Effects of sterilization on tensile strength of orthodontic wires /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


The Effects of Sterilization on
Tensile Strength of Orthodontic
wires

Presented by:
Madhvi Bhardwaj
Postgraduate student

Guided by:
Dr.(Mrs.) P.V.Hazarey
Prof. And Head

Sharad Pawar Dental College
Datta Meghe Institute of Medical Sciences, Wardha

Introduction
• As overhead costs rise, orthodontists are
continually searching for ways to reduce costs.
• The newer orthodontic wires display an excellent
combination of strength resiliency and low-load
deflection rates.
• Beta-titanium (TMA) three times while NiTi
usually two times more expensive than stainless
steel wires.

• It is unlikely that orthodontist will discontinue their
use due to their relatively high price.
• Hence, the challenge is to make more cost effective
use of these wires.
• Sterilization and reuse of the more expensive
orthodontic wires is one option.


• During finishing stage of treatment when
lower grade wires may be reused in the same
patient
• Also one can recycle and reuse the same wire
in different patient


• When considering the reuse of orthodontic
wires, it is important to:
– Evaluate the effect of sterilization on the
physical properties of wires
– Eliminate the risk of cross infection


AIM AND OBJECTIVES
•

To evaluate the effects of sterilization on the tensile
strength of Nickel- Titanium, TMA and Stainless
steel wires.

•

To compare the effects of three different methods of
sterilization methods on the tensile strength of
Nickel- Titanium, TMA and Stainless steel wires.


Materials
•

Wires used:

•

5 samples of each
–

0.016” (round) and 0.016”X0.022” (rectangular)
TMA (Ortho organizer)

–

Nickel – Titanium (Libral Traders)

–

Stainless Steel wires (Libral Traders)

• Control group: The used wires were
ultrasonically cleaned and air dried
but was not processed through
different sterilization procedures.


• Experimental group: The used wires
were ultrasonically cleaned and air
dried and was processed through
different sterilization procedures.


•

Equipments used for sterilizations:

HOT AIR OVEN

STEAM AUTOCLAVE

BIOCLENZ SOLUTION
(2% GLUTERALDEHYDE)

• Universal testing machine:
– For measuring the ultimate tensile strengths of the
wires


Method
• Part 1:
– The different types of sterilization methods used
on three types of wires:
• Dry heat sterilization: Hot air oven was used at
320°to 340°F (160° to 171°C) for a period of 1 to 2
hours.
• Autoclaving: Used at 250 °F (121 °C) at 15 psi for
15 minutes or 270 °F (132 °C) at 30 psi.
• Cold sterilization: 2% Glutaraldehyde was used for
a duration of 10 minutes and upto 10 hours of time.

• Part 2 :
– Determining the effects of repeated sterilization
on tensile strengths of 0.016 ” and 0.016”X
0.022” TMA, Nickel -Titanium and Stainless
steel wires.

• All wires were tested using a Universal Tensile
Testing Machine (Model No. 1.3 D) with a load
cell capacity of 2500 N having a least count of
50 N.

• The machine consisted of two movable fixtures so
as to tightly grip the wire specimen in place when
the test is being performed and the speed of the
machine was kept at a constant rate of 1mm/min.


Observation and Results
Table 1 Ultimate Tensile strength of stainless steel wire(0.016
round)
Sterilization Method
Sterilization cycles

Dry heat

Autoclave

Cold

0

1237 ± 85

1211 ± 85

1087 ± 48

1

1282 ± 57

1251 ± 84

1091 ± 38

5

1212 ± 95

1238 ± 180

1088 ± 47

8.06

F- value*
p-level
Comparison
Between
Cycles

2.95

2.01

NS

NS

NS

(0-1)

NS

---

---

(0-5)

NS

---

---

NS
--(1-5)

---

Table 2 : Ultimate Tensile strength of stainless steel
wire (0.016 x 0.022inch)

Dry heat

Autoclave

0
1

1855.33 ± 26.39
1825.44 ± 30.97

5

1849.71 ± 20.42

1840.27 ± 5.53
1832.12 ± 5.40
1835.32 ±
19.15
0.59
0.56
NS,p>0.05
0.54
NS, p>0.05
0.79
NS, p>0.05
0.90
NS, p>0.05

F- value*
p-level
Comparison
Between
Cycles

(0-1)
(0-5)
(1-5)

1.82
0.20
NS,p>0.05
0.21
NS, p>0.05
0.93
NS,p>0.05
0.34
NS,p>0.05


Cold
1797.29 ± 17.36
1794.75 ± 19.82
1776.80 ± 19.62
1.73
0.21
NS,p>0.05
0.97
NS, p>0.05
0.24
NS, p>0.05
0.32
NS, p>0.05

• Dry heat sterilization, Autoclaving and
Cold sterilization did not affect the
tensile strength of round and rectangular
Stainless steel wires.


Table 3 Ultimate Tensile strength of Nickel Titanium wire ( 0.016 round)


Dry heat

Autoclave

Cold

0

1226 ± 11

1226 ± 11

1226 ± 11

1

1382 ± 60

1366 ± 54

1222 ± 15

5

1364 ± 31

1382 ± 29

1234 ± 14

32.2
S,p<.01

28.6
S,p<.01

(0-1)

P<.01

P<.01

---

(0-5)

P<.01

P<.01

---

(1-5)

NS

NS

---

F- value*
p-level
Comparison
Between
Cycles


1.06
NS

Table 4 : Ultimate Tensile strength of Nickel
Titanium( 0.016 x 0.022 inch)

0
1
5
F- value*
p-level
Comparison
Between
Cycles

(0-1)
(0-5)
(1-5)

Dry heat

Autoclave

1748.92 ± 20.64
1836.36 ± 21.68
1758.79 ± 17.02
28.99
0.00
S,p<0.05
0.00
S, p<0.05
0.71
NS,p>0.05
0.00
S,p<0.05

1746.45 ± 23.42
1826.71 ± 21.47
1844.98 ± 21.68
27.83
0. 00
S,p<0.05
0.00
S, p<0.05
0.00
S, p<0.05
0.42
NS, p>0.05


Cold
1748.92 ± 20.64
1768.31 ± 0.27
1748.26 ± 1.75
4.53
0.30
NS
0.06
NS, p>0.05
0.99
NS, p>0.05
0.05
NS, p>0.05

• Dry heat sterilization significantly increased the
tensile strength of both round and rectangular Nickel
-Titanium wires after one cycle.
• Autoclaving increased the tensile strength of
rectangular and round Nickel -Titanium wires.
• Cold sterilization did not affect the tensile strength of
both round and rectangular Nickel -Titanium wires.


Table 5 Ultimate Tensile strength of TMA wire (0.016 round)


Dry heat

Autoclave

Cold

0

1087 ± 48

1087 ± 48

1087 ± 48

1

1282 ± 57

1251 ± 84

1091 ± 38

5

1212 ± 95

1238 ± 180

1088 ± 47

2.95

8.06
S,0.01

F- value*
p-level
Comparison
Between
Cycles

0.01

S,0.02

NS,0.2

(0-1)

S

---

---

(0-5)

S

S

---

(1-5)

NS

NS

---


Table 6 : Ultimate Tensile strength of TMA (0.016 x
0.022 inch)

0
1
5
F- value*
p-level
Comparison
Between
Cycles

(0-1)
(0-5)
(1-5)

Dry heat
1673.53 ± 20.64
1840.89 ± 22.70
1672.03 ± 33.65
68.12
0.00
S,p<0.05
0.00
S, p<0.05
0.90
NS,p>0.05
0.00
S,p<0.05

Autoclave

Cold

1866.02 ± 16.83 1773.53 ± 20.64
1823.73 ± 21.26 1766.03 ± 4.87
1878.45 ± 21.89 1792.68 ± 22.11
10.15
3.01
0.003
0.08
S,p<0.05
NS,p>0.05
0.01
0.78
S, p<0.05
NS, p>0.05
0.60
0.24
NS, p>0.05
NS, p>0.05
0.003
0.08
S, p<0.05
NS, p>0.05


• Dry heat sterilization significantly increased the
tensile strength of both round and rectangular
Beta-Titanium wires after one cycle.
• Autoclaving also increased the tensile strength of
in case of round and rectangular Beta-Titanium
wires
• Cold sterilization did not affect the tensile
strength of both round and rectangular BetaTitanium wires.

Statistical analysis showed that with the
comparison between the cycles no significant
differences were found in the tensile strength of
wires between zero cycle and five cycles of
sterilization but increases after one cycle of
sterilization.


Discussion
• The purpose of present study was to
examine the effect of repeated cycles
of different methods of sterilizations
on tensile strength of round and
rectangular (0.016” and 0.016”X
0.022” ) Beta – Titanium, Nickel –
Titanium, and Stainless steel wires.

• Tensile strength was chosen as the parameters
as it has a direct impact on the clinical use of
wire.
• If a wire’s tensile strength decreases it is more
prone to breakage, which may cause a problem
for both the patient and the orthodontist


• It can be concluded that sterilization of Beta –
Titanium and Nickel – Titanium wires with dry
heat or autoclave produces an increase in their
tensile strength.
• The decrease in tensile strength of stainless
steel wires produced by autoclave or dry heat
sterilization may not present a clinical problem
since only few Orthodontists reuse these wires.


Conclusion
• Whether or not recycling is a practical method of
reducing orthodontic overhead cost
• The results of this study suggest that Orthodontists
who choose to recycled Nickel – Titanium, TMA or
Stainless steel arch wires do not need to be
concerned about reducing the wire’s ultimate tensile
strength by sterilization procedures.
• Instead, tensile strength increases in case of NickelTitanium and TMA wires


Effects of sterilization on tensile strength of orthodontic wires /certified fixed orthodontic courses by Indian dental academy

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