of this study was to histomorphometrically analyze the use of miniature implants. A total of 96 miniature implants (1.0 x 5.0 mm; 48 loaded and 48 healing control) were placed in the mandible and maxilla of 8 male dogs. The implants were allowed to heal for three different periods (3, 6, and 12 weeks) followed by 12 weeks of 200 to 300 g of orthodontic force application. Bone specimens containing implants were collected for histomorphometric analysis. The results indicate that clinical rigidity (osseointegration) was achieved by 96.9 percent of the miniature implants. Histomorphometric analysis revealed that the amount of bone contact at the implant-bone interface ranged from 11.3 to 68 percent (mean ± SEM=34.4 ± 4.6 percent) in the healing control groups and from 18.8 to 63 percent (mean=43.l ± 4.0 percent) in the force applied groups in the maxilla. On the other hand, in the mandible, bone-implant contact ranged from 7 to 82 percent (mean=44.1 ± 6.8 percent) in the healing control groups and from 12 to 72 percent (mean=50.7 ± 5.3 percent) in the force applied groups. Results from bone formation rate, mineralizing surface/bone surface and mineral appositional rate showed a significant difference in the 3-week healing control group compared to those in other groups. From these results, we concluded that miniature implants are able to function as rigid osseous anchorage for orthodontics with minimal (less than 3 weeks) healing period. This study was supported by Matsumoto Research fund.
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    The Effects of Altering Interbracket Position on Closing Loops of Similar Dimensions
    (2002) Wilson, Don; Katona, Thomas R.; Baldwin, James J.; Chen, Jie; Hohlt, William F.; Shanks, James
    Orthodontic closing loops offer an efficient approach to consolidate extraction spaces. They allow for efficient tooth movement by lowering the load deflection rate, increasing potential activation, and by forming posterior anchorage units that can effectively resist displacement. The closing loop under investigation is a cross-leg delta loop. No studies have been done on this unique spring and the force systems created by altering its interbracket position. It is simple to fabricate chairside and produces fairly predictable moment to force ratios (M:F). The legs are crossed so the spring is activated in the same direction as its original bends, thus giving a more uniform distribution of stress within the spring, potential permanent deformation of the spring is decreased, reduced load deflection, and a greater overall range of activation. The cross-leg delta is simpler to fabricate than the more common T-loop since it needs two fewer bends. The material chosen for loop fabrication was 0.016 x 0.022 inch stainless steel wire due to its common use in clinic and research. Allowing for patient comfort and the fact that taller loops produce greater moment to force ratios, 7mm was chosen as the height of the cross-leg delta loop. The purpose of this study was to measure the spring generated forces and moments when altering the interbracket position of the closing loop. The null hypotheses are that there will not be any differences in the forces generated in the x (Fx) and y (Fy) directions, moments about the bucco-lingual axis (Mz), and M:F ratios in the sagittal plane (Mz:Fx) will not be altered by changing the interbracket position of cross-leg delta loops of same dimensions. A total of 120 loops, grouped as four sets of loops with 30 loops in each set: L1010, Ll 109, L1208, Ll307, were fabricated. The first two digits represent the length of the mesial leg and the last two digits represent the length of the distal leg for a total of 20mm in overall length. Each sequential set had the mesial leg increased by 1mm and the distal leg decreased by 1mm such that the most asymmetric set (L1307) had a 13mm mesial and a 7mm distal leg. The testing apparatus measured forces and moments along 3 mutually perpendicular axes (x, y, and z). Horizontal activation of the loop was performed by placing measured 1mm and 2mm stops over the wire. Data were collected from each set of loops. The cross-leg delta loops with symmetric 15° gable bends were compared for differences in moments and forces using repeated measures analysis of variance (ANOVA) models. Separate analyses were performed for Fx, Fy, Mz and Mz:Fx. Since the data was not normally distributed, a rank transformation was used. Pairwise comparisons were made using the Sidak method to control the overall significance level at 5%. Altering the interbracket position of a cross-leg delta loop did not cause major changes on the anterior and posterior forces in the x direction. Statistically significant differences in vertical forces (Fy), were much more pronounced when loops were positioned asymmetrically. Posteriorly positioned loops caused a statistically significant intrusive force on the anterior and extrusive force on the posterior segment was observed. As the loop was positioned more posteriorly, moments (Mz) acting in a clockwise direction on the anterior bracket decreased. More posteriorly positioned loops caused increased moments (Mz) in a counter-clockwise direction on the posterior bracket. As the loop was positioned more posteriorly, the M:F ratios in the sagittal plane acting on the anterior bracket decreased (Mz:Fx). More posteriorly positioned loops generated increased M:F ratios on the posterior bracket in the sagittal plane (Mz:Fx). Ideally, a posteriorly positioned closing loop would be used in a deep bite case needing maximum posterior anchorage. The intrusive force and decreased M:F ratio (Mz:Fx) on the anterior segment would cause more tipping and intrusion as space closure was carried out. The posteriorly positioned loop would generate increased moments (Mz) on the posterior bracket leading to increased M:F ratios in the sagittal plane (Mz:Fx). The extusive forces on the posterior segment would open the bite while the increased M:F ratios (Mz:Fx) would cause less tipping and increased anchorage. The study showed that altering the interbracket position of a closing loop can significantly alter the M:F ratio as well as the vertical and horizontal forces on the anterior and posterior segments. These results are important because the clinician can incorporate asymmetrically positioned loops to facilitate more efficient anchorage preparation. A posteriorly positioned loop can also generate an intrusive force on the anterior segment to help control overbite while retracting individual teeth or a segment en mass.
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    Using an Orthodontic Force Tester to Simulate Clinical Environment for Space Closure and Measuring the Applied Three-Dimensional Load System
    (2007) Isikbay, Serkis C.; Chen, Jie; Katona, Thomas R.; Hohlt, William H.; Baldwin, James J.; Shanks, James C.
    Applied orthodontic load systems (forces and moments) cause teeth to move from their existing position in the dental arch. The types of tooth movement can be classified as tipping, rotation and translation in three-dimension. If the desired tooth movement is pure translation, a force should be applied directly at the center of resistance. Since the center of resistance of teeth cannot be identified or accessed easily and reliably, and orthodontic brackets are applied most practically on the buccal surfaces of the tooth crowns, applying a force at the center of resistance is not realistic. Therefore, the applied force should be accompanied by a moment to moderate tipping. The control of the movement relies on the ability to quantify and manipulate the orthodontic load system, specifically the moment-to-force ratio (M:F). The inability to control the orthodontic load system can result in undesirable tooth movement as well as a decrease in the efficiency of overall treatment. The importance of the three-dimensional (3-D) load system is well established although it has never been satisfactorily measured. The purpose of this study was to measure forces and moments generated by a commercially available T-loop closing loop archwire in three axes simultaneously at two different locations utilizing the orthodontic force tester (OFT) and a custom-made dentoform that simulates a typical space closure clinical case. The parameters in the design of a closing archwire that influence the 3-D orthodontic load system were tested to analyze the effects of these variations. The five parameters that were investigated include activation, loop location, gable direction, gable angle, and gable type. The overall null hypothesis was that the variations in the design of a closing archwire would not influence the 3-D orthodontic load system (p>0.05). A full factorial analysis of variance (ANOVA) model was used to model the absolute value of the forces (Fx, Fy, Fz ) and moments (Mx, My, Mz) in each plane separately. Additionally the ratios of the moment in the x-plane (Mx) to the force in the y-plane (Fy) and of the moment in the y-plane (My) to the force in the x-plane (Fx) were calculated for each experimental run. Separate ANOVA models were run for each sensor type (lateral incisor and canine). In lieu of multiple pair-wise comparisons, Tukey's minimum significant difference was estimated assuming a significance level of alpha = 0.05. Along with estimates of the means and standard deviations of the forces and moments, appropriate 95% confidence intervals were estimated for each mean. Statistical significant interactions were found for the variations that were tested, therefore the Null Hypothesis was rejected. The various directions of Fy and its overall low magnitude at the lateral incisor bracket challenged the accepted notion that the lateral incisor moved distally during space closure. A resultant force may indeed be in the direction toward the center of the arch rather than the center of the space. It was noted that the intrusive/extrusive, the buccal/lingual root moments forces and the mesial/distal root moments were influenced more by the Second Order Gable Bends than the First Order Gable Bends. It could be concluded that 10,10 First Order Gable Bends and 10,10 or 20,0 Second Order Gable Bends should be used for most clinical space closure needs at anterior or middle T-loop spring positions with 1 mm or 2 mm activations. Future studies investigating self-ligating brackets, different closing loop designs, modifications, and materials are necessary to understand the 3D orthodontic force system further and design the ideal system that would allow clinical space closure as desired.