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ARCHWIRE VIBRATIONS AND
STICK SLIP BEHAVIOR AT
BRACKET ARCHWIRE
INTERFACEJOURNAL CLUB
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AIM OF THE STUDY
To obtain in-vivo measurements of vibrational frequencies and amplitudes
associated with oral disturbances on orthodontic appliances and thenreplicate these ex vivo to evaluate the stick-slip behavior at bracket-archwire
interfaces by using clinically relevant tipping moments during passive and
active bracket ligation. In addition, predictive statistical modeling was applied
to the exvivo data to explore a broader range of frequencies and amplitudes
of vibration and compare potential effects between the 2 types of bracket
ligation.
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REVIEW OF LITERATURE
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FORCES RELEASED DURING SLIDING
MECHANICS
WITH PASSIVE SELF-LIGATING BRACKETS
ORNONCONVENTIONAL ELASTOMERIC
LIGATURES
LORENZO FRANCHI ET AL
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This study was performed in Florence and Rome, Italy
4 types of passive SLB was compared to CEL and NCEL
5 brackets of each type was aligned using 0.0215 0.028-in stainless steel wirewas used to align the brackets before fixing them with cyanoacrylate glue onto
an acrylic block. The interbracket distance was set at 8.5 mm
Sliding friction generated by the 0.019 0.025-in stainless steel wire wasmeasured under dry conditions and at room temperature (20C 2C)
Result: Significantly smaller static and kinetic forces were generated by the
SLBs and NCEL (2 g) compared with the CEL (500 g). No significant differenceswere found within the different types of SLBs, or between these and the NCEL
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INFLUENCE OF ANGULATION ON THE
RESISTANCE TO SLIDING IN FIXED
APPLIANCES
LAURENCE C. ARTICOLO AND ROBERT P. KUSY
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Study was performed in Chapel Hill, North Carolina
The resistances to sliding of 21 25 mil stainless steel, nickel titanium, or beta-titanium arch wires ligated to brackets made of stainless steel, single crystal
sapphire, or polycrystalline alumina with 10 mil stainless steel ligatures werestudied as a function of five angulations (0, 3, 7, 11, and 13) using ninedifferent couples .
After 22 mil brackets were mounted to fixtures and, the arch wires were slidthrough the brackets at 1 cm/minute in the dry state at 34C.
The resistance to sliding was measured by one computer while five normalforces (nominally 0.2, 0.4, 0.6, 0.8, and 1.0 kg) were serially maintained byanother computer
When couples were in the passive configuration at low angulations, allstainless steel wire-bracket couples once again had the least resistance tosliding.
When the angulation exceeded about 3, however, the active configurationemerged and binding quickly dominated as the resistance to sliding increasedover 100-fold. Under these conditions, the relative rankings among thematerials transposed; couples of stainless steel had the most resistance tosliding, whereas, couples of the more compliant alloys, such as nickel titaniumwire, had the least.
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COMPARATIVE EVALUATION OFFRICTIONAL FORCES IN ACTIVE AND
PASSIVE SELF-LIGATING BRACKETS WITH
VARIOUS ARCHWIRE ALLOYS
MANU KRISHNAN ET AL
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This in-vitro study compared the effects of stainless steel, nickel-titanium, and
beta-titanium archwires on frictional forces of passive and active self-ligating
brackets with a conventional bracket
Static and kinetic frictional forces were lower for both the passive and active
designs than for the conventional brackets. Maximum values were seen with
the beta-titanium archwires, and significant differences were observed
between nickel titanium and stainless steel archwires. With the passive or
active self-ligating brackets, stainless steel wire did not produce a significant
difference, but differences were significant with nickel-titanium and beta-
titanium wires.
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COMPARISON OF RESISTANCE TO
SLIDING BETWEEN DIFFERENT SELF-LIGATING BRACKETS WITH SECOND
ORDER ANGULATION IN THE DRY AND
SALIVA STATES
GLENYS A. THORSTENSON AND ROBERT P. KUSY
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Resistance to sliding was investigated for 3 self-ligating brackets having passive
slides and 3 self-ligating brackets having active clips. For all cases, an 0.018
0.025-in stainless steel archwire was drawn through each bracket at a rate of10 mm/min over a distance of 2.5 mm. For each bracket, the resistances to
sliding were measured at 14 second-order angulations, which ranged from 9
to 9. Both the dry and the wet (human saliva) states were evaluated at 34C.
From dimensional measurements, the critical contact angles for binding were
determined for all products and ranged from 3 to 5.
Below each characteristic critical angle, brackets with passive slides exhibited
negligible friction; brackets with active clips exhibited frictional forces as great
as 50 cN (50 g). Above each critical angle, all brackets had elastic binding
forces that increased at similar rates as angulation increased and were
independent of bracket design. Generally speaking, at second-order
angulations that exceeded the critical angle, brackets with active clips that hada low critical angle had more resistance to sliding than did brackets with active
clips that had a higher critical angle. Brackets with passive slides that had a
high critical angle exhibited the lowest resistance to sliding, but could do so at
a cost of some loss of control.
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FRICTION AND RESISTANCE TO
SLIDING IN ORTHODONTICS: A
CRITICAL REVIEW
S. JACK BURROW
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Frictional resistance was effectively reduced to zero each time minute relative
movements occurred at the bracket/ wire interfaces because binding and
notching were temporarily released
Oscillating the bracket while measuring the resistance to sliding, produces the
same temporary release of binding
If one considers the clinical situation, where there is intermittent movement
between the bracket and archwire, then clinically one may not be looking at
true friction, but rather a binding and releasing phenomenon
Hixon et al observed that vibrating the teeth decreased resistance to sliding,
providing supporting evidence of movement as binding and releasing.
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TAKING THE CHATTER OUT OF SLIDING
MECHANICS - ADDRESSING THE
VIBRATION ISSUE
ROBERT P. KUSY
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Although vibration might help an archwire jump out of a notched wire region
that has occurred because of excessive angulation (or torquing) or because of
inadequate yield strength (or hardness), vibration normally represents just a
lot of undeterminable wind that probably blows east as often as it does west,or north, or south. The practitioner and his or her sliding mechanics
determine the prevailing course. So, let us maintain our bearings in
understanding the principles of sliding mechanics without being too distracted
by the chatter from indefinable vibrations.
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MATERIALSAND
METHODS
6 volunteers
The subjects were at least 18 years of age,
had maxillary right canines, and were
undergoing orthodontic treatment with
fixed appliances on their maxillary andmandibular anterior and posterior teeth
Single axis peizoresistive accelerometer
Digital storage oscilloscope
In-vivo
The mean vibration frequency was 98 ( 41) Hz with a range
of 58 to 139 Hz
The mean peak-to-peak vibration amplitude was 151 ( 39)
mV with a range of 112 to 190 mV
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MATERIALSAND
METHODS
A waveform generator
0.017 3 0.025-in stainless steel archwire
Two types of stainless steel brackets with 0.022 3
0.028-in slot dimensions for the maxillary right canine
DamonQ, 491- 6480; Ormco, Orange, Calif had amesiodistal width of 2.9 mm and characteristics of
passive ligation by closing a door and creating atube to constrain the archwire.
Unitek Victory Series, 017-880; 3M Unitek,Monrovia, Calif had a mesiodistal width of 3.4 mm,conventional twin design, and characteristics ofactive ligation by using an elastomeric ligature
Each bracket had bonded (Transbond XT; 3M Unitek)
to its mesh pad a moment arm that was a 0.032-indiameter stainless steel wire (Dentsply GACInternational) that extended superiorly with a notch10 mm above the center of the bracket slot. Thismoment arm was perpendicular to the gingival andincisal wall of the bracket slot and parallel to thepulpal wall of the bracket slot.
Ex-vivo
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MATERIALS AND METHODS
Spring was activated 12mm
Moment per mm deactivation of spring = 1460 cN
Data and statistical analyses used backward linear regression to determine
which, if any, independent variables had no significant effect on the
dependent variable, bracket-archwire frictional resistance
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RESULTS
The bench-top stick-slip measurement trials containing medium (150 mV) and high(190 mV) amplitude vibrations had significantly less friction (ln, s), 4.81 2.08 and4.67 2.00, respectively, than those subjected to low (110 mV) amplitudes, 5.80 1.39 (P = 0.04). There were no significant differences between passive and activeligation methods.
Analyses determined critical frequencies and amplitudes of vibration for thehighest values of predicted frictional resistance, which were 122 Hz (2.99) and 111mV (1.00) for the passive bracket ligation type and 120 Hz (2.27) and 100 mV (1.51)for the active bracket ligation type.
The lowest predicted frictional resistance for the range of frequencies andamplitudes investigated was for the passive bracket ligation type at 58 Hz and 202mV. In contrast, the lowest frictional resistance predicted for the active bracketligation type was at 150 Hz and 205 mV and was 5-fold higher
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0
1
2
3
4
5
6
110 150 190
5.64
4.47 4.21
5.97
5.14 5.14
MEANFRICTIONALRESISTANCE
AMPLITUDE
110 150 190
PASSIVE 5.64 4.47 4.21
ACTIVE 5.97 5.14 5.14
PASSIVE ACTIVE
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0
1
2
3
4
5
6
60 100 140
3.28
4.34 4.44.425.06 4.84
MEANFRICTIONA
LRESISTANCE
FREQUENCY
60 100 140
PASSIVE 3.28 4.34 4.4
ACTIVE 4.42 5.06 4.84
PASSIVE ACTIVE
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DISCUSSION
LIMITATIONS OF THE STUDY
BIOLOGIC FACTORS NOT CONSIDERED
DID NOT TAKE INTO ACCOUNTRHEOPHYSICS OF SALIVA, FOOD &BEVERAGES
TEMPERATURE CHANGES
CHANGES OF PHYSICAL PROPERTIES OFWIRE, ELASTOMERIC LIGATION
THE MASS OF THE ACCELEROMETERMIGHT HAVE AFFECTED ARCHWIREVIBRATION
EFFECTS OF INTERBRACKET DISTANCE ANDADJACENT TOOTH CONSTRAINTCONDITIONS WERE NOT INCLUDED
REAL-TIME RECORDING OF TRACTIONALFORCES
BROADER RANGE OF BRACKET SLOT AND
ARCHWIRE DIMENSIONS TO BE TESTED
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CONCLUSION
Further studies including all variables concerned needs to be performed for
clinically applicability
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THANK YOU