“EFFICIENCY OF NEWER GENERATION PREADJUSTED EDGEWISE APPLIANCES” – A RANDOMIZED CONTROLLED TRAIL
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• Andrews increased anterior tip due to “Wagon wheel effect” where tip was lost as torque was added(4:1). • He added additional tip of 100 in the upper anterior segment and 120 in the lower anterior segment. • Due to extra tip built into the anterior brackets there was the tendency for anterior teeth to incline forward during the initial phase of leveling and aligning.
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• Attempts were made to eliminate or minimize this effect by connecting anterior segments to posterior segments, usually with elastic forces. But this created a greater demand for anchorage control during this initial stage of treatment. • Increased elastic force resulted in “roller coaster effect”. www.indiandentalacademy.com
• The anterior tip specifications for the original SWA and Roth were all greater than the research findings. Additional tip had been built in, over and above the scientific means, for e.g., the important upper canine carried 110 in the first generation (SWA) and then 130 in the second generation (Roth) system, compared with the research finding of 80. www.indiandentalacademy.com
Additional anterior tip was a disadvantage for three reasons: • It created a significant drain on Antero-posterior (A/P) anchorage. • It increased the tendency to bite deepening during the alignment stage. • It brought the upper canine root apex too close to the first premolar root in some cases www.indiandentalacademy.com
Tip values Reduced Upper and Lower Anterior Tip Upper Anterior Tip Centrals
Laterals Canine
Lower Anterior Tip Centrals
Laterals
Canines
Andrew’s norms
3.59
8.04
8.4
0.53
0.38
2.5
Original SWA
5
9
11
2
2
5
Roth SWA
5
9
13
2
2
7
MBT Versatile
4
8
8
0
0
3
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• Mclaughlin, Bennett and Trevisi redesigned the entire bracket system to complement their proven treatment philosophy and to overcome the perceived inadequacies of the original SWA and Roth Prescription appliances.
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• By using additional tip in the anterior brackets, anywhere from 2 to 3 mm of molar anchorage can be lost in bringing the roots of the anterior teeth to this over angulated position.
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• Because tip appears to be the strength of the pre adjusted appliance and because with light forces there is no need for second order compensation or “anti-tipâ€?, when designing the MBT bracket system, it was decided to base the anterior tip on the original research values. www.indiandentalacademy.com
• The present double blind, randomized controlled trial is being undertaken to study the efficiency of a newer generation preadjusted edgewise appliances (MBT) compared to an earlier generation preadjusted edgewise appliances (Roth) in terms of anchorage control and efficient alignment during the initial stage of treatment. www.indiandentalacademy.com
METHODOLOGY • Study group comprised of 20 patients who need first premolar extraction as a part of orthodontic treatment. • The Head of Department who is not involved in the study coded two bracket system (MBT and Roth), each containing 10 sets to Group A and Group B. • The principal investigators did not know which group belongs to which bracket system until the results were analyzed. www.indiandentalacademy.com
• After the results were obtained and analyzed then groups were recorded accordingly. • Group A was found to be MBT bracket system and Group B was Roth bracket system. •
20 patients were randomly taken from the Department OPD. They were randomized by asking the patient to chose the token (Red for Group A and Blue color for Group B). www.indiandentalacademy.com
Treatment Protocol : • The cases under study were strapped up with 0.022 MBT or 0.022 Roth full banded prescriptions. • Bracket positioning was done using individualized bracket-positioning charts. • Lace backs are used for antero-posterior canine control • Bend backs for antero-posterior incisor control. www.indiandentalacademy.com
• All 2nd molars are banded and transpalatal arch placed. • As leveling and alignment progressed round 0.016 HANT were replaced by 0.019” x 0.025” HANT which was later replaced by 0.019” x 0.025”SS wire.
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Incisor Torque (Lateral Cephalogram) • Maxillary Incisors: Angle formed between long axis of maxillary incisor to the S-N plane was measured before treatment and after alignment. • Mandibular Incisors : Angle formed between long axis of mandibular incisor to the mandibular plane was measured before treatment and after alignment.
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Measurement of tip
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Reference lines used to measure tip
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Reference line for uppers
Tip Value (OPG)
Reference line for lowers www.indiandentalacademy.com
MBT
ROTH
Upper right canine
0.8 ± 1.5
2.2 ± 1.2
Upper left canine
0.7 ± 1.4
2.6 ± 1.6
Upper right canine
0.4 ± 1.2
1.8 ± 2.0
Upper left canine
0.3 ± 2.7
1.0 ± 1.2
Not significant www.indiandentalacademy.com
Significant
Anchorage consideration (Lateral Cephalogram) X-axis 70 to SN Y-axis 900 to X-axis
Horizontal measurements
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GRAPH - II : Y AXIS TO UPPER INCISOR INCISAL TIP
76.1
76.5 76 75.5
75.5 75.2
75 74.4 74.5 74 73.5 Pre
Post
Group A Group B www.indiandentalacademy.com
GRAPH - III : Y AXIS TO UPPER MOLAR MESIO-BUCCAL CUSP
45.8 46
45.6
45.5 45 44.5
43.9
44 43.5 43 42.5 Pre
Post
Group A
Group B
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45.6
HORIZONTAL MEASUREMENT CHANGES IN MBT PRESCIPTION . PATIENT
Anchorage loss of molars (0.2 ± 0.9)
Slight proclination of anteriors(.03 ± 0.05 )
Lingual tipping of lower incisors1.5 ± 0.2 www.indiandentalacademy.com
HORIZONTAL MEASUREMENT CHANGES IN ROTH PRESCIPTION .
PATIENT
Anchorage loss of molars (1.7 ± 0.5 )
Proclination of anteriors(1.7 ± 0.9)
MORE ANCHORAGE LOSS AND ANTERIOR FLARING IN MAXILLARY ARCH www.indiandentalacademy.com
• In the present study we had coordinated the arch forms in both the groups so there was no significant variation between both the groups • In the present study the selected cases were bearing bimaxillary protrusion with no functional interference so the result indicated none of them to have functional occlusal changes. www.indiandentalacademy.com
• The flaring of maxillary anteriors in group B (Roth prescription) was due to extra- tip added to the anterior brackets. This extra tip resulted in increase in the arch length leading to the flaring of anteriors. Lace backs and bend backs which were given to control this anterior flaring resulted in increased mesial force on molars ensuing anchorage loss in group B patients.
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TORQUE
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• When the edgewise appliances is used, the application of resilient wires in the leveling phase leads to undetectable force systems and torques, possibly resulting in unintended individual tooth movements with undesirable side effects. During retraction or protraction, a resilient wire may cause jiggling movements; the elastic deformation of the wires may trigger intrusive and extrusive side effects that may induce undesirable histologic responses. These problems must be taken into account when comparing type of tooth movement and histologic findings.
•Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1995 Apr (360 - 371): Histologic tissue response after tooth movement Wehrbein, Fuhrmann,and Diedrich www.indiandentalacademy.com
• Usually upper molar torque need not be changed. • When resilient wire placed posterior teeth first move buccally and then palatally producing dehiscence, fenestrations , severe root resorption and sinus perforation. This is due torque change from anteriors to posteriors
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Thurow pointed out that unless all teeth in an arch need torquing in the same direction and degree there should be some play between the arch wire and brackets. If there is not, as the wire is activated in engaging a bracket on a tooth requiring torque, adjacent teeth are torqued in the opposite direction first and then complete unnecessary “round trip� as the wire returns to its passive state. Any activation for torque should be less than the degree of play in the opposite direction at adjacent teeth.
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• Torque values Maxillary Tooth ROTH
II molar -9
I Molar -9
II PM -7
MBT
-14
-14
-7
I PM Canine Latera Central l -7 -7 8 12 -7
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0
10
17
• With an .017” x .025” wire in .018” slot slop is 4.50 • With an .019” x .025” wire in .022” slot slop is 10.50 DR. THOMAS D. CREEKMORE (1979)
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ROTH Maxillary II I Tooth molar Mola r ROTH -9 -9
II PM
I PM Canine Latera Centra l l
-7
Difference in torque = 150
-7
-7
8
150
12
40
Slop= 4.50 11.50 of unnecessary back and forth torque action. When 17x25 placed in 18 slot brackets slop between wire and slot is just 4.50. The torque difference between lateral incisors and posteriors is 150 so there is unnecessary back and forth torque action. www.indiandentalacademy.com
• Because of reduce play between wire and slot in Roth prescription appliance more force is exerted by rectangular niti. This lowers the pain threshold for the patient resulting in increased hyalinization. The treatment time during leveling and aligning stage is increased due to “jiggling” and round tripping of teeth. www.indiandentalacademy.com
MBT Maxillary II I Tooth molar Molar MBT
-14
-14
II PM -7
I PM Canine Latera Centra l l -7
70
0
70
Difference in torque =Maximum 100 Slop= 10.5
0
No unnecessary back and forth torque action. www.indiandentalacademy.com
10
100
17
70
• Increased pain threshold due to reduced force •Reduced treatment time
Materials and method
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• FE analysis solves a complex problem by redefining it as the summation of the solutions of a series of inter related simpler problems.
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• CT scan images of Maxilla were taken in the axial direction, parallel to the occlusal plane. Sequential CT images were taken at 3-mm intervals to reproduce finer and detailed aspects of the geometry.
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CT SCAN (AXIAL VIEW PARALLEL TO OCCLUSAL PLANE) www.indiandentalacademy.com
TRACINGS OF CT SCAN www.indiandentalacademy.com
AUTOCAD TRACING OF EACH LAYER
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SUPER IMPOSITION OF ALL LAYERS
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• Along the centerline of bone, of each CT image, geometric points were defined and assigned X, Y, and Z coordinates, which were fed into the preprocessor of the software for grid generation. The FE program used in this study was NISA-II Display-III and was run on a Pentium-III computer www.indiandentalacademy.com
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• The grids created were then joined to form lines. The geometric lines passing through these points described the measured bone geometry as close as possible.
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• The next step was to generate geometric surfaces by joining lines together. Each layer created was stacked one above the other in the axial direction and joined by straight lines. Lines were joined to create patches. Only 7 layers of the maxilla with respect to the dentition was modeled and analyzed.
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• The next step was to convert the geometric model into a FEM. The geometric entities created in the previous step were replaced with finite elements and nodes at this stage. • The complete geometry is now defined as an assemblage of discrete pieces called elements and are connected together at a finite number of points called nodes. • In this study a linear four nodal quadrilateral and triangular shell elements were used, which were able to take membranes into account, ie, in-plane deformation as well as bending deformations. www.indiandentalacademy.com
• The shell elements have six degrees of freedom (DOF) at each of their unstrained nodes: three translations (X, Y, and Z) and three rotations (around the X, Y, and Z axes). • In the present study the model consisted of 44142 DOF, which gives a more consistent result as compared with previously published studies. The total number of elements and nodes created was 9218 and 8980, respectively www.indiandentalacademy.com
Centrals
laterals
st Canine 1st Premolar 2nd Premolar 1 molar
CAD MODEL www.indiandentalacademy.com
www.indiandentalacademy.com 3D-FE CAD MESH SHOWING MAXILLARY TEETH WITH PERIODONTAL SUPPORT
TOOTH
PDL
BONE
3D-CAD MODEL OF MAXILLARY DENTITION AND PERIODONTAL SUPPORT www.indiandentalacademy.com
3D-FEM analysis done on 0.017 x0.025 niti in 0.018 slot and 0.019 x0.025 niti in 0.022 slot to find torquing force applied by the wire www.indiandentalacademy.com
• Force levels Maxillary Tooth ROTH
I Molar -.193
II PM -.302
I PM
Canine
-.516N
-1.547N
.6N
1.57N
MBT
-.09N
-.16N
-.2N
-.52N
.2N
.52N
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Lateral Central
STRESS DISTRIBUTION IN ROTH (0.017” x 0.025” in 0.018 slot)
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STRESS DISTRIBUTION IN MBT (0.019” x 0.025” in 0.022 slot)
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DISPLACEMENT IN ROTH (0.017” x 0.025” in 0.018 slot)
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DISPLACEMENT IN MBT (0.019” x 0.025” in 0.022 slot)
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ROTH
MBT
INCISOR DISPLACEMENT
28.49 X 10-4 Mpa
10.25 x 10-4Mpa
MAX STRESS
.9253Mpa
.3770 Mpa
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PARAMETER
TIME TAKEN LEVELING AND ALIGNING
GROUP
TREATMENT TIME
FOR GROUP A 3.5MON ±0.5
GROUP B 4.1MON ±1.1
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