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BIO-MECHANICS OFBIO-MECHANICS OF
TORQUETORQUE
A Finite Element InvestigationA Finite Element Investigation
Dr. Vijay P. ...
2
Salutations to Dr. AngleSalutations to Dr. Angle
3
 Angle’s achieved a quantum leap in orthodonticAngle’s achieved a quantum leap in orthodontic
mechanics by introducingm...
4
TorqueTorque
 Torque control isTorque control is essentialessential forfor
1. Esthetic, functional and health outcome o...
5
What prompted the presentWhat prompted the present
studystudy
Writings ofWritings of
 IsaacsonIsaacson et al, -et al, -...
6
Reciprocal reactionsReciprocal reactions on adjacenton adjacent
teethteeth during torque application withduring torque a...
7
Theory V/s Practice of TorqueTheory V/s Practice of Torque
Isaacson et al (1993)Isaacson et al (1993)
““The equal and op...
8
What happens with incrementalWhat happens with incremental
torque?torque?
1,2,3 progressively
torqued more and
more?
Som...
9
Isaacson’s hypothesisIsaacson’s hypothesis
10
Relevant Clinical situationRelevant Clinical situation
 IncrementalIncremental
twisting bendstwisting bends
between 13...
11
Ineffectiveness of ProgressiveIneffectiveness of Progressive
Torque inTorque in Clinical PracticeClinical Practice??
 ...
12
PossiblePossible explanationexplanation
 What Isaacson mentioned are theWhat Isaacson mentioned are the initial effect...
13
PossiblePossible explanationexplanation
 Perhaps,Perhaps, as the end teeth start moving, theas the end teeth start mov...
14
Biologic implicationsBiologic implications
(DeAngelis and Davidovitch)(DeAngelis and Davidovitch)
 Root resorption pos...
15
Optimum Torquing momentsOptimum Torquing moments
10 to 20 N mm10 to 20 N mm for rectangular wire torquefor rectangular ...
16
Aims and objectivesAims and objectives
1. To verify the hypothesis of Isaacson1. To verify the hypothesis of Isaacson
r...
17
Aims and objectivesAims and objectives
3. To explore the effects of different amounts of3. To explore the effects of di...
18
MethodologyMethodology
 Finite Element Method (Finite Element Method (FEMFEM) – Excellent tool in) – Excellent tool in...
19
MethodologyMethodology
 The FEM software employed wasThe FEM software employed was Nastran-Nastran-
Patran.Patran.
 A...
20
21
MethodologyMethodology
 AppropriateAppropriate torquing momentstorquing moments were applied atwere applied at
thethe ...
22
23
Some AssumptionsSome Assumptions
 The software assumes that the archwireThe software assumes that the archwire
fits pr...
24
Some AssumptionsSome Assumptions
 Will this affect its reliability in application to theWill this affect its reliabili...
25
Validation of force valuesValidation of force values
 Any numerical study must be validated byAny numerical study must...
26
Validation of force valuesValidation of force values
Wire
Size
Range
of
play
Mean
play
Expt.
Range
Mean
value
FEM
18 x2...
27
I. Verification of Isaacson’s hypothesisI. Verification of Isaacson’s hypothesis
forfor Straight length of wire
Tooth 1...
28
ActivationActivation Torque on teeth (N mm)Torque on teeth (N mm)
LeftLeft
LateraLatera
ll
LeftLeft
CentralCentral
Righ...
29
Verification of Isaacson’sVerification of Isaacson’s
hypothesishypothesis
 Thus the clinical picture may be slightlyTh...
30
II. Stepwise resolution of anteriorII. Stepwise resolution of anterior
TorqueTorque
 IncrementalIncremental
twisting b...
31
Amount of
torque
(Degrees)
Torque on each tooth
(Nmm)
Central Lateral Canine
Central : 20
Lateral : 10
30.74 -6.53
-13....
32
Other situations studiedOther situations studied
 TorquingTorquing twotwo incisorsincisors
in the same directionin the...
33
Lingual Root Torque for Central Incisors
Amount of
torque
(Degrees)
Torque on each tooth
(Nmm)
Central Lateral Canine
1...
34
Lingual Root Torque on Four Incisors
Amount of
torque
(Degrees)
Torque on each tooth
(Nmm)
Central Lateral Canine
cent ...
35
Individual Root Torque – Right centralIndividual Root Torque – Right central
incisorincisor
WireWire
size/size/
alloyal...
36
III. The effect of built-in torque usingIII. The effect of built-in torque using
MBTMBT prescriptionprescription
 The ...
37
MBT Actual Clinical momentMBT Actual Clinical moment
valuesvalues
 The high FEM values do not apply (forThe high FEM v...
38
MBT Cuspid -7MBT Cuspid -7
Amount ofAmount of
torquetorque
(Degrees)(Degrees)
  Torque on each tooth (Nmm)Torque on eac...
39
MBT Cuspid 0 and +7MBT Cuspid 0 and +7
Amount ofAmount of
torquetorque
(Degrees)(Degrees)
  Torque on each tooth (Nmm)T...
40
MBT Inverted lateral bracketMBT Inverted lateral bracket
Amount ofAmount of
torquetorque
(Degrees)(Degrees)
  Torque on...
41
 IS IT A GOOD IDEA TO INVERT THEIS IT A GOOD IDEA TO INVERT THE
LATERAL BRACKETLATERAL BRACKET ( especially( especiall...
42
IV. Torquing Moments from variousIV. Torquing Moments from various
wireswires
 The torsional stiffness ratio of SS : T...
43
Clinical recommendationsClinical recommendations
 Twists in the rectangular archwireTwists in the rectangular archwire...
44
Clinical recommendationsClinical recommendations
ForFor active torquingactive torquing with twists in the rectangularwi...
45
Clinical recommendationsClinical recommendations
 TheThe moments generated by the NiTimoments generated by the NiTi
ar...
46
Clinical recommendationsClinical recommendations
Alternate methodsAlternate methods proposed by authors likeproposed by...
47
Alternate torquing methodsAlternate torquing methods
(Thurow)(Thurow)
48
Alternate torquing methodsAlternate torquing methods
(DeAngelis)(DeAngelis)
Warren Spring
49
Alternate torquing methodsAlternate torquing methods
(Burstone, Isaacson)(Burstone, Isaacson)
50
TwistTwist in the wirein the wire v/sv/s TorqueTorque of teethof teeth
 Angle’sAngle’s torque control concepttorque co...
51
THANKS TOTHANKS TO
Co-Authors:Co-Authors:
Prof. Satish Annigeri (B.V.B. EngineeringProf. Satish Annigeri (B.V.B. Engine...
52
THANK YOUTHANK YOU
53
54
55
56
Young’s modulus and Poisson’sYoung’s modulus and Poisson’s
ratioratio
Young’sYoung’s
ModulusModulus
Poisson’sPoisson’s
...
57
Moments generated by SSMoments generated by SS
WiresWires
Clinical SituationClinical Situation
Amount ofAmount of
torqu...
58
Individual Root Torque – Right centralIndividual Root Torque – Right central
incisorincisor
WireWire
size/size/
alloyal...
59
Ineffectiveness ofIneffectiveness of ProgressiveProgressive
IncrementalIncremental Torque (Isaacson)Torque (Isaacson)
60
Some AssumptionsSome Assumptions
 The differences in theThe differences in the sizes and shapes ofsizes and shapes of
...
61
Basic Premise of the EdgewiseBasic Premise of the Edgewise
ApplianceAppliance
An ideally shaped rectangular archwire,An...
62
P.A.E. AppliancesP.A.E. Appliances
 Same implicit understanding of P.A.E.Same implicit understanding of P.A.E.
applian...
63
Aims and objectivesAims and objectives
6. To study the possible actions and6. To study the possible actions and
reactio...
64
Some AssumptionsSome Assumptions
 All brackets perfectly leveled and aligned.All brackets perfectly leveled and aligne...
65
Isaacson - Kesling DebateIsaacson - Kesling Debate
66
Isaacson Kesling DebateIsaacson Kesling Debate
67
Isaacson - Kesling DebateIsaacson - Kesling Debate
68
 ““Orthodontic practice is nothing but push, pull andOrthodontic practice is nothing but push, pull and
twist”.twist”....
69
Isaacson’s hypothesisIsaacson’s hypothesis
1R
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Advantages of FEMAdvantages of FEM
When properly appliedWhen properly applied
 It couldIt could obviate the needobviat...
71
MethodologyMethodology
 Appropriate values for Young’s Modulus andAppropriate values for Young’s Modulus and
Poisson’s...
72
Optimum Torquing momentsOptimum Torquing moments
 A light torquing spring with 3 to 4 N mm momentA light torquing spri...
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Biomechanics of torque control

Biomechanics of torque control

Biomechanics of torque control

  1. 1. 1 BIO-MECHANICS OFBIO-MECHANICS OF TORQUETORQUE A Finite Element InvestigationA Finite Element Investigation Dr. Vijay P. JayadeDr. Vijay P. Jayade Prof. And Head,Prof. And Head, Department Of Orthodontics,Department Of Orthodontics, S.D.M. College of DentalS.D.M. College of Dental Sciences,Sciences, Dharwad.Dharwad.
  2. 2. 2 Salutations to Dr. AngleSalutations to Dr. Angle
  3. 3. 3  Angle’s achieved a quantum leap in orthodonticAngle’s achieved a quantum leap in orthodontic mechanics by introducingmechanics by introducing root controlroot control in hisin his appliances.appliances.  ( “All that one can do is to push, pull or twist”).( “All that one can do is to push, pull or twist”).  ThisThis “twist“twist in the tale” has dramatically changedin the tale” has dramatically changed the script of orthodontic mechanics.the script of orthodontic mechanics.
  4. 4. 4 TorqueTorque  Torque control isTorque control is essentialessential forfor 1. Esthetic, functional and health outcome of1. Esthetic, functional and health outcome of the treatment,the treatment, 2. Stability of the results.2. Stability of the results. It is commonly attained by manipulatingIt is commonly attained by manipulating thirdthird order relationship of a rectangular archwire -order relationship of a rectangular archwire - rectangular slotrectangular slot..
  5. 5. 5 What prompted the presentWhat prompted the present studystudy Writings ofWritings of  IsaacsonIsaacson et al, -et al, - mechanicsmechanics of torque usingof torque using rectangular wires, more specifically therectangular wires, more specifically the complex reactions on thecomplex reactions on the adjacentadjacent teeth,teeth,  DeAngelis and DavidovitchDeAngelis and Davidovitch -- biologicbiologic considerations of torque application.considerations of torque application.
  6. 6. 6 Reciprocal reactionsReciprocal reactions on adjacenton adjacent teethteeth during torque application withduring torque application with rectangular wiresrectangular wires  These were mentioned byThese were mentioned by Brodie (1931)Brodie (1931) and subsequently byand subsequently by othersothers like Strang,like Strang, Thurow and Andreasen.Thurow and Andreasen.  However, theirHowever, their complexitycomplexity was not givenwas not given due attention till recently.due attention till recently.
  7. 7. 7 Theory V/s Practice of TorqueTheory V/s Practice of Torque Isaacson et al (1993)Isaacson et al (1993) ““The equal and opposite reciprocal reactionsThe equal and opposite reciprocal reactions (which generally cause(which generally cause undesirable oppositeundesirable opposite movementsmovements of adjacent teeth) are commonlyof adjacent teeth) are commonly disregarded”.disregarded”. ““On the basis of theoretical mechanics, thisOn the basis of theoretical mechanics, this approach is conceptually flawed”.approach is conceptually flawed”.
  8. 8. 8 What happens with incrementalWhat happens with incremental torque?torque? 1,2,3 progressively torqued more and more? Some other response? All torqued equally?
  9. 9. 9 Isaacson’s hypothesisIsaacson’s hypothesis
  10. 10. 10 Relevant Clinical situationRelevant Clinical situation  IncrementalIncremental twisting bendstwisting bends between 13, 12,between 13, 12, 11 also 21, 22, 23.11 also 21, 22, 23. XX XX
  11. 11. 11 Ineffectiveness of ProgressiveIneffectiveness of Progressive Torque inTorque in Clinical PracticeClinical Practice??  This situation for torquing the incisors, isThis situation for torquing the incisors, is analogousanalogous to the one discussed by Isaacson.to the one discussed by Isaacson.  It does appear to work clinically.It does appear to work clinically.  HOW DOES IT HAPPEN?HOW DOES IT HAPPEN?
  12. 12. 12 PossiblePossible explanationexplanation  What Isaacson mentioned are theWhat Isaacson mentioned are the initial effectsinitial effects and not all the actions and reactions, whichand not all the actions and reactions, which keep on fluctuating till thekeep on fluctuating till the twist in the wiretwist in the wire expresses itself completely.expresses itself completely.
  13. 13. 13 PossiblePossible explanationexplanation  Perhaps,Perhaps, as the end teeth start moving, theas the end teeth start moving, the torquing moments on them gradually diminish,torquing moments on them gradually diminish, and so also the reactionary moments on theand so also the reactionary moments on the middle teeth. The twist in the wire would thenmiddle teeth. The twist in the wire would then start acting on the middle teeth.start acting on the middle teeth.  TheThe changing sequence of actions andchanging sequence of actions and reactionsreactions needs to be worked out.needs to be worked out.  IS THERE ANY ROUND TRIPPING?IS THERE ANY ROUND TRIPPING?
  14. 14. 14 Biologic implicationsBiologic implications (DeAngelis and Davidovitch)(DeAngelis and Davidovitch)  Root resorption possibility increases due to :Root resorption possibility increases due to : a)a) “round tripping”“round tripping” and “jiggling” of roots,and “jiggling” of roots, b)b) excessive torquing forces / moments.excessive torquing forces / moments.
  15. 15. 15 Optimum Torquing momentsOptimum Torquing moments 10 to 20 N mm10 to 20 N mm for rectangular wire torquefor rectangular wire torque (Burstone(Burstone,, Nikolai,Nikolai, andand Meiling and Odegaad)Meiling and Odegaad) forfor bodily translationbodily translation (M/F ratio 10:1)(M/F ratio 10:1) Are the moments, which are generated in clinicalAre the moments, which are generated in clinical practice, within this range?.practice, within this range?.
  16. 16. 16 Aims and objectivesAims and objectives 1. To verify the hypothesis of Isaacson1. To verify the hypothesis of Isaacson regarding theregarding the initial effectsinitial effects of progressiveof progressive root torque.root torque. 2. To work out how the effects of root2. To work out how the effects of root torque in various situations mighttorque in various situations might gradually be alteringgradually be altering over a period ofover a period of timetime..
  17. 17. 17 Aims and objectivesAims and objectives 3. To explore the effects of different amounts of3. To explore the effects of different amounts of built-in torquebuilt-in torque on adjacent teeth in the PAEon adjacent teeth in the PAE appliances.appliances. 4. To estimate the4. To estimate the quantum of momentsquantum of moments generated by different archwires.generated by different archwires.
  18. 18. 18 MethodologyMethodology  Finite Element Method (Finite Element Method (FEMFEM) – Excellent tool in) – Excellent tool in analyzing problems ofanalyzing problems of mechanicalmechanical nature (innature (in this instance,this instance, moments and displacementmoments and displacement behavior).behavior).
  19. 19. 19 MethodologyMethodology  The FEM software employed wasThe FEM software employed was Nastran-Nastran- Patran.Patran.  A rectangular wire in edgewise mode wasA rectangular wire in edgewise mode was modeled initially as straight length and later asmodeled initially as straight length and later as anterior part of an archwire onanterior part of an archwire on AutocadAutocad softwaresoftware  175175 nodesnodes in the anterior curvaturein the anterior curvature
  20. 20. 20
  21. 21. 21 MethodologyMethodology  AppropriateAppropriate torquing momentstorquing moments were applied atwere applied at thethe correct locations :correct locations :  a) from presumed twists in the archwire ORa) from presumed twists in the archwire OR  b) from in-built torque in the brackets.b) from in-built torque in the brackets.  ThenThen reciprocal reactions were derivedreciprocal reactions were derived fromfrom the software (boththe software (both initial, as also over timeinitial, as also over time fromfrom wire relaxation).wire relaxation).
  22. 22. 22
  23. 23. 23 Some AssumptionsSome Assumptions  The software assumes that the archwireThe software assumes that the archwire fits precisely in the bracket slotfits precisely in the bracket slot without anywithout any playplay (e.g., a slot height of 0.019” was(e.g., a slot height of 0.019” was assumed for the archwire having theassumed for the archwire having the dimension of 19x25).dimension of 19x25).
  24. 24. 24 Some AssumptionsSome Assumptions  Will this affect its reliability in application to theWill this affect its reliability in application to the clinical practice?clinical practice?  No, because what it depicts is theNo, because what it depicts is the clinicallyclinically effective torqueeffective torque that acts on the teeththat acts on the teeth after theafter the archwire-bracket play has been overcomearchwire-bracket play has been overcome..  The play isThe play is uniformuniform for all the brackets for anyfor all the brackets for any given archwire.given archwire.
  25. 25. 25 Validation of force valuesValidation of force values  Any numerical study must be validated byAny numerical study must be validated by comparing with a laboratory study.comparing with a laboratory study.  AA laboratory set uplaboratory set up, as used by Meling,, as used by Meling, Odegaard and Meling, was simulated on FEM,Odegaard and Meling, was simulated on FEM, and moments generated were compared.and moments generated were compared.
  26. 26. 26 Validation of force valuesValidation of force values Wire Size Range of play Mean play Expt. Range Mean value FEM 18 x25 mil 2.98o - 6.31o 4.6o 3.24- 4.79 Nmm 3.86 Nmm 3.39 Nmm Wire twisted by 1 degree -
  27. 27. 27 I. Verification of Isaacson’s hypothesisI. Verification of Isaacson’s hypothesis forfor Straight length of wire Tooth 1Tooth 1 Tooth 2Tooth 2 Tooth 3Tooth 3 Tooth 4Tooth 4 Tooth 1 : 0Tooth 1 : 0 Tooth 2 : 10Tooth 2 : 10 Tooth 3 : 20Tooth 3 : 20 Tooth 4 : 30Tooth 4 : 30 -19.5-19.5 00 00 19.519.5 Tooth 1 : -2Tooth 1 : -2 Tooth 2 : 10Tooth 2 : 10 Tooth 3 : 20Tooth 3 : 20 Tooth 4 : 28Tooth 4 : 28 -15.3-15.3 -3.8-3.8 44 15.115.1 Torque on teeth (N mm)Torque on teeth (N mm)
  28. 28. 28 ActivationActivation Torque on teeth (N mm)Torque on teeth (N mm) LeftLeft LateraLatera ll LeftLeft CentralCentral RightRight CentralCentral RightRight LateralLateral R. Lateral : 0R. Lateral : 0 R. Central : 10R. Central : 10 L. Central : 20L. Central : 20 L. Lateral : 10L. Lateral : 10 33.133.1 -1.68-1.68 8.978.97 -19.46-19.46 Verification of Isaacson’sVerification of Isaacson’s hypothesis -forhypothesis -for curvedcurved anterioranterior segmentsegment
  29. 29. 29 Verification of Isaacson’sVerification of Isaacson’s hypothesishypothesis  Thus the clinical picture may be slightlyThus the clinical picture may be slightly different because ofdifferent because of curvaturecurvature in thein the archwire andarchwire and different inter-bracketdifferent inter-bracket distances.distances.
  30. 30. 30 II. Stepwise resolution of anteriorII. Stepwise resolution of anterior TorqueTorque  IncrementalIncremental twisting bendstwisting bends between 13, 12,between 13, 12, 11 also 21, 22, 23.11 also 21, 22, 23. XX XX
  31. 31. 31 Amount of torque (Degrees) Torque on each tooth (Nmm) Central Lateral Canine Central : 20 Lateral : 10 30.74 -6.53 -13.76 Central : 18 Lateral : 12 Canine : -2 22.53 -0.23 -8.11 Central : 16 Lateral : 12 Canine : -4 17.62 -0.14 -0.08 Central :14 Lateral :12 Canine :-4 12.91 3.69 -0.06 Central :12 Lateral :12 Canine :-4 8.11 7.58 -0.08 Central :10 Lateral :10 Canine :-4 6.8 4.97 2.64 Stepwise resolution of anterior progressive torque
  32. 32. 32 Other situations studiedOther situations studied  TorquingTorquing twotwo incisorsincisors in the same directionin the same direction XX XX TorquingTorquing fourfour incisors,incisors, with twists onlywith twists only between 13 & 12 andbetween 13 & 12 and 22 & 23.22 & 23.
  33. 33. 33 Lingual Root Torque for Central Incisors Amount of torque (Degrees) Torque on each tooth (Nmm) Central Lateral Canine 10 23.94 -19.46 8 15.8 -9.15 -2.76 6.5 9.49 -1.22 -4.8 5 3.4 6.43 -6.9 cent-5 latr-3.5 5.8 1.71 -4.84
  34. 34. 34 Lingual Root Torque on Four Incisors Amount of torque (Degrees) Torque on each tooth (Nmm) Central Lateral Canine cent and lat – 10 canine 0 6.81 12.93 -13.76 cent and lat - 8 canine -2 5.51 6.26 -2.64 cent and lat - 6 canine -2 4.1 3.6 0.17
  35. 35. 35 Individual Root Torque – Right centralIndividual Root Torque – Right central incisorincisor WireWire size/size/ alloyalloy Act.Act.   Torque on each tooth (Nmm)Torque on each tooth (Nmm) L.L. LateralLateral L.L. CentralCentral R.R. CentralCentral R.R. LateralLateral R.R. CanineCanine 19x25/19x25/ ssss 1010 -15.37-15.37 39.1939.19 -19.29-19.29 19x25/19x25/ ssss 88 -3.81-3.81 --4.14.1 24.6824.68 --9.149.14 -2.82-2.82 17x25/17x25/ ssss 1010 -11.97-11.97 30.2130.21 -14.96-14.96 17x25/17x25/ ssss 88 -2.96-2.96 -3.24-3.24 1919 --7.117.11 -2.2-2.2
  36. 36. 36 III. The effect of built-in torque usingIII. The effect of built-in torque using MBTMBT prescriptionprescription  The results are different depending on theThe results are different depending on the torque in cuspid brackettorque in cuspid bracket (-7, 0 or +7)(-7, 0 or +7)
  37. 37. 37 MBT Actual Clinical momentMBT Actual Clinical moment valuesvalues  The high FEM values do not apply (forThe high FEM values do not apply (for untorqued arch wire) in clinical practiceuntorqued arch wire) in clinical practice because of about 10 degrees of wire-slotbecause of about 10 degrees of wire-slot play. But theplay. But the trends seen are importanttrends seen are important..  However, if the 19x25 SS wire is givenHowever, if the 19x25 SS wire is given additional torqueadditional torque that overcomes the play,that overcomes the play, then the FEM values would be close to thethen the FEM values would be close to the Clinical.Clinical.
  38. 38. 38 MBT Cuspid -7MBT Cuspid -7 Amount ofAmount of torquetorque (Degrees)(Degrees)   Torque on each tooth (Nmm)Torque on each tooth (Nmm) CentralCentral LateralLateral CanineCanine PremolarPremolar Central:Central: 1717 Lateral:Lateral: 1010 Canine:-7Canine:-7 23.4223.42 13.413.4 -42.56-42.56 (13.93)(13.93) Central:Central: 1515 22.1222.12 6.896.89 --31.7931.79 (10.4)(10.4)
  39. 39. 39 MBT Cuspid 0 and +7MBT Cuspid 0 and +7 Amount ofAmount of torquetorque (Degrees)(Degrees)   Torque on each tooth (Nmm)Torque on each tooth (Nmm) CentralCentral LateralLateral CanineCanine PremolarPremolar Central: 17Central: 17 Lateral: 10Lateral: 10 Canine: 0Canine: 0 23.4223.42 -0.58-0.58 -13.76-13.76    Central: 17Central: 17 Lateral:Lateral: 1010 Canine:7Canine:7 23.4223.42 10.2210.22 15.0515.05 (-13.93)(-13.93)
  40. 40. 40 MBT Inverted lateral bracketMBT Inverted lateral bracket Amount ofAmount of torquetorque (Degrees)(Degrees)   Torque on each toothTorque on each tooth (Nmm)(Nmm) CentralCentral LateralLateral CanineCanine PremolaPremola rr Central: 17Central: 17 Lateral:Lateral: -10-10 Canine: 7Canine: 7 57.6757.67 -79.35-79.35 42.5642.56 (-13.93)(-13.93) Central: 17Central: 17 Lateral:Lateral: -10-10 Canine: 0Canine: 0 57.6757.67 -65.37-65.37 13.7613.76   ------
  41. 41. 41  IS IT A GOOD IDEA TO INVERT THEIS IT A GOOD IDEA TO INVERT THE LATERAL BRACKETLATERAL BRACKET ( especially( especially alongside a cuspid bracket with +7alongside a cuspid bracket with +7 torque)?torque)?  Even after discounting 40 N mm momentEven after discounting 40 N mm moment due to 10 degrees play, the momentsdue to 10 degrees play, the moments generated are high.generated are high.  UseUse NitiNiti rectangular wires before SSrectangular wires before SS
  42. 42. 42 IV. Torquing Moments from variousIV. Torquing Moments from various wireswires  The torsional stiffness ratio of SS : TMA :The torsional stiffness ratio of SS : TMA : NiTi isNiTi is 10 : 3 : 1.10 : 3 : 1.  Torquing moments from heavy SS wiresTorquing moments from heavy SS wires are high and often above, those from TMAare high and often above, those from TMA generally within and those from NiTi belowgenerally within and those from NiTi below thethe physiologic limitphysiologic limit..
  43. 43. 43 Clinical recommendationsClinical recommendations  Twists in the rectangular archwireTwists in the rectangular archwire seem to beseem to be appropriateappropriate only when reciprocal torque isonly when reciprocal torque is requiredrequired on the adjacent teeth, but beware ofon the adjacent teeth, but beware of high moments. (‘Usehigh moments. (‘Use undersizeundersize wires’- Thurow)wires’- Thurow)  In other situations, this method to cause activeIn other situations, this method to cause active root torque appears mechanically androot torque appears mechanically and biologically unsoundbiologically unsound (often high moments(often high moments which drop suddenly, also round tripping)which drop suddenly, also round tripping)
  44. 44. 44 Clinical recommendationsClinical recommendations ForFor active torquingactive torquing with twists in the rectangularwith twists in the rectangular wires,wires, TMATMA wires should be considered.wires should be considered. The rectangular nearThe rectangular near full size SS wiresfull size SS wires can becan be used thereafterused thereafter for holding the teethfor holding the teeth in theirin their corrected torque positions.corrected torque positions.
  45. 45. 45 Clinical recommendationsClinical recommendations  TheThe moments generated by the NiTimoments generated by the NiTi archwires even in 19x25 arearchwires even in 19x25 are too lowtoo low toto bring about active torquing of teethbring about active torquing of teeth overover long periodslong periods..  However, they may proveHowever, they may prove beneficialbeneficial whenwhen reciprocal torquereciprocal torque is needed on adjacentis needed on adjacent teeth.teeth.
  46. 46. 46 Clinical recommendationsClinical recommendations Alternate methodsAlternate methods proposed by authors likeproposed by authors like Thurow, DeAngelis and Burstone/IsaacsonThurow, DeAngelis and Burstone/Isaacson deserve a serious attentiondeserve a serious attention whenwhen reciprocalreciprocal torque on adjacent teeth is not neededtorque on adjacent teeth is not needed, and, and round tripping is to be avoided.round tripping is to be avoided. The reciprocalThe reciprocal reactionsreactions of these are spreadof these are spread on many (often distant) teethon many (often distant) teeth, and are, and are controlled more easily.controlled more easily.
  47. 47. 47 Alternate torquing methodsAlternate torquing methods (Thurow)(Thurow)
  48. 48. 48 Alternate torquing methodsAlternate torquing methods (DeAngelis)(DeAngelis) Warren Spring
  49. 49. 49 Alternate torquing methodsAlternate torquing methods (Burstone, Isaacson)(Burstone, Isaacson)
  50. 50. 50 TwistTwist in the wirein the wire v/sv/s TorqueTorque of teethof teeth  Angle’sAngle’s torque control concepttorque control concept is inseparableis inseparable from good orthodontic practice.from good orthodontic practice.  However, hisHowever, his “twists” in the rectangular wire“twists” in the rectangular wire for attaining torque should be employedfor attaining torque should be employed judiciously, and not indiscriminately.judiciously, and not indiscriminately.
  51. 51. 51 THANKS TOTHANKS TO Co-Authors:Co-Authors: Prof. Satish Annigeri (B.V.B. EngineeringProf. Satish Annigeri (B.V.B. Engineering College, Hubli),College, Hubli),  Dr. Chetan V. Jayade,Dr. Chetan V. Jayade,  Dr. Punit Thawani.Dr. Punit Thawani.
  52. 52. 52 THANK YOUTHANK YOU
  53. 53. 53
  54. 54. 54
  55. 55. 55
  56. 56. 56 Young’s modulus and Poisson’sYoung’s modulus and Poisson’s ratioratio Young’sYoung’s ModulusModulus Poisson’sPoisson’s RatioRatio StainessStainess SteelSteel 179000 N/mm179000 N/mm22 0.30.3 TMATMA 71700 N/mm71700 N/mm22 0.30.3 NitinolNitinol 41400 N/mm41400 N/mm22 0.30.3
  57. 57. 57 Moments generated by SSMoments generated by SS WiresWires Clinical SituationClinical Situation Amount ofAmount of torquetorque (Degrees)(Degrees)   Torque on each tooth (Nmm)Torque on each tooth (Nmm) CentralCentral LateralLateral CanineCanine Lingual rootLingual root torque on twotorque on two central incisorscentral incisors 1010 23.9423.94 -19.46-19.46 Lingual rootLingual root torque on two all 4torque on two all 4 incisors -incisors - progressive rootprogressive root torque - liketorque - like Isaacson'sIsaacson's Central :Central : 2020 Lateral :Lateral : 1010 30.7430.74 -6.53-6.53 -13.76-13.76 Pre adjustedPre adjusted EdgewiseEdgewise Prescription - MBTPrescription - MBT Central: 17Central: 17 Lateral:Lateral: -10-10 57.6757.67 -99.17-99.17 83.4383.43
  58. 58. 58 Individual Root Torque – Right centralIndividual Root Torque – Right central incisorincisor WireWire size/size/ alloyalloy Act.Act.   Torque on each tooth (Nmm)Torque on each tooth (Nmm) L.L. LateralLateral L.L. CentralCentral R.R. CentralCentral R.R. LateralLateral R.R. CanineCanine 19x25/19x25/ TMATMA 1010 -6.16-6.16 15.7115.71 -7.73-7.73 19x25/19x25/ TMATMA 88 -1.53-1.53 -1.64-1.64 9.899.89 -3.66-3.66 -1.13-1.13 17x25/17x25/ TMATMA 1010 -4.79-4.79 12.112.1 -6-6 17x25/17x25/ TMATMA 88 -1.19-1.19 -1.31-1.31 7.617.61 -2.85-2.85 -0.88-0.88
  59. 59. 59 Ineffectiveness ofIneffectiveness of ProgressiveProgressive IncrementalIncremental Torque (Isaacson)Torque (Isaacson)
  60. 60. 60 Some AssumptionsSome Assumptions  The differences in theThe differences in the sizes and shapes ofsizes and shapes of rootsroots of various teeth were generallyof various teeth were generally disregarded. Also, thedisregarded. Also, the periodontal andperiodontal and alveolar bone supportalveolar bone support to all the teeth wereto all the teeth were considered as uniform.considered as uniform.  All the archwire materials viz. stainlessAll the archwire materials viz. stainless steel, T.M.A. and Niti were considered tosteel, T.M.A. and Niti were considered to havehave linear elastic propertieslinear elastic properties (hence,(hence, applicable only to work hardened NiTi).applicable only to work hardened NiTi).
  61. 61. 61 Basic Premise of the EdgewiseBasic Premise of the Edgewise ApplianceAppliance An ideally shaped rectangular archwire,An ideally shaped rectangular archwire, would move the teeth to the desired finalwould move the teeth to the desired final positions because of its close fit in thepositions because of its close fit in the rectangular bracket slots.rectangular bracket slots. Is this movement a direct translation of theIs this movement a direct translation of the teeth along the shortest route, or does itteeth along the shortest route, or does it involve “round tripping” of some of theinvolve “round tripping” of some of the teeth, if not all?teeth, if not all?
  62. 62. 62 P.A.E. AppliancesP.A.E. Appliances  Same implicit understanding of P.A.E.Same implicit understanding of P.A.E. appliances also (which use continuousappliances also (which use continuous archwires) : the archwire bracketarchwires) : the archwire bracket relationship would cause the teeth torelationship would cause the teeth to move from their malaligned positions tomove from their malaligned positions to the correct positions.the correct positions.  Again, is there a possibility of someAgain, is there a possibility of some amount of round tripping?amount of round tripping?
  63. 63. 63 Aims and objectivesAims and objectives 6. To study the possible actions and6. To study the possible actions and reactions generated byreactions generated by alternativealternative torquing mechanismtorquing mechanism such as a Warrensuch as a Warren spring, and compare these with those fromspring, and compare these with those from the conventional archwire twist.the conventional archwire twist.
  64. 64. 64 Some AssumptionsSome Assumptions  All brackets perfectly leveled and aligned.All brackets perfectly leveled and aligned.  Root apices of teeth undergoing torqueRoot apices of teeth undergoing torque move bymove by 1.5 to 2 degrees per month1.5 to 2 degrees per month (based on what is commonly observed in(based on what is commonly observed in the clinical practice, and also fromthe clinical practice, and also from Creekmore’s interview).Creekmore’s interview).
  65. 65. 65 Isaacson - Kesling DebateIsaacson - Kesling Debate
  66. 66. 66 Isaacson Kesling DebateIsaacson Kesling Debate
  67. 67. 67 Isaacson - Kesling DebateIsaacson - Kesling Debate
  68. 68. 68  ““Orthodontic practice is nothing but push, pull andOrthodontic practice is nothing but push, pull and twist”.twist”.  Angle introduced theAngle introduced the “twist”“twist” in the talein the tale thatthat dramatically changed the script of orthodonticdramatically changed the script of orthodontic mechanics.mechanics.
  69. 69. 69 Isaacson’s hypothesisIsaacson’s hypothesis 1R
  70. 70. 70 Advantages of FEMAdvantages of FEM When properly appliedWhen properly applied  It couldIt could obviate the needobviate the need for the use offor the use of elaborate laboratory (often invasive)elaborate laboratory (often invasive) procedures.procedures.  ItsIts accuracyaccuracy is very high.is very high.  It canIt can segregatesegregate the effects of bending fromthe effects of bending from those of twisting in curved members (e.g.,those of twisting in curved members (e.g., Archwire).Archwire).
  71. 71. 71 MethodologyMethodology  Appropriate values for Young’s Modulus andAppropriate values for Young’s Modulus and Poisson’s ratio were given.Poisson’s ratio were given.  As per the expert advice,As per the expert advice, it was not necessaryit was not necessary to model the bracketsto model the brackets, since applying, since applying appropriate boundary conditions at the locationappropriate boundary conditions at the location of the brackets simulates wire-bracket inter-of the brackets simulates wire-bracket inter- face.face.
  72. 72. 72 Optimum Torquing momentsOptimum Torquing moments  A light torquing spring with 3 to 4 N mm momentA light torquing spring with 3 to 4 N mm moment was shown to cause no tissue damage bywas shown to cause no tissue damage by ReitanReitan..

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