3. 3
Dr. Richard McLaughlin
Dr. Richard McLaughlin completed his orthodontic training at the
University of Southern California in 1976.
Full time practice of orthodontics in San Diego, California.
Dr. McLaughlin is an Associate clinical professor at the University
of Southern California, Department of Orthodontics.
4. 4
Dr. John Bennett
Dr. Bennett completed his orthodontic training at the Eastman Dental
Institute in London, England in 1972.
Full time practice of orthodontics in London, England.
He is currently a part time clinical instructor at the postgraduate
orthodontic program at Bristol University in England.
5. 5
Dr. Hugo Trevisi
Dr. Hugo Trevisi received his dental degree in 1974 at Lins College
of Dentistry in the state of Sao Paulo, Brazil.
Full time practice of orthodontics in Presidente Prudente, Brazil.
He is a Faculty Member at the University of Odontology and
Dentistry in Presidente Prudente.
6. 6
CONTENTS:
Introduction:
The work of Andrews & Roth
The work of McLaughlin & Bennett –
(1975- 1993),(1993 – 1997)
The work of McLaughlin , Bennett & Trevisi ,
( 1997 – 2001)
Fundamentals of treatment mechanics
MBT treatment philosophy:
Bracket selection
Versatility of the system
Accuracy of bracket positioning
7. Light continuous forces
0.022 versus 0.018 slot
Anchorage control early in the treatment
Group movement
Arch forms
Arch wire sequence
Arch wire hook & ligation
Anchorage control during tooth leveling and aligning.
An overview of Class II treatment.
7
8. 8
• An overview of Class III treatment.
• Space closure and sliding mechanics.
• Finishing the case.
• Appliance removal and retention protocols.
• Conclusion.
• References.
9. INTRODUCTION
In this era of progression, the truths of today become the myths
of tomorrow.
Straight wire appliance (SWA)developed by Andrews
dramatically changed the concept of the standard edgewise
appliance system.
Andrews published his land mark article in 1972 and
subsequently designed an appliance based on his findings.
9
10. Andrews made extensive measurements on untreated and treated
excellent occlusions. 120 models were compared with 1150 treated
cases which he collected from orthodontists all over USA
The best in treatment results and the best in nature revealed the
differences between the right and wrong.
He determined the average tip and torque angles and in/out
dimensions of the labial surface of each tooth relative to a flat labial
arch wire plane.
10
11. These dimensions, representing the goals of individual tooth positions,
were then used to fabricate brackets for each tooth. When each bracket
was precisely positioned at the midpoint of the facial axis and aligned
with the facial axis, they collectively became the Straight wire
appliance (A Company, Inc., San Diego, Calif.).
This, in effect, orients the arch wire slot for a specific tip, torque, and
rotation angle, plus height and in/out dimensions to the facial surface of
each tooth.
11
12. FUNDAMENTALS OF TREATMENT MECHANICS
Bracket
selection
Arch wire
selection
Force levels
Bracket
positioning
12
13. 13IMPORTRANCE OF THE SIX KEYS.
They are a complete set of indicators of optimal occlusion .
They can be judged from tangible landmarks .
They can be adjudged from the facial and occlusal surfaces of the crown ,
reducing the need for a lingual view .
Proper diagnosis and treatment planning .
Consistent with nature’s plan aesthetically and functionally.
The Six keys to normal occlusion, Lawrence F. Andrew, 1972
14. 14SIX KEYS TO OPTIMAL OCCLUSION
KEY 1 : INTERARCH RELATIONSHIP
The Six keys to normal occlusion, Lawrence F. Andrew, 1972
15. 15Key 2 : CROWN ANGULATION (the Mesiodistal tip of the crown)
The Six keys to normal occlusion, Lawrence F. Andrew, 1972
16. 16
KEY 3 :CROWN INCLINATION (Labiolingual or Buccolingual
inclination).
The Six keys to normal occlusion, Lawrence F. Andrew, 1972
17. 17
When the upper anterior crown are insufficiently
inclined, upper posterior crowns are forward of their
normal position.
But when the anterior crowns are properly inclined,
one can see how the posterior teeth are encouraged
into their normal positions
The Six keys to normal occlusion, Lawrence F. Andrew, 1972
20. Difficulties with SWA:
When original SWA became available in 1972 , it was based on science but
included many features of Siamese edgewise brackets .
Although SWA was radically new , traditional heavy forces continued to be
used .
No anchorage control measures .
He also emphasized wagon wheel effect where tip is lost due to addition of
torque . hence he chose to add additional tip to the anterior brackets.
20
21. As you place torque in the anterior part of the arch wire you negate tip by a
ratio of four-to-one.(Andrews, L. F.: Six Keys to Normal Occlusion. Am. J.
Orthodontics, 62:296-309, 1972).
21
22. “ROLLER COASTER EFFECT”
Difficulties with increased tip and heavy forces resulted
in lateral open bite.
22
23. These experience led Andrews to introduce a series of
modifications
• For extraction cases, canine bracket with anti tip ,anti
rotation and power arm
• 3 Different sets of incisor brackets for varying degree of
torque in different clinical situations.
Wide range of
brackets
Various arch forms
Bracket at center
of clinical crown
Heavy force level
SWA
23
24. THE WORK OF ROTH
( II Generation of
PEA)
Following his experience with original SWA , Roth introduced
measures to overcome day to day shortcomings .
Roth tried to avoid the inventory difficulties of a multiple
bracket system ( “minimum extraction series brackets to
manage both extraction & non extraction).
24
Roth,RH.: Five Year Clinical evaluation of Andrews Sraight wire
appliance,J.clin.orthod.10:836-850,1976.T
25. He emphasized the use of articulators for diagnostic records, for early Splint construction
and use of gnathalogical positioners to get correct condyle position.
His basic area of interest has been in the relationship of gnathological concepts to
orthodontics. He devoted much of his time and effort into determining what the posterior
occlusal relationships should be for the natural dentition so as to achieve a good functional
occlusion on a more routine basis after completion of orthodontic mechanotherapy.
25
30. THE WORK OF MCLAUGLIN AND BENNETT
BETWEEN 1975 AND 1993:
They worked mainly with standard SWA
Instead of initially modifying the basic bracket design , for more than
15 years they developed and refined treatment mechanics based on
sliding mechanics and continuous light forces .
These mechanics were published initially as series of papers in early
1990 and then as a book in 1993.
30
32. 32
Accurate bracket positioning with lace backs and bendbacks
for early anchorage control .
Sliding mechanics on .019 x .025 steel rectangular wires , with
light .014 finishing wires.
Unlike Andrews non extraction cases , many patients were
children with malocclusion.
33. THE WORK OF MCLAUGHLIN, BENNETT AND TREVISI -1993
AND 1997
• McLaughlin and Bennett then worked with Trevisi to re-design the entire bracket
system to complement their proven philosophy.
• They re-examined Andrews original findings and took into account research input
from Japanese sources when designing MBT bracket system.
33
34. New range of
MBT brackets
Ovoid arch
wire selection
Light force &
sliding
mechanics
Bracket
position with
the help of
gauge
34•This is third generation bracket system , it is a version of preadjusted
bracket system specifically for use with light, continuous forces,
lacebacks and bendbacks and it was designed to work ideally with
sliding mechanics .
35. 35
In Roth and SWA , Additional anterior tip was a
disadvantage .
• It created a significant drain on antero posterior anchorage
• It increased the tendency to bite deepening during alignment
stage
• It brought the upper canine root apex too close to first premolar
in some cases.
36. •A total of 10 deg less distal root tip in upper ant segment
and 12 deg less tip in lower anterior segment is needed.
36
37. 37
The PEA system is a development of edgewise bracket which is
relatively ineffecient in delivering torque.
So in MBT system it was necessary to build extra torque in incisor and
molar region .
38. SWA MBT
U: Lateral incisor
SWA MBT
U: Central incisor
• The most common torque need for the upper incisors during
orthodontic treatment is increased palatal root torque. This torque
tends to be lost during the stages of overjet reduction and space
closure.
38
39. SWA
MBT
• The most common torque need for the lower incisors is labial
root torque to bring them into a more upright position. This is
because they tend to be inclined labially due to elimination of
crowding, leveling of the curve of Spee, and the use of Class II
mechanics elastics.
L: Incisor
39
40. THE WORK OF MCLAUGHLIN ,BENNETT,AND TREVISI BETWEEN -
1997 AND 2001
It became necessary to address the subjects of arch wire selection and force levels
New range of
MBT brackets
Ovoid, tapered,
square arch
wire selection
Bracket
position with
the help of
gauge
Updated light
force level &
Sliding
mechanics
40
43. OVERVIEW OF MBT TREATMENT PHILOSPHY
Light continuous forces
Bracket selection
Versatility of bracket system
Accuracy of bracket positioning
The .022 versus .018 inch slot
Anchorage control early in treatment
Group movement
The use of three arch forms
One size of rectangular steel wire
Arch wire ligation
Awareness of tooth size discrepancies
Persistence in finishing
43
44. 44
LIGHT CONTINUOUS FORCES:
• Comfortable for patient.
• Minimizes threat to anchorage.
• Quantified as below 200gms.
45. 45
Rate of tooth movement under heavy and light continuous orthodontic forces Jason A.Yeea TamerTürkb SelmaElekdağ-
Türk Volume 136, Issue 2, August 2009, AJODO
Initial tooth movement would benefit from light forces. Heavier forces tend to
increase the rate and the amount of canine retraction but lose their advantage
because of unwanted clinical side effects.
Storey And Smith (1952) proposed their theory of “optimal force”. According to this
theory, there is optimal range of force that produce maximum tooth movement. When
force is increased above this range, tooth movement slows down.
46. 46
BRACKET SELECTION:
Standard metal, mid sized, and clear
ACCURACY OF BRACKET POSITIONING:
• Corner-stone of treatment approach.
• Gauges and individual brackets-positioning charts are
recommended.
47. Design features of bracket system
RANGE OF BRACKETS
Standard size metal brackets.
Mid-size metal brackets.
Esthetic brackets.
IMPROVED I.D SYSTEM
Laser numbering of standard size metal
brackets.
RHOMBOIDAL SHAPE
Reduces bulk and assists accuracy of
bracket placement.
47
48. Drawing of MBT brackets.
Standard size brackets have a
rhomboidal form and numerical
i.d. system.
Drawing of original SWA
bracket.
Dots (upper) and dashes (lower)
were used for i.d purposes.
48
49. 49THE .022’’VERSUS THE .018” SLOT:
• The larger slot allows more freedom of movement for the starting wires, and hence helps
to keep forces light
• Later in treatment, the steel rectangular working wires of .019/.025 have been found to
perform well.
• With the .018 slot, the main working wire is normally .016/.022 or .017/.025
50. 50PLAY OF THE WIRE IN THE BRACKET
• The difference between the slot width and the dimension of the arch wire is termed as
play
• According CREEKMORE ( JCO 1979) For every 0.001 degree of play within the
bracket slot 4 degree of effective torque will be lost.
•The amount of the play wire bracket interface is also influenced by ligation
•If the wire not fully engaged the effective torque decreases.
This play, also called deviation angle, was defined as a rotation movement of
the rectangular archwire from its passive position to a position where two
opposite edges of the archwire contact two opposite walls of the bracket slot
Meling TR, Odegaard J, Seqner D. On bracket slot height: a methodologic study. Am J Orthod Dentofacial
Orthop. 1998 Apr;113(4):387-93.
51. 0.022 / 0.018 inch slot
PEA system works well in 0.022 slot
More freedom of wire in a larger slot in initial phase of treatment
– lighter force
Later in the treatment full slot engagement gives control for
retraction
Rigidity for surgical / fixed functional treatment
51
52. 52
Eric Ray Nease compared 0.018 inch and 0.022 inch slot orthodontic brackets to determine
differences in treatment outcome between the two.
• 0.018” slot are; decreased wire inventory, shorter treatment time (according to
some studies) and increased wire flexibility due to smaller dimension of wires while
the disadvantages of 0.018” slot are; desired third order moment to force ratios
may not be produced by newer orthodontic alloys and less than optimum sliding.
• 0.022” slot are that newer orthodontic alloys can be used with minimum patient
discomfort and optimum clearance for sliding is obtained while the disadvantages
of 0.022” slot are that increased wire inventory is required and there lies an inability
to attain third order control till last stages of treatment.
Nease ER. 0.018” versus 0.022” slot orthodontic brackets: A comparative analysis. Am J Orthod and Dentofacial Orthop. 2000;
53. 53
0.018-inch and 0.022- inch systems; however, one can certainly fill the slot in
the 0.018-inch bracket more efficiently and earlier in treatment. This feature
provides the advantage of early torque control of anterior teeth. Torque
control is essential in the precise positioning of anterior teeth and in the
retraction phase of extraction treatment.
Martin B. Epstein, Benefits and Rationale of Differential Bracket Slot Sizes: The Use of 0.018-Inch and 0.022-Inch Slot
Sizes Within a Single Bracket System, Angle Orthodontist, Vol 72, No 1, 2002
54. 54
Sifakakis et al (2012) assessed the effect of the moments generated with low- and high
torque brackets.It was found that high-torque brackets produced higher moments compared
with low-torque brackets.
Additionally, in both high- and low-torque configurations, the thicker 0.019 × 0.025 inch
steel archwire in the 0.022 inch slot system generated lower moments in comparison with
the 0.017 × 0.025 inch steel archwire in the 0.018 inch slot system
Sifakakisa I, Pandis N, Makou M, Eliades T, Katsaros C, Bourauel C. Torque expression of 0.018 and 0.022 inch conventional
brackets. European Journal of Orthodontics. 2012
55. Although an ovoid arch form had proved useful in the early years
Three basic arch form
Tapered ,
Square And Ovoid
When superimposed they vary mainly in the inter canine & inter premolar area,
giving a range of 6 mm.
ARCH WIRE FORMS :
55
57. 57
• Lacebacks are .010 or .009 ligature wires which extend from the most
distally banded molar to the canine bracket.
• Bendbacks help to prevent mesial movement of the anterior teeth and ensure
comfortable positioning of the archwire ends in the molar regions.
• If the archwire is bent back immediately behind the tube on the most distally
banded molar, this serves to minimize forward tipping of incisors.
58. 58
GROUP MOVEMENT:
• Where possible, group movement is carried out, and the upper and lower anterior segments are
managed as a group of six or eight teeth.
• In situation A, the space has been closed by mesial movement of molars and premolars - a
minimum anchorage treatment.
• In situation B, the incisors and canines have been retracted into the available space - a maximum
anchorage situation as might occur in a Class III case or a bimaxillary protrusion.
61. 61
AWARENESS OF TOOTH SIZE DISCREPANCIES:
It is part of the technique to assess tooth size at the treatment
planning stage and throughout treatment.
PERSISTENCE IN FINISHING:
In the closing stages of treatment, light wires such as .014 steel are
used, and archwire bends are frequently required.
62. 62
Roth once said :
“The A-company’s SWA as developed by L. Andrews is truly a SWA
from the stand point of a level slot lineup.
… i.e. all the slots of the brackets are at the same height and level in all
three dimensions when the teeth are in the correct positions”.
MBT Treatment mechanics manual by Dr K Sadashiva Shetty- 2016
63. 63
This is accomplished by the contours for torque, rotations and in-out being
built into the base of the brackets.
It is physically impossible to achieve this slot lineup with any appliance
that does not have the compound contoured base with torque in the base.
64. Torque in base
Torque in face
Long axis point, the base point and the
slot point were on the horizontal plane.
64
The torque in the base means that the bracket stem is parallel and coincides with the long
axis of the bracket slot.
Torque in the face the slot is cut at an angle to the bracket stem, therefore their long axis do
not coincide and are not parallel to each other
65. 65TORQUE IN THE BASE Vs. TORQUE IN THE FACE
• Torque-in-base was an important issue with the first and second generation
pre adjusted brackets, because level slot line-up was not possible with
brackets designed with torque-in-face. Torque in the base is said by Andrews
to be a prerequisite for a fully programmed appliance – that is, one that
produces acceptable results without arch wire bends, assuming the brackets
are placed correctly.
• Albert H.Owen in 1991 conducted a study comparing Roth Prescription and
the Vari Simplex Discipline appliance of Alexander concluded that while
torque in the base had a sound theoretical basis, its effectiveness is greatly
influenced by the clinician’s success in accurately.
TORQUE IN THE BASE Vs. TORQUE IN THE FACE, Albert H Owen, 1991, JCO
66. 66TORQUE IN BASE - THE COMPUTER-AIDED
DESIGN (CAD) FACTOR:
Modern bracket systems, including the MBT system,
have been developed using computer aided design and
computer-aided machining - the CAD-CAM system.
This allows more flexibility of design, not only to place
the slots in the correct position in the brackets, but also
to enhance bracket strength and features such as depth
of tie wing and labio-lingual profile.
67. Present
During 1st & 2nd generation PEA brackets, technology was not available to
set bracket slots in the correct position relative to the facial surfaces of the
crowns ( i.e. level slot lineup) without torque-in-base.
With the introduction of CAD-CAM, however, the torque-in-base concept
has been given less importance.
67
68. 68
Modern bracket systems, including the MBTTM system, have been
developed using CAD-CAM.
However, at present this is available with the Mid-Size MBT brackets only.
69. Torque in base: computer aided design ( CAD)
1. Torque in base ( full size and clear) or
2. Combination of torque in base and torque in face (mid size)
69
70. 70CLASSIFICATION OF ORTHODONTIC FORCES
Schwarz (1932): force magnitude and tissue response:
First degree of efficiency:
• Below threshold to stimulate tooth movement and also of too short duration.
• But if duration increased – tooth movement
Second degree of efficiency:
•Most favorable for continuous tooth movement without root resorption.
• Resorption of bone at same rate as apposition.
• Weaker than blood pressure in capillary blood vessels – 15 to 20 gm/cm2 –
duration.
71. 71
Third degree of efficiency:
• Interrupt the blood circulation in periodontal membrane.
• Medium strength – 20-50gm/cm2.
• Tissue not yet crushed.
• If interrupted – bone remodeling continuous
• Necrosis of periodontal membrane most common cause of root resorption.
Fourth degree of efficiency:
• Forces of this magnitude crushes primary ligament irresponsible damage to the
affected tissues necrosis of alveolar bone and root resorption.
Biological Mechanism Of Tooth Movement- 2nd Edition By Vinod Krishnan
72. 72IN-OUT SPECIFICATION
Expression of in-out:
The in-out feature of preadjusted brackets is 100% fully expressed, because the archwire
lies snugly in the slot.
The labio-lingual movement is rapid, and normally occurs in one visit. The original
SWA in-out specification was therefore used as a basis when designing the MBT system.
73. 73
Andrews used the term “prominence” to describe what is known as “in-and-out,” and he
measured it from a line called the “embrasure line.” This was defined as “an imaginary line
at the level of the crown's midtransverse plane that would connect the most facial portions of
the contact areas of all crowns in an arch when theyare optimally positioned.”
Richard P. McLaughlin ,John C. Bennett, Evolution of treatment mechanics and contemporary appliance design in
orthodontics: A 40-year perspective, June 2015 AJODO
74. Upper Second Premolars have small crowns
A bracket which is 0.5mm thick helpful in obtaining good
alignment of marginal ridges
74 UPPER SECOND PREMOLARS:
77. 77
For all molars, a 0° tip bracket is recommended. If placed parallel
to the buccal cusps of the molars, a 0° lip bracket will deliver 5° of
tip for the uppers and 2° of tip for the lowers.
80. 80
Torque is not efficitently expressed by the preadjusted appliance system, partly due to
the small area of torque application.
A rectangular .019/.025 steel wire in .022 slot will have approximately 10" of 'slop'. The
exact amount depends on the precision of manufacture of the wire and bracket slot and
the amount of wire edge 'rounding' or 'radiusing.
81. 81
Incisor torque
• It is helpful clinically to have torque control which moves upper incisor
roots palatally and lower incisor roots labially.
• Class II cases, where Class II elastics can cause torque to be 'lost' on the
upper incisors, and where lower incisors tend to procline during leveling
and in response to Class II elastic.
• Class I cases, where correct incisor torque helps to achieve good anterior
tooth fit.
82. 82• There is generally a need for greater palatal root torque of the upper incisors and for more
labial root torque of the lower incisors.
• For these reasons, the authors recommend +17° of torque for the upper central incisors,
+10° of torque for the upper lateral incisors, and -6° of torque for the lower incisors
85. 85
• For upper molars, on the other hand, the -9° of the original SWA has proven to be
inadequate, and they prefer -14°, as this gives better control of the palatal cusps.
• The -14° specification for the upper molars helps to reduce interferences during
function, by preventing the palatal cusps from hanging down.
UPPER MOLAR TORQUE
86. 86LOWER PREMOLAR AND MOLAR TORQUE
• The authors have recommended substantial changes in torque features for the attachments
in the lower buccal segments, compared with the original SWA.
• This reduces the 'rolling-in' of lower molars as well as assisting in the development of the
mandibular arch.
89. 89
THE VERSATILITY OF BRACKET SYSTEM
ASPECTS OF VERSATILITY:
Seven main areas of versatility are listed below –
1. Options for palatally displaced upper lateral incisors (-10°).
2. Three torque options for the upper canines (-7°, 0 ° , and +7°).
3. Three torque options for lower canines (-6°, 0 °, and +6°).
90. 904. Interchangeable lower incisor brackets - the same tip and torque.
5. Interchangeable upper premolar brackets - the same tip and torque.
6. Use of upper second molar tubes on first molars in non-HG cases.
7. Use of lower second molar tubes for the upper first and second
molars of the opposite side, when finishing cases to a Class II molar
relationship.
91. PALATALLY DISPLACED LATERAL INCISOR:
• Rotation of bracket to 180 degree makes +10 to -10 torque
• Assists labial root torque at the rectangular wire stage.
91
96. Factors that govern the canine torque options:
6 Factors
Arch form
Canine prominence
Extraction decision / tip control
Overbite
Rapid palatal expansion
Agenesis of upper lateral incisors, when space has to be closed
96
97. ARCH FORMS
Well developed arches less tooth movement required, then -7 upper and -6 in lower.
More ovoid or tapered suggest 0 degree torque bracket for both.
Narrow tapered arch form then +7 upper and +6 in lower
97
99. In prominent canine 0 degree or +7 upper and +6 in lower recommended.
0 degree torque bracket preferred for premolar extraction cases for maintaining the
canine root in cancellous bone.
IN OVERBITE
To move the lower canine crown move labially but to maintain root centered in
the bone 0 degree or +6 lower canine bracket recommended.
If one or both lateral incisors missing bringing the canine mesially close to
centrals then it helpful to invert -7 t0 180 . This changes the torque to +7 but tips
stays same at 8.
99 CANINE PROMINENCE
101. 101 THE EXTRACTION DECISION (TIP CONTROL)
• Brackets with 0° torque for use with canine retraction
mechanics and in any case where it is necessary to
substantially change canine tip.
• The thinking behind this view is that the 0° brackets tend to
maintain the canine roots in cancellous bone, thereby making
tip control of the canine roots easier.
• The 0 degree canine bracket carries a hook, as it is often
considered for cases which require canine retraction
102. 102
RAPID PALATAL EXPANSION CASES:
• After rapid palatal expansion, widening of the upper arch
creates a secondary widening in the lower arch.
• The torque changes (uprighting) among the lower teeth and 0°
or +6° lower canine brackets are recommended.
103. 103AGENESIS OF UPPER LATERAL
INCISORS,WHERE SPACE IS TO BE CLOSED:
• If one or both upper lateral incisors are missing, a decision may
be made to close the spaces, and bring the canines mesially into
contact with the central incisors.
• In this situation, it is helpful to invert the -7° upper canine
bracket 180°.
106. IN NON-HG CASES Use of upper second
molar tubes on first molars
106
-14 torque, 0 tip, 10 antirotation
107. FINISHING TO A CLASS II MOLAR
RELATIONSHIP Use of second molar tubes for
the upper first and second molars of the opposite
side.
107
108. Additional bracket & tube options:
Brackets for smaller upper II premolar
Lower second premolar tube
Lower first molar non convertible tube
Triple tube & double tube
Bondable mini molar tube for second molar
108
109. 109 BRACKET FOR SMALL UPPER
SECOND PREMOLARS:
The thicker bracket option for
small upper second premolars is
helpful in achieving good
alignment of marginal ridges
without wire bending.
110. 110
LOWER SECOND PREMOLAR TUBES:
1)Appliance breakages in the lower second premolar regions
are frequently encountered, even with careful bonding, when
regular brackets are used.
2) The lower second premolar tube is more comfortable and is
normally less liable to breakages than the equivalent bracket.
111. 111 LOWER FIRST MOLAR NON-CONVERTIBLE
TUBES:
Lower first molar non-convertible tubes have many advantages
over the traditional, more bulky, convertible lower first molar
attachments
112. 112 LOWER FIRST MOLAR DOUBLE TUBE AND UPPER FIRST
MOLAR TRIPLE TUBE ATTACHMENTS:
These were introduced for cases where segmental mechanics are
appropriate for the case.
113. 113 BONDABLE MINI SECOND MOLAR TUBES
In instances where a second molar needs to be included, but the tooth is insufficiently
erupted for band placement, a small tube can be bonded to the mesio-buccal area.
They are comfortable and surprisingly effective for aligning the second molar.
114. 114
Inclusion of second molar at the outset does help in enhancing anchorage. It
not only controls the mesial movement of molar but also helps to exercise
control over angular and vertical movement of molars.
Inclusion of mandibular second molars in orthodontic mechanics is relevant not only
for the correction of second molars mesiodistal inclination, but also for first molars
uprighting
Luiz Filiphe Gonçalves Canuto, Karina Maria Salvatores de Freitas Influence of treatment including second molars on final
and postretention molar angulation, Dental Press J Orthod. 2013 Sept-Oct;18(5):121-7
Brig SM Londhe, Lt Col P Kumar, Efficacy of Second Molar to Achieve Anchorage Control in Maximum
Anchorage Cases, MJAFI, Vol. 66, No. 3, 2010
115. 115
Controversies about the necessity of second molars inclusion during orthodontic treatment.-
• Two of the major goals of treatment consist in leveling the curve of Spee and correcting
overbite. Thus, nothing is more rational than using the second molars to provide an anchorage
that allows anterior teeth intrusion and correction of the curve of Spee.
• When using Class II elastics, the second molar inclusion increases arch length. Therefore,
there is not only an increase in the horizontal component of force, but also a decrease of the
vertical component. This fact is generally favorable because it facilitates sagittal interarch
adjustment and prevents first molars extrusion.
Luiz Filiphe Gonçalves Canuto, Karina Maria Salvatores de Freitas Influence of treatment including second
molars on final and postretention molar angulation, Dental Press J Orthod. 2013 Sept-Oct;18(5):121-7
116. 116
• In extraction cases, mandibular second molars inclusion provides posterior anchorage
improvement and avoids inclination and rotation of the first molars. It is also
indicated for cross-bites, proclined or rotated second molars cases as well as surgical
cases.
• However, there are clinical situations in which inclusion of second molars may be
contraindicated, such as in patients with initial anterior open bite and vertical facial
growth tendency.
Luiz Filiphe Gonçalves Canuto, Karina Maria Salvatores de Freitas Influence of treatment including second molars on final
and postretention molar angulation, Dental Press J Orthod. 2013 Sept-Oct;18(5):121-7
118. 118 Setting up of the case is the most important aspect of the treatment, after correct diagnosis
and treatment planning.
Bracket positioning is most important mechanical procedure in the treatment of the patient
Banding and bonding should therefore not to be delegated and should be managed by the
orthodontist, to ensure accuracy of appliance placement.
119. 119
NEED FOR ACCURACY
Accuracy of bracket positioning is essential, so that the built in features of the bracket
system can be fully and efficiently expressed.
This helps treatment mechanics and improves the consistency of the results.
120. 120
FULL OR PARTIAL SET-UP?
For many patients, it is correct to place all the brackets and bands at the start of
treatment so that any discomfort is limited to one episode, and all the teeth start to be
corrected from the outset.
However, in some situations, listed below, it may be beneficial to consider partially
setting up the case, leaving individual teeth, and in some instances groups of teeth,
without attachments
121. 121
o BLOCKED-OUT TEETH:
If individual teeth are vertically or horizontally displaced from the primary arch form, it
is often good technique to delay bracketing the displaced tooth until the other teeth are
well aligned, and space has been made available.
122. 122
o DEEP-BITE CASES:
In some cases, when it has been decided not to use a bite plate or occlusal build-up,
upper arch treatment should be started first.
Later, after the overbite has started to correct, it will be possible to place the lower
incisor brackets without discomfort to the patient or risk of damage to the enamel or
the newly placed brackets.
123. 123o ENAMEL REDUCTION CASES:
It is normally necessary to carry out enamel reshaping in cases with triangular-shaped
incisors. It may be helpful to delay bracketing the incisors, especially in the lower arch
124. IN THE EARLY YEARS OF PEA…
Positioning was done with gauges and standard millimeter measurements from
the incisal /Occlusal edge of each tooth , irrespective of tooth size
Because of this reason patient with large incisors had bracket placed more
incisally than patient with small incisors.
124
125. 125
This variation in relative position on the tooth from patient to patient results
in variations in the in-out position of the bracket and in the amount of the
torque delivered.
126. 126
“ IN THE PAST THE BEST RESULTS WERE ACHIEVED BY THE
ORTHODONTISTS WHO WERE THE BEST WIRE BENDERS. IN THE FUTURE,
THE BEST RESULTS WILL COME FROM THOSE ORTHODONTISTS WHO ARE
THE BEST BRACKET POSITIONERS ‘’–
MBT
127. THEORIES OF BRACKET POSITIONING
The most reliable position is the center of the clinical crown which is relatively the same in
patients with large or small teeth. This position is recommended as the horizontal reference.
( Use of gauges )
The vertical long axis of the clinical crown is selected as the vertical reference for the
bracket positioning
127
128. 128
Angle (1928) initially taught that the best position of the band was where it fits better
mechanically. Then, if possible, the bracket should be placed at the center of the labial
surface of the tooth.
Angle HE. The latest and best in orthodontic mechanism. Dental Cosmos 1928;70:il43; 1929;71:164
Later, placement of the anterior bands at the junction of the middle and incisal thirds has been
recommended ( Balut et al. , 1992 ).
Balut N , Klapper L , Sandrik J , Bowman D 1992 Variations in bracket placement in the preadjusted orthodontic appliance .
American Journal of Orthodontics and Dentofacial Orthopedics 102 : 62 – 67
129. 129
Tweed (1966)suggested the incisal edge as a guideline for linear measurement.
Tweed advocated placing brackets by using linear measurements from bracket slot to the incisal
edges of anterior teeth. In maxillary arch the bracket was placed vertically at a distance of
3.5mm for central incisors, canine and the premolars while for the lateral incisors the distance
was kept at 3 mm.
Mesio-distally for the anteriors it should be at the middle of the tooth and Slot should be
parallel to the incisal edge.
Tamizharasi, Kumar S. Evolution of Orthodontic Brackets..Journal of Ind Acad of Dent Spec. 2010;1:25- 30.
130. 130
Saltzmann advocated the middle third of the crown as the ideal location.
Holdaway (1952) stated the bite to be determinant for bracket positioning, at occlusal third
of the crown if there is an increased overbite and at cervical third in open bite cases.
• Whereas in the mandibular arch ,The incisal edge of bracket slot is placed at 3.5mm to the
incisal edges of incisors and cusp tips of cuspids and premolars.
• On the molars, brackets and molar sheaths are placed at the junction of upper and middle
third of teeth occluso-gingivally. Mesiodistally, mesially bracket should be in line with
the mesio-buccal cusp
131. 131
P.R. Begg(1965) gave the light wire appliance and advocated the differential force mechanics .
Begg brackets are modified ribbon arch brackets.
According to him the brackets are centered mesiodistally on the labial surfaces of teeth with the
base of the arch wire slots 4mm from the incisal edges or cusp tips.
On maxillary laterals at 3.5mm except when tooth is originally displaced lingually (4mm).
Molar tubes should be parallel with the occlusal surface when viewed from the buccal aspect.
Parallel with a line bisecting the occlusal surface of the tooth mesio-distally when viewed from
occlusal.
Tubes on mandibular molars are placed more gingivally to avoid occlusal interferences.
Begg PR, Kesling PC. Begg orthodontic theory and technique. W. B. Saunders Company, Philadelphia; 1977
132. 132Andrews straight wire appliance(1976) gave the concept of an imaginary plane known as “The
Andrews Plane”.
It is a plane that would pass through (Long Axis) LA-points of the crowns of normally occluded
teeth; or, simply the plane would separate the occlusal and gingival portions of the crown at the
LA-point.
133. 133
Andrews advocated placing brackets at the mid-point of the long axis of the
clinical crown, keeping vertical tie wings parallel to the long axis of the clinical
crown and then moving the bracket up or down until the middle of its slot base is
at the same height as the midpoint of the clinical crown.
Andrews LF. The straight-wire appliance, origin, controversy, commentary. Journal of Clinical Orthodontics, 1976;10: 99–114
134. 134Roth developed the second generation of preprogrammed brackets. He modified the Andrews
prescription to allow the teeth to be placed in an overcorrected position
Roth advocated the key in determining bracket height are the canines and premolars.
The center of bracket should be placed at the maximum convexity of crowns of posterior teeth.
Maxillary centrals should be bracketed equal in height to the maxillary laterals. The centrals
will be 0.5 to 1mm longer than the laterals after settling .
Canine tip is kept 1mm longer than the adjacent laterals.
135. 135
Position of anterior brackets are slightly more incisally relative to LA point. Mandibular
central and lateral brackets are kept at same height 0.5 to 1mm shorter than canine
bracket.
Roth recommended more incisal positioning of incisors bracket to level the curve of Spee
with flat archwires rather than placing reverse curves
Roth RH: The Straight-Wire Appliance 17 years later. J Clin Orthod 1987;21:632-42
136. 136
Vari Simplex Discipline
It is one of the pre adjusted edge wise system.
It was introduced in 1978 by Dr. R. G . Wick Alexander.
The name vari – simplex discipline was chosen after very much thought
• “VARI” means the variety of bracket types used ( Twin, Lewis And Lang)
• Simplex refers to the KISS principle.
• Discipline instead of appliance.
137. 137Bracket height :- each bracket is placed at a predetermined position on each tooth
relative to the other teeth. Bicuspid bracket height is the key because its clinical crown
height is so variable.
Its normal bracket slot height is 4.5mm
Maxillary arch:-
Centrals – x
Laterals – x – 0.5
Cuspids – x+0.5
Bicuspids – x
First molars – x-0.5
Second molars – x-1 5
Mandibular arch
Centrals – x-0.5
Laterals – x-0.5
Cuspids – x+ 0.5
Bicuspids – x
First molars – x- 0.5
138. 138The third generation of brackets were developed by McLaughlin, Bennett and Trevisi .
MBT™ Versatile+ Appliance System was launched in 1997.
• It is based on light forces and sliding mechanics maintaining the advantages of the
prescriptions of Andrews and Roth, but eliminating certain limitations.
• They recommended the use of Bracket Placement Chart.
• These charts were developed by using data obtained by measuring anatomical crown
heights and clinical crown heights , American Boards or Angle Society cases and debonded
cases that had settled into good occlusion
McLaughlin R.P, Bennett JC : “Bracket Placement with the Preadjusted Appliance” Journal of Clinical Orthodontics May
1995; 29: 302-311.
139. 139
From this data, a theoretical bracket placement chart was devised from which the user selected
the row of bracket heights which most closely corresponds to the half clinical crown height of
the dentition to be bonded.
Positioning gauges to guide the occlusal-gingival placement of the bracket, from the incisal
edge of the tooth to the bracket slot were used (Boone's Gauge and Dougherty's Gauge)
Petocz P, Darendeliler MA. A comparison of accuracy in bracket positioning between two techniques—localizing the centre of the
clinical crown and measuring the distance from the incisal edge European Journal of Orthodontics 2007; 29: 430-436.
140. 140 When direct bonding, it is helpful to avoid viewing teeth from the sides , or from
above or below. To properly view the teeth during bonding procedures it will be
necessary for the patient to turn the head and for the orthodontist to change seating
from time to time .
141. BRACKET PLACEMENT GAUGE 141
Metallic or wooden jigs are available for bracket heights ranging from 2mm to 5.5mm
from the incisal or occlusal edges, with each jig having a bracket placement gauge on each
end.
142. Modification to the bracket jig: A new tool for orthodontic bracket placement; Prof (Dr.) U.S. Krishna
Nayak & Dr Ankur Aggarwal, JCO, April, 2009.
Regular bracket placement jigs are
Cumbersome to use,
Have to be interchanged frequently during the bonding
procedure,
Cause considerable loss of chair time.
Ankur bracket jig: This all-in-one tool eliminates the need for
multiple bracket placement gauges, thus saving chair time and
improving practice efficiency.
142
143. Ankur's Bracket Jig* (ABJ) replaces these separate
jigs with a single tool consisting of an incisal/
occlusal arm with an engraved millimetric ruler, a
vertical screw, a spring, a horizontal bracket-
engaging arm, and a nut to hold the bracket arm in
place over the spring.
Bracket heights from 2mm to 5.5mm can be set by
rotating the nut clockwise or counterclockwise with
the thumb
143
144. 144New 2D bracket -positioning gauge has been specifically designed for direct bonding A
hand-held instrument with a bracket-positioning blade allows quick and easy
manipulation of orthodontic brackets into the desired positions on the tooth.
Narendra sharma’s 2- dimentional bracket positioner (NS2DBP) replaces these separate
jigs with a single tool
Sharma N, Shrivastav S, Hazarey P. A new 2D bracket positioning gauge.J Ind Orthod Soc.2011; 45:202-04.
146. HORIZONTAL ACCURACY DURING
BRACKET POSITIONING
Flat surfaces of incisors and molars are not much affected by small errors
Canine premolars have curved surface so care must be taken here to avoid bracket
positioning errors or it leads to rotation of these teeth .
Lower canine bracket must be placed on the vertical midline, or slightly mesial to it , to
ensure good contact with the lateral incisors.
146
147. HORIZONTAL BRACKET PLACEMENT ERRORS
If brackets are placed to
the mesial or distal of the
vertical long axis of the
clinical crown, improper
tooth rotation can occur.
147
148. 148
Horizontal accuracy in the canine,
premolar, and molar regions should
be checked with a mouth mirror.
Horizontal and vertical accuracy
can be checked from the buccal
aspect.
149. 149ROTATED INCISORS
On a rotated tooth, the bracket can be bonded slightly more mesially or distally.
In this way, full correction of the rotation can be achieved.
150. VERTICAL ACCURACY DURING BRACKET
POSITIONING
It is the most difficult aspect of bracket positioning and
accuracy is greatly improved by the use of Bracket positioning
charts
It deals with difficulties such as:
o Tooth length discrepancies,
o Labially and lingually displaced roots,
o Partly erupted teeth.,
o Gingival hyperplasia
150
151. VERTICAL ERRORS
Vertical errors in bracket
placement are caused by
placing brackets gingival
or incisal/occlusal to the
center of the clinical
crown.
151
152. GINGIVAL CONCERN.
Partially erupted tooth.
It is difficult to visualize the
center of the clinical crown
on partially erupted teeth ,
when treating young patients.
152
153. GINGIVAL INFLAMMATION
Top: Healthy gingivae.
Bottom :The same case with
inflamed gingivae in the upper
right quadrant.
153
Gingival inflammation causes fore shortening, effectively
reducing the length of the clinical crowns.
154. THICKNESS ERRORS.
Excess bonding agent beneath the
bracket base can cause thickness
and rotational errors.
Can be eliminated by pressing the
bracket against the tooth.
154
155. These will occur if the bracket wings
do not straddle the vertical long axis
of the crown in a parallel manner.
Such errors lead to improper crown
tip.
155
159. Chart individualization in deep bite and open bite cases
In deep-bite cases, it can be helpful to place the incisor and canine brackets 0.5 mm
more occlusally.
In open –bite cases they should be 0.5 mm more gingival
159
160. Upper Molar Band Placement
160
PLACING MOLAR BANDS
SEPARATION
Good separation of posteriors is essential for accurate band positioning in
most cases..
Elastic separating modules or Metal separator can be used
162. 162Placement of brackets in the positions determined by measuring the distance from the
ME appears to be more accurate in the vertical dimension for the upper and lower
anterior teeth.
The extent of error of bracket placement, regardless of which technique was used,
demonstrates that archwire bending adjustments or repositioning of brackets will be
necessary to achieve acceptable treatment results.
Petocz P, Darendeliler MA. A comparison of accuracy in bracket positioning between two techniques—localizing the
centre of the clinical crown and measuring the distance from the incisal edge European Journal of Orthodontics 2007; 29:
430-436.
163. 163
Components Of Arch Form
Anterior Curvature
Inter Canine Width
Posterior Curvature
Inter Molar Width
164. 164
• The preservation of intercanine width is an indispensable part of treatment planning to
reduce the risk of postretention relapse.
• Deviation from the normal transverse relationship might lead to root and
alveolar bone resorption, tipping of teeth, periodontal damage, and
esthetically compromised results.
Little RM, Riedel RA, Stein A. Mandibular arch length increase during the mixed dentition: postretention evaluation of stability and relapse.
Am J Orthod Dentofacial Orthop 1990;97:393-404.
165. 165IMPORTANCE OF ARCH FORMS:
1) STABILITY: Relationship between the arch form and stability cannot be ignored Reidel in one
of his nine theorems for stability have stressed on the need to maintain the existing arch form,
particularly in the mandibular arch for stability
2) OCCLUSION: Unless the teeth are aligned in a proper arch form in both upper and lower
arches, the occlusion will not be normal. Angle(1907) emphasised this with his concept of Line of
Occlusion.
3) ESTHETICS: Primary reason for the patient to take treatment. Teeth arranged in proper arch
form, will improve smile value as proposed by
166. 166NORMAL GROWTH & DEVELOPMENT OF ARCHES-
Arch dimensions change with growth hence it is important to distinguish changes induced
by appliance therapy and by growth.
Acc. to Scott(1967) arch form is determined prior to muscular development and is
independent of functional activity of the oral musculature.
Moorrees(1969) pointed out that considerable individual variation in arch form will occur
with normal growth, with a tendency toward an increase in inter-molar width during
change over from deciduous to permanent dentition.
167. 167DIFFERENT CONCEPTS OF ARCH FORM:
1. BONWILL CONCEPT
2. BONWILL HAWLEY CONCEPT
3. ANGLES LINE OF OCCLUSION
4. APICAL BASE CONCEPT
5. CATERNARY ARCH FORM
6. BRADER ARCH FORM
7. ROCKY MOUNTAIN DATA SYSTEM
8. ROTH’S TRU ARCH FORM
9. RICKETTS PENTA MORPHIC ARCH FORM
10. MATHEMATIC & GEOMETRIC MODELS FOR ARCH FORM
169. 169
BONWILL’S CONCEPT OF ARCH FORM:
Developed certain postulates for artificial dentures in 1885 He noted the tripod shape of
the mandible is formed by an equilateral triangle, with its base between the condyles and
the apex between the central incisors. length of each side approx. 4 inches.
170. 170
BONWILL & HAWLEY ARCH FORM:
• Hawley in 1905, modified Bonwill’s concept.
• He recommended thet the combined widths of the 6
anterior teeth serve as the radius of a circle and the teeth be
placed on that circle.
• From this circle he constructed and equilateral triangle
with the base representing the intercondylar width.
• The radius of each arch varied depending on size of teeth,
so the arch dimensions differed as a function of tooth size
but the arch form was constant.
• This was used as a guide for establishing arch form
171. 171
ANGLE’S LINE OF OCCLUSION
Angle in 1906,described the LINE OF OCCLUSION – “he
line of greatest normal occlusal contact” . But in 1907, he
rediscribed it as “ the line with which in form and in
position according to type, the teeth must be in harmony if
in normal occlusion.”
Ricketts(1997) redefined the line of occlusion to its
contemporary definition – “A distinctively individual line
at the inciso-buccal contact, with a location, position &
form to which the teeth must conform to be in normal
occlusion
172. 172BRADER ARCH FORM
Brader in 1971, presented a mathematical model of
dental arch form at the annual session of A.A.O for
which he won Milo Hellman Research Award Of
Special Merit. He proposed that the arch form was a
trifocal ellipse, which was based on the findings of
Proffit, Norton & Winders. The trifocal ellipse was
patterned after the shape of an egg- extremely
resistant to collapse & produced stable arch form.
173. 173
Traditionally, it was believed that the tongue pressure and the lip and cheek pressure was
equal in magnitude and opposite in direction.
This was disproved by Lear & Moorrees(1969). They found the tongue pressure was always
more than the lip and cheek pressure. Also verified the time- pressure equilibrium
hypothesis. Not only pressure but duration of pressure should also be considered.
174. 174CATERNARY ARCH FORM: Concept first proposed by
David Musich & James Ackerman(1973). To measure the
arch perimeter they used an instrument that was a
modified Boley Guage with a chain incorporated in it -
CATANOMETER
Schulhoff(1977) used the same concept to describe the
lower arch. Caternary curve is the shape that the loop of a
chain would take if it were suspended from 2 hooks. Shape
of the curve depends on the length of the chain and the
distance between the hooks. Caternary Arch
175. 175
Felton(1987) evaluated a wide range of manufactured arch wires from
orthodontic companies and found that the arch forms fell into tapered,
ovoid or square groups ( first classified by Chuck in 1932).
When superimposed they differed only in ICW (approx 6mm).
176. ARCH FORM
Arch form classification (CHUCK et al 1932 )
TAPERED
SQUARE
OVOID
176
Nojima K, McLaughlin RP, Isshiki Y, Sinclair PM. A comparative study of Caucasian and Japanese mandibular clinical arch forms.
Angle Orthod 2001;71:195-200
178. 178
THE TAPERED ARCH FORM:
This arch form has the narrowest inter-canine width and is useful
early in treatment for patients with narrow, tapered arch forms.
It is particularly important to use this form for patients with narrow
arch forms, and especially in cases with gingival recession in the
canine and premolar regions (most frequently seen in adult cases).
Miyake H, Ryu T, Himuro T. Effects on the dental arch form using a preadjusted appliance with premolar extraction in Class I crowding.
Angle Orthod 2008;78:1043-9.
179. 179
THE SQUARE ARCH FORM:
This arch form is indicated from the start of treatment in cases with broad arch
forms.
It is also helpful, at least in the first part of treatment, for cases that require
buccal uprighting of the lower posterior segments and expansion of the upper
arch.
After over expansion has been achieved, it may be beneficial to change to the
ovoid arch form in the later stages of treatment.
The square arch form is useful to maintain expansion in upper arches after
rapid maxillary expansion.
180. 180
THE OVOID ARCH FORM:
Good stability.
Minimal amounts of post-treatment relapse.
181. 181The ovoid arch form has an inter-canine width close to that of the square form, and its
inter-molar width is similar to that of the tapered.
Byung-In Kim,,Mohamed Bayome, Yoonji Kim, Comparison of overjet among 3 arch types in normal occlusion, March 2011 Vol 139 Issue 3
American Journal of Orthodontics and Dentofacial Orthopedics
182. 182
SELECTION OF ARCHFORM:
Arch form template are placed on lower study models. The inter-canine width is
evaluated.
If buccal uprighting is needed in the lower arch, a wider arch form is selected.
183. 183ARCH WIRE SEQUENCING
EARLY IN TREATMENT: .015”/ .0175” multistranded /.014” SS or .016” HANT.
Less effect on arch form , so ovoid arch form indicated for all cases.
MID TREATMENT:
.014”/.016”/.018” SS or .019x.025” Rec. HANT.
Influence arch form requires full inventory.
LATE TREATMENT:
.019x.025”SS stocks of three arch forms.
184. MANAGEMENT OF ARCH FORMS
STANDARDIZED VS CUSTOMIZED ARCH FORM
Its not practical to customize wire for each patient
Multistrand .015” or round .016’’ HANT wires – U&L
As treatment progress heavier HANT wires & SS wires
Clear templates can be used to assess the patient's lower model, to determine whether
the lower arch has a tapered , square or ovoid arch form.
184
185. ARCH FORM CONTROL EARLY IN TREATMENT
Its recommended that all round wires be stocked in ovoid forms
Opening wires --- .014’’ multistranded, 0.016’’ HANT or sometimes 0.014’’ SS
Manufactured shape of rectangular HANT wires cannot be customized, therefore
stocked in ovoid, tapered & square forms
185
186. CUSTOMIZING SS RECTANGULAR WIRES
After rectangular HANT stage a wax template is molded over the lower arch to record the indentations
of the brackets
.019x.025’’ SS archwire is bent to the indentations in the wax
Wire then compared with starting lower model, to ensure that it closely resembles the overall starting
shape
Wire than checked for symmetry on a template
Finally, a Xerox copy of the wire is made & stored in the patient’s notes.
This is the patients IAF
Lower wires are used in IAF shape & upper in a form which is 3mm wider.
186
•Increased because they are being retracted in most treatment. •Less negative torque to offset the reciprocal effect of building more positive torque into the incisors
it is increased the resultant axial is esthetically and functionally undesirable
The 5° torque increase in torque improves •Ethetics by preventing flattened profile, straight upper lip and obtuse nasolabial angle.
•Provide more space for lower anterior teeth, thereby aiding classI intercuspation and
•Establish proper anterior guidance & prevent lateral stress in posterior segments
SWA 3
ROTH 8
MBT 10
SWA 7
ROTH 12
MBT 17
SWA -1
ROTH -1
This reduces the bulk of each bracket and allows reference lines in both the horizontal and the vertical planes, there by assisting accuracy of bracket placement.
The original standard metal SWA brackets were rectangular in shape, and the i.d. system was based on dots in the upper arch and dashes in the lower arch.
Brackets of a rhomboidal shape have reduced bulk and there is coordination of perspective lines through only two planes, which assists in accuracy of bracket placement.
.These wires are more flexible and hence show greater deflection and binding during space Closure with sliding mechanics.
The .019/.025 steel rectangular working wires are more rigid than .016/.022 or .017/.025 wires and perform better during space closure and overbite control
But generally there is some play between the bracket and arch wire even if the slot is filled with full dimension wire. * Because the dimension of the wire will be slightly smaller than the label dimension and slot width are larger than they are labeled
PLAY OF THE ARCH WIRE •Filling the bracket slot by incrementally increasing the wire cross section has been the basic sequence of therapeutic protocols. •Inevitably, a fraction of torque that is built into the bracket remains unexpressed owing to ‘play’ or ‘3rd order clearance’ or ‘slop’. •Inability in full expression of built in torque in PEA is perhaps one of its biggest shortcomings. The average ‘play’ values vary with different
s. Conversely, a distinct disadvantage may be encountered when filling the bracket slot. Full-sized stainless steel rectangular archwire becomes markedly reduced in springiness and range, thereby severely limiting the ability to place effective torque and finishing bends
They restrict canine crowns from tipping forward during leveling and aligning.
They are mainly used in premolar extraction cases, but they may also be required in some non-extraction cases where there is a local threat to anchorage.
If the opening wire is .015 multistrand, it may be turned into a small circle distal to the molar tube.
A/P anchorage control of lower molars - the lingual arch
Lower lingual arches may be used to prevent first molars drifting mesially into the available leeway space after shedding of the lower primary second molars. This averages 2.5mm.
Class III elastics can be worn in combination with a
headgear for maximum anchorage support in the lower anterior
segment.
Class III elastics can be worn to Kobayashi tie wires in the lower canine region, at the same time as a headgear. The authors prefer to delay Class III
elastics until the .016 round wire stage, to prevent extrusion of the incisors.
A/P anchorage support and control for upper molars - the use of headgear.
A/P anchorage support and control for upper molars - the palatal bar
The working steel .019/.025 rectangular wires normally have soldered hooks, and these are useful for many aspects of
treatment mechanics. The average hook positions are 36-38 mm in the upper arch and 26 mm in the lower arch. There is greater variability of hook position in the
upper arch, and this is assumed to be due to variation in upper lateral incisor size.
Conventional elastomeric modules.
'Easy-to-tie' elastomeric modules.
Coon ligature-tying pliers provide more positive archwire engagement than elastomeric modules.
Hemostats or 'mosquito' pliers may also be used to apply wire ligatures to" brackets.
Brackets with torque in base was designed so that the LA point, the base point, and the slot point were on the same horizontal plane. To accomplish this an acute (<90°) angle was required at the occlusal aspect of the bracket base, and an obtuse (>90°) angle at the gingival aspect of the bracket base
The CAD system analyzes the ideal slot location and then designs the in-fill of the bracket as necessary.
The outcome of the CAD process is that the resulting bracket can have torque in base, torque in face, or a combination of the tw0.
Approximately 20% of cases have upper second premolars with small clinical crowns, and a bracket which is 0.5mm thicker is helpful in obtaining good alignment of marginal ridges without wire bending for these cases.
The tip feature of preadjusted brackets is almost fully expressed. A .019/.025 wire in an upper canine bracket with 8 degree of built-in tip will express most of that tip. More than 7° of the 8° will be fully expressed. With light continuous force mechanics, tip can be well controlled, and tip specifications are fully and rapidly expressed in clinical use.
The research figures for tip were closely adhered to when the MBT™ bracket system was designed, although small changes were made to the tip specification for molar and
upper premolar attachments.
The tip feature of preadjusted brackets is almost fully expressed, and there is less than 1° of 'slop' when a .019 / .025 rectangular wire is placed.
Upper and lower molar attachments have 0" tip. When placed parallel to the buccal cusps of the molars, this delivers 5° of tip in the uppers and 2° of tip in the lowers.
As a result of the relative inefficiency of preadj listed
brackets in delivering torc|ue, it was necessary to build extra
torque into the incisor, molar, and lower premolar brackets,
in order to meet clinical goals with a minimum of wire
The upper canine bracket has -7° torque. When
inverted it has +7° torque.
The upper canine bracket with hook has 0° torque.
MBT™ Versatile+ bracket system has overall design improvements compared with previous appliances. These include changes in tip and torque, as well as design features
which introduce a new characteristic for the preadjusted system - that of versatility.
The firsl and second generation (p. 6) of brackets and buccal
tubes had a single option for each specific tooth, with a
recommendation for proper tip, torque and in-out
compensation. There was little room for versatility. The
MBT™ Versatile+ bracket system has overall design
improvements compared with previous appliances. These
include changes in tip and torque, as well as design features
which introduce a new characteristic for the preadjusted
system - that of versatility.
Theres a risk of moving the crown labially, while leaving the root
palataliy placed. In this situation, there will be a need for
additional wire bending, and treatment time will be extended.
During the alignment stage, il is necessary to create enough
space for the palataliy displaced tooth. This is achieved
using coil spring. The brackets on the adjacent teeth are
lied with wire ligatures, to prevent rotations
It is necessary to create sufficient space for palataliy
displaced incisors before attempting t o move them labially.
Bendbacks are placed 2 mm distal to molar tubes, to allow an
increase in arch length.
The palatally displaced lateral incisor is bracketed with the
normal bracket, but it is rotated 180° (Figs 2.37 & 2.38),
which changes the torque from +10° to -10°. This assists
in labial root torque at the rectangular wire stage. The tip
stays the same at 8°.
Conventional placement of an upper lateral incisor bracket gives +10° of torque.
Rotation of the lateral incisor bracket by 180° changes the torque from +10° t o -10°.
Many clinicians believe that the -7° upper and - 6 " lower
torque canine brackets are not ideal for premolar extraction
cases, or in cases where there is considerable canine tip to be
corrected during treatment.
This changes the torque to +7°, but the tip stays the same at 8". The left side bracket is placed on the left canine and the right side bracket is placed on the right canine. It is not correct to place the left canine bracket on the right canine or vice versa.
The inverted canine bracket is well adapted to the tooth surface, and the in-out dimension will be correct. At the rectangular wire stage, this helps to torque the canine root
into a palatal position with a minimum of wire bending
For the lower incisor brackets, 0" tip was used to reflect the research findings, and to make less demand on lower arch anchorage. An addilional benefit is that the 0" tip allows all the lower incisor brackets to be interchangeable, thereby assisting inventory control.
Similar comments can be made concerning the upper premolar brackets. The bracket system was designed with 0“ tip for all the upper premolars, to make less demand on
anchorage, and to assist in achieving a Class I relationship. The 0° tip allows them to be interchangeable, which helps inventory control.
Upper premolar brackets have zero tip, and are interchangeable both between first and second premolars and between the left and right sides.
The recommended specification for upper first and second molars is -14° torque, 0° tip, and 10° anti-rotation. The upper second molar tube may therefore be used on the upper first molars, for cases where headgear will not be required
When finishing cases in a Class II molar relationship, it can be helpful t o place lower second molar attachments on upper first and second molars of the contralateral side during the finishing stages. The lower attachments have 0° rotation, and normally in these cases it is appropriate to encourage upper molars to rotate mesio-palatally. A 0° rotation molar attachment is therefore preferable to the normal upper molar attachment, which has 10° rotation.
These were developed and tested in 2000, and are likely to find a place in the future of orthodontic treatment mechanics.
This radical development has been made possible by the flexibility of the .016 HANT wires, which can easily be threaded through lower second premolar tubes at the start of
treatment, even if there are slight rotations present.
Appliance breakages in the lower second premolar region
These have many advantages over the more bulky convertible lower first molar attachments, tubes are more comfortable, cleaner, and stronger than the conventional convertible brackets.
Their reduced bulk causes fewer interferences in this important area, and this in turn makes it easier to achieve accurate vertical bracket positioning.
For these reasons, lower first molar non-convertible tubes are becoming the attachment of choice in many practices, in preference to the more bulky convertible lower first molar attachments.
If lower incisors are bracketed at the start of treatment, they will inevitably procline a little during tooth alignment, especially in a non-extraction case.
Subsequent enamel reduction, followed by retroclination is a form of round tripping. This undesirable effect can be avoided by not bracketing lower
incisors at the outset.
Triangular-shaped incisors normally require reshaping to avoid unesthetic black triangles. It can be helpful to delay placement of brackets in the lower incisor region to reduce unwanted proclination early in treatment.
Treatment mechanics can be easier if lower incisors of a triangular shape are re-shaped before bracket placement.
Every' effort should be made to achieve accurate bracket positioning.
Ideal positioning can result in cases which show good occlusion with little effort, and will make the finishing stages of the treatment easier.
This helps efficiency in a busy orthodontic practice
Toward the end of the treatment, the teeth must be brought as close as possible to their final and functional positions before debonding. This necessitates a perfect alignment of the marginal ridges, contact points, and roots of the teeth. Factors such as error in bracket placement, tooth irregularities, and variations in tooth structure make it difficult to achieve these goals accurately with the preadjusted orthodontic appliance.
Slight mesial or distal adjustment is helpful when bracketing rotated incisors.
On a rotated tooth, the bracket can be bonded slightly more mesially or distally, sometimes with a very small amount of excess composite under the mesial or distal of the bracket base.
In this way, full correction of the rotation can be achieved with no special measures.
The bracket-positioning gauges are used in slightly different ways in different areas of the mouth.
In the incisor regions, the gauge is placed at 90° to the labial surface.
In the canine and premolar regions, the gauge is placed parallel with the occlusal plane.
In the molar region, the gauge is placed parallel with the occlusal surface of each individual molar
This is the most difficult aspect of bracket positioning, and accuracy is greatly improved by the use of gauges and an individualized bracket-positioning chart.
This will deal with difficulties such as tooth length discrepancies, labially and lingually displaced roots, partly erupted teeth, and gingival hyperplasia which have been
previously reported.
Me incial idge
RELAPSE TENDENCY AFTER ORTHODONTIC TREATMENT 1. In 1969, Reidel reviewed literature concerning stability of arch form; - When intercanine and inter molar width had been changed during orthodontic treament, there was a strong tendency for these teeth to return to their pre treatment positions - Thus he postulated that arch form particularly in the mandibular arch cannot be permanently altered during appliance therapy (
PR=C
PRESSURE
RADIUS OF CURVATURE
C CONSTANT
Cases undergoing single arch treatment often require the use of the tapered arch form. In this way, no expansion of the treated arch occurs, relative to the untreated arch.
The posterior part of this arch form can easily be modified to match the inter-molar width of the patient.
: class II div 2
The recent research (above) indicates that a greater number of tapered arch forms should also be used. When superimposed,
the three shapes vary mainly in inter-canine and inler-first premolar width, giving a range of approximately 6 mm in this area.
Rectangular SS .019x.025 working wires have a major influence on arch form. Therefore need to be customized to each patient’s individual arch form (IAF)
